Resonant soft-switching technique is a hot topic in the power electronics field recently. It has improved the design of the power electronic converter greatly because of the deep research and widespread application of the soft-switching theory. Soft-switching technique can make the converter more efficiency, more power density, and more reliability.It can decrease the EMI caused by power converter and environment pollution (noise, etc) effectively. So it is necessary to do deep research for the resonant soft-switching technique.
Firstly, this paper analyzes and summarizes the research situation of resonant soft-switching technique and main topologies. And it indicates the main advantages and disadvantages. Then it pays more attention to analyze the parallel resonant DC link circuit theory and operating modes. It also analyzes how the resonant circuit realizes the resonant process. This paper also simplifies the control part design of the parallel resonant DC link soft-switching inverter by DSP.
Secondly, this paper analyzes the operating principle of the SPWM modulation strategy for the full bridge inverter deeply. And it also analyzes the sine wave producing process. It also gives the parameters of the resonant components. And then the output voltage harmonic for the single-phase three-level SPWM inverter under the half triangular and half saw-tooth carrier wave is studied. It also discusses how to select the carrier ratio N and the effects to the output wave by modulation ratio M.
Thirdly, this paper studies the digital PID theory and its application and then deduces the discrete PID incremental control formula. The paper also discusses the effect caused by truncation error for output voltage and then derives the improved PID regulation method. Based on the conclusion, the paper establishes the digital PID voltage feedback controller. In the aspect of the control realization, this paper studies the digital control technique with digital signal processor (DSP).And then the SPWM modulation strategy and digital PID controller with digital signal processor (DSP) technique are united. This paper also finishes designing and debugging software and hardware of the whole inverter system control part.
Keyword: Parallel resonant DC link;inverter; soft-switching; DSP
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