Research on Photovoltaic Power Smoothing Based on Time Window Tracking Differentiator

Abstract

The fluctuation of the photovoltaic(PV) output power will affect the stability of the distribution network and cause difficulty of grid dispatching. Smoothing methods such as low pass filter method and moving average method cannot guarantee the obtained curve meets the fluctuation requirements accurately. What's more, these methods will lead to the Battery Energy Storage System (BESS) acting frequently and the output of BESS getting large. It means higher requirements on the energy storage capacity. Based on Tracking Differentiator(TD), a Time Window Tracking Differentiator (TWTD) has been proposed in this paper to obtain the smoothing target curve of PV output power. Additionally, the state and total disturbance are observed by linear extended state observer(LESO), and the reference signal can be tracked quickly and accurately through the linear state error feedback. Finally, a rather smoothing curve can be obtained. Taking into account the capacity limit of BESS, a nonlinear energy storage constraint is proposed to adjust the energy storage output according to the State of Charge (SOC) of BESS. In this paper, the source of experimental data is the output of a PV power generation and energy storage system in East China. The simulation is based on Matlab/Simulink platform. The experimental results show that not only the algorithm can effectively suppress the fluctuation of the Point of Common Coupling (PCC) but it can reduce the times of BESS actions and save energy.