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As a technique to control the voltage drop at network peak periods and voltage rise at middays when a high number of rooftop photovoltaic systems exist in a low-voltage feeder (LVF), two or more neighboring LVFs can be coupled. To add voltage controllability to the coupling point, a distribution static compensator (DSTATCOM) can be installed. An important issue for such a system is its operation under short-circuit conditions in one of the LVFs and relevant protection aspects. This paper investigates the performance of such a system under fault conditions and presents a protection scheme that can achieve the desired operation of the system, under short-circuit faults in either of the LVFs. The performance of the system of coupled LVFs is investigated by numerical analysis in MATLAB while the dynamic feasibility of the proposed technique is validated by simulation studies in PSCAD/EMTDC. [ABSTRACT FROM AUTHOR]

This research study explains the design and performance of a Static VAR Compensator (SVC) coupled Hybrid Distribution Static Compensator (DSTATCOM) for low voltage power distribution system (PDS). A comparative analysisis done between Voltage Source Inverter (VSI)-based DSTATCOM and SVC Hybrid DSTATCOM using Jordan Least Mean Square (JLMS) algorithm to alleviate the shunt-related power quality (PQ) glitches. The specific design is obtained as compared to the existing neural network toolbox algorithm to improve the estimation speed and accuracy. The main objective is to extract the tuned weighted values of fundamental active and reactive power components of distorted load currents for the switching signal generation using an adaptive JLMS algorithm.Several functions of DSTATCOM and hybrid DSTATCOM using this JLMS controller are showcased for harmonics curtailment, power factor (p.f.) improvement, load balancing, voltage regulation, etc. Simulation results on an SVC Hybrid DSTATCOM have shown an acceptable level of performance under unbalanced loading situations. Finally, some comparative results are provided to validate the feasibility and effectiveness of the suggested topology. [ABSTRACT FROM AUTHOR]

Summary: The objective of this article is to compensate the deviations in magnitude and phase shift of load terminal voltage in an unbalanced low‐voltage distribution system. In specific, power balancing at the load terminal is accomplished through a compensator. A separate single‐phase full bridge voltage source converter (VSC) is employed in each phase to mitigate the system unbalance. The desired active and reactive power exchange of VSC with the system is accomplished with a simplified control methodology that considers terminal magnitude and angle measurements. The performance of the proposed method is compared with well established d‐q–based control methodology. The functionality of the compensator and its applicability is verified through a detailed case study. [ABSTRACT FROM AUTHOR]

Copyright of Revista Técnica Energía is the property of Centro Nacional de Control de Energia CENACE and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper presents a Distribution Static Compensator (DSTATCOM) that uses a traditional Synchronous Reference Frame (SRF) to make source current in phase and sinusoidal shape w.r.t source voltage, so that unity power factor is achieved at source side. In addition to this, a new concept of single phase synchronous d-q reference frame theory is used for generation of reference signals in a three phase distribution system for compensation of voltage unbalances at the load side. Further, this paper uses a traditional hysteresis controller for generation of switching signals for the Voltage Source Converter (VSC). Moreover, switching of DSTATCOM between Current Controlled Mode(CCM) and Voltage Controlled Mode(VCM) is carried out so that only single DSTATCOM serves the problem for current and voltage related Power Quality problems. Simulations are carried out in MATLAB/Simulink environment to validate the proposed scheme and results indicate that the unity power factor is achieved during CCM mode and voltages in all the three phases at PCC are maintained at 1 p.u. during VCM mode. [ABSTRACT FROM AUTHOR]

This paper deals with a control design based on amplitude adaptive notch filter (AANF) for a four-leg distributed static compensator (DSTATCOM) in a three-phase four-wire distribution grid to overcome current-related problems of power quality. Extracted reference currents of DSTATCOM are obtained using AANF because of its simple structure, exact measuring of frequency and amplitude, suitable estimation of the desired signal, and capability of tracking the changes of the input signal amplitude. To improve the dynamic performance of DSTATCOM, two fuzzy logic controllers are utilized to regulate DC link voltage and the voltage of point of common coupling (PCC). Furthermore, an adaptive hysteresis band current controller is applied for generating the gate pulses of IGBT switches. The proposed control scheme is robust to power system oscillations, especially when the main voltage suffers from disturbances and unbalancing. Different surveys are performed to study the efficacy of the proposed method, and results are verified through the simulation results in MATLAB/Simulink environment. [ABSTRACT FROM AUTHOR]

