Research On Topology And Control Of Three Phase Soft-switching Inverter

Three-phase PWM inverter device is widely applied in power conversion.It can not be ignored that the conventional inverter has low power density,large switching loss and poor reliability.The application of the resonant technology not only makes the three-phase PWM inverter with high power density,low switching loss and high switching frequency,and also makes it achieve the purpose of miniaturization and light weight.Therefore,the three-phase soft-switching inverter has become a new show in the power electronic converter.In this paper,the topology of two new types of soft-switching inverter,represented by the type of resonant DC link and resonant AC link,is studied.The working mechanism of the soft-switching of both circuits is deeply analyzed.A virtual zero voltage vector modulation method and a Grid-connected control strategy are established in the two circuits.The results show that these two kinds of circuits can keep soft-switching under any power factor.Generally,the auxiliary resonant circuit of the resonant DC link inverter is located in the main power transmission channel.Most of the resonant components of the DC-Rail ZVT inverter studied in this paper are removed from the main power channel.Only when resonance occurs,the resonant network is put into the main circuit,which further reduces the loss of the additional resonant network.In addition,the virtual zero voltage vector modulation method equivalent to the traditional SVPWM modulation is used to minimize the number of times of resonance in each switch cycle,which greatly reduces the zero-voltage groove on the DC bus and makes full use of the DC voltage utilization.The new RP ZVT inverter in this paper has no neutral-shift problem,and the auxiliary resonant circuit is simple.The soft-switching action is achieved under any power factor by using the same virtual zero voltage vector modulation method.Owing to the constant DC bus voltage in this topology,the efficiency of the whole machine is greatly improved.Finally,the simulation and results of DC-Rail ZVT PWM three-phase inverter and RP ZVT PWM three-phase inverter are verified and analyzed.The correctness of the topology and control strategy is confirmed,and the purpose of realizing the soft-switching action of all power switch devices is achieved.On this basis,the loss estimation and efficiency comparison of these two kinds of soft-switching circuits are carried out.The results show that the soft-switching circuit has obvious advantages in improving efficiency.