Review of Multifunctional Inverter Topologies and Control Schemes Used in Distributed Generation Systems
Review of Multifunctional Inverter Topologies and Control Schemes Used in Distributed Generation Systems
Journal of Power Electronics. 2014. Mar, 14(2): 324-340
Copyright © 2014, The Korean Institute Of Power Electronics
  • Received : October 29, 2013
  • Accepted : December 30, 2013
  • Published : March 30, 2014
Export by style
Cited by
About the Authors
Ahmet Teke
Department of Electrical and Electronics Eng., Cukurova University, Adana, Turkey
Mohammad Barghi Latran
Department of Electrical and Electronics Eng., Cukurova University, Adana, Turkey

Recent developments in power electronics technology have spurred interest in the use of renewable energy sources as distributed generation (DG) generators. The key component in DG generators is a grid-connected inverter that serves as an effective interface between the renewable energy source and the utility grid. The multifunctional inverter (MFI) is special type of grid-connected inverter that has elicited much attention in recent years. MFIs not only generate power for DGs but also provide increased functionality through improved power quality and voltage and reactive power support; thus, the capability of the auxiliary service for the utility grid is improved. This paper presents a comprehensive review of the various MFI system configurations for single-phase (two-wire) and three-phase (three- or four-wire) systems and control strategies for the compensation of different power quality problems. The advances in practical applications and recent research on MFIs are presented through a review of nearly 200 papers.
In recent years, the installation of more distributed generators (DG) in power distribution networks has elicited increased attention. A number of reasons can explain this trend. Such reasons include environmental concerns, electricity business restructuring, and the rapid development of small-scale power generation technologies and other micro-grid related devices and systems. In practice, DG units can be constructed with various renewable energy sources (RES). However, the real power output from these energy resources is essentially unstable. Given the increasing number of RESs and DG installations, new control strategies must be developed for the proper operation and management of new power grids embedded with DG units to maintain or improve system quality and reliability. Power electronics and smart technologies play an important role in DG operations, in which the effective integration of RES into the power grid is the major objective [1] - [6] .
A comprehensive review of AC and DC micro-grid systems with RES-based DG units, energy storage devices, and loads available in recent literature was presented in [2] . A fuel cell system-based power generation system was presented in [7] - [9] . Several typical PV-based DG systems were designed in [10] and [11] , and a DG system based on a wind power generator was presented in [12] . Utility is of concern because of the high penetration level of intermittent RES in distribution systems. This situation may cause a hazard to the network in terms of power quality (PQ), voltage regulation, and stability. The electric PQ guidelines and standard limits can be found in [13] - [19] . The negative effects of poor PQ were well investigated in [13] , [14] , and [17] - [19] .
The relation between DG and PQ is ambiguous. Many authors have stressed the positive effects of DG on PQ problems. In [20] , the sources of PQ problems in DG systems were analyzed; this study has contributed significantly to this new research field. In [21] , [22] , the resonance phenomenon in a PV plant was discussed to define the unwanted trip off of grid-tied inverters, a phenomenon that shows the significance and necessity significance of PQ enhancement in DG systems. In the field of exhaustive PQ evaluation, [23] presented several useful suggestions to form a quantitative exhaustive indicator, including various PQ indicators. Exhaustive evaluation can provide a decision on the existing PQ, which may be used as a reference for DG systems to manage their PQ. Therefore, DG systems must comply with technical and regulatory requirements to maintain the efficient, reliable and safe operation of the overall grid. DG systems can be controlled efficiently to improve the system operation with enhanced PQ at the point of common coupling (PCC) with the advances in power electronics and digital control technologies [24] . Although the main purpose of DG systems is to provide active power, reactive power can be compensated and active power filter functionality can be achieved.
DG systems are tied to the utility grid either in series or in a shunt position. However, the target compensated quantities, such as harmonics, unbalance, and reactive power, are directly related to the currents. As such, the shunt type topology is widely utilized because it effectively injects compensating currents at PCC. In practical applications, the three-phase voltage source inverter (VSI) is widely used as the interface between RES-based DG generators and the utility grid. To develop a multifunctional DG inverter, the switching signals for VSI, which are by nature current signals, may include information on the active power supplied from RES and the reactive power required to compensate for the PQ disturbances at PCC [25] , [26] . The general components of a common MFI system and their interconnections are shown in Fig. 1 .
PPT Slide
Lager Image
Generalized block diagram of MFI.
Measuring instruments, such as advanced metering infrastructures and demand energy management and protection systems, can also be integrated into MFIs. To achieve all these enhancements, current research is focused on determining details of utility grid applications, such as power supply for critical loads in commercial buildings, electronic factories, and hospitals. Results show a significant reduction in PQ problems, losses, and downtime and protection malfunctions [2] , [27] - [29] .
The present study also developed an abbreviated list of different MFI categories. A total of 10 abbreviations were identified: MFI-ML, MFI-VM, MFI-CM, MFI-ZM, MFI-DC, MFI-FC, MFI-CH, MFI-HM, MFI-MM, and MFI-DM. The most substantial control methods and approaches utilized to control MFIs are likewise presented in this paper.
MFIs can be classified into two major categories: power circuit structure of the MFI and compensated variable in PCC.
- A. Power Circuit Structure
MFIs can be classified based on the power circuit structure utilized to solve PQ problems in a studied system as shown in Fig. 2 . The important parameters ascribed to these classifications are the following: (1) type of power source, (2) inverter topology, and (3) power circuit configuration of the MFI. Newly developed topologies and/or power circuit configurations for MFIs are also presented in this section [26] .
PPT Slide
Lager Image
Classification of MFI based on power circuit structure.
1) Classification according to the type of power source: AC loads or devices in the power system can be generally divided into single-phase and three-phase depending on whether the system is supplied by a single-phase (2-wire) or three-phase (3-wire or 4-wire) source. Various MFI configurations are employed to mitigate PQ disturbances from the system. The voltage-related PQ disturbances that occur in both single-phase and three-phase systems have similar characteristics. Additionally, three-phase systems require voltage unbalance compensation to satisfy the enhanced PQ.
The major issue in a single-phase system is the compensation for the reactive power and harmonic currents. In the case of a three-phase three-wire (3P3W) system, one must consider the current unbalance expected from the reactive current and current harmonics. A neutral current compensation loop is required for a three-phase four-wire (3P4W) system.
The most popular MFI system configuration that compensates for PQ disturbances in a single-phase two-wire (1P2W) supply system consists of two H-bridge inverters (total of four semiconductor switches) as shown in Fig. 3 (a) [30] - [49] . Fig. 3 (b) shows a single-phase three-wire (1P3W) half-bridge VSI topology that generates stable sinusoidal voltages or achieves PQ compensation [50] . In [51] , a new active filtering technique was proposed as the interface between single-phase VSI and the utility grid. The technique involves the use of a single inverter with four legs (1P4L) as shown in Fig. 3 (c). Two legs are utilized to construct a full bridge characterized by low switching frequency. The two other legs comprise a filter full bridge characterized by low power and high switching frequency.
PPT Slide
Lager Image
(a) Configuration of 1P2W MFI H-bridge. (b) Configuration of 1P3W MFI. (c) Configuration of 1P4L MFI.
Nonlinear loads, such as variable speed drives fed from a 3P3W system, AC-AC converters, arc welding devices, and arc furnaces, cause several PQ problems. A 3P3W VSI-based MFI is shown in Fig. 4 . It is the most preferred MFI system [52] - [127] . Fig. 5 shows the circuit topology of a three-phase, two-leg, three-wire inverter that generates active power in the utility system to simultaneously achieve harmonic and reactive power compensation [128] , [129] . Except for three-phase loads, some industrial facilities often consist of combined loads, such as a variety of single-phase and three-phase loads supplied by a 3P4W source.
PPT Slide
Lager Image
Configuration of the 3P3W VSI-based MFI.
PPT Slide
Lager Image
Configuration of a 3P2L MFI.
A neutral conductor causes an excessive neutral current flow and thus demands additional compensation requirements in the presence of a fourth wire. To mitigate the neutral current in a 3P4W system, various shunt inverter configurations have been studied, namely, two-split capacitor (2C) [130] , [131] , four-leg capacitor (4L) [131] - [141] , and three-H bridge (3HB).
Fig. 6 shows the 3P4W MFI configurations based on 2C, 4L, and 3HB topologies. The 2C topology consists of two split capacitors on the DC side. The midpoint of the capacitor is employed as a connection point for the fourth wire. In the 2C topology, equal voltages must be maintained in both capacitors to prevent the flow of circulating current as shown in Fig. 6 (a). An additional control loop for DC bus capacitor voltage regulation is required for this type of topology.
PPT Slide
Lager Image
Inverter topology of 3P4W MFI; (a) 2C shunt inverter topology; (b) 4L inverter topology; and (c) 3HB inverter topology.
An additional leg (two switching devices) is employed in the 4L topology to compensate for the load neutral current as shown in Fig. 6 (b). The 4L topology achieves superior control over neutral current through the use of a fourth leg. The 3HB topology involves the use of three units of single-phase H-bridge inverters connected to the common DC bus of the MFI. The MFI system configuration, in which the shunt inverter consists of three units of H-bridges, is shown in Fig. 6 (c).
2) Classification according to inverter topology: In an MFI, both the inverter and rectifier use the common DC bus. The inverter maintains the DC link value at its set reference value. An MFI can be formed with a pulse-width modulated (PWM) current source inverter (CSI) [93] , [100] - [103] , which employs a common inductor L DC to develop the DC bus. Fig. 7 shows the configuration of a CSI-based MFI system. The CSI-based MFI topology is rarely used because of its high cost and losses.