In this article, a single-phase Distribution Static Compensator (DSTATCOM) with reduced dc-link voltage is proposed for power quality improvement in a distribution system. Generally, the dc-link voltage of DSTATCOM is maintained twice the peak of Point of Common Coupling (PCC) voltage by voltage regulation loop. But, the dc-link voltage is maintained itself without voltage regulation loop in the proposed method. For this case, the required dc-link voltage magnitude is less when compared to conventional method. Under predefined load conditions such as agriculture pump set loads, this less voltage is sufficient to give satisfactory performance. Therefore, the rating of DSTATCOM is reduced and thereby the cost of system is reduced. The proposed method enables compensation of reactive power and mitigation of source current harmonics in a distribution system for low power applications. The advantages of the proposed method are elimination of dc voltage sensing elements, minimization of switching loss of Voltage Source Inverter (VSI) and cost effective. The proposed single-phase DSTATCOM performance is demonstrated through MATLAB/simulink and validated by experimental results with agriculture pump set load. [ABSTRACT FROM AUTHOR]

Solving voltage regulation in underrated grid networks can be very time consuming and costly for operators and unpleasant for customer, who constantly experience equipment malfunctions due poor voltage quality. Active solutions such as Multifunctional Voltage-Quality Regulator (MVQR) work well as a quick fix in these cases, bringing voltages to the right levels as soon as installed, feeding active or reactive power into their point of connection. Unfortunately, current solutions can be fastidious, adjusting voltage levels that are already adequate for customer services to a specific fixed setpoint, unnecessarily spending energy, overusing distribution networks, wearing out energy-storage components and eventually not optimizing the equipment’s regulation capacity. To address the aforementioned problems, this manuscript proposes a control scheme to reduce the reactive power processed in an existing MVQR. The MVQR was based in a distribution static compensator (DSTATCOM) with active harmonic filtering feature. Where voltage-magnitude regulation is achieved by reactive power injection only, while harmonic mitigation is performed by harmonic injection based on PCC-voltage-detection-method (PCC-VDM). The proposed MVQR control scheme reduces the reactive energy injection when the voltage level at PCC is within limits of relevant standards. The main contribution of this paper is the detailed mathematic analysis of the scheme for reducting the reactive energy injection, which had not been found in literature. This analysis shows how to design this scheme to obtain better regulation, guarantee dynamic decoupling from other control loops, as well as ensure closed-loop system stability. Simulation and experimental results were carried out for validation of the proposed control method. The proposed MVQR had shown itself an efficient and effective addition, reducing significant processed reactive power using wisely resources, likely available in similar MVQR topologies. [ABSTRACT FROM AUTHOR]

The power quality compensator chosen in this paper is a DSTATCOM which integrates a three phase four leg Voltage Source Converter (VSC) with a DC capacitor. The major role of the DSTATCOM is to mitigate the components of harmonic/reactive current present in the line current thereby shapes the grid current to be sinusoidal and improves the power factor nearly unity under varying conditions. In addition DSATATCOM mitigates neutral current (Isn) and balances the load currents under unbalanced conditions in three phase four wire (3P4W) distribution system. The control strategy proposed for the DSTATCOM is a Neural Network (NN) based p-q-r theory with two Artificial Neural Network (ANN) controllers for a 3P4W distribution system. The reference signal for 3P3W Shunt Active Power Filter (SAPF) is calculated by implementing an ANN controller. The alleviation of Isn under unbalanced condition is achieved by another ANN controller which produces reference signal for the 1Φ APF. The performance of the proposed DSTATCOM is analysed for various conditions through simulations in MATLAB SIMULINK and the simulation results justify the effectiveness of the propounded NN based control algorithm for DSTATCOM. [ABSTRACT FROM AUTHOR]

