Fast Frequency Response Using Model Predictive Control for A Hybrid Power System

Abstract

Large-scale penetration of Renewable Energy Sources (RESs) in Hybrid Power Systems (HPSs) consists of predominantly asynchronously interfaced sources. Asynchronous interconnection of RESs is made possible by using Power Electronic Converters (PECs); however, it subsequently reduces the system inertia due to less rotational mass. The decrease in system inertia causes a high Rate of Change of Frequency (RoCoF). Consequently, frequency control becomes challenging with high RoCoF. To maintain the frequency at a nominal value, the power balance between the load and generation is necessary. The excess or deficit in power from RES is uncertain, and stochastic load disturbances should match generation and storage changes. Owing to high RoCoF, the response of the system to maintain power balance should be obtained within a minimum time. Therefore, Fast Frequency Response (FFR) using the available reserves is of prime significance. This paper addresses the FFR problem by proposing a modified Model Predictive Control (MPC) by introducing RoCoF in the objective function to achieve FFR using primarily Fuel Cell (FC) storage in a Hybrid Power System (HPS). The modified MPC controller's performance is compared with the conventional PID and MPC controllers by testing the dynamic model for both situations - i) constant step and ii) random load fluctuations and wind disturbances using MATLAB/Simulink. Simulation results under various cases show that the proposed MPC has improved the performance parameters (settling time, peak overshoot, and peak-peak magnitude) of the step response.