Harmonic Analysis And Simulation Of Induction Motor Fed By SPWM Inverter

With the development of power electronic technology, variable-frequency adjustable-speed system for AC motor has been voted as the most predominant power driving system in modern AC adjustable-speed systems. The problem of pollution caused by harmonic appears gradually with the development of variable-frequency adjustable-speed technology for motor. In order to eliminate harmonic, save energy and reduce loss, a lot of researches and analyses have been done. At present, aiming at harmonic produced by rectifier of variable-frequency adjustable-speed system for three-phase induction motor, a lot of analyses and calculations have been done and accurate filtering methods have been researched to make output voltage of rectifier equal DC voltage approximately. But harmonic produced by inverter is only analyzed qualitatively, and few literatures about quantitative calculation come forth.The principle of SPWM control technology is described in detail in the first part of this paper. The direction and meaning of the research on harmonic are pointed out at the same time. According to Bessel function and Fourier series theory, generation, magnitude and distribution of voltage harmonic generated by single-phase two-level SPWM inverter and three-phase SPWM inverter are analyzed and calculated particularity and concretely in allusion to inverter-motor system. Based on the calculation result, the problem of harmonic is analyzed by taking the form of figure and text, and the corresponding conclusion was drew. In addition, some factors that affect the distribution of harmonic spectrum of SPWM output voltage are discussed in detail. In this paper, the effect of harmonic on magnetic motive force of windings, slip ratio of rotary magnetic field, torque and copper loss of induction motor are discussed, which offers reference for the design of variable-frequency adjustable-speed system for induction motor, harmonic analysis of power supply and calculation of additional loss of motor. In the end, simulation model of SPWM inverter is set up with power system library of Simulink in MATLAB software. Through simulating, not only the correctness of mathematical deduction in theory is validated, but also a good method of simulation is offered for the design of power electron circuit and variable-frequency adjustable-speed system for AC motor.