| The rapid development of industrial production puts forward higher requirements for the performance of power converters,and miniaturization and modularization are generally the development trend.However,due to the large switching loss of traditional hard switching rectifier,the switching frequency of power converter is still limited.With the increase of switching frequency,the problems of device stress,switching loss and electromagnetic interference are more prominent.The power converter based on soft switching technology not only improves the switching frequency,but also reduces the switching loss,reduces the equipment volume and improves the stability.Therefore,based on soft switching technology,this paper proposes two kinds of high efficiency rectifier topology circuits.In the second chapter,a high efficiency single-phase full bridge soft switching rectifier based on two-way switch assisted converter is proposed.The remarkable feature of the rectifier is that there are few auxiliary circuit devices,the structure is simple,the auxiliary devices are not connected in series on the main power transmission channel of the rectifier,which is conducive to reducing the on state loss of the auxiliary circuit and improving the efficiency of the rectifier.Moreover,the two-way auxiliary switch is used to trigger the auxiliary circuit to work,so as to realize the resonance capacitance of the main switch to be opened in parallel when the rectifier is in the dead zone state The two-way auxiliary switch can adopt fixed duty cycle control,which is beneficial to simplify the control.The topology proposed in the second chapter is only suitable for single-phase full bridge circuit,which contains a group of auxiliary resonant circuits with simple structure.However,it is difficult to ensure the capacitor voltage sharing at the DC output side.In general,additional voltage sharing circuits are needed to make the operation stable.In order to make the DC output side of the rectifier without voltage sharing capacitors,a three-phase bridge zero current is proposed in the third chapter The switch rectifier improves the power efficiency and ensures the stability of the circuit operation.The soft switch topology circuit proposed in the third chapter is based on the traditional three-phase bridge circuit.Each phase bridge arm is connected with a group of auxiliary resonance circuits in parallel.The remarkable advantage is that the switch device can realize zero current soft switching,eliminate the switching loss caused by the trailing current of IGBT,and further optimize the efficiency of the three-phase bridge rectifier with IGBT as the switch device.In this paper,the work flow and the wave form of each flow of the two topology circuits are analyzed in detail.The dynamic analysis of the rectifier is established by using differential equation and phase plane analysis method.The realization condition of soft switch,the loss of auxiliary circuit and the design of parameters are analyzed in detail through the mathematical model,Finally,the simulation software MATLAB is used to verify the simulation results.The simulation results show that the two rectifiers proposed in this paper can achieve soft switching,and improve the efficiency of rectifiers. |
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