Enhancement of Power Quality and Stability in Wind Farm to Weak‐ Grid Connection Using Upqc

Abstract

Most of the wind energy conversion systems around the world employ Squirrel Cage Induction Generator (SCIG) which is directly connected to the grid. In modern power generation, the Wind Farms (WF) are connected through Medium Voltage (MV) distribution headlines. A situation commonly found in such scheme is that the power generated is comparable to the transport capacity of the grid. This case is known as Wind Farm to Weak Grid Connection. The major problems due to weak grids are voltage fluctuations and this causes poor voltage regulation at the Point Of Common Coupling (PCC). Thus the combination of weak grids, wind power fluctuation and system load changes results in disturbances in the PCC voltage, it will have negative impact on Power Quality and WF stability. This situation can be improved using control methods at generator level, or compensation techniques at PCC. In case of wind farms based on SCIG directly connected to the grid, it is necessary to employ the Custom Power System (CUPS). This project proposes the CUPS device i.e., Unified Power Quality Compensator (UPQC) which is designed to mitigate voltage fluctuations at the grid side and to maintain the voltage in the WF terminals. The internal control strategy is based on the management of active and reactive power in the series and shunt converters of the UPQC, and the exchange of power between converters through UPQC DC–Link. This approach increases the compensation capability of the UPQC with respect to other custom strategies i.e., DVR and DSTATCOM that use reactive power only. Simulations results show the effectiveness of the proposed compensation strategy for the enhancement of Power Quality and Wind Farm stability.