PPT Slide
Lager Image
Configuration of the CSI-based MFI.
The second topology, the most popular and common inverter topology for MFI, is PWM VSI. This topology involves the use of a common capacitor C DC . Fig. 8 shows the single-line configuration of a VSI-based MFI. Most studies on MFIs generally use the VSI-based topology. The VSI topology does not require blocking diodes; it is lighter in weight, cheaper, and allows for more flexible control than the CSI topology.
PPT Slide
Lager Image
Configuration of the VSI-based MFI.
The third topology for MFI consists of a Z-source inverter (ZSI) that shares a common energy storage capacitor and an inductor. ZSI is different in structure from the conventional VSI or CSI because of the presence of X-shaped LC impedance shown in Fig. 9 . ZSI allows for safe triggering through the inverter arms and the amplification of voltage across the Z-source capacitor through the inductors in the Z-source impedance network. With the rapid development in renewable energy technologies, ZSI topology provides DG operators greater flexibility in interfacing the generated energy to the utility grid [143] - [145] . In [146] , a new topology called quasi-ZSI (qZSI) was proposed to generate power from a PV system with a battery. The battery is shunt, with one of the capacitors in quasi-Z-source (qZS) topology instead of a DC/DC converter. The system with battery support can improve the injected power in the utility grid when the PV power fluctuates as shown in Fig. 10 .
PPT Slide
Lager Image
Configuration of the ZSI-based MFI.
PPT Slide
Lager Image
Configuration of the qZSI-based MFI.
T-source inverter is a modified shape of ZSI, in which the number of passive components is reduced to further improve the ZSI’s operation as studied in [108] . The configuration of the T-source inverter is shown in Fig. 11 .
PPT Slide
Lager Image
Configuration of a TSI-based MFI.
In [147] , the three-phase five-leg topology (DC link is omitted; shown in Fig. 12 ) and its overall control are investigated. The performance of the systems is compared with that of the traditional six-leg topology. A five-leg converter is used to replace the traditional six-leg one while performing similar tasks. The structure and control of wind energy conversion systems (WECS) with an induction generator doubly fed by a five-leg converter are different from the traditional scheme with a six-leg converter. The number of output control signals can be reduced because the number of legs is reduced. Therefore, a modified PWM controller for a five-leg converter is preferred. The voltage reference generation units remain identical in both five- and six-leg cases. Thus, the generation of the desired two sets of three-phase voltages in the utility grid and rotor sides is possible with a suitable PWM control method.
PPT Slide
Lager Image
Configuration of the five-leg converter.
Single-phase and three-phase VSIs coupled with isolating transformers are often preferred to ensure galvanic isolation and alter the output voltage value [129] , [149] - [152] . In [153] , a linear model in the stationary frame was developed for a VSI connected to the utility grid through Δ-Y and Y-Y transformers. The proposed model accounts for the phase shift caused by the Δ-Y transformer. This phase shift improves the system’s dynamic and steady-state behavior in balanced and unbalanced conditions. According to the modal analysis performed in [153] , the phase shift from the Δ-Y configuration can decrease the gain of the open-loop system by 62% compared with the Y-Y configuration-based system.
3) Classification according to power circuit configuration: This section presents a review of various MFI configurations.
a) Multilevel MFI (MFI-ML): In medium-voltage and high-power applications, multilevel inverter technology is a very efficient alternative in the interfacing system for the integration of RES into the AC grid and also for other applications where high-quality voltages and currents are required. Superior harmonic spectrum, decreased voltage rating for the switches, decreased common mode voltages, and minimal voltage changes (dv/dt) are important advantages of multilevel inverters. However, the complexity of the control method is higher compared with that in the traditional two-level inverter. Basically, multilevel MFI can be classified into (1) voltage-source multilevel MFI, (2) current-source multilevel MFI, and (3) Z-source multilevel MFI.
Voltage-Source Multilevel MFI (MFI-VM): In this section, the classification of voltage-source multilevel MFI (referred to as MFI-VM in this study) is discussed.
Diode-Clamped MFI (MFI-DC): The circuit scheme of a three-phase, three-level, diode-clamped inverter is provided in Fig. 13 . This scheme is utilized to integrate DG to the utility grid to improve PQ at PCC [86] , [154] , [155] . Each phase of the three-phase inverter employs a common DC bus subdivided into three levels by two capacitors. The voltage in each capacitor is V dc /2 and the voltage stress on each switch is restricted to V dc /2 through the clamping diodes. Fig. 14 shows the three-level neutral point clamped (NPC) inverter topology [156] - [165] . Each of the three legs can provide one additional output voltage level. The neutral point voltage that corresponds to one half of the DC link voltage is available at the output of the phases when appropriate diodes are clamped. Moreover, five-level NPC is used to connect DG to the AC grid [166] .
PPT Slide
Lager Image
Configuration of the three-level MFI-DC system.
PPT Slide
Lager Image
Configuration of the three-level MFI-NC system.
Flying Capacitor MFI (MFI-FC): The three-phase, three-level, flying capacitor inverter topology is used to integrate DG to the utility grid as shown in Fig. 15 [165] . Each phase leg of the inverter has a configuration identical to that of common DC series capacitors. The inner-loop capacitors are independent in the A, B, and C phase legs. The flying capacitor multilevel inverter has the advantages of flexible switching control, high protection capability for power switches, and control of real and reactive power. The inverter requires various switching combinations to balance the voltage across the capacitor. This condition implies an increase in the complexity of the control algorithm.
PPT Slide
Lager Image
Configuration of the three-level MFI-FC system.
Cascade H-Bridge MFI (MFI-CH): MFI-CH consists of multiple H-bridge inverters in cascade arrangement as shown in Fig. 16 . The cascade topology permits the use of DC sources with various voltage levels. High-quality and high-resolution multilevel waveforms can be obtained with a small number of components. Although the cascaded topology requires multiple isolated DC sources, the batteries or PV panels in some systems can be utilized to achieve high-efficiency transformer-less inverters. The single-phase three-level H-bridge [100] , 19-level [142] , and 27-level [168] cascaded H-bridge (CHB) inverters as well as the three-phase nine-level cascaded H-bridge [169] inverter are used for the integration of DG to the grid to compensate for PQ problems in PCC.
PPT Slide
Lager Image
Configuration of the MFI-CH system.
Hybrid multilevel MFI (MFI-HM): The topology of the five-level hybrid clamped inverter developed in [170] is shown in Fig. 17 . V dc represents the generator and MPPT. The hybrid clamped inverter can maintain the balanced voltages of the DC link capacitors regardless of the characteristics of the load or its operation mode. The hybrid clamped topology can control active and reactive flows regardless of the conditions of the load and has a simple arrangement that satisfies the voltage balance of the DC link capacitors. The disadvantage of the hybrid clamped topology is the number of components used. Fig. 18 shows the system configuration of the cascaded NPC/H-bridge inverter to integrate PV arrays to the utility grid. The system is comprised of two PV arrays of the same power rating, a nine-level cascaded NPC/H-bridge inverter, an LCL passive filter, and a utility grid.
PPT Slide
Lager Image
Configuration of the five-level MFI-HM system.
PPT Slide
Lager Image
Configuration of the cascaded NPC/H-bridge inverter.
The main structure of the proposed topology is comprised of two similar NPC cascaded cells. The inverter phase voltage is the sum of the output voltages of the two cascaded cells. Five different voltage output levels (+2V dc , +V dc , 0, -V dc , and –2V dc ) are produced at the AC output terminal of the cascaded model using proper switching techniques.
The proposed topology has the following advantages: (1) MV operation improves the PQ of the currents injected into the utility grid; (2) reduction in cable size; (3) low step-up voltage is required; and (4) increased system efficiency. The configuration in [127] has the advantages of both multi-phase generators and multilevel inverters and serves as a guide to obtaining an optimum solution for multi MW rated WECS [137] .
Multilevel current source MFI (MFI-CM): MFI-CM allows for superior control of the current fed to the electrolyzer; thus, the level of operation is near the point of maximum efficiency. The power factor and/or harmonics can be compensated for by modifying the inverter control strategy to acquire an active power filter. The seven-level MFI-CM in [173] is used to interface the electrolyzer or fuel cell with the utility grid as shown in Fig. 20 . It consists of three similar modules and has the ability to generate seven-level output current. Each module has six switching devices with bidirectional voltage blocking abilities and two inductors to maintain the balance of the currents. A capacitor bank prevents high voltages caused by the commutation of the currents in the inductive loads. A phase-shifted carrier sinusoidal PWM-based control for MFI-CM is used to regulate the current in each module.
PPT Slide
Lager Image
Configuration of the MFI-MM system.
PPT Slide
Lager Image
Configuration of the MFI-CM system.
Z-source multilevel MFI (MFI-ZM): In [174] , an improved interface for the utility grid connection of the PV generation systems was proposed.
The proposed topology consists of a three-level cascaded ZSI and allows for efficient, flexible, and high-quality power generation from the PV plant as shown in Fig. 21 .
PPT Slide
Lager Image
The configuration of the MFI-ZM system.
b) Distributed multilevel MFI (MFI-DM): In [189] , an inverter system interfaced with the utility grid was proposed. The system improves the voltage quality of micro-grid applications as shown in Fig. 22 . The proposed topology consists of two three-phase four-leg inverters with DG sources and linear and non-linear loads. The topology uses a series-parallel structure to construct a grid-interfacing system.
