Power Redistributor Applied to Distribution Transformers (original) (raw)
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This paper presents a new control strategy for parallel active filters. The instantaneous positive sequence extraction of load current and utility voltage is combined with the p q theory. This method is able to control a four leg active filter for compensation of reactive power, current harmonics, three-phase imbalance and neutral current cancellation simultaneously in 3-phase 4-wire distribution systems. The presented method can operate in harmonic polluted and/or imbalance utility voltage case. The simulation results prove the considerable ability of control strategy to suppress the above-mentioned subjects with a very fast dynamic response. This method is usable in 3-wire systems, too.
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ANALYSIS AND MITIGATION OF UNBALANCE DUE TO LOAD IN DISTRIBUTION SYSTEM BY USING ACTIVE POWER FILTER
Distribution network losses can vary significantly depending on the load unbalance. Here, an analysis of distribution system losses is presented that considers load unbalance and the effect of explicitly represented neutral wire. A general power flow algorithm for three-phase four-wire radial distribution networks, based on the current summation backward-forward technique is applied. Loss analysis results obtained from three-phase four-wire medium and low voltage test feeders with unbalanced load scenarios are presented and discussed an active power filter is designed, simulated, implemented, and tested. It can work in different modes: active power filtering, power factor correction, and load unbalance compensation. It is based on a current controlled voltage-source inverter with fixed carrier PWM. The control algorithm generates the source reference currents based on the controlled DC link voltage. The dimensioning criteria of the inductive and capacitive power components are discussed. The implementation is validated with simulated and experimental results obtained in a 5 kVA prototype.
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THREE PHASE FOUR WIRE UNIFIED POWER QUALITY CONDITIONER FOR POWER QUALITY IMPROVEMENT
This paper presents a novel structure for a three phase four-wire (3P4W) distribution system utilizing unified power quality conditioner (UPQC). The 3P4W system is realized from a three-phase three-wire system where the neutral of series transformer used in series part UPQC is considered as the fourth wire for the 3P4W system. A new control strategy to balance the unbalanced load currents is also presented in this paper. The neutral current that may flow toward transformer neutral point is compensated by using a four-leg voltage source inverter topology for shunt part. Thus, the series transformer neutral will be at virtual zero potential during all operating conditions. The simulation results based on MATLAB/Simulink are presented to show the effectiveness of the proposed UPQC-based 3P4W distribution system. Index Terms- Active power filter (APF), four-leg voltage-source inverter (VSI) structure, three-phase four-wire (3P4W) system, unified power quality conditioner (UPQC).
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