Performance Analysis of Flower Pollination Optimization-based PID Controller for Regulation of Frequency of Hybrid Wind-Hydro Power Plant

Abstract

The world is moving towards generating electricity from renewable energy sources (RESs) to reduce harmful pollution; wind turbines (WTs) and hydropower plants (HPPs) are the most advanced and environmentally friendly forms of electrical energy. However, the interconnection of RESs, especially WTs, with the power grid brings a challenge: keeping the grid frequency constant. Wind speed determines the fluctuating nature of wind power. Due to variations in wind speed, the outputs of double-fed induction generator (DFIG) based WT also vary. In addition, the variable nature of the load leads to a power imbalance between demand and supply. This imbalance of power may cause a deviation in the frequency of the grid from its nominal. The drop or rise of the grid frequency also causes trips offline for generators, equipment damage, and system blackout. To overcome this difficulty, a frequency regulation for grid-connected WT- hydropower plants based on flower pollination optimization algorithm-based Proportional integral derivative (FPOA-PID) controller is put forth in this work. The system consists of two PI controllers for the rotor side converter (RSC), three PI controllers for the grid side converter (GSC) of DFIG, one PID for pitch angle control, and one PID for frequency regulation. The parameters of the frequency regulation controller are tuned using FPOA and particle swarm optimization (PSO) for comparison. The dynamic performance of the system is tested in MATLAB/SIMULINK. Accordingly, the FPOA-based PID for regulation of the grid frequency has a settling time of 1.0106sec, an overshot of 0.0228Hz, an undershot of 0.0289Hz, and the final output frequency of the grid is 50Hz with 0% steady-state error (SSE). In contrast, the PSO based PID controller has a settling time of 1.9406sec, an overshot of 0.02943Hz, an undershot of 0.0375Hz with 0% SSE at 11m/s and 0.05pu load. The FPOA-based PID has better convergence performance than PSO-based PID controllers. The normal operational range of frequency (grid code is between 49.5Hz to 50.5Hz in Ethiopia National Transmission system (ENTS) and the result indicates that, with the FPOA-PID technique, the overall performance of the system showed robustness regardless of the presence of load variations and the wind speed fluctuations. A performance comparison is conducted between the proposed FPOA-PID, PSO-PID, and PI controller schemes to verify the superiority of the suggested technique in the presence of a DFIG-WT and HPP.