Wind generator output power smoothing and terminal voltage regulation by using STATCOM/SMES

Due to random variations of wind speed, the output power and terminal voltage of a fixed speed wind generator fluctuates continuously. These irregularities in power output affect the power quality and thus an energy storage system is needed. In this work, the STATCOM/SMES system with a voltage-source IGBT converter is proposed as a controllable energy storage system. The proposed STATCOM/SMES system is used to provide both active and reactive power, which can significantly decrease the voltage and output power fluctuations of grid connected fixed speed wind generator. For wind generator output power smoothing, constant output power reference is not a good choice, because sufficient power cannot be obtained when wind speed is very low. Energy storage device can solve the problem but large energy storage capacity may be needed. Therefore, a low pass filter approach is adopted to generate the line power reference in the proposed system, in which the time constant corresponds to the energy storage capacity. Thus the energy storage capacity of SMES can be made comparatively small. Real wind speed data is used in the simulation analyses, which validates the effectiveness of the proposed control strategy. Simulation results clearly show that the proposed STATCOM/SMES system can smooth well the wind generator output power and also maintain the terminal voltage at rated level with reduced energy storage capacity.