The Research On Improving The Voltage Utilization For Motor Controllers

The motor controller is a device,which converts DC to AC, the principle of which is based on PWM(Width Modulation Pulse) technology.And one of the important index of the technology is the utilization of the DC voltage. The improvement of the utilization rate of the DC voltage can improve the system efficiency, extend the speed regulation range of the AC motor, and improve the output power of the motor.Currently widely used SVPWM(Vector Pulse Width Modulation Space) technology SPWM(Pulse Width Modulation Sinusoidal) has greatly improved the voltage utilization. Develop a novel rectangular-wave- voltage control technology based on the SVPWM and SVPWM overmodulation technology. The realization of the motor controller of DC voltage utilization rate can be from zero continuous transition to maximum. The rectangular wave voltage, the high- level duty cycle is 0.5 in the period of a electrical angle, is very difficult to achieve a good control of the rectangular wave voltage. This paper introduces SVPWM principle and realization method, elaborated the SVPWM over modulation strategy and a modulation method,which is simple and effective, and the rectangular wave voltage is studied,proposes a current closed-loop control of rectangular wave phase control strategy to achieve maximum utilization rate of voltage.This paper will introduce the SVPWM technology, focusing on the theoretical basis and implementation method of SVPWM. The basic electrical structure of the motor controller is introduced, the implementation algorithm of SVPWM is described in detail and the simulation model of SVPWM is built with MATLAB, and its simulation is carried out.Then, on the basis of SVPWM, the over modulation method based on SVPWM is introduced. In the over modulation region, different modulation algorithms can deal with the amplitude and phase of the voltage vector. According to the amplitude and phase of the voltage vector, the modulation region is divided into two regions.In thefirst region, does not change the phase target of amplitude only to do some reduction with the amplitude, in the over modulation zone two, the amplitude and the phase of target voltage- vector are processed according to a certain algorithm.Therefore, this paper will focus on the principle and method of rectangular-wave–voltage’s phase control. Because of the characteristics of the rectangular wavevoltage the amplitude can not be controlled, only the phase can be controlled. At present, the vector control method is widely used in AC motor. This paper will briefly explain the vector control equation of AC motor. This paper will introduce the mathematical relationship between the rectangular wave phase and motor equation,which describes the principle of closed current- loop to control the phase of rectangle wave, and analyzed the shortage of torque closed-loop control. Finally the algorithm do some simulation analysis on the algorithm.