Utilization of Unified Power Quality Conditioner for voltage sag/swell mitigation in microgrid

Abstract

Microgrids (MG) are becoming increasingly attractive to consumers and a great number of them will be installed at consumer's sites in the future. Due to high penetration of distributed generation (DG) units with different types of loads, microgrids can cause power quality and power control issues. Some of them are voltage stability, swells and sags, and power factor improvement which require reactive power. Microgrid particularly when operated in islanded operating condition has to maintain the power balance independently of a main grid due to tightly coupled generation, consumption and lack of infinite bus. Even in grid connected mode reactive power compensation is still challenging due to linear and nonlinear loads. In this regard, new techniques and devices for VAR compensation in the micro grid are being investigated. Among these custom power devices are proving to be a powerful solution to power quality problems. Hence the key objective of this paper is to investigate reactive power compensation in microgrids by means of custom power device. The device considered is Unified Power Quality Conditioner (UPQC). This custom power device is initially modeled, simulated and tested in conventional distribution power system. Later the same is incorporated into the microgrid. The microgrid is developed with two DG units, a PV cell and a wind generator to give an output voltage equal to the conventional 3 phase 4 wire distribution system. The performance of the custom power device with its control technique in providing the reactive power compensation to resolve the power quality issues in microgrid with dynamically varying load is examined. A comparison is made between the conventional distribution system and microgrid in terms of compensation using custom power device.