In electrical systems the most critical disturbance is the interruption of the power service. However, the main concern for many commercial and industrial users is the mal-operation produced by voltage sags. This paper presents a study about the performance of a distribution system in presence of voltage sags using a distribution generation (DG) unit and a distribution static compensator (DSTATCOM). The analysis is performed by using a method for stochastic generation of disturbances and the ATP/EMTP software tool. Several case studies using the IEEE-13, bus test feeder taking to account different DG locations and penetration levels for DG unit are presented. In addition, the relation between the injected DSTATCOM reactive power, the type of sag and the location of affected nodes is considered. Simulations show that for IEEE-13 system the DSTATCOM is the best alternative for sags mitigation at a specific point in the system. However, the DG unit is an alternative that can be considered in larger distribution systems to reduce the effects of voltage sags. [ABSTRACT FROM AUTHOR]

This paper presents the control of a self-excited Induction Generator using DSTATCOM. The performance of the DSTATCOM depends on the extraction of the reference source currents. For this purpose, the control strategy adopted is IRP theory, which is implemented using MATLAB/Simulink. Generation of the PWM pulses triggers the IGBT of the VSI based DSTATCOM. This is achieved using Arduino Due, a 32 bit ARM core microcontroller interfaced with MATLAB/Simulink. The performance of the SEIG is analyzed experimentally in a hardware prototype to evaluate the effect of DSTATCOM. It is observed that SEIG with DSTATCOM provides voltage sag mitigation, reactive power compensation, and power factor improvement. [ABSTRACT FROM AUTHOR]

Voltage sags are the most common power quality disturbances in electrical facilities. It may cause malfunction in sensitive equipment and process interruption. The distribution static compensator (DSTATCOM) is a device that can compensate voltage sags by injecting reactive power into distribution systems. This paper shows the influence on voltage sags characteristics by the presence of twelve-pulse DSTATCOM in the modified IEEE-13 distribution system. The analysis is performed by means of a random generation of disturbances using a MATLAB routine to identify the critical buses of the test system. Further, the DSTATCOM model taking advantage of the available elements from ATP/EMTP software is described. Simulations show that when DSTATCOM is placed directly to an affected bus it is possible to obtain a complete mitigation of the voltage sag. Finally, the relation between the reactive power injected by DSTATCOM, the type of voltage sag and the location of the affected bus is considered. [ABSTRACT FROM AUTHOR]

In this paper the choice of power quality compensator is a DSTATCOM which constitutes a four leg voltage source converter (VSC) and a DC capacitor. An artificial neural network (ANN) based synchronous reference frame (SRF) theory is proposed for the generation of gating pulse of the DSTATCOM to balance the source current, eliminate harmonics and to compensate neutral current and reactive power in three phase four wire (3PAW) distribution system. In the proposed control strategy ANN controllers replace the PI controllers and low pass filters of conventional method. ANN controllers are also implemented to keep up the voltage across the capacitor and as a compensator to compensate neutral current under unbalanced load conditions. Various transformer topologies are simulated and compared with the proposed control strategy for compensation of neutral current. The DSTATCOM performance is adjudged under balanced, unbalanced and/or distorted voltage source conditions through simulation using MATLAB software. Data extracted from the experiment conducted in the laboratory to study the effect of non-linear load are used in the simulation to prove the efficacy of the proposed control strategy in power quality improvement. [ABSTRACT FROM AUTHOR]

This paper presents implementation of distribution static compensator (DSTATCOM) using kernel incremental metalearning algorithm (KIMEL) control algorithm. It demonstrates the functions of DSTATCOM such as reactive power compensation, harmonics elimination, and load balancing under linear and nonlinear loads with its self-supporting dc-bus voltage. The proposed control algorithm based on KIMEL is applied for extraction of fundamental active and reactive power components of load currents that are required for estimation of reference supply currents. These reference supply currents are used for gating pulses generation using indirect current control principle. A DSTATCOM with features of self-supporting dc bus (capacitor) is developed using DSP (dSPACE-1104), and the response of proposed control algorithm is studied under various operating conditions and found satisfactory. [ABSTRACT FROM AUTHOR]

Highlights: [•] Immune algorithm (IA) is used for optimal DSTATCOM placement and sizing. [•] Proposed methods were performed on two IEEE test systems (33 and 69 bus). [•] Simulation confirmed effectiveness of proposed IA method over GA in minimizing OF. [Copyright &y& Elsevier]