PPT Slide
Lager Image
Configuration of the MFI-DM system.
The proposed system can withstand voltage-related disturbances and maintain the power transfer between DG and the utility grid while maintaining a superior quality voltage for the customer loads. Voltage unbalance correction and harmonic current compensation functions are also achieved with MFI-DM.
- B. Classification Based on the Compensated Variable
The main aim of an MFI is compensate for PQ problems (voltage quality problems, such as sags, swells, flickering, unbalance, harmonics, and current quality problems, including harmonics, reactive current, unbalance and neutral current) at the connection point of the DG sources to the utility grid. The classification of MFIs based on the compensation approach is presented in Table I .
PPT Slide
Lager Image
Several abbreviations of MFIs based on the topology or application were described in Section II. Ten key abbreviations, namely, MFI-ML, MFI-VM, MFI-CM, MFI-ZM, MFI-DC, MFI-FC, MFI-CH, MFI-HM, MFI-MM, and MFI-DM, are presented in Table II . These abbreviations can be used to emphasize the main features of MFIs more concisely [26] . MFI-DC, MFI-FC, and MFI-CH are generally based on the VSI topology.
PPT Slide
Lager Image
An advanced control technique is very critical for the efficient operation of power electronic-based MFI systems. MFI control techniques calculate the current and voltage reference signals and determine the switching sequence of the inverter switches. Frequency domain techniques, such as fast Fourier transform, are rarely used because of the large computation time and delay in calculating the reference signals [26] . Time domain techniques allow for the instantaneous derivation of compensating currents or voltage signals. A large number of control techniques have been successfully applied to MFIs in the time domain.
The most common time domain control methods used for MFIs are instantaneous active and reactive power (also called three-phase pq theory) [175] and synchronous reference frame (also called three-phase dq theory) methods [176] . These methods convert the current and voltage signals in the ABC frame into the stationary reference frame (pq theory) or the synchronously rotating frame (dq theory) to extract the fundamental and harmonic quantities [26] . Instantaneous active and reactive powers are calculated in pq theory, whereas dq theory is concerned with the free current of the source voltage. Real and reactive powers are concerned with fundamental components (pq theory). The fundamental components in the distorted voltage or current (dq theory) are DC quantities in these theories. MFI controllers based on instantaneous active and reactive power theory were studied in [30] , [60] , [71] , [72] , [77] , [78] , [81] , [82] , [99] , [100] , [106] , [112] , [114] , [133] , [137] , [140] , [153] , [177] , and [178] , whereas synchronously rotating frame theory-based controllers were studied in [55] - [57] , [63] , [65] , [66] , [70] , [80] , [82] , [85] , [87] - [89] , [101] , [103] , [104] , [107] , [118] , [120] , [129] , [139] , [148] , [150] , [151] , [162] , [165] - [167] , [174] , and [179] - [182] .
Synchronously rotating frame theory has limitations whenthe source voltages are unbalanced and/or distorted. Dq theory is modified and referred to as “dq0 theory” to eliminate these limitations as can be found in [86] , [90] , [113] , [130] , and [157] . A new adaptive linear neuron (ADALINE) technique called MO-ADALINE was implemented in multi-output (MO) systems to track or estimate the parameters and symmetrical components. The control strategy involves the use of combined fuzzy logic controller for voltage regulation and processing unit-based ADALINE for harmonics, unbalance, and reactive power compensation [63] .
Moreover, a new adaptive neuro-fuzzy control method is utilized to achieve smooth bi-directional power flow and nonlinear unbalanced load compensation simultaneously; in this case, the traditional PI controller might be insufficient because of the instantaneous changes in the dynamics of the system [132] , [183] . In [69] , a novel integrated diagnostic system was developed for islanding detection using a neuro-fuzzy model for grid-tied inverter-based DGs. In [69] , an adaptive neuro-fuzzy inference system was used for islanding detection.
In [126] , a current control method for inverters based on the sigma delta modulation algorithm called the sigma delta-based current controlled voltage source inverter (ΣΔ_CC_VSI) interfaced with DG generators was studied. A particle swarm optimization method was used for the optimum tuning of the controllers as a result of the existent number of PI controllers. ΣΔ_CC_VSI minimizes the harmonics of the unfiltered voltage. Thus, it is powerful in minimizing electromagnetic interference, which is critical for sensitive loads [26] .
The combination of methods and strategies results in diverse control concepts used in grid-connected VSCs, such as PI controller-based voltage oriented controller (PI-VOC) [111] , [136] , space-vector pulse width modulation (SV-PWM) and voltage oriented control (VOC) method [174] , direct power control (DPC) with space vector modulation (SVM) based on sliding mode control (SMC) [97] , DPC-based SVM [101] , DPC strategy with non-linear SMC with and SVM [117] , and DPC-EMC (electromagnetic compatibility) [73] . DC-bus voltage control has a critical role in delivering the required MFI performance. During the sudden changes in system dynamic conditions, such as instantaneous load change or voltage sag/swell, the DC-link controller responds quickly to return the DC-bus voltage to its reference point with minimum delay time and overshoot. The PI-based DC-link voltage controller is simple to implement and is therefore preferred by most researchers, including [30] , [32] , [35] , [38] , [39] , [55] , [59] , [60] - [62] , [67] , [75] , [76] , [79] , [81] , [92] , [101] - [103] , [107] , [116] - [118] , [120] , [122] - [128] , [130] , [134] , [136] , [139] , [140] , [145] , [146] , [148] , [155] , [157] , [160] , [161] , [165] , [167] , [171] , and [184] - [186] .
To improve the response time of PI controller-based methods, researchers have developed several methods, including a spatial repetitive controller [128] , neuro-fuzzy controller [132] , [141] , PI-type fuzzy logic controller [162] , adaptive hysteresis band controller [78] , adaptive sensorless controller [51] , sliding mode controller [97] , H controller [131] , H repetitive controller [203], unified DC-link current controller [101] , Lyapunov function-based current controller [105] , fast dynamic high-performance non-linear controller [106] , predictive current controller based on SV-PWM [158] , and current and reactive power controllers [108] . SVM has proven to be a popular and favorable PWM scheme because of its high DC-link voltage utilization [93] , [108] , [110] , [114] , [115] , [164] , [169] , model predictive control (MPC) [84] , adaptive hysteresis controller [89 , 110 , 113] , model-based control [111] , fuzzy with hysteresis current controller [45] , automatic voltage regulation [188] , auto-voltage regulator designed based on discrete PID algorithm [119] , and the optimal linear-adaptive regulator, which has been selected for the controller using linear-quadratic regulator control technique [158] . In [137] , a stationary-frame resonant controller with direct feedback variables was utilized to arrange a dual-loop control scheme. The control methods studied in [41] , [65] , [73] , [150] , and [190] have no additional control loop for DC bus voltage regulation. The DC-link is controlled by either a current or voltage control loop.
Some of the available MFIs are mainly experimental prototypes or small-scale installations whose capacities are low in general as shown in Table III . The available capacities of MFIs in single-phase are small; these MFIs are mainly implemented in PV grid-connected systems (<4 kVA). However, the available capacities of MFIs in three-phase are usually large; these MFIs are used in wind and solar plants (<400 kVA). The capacity of existing MFIs is small and should promote the experimental prototype for industrial applications.
PPT Slide
Lager Image
Both active power flow control and compensation of PQ problems are achieved in the same MFIs in DG generators that involve the use of few power electronic components, are small, and have high efficiency, low investment cost, reduced maintenance cost, and high reliability. The reduction in investment, operation, and maintenance cost as well as the enhancement of the cost-effective features of MFIs were proposed in [77] , [163] , and [191] .
This paper presented an exhaustive review of the MFIs utilized to improve the power quality in the utility grid and at consumer level. The review and classification of published articles show that MFIs can help mitigate both current- and voltage-related PQ disturbances. The latest developments in grid-tied inverters fed by RES-based DGs (i.e., PV and/or wind systems) have introduced new regulations and standards to enhance PQ. The development of new control strategies and execution of multifunctional compensation capability are the main research trends related to both active power flow control and mitigation of various PQ disturbances using MFIs. The different aspects of MFIs and the new developments in this field of research were discussed in detail in this study.
MFI-based DG systems are essential to future utility grids for the delivery of high-quality, reliable, and efficient electricity supply. To achieve this goal, various multi-level topologies and structures should be employed to increase the size of installed MFIs. The classification of MFIs will help researchers, users, and suppliers of electrical power to acquire an overview for further research and studies on this subject.
Ahmet Teke received his B.S., M.Sc., and Ph.D. degrees in electrical and electronics engineering from Cukurova University, Adana, Turkey in 2002, 2005, and 2011, respectively. He is currently an assistant professor at the Department of EEE, Cukurova University. His current research interests include custom power devices, renewable energy sources, control of power electronic converters, PWM modulation techniques, multifunctional inverters, and power system harmonics.
Mohammad Barghi Latran received his B.S. and M.Sc. degrees in electrical and electronics engineering from Islamic Azad University Ardebil Branch, Ardebil, Iran, in 2007 and from Hacettepe University, Ankara, Turkey, in 2012, respectively. He is currently pursuing his Ph.D. degree at the Department of EEE, Cukurova University, Adana, Turkey. His current research interests include applications of power electronics in distribution systems, power quality enhancement, active power filters, static VAR compensators, applications of power electronics in renewable energy resources, and grid interconnection issues.
