MOPSO-based optimal fuzzy logic control strategy for standalone hybrid diesel-wave energy conversion system

Abstract

The paper proposes a Multi-Objective Particle Swarm Optimization (MOPSO)-based Fuzzy Logic Control Proportional-Integral-Derivative (MOPSO-FLC-PID) controller for stand-alone hybrid Diesel- variable speedWave Energy Conversion System (WECS).The optimal control performance can be achieved by tuning scaling factors of the FLC and gain parameters with Multi-ObjectiveParticle Swarm Optimization (MOPSO) algorithm in order to improve system dynamic performance especially when nonlinearity,uncertainty and complexity of the hybrid Diesel-WECS are involved. Number of objective functions is defined to measurethe performance of the proposed controllers such as minimize the transient DC and AC voltage and current ripples, minimizethe DC and AC voltage and current Total Harmonic Distortion (THD), minimize the absolute total control steady state errordeviations, minimize the RMS absolute voltage deviations at the DC and AC load collection buses, ensure minimal losses aswell as wave energy optimal power utilization. Since some of these objective functions are conflicting, MOPSO is used to finda Pareto front from which a desired optimal operating state can be chosen. For the purpose of comparing the improvementobtained in the system dynamic performance with the application of the MOPSO-FLC-PID procedure to tune the scaling factorsof the FLC and the PID controller gains, these results are compared with those obtained using traditional Ziegler-Nichols PIDapproach, PID type fuzzy logic controller designed with Single-Objective Particle Swarm Optimization (SOPSO-FLC-PID),traditional PID type controller optimized with SOPSO-PID and traditional PID type controller optimized with MOPSO-PID.A complete simulation model is developed for such stand-alone hybrid Diesel-WECS under variable speed operation usingMATLAB Simulink environment. Simulation results show that the proposed design approaches are efficient to find the optimalscaling factors and PID gains of the controllers and therefore improves the transient performance of the hybrid Diesel-WECSover a wide range of operating conditions, sudden load change and three-phase short circuit fault.