Fuzzy multi-objective technique integrated with differential evolution method to optimise power factor and total harmonic distortion

The main aim of active-filter-based power-quality improvement schemes is to reduce the total harmonic distortion (THD) and improve power factor (PF). According to standards, selective harmonic distortion (SHD) should be controlled too. Non-sinusoidal current owing to non-linear loads causes a non-sinusoidal voltage. Under such conditions, any attempt to make the power factor unity by usual methods will cause a non-sinusoidal current, which increases the THD. Also, attempt for harmonic-free current may not conclude unity power factor because of harmonics present in the voltage. Thus, there is a tradeoff between reduction of THD and improvement in power factor. One of the solutions to this tradeoff is to optimise PF while keeping THD and SHD into their specified limits. Differential evolution (DE) is introduced in this study and used for this optimisation problem, and the results are compared with four types of particle swarm optimisation (PSO), including conventional PSO, linearly decreasing inertia PSO, Type 1 PSO, constant inertia PSO and with the traditional optimisation method. It is seen that DE algorithm converges to a better result much faster than the other algorithms. Furthermore, using fuzzy strategy a multi-objective optimisation is proposed to optimise PF and THD simultaneously while keeping SHD in its limit. It is observed that using these optimisation methods, PF and THD are more improved.