This paper proposes a modified four-leg distribution static compensator (DSTATCOM) topology for compensation of unbalanced and nonlinear loads in three-phase four-wire distribution system. DSTATCOM, connected in parallel to the load, supplies reactive and harmonic powers demanded by unbalanced nonlinear loads. In this proposed topology, the voltage source inverter (VSI) of DSTATCOM is connected to point of common coupling (point of interconnection of source, load, DSTATCOM) through interface inductor and series capacitance, unlike the conventional topology which consists of interface inductor alone. Load compensation with a lower value of input DC link voltage of VSI is possible in this modified topology compared to conventional topology. A comparative study on modified and conventional topologies in terms of voltage rating of inverter power switches, switching losses in VSI and power rating of input DC capacitor of VSI is presented. The detailed design aspects of DC link capacitor and interface series capacitor are also presented. The reference filter currents are generated using instantaneous symmetrical component theory and are tracked using hysteresis current control technique. A detailed simulation study is carried out, to compare the compensation performances of conventional, modified topologies using PSCAD simulator and experimental studies are done to validate the simulation results. [ABSTRACT FROM AUTHOR]

Highlights: [•] Studying voltage unbalance in low voltage feeders with distributed single-phase PVs. [•] Proposing new converter control for DSTATCOM & DVR to reduce voltage unbalance. [•] Conducting Monte Carlo based stochastic analysis to investigate efficacy of proposed methods. [•] Proving the dynamic feasibility of the proposed method and control algorithms. [Copyright &y& Elsevier]

The power balancing mechanism and the effective voltage balancing control algorithm are presented for the single-phase cascaded H-bridge multilevel DSTATCOM. The dc voltage balancing control for CHB-DSTATCOM is splitted into the average voltage controller and the voltage balancing controller, which are designed to regulate the active power flow between the CHB-DSTATCOM with the grid and to regulate active power flow among each inverter units, respectively. The effectiveness of the control algorithm is validated by the simulation results. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents comparison of three different control strategies to generate reference current components for Distribution Static Compensator (DSTATCOM). Reference currents are tracked by a three-phase voltage source converter in a hysteresis band control scheme. These methods are instantaneous reactive power (IRP) theory, symmetrical component (SC) theory and an improved instantaneous active and reactive current component (IARCC) theory. The performance of three methods has been evaluated under various source voltage and load conditions with new IEEE Standard 1459 power definitions. A comparative study of their performance in terms of rms value of source current, Total Harmonic Distortion (THD), supply power factor and compensator ratings is also presented. A three-phase, four-wire distribution system supplying linear as well as non-linear load is considered for simulation study which is carried out using MATLAB/SIMULINK software. Under balanced and sinusoidal source voltage conditions, all three control strategies similar performance while an improved IARCC theory outperforms, particularly, under unbalanced and distorted source voltage conditions. [Copyright &y& Elsevier]

Abstract: This paper deals with a Distribution STATic COMpensator (DSTATCOM) for balancing of source currents, power factor correction and harmonic mitigation in three-phase, three-wire distribution system supplying delta connected load under various source voltage conditions. The control strategy applied to the DSTATCOM play a major role in its performance. A novel approach based on an improved instantaneous active and reactive current component (IARCC) theory is proposed for generation of three-phase reference currents for DSTATCOM. A three-phase voltage source converter with a dc bus capacitor is employed as DSTACOM which will track the reference currents in a hysteresis band scheme. The performance of DSTATCOM is evaluated under sinusoidal, unbalanced sinusoidal and unbalanced distorted source voltage conditions. Variation in load current, variation in magnitude and harmonic content in source voltage has been considered. Delta connected linear as well as non-linear load conditions have been considered. The performance of the DSTATCOM using the proposed control strategy is demonstrated using simulation results in MATLAB/SIMULINK software. Simulation results demonstrate the feasibility of proposed scheme for the control of DSTACOM. [Copyright &y& Elsevier]

