Abstract
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.
Highlights
In recent years the power quality (PQ) problems in low voltage three-phase four-wire networks have gained great importance due to massive penetration of single-phase non-linear loads such as energy-saving lighting systems, office and computer equipment and variable speed motor drives in small air conditioners.Unlike the three-phase loads of powerful industrial consumers the typical loads of office and commercial consumers are single-phase devices
This paper presents the distributed PQ conditioning system for three-phase four-wire networks
The system consists of several hybrid filter units, providing compensation of excessive neutral currents and voltage distortions in selected areas of distribution network
Summary
In recent years the power quality (PQ) problems in low voltage three-phase four-wire networks have gained great importance due to massive penetration of single-phase non-linear loads such as energy-saving lighting systems, office and computer equipment and variable speed motor drives in small air conditioners. Passive and hybrid compensation devices for three-phase four-wire systems implemented on the basis of Zigzag transformers are considered in [9,10,11,12] Such devices can effectively mitigate the neutral-line current. A more cost-effective version of PQ conditioner for three-phase four-wire networks is proposed in [15] It consists of two hybrid power filters that provide compensation of neutral-line current and nonzero-sequence components. Power quality conditioners, discussed in [13,14,15] are used to solve issues, caused by asymmetric load, harmonic distortions, neutral conductors overloading These devices are designed to control the power quality in separate nodes of the network a concentrated non-linear load is connected to.
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