A novel model predictive control strategy of D-PMSG wind turbine systems for LVRT based on two-state unloading resistance and super capacitor

Abstract

For low voltage ride through (LVRT) of the wind power generation system, rotor energy storage and super capacitor are promising options. When the rotor energy storage cooperates with the super capacitor for LVRT, the DC voltage will undulate violently due to the speed fluctuation. To solve this problem, a crowbar circuit topology and its control strategy including unloading resistance and super capacitor are proposed in this paper. During the process of LVRT, the super capacitor and resistor absorb energies together. In doing so, the DC bus voltage fluctuation will be suppressed by changing the value of the unloading resistance. The proposed method can effectively reduce the power of the unloading resistor and the capacity of super capacitor, and further decrease the hardware cost. By adding the penalty term of the current change rate to the cost function using the model predictive control method (MPC), the DC bus voltage fluctuation is reduced with the realization of rotor energy storage. The control performances of the proposed LVRT strategy are validated through simulation results.