A Time-Varying Hierarchical Load Frequency Control Method for Multi-area Power System with Wind Power Participation and HVDC Tie-Line based on MAS Structure

To solve the LFC issues of the HVDC multi-area grids caused by the participation of the wind power, a novel control strategy is proposed in this paper. Firstly, considering that the wind turbines participate in the primary frequency regulation, the LFC model of the multi-area interconnected grids with HVDC tie-line is constructed. Due to the uncertainty of wind speed, the parameters of the LFC system are dynamic. Then, a control structure with the cascade of the time-varying MPC and PID controller is designed. The PID is connected in series behind to adjust the output of the time-varying MPC so as to improve its control performance. Furthermore, a dynamic hierarchical control method is proposed, of which time-varying MPC activates or not depends on the control requirements. It applies only the PID controller when frequency changes little but the cascade structure with PID and time-varying MPC when that changes much. Because the LFC system of each area is an independent subsystem among which the information can transfer, a MAS is put forward during the design. Finally, a three-area interconnected power system is analyzed to testify the feasibility of the proposed method. The simulation results show that the proposed control method can reduce the time complexity of system control algorithm by adjusting the participation of the upper time-varying MPC controller, which is under the premise of ensuring the control effect.