Research On A Novel Passive Soft-switching Inverter

The switching frequency of system continues to increase because of the requirements of miniaturization for inverters.The problems of high switching loss and low system efficiency have also appeared when the switching frequency is high.The soft-switching technology alleviates the problems above effectively.Passive soft-switching inverters are controlled easily,highly reliable leading to more suitable for practical applications among many soft-switching inverters.The existing passive soft-switching inverters use passive components for energy transmission,while ignoring the impact caused by the loss of the auxiliary snubber circuit existing in the practical circuits through the study of the past passive soft-switching inverters;Too many resonances occurred when energy absorbed by capacitors re-transferred to the capacitors through inductors during processing the energy absorbed after turning off the switches and transferred after turning on the switches.Although the voltage and current change rate of switches in the main circuit is decreased,the resonances of the auxiliary snubber circuit generate much electronic noises and raise the conduction loss of other passive components.The energy absorbed by snubber circuits stored in capacitors in form of voltage in papers presented before.As a result,the topology is complicated and the electrical stress of the switching elements in the topology is high.A novel type of passive soft-switching inverter topology is proposed in this paper to solve the problems above.The new structure can realize the zero-current turn-on and zero-voltage turn-off of the power switching elements.Only one resonance occurs in a switching cycle and loss reduced in the inverter.Taking inductors as the main components to absorb and release energy in the form of current during the power switches conducting,thus leading to a small number of components used in auxiliary snubber circuit and enhance the efficiency and reliability of the inverter.In this thesis,one phase of the novel passive soft-switching topology is analyzed in detail.A switching cycle is divided into different operating modes and the equivalent circuit of each operating mode is given.The mathematical equation of each operating mode is derived.The soft-switching conditions and the design of different parameters in the topology are discussed.Then the example of this novel topology is simulated,the open-loop and closed-loop system simulation model are built,completing the analysis and evaluation of the simulation results.Having verified the correctness of the principles of this novel passive soft-switching topology analyzed above and the rationality of the new structure after compmared with some soft-switching topologies.Finally,summary this thesis and put forward the next researching plans.