Research On Series-Parallel Technology To High Power Inverter Power Supply

Today, as the increasing demand of capacity and the more stringentrequirement for high-power inverter power supply, one of the importantdevelopment directions of modern power electronic technology is how to improvethe capacity and the quality of the power electronic inverter device output power.In fields of high voltage and high power，the contradiction between the workingvoltage and the switching frequency of power switch tube restrict the extensiveapplication of inverter technology. An effective way to solve these problems iscombined H-bridges cascade multi-level inverter with carrier phase shifting SPWMtechnology. The low pressure device is successfully applied in high-pressuresituations, and the high equivalent switching frequency is got by using lower deviceswitching frequency. In addition, the switch loss is lower and the level of outputvoltage and current can be improved. Therefore, circuit topology and thecorresponding control strategy of H-bridges cascade multi-level inverter isregarded as the current research hot spot.In this paper, H-bridges cascade multi-level inverter of series-parallel invertercombined with carrier phase shifting SPWM control method are analyzed. Thereare three kinds of basic topology structure of H-bridges cascade multi-level inverter,which are Series, parallel and series-parallel type. The main control method is thecarrier phase shifting SPWM technology. Based on the principle of bipolar carrierphase shifting SPWM control technique, the characteristics of output voltage andcurrent of three kinds of topology structure are derived and analyzed in detail.Through simulation analysis, the Carrier phase-shifted SPWM control method foran H-bridge series-parallel inverter is proposed.One of the key problems of series-parallel inverter technology is thecirculating current which is analyzed in the paper. Firstly, circulating current inparallel inverters is studied and the factors affecting the size of the circulatingcurrent is interpreted. According to the specific requirements of EAST fast controlpower in EAST superconducting Tokamak, the design method of flow reactor is putforward. Secondly, the mode of current loop control is introduced to share thecurrent between parallel units. Based on the instantaneous reactive power theory, the circulation inhibition method is adopted. Finally, the results of the simulationverify the availability of two control strategies.On this basis, the six H-bridges series-parallel inverter experimental deviceplatform is built, and the design process of main parameters is supplied in detail.The results of the experiment certify the correctness of the series-parallel topologyand the feasibility of the control strategy.