PMSG LVRT Strategy with Frequency Divided Droop Control of Supercapacitor

When rotor and supercapacitor cooperate to solve the low voltage ride-through, the rotor difficultly real time responds to wind fluctuation with the inertia increasing. The speed change lags behind the wind and mismatches, resulting in the speed and DC voltage fluctuation. To solve this problem, a model predictive control using frequency division droop control is proposed. The power of supercapacitor is controlled by MPC to maintain DC voltage stability. Through virtual impedance droop control, the unloading resistor absorbs the high frequency fluctuation power, effectively eliminating the fluctuation of DC voltage. The fluctuation of speed is reduced by using the cost function of speed. This method effectively suppresses the speed mismatch caused by wind fluctuation. The hardware-in-the-loop results verified the effectiveness of proposed method.