The Research For Selective Harmonic Elimination Technique Based On Genetic Algorithm

The inverter as a quite obvious energy saving effect power electronic device, which can drive the operation of AC motor, mainly for control speed, adjust the output voltage, current and change the output frequency. The key technology of the inverter is to dc to ac inverter technology. However,the process is accompanied by a large number of harmonics and it will produce so abominable influence to the motor load that it is difficult to achieve stable operation. The selective harmonic elimination technology not only can effectively eliminate selected harmonics, but also the other remaining harmonics has better inhibition ,therefore the efficiency of inverter was improved. On the basis of analyzing the basic principle of selective harmonic elimination technique, this paper designs a kind of selective harmonic elimination inverter which the output voltage and current waveform is similar to sine wave, AC motor operation has been greatly improved.Firstly, based on selective harmonic elimination technique basic principle and Fourier series theory, the harmonic elimination model of output waveform of three-phase voltage type inverter is built. The model is nonlinear transcendental equations between the output voltage ,the harmonic voltage and switching angle. How to find a rapid and effective solution has become a pressing matter of the moment of selective harmonic elimination technique.Traditional Newton-Raphson algorithm can solve switching angles, but the more stringent requirements for initial value, calculation time is relatively long. This paper presents genetic algorithm which will apply to selective harmonic elimination technique, for the initial value selection is random and convergence speed is faster.Secondly, the paper makes simulation analysis in bipolar Selective harmonic elimination model, by using Newton-Raphson algorithm and genetic algorithm for solving nonlinear transcendental equations get switching angles. At the same time, observing the switching angles with the institutional alterative curve and comparing the phase voltage harmonic distortion rate. Finally, the two methods combine their respective advantages to improve the basic genetic algorithm- hybrid genetic algorithm. When the algorithm solves the nonlinear transcendental equations, solving process is the first to use the basic genetic algorithm for solving transcendental equations, and then obtain exact solutions by Newton-Raphson algorithm. The hybrid genetic algorithm is applied to solve the nonlinear transcendental equations, using frequency analysis to observe the harmonic suppression effects in different switching angles and modulation degrees. The results show that hybrid genetic algorithm is feasible in selective harmonic elimination technique.Again, designing a selective harmonic elimination inverter under VVVF control, it consists of two parts: the power circuit and the control circuit. The control circuit is composed of A/D converter, voltage to frequency converter, counter and a data memory, and the power circuit use the three-phase voltage type inverter circuit. The main application of inverter circuit is DIP-IPM (intelligent power module)which realizes the contravariant link in the inverterFinally, through debugging the hardware circuit of the inverter, and analyzing the output voltage waveform of the experimental circuit, genetic algorithm and the improved method for solving the switching angles of selective harmonic elimination technique are verified to be correct.