The Application Of BESS In Improving Power Quality And Stability Of Wind Power

Wind energy is currently the most widely used renewable energy, for the sake of effectively using the large-scale wind power, the wind farm must connect to the power grid. However, because of the strong randomness of the wind, the large-scale wind power connected to the grid can bring adverse effect to the frequency stability, voltage stability and power quality of the power grid. The BESS has a fast active/reactive power exchange capacity, when applied to wind power, which can smooth wind power fluctuations and provide wind farms a certain amout of reactive power support by participating in wind power AVC of the PCC. However, because the BESS has not a effective and feasible way of quantity standard disposal, we can only use actual value to sduty the BESS connected to the power grid, which is always inconvenient. Therefore, aiming at these problems, this paper carries out the following research work:Firstly, based on the actual value model of the BESS, this paper takes the converter of the BESS as ideal transformer whose ratio of transformation is equal to the modulation ratio. Then this paper builds the per unit model of the BESS, gives out the per unit equivalent circuit and analyzes the open-loop response characteristics of the BESS. On the basis of the research, this paper designs the direct power controller of the BESS.Secondly, when the BESS is applied to the wind power smooth and with the volatility of the wind power and the response of the BESS under consideration, this paper introduces the gray super short-term prediction of wind power, and uses low pass filter as basic filtering control method to smooth the power fluctuations. Combined with the SOC of the BESS and the change value of the wind power output, this paper designs the fuzzy controller to adjust the filtering time constant and gradually change the battery output, witch can keep the SOC within a limited range and smooth the wind power output as much as possible at the same time.Thirdly, in the application of the PCC AVC of the wind farm, based on conventional nine area and five area principle of the integrated substation reactive power control, this paper gives out the five erea chart of the wind farm through certain linearization. With th principle of hierarchical layer, this paper divides the AVC system into setting calculation layer, control and decision layer and BESS control module. Then this paper designs the AVC control strategy of the wind farm with BESS. Finally, this paper builds the simulation model of DFIG and BESS under SIMULINK environment and carries on the simulation of wind power smooth and AVC. The simulation results show that using the wind power smooth and AVC control strategy, we can effective smooth the wind power fluctuations and keep the voltage-reactive power of PCC is the desired state.