Zero fundamental voltage vector randomization method for space vector pulse-width modulation (PWM)

Abstract

The invention discloses a zero fundamental voltage vector randomization method for space vector pulse-width modulation (PWM). According to the method, a modulated wave implied in phase voltage is decomposed into a definitive part and a random part; statistic characteristic parameters such as a mean value and standard deviation of the random part are kept constant at the modulation ratio; the randomization range of a zero fundamental voltage vector is the action time of the minimal zero fundamental voltage vector within a complete modulated wave cycle; and when the randomization method is applied to a seven-segment symmetrical modulation mode, the randomization range is the result that the minimal holding time required for current measurement is added to the minimal value, so that the measurement accuracy is improved. According to the technical scheme of the invention, sufficient randomization can be realized; the statistic characteristic parameters of the random part of the implied modulated wave cannot change along with time; effective application of a plurality of research methods and analysis tools based on the stationary random process is facilitated.

Description

technical field [0001] The invention belongs to the technical field of AC frequency conversion, and in particular relates to a method for randomizing space vector PWM zero basic voltage vectors. Background technique [0002] The two-level three-phase inverter can convert direct current into alternating current with variable frequency and amplitude, and has been widely used. For example, in the driving system of electric vehicles, the inverter is responsible for converting the DC output from the battery into three-phase AC, and then drives the three-phase permanent magnet synchronous motor, such as figure 1 shown. The alternating current output by the inverter is equivalent to the voltage pulse according to the principle of time averaging, that is, pulse width modulation (PWM) technology. Space vector PWM (SVPWM) technology is commonly used in two-level three-phase inverters. In addition to the required fundamental wave voltage, the output voltage also contains a large num...

AI Technical Summary

Problems solved by technology

[0004] Both the inverter and the SVPWM strategy are highly nonlinear systems, especially the randomization makes the system complex and makes the comprehensive analysis of the inverter performance more difficult, which increases the difficulty of design, control and performance evaluation

The principles and techniques of stochastic processes can be used to design and evaluate the performance of stochastic SVPWM strategies; however, the randomization of two zero-fundamental voltage vectors is equivalent to introducing randomness into the implied modulating wave

The statistical characteristic parameters of this random part change with time, which leads to the ineffective application of many research methods and analysis tools based on stationary random processes, which greatly limits the design, performance evaluation and new strategies of random SVPWM strategies. development

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