Three-phase Four-wire Power Distribution System Research Articles

Experimental Validation of Photovoltaic System with Isolated Dual Inductor dc-dc Converter for Grid-Connected Application

Abstract This article presents a double inductor–based converter for a grid-connected photovoltaic (PV) system with the utilization of the battery bank. This converter used to give continuous power to the three-phase four-wire power distribution system from the PV array. In order to increase the low magnitude of the PV array output voltage into a high dc voltage required for the three-phase dc link, the proposed system offers two boost stages. The double inductor–based converter gives power to the load in both the switched ON and OFF conditions of the chopping switch over buck, boost, and Cuk converters utilized in the PV-coordinated grid-connected applications. The operations of the proposed double inductor–based converter sustained three-phase four-wire power distribution system are analyzed and presented. The digital simulation and hardware experimental prototype results are presented to examine the performance of the presented double boost converter fed to the three-phase four-wire power distribution system.

A New Method for Dimensioning and Designing the Zero-Sequence Electromagnetic Filter Considering System Displacement Power Factor

This paper proposes an innovative method for dimensioning and designing the zero-sequence electromagnetic filter applied to three-phase four-wire distribution power systems. As premises, the optimum ratio between zero-sequence and positive-sequence impedances of the filter must be established in order to potentiate the filtering percentage of zero-sequence currents and ensure the quality of the supply system displacement power factor. The calculations are based on the sequential harmonic transmittances of the equivalent circuit reduced to the coupling point of the electromagnetic filter. To validate the proposed method, the results obtained with the application of the electromagnetic filter designed in a test system using the MATLAB software are compared to the results of the system modeled in the PSIM software.

Centralized Control of Distributed Single-Phase Inverters Arbitrarily Connected to Three-Phase Four-Wire Microgrids

This paper proposes an effective technique to control the power flow among different phases of a three-phase four-wire distribution power system by means of single-phase converters arbitrarily connected among the phases. The aim is to enhance the power quality at the point-of-common-coupling of a microgrid, improve voltage profile through the lines, and reduce the overall distribution losses. The technique is based on a master/slave organization where the distributed single-phase converters act as slave units driven by a centralized master controller. Active, reactive, and unbalance power terms are processed by the master controller and shared proportionally among distributed energy resources to achieve the compensation target at the point-of-common-coupling. The proposed control technique is evaluated in simulation considering the model of a real urban power distribution grid under non-sinusoidal and asymmetrical voltage conditions. The main results, concerning both steady-state and transient conditions, are finally reported and discussed.

A New Hybrid Power Conditioner for Suppressing Harmonics and Neutral-Line Current in Three-Phase Four-Wire Distribution Power Systems

In this paper, a new hybrid power conditioner is proposed for suppressing harmonic currents and neutral-line current in three-phase four-wire distribution power systems. The proposed hybrid power conditioner is composed of a neutral-line current attenuator and a hybrid power filter. The hybrid power filter, configured by a three-phase power converter and a three-phase tuned power filter, is utilized to filter the nonzero-sequence harmonic currents in the three-phase four-wire distribution power system. The three-phase power converter is connected to the inductors of the three-phase tuned power filter in parallel, and its power rating can thus be reduced effectively. The tuned frequency of the three-phase tuned power filter is set at the fifth harmonic frequency. The neutral-line current suppressor is connected between the power capacitors of the three-phase tuned power filter and the neutral line to suppress the neutral-line current in the three-phase four-wire distribution power system. With the major fundamental voltage of the utility dropping across the power capacitors of the three-phase tuned power filter, the power rating of the neutral-line current suppressor can thus be reduced. Hence, the proposed hybrid power conditioner can effectively reduce the power rating of passive and active elements. A hardware prototype is developed to verify the performance of the proposed hybrid power conditioner. Experimental results show that the proposed hybrid power conditioner achieves expected performance.

Design and Performance of an Adaptive Low-DC-Voltage-Controlled LC-Hybrid Active Power Filter With a Neutral Inductor in Three-Phase Four-Wire Power Systems

This paper proposes an adaptive low-dc-link-voltage-controlled LC coupling hybrid active power filter ( LC-HAPF) with a neutral inductor, which can compensate both dynamic reactive power and current harmonics in three-phase four-wire distribution power systems. Due to its adaptive low-dc-link-voltage characteristic, it can obtain the least switching loss and switching noise and the best compensating performances, compared with the conventional fixed and newly adaptive dc-voltage-controlled LC-HAPFs. The design procedures of the dc-link voltage controller are discussed, so that the proportional and integral gains can be designed accordingly. Moreover, the general design procedures for the adaptive dc-voltage-controlled LC-HAPF with a neutral inductor are also given. The validity and effectiveness of the adaptive dc-link voltage-controlled LC -HAPF with a neutral inductor are confirmed by experimental results obtained from a 220-V 10-kVA laboratory prototype compared with the conventional fixed and adaptive dc-link voltage-controlled LC-HAPFs without a neutral inductor.

