This paper presents distributed power quality conditioning system to compensate current and voltage distortions in three-phase four-wire networks caused by unbalanced non-linear single-phase loads. The proposed conditioning system consists of several hybrid filter units installed in various nodes for compensation of excessive neutral currents and voltage distortions in a selected area of the distribution network. The system is open and it can be easily modified by installation of new filter units. A novel hybrid filter design procedure based on filter frequency characteristics optimization in the parameters of passive and active parts is presented. A digital system of control signal computation for active filters based on the use of modern methods of spectral analysis is considered. The proposed digital control system enables selective compensation of fundamental and harmonic components. The mathematical model of the proposed power quality conditioning system is developed in the MatLab software. The simulated results show that the presented conditioning system reduces the level of neutral conductor currents and the voltage unbalance as well ensures harmonic compensation in three-phase four-wire networks.

The article considers a hybrid power quality conditioner (HQPC) for 3-phase 4-wire systems with a distributed modular structure. Some conditioner modules provide compensation for the component currents and voltages that form the negative and zero sequence systems. The open structure of the HQPC, consisting of independent modules, allows compensating for distortions of currents and voltages of the 3-phase network caused by the nonlinear nature and asymmetry of single-phase loads. The compensation characteristics of the proposed conditioner were researched using a model developed in the MatLab environment. The simulation showed that the proposed conditioner can ensure normalization of power quality in 3-phase 4-wire system at various modes of network operation.

Load unbalance and modern office equipment result in a significant neutral current in three-

Abstract. This paper describes a distributed power quality (PQ) monitoring system. The structure of the measurement system, format of PQ database and web-server software are being discussed. The developed software can be used for PQ analysis and research activities. Examples of harmonic pollution measurements are being displayed.

Основной причиной увеличения токов нейтральных проводников в трехфазных четырехпроводных сетях низкого напряжения являются современное офисное оборудование и несимметрия нагрузок. В статье рассмотрена новая конфигурация гибридного широкополосного фильтра для управления качеством электроэнергии в трехфазных четырехпроводных сетях. Предложенный фильтр образован последовательным соединением пассивного широкополосного фильтра и однофазного инвертора. Фильтр может работать как в пассивном, так и в гибридном режиме. Компенсационные характеристики предложенного фильтра проанализированы с помощью моделирования в среде MATLAB. Анализ показал, что предложенный гибридный фильтр является эффективным средством ослабления токов нейтральных проводников. Ключевые слова: трехфазная четырехпроводная сеть, гибридный силовой фильтр, ток нейтрального провода.