Arai J. , Iba K. , Funabashi T. , Nakanishi Y. , Koyanagi K. , Yokoyama R. 2008 “Power electronics and its applications to renewable energy in Japan” IEEE Circ. Sys. Mag. 8 (3) 52 - 66    DOI : 10.1109/MCAS.2008.928420
Justo J.J. , Mwasilu F. , Lee J. , Jung J.W. 2013 “AC-microgrids versus DC-microgrids with distributed energy resources: A review” Renewable and Sustainable Energy Reviews 24 387 - 405    DOI : 10.1016/j.rser.2013.03.067
Akorede M.F. , Hizam H. , Aris I. , Kadir Ab 2010 “A critical review of strategies for optimal allocation of distributed generation units in electric power systems” IREE 5 (2) 593 - 600
Bhusal P. , Zahnd A. , Eloholma M. , Halonen L. 2007 “Energy-efficient innovative lighting and energy supply solutions in developing countries” IREE 2 (1) 665 - 670
Laaksonen H. , Mohamed A. 2008 “Stability of microgrid with different configurations after islanding due to fault in the utility grid” IREE 3 (3) 498 - 512
Salam A. A. , Barakat G. , Hannanand M. A. , Shareef H. 2010 “An improved inverter control scheme for managing the distributed generation units in a microgrid” IREE 5 (5) 891 - 899
Belfkira R. , Barakat G. , Nichita C. 2008 “Sizing optimization of a stand-alone hybrid power supply unit: Wind/PV system with battery storage” IREE 3 (5) 820 - 828
Mazumder S. , Burra R. , Huang R. , Tahir M. , Acharya K. 2010 “Universal grid-connected fuel-cell inverter for residential application” IEEE Trans. Ind. Electron. 57 (10) 3431 - 3447    DOI : 10.1109/TIE.2009.2038943
Nergaard T. A. , Ferrell J. F. , Leslie L. G. , Lai J. S. 2002 “Design considerations for a 48 V fuel cell to split single phase inverter system with ultracapacitor energy storage” IEEE Conf. Power Electr. Spec. 2007 - 2012
Selvaraj J. , Rahim N. A. 2009 “Multilevel inverter for grid-connected PV system employing digital PI controller” IEEE Trans. Ind. Electron. 56 (1) 149 - 158    DOI : 10.1109/TIE.2008.928116
Patel H. , Agarwal V. 2009 “MPPT scheme for a PV-fed single-phase single-stage grid-connected inverter operating in CCM with only one current sensor” IEEE Trans. Energy Convers. 247 (1) 256 - 263    DOI : 10.1109/TEC.2008.2005282
Jia Y. , Yang Z. , Cao B. 2002 “A new maximum power point tracking control scheme for wind generation” IEEE Power System Tech. Conf. 144 - 148
Dugan R. C. , McGranaghan M. F. , Beaty H. W. 1996 Electrical Power Systems Quality McGraw-Hill
Sankaran C. 2002 Power Quality CRC Press Boca Raton
1992 IEEE recommended practices and requirements for harmonic control in electrical power systems, IEEE Standard 519-1992
2003 IEEE standard for interconnecting distributed resources with electric power systems, IEEE Standard 1547-2003
Hingorani N. G. , Gyugyi L. 2000 Understanding FACTS: Concepts and Technology of Flexible AC Transmission Systems IEEE Press
Sood V. K. 2004 HVDC and FACTS Controllers – Applications of Static Converters in Power Systems Kluwer
Ghosh A. , Ledwich G. 2002 Power quality enhancement using custom power devices Kluwer
Cobben J. F. G. , Kling W. L. , Myrzik J. M. A. 2005 “Power quality aspects of a future micro grid” in Proc. the IEEE Int.Conf. Future Power Sys 1 - 5
Enslin J. H. R. , Heskes P. J. M. 2004 “Harmonic interaction between a large number of distributed power inverters and the distribution network” IEEE Trans. Power Electron. 19 (6) 1586 - 1593    DOI : 10.1109/TPEL.2004.836615
Bollen M. H. , Hassan F. 2011 Integration of Distributed Generation in the Power System Wiley-IEEE Press
Salarvand A. , Mirzaeian B. , Moallem M. 2010 “Obtaining a quantitative index for power quality evaluation in competitive electricity market” IET Gener. Trans. Distr. 4 (7) 810 - 823    DOI : 10.1049/iet-gtd.2009.0479
Kumar A. A. , Rao J.S. 2012 “Power quality improvement of grid interconnected 3-phase 4-wire distribution system using fuzzy logic control” IJERT 1 (4) 1 - 5
Ma T. T. 2012 “Power quality enhancement in micro-grids using multifunctional DG inverters” in Proc. Int. Multi Conf. of Eng. Vol. 2
Khadkikar V. 2012 “Enhancing electric power quality using UPQC: A comprehensive overview” IEEE Trans. Power Electron. 27 (5) 2284 - 2297    DOI : 10.1109/TPEL.2011.2172001
Gungor V. C. , Sahin D. , Kocak T. , Ergut S. , Buccella C. , Cecati C. , Hancke G. P. 2011 “Smart grid technologies: Communication technologies and standards” IEEE Trans. Ind. Informat. 7 (4) 529 - 539    DOI : 10.1109/TII.2011.2166794
Rahman M .A. , Al-Shaer E. , Bera P. A. 2013 “Noninvasive threat analyzer for advanced metering infrastructure in smart grid” IEEE Trans. Smart Grid 4 (1) 273 - 287    DOI : 10.1109/TSG.2012.2228283
Liu N. , Chen J. , Zhu L. , Zhang J. , He Y. 2013 “A key management scheme for secure communications of advanced metering infrastructure in smart grid” IEEE Trans. Ind. Electron. 60 (10)
Macken K. J. P. , Vanthournout K. , Keybus J. V. , Deconinck G. , Belmans R. J. M. 2004 “Distributed control of renewable generation units with integrated active filter” IEEE Trans. Power Electr. 19 (5) 1353 - 1360    DOI : 10.1109/TPEL.2004.833450
Alatrash H. , Mensah A. , Mark E. , Haddad G. , Enslin J. 2012 “Generator emulation controls for photovoltaic inverters” IEEE Trans. Smart Grid 3 (2) 996 - 1011    DOI : 10.1109/TSG.2012.2188916
Kim H. , Yu T. , Choi S. 2008 “Indirect current control algorithm for utility interactive inverters in distributed generation systems” IEEE Trans. Power Electron. 23 (3) 1342 - 1347    DOI : 10.1109/TPEL.2008.920879
Ko S. H. , Lee S. R. , Dehbonei H. , Nayar C. V. 2006 “Application of voltage and current-controlled voltage source inverters for distributed generation systems” IEEE Trans. Energy Convers. 21 (3) 782 - 792    DOI : 10.1109/TEC.2006.877371
Enslin H. R. J. , Heskes J. M. P. 2004 “Harmonic interaction between a large number of distributed power inverters and the distribution network” IEEE Trans. Power Electron. 19 (6) 1586 - 1593    DOI : 10.1109/TPEL.2004.836615
Trujillo C.L. , Velasco D. , Figueres E. , Garcerá G. 2010 “Analysis of active islanding detection methods for grid-connected micro inverters for renewable energy processing” Appl. Energy 87 (11) 3591 - 3605    DOI : 10.1016/j.apenergy.2010.05.014
Renders B. , De Gusseme K. , Ryckaert W. R. , Vandevelde L. 2009 “Converter-connected distributed generation units with integrated harmonic voltage damping and harmonic current compensation function” Electric Power Sys. Res. 79 (1) 70 -    DOI : 10.1016/j.epsr.2008.05.006
Goyal S. , Ghosh A. , Ledwich G. 2009 “Active power flow control in a distribution system using discontinuous voltage controller” Electric Power Sys. Res. 79 (1) 255 - 264    DOI : 10.1016/j.epsr.2008.06.002
Hassaine L. , Olias E. , Quintero J. , Haddadi M. 2009 “Digital power factor control and reactive power regulation for grid-connected photovoltaic inverter” Ren. Energy 34 (1) 315 - 321    DOI : 10.1016/j.renene.2008.03.016
Hussain E. K. , Bingham C. M , Stone D. 2011 “Grid connected PVs & Wind turbine with a wide range of reactive power control and active filter capability,” IEEE Int. Conf. Inn. Smart Grid Tech.
