| In recent years, with the development of PWM inverter, there have been radical changes on the design of power converter. It has been changed from heavy and enormous power frequency transformer to light and small density power converter, and the whole efficiency of converter has been greatly improved too. These changes will benefit the design and application of PWM inverter. However, with the rapid development of China's industry and the increase of energy demand, highly effective energy-Saving inverter becomes the focus of research.Traditional inverter technology is mature, reliable, widely applied, but there are some disadvantages such as large on size, big audio noise, poor system dynamic characteristics, etc. Soft-switching technology is regarded as an advanced technology in the design of power inverter. In order to solve traditional snubber's disadvantages of circuit loss, the lossless soft switching technology is proposed. Lossless soft switching technology can be separated into passive lossless soft switching technology and active lossless soft switching technology, depending on whether the active switch exists or not. Though active losses soft switching technology can reduce switching loss, the structure and the control are complex. Passive lossless soft switching technology just adds some passive components into converters to transfer and feedback energy to reach the lossless effect. While, passive lossless soft switching technology can not only reduce switching loss and noise, but also have simple circuit, low cost, and high reliability, so it receives widely focus and study in recent years.Soft switching inverter, which controls resonance process by auxiliary switching device, has complex control model and difficult implementation. So an absorption soft switching topology is studied in this thesis. It makes main switching device on under zero-current and off under zero-voltage. The characteristic of such circuit topology is that the upper and lower tubes of the bridge arm share the same reanalyzing absorption inductance and turn-off capacitance. On the basic of optimizing main absorption structure, a spot of inductance and diode elements are added, which realizes the minimization of additional elements. Furthermore, capacitance-structured voltage source makes energy feedback and the restoration of absorption elements come true.The thesis summarizes the improvement and present situation of soft switching inverter technology based on reading and studying on a lot of relevant literature. The main study works are as follows:Firstly, a passive lossless main circuit topology of three phase PWM inverter is analyzed. According to each state of switch tube, the thesis analyzes the working principle and working process of this topology, establishes mathematical model and solves the main parameters value. Based on the theory analysis, the thesis verifies that the circuit can realize soft-switching of switch device and realize energy feedback, thus provides a theoretical basis for subsequent studies.Secondly, the control strategy of PWM is designed through analyzing the soft switching working condition of this circuit. Only if modulation depth fits in with the condition of zero-voltage-switching and zero-current-switching, soft-switching of switch tube can be realized. A follow-up simulation study of three phase passive and lossless soft switching inverter is made. Comparing with the simulation result of traditional inverter and analyzing the stroboscope of the structure, the correctness of control strategy is verified.Finally, some existing problems in theoretical study and practical application are pointed out, and the prospect of research work of next step is presented in the thesis.
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