Integrating particle swarm optimization and routh-hurwitz's theory for controlling grid-connected LCL-Filter converter

Abstract

This paper proposes a method of integrating the Particle Swarm Optimization (PSO) technique with Routh-Hurwitz's stability theory in a special optimizing process as an effective tuning method for the PI controller. This overcomes the problem of resonance frequency between the grid and filter, which affects on system's stability margin. This concept realised by combining multiple restrictions functional, time and frequency behaviour besides the stability criterion, as a comprehensive evaluation to enhance the performance and its activity. The decoupled model of the LCL-filter grid-connected voltage source inverter (VSI) is used to simulate the multi-loop current control scheme. This approach operates in offline mode to achieve the optimal controller's parameters. Simulation results demonstrate an interesting harmony between the system's performance and stability in different operating conditions, which gives phase margin= 87o, gain margin=7 dB, and damping ratio=0.55. The proposed design shows superior performance, as compared with previous works, in dynamic and steady state performances, which gives rise time=7.861ms, settling time=27.6ms, overshoot=2.282%, THD=1.967%, and RF=3.017%, besides an acceptable current's harmonics contents.