| A t present, domestic and foreign electronic power conversion technologies are used by the PWM pulse width modulation, which contains two kinds of modulation methods:the transfer of pulse width of fixed frequency and the transfer of frequency of fixed pulse width. Although the two modulation methods make the power switch components worked in the switch state, so in theory open to minimize the wear and tear, but they are subject to frequency modulation. In practice, because people always want the highest possible frequency modulation, which can effectively reduce the conversion of the system size, weight and can improve the efficiency. However, the power switch components from full to cut-off or from the cut-off to full surpass the middle of must enlarge saturated, so the ball forward in the process of switching power components on the existence of switching losses, and along with the increased frequency modulation, a significant increase in switching losses, PWM as a constraint to the development of high-frequency obstacles.In order to solve these problems, the international community generally used two methods:first, resonant soft-switching means that the use of auxiliary capacitors, inductors composed of resonant soft-switching circuit, so that the switching components in zero current or zero-voltage opening hours, turn-off, so close to zero switching losses. The second is a buffer to absorb the way, this way is switching components in parallel at both ends of the buffer to absorb circuit is actually using the energy transfer methods, that is switch components from wear and tear of the shoulder transferred to the buffer to absorb circuit. Practical applications show that the two solutions only adapt to a small extent, control the complexity, low of reliability, especially in the high-pressure, high-frequency, high efficiency converter system, the traditional solution is limited.In view of this, this paper analyzes the traditional technologies and methods of the problems based on an effective solution to the traditional variable-flow technology that exist in the system modulation frequency and device switching losses of the negative correlation problem of the discrete constant energy chopper inverse transform method and adopted the principle of experimental verification. The basic principle of this method is the use of power switching components and energy storage devices consisting of power pulse to form circuit, it will be required to transfer energy in the time segmentation approach into a separate, containing a fixed energy and zero-crossing characteristics of the cyclical power pulse, then according to the different scope of the application follow-up conversion (such as wave formation, step-up or inverter, etc.), so as to achieve the entire transformation process of all the power switching elements are zero in the natural state of open and switch off from The purpose of the modulating frequency constraints. Its three main advantages:First, the entire transformation process of all the power switching components are zero at the natural state of the opening switch and turn-off, and not subject to modulation frequency constraints; are two happen even if the load-side short-circuit, the short-circuit power is still equal to determine the control value, therefore the safety of the system greatly improve; are three pieces can be used as a semi-controller power switching elements, and may be single-chip direct control. Sunplus SPCE061A Singlechip used as a control device in the experimental verification, The bridge of thyristor chopper inverter is composed of the one-way SCR. In the inverter output waveform for the relatively smooth sine wave, the successful implementation of the 220V 0.6KW on three-phase asynchronous motor of variable frequency stepless speed regulation, the speed control range is 10%-100%(the inverter output frequency is 5-50Hz, motor speed is 138-1380 r/min), the governing characteristics is U /f constant control. It can demonstrate the inverter method is correct and feasible. |
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