| The high-frequency link inverter consists of a high frequency inverter in transformer original side, a high-frequency transformer, an output cycloconverter in transformer secondary side, and an output filter. The high-frequency link inverter has been widely studied for its characteristics of mature topology, isolated power conversion and bidirectional power flow, which overcomes the disadvantages of traditional inverter with big volume, high noise and cost. However, for high-frequency link inverter, the safe commutation problem of cycloconverter has always been the technical difficulty. Aiming at this problem, the de-re-couple uni-polarity phase-shifted control strategy is proposed in this paper, which can achieve ZVS of all the switches in cycloconverter and natural commutation of the transformer leakage inductance and filter inductance.Firstly, the topologies of high-frequency link inverter are summarized, and the research status is introduced. The advantages and disadvantages of the topologies are analyzed, and the single-phase high-frequency link cycloconverter is explained in detail, then several present exiting commutation methods are described.Secondly, the advantages of de-re-couple modulation strategy and uni-polarity phase-shifted control strategy are summarized, based on this, the de-re-couple uni-polarity phase-shifted control strategy is proposed, and the working process of soft commutation is analyzed in detail. Then the causes of voltage oscillation and voltage spike across the switches in cycloconverter are discussed, and the feasibility of eliminating voltage oscillation by introducing the clamping diode and resonant inductor in transformer original side is proved in theory. The operation process of single-phase high-frequency link inverter with clamping diode and resonant inductor is emphatically analyzed.Thirdly, the closed-loop control and gird-connected control of single-phase high-frequency link inverter are studied. Based on uni-polarity phase-shifted control strategy, the mathematical model of single-phase high-frequency link inverter is established. The double closed-loop control and gird-connected control are studied and the power voltage synchronous technology which is based on second order generalized integrator(SOGI) is researched, then the parameters of PR and PI regulators are designed.Finally, after theoretical and simulation study, the hardware and software of the system are designed in detail, and the 1k VA experimental platform which is based on DSP and CPLD digital control is constructed. The correctness and effectiveness of the theory above are verified by experimental results. |
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