Wen C. , Lu G. , Wang P. , Li Z. , Liu X. , Fan Z. 2011 “Vector control strategy for small-scale grid connected PMSG wind turbine converter” 2nd IEEE Int. Conf. Inn. Smart Grid Tech. 1 - 7
Jena S. , Babu B. C. , Naik N. K. , Mishra G. 2011 “Performance improvement of single-phase grid–connected PWM inverter using PI with hysteresis current controller” IEEE Int. Conf. Energy, Auto. Sig. 1 - 5
Shao R. , Kaye M. , Chang L. 2011 “Advanced building blocks of power converters for renewable energy based distributed generators” 8nd IEEE Int. Conf. Power Electr. 2168 - 2174
Ramai G. , Tran-Quoc T. , Hadjsaid N. 2005 “Fuzzy logic, supervision and control of distributed generators” 18th Int.Conf. Exh. Elec. Distr. 6-9 June 1 - 5
Vandoorn T. L. , Ionescu C. M. , De Kooning J. D. M. , De Keyser R. , Vandevelde L. 2013 “Theoretical analysis and experimental validation of single-phase direct versus cascade voltage control in islanded microgrids” IEEE Trans. Ind. Electron. 60 (2) 789 - 798    DOI : 10.1109/TIE.2012.2205362
Jena S. , Babu B.C. 2011 “Power quality improvement of 1-Φ grid-connected PWM inverter using fuzzy with hysteresis current controller” IEEE 10th Int. Conf. Env. Elec. Eng. 8-11 May 1 - 4
Yafaoui A. , Wu B. , Kouro S. 2010 “Improved active frequency drift anti-islanding method with lower total harmonic distortion” IEEE 36th Annu. Conf. Ind. Elec. Soc. 3216 - 3221
Serban I. , Marinescu C. 2010 “Active power decoupling circuit for a single-phase battery energy storage system dedicated to autonomous microgrids” IEEE Int. Symp. Ind. Elec. 4-7 Jul. 2717 - 2722
Neves P. , Gonçalves D. , Pinto J. G. , Alves R. , Afonso J. L. 2009 “Single phase shunt active filter interfacing renewable energy sources with the power grid” IEEE 35th Annu. Conf. Ind. Elec. 3264 - 3269
Buticchi G. , Barater D. , Lorenzani E. , Franceschini G. 2012 “Digital control of actual grid-connected converters for ground leakage current reduction in PV transformerless systems” IEEE Trans. Ind. Inf. 8 (3) 563 - 572    DOI : 10.1109/TII.2012.2192284
Lin B. R. , Ji Chen J. 2006 “Three-phase two-leg inverter for stand-alone and grid-connected renewable energy systems” IEEE Region 10 Conf. 1 - 4
Picardi C. , Sgrò D. , Gioffré G. 2012 “A new active filtering technique for grid-connected inverters” IEEE Inte. Symp. Power Elect., Elec. Dri., Autom. Moti. 900 - 905
Ahmed K.H. , Massoud A.M. , Finney S.J. , Williams B.W. 2009 “Autonomous adaptive sensorless controller of inverter based islanded distributed generation system” IET Power Electr. 2 (3) 256 - 266    DOI : 10.1049/iet-pel.2008.0029
Antoniewicz P. , Kazmierkowski M. P. 2008 “Virtual flux based predictive direct power control of ac/dc converters with online inductance estimation” IEEE Tran. Ind. Electron. 55 (12) 4381 - 4390    DOI : 10.1109/TIE.2008.2007519
Zeng Q. , Chang L. 2008 “An advanced SVPWM-based predictive current controller for three-phase inverters in distributed generation systems” IEEE Tran. Ind. Electron. 55 (3) 1235 - 1246    DOI : 10.1109/TIE.2007.907674
Teodorescu R. , Blaabjerg F. 2004 “Flexible control of small wind turbines with grid failure detection operating in stand-alone and grid-connected mode” IEEE Tran. Power Electron. 19 (5) 1323 - 1332    DOI : 10.1109/TPEL.2004.833452
Abdel Y. 2011 “Mitigation of converter-grid resonance, grid-induced distortion, and parametric instabilities in converter-based distributed generation” IEEE Tran. Power Electron. 26 (3) 983 - 996    DOI : 10.1109/TPEL.2010.2070878
Dasgupta S. , Mohan S. N. , Sahoo S. K. , Panda S. K. 2013 “Lyapunov function-based current controller to control active and reactive power flow from a renewable energy source to a generalized three-phase microgrid system,” IEEE Tran. Ind. Electron. 60 (2) 799 - 813    DOI : 10.1109/TIE.2012.2206356
Delfino F. , Procopio R. , Rossi M. , Ronda G. 2010 “Integration of large-size photovoltaic systems into the distribution grids: A P–Q chart approach to assess reactive support capability” IET Ren. Power Gener. 4 (4) 329 - 340    DOI : 10.1049/iet-rpg.2009.0134
Singh M. , Khadkikar V. , Chandra A. 2011 “Grid synchronization with harmonics and reactive power compensation capability of a permanent magnet synchronous generator-based variable speed wind energy conversion system” IET Power Electr. 4 (1) 122 - 130    DOI : 10.1049/iet-pel.2009.0132
Camacho A. , Castilla M. , Miret J. , Vasquez J. C. , Alarcón-Gallo E. 2013 “Flexible voltage support control for three-phase distributed generation inverters under grid fault” IEEE Trans. Ind. Electron. 60 (4) 1429 - 1441    DOI : 10.1109/TIE.2012.2185016
Kazmierkowski M. P. , Jasinski M. , Wrona G. 2011 “DSP-based control of grid-connected power converters operating under grid distortions” IEEE Trans. Ind. Informat. 7 (2) 204 - 211    DOI : 10.1109/TII.2011.2134856
Tang X. , Tsang K. M. , Chan W. L. 2012 “A power quality compensator with DG interface capability using repetitive control” IEEE Trans. Energy Convers. 27 (2) 213 - 219    DOI : 10.1109/TEC.2012.2183874
Marei M. I. , El-Saadany E. F. , Salama M. M. A. 2004 “A novel control algorithm for the DG interface to mitigate power quality problems” IEEE Trans. Power Del. 19 (3) 1384 - 1392    DOI : 10.1109/TPWRD.2004.829922
He J. , Li Y. W. , Munir M. S. 2012 “A flexible harmonic control approach through voltage-controlled DG–grid interfacing converters” IEEE Trans. Ind. Electron. 59 (1) 444 - 455    DOI : 10.1109/TIE.2011.2141098
Zamani M. A. , Yazdani A. , Sidhu T. S. 2012 “A control strategy for enhanced operation of inverter-based microgrids under transient disturbances and network faults” IEEE Trans. Power Del. 27 (4) 1737 - 1747    DOI : 10.1109/TPWRD.2012.2205713
Pouresmaeil E. , Miracle D. M. , Bellmunt O. G. , Jané J. B. 2010 “A multi-objective control strategy for grid connection of DG (distributed generation) resources” Energy 35 (12) 5022 - 5030    DOI : 10.1016/
Li S. , Haskew T. A. , Hong Y. K. , Xu L. 2011 “Direct-current vector control of three-phase grid-connected rectifier–inverter” Electric Power Sys. Res. 81 (2) 357 - 366    DOI : 10.1016/j.epsr.2010.09.011
Gidwani L. , Tiwari H. , Bansal R.C. 2013 “Improving power quality of wind energy conversion system with unconventional power electronic interface” Int. Jour. of Elec. Power & Energy Sys. 44 (1) 445 - 453    DOI : 10.1016/j.ijepes.2012.07.051
Hashemi F. , Ghadimi N. , Sobhani B. 2013 “Islanding detection for inverter-based DG coupled with using an adaptive neuro-fuzzy inference system” Int. Jour. Elec. Power & Energy Sys. 45 (1) 443 - 455    DOI : 10.1016/j.ijepes.2012.09.008
He C. , Xie X. , Yan H. , Xie C. , Chen G. 2011 “A novel grid-connected converter with active power filtering function” Energy Proc. 12 348 - 354    DOI : 10.1016/j.egypro.2011.10.047
Savaghebi M. , Vasquez J. C. , Jalilian A. , Guerrerob J. M. , Lee T. L. 2013 “Selective compensation of voltage harmonics in grid-connected microgrids” Math. Comp. Simu. 91 211 - 228    DOI : 10.1016/j.matcom.2012.05.015
Tsengenes G. , Adamidis G. 2011 “Investigation of the behavior of a three phase grid-connected photovoltaic system to control active and reactive power” Elec. Power Sys. Res. 81 (1) 177 - 184    DOI : 10.1016/j.epsr.2010.08.008
Cirrincione M. , Pucci M. , Vitale G. 2011 “Direct power control of three-phase VSIs for the minimization of common-mode emissions in distributed generation systems” Elec. Power Sys. Res. 81 (4) 830 - 839    DOI : 10.1016/j.epsr.2010.11.007
