Coordinated control method for a photovoltaic-energy storage system using Kalman filtering

Due to strong volatility, photovoltaic (PV) power generation is often paired with an energy storage system (ESS) to generate electricity. Although the ESS can smooth the fluctuation of PV, frequent charging and discharging operation can seriously affect its lifetime, especially when the output of PV is close to the load in an islanded microgrid. This paper proposes a coordinated control method for a PV-ESS using Kalman filtering. The output power reference of the PV system obtained by the original maximum power point tracking (MPPT) control is modified using Kalman filtering. Optimization in economics is adequately analyzed, considering both the loss caused by non-MPPT control and the benefit of reducing charging and discharging cycles. In addition, the DC-link capacitor is controlled to be charged and discharged to shorten non-MPPT control duration and smooth the fluctuation of the PV system further. To validate the performance of the proposed method, the simulations based on MATLAB are implemented under various scenarios, considering variable irradiance, loads, and capacity ratios of the PV and the ESS, both in grid-connected and islanded microgrids. The results show the proposed method can smooth the fluctuation of PV-ESS output power and significantly reduce the charging and discharging cycle.