A Distribution STATCOM (DSTATCOM) is a shunt compensation device used for reactive power compensation. It can be used either in the power factor correction mode or in the voltage regulation mode. In this paper, a vector based hysteresis current controller (HCC) for DSTATCOM, operated in the power factor correction mode, is implemented. The control law is derived based on generalized instantaneous reactive power theory. The controller uses errors in current represented in stationary a-β frame, multi-level hysteresis comparators and an associated lookup table to produce a switching pattern, which restricts the errors in currents to lie within a region. Extensive use of zero vectors has been made to reduce the switching frequency and switching losses. The control technique implemented does not require phase locked loop (PLL) to track the line frequency. The use of HCC makes the system robust, and hence independent of load parameter variation, with fast transient response. The performance of vector based HCC is studied in MATLAB/SIMULINK environment and results obtained are satisfactory. [ABSTRACT FROM AUTHOR]

This paper presents the application of distribution static compensator (DSTATCOM) for mitigating the frequently occurring problems of voltage dips in autonomous systems. Consumer loads are experiencing proliferation of induction motors. The starting of induction motors draws large current causing voltage sag (dip). Autonomous Power system is comparatively less stiff than the grid connected system. Large starting current, causing objectionable voltage drop, is critical for an autonomous system. DSTATCOM has been effectively used to redeem this power quality problem. An asynchronous generator with a motor load having a DSTATCOM connected in shunt is simulated on a MATLAB platform using Simulink and Power System Block set. The simulation establishes the capability of DSTATCOM to mitigate the voltage dip problem for an autonomous system. [ABSTRACT FROM AUTHOR]

In this paper, a combination of two techniques for improving bus voltage magnitudes during voltage sag is presented. Initially network reconfiguration is applied to the exposed weak area in distribution systems. Then to further mitigate the voltage sag, DSTATCOM placement is considered as a second approach. Gravitational Search Algorithm (GSA) is considered as new heuristic optimization algorithm. It is used for finding the optimal solution in both proposed techniques. Suitable encoding methods are used to establish DSTATCOM location and to maintain radial structure of distribution network respectively. The simulation results show that the proposed method is efficient and feasible for improving the bus voltage profile during voltage sag considering the benefits obtained from the reduction of the financial losses by the load outages due to voltage sag problems. The proposed method may assist the utility engineers in taking the right decision for network reconfiguration and voltage sag mitigation. [ABSTRACT FROM AUTHOR]

Abstract: The main idea in distribution network reconfiguration is usually to reduce loss by changing the status of sectionalizing switches and determining appropriate tie switches. Recently Distribution FACTS (DFACTS) devices such as DSTATCOM also have been planned for loss reduction and voltage profile improvement in steady state conditions. This paper implements a combinatorial process based on reconfiguration and DSTATCOM allocation in order to mitigate losses and improve voltage profile in power distribution networks. The distribution system tie switches, DSTATCOM location and size have been optimally determined to obtain an appropriate operational condition. Differential evolution algorithm (DEA) has been used to solve and overcome the complicity of this combinatorial nonlinear optimization problem. To validate the accuracy of results a comparison with particle swarm optimization (PSO) has been made. Simulations have been applied on 69 and 83 busses distribution test systems. All optimization results show the effectiveness of the combinatorial approach in loss reduction and voltage profile improvement. [Copyright &y& Elsevier]

The proposed distribution static compensator is used to compensate the reactive power for power factor correction or voltage regulation along with load balancing, neutral current compensation, and harmonics current elimination. A zig-zag/star transformer is used to isolate the voltage source converter, and it is operated as a three-phase four-wire distribution static compensator for power quality improvement in a three-phase four-wire system. In order to reduce the current rating of the voltage source converter, the zig-zag configuration is used in the primary windings of the transformer. The voltage source converter is connected to the secondary windings of the zig-zag/star transformer, and this allows the optimum selection of voltage rating of the voltage source converter. Moreover, this transformer connection provides isolation for the voltage source converter system. The distribution static compensator is implemented using the dSPACE DS1104 R&D controller (dSPACE Inc., Wixom, Michigan, USA) and a slave digital signal processor subsystem based on the TMS320F240 digital signal processor (dSPACE Inc., Wixom, Michigan, USA) to validate the design and the developed control algorithm. [ABSTRACT FROM AUTHOR]

