Research On Modulation Methods Of Sine Wave Output VVVF Power Supply

With the rapid development of information technology, sine were out put VVVF power supplies are widely used in a lot of fields. The requirement output waveform of VVVF power supply is rising. The output quality of VVVF power supplies mainly includes two aspects. One is the accuracy of stable output waveform; the other is the good transient response. So research on inverter control strategies which are not only simple, but also have better transient and stable performance is always the hot research question of power tectonics field. In order to get high quality and high reliability VVVF supply, this paper presents the study of SPWM modulation methods and digital control strategies of sine wave output inverter.There are so many advantages of digital control, such as simple hardware circuit which solved the problem of floating parameter with tempter in analog circuit, the flexible and advanced control which can be applied in digital control and so on. Power supply products designed by digital control not only have reliable performance, but also can be easy produced in large quirkily so research period is reduced. Digital control power supply is trend of current power supply products design.This paper mainly presents the research on different modulation methods of sins wave output VVVF power supply controlled by DSP, including the characteristics of SPWN inverter under differ modulation methods, the distribution of voltage harmonic waveform, the digital realization of SPWN modulation waveform and the inverter model of different modulation using digital control chip TMS320F240,the control strategies of inverter are instantaneous voltage value inner loop and the mean voltage outer loop . The quality of sine wave can be guaranteed by the instantaneous voltage value inner loop and the output sine wave value can be controlled by the mean voltage value outer loop . PI controllers are used in both loop, also the detailed parameters design produces is presented. In succession, the DSP controlled software floe chart is drawled and the influence of drive dead time on output voltage waveforms and the THD of output voltage waveform of three different modulation methods are provided.