Journal of Power Electronics, Vol. 13, No. 5, September 2013 909 http://dx.doi.org/10.6113/JPE.2013.13.5.909 JPE 13-5-17 Coordinated Control of Reactive Power between STATCOMs and Wind Farms for PCC Voltage Regulation Thanh Hai Nguyen * , Dong-Choon Lee † , Tan Luong Van ** , and Jong-Ho Kang *** †* Dept. of Electrical Engineering, Yeungnam University, Gyeongsan, Korea ** Ho Chi Minh City Electric Power College, Ho Chi Minh, Viet Nam *** Wind Energy Biz Division, Hyosung Co., Ltd, Changwon, Korea Abstract This paper proposes a coordinated control of the reactive power between the STATCOMs (static synchronous compensators) and the grid-side converters (GSC) of wind farms equipped with PMSGs (permanent-magnet synchronous generators), by which the voltage fluctuations at the PCC (point of common coupling) are mitigated in the steady state. In addition, the level of voltage sags is reduced during grid faults. To do this, the GSC and the STATCOM supply reactive power to the grid coordinately, where the GSCs are fully utilized to provide the reactive power for the grid prior to the STATCOM operation. For this, the GSC capability of delivering active and reactive power under variable wind speed conditions is analyzed in detail. In addition, the PCC voltage regulation of the power systems integrated with large wind farms are analyzed for short-term and long-term operations. With this coordinated control scheme, the low power capacity of STATCOMs can be used to achieve the low-voltage ride-through (LVRT) capability of the wind farms during grid faults. The effectiveness of the proposed strategy has been verified by PSCAD/EMTDC simulation results. Key Words: Coordinated control, GSC, Low-voltage ride-through, PCC voltage regulation, PMSG, STATCOM, Wind farms I. INTRODUCTION Nowadays, the penetration of wind power into the grid has been increasing continuously. As a result, its influence on the stability of existing power systems has become an important issue. In addition, this situation has changed the role of the wind power in the grid. Wind power plants are required to control the grid voltage and to enhance power system stability [1], [2]. Furthermore, for the security of power system operation, the disconnection of a significant number of wind turbine generators is no longer accepted [1], [3]-[5]. Fig. 1 shows the different grid codes for the LVRT requirements and the reactive current required to provide the grid with consideration of the voltage drop profile [3]. As for the power stability issues, the management of the reactive power exchanged between the wind farm and the grid is essential [6]. In order to comply with power factor requirements and voltage stability requirements at the PCC, most wind farms are equipped with switched-shunt capacitors for static reactive power compensation, especially in fixed- speed wind turbine systems. Today, variable-speed wind turbine (VSWT) systems are preferred to fix-speed systems [7]-[11], where the VSWT systems are controlled to Manuscript received Jan. 28, 2013; revised Jul. 26, 2013 Recommended for publication by Associate Editor Seung-Ho Song. † Corresponding Author: dclee@yu.ac.kr Tel: +82-53-810-2582, Fax: +82-53-810-4767, Yeungnam University * Dept. of Electrical Eng., Yeungnam University, Korea ** Ho Chi Minh City Electric Power College, Viet Nam *** Wind Energy Biz Division, Hyosung Co., Ltd., Korea Fig. 1. Grid codes [3]. (a) LVRT requirements. (b) Amount of required reactive current of Spanish grid code.