A Voltage Regulator for Power Quality Improvement in Low-Voltage Distribution Grids

Abstract

This paper presents a voltage-controlled DSTATCOM-based voltage regulator for low voltage distribution grids. The voltage regulator is designed to temporarily meet the grid code, postponing unplanned investments while a definitive solution could be planned to solve regulation issues. The power stage is composed of a three-phase four-wire Voltage Source Inverter (VSI) and a second order low-pass filter. The control strategy has three output voltage loops with active damping and two dc bus voltage loops. In addition, two loops are included to the proposed control strategy: the concept of Minimum Power Point Tracking (mPPT) and the frequency loop. The mPPT allows the voltage regulator to operate at the Minimum Power Point (mPP), avoiding the circulation of unnecessary reactive compensation. The frequency loop allows the voltage regulator to be independent of the grid voltage information, especially the grid angle, using only the information available at the Point of Common Coupling (PCC).

Existing System

Maximum Power Point Tracking Techniques

Proposed System

This paper presents a three phase DSTATCOM as a voltage regulator and its control strategy, composed of the conventional loops, output voltage and dc bus regulation loops, including the voltage amplitude and the frequency loops. This paper presents a voltage-controlled DSTATCOM-based voltage regulator for low voltage distribution grids, using a three-phase four-wire VSI with an LC low-pass output filter. Operation principles of the voltage-controlled DSTATCOM and the control strategy are presented. Additionally, two loops are included to the proposed control strategy: the concept of minimum power point tracking (mPPT) and the frequency loop. The mPPT avoids unnecessary reactive compensation, increasing the compensation capability. The frequency loop overcomes the practical difficulty of synchronization by correcting the frequency of the voltage reference. This paper proposes the combination of both loops, providing to the power company a solution for the poor voltage regulation in real distribution grids with superior PCC voltage quality.

Architecture

Three-phase four-wire VSI with LC low-pass filter