An improved stability method of the offshore islanded wind-PV-battery microgrid based on capacitor voltage feedforward

Objectives For the worse stability of the offshore wind-photovoltaic(PV)-battery weak microgrid caused by the limited capacity, the energy intermittent and the load mutation with the characteristic of bilateral randomness, the bus equivalent impedance-based analysis is adopted and the capacitance voltage feedforward method is presented in the wind and PV inverters, aiming to adjust the output impedance given the power system stability. Methods Firstly, the offshore wind-PV-battery microgrid electric circuit and its control strategy is investigated. This power system is working in the master-slaver mode, namely the battery cell, composed of the same peer multi sub-elements controlled in the power droop strategy, is as the master power supply for stable grid voltage, whereas the grid-connected wind and PV generation cells are as the slaver power supplies. Then the system equivalent model and the inverter model are established for the bilateral randomness system stability analysis from the inverter device to microgrid system. The theories of the LCL resonant suppression, the phase margin (PM) increasement and the inductance current weaken impact to grid voltage are analyzed in detail. Results The experiment results testified that this proposed capacitance voltage feedforward has the capacitor feature with lead angle which improve the value of PM to 13.8°, which effectively enhance the adaptability of new energy power generation devices to weak microgrids. Conclusions The proposed method has important theoretical significance and application prospect for improving the stability of the offshore wind-PV-battery microgrid system.