Eltamaly A. M. 2012 “A novel harmonic reduction technique for controlled converter by third harmonic current injection” Elec. Power Sys. Res. 91 104 - 112    DOI : 10.1016/j.epsr.2012.05.014
Chinchilla M. , Arnalte S. , Burgos J.C. , Rodrı´guez J.L. 2006 “Power limits of grid-connected modern wind energy systems” Ren. Energy 31 (9) 1455 - 1470    DOI : 10.1016/j.renene.2004.03.021
Mohoda S. W. , Hatwara S. M. , Awareb M. V. 2011 “Grid support with variable speed wind energy system and battery storage for power quality” Energy Proc. 12 1032 - 1041    DOI : 10.1016/j.egypro.2011.10.135
Chen Z. , Blaabjerg F. , Pedersen J. K. 2005 “A multi-functional power electronic converter in distributed generation power systems” IEEE 36th Conf. Power Electr. 1738 - 1744
Mosazadeh Y. , Fathi H. , Sheykholeslami A.R. , Hajizadeh M. 2012 “Adaptive hysteresis band controlled grid connected PV system with active filter function” IEEE Conf. Power Eng. Ren. Energy 1 - 6
Pouresmaeil E. , Miguel-Espinar C. , Massot-Campos M. , Montesinos-Miracle D. , Gomis-Bellmunt O. 2013 “A control technique for integration of DG units to the electrical networks” IEEE Trans.Ind. Electr. 60 (7) 2881 - 2893    DOI : 10.1109/TIE.2012.2209616
Dehghani M. T. , Vahedi A. , Savaghebi M. , Ouerrero J. M. 2012 “Voltage quality improvement in islanded microgrids supplying nonlinear loads” IEEE Conf. Power Electr. Drive Syst. Tech. 360 - 365
Eren S. , Bakhshai A. , Jain P. 2012 “Control of grid-connected voltage source inverter with LCL filter,” IEEE Annu. Conf. Appl. Power Electr. 1516 - 1520
Savaghebi M. , Guerrero J. M. , Jalilian A. , Vasquez J. C. , Lee T. L. 2011 “Hierarchical control scheme for voltage harmonics compensation in an islanded droop-controlled microgrid” IEEE 9th Int. Conf. Power Electr. Drive Sys. 89 - 94
Ilango K. , Manitha P. V. , Manjula G. N. 2012 “An enhanced controlled for shunt active filter interfacing renewable energy source and grid” IEEE 5th Int. Conf. Power Electr. 1 - 5
Hwang T. S. , Y.Park S. , Gupta S. 2012 “Distributed model predictive control of multi-functional power conditioning system for building energy efficiency” IEEE Conf. Energy Convers. 2751 - 2758
Khadkikar V. , Varma R. K , Seethapathy R. 2012 “Impact of distributed generation penetration on grid current harmonics considering non-linear loads” IEEE 3th Int. Conf. Power Electr. Distr. Gener. Sys. 608 - 614
Huseinbegovic S. , Perunicic B. , Milosavljevic C. , Veselic B. 2012 “Direct power control for various topologies of three phase grid-connected voltage sources converters using sliding mode control” IEEE Int. Conf. Ind. Tech. 795 - 801
Dasgupta S. , Mohan S. N. , Sahoo S. K. , Panda S. K. 2011 “Evaluation of current reference generation methods for a three-phase inverter interfacing renewable energy sources to generalized micro-grid” IEEE 9th Int. Conf. Power Electr. Drive Sys. 316 - 321
Mehta G. , Singh S. P. , Patidar R. D. 2011 “Non-linear load compensation in Fuel Cell grid interfaced system using active power filter” IEEE 9th Int. Conf. Power Electr. Drive Sys. 197 - 202
Jena S. , Babu B.C. , Mishra G. , Naik A. K. 2011 “Reactive power compensation in inverter-interfaced distributed generation” IEEE Int. Conf. Energy, Auto. Sig. 1 - 6
Jena S. , Babu B. C. , Naik A. 2011 “Experimental study on reactive power management in inverter-interfaced distributed generation system” IET Int. Conf. Sust. Energy Intell.Sys. 80 - 85
Nouri T. , Ghasemzadeh S. 2011 “A new flexible distributed generation unit for active power generation and harmonic compensation under non-ideal source voltages condition” IEEE 7th Int. Conf. Elec. Electr. Eng. 263 - 267
Wang B. C. , Guo X. O. , Huang Xi. K. , Wu W. Y. 2012 “Flexible control of three-phase distributed generation systems for voltage rise mitigation in microgrid” Przegląd Elektrotechniczny (Electrical Review) 7b
Al-Saedi W. , Lachowicz S. W. , Habibi D. 2011 “An optimal current control strategy for a three-phase grid-connected photovoltaic system using particle swarm optimization” IEEE Conf. Power Eng. Auto. 286 - 290
Vekhande V. , Fernandes B. G. 2011 “Bidirectional current-fed converter for integration of DC micro-grid with AC grid,” IEEE Annu. Conf. 1 - 5
Hamadi A. , Rahmani S. , Al-Haddad K. , Al-Turki Y.A. 2011 “A three-phase three wire grid-connect photovoltaic energy source with sepic converter to track the maximum power point” IEEE 37th Annu. Conf. Ind. Electr. Soc. 3087 - 3092
Dasgupta S. , Mohan S. N. , Sahoo S. K. , Panda S. K. 2011 “A FBD theory based grid frequency independent current reference generation method for a three phase inverter interfacing renewable energy sources to generalized micro-grid” IEEE 37th Annu. Conf. Ind. Electr. Soc. 3076 - 3081
Xiao L. , Huang S. , Zheng L. , Xu Q. , Huang K. 2011 “Sliding mode SVM-DPC for grid-side converter of D-PMSG under asymmetrical faults” IEEE Int. Conf. Electr. Mach. Sys. 1 - 6
Agamy A. G. , Alaboudy A.H. K. , Mostafa H. E. , Fekry M.Y. 2011 “Bacterial foraging-based PI controller of inverter-based distributed generators” IEEE Conf. PowerTech 1 - 7
Su L. , Li G. , Jin Z. 2011 “Modeling, control and testing of a voltage source inverter based microgrid” IEEE 14th Int. Conf. Elec. Utility Dereg. Restru. Power Tech. 724 - 729
Pouresmaeil E. , Miracle D. M. , Bellmunt O. G. 2011 “Control scheme of three-level H-bridge converter for interfacing between renewable energy resources and AC grid” 14th Euro. Conf. Power Electr. Appl. 1 - 9
Dai J. , Xu D. , Wu B. , Zargari N. R. 2011 “Unified DC-link current control for low-voltage ride-through in current-source-converter-based wind energy conversion systems” IEEE Trans. Power Electron. 26 (1) 288 - 297    DOI : 10.1109/TPEL.2010.2059377
Dai J. , Xu D. , Wu B. 2009 “A novel control scheme for current-source-converter-based PMSG wind energy conversion systems” IEEE Trans. Power Electron. 24 (4) 963 - 972    DOI : 10.1109/TPEL.2008.2010259
Liu X. , Loh P. C. , Wang P. , Blaabjerg F. 2013 “A direct power conversion topology for grid integration of hybrid AC/DC energy resources” IEEE Trans. Ind. Electron. 60 (12) 5696 - 5707    DOI : 10.1109/TIE.2012.2236993
Popat M. , Wu B. , Zargari N. R. 2013 “Fault ride-through capability of cascaded current-source converter-based offshore wind farm” IEEE Trans. Sust. Energy 4 (2)    DOI : 10.1109/TSTE.2012.2223246
Dasgupta S. , Mohan S. N. , Sahoo S. K. , Panda S. K. 2011 “A Lyapunov function based current controller to control active and reactive power flow in a three phase grid connected PV inverter under generalized grid voltage conditions,” IEEE 8th Int. Conf. Power Electr. 1110 - 1117
Dasgupta S. , Mohan S. N. , Sahoo S. K. , Panda S. K. 2011 “Derivation of instantaneous current references for three phase PV Inverter connected to grid with active and reactive power flow control” IEEE 8th Int. Conf. Power Electr. 1228 - 1235
Abo-Al-Ez K.M. , Xia X. , Zhang J. 2012 “Smart interconnection of a PV/Wind DG micro grid with the utility distribution network” IEEE 9th Conf. Ind. Commer. Energy 1 - 8
Mahendran K. , Indhumath B. , Prabha S.u. , Suryakala S. 2012 “Adapted SVPWM for T-source inverter for renewable energy system” IEEE Int. Conf. Comp., Electr. Elec. Tech. 404 - 408
Goyal M. , Gupta R. 2012 “Power flow control in distributed microgrid with wind energy system” IEEE Student Conf. Eng. Sys. 1 - 5
Jena S. , Babu B. C. , Samantaray S.R. , Mohapatra M. 2011 “Comparative study between adaptive hysteresis and SVPWM current control for grid-connected inverter system” IEEE Students' Tech. Symp.