Copyright of Automatika: Journal for Control, Measurement, Electronics, Computing & Communications is the property of Taylor & Francis Ltd and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper proposes a method for enhancing stability of an autonomous microgrid with distribution static compensator (DSTATCOM) and power sharing with multiple distributed generators (DG). It is assumed that all the DGs are connected through voltage source converter (VSC) and all connected loads are passive, making the microgrid totally inertia less. The VSCs are controlled by either state feedback or current feedback mode to achieve desired voltage-current or power outputs, respectively. A modified angle droop is used for DG voltage reference generation. Power sharing ratio of the proposed droop control is established through derivation and verified by simulation results. A DSTATCOM is connected in the microgrid to provide ride through capability during power imbalance in the microgrid, thereby enhancing the system stability. This is established through extensive simulation studies using PSCAD. [ABSTRACT FROM AUTHOR]

This paper presents a study about of a fuzzy Controlled STATCOM, which can be applied for mitigation of the voltage flicker in a distribution system. The voltage flicker is produced by a large variable load absorbing continuously changing currents such as an arc furnace. The DSTATCOM includes a voltage-sourced PWM inverter and its control system. The control strategy of the DSTATCOM plays an important role in maintaining the voltage flicker. Here, the DSTATCOM controller is designed with two types of controllers, linear proportional-integral (PI) and nonlinear fuzzy logic. The simulation of the DSTATCOM with 3MVar reactive power on a 25 KV distribution network is carried out in MATLAB/SIMULINK software. At the end of the paper, fuzzy controllers were evaluated by comparing its performance with the PI controllers. It is observed that the fuzzy controllers are very superior in mitigating the voltage flicker. [ABSTRACT FROM AUTHOR]

A new topology of DSTATCOM (distribution static compensator) is proposed for power quality improvement in three-phase four-wire distribution systems. A three-leg VSC (Voltage Source Converter) is integrated with a star/hexagon transformer for the compensation of reactive power for voltage regulation or for power factor correction along with load balancing, elimination of harmonics currents and neutral current compensation. The star/hexagon connected transformer provides a path to the zero sequence current in a three-phase four-wire distribution system. In order to optimize the voltage rating of the VSC, the star/hexagon transformer is designed to have a suitable voltage rating for the secondary windings for integrating the three-leg VSC. This transformer connection provides the selection of 'off the shelf' VSC for this application and it also provides isolation for the VSC system. The performance of the proposed DSTATCOM system is validated through simulations using MATLAB software with its Simulink and Power System Block set (PSB) toolboxes. [ABSTRACT FROM AUTHOR]

This paper introduces a novel method for the mitigation of the voltage sag and voltage flicker by using Kalman filter and its derivatives (adaptive, and extended). The Kalman filter is used as a tool to extract both the instantaneous envelope of the voltage sags, and to extract the Instantaneous Flicker Level (IFL) of the voltage flicker. Also, this paper demonstrates the advantages of using the Kalman filter instead of the existing tools for tracking and extracting voltage disturbances. Digital simulation results are presented to illustrate the mitigation of unbalanced voltage sags, and the compensation of the cyclic and noncyclic voltage flicker by employing the proposed algorithm. [ABSTRACT FROM PUBLISHER]

• Unbalanced voltage compensation strategy. • Unbalaced voltage assessment responsability. • Distribution Static Synchronous Compensator. • Control algorithm for Static Synchronous Compensator. This paper presents a control algorithm, based on consumer-generated voltage imbalance assessment, for a distribution static synchronous compensator (DSTATCOM). The proposed algorithm quantifies, in the time-domain, the parcels of voltage unbalance due to the supplier (utility) and consumer using measurements of the instantaneous voltages and currents at the point of common coupling. Small-signals models are derived and used to design the controllers for the DSTATCOM in order to compensate for the negative and zero sequence voltages caused by the consumer. These controllers are designed in the synchronous reference frame, with two inner current loops and two outer voltage loops for each compensated sequence, to ensure the DSTATCOM tracks the reference voltages generated by the unbalance assessment algorithm. Digital simulation results obtained with an unbalanced distribution network are used to validate the proposed methodology. Through the comparison of the results obtained with and without the proposed unbalance assessment algorithm it is possible to conclude that the capacity of the compensator can be significantly reduced when only the unbalanced voltage parcel caused by the load is compensated. [ABSTRACT FROM AUTHOR]