Wind Generator Output Power Smoothing and Terminal Voltage Regulation by Using STATCOM/ESS

In this work, it is reported that STATCOM/BESS (battery energy storage system) topology can significantly decrease voltage and power fluctuations of grid connected fixed speed wind generators. One major problem in wind generator output power smoothing is setting of the reference output power. Constant output power reference is not a good choice because there can be some cases where wind speed is very low and then sufficient power cannot be obtained. In that case, energy storage device can solve the problem but large energy capacity may be needed. This paper proposes exponential moving average (EMA) to generate the reference output power, and thus the energy capacity of BESS unit can be small. The objective of the proposed STATCOM/BESS topology is to smooth the wind farm output by absorbing or providing real power. Moreover, its reactive power output can also be controlled to keep the wind farm terminal voltage constant. Control methodology of STATCOM/BESS topology suitable for the two objectives stated above is developed in this paper. 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/BESS unit can smooth well the wind generator output power and also maintain the terminal voltage at rated level.