| Modular multilevel converter is widely concerned and studied because of its advantages such as highly modular structure and easy upgrade of voltage level.In this paper,MMC rectifier is the research object.The research status of the key technical problems of high power rectifier based on MMC modulation strategy is introduced and analyzed.Through the construction of single-phase MMC rectifier simulation system and experimental prototype,key technical problems of MMC topology such as start control,double loop control strategy,sub module capacitor voltage balancing strategy and circulation suppression strategy are studied.The topological structure and working principle of high power rectifier based on MMC are analyzed detailedly.The equivalent mathematical model of single-phase MMC rectifier is established.On the basis of these research,key techniques of MMC rectifier are studied.Specific modulation strategy and the control scheme are proposed.The design method of the capacitance and inductance parameter in the main circuit are analyzed and proposed.In oeder to verify the control method designed in this paper,a single-phase five level MMC rectifier system is build based on the saber simulation software.The steady state and dynamic performance of the control system is simulated and analyzed.The feasibility and performance of the control scheme designed in this paper are verified.The experimental prototype of the rectifier based on MMC is designed in detail,including the hardware architecture design,DSP+FPGA+CPLD control system design and so on.The results of the theoretical research and simulation analysis are verified and analyzed on the experimental prototype of MMC rectifier.The results show that the designed control strategy effectively balances the capacitor voltage of the sub modules,the circulation is inhibited,the stability of the DC voltage is controled and the requirements of the unit power factor is realized. |
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