Research On Three-phase PWM Soft-switching Inverter Based On The Principle Of Zero-voltage And Zero-current Transfer

As modern power electronic technology’s growing maturity, power electronic devices are developing toward miniaturization and lightening, that requires switching elements in the devices must realize high frequency. As one of the primary power electronic converter technologies, traditional hard-switching inverter technology is very mature and widely used. But when the switching frequency is very high, there will be lots of disadvantages to reduce inverter efficiency, just like high switching loss and serious harmonic pollution. Soft-switching technology made the problems above readily solved. Focused on the topic of soft-switching three phase PWM inverter, this thesis made research and discuss on a new kind of resonant soft-switching inverter.First, the thesis introduced the develop status and significance of soft-switching inverter. We got the conclusion that there are still some problems in current pole resonant soft-switching inverter, just like high voltage and current stress of switches, complex controlling, and interaction between different phases. Based on this situation, a novel three phase PWM pole resonant soft-switching inverter based on the principle of zero-voltage and zero-current transfer topology circuit is proposed. In the proposed topology, independent control is achieved by three individual auxiliary resonant circuits for each bridge. Auxiliary switches are employed to control the resonant process. As the voltage across main switches decreases to zero before main switches are turned on and the current decreases to zero before main switches are turned off, zero-voltage turn-on and zero-current turn-off can be realized in the novel topology. The problems of turn-on capacitive losses in some zero-voltage turn-on topology and the tail current in some zero-current turn-off topology are both solved. And then, this thesis analyzed the soft-switching operation mechanism of the proposed topology in detail based on the equivalent circuit figures of different working modes, mathematical analyses of the dynamic process is also made. SPWM control strategy was established to realize the inverter’s zero-voltage and zero-current switching operation, and loop parameters are also calculated. Simulation is made upon the principle analysis, and the result proved the validity of the zero-voltage and zero-current three phase PWM soft-switching inverter topology and its SPWM control strategy. Comparing with the simulation result of traditional hard-switching inverter, the advantages of lower switching loss, and less harmonic pollution were proved as well.Finally, a summary and analysis is made about the theoretical analysis, simulation research and possible practical problems of the proposed three-phase soft-switching inverter. Some outlook of our researching work is summarized as well.