Improved optimal harmonic reduction method in PWM AC-AC converter using modified Biogeography-Based Optimization Algorithm

Pulse width modulation (PWM) AC-AC converter is a power electronic device which has many applications, because it can control the load voltage and active power. This converter cuts the voltage wave form, so the output voltage will have harmonics. Since the fundamental component of output voltage influences the active power, assigning weighting factor to the optimization problem of harmonic reduction in the converter has been proposed in this paper. To solve the optimization problem a hybrid algorithm including biogeography-based optimization BBO and simulated annealing (SA) has been presented. This algorithm has the advantages of the two method simultaneously. Since many evolutionary optimization algorithms may not reach the global optimum solution, in order to develop the search process, a local search algorithm in an inner loop i.e. SA is applied to the obtained solution by main search algorithm i.e. BBO. In the other word, the second level optimization by SA is applied to the best answer of BBO in each iteration, to find the global extreme point. The proposed algorithm has been applied to some standard benchmark functions. After validation using these problems, the main problem which is a practical problem to minimize the harmonics for PWM AC-AC converter has been solved. Simulation results show the efficiency of proposed method by considering weighting factor to optimize a practical problem in power engineering area in order to harmonic reduction as well as improving fundamental voltage as an important issue.