The Research Of Smoothing Method For Wind-photovoltaic-storage Hybrid Power System

The active power output of intermittent power is random and fluctuant, which is contradictory with the requirement that the power source should be controlled and adjustable. And it is also an main constraint of grid to accept wind power, solar power and other clean energy. From the grid perspective, the grid-connected intermittent power is a random disturbance source. The reliable operation of the grid is mainly affected by the power fluctuation. Therefore, it is necessary to study an effective power control method to stabilize the fluctuant power output of wind-photovoltaic-storage hybrid power system.Underpinned by the analysis of fluctuation characteristics of wind power output and PV output, a smooth control method based on the power curve is proposed in this paper, with the target that wind farm and photovoltaic power plant should make full use of schedulability themselves and the frequency of charging and discharging of energy storage device should be minimized. The details are as follows:(1) Power dispatching value is not available at power smoothing mode. Therefore, power curves are proposed as the target power curves for power system to track. The power curves of wind-photovoltaic-storage hybrid power system and subsystems are developed based on the predictive information of wind farm and photovoltaic power plant, in order to smooth the power fluctuation. The total power output is fluctuated by controlling each subsystem to generate power in accordance with the power curve.(2) Because power curve are calculated on basis of the forecasting information, the accuracy is affected by forecast error. Therefore, energy storage devices are used to smooth the actual output power, in order to ensure the smoothness of the final output of wind-photovoltaic-storage hybrid power system. Firstly, a weighted moving average filter algorithm is designed to calculate the charge and discharge power of storage device. Secondly, an SOC control strategy based on fuzzy control is proposed in order to maintain the SOC of energy storage device at a reasonable level. Finally, the purpose of smoothing power fluctuations is achieved on the premise of maintaining the state of charge of storage at a reasonable level.(3) Based on Matlab/Simulink, the power curves for wind-photovoltaic-storage hybrid power system and each subsystems are calculated. The simulation is designed to prove the effectiveness of real-time power smooth strategy and fuzzy control strategy of storage devices. Simulation results show that: power fluctuations get smaller and meet national requirements by using the smooth control strategy of this article, and the SOC is maintaining at a reasonable level.