Three-phase four-wire hybrid power filter using a smaller power converter

In this paper, a hybrid power filter is proposed to solve problems of line harmonic currents and neutral line currents of three-phase four-wire power distribution system. This hybrid power filter is configured by a there-phase tuned power filter and a three-phase power converter. The tuned power filter is configured by a capacitor and an inductor, and its tuned frequency is setting at the frequency of third-order harmonics. The three-phase power converter has a four legs bridge structure and is connected to the inductor of the tuned power filter in parallel. The three-phase power converter is applied to solve the problems of series/parallel resonance and improve poor filter performance. Furthermore, it also forces the fundamental current of the tuned power filter and the dominant harmonic current of the nonlinear load to flow through the inductor of the tuned power filter. In this way, the voltage rating of the three-phase power converter is reduced because it is serially connected to the power capacitor of the tuned power filter, and the current rating can be diminished because it is connected to the inductor of the tuned power filter in parallel. Hence, the power rating of the power converter applied in the proposed hybrid power filter is minimized. A DSP based prototype is developed and tested to verify the performance of the proposed three-phase four-wire hybrid power filter. Experimental results show that the proposed three-phase four-wire hybrid power filter achieves the expected performance.

Single-phase inverter-based neutral-current suppressor for attenuating neutral current of three-phase four-wire distribution power system

In this study, a neutral-current suppressor is proposed. The proposed neutral-current suppressor comprises a zero-sequence transformer, a single-phase power converter and a rectifier. The proposed zero-sequence transformer is implemented by only two single-phase transformers, which are connected to three-phase lines of the three-phase four-wire distribution power system to supply a zero-sequence current path. The single-phase power converter is connected between the zero-sequence transformer and neutral line. A rectifier with small power rating is connected to the DC bus of single-phase power converter for overcoming the power loss of single-phase power converter to sustain a constant DC voltage. The performance of neutral-current suppression for the zero-sequence transformer is advanced by controlling the single-phase power converter so as to make the neutral load current flow through the proposed neutral-current suppressor. Moreover, the proposed neutral-current suppressor can also avoid the neutral current caused by the unbalanced voltage of three-phase four-wire distribution power systems. Hence, the proposed neutral-current suppressor is an effective solution to the neutral-current problem of three-phase four-wire distribution power systems. Both computer simulation and experimental results verify that the proposed neutral-current suppressor can achieve the expected performance.

Star-hexagon transformer and non-isolated three-leg VSC based three-phase four-wire DSTATCOM

A new three-phase four-wire DSTATCOM (distribution static compensator) is proposed for power quality improvement in the distribution system. The DSTATCOM is based on a star/hexagon transformer and three-leg VSC (voltage source converter). It compensates harmonic current, reactive power and balances the load along with neutral current compensation. Each of the three single phase transformers has three windings and the secondary windings are connected in star/hexagon configuration for interfacing to a three-phase four-wire power distribution system. The IGBT (insulated gate bipolar transistor) based VSC is a capacitor supported and it is controlled for the required compensation of load currents. The DC bus voltage of the VSC is regulated even during dynamic load variations. The DSTATCOM is tested for power factor correction and voltage regulation along with neutral current compensation, harmonic elimination and load balancing under linear loads as well as non-linear loads. The performance of the three-phase four-wire DSTATCOM is validated using MATLAB software with its Simulink and SimPower System (SPS) tool boxes.

A T-Connected Transformer and Three-leg VSC Based DSTATCOM for Power Quality Improvement

In this paper, a new three-phase four-wire distribution static compensator (DSTATCOM) based on a T-connected transformer and a three-leg voltage source converter (VSC) is proposed for power quality improvement. The T-connected transformer connection mitigates the neutral current and the three-leg VSC compensates harmonic current, reactive power, and balances the load. Two single-phase transformers are connected in T-configuration for interfacing to a three-phase four-wire power distribution system and the required rating of the VSC is reduced. The insulated gate bipolar transistor (IGBT) based VSC is supported by a capacitor and is controlled for the required compensation of the load current. The DC bus voltage of the VSC is regulated during varying load conditions. The DSTATCOM is tested for power factor correction and voltage regulation along with neutral current compensation, harmonic elimination, and balancing of linear loads as well as nonlinear loads. The performance of the three-phase four-wire DSTATCOM is validated using MATLAB software with its Simulink and power system blockset toolboxes.

Analysis of Zig-Zag Transformer Applying in the Three-Phase Four-Wire Distribution Power System

The load unbalance and the nonlinear loads result in a significant neutral current in the three-phase four-wire distribution power system. The Zig-Zag transformer has been proposed to attenuate the neutral current of the three-phase four-wire distribution power system. In this paper, an analysis is carried out and computer simulation is used to evaluate the performance of the Zig-Zag transformer under ideal and nonideal power conditions. The simulation results show that (a) the Zig-Zag transformer can effectively attenuate the neutral current and zero-sequence harmonic currents on the utility side under the balanced utility voltage, (b) the utility side neutral current becomes larger under the unbalanced utility voltage or the distorted utility voltage with zero sequence harmonic components after applying the Zig-Zag transformer, (c) the insertion of an inductor in the utility side of the neutral conductor can alleviate overloading of the neutral current caused by the unbalanced utility voltages and the distorted utility voltages with zero sequence harmonic components.

Mitigation of third‐harmonic voltage for three‐phase four‐wire distribution system based on a series active filter for neutral conductor

AbstractThis paper proposes a series active filter for mitigation of the third‐harmonic voltage in a three‐phase four‐wire power distribution system in a building. The active filter which consists of a single‐phase inverter can suppress the harmonic voltage of the system. The active filter is characterized by acting not only as a capacitor but also as a resistor for the third‐harmonic components. A Hilbert transformer is applied to the controller of the active filter in order to realize accurate third‐harmonic detection on a single‐phase active filter. Measurement results of harmonic distortion of source voltage in a building is also shown in this paper. It is clarified in a simulation and experiment that the active filter can suppress the third‐harmonic voltage without increasing neutral conductor current. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 150(1): 62–70, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.10379