Paál E. , Weitzl Z. , Choi C. S. 2011 “Grid management functions built in PV inverters for distributed power generation” IEEE 8th Int. Conf. Power Electr. 2637 - 2644
Vasquez J. C. , Guerrero J. M. , Savaghebi M. , Teodorescu R. 2011 “Modeling, analysis, and design of stationary reference frame droop controlled parallel three-phase voltage source inverters” IEEE 8th Int. Conf. Power Electr. 272 - 279
Babu B. C. , Mohapatra M. , Jena S. , Naik A. 2010 “Dynamic performance of adaptive hysteresis current controller for mains-connected inverter system” IEEE Int. Conf. Ind. Electr., Cont. Rob. 95 - 100
Tsengenes G. A. , Adamidis G. A. 2010 “Study of a simple control strategy for grid connected VSI using SVPWM and p-q theory” XIX Conf, Elec. Mach. 1 - 6
Zhao J. , Jiang J. 2009 “Implementation of grid-connected power conditioner for renewable energy” IEEE Int. Conf. Power Electr. Moti. Con. 2497 - 2500
Bai H. , Shang S. 2010 “A research of combined multifunctional three phase grid-connected inverter/active power filter for PV system” IEEE Int, Symp. Power Electr. Distr. Gener. Sys. 224 - 228
Hu J. , Hu B. 2010 “Direct active and reactive power regulation of grid connected voltage source converters using sliding mode control approach” IEEE Int. Symp. Ind. Electr. 3877 - 3882
Ahmed K. H. , Massoud A. M. , Finney S. J. , Williams B. W. 2010 “New voltage regulation techniques for low voltage radial feed PWM inverter based distributed networks” IEEE Int. Symp. Ind. Electr. 2241 - 2246
Du C. , Zhang C. , Chen A. 2010 “Amplitude limiting for the photo-voltaic (PV) grid-connected inverter with the function of active power filter” IEEE Int, Symp. Power Electr. Distr. Gener. Syst. 426 - 432
Kazmierkowski M. P. , Jasinski M. , BobrowskaRafal M. 2010 “AC-DC-AC converter with grid voltage dips mitigation” 14th Int. Conf. Power Electr. Moti. Con. 69 - 74
Savaghebi M. , Jalilian A. 2010 “A new control strategy for distributed generation interface converters to compensate microgrid harmonics,” Int. Symp. Power Electr. Elec. Drives Auto. Moti. 908 - 913
Paál E. , Tatai Z. 2010 “Grid connected inverters influence on power quality of smart grid” IEEE 14th Int. Conf. Power Electr. Moti. Con T6-35 - T6-39
Dannehl J. , Fuchs F. W. , Thøgersen P. B. 2010 “PI state space current control of grid-connected PWM converters with LCL filters” IEEE Trans. Power Electron. 25 (9) 2320 - 2330    DOI : 10.1109/TPEL.2010.2047408
Yue W. , Zhao C. , Lu Y. , Li G. 2010 “A scheme of connecting microgird to ac grid via flexible power electronics interface” Int. Conf. Power Sys. Tech. 1 - 6
Choi D. K. , Kang D. H. , Lee K. B. 2010 “A novel gain scheduling method for distributed power generation systems with a LCL-filter by estimating grid impedance” IEEE Int. Symp. Ind. Electr. 3438 - 3443
Davari M. , Salabeigi I. , Gharehpetian G. B. , Fathi S.H. , Kashefi Kaviani A. 2009 “Optimal tuning of multifunction current controller for sigma delta modulation inverter-based distributed generation using PSO method” IEEE Conf. 1 - 6
Duran M. J. , Kouro S. , Wu B. , Levi E. , Barrero F. , Alepuz S. 2011 “Six-phase PMSG wind energy conversion system based on medium-voltage multilevel converter” 14th Europ. Conf. Power Electr. Appl. 1 - 10
Dasgupta S. , Mohan S. N. , Sahoo S. K. , Panda S. K. 2013 “Application of four switch based three phase grid connected inverter to connect renewable energy source to a generalized unbalanced microgrid system” IEEE Trans. Ind. Electron. 60 (3) 1204 - 1215    DOI : 10.1109/TIE.2012.2202350
Amin M. M. , Mohammed O. A. 2011 “Development of high-performance grid-connected wind energy conversion system for optimum utilization of variable speed wind turbines” IEEE Trans. Sust. Energy. 2 (3) 235 - 245    DOI : 10.1109/TSTE.2011.2150251
Elmitwally A. , Rashed M. 2011 “Flexible operation strategy for an isolated PV-diesel microgrid without energy storage” IEEE Trans. Energy Convers. 26 (1) 235 - 244    DOI : 10.1109/TEC.2010.2082090
Zhong Q. C. , Liang J. , Weiss G. , Feng C. , Green T. C. 2006 “H∞control of the neutral point in four-wire three-phase DC–AC converters” IEEE Trans. Ind. Electron. 53 (5) 1594 - 1602    DOI : 10.1109/TIE.2006.882014
Singh M. , Chandra A. 2013 “Real-time implementation of ANFIS control for renewable interfacing inverter in 3P4W distribution network” IEEE Trans. Ind. Electron. 60 (1) 121 - 128    DOI : 10.1109/TIE.2012.2186103
Wang F. , Duarte J. L. , Hendrix M. A. M. 2011 “Pliant active and reactive power control for grid-interactive converters under unbalanced voltage dips” IEEE Trans. Power Electron. 26 (5) 1511 - 1521    DOI : 10.1109/TPEL.2010.2052289
Prodanovi´c M. , Green T. C. 2006 “High-quality power generation through distributed control of a power park microgrid” IEEE Trans. Ind. Electron. 53 (5) 1471 - 1482    DOI : 10.1109/TIE.2006.882019
Singh B. , Sharma S. 2012 “Design and implementation of four-leg voltage-source-converter-based VFC for autonomous wind energy conversion system” IEEE Trans. Ind. Electron. 59 (12) 4694 - 4703    DOI : 10.1109/TIE.2011.2179271
Singh M. , Khadkikar V. , Chandra A. , Varma R. K. 2011 “Grid interconnection of renewable energy sources at the distribution level with power-quality improvement features” IEEE Trans. Power Del. 26 (1) 307 - 315    DOI : 10.1109/TPWRD.2010.2081384
Wang F. , Duarte J.L. , Hendrix M.A.M. 2010 “Design and analysis of active power control strategies for distributed generation inverters under unbalanced grid faults,” IET Gener. Trans. Distrib. 4 (8) 905 - 916    DOI : 10.1049/iet-gtd.2009.0607
Singh M. , Chandra A. 2011 “Application of adaptive network-based fuzzy inference system for sensorless control of PMSG-based wind turbine with nonlinear-load-compensation capabilities” IEEE Trans. Power Electr. 26 (1) 165 - 175    DOI : 10.1109/TPEL.2010.2054113
Li F. , Wang X. , Chen Z. , Zhang X. , Hu Y. 2011 “A control strategy for multi-functional converter to improve grid power quality” IEEE 37th Annu. Conf. Ind. Electr. Soc. 790 - 795
Khani S. , Mohammadian L. , Hosseini S. H. 2012 “Controlling a 4-wire PV-AF system in existence of unbalanced and distorted supply voltages” 20th Iranian Conf. Electr. Eng. 473 - 478
Ma Y. , Ellinger T. , Petzoldt J. 2011 “Implementation of harmonic control for a 3-phase 4-wire inverter with harmonic-loaded neutral” 14th Europ. Conf. Power Electr. Appl. 1 - 10
Beser E. , Arifoglu B. , Camur S. , Beser E. K. 2010 “A grid-connected photovoltaic power conversion system with single-phase multilevel inverter” Solar Energy 84 (12) 2056 - 2067    DOI : 10.1016/j.solener.2010.09.011
Gajanayake C. J. , Vilathgamuwa D. M. , Loh P. C. , Teo-dorescu R. , Blaabjerg F. 2009 “Z-source-inverter-based flexible distributed generation system solution for grid power quality improvement” IEEE Trans. Energy Convers. 24 (3) 695 - 704    DOI : 10.1109/TEC.2009.2025318
Gajanayake C. J. , Vilathgamuwa D. M. , Loh P. C. , Blaabjerg F. , Teodorescu R. 2007 “A Z-source inverter based flexible DG system with p+resonance and repetitive controllers for power quality improvement of a weak grid” IEEE Conf, Power Electr. 2457 - 2463
Chen X. , Fu Q. , Infield D. G. 2009 “PV grid-connected power conditioning system with Z-source network” Int. Conf. Sust. Power Gener. Sup. 1 - 6
Sun D. , Ge B. , Bi D. , Peng F. Z. 2013 “Analysis and control of quasi-Z source inverter with battery for grid-connected PV system,” Int. Jour. Elec. Power & Energy Sys. 46 234 - 240    DOI : 10.1016/j.ijepes.2012.10.008
Shahbazi M. , Poure P. , Saadate S. , Zolghadri M. R. 2011 “Five-leg converter topology for wind energy conversion system with doubly fed induction generator” Ren. Energy 36 (11) 3187 - 3194    DOI : 10.1016/j.renene.2011.03.014
Jain S. , Jiang J. , Huang X. , Stevandic S. 2012 “Modeling of fuel-cell-based power supply system for grid interface” IEEE Trans. Indus. Appl. 48 (4) 1142 - 1153    DOI : 10.1109/TIA.2012.2199454
Dai M. , Marwali M. N. , Jung J. W. , Keyhani A. 2008 “Power flow control of a single distributed generation unit” IEEE Trans. Power Electron. 23 (1) 343 - 352    DOI : 10.1109/TPEL.2007.911815
Marei M. I. , El-Saadany E. F. , Salama M. M. A. 2012 “A flexible DG interface based on a new rls algorithm for power quality improvement” IEEE Sys. Jour. 6 (1) 68 - 75    DOI : 10.1109/JSYST.2011.2162930
Ribeiro L. A. de S. , Saavedra O. R. , Lima S.. L. , de Matos J. G. , Bonan G. 2012 “Making isolated renewable energy systems more reliable” Ren. Energy 45 221 - 231    DOI : 10.1016/j.renene.2012.02.014
Andreotti A. , Del Pizzo A. , Rizzo R. , Tricoli P. 2010 “An efficient architecture of a PV plant for ancillary service supplying” Int. Symp. Power Electr. Elec. Drives Auto. Moti. 678 - 682
Mahmood H. , Jiang J. 2012 “Modeling and control system design of a grid connected VSC considering the effect of the interface transformer type” IEEE Trans. Smart Grid 3 (1) 122 - 134    DOI : 10.1109/TSG.2011.2166412
