| The cells in series multi-level high voltage frequency converter (CSHVFC) is one of the hotspots in the power electronic field now. It has many merits as follows: input side has less pollution to the electrical net; output voltage approaches to sine wave so that it does not need output filter, structure is simple and easy to be modularized; control method is easy to be realized and so on. These merits make CSHVFC to be widely used in the electric drive field, especially for blower fan and water pump which require lower timing capability. For blower fan and water pump load, cascaded topology is as the basic structure of high-voltage converter in this paper. Concretely speaking, the main contents in this paper are as follow:Base on the analysis of operation principle for the cascaded inverter, the modulation principle of carrier-based Phase Shifted SPWM (PS SPWM) has been explained in detail, and the superiority of harmonic elimination under this SPWM modulation has been demonstrated also. The advantages of the PS SPWM applied in the cascaded inverter were also presented.Analyzed some basic topology of high-voltage converters and compared their excellence and defect. Then, accord to actual situation, the researching project-the CSHVFC was ascertained.Based on dislocation phase shifting, the system circuit design of CSHVFC is introduced which included phase-shifting transform power, the main part of power unit and control system. CSHVFC uses many power cells in series to form the high-voltage output, but each unit needs a dislocation phase shifting type SPWM pulse to carry on the control. In order to produce the real-time SPWM pulses, the logical component"Field Programmable Gate Array-FPGA"is used.The hardware was debugged. The results proved the feasibility and applicability of the PS SPWM modulation strategy. These works will make bases for next study in the control scheme and modulation strategy of cascaded inverter's application. |
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