Research And Realization On Control Strategies Of Cascaded High-voltage Converter

Now, cascaded high-voltage converter is one of the hotspots in the power electronic field. It has many merits as follows: input side has less pollution to the electrical net;output voltage approaches to sine wave so that it doesn't need output filter;structure is simple and easy to be modularized;control method is easy to be realized and so on. These merits make cascaded high-voltage converter 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:1 Cascaded high-voltage converter's basic topology is analyzed. The multi -plexing rectify circuit and invert circuit are explained in detail, and the traditi onal cascaded converter commonly used nowadays, as well as mixed cascaded2~N and 3~N invert structure are mainly introduced.2 The control methods of high-voltage converter are researched. Based on carrier phase shifting SPWM, another method which is easily to be realized —synchronous carrier phase shifting SPWM is proposed. Line voltage controlled SPWM and quasi-optimized PWM are introduced into carrier phase shifting SPWM and multi-carrier SPWM strategy is also researched.3 For the MATLAB soft ware, the models of the control strategies above are established and these results are analyzed and compared.4 The circuit in the case of fault of power unit is analyzed. Study shows that when fault appears, the output of the fault of power unit is not only closed off, but also removed from the system. Furthermore, correspond methods to deal with some main faults are proposed, such as: over current, over voltage and lack voltage in the DC side, overheat and over load.5 According to the characters of the system, the scheme for cascaded high-voltage converter is designed.