Rajarajan R. , Aravindan P. 2012 “Maximum power extraction in grid connected DFIG using 3 level diode clamped inverter” Int. Conf. Computing, Electr. Elec. Tech. 319 - 324
Pouresmaeil E. , Bellmunt O. G. , Miracle D. M. , Jané J. B. 2011 “Multilevel converters control for renewable energy integration to the power grid” Energy 36 (2) 950 - 963    DOI : 10.1016/
Ozdemir S. , Altin N. , Sefa I. 2012 “Single stage three-level MPPT inverter for solar supplied systems,” Int. Symp. Power Electr., Elec. Drives, Auto. Moti. 103 - 108
Etxeberria A. , Vechiu I. , Camblong H. , Vinassa J.-M. 2012 “Comparison of three topologies and controls of a hybrid energy storage system for microgrids” Energy Convers. Manag. 54 (1) 113 - 121    DOI : 10.1016/j.enconman.2011.10.012
Alepuz S. , Monge S. B. , Bordonau J. , Gago J. , González D. , Balcells J. 2006 “Interfacing renewable energy sources to the utility grid using a three-level inverter” IEEE Trans. Ind. Electron. 53 (5) 1504 - 1511    DOI : 10.1109/TIE.2006.882021
Pouresmaeil E. , Miracle D. M. , Bellmunt O. G. 2012 “Control scheme of three-level NPC inverter for integration of renewable energy resources into AC grid” IEEE Sys. Jour. 6 (2) 242 - 253    DOI : 10.1109/JSYST.2011.2162922
Tsengenes G. , Adamidis G. 2011 “A multi-function grid connected PV system with three level NPC inverter and voltage oriented control” Solar Energy 85 (11) 2595 - 2610    DOI : 10.1016/j.solener.2011.07.017
Abbes M. , Belhadj J. , Bennani A. B. A. 2010 “Design and control of a direct drive wind turbine equipped with multilevel converters” Ren. Energy 35 (5) 936 - 945    DOI : 10.1016/j.renene.2009.10.021
Martı´nez J. A. , Garcı´a J. E. , Arnaltes S. 2010 “Direct power control of grid connected PV systems with three level NPC inverter” Solar Energy 84 (7) 1175 - 1186    DOI : 10.1016/j.solener.2010.03.023
Hamzaoui I. , Bouchafaa F. , Hadjammar A. 2011 “Investigation of the behavior of a three phase grid connected photovoltaic system to control active and reactive power with DPC” Energy Proc. 6 493 - 502    DOI : 10.1016/j.egypro.2011.05.057
Abbes M. , Belhadj J. 2012 “New control method of a robust NPC converter for renewable energy sources grid connection,” Electric Power Systems Res. 88 52 - 63    DOI : 10.1016/j.epsr.2012.01.018
Muyeen S. M. , Takahashi R. , Murata T. , Tamura J. 2010 “A variable speed wind turbine control strategy to meet wind farm grid code requirements” IEEE Trans. Power Syst. 25 (1) 331 - 340    DOI : 10.1109/TPWRS.2009.2030421
Arezki S. , Boudour M. 2012 “Linear enslavement of DC bus voltage of hybrid system wind-photovoltaic” Int. Symp. Envi. Frien. Ener. Appl. 664 - 669
Karmiris G. , Tsengenes G. , Adamidis G. 2012 “A multifunction control scheme for current harmonic elimination and voltage sag mitigation using a three phase three level flying capacitor inverter” Simu. Mode. Prac. Theory 24 15 - 34    DOI : 10.1016/j.simpat.2012.01.007
Tsang K. M. , Chan W. L. 2012 “27-level DC-AC inverter with single energy source” Energy Convers. Manag. 53 (1) 99 - 107
Mahendran K. 2011 “Advanced cascaded multilevel inverter for PV cell renewable energy system employing incremental conductance MPPT algorithm” Int, Conf. Recent Adv.Elec., Electr. Cont. Eng. 367 - 370
Sotoodeh P. , Tareila C. P. , Miller R. D. 2012 “A single-phase D-STATCOM inverter for distributed energy sources” North Ame. Power Symp., Cham. 1 - 6
Wanjekeche T. , Nicolae D. V. , Jimoh A. A. 2010 “Modeling and control of a cascaded NPC/H-bridge inverter with LCL filter in PV- Grid application” Conf, Proc. 334 - 339
Bojoi R. , Limongi L. R. , Roiu D. , Tenconi A. 2011 “Enhanced power quality control strategy for single-phase inverters in distributed generation systems” IEEE Trans. Power Electron. 26 (3) 798 - 806    DOI : 10.1109/TPEL.2010.2103572
Aguirre M. , Couto H. , Valla M. I. 2012 “Analysis and simulation of a hydrogen based electric system to improve power quality in distributed grids” Int. Jour. Hyd. Energy 37 (19) 14959 - 14965    DOI : 10.1016/j.ijhydene.2012.01.163
Pacas J. M. , Molina M. G. , dos Santos E. C. 2012 “Design of a robust and efficient power electronic interface for the grid integration of solar photovoltaic generation systems” Int. Jour. Hyd. Energy 37 (13) 10076 - 10082    DOI : 10.1016/j.ijhydene.2011.12.078
Akagi H. , Kanazawad Y. , Nabae A. 1984 “Instantaneous reactive power compensators comprising switching devices without energy storage components” IEEE Trans. Ind. Appl. 20 (3) 625 - 630    DOI : 10.1109/TIA.1984.4504460
Bhattacharya S. , Divan D. 1995 “Instantaneous reactive power compensators comprising switching devices without energy storage components,” in Proc. 30th Ind. Appl. Soc. Annu. Meet. Ind. Appl. Conf Oct. 8-12 2531 - 2540
Castilla M. , Miret J. , Sosa J. L. , Matas J. , Vicu˜na L. G. 2010 “Grid-fault control scheme for three-phase photovoltaic inverters with adjustable power quality characteristics” IEEE Trans. Power Electron. 25 (12) 2930 - 2940    DOI : 10.1109/TPEL.2010.2070081
Rodr´ıguez P. , Timbus A. , Teodorescu R. , Liserre M. , Blaabjerg F. 2009 “Reactive power control for improving wind turbine system behavior under grid faults” IEEE Trans..Power Electron. 24 (7) 1798 - 1801    DOI : 10.1109/TPEL.2009.2014650
Lee T. I. , Cheng P. T. 2007 “Design of a new cooperative harmonic filtering strategy for distributed generation interface converters in an islanding network” IEEE Trans. Power Electron. 22 (5) 1919 - 1927    DOI : 10.1109/TPEL.2007.904200
Jayasinghe S. D. G. , Vilathgamuwa D. M. , Madawala U. K. 2011 “Diode-clamped three-level inverter-based battery/supercapacitor direct integration scheme for renewable energy systems” IEEE Trans Power Electron. 26 (12) 3720 - 3729    DOI : 10.1109/TPEL.2011.2148178
Delghavi M. B. , Yazdani A. 2011 “An adaptive feedforward compensation for stability enhancement in droop-controlled inverter-based microgrids” IEEE Trans. Power Del. 26 (3) 1764 - 1773    DOI : 10.1109/TPWRD.2011.2119497
Karimi H. , Yazdani A. , Iravani R. 2011 “Robust control of an autonomous four-wire electronically-coupled distributed generation unit” IEEE Trans. Power Del. 26 (1) 455 - 466    DOI : 10.1109/TPWRD.2010.2064184
Altin N. , Sefa I. 2012 “dSPACE based adaptive neuro-fuzzy controller of grid interactive inverter” Energy Convers. Manag. 56 130 - 139    DOI : 10.1016/j.enconman.2011.11.017
Ilavarasi V. , Rajan C. C. A. 2012 “Power quality improvement in grid connected system using four leg VSI” IEEE Int. Conf. Adv. Eng., Sci. Man. 540 - 546
Shyam B. , Aswathy B. R. , Thomas P. C. 2011 “A novel wind energy conversion system with power quality improvement features,” Conf. Innov. Smart Grid Tech. 84 - 88
Yamauchi H. , Uchida K. , Yona A. , Senjyu T. 2012 “Intelligent operations of distribution system with distributed generators” Int. Conf. Rene. Energy Res. Appl. 1 - 6
Weiss G. , Zhong Q. C. , Green T. C. , Liang J. 2004 “H∞repetitive control of DC-AC converters in microgrids,” IEEE Trans. Power Electr. 19 (1) 219 - 230    DOI : 10.1109/TPEL.2003.820561
Luo S. , Luo An. , Lv Zhipeng , Shen Y. , Guo Lu. , Jiang Wenqian 2010 “Power quality active control research of building integrated photovoltaic” IEEE 2th Int. Symp. Power Electr. Distri.Gener. Syst. 796 - 801
Wang F. , Duarte J. L. , Hendrix M. A. M. 2011 “Grid-interfacing converter systems with enhanced voltage quality for microgrid application concept and implementation” IEEE Trans. Power Electr. 26 (12) 3501 - 3513    DOI : 10.1109/TPEL.2011.2147334
Maris T. I. , Kourtesi S. , Ekonomou L. , Fotis G. P. 2007 “Modeling of a single-phase photovoltaic inverter” Solar Energy Mater. Solar Cells 91 (18) 1713 - 1725    DOI : 10.1016/j.solmat.2007.05.027
Zeng Z. , Yang H. , Zhao R. , Cheng C. 2013 “Topologies and control strategies of multi-functional grid-connected inverters for power quality enhancement: A comprehensive review” Renewable and Sustainable Energy Reviews 24 223 - 270    DOI : 10.1016/j.rser.2013.03.033
Amin M.M.N. , Mohammed O.A. 2010 “Power quality improvement of grid-connected wind energy conversion system for optimum utilization of variable speed wind turbines” 36th IEEE Conf. Ind. Electr. Soc. 3287 - 3292
Lv Z. , Luo A. , Wu C. , Shuai Z. , Kang Z. 2009 “A research of microgrid energy supply and filtering system based on inverter multiplexing” IEEE Int. Conf. on Sust. Power Gen. Supply 1 - 7
Han B. , Bae B. , Kim H. , Baek S. 2006 “Combined operation of unified power-quality conditioner with distributed generation” IEEE Trans. Power Del. 21 (1) 330 - 338    DOI : 10.1109/TPWRD.2005.852843
Boué A. B. R. , Valverde R. G. , Vila F. A. R. , Ponce J. M. T. 2012 “An integrative approach to the design methodology for 3-phase power conditioners in photovoltaic grid-connected systems” Energy Convers. and Manag. 56 80 - 95    DOI : 10.1016/j.enconman.2011.11.012
Lim Y. S. , Tang J. H. 2014 “Experimental study on flicker emissions by photovoltaic systems on highly cloudy region: A case study in malaysia” Renewable Energy 64 61 - 70    DOI : 10.1016/j.renene.2013.10.043