基于谐振式三电平半桥直流变换器的电力变压器拓扑结构

Power Electronics Transformer Topology and Control Scheme Based on Resonance Bidirectional Half Bridge Tree-level DC-DC Converter

针对现有的几种典型电力电子变压器(PET)拓扑结构对电网电压暂升骤降的变化抑制能力较弱,无法保证负载电压的恒定,提出一种基于谐振式双侧三电平半桥直流变换器的电力变压器拓扑结构。该系统输入级使用三相三电平PWM变换器,有效确保了交流电网输入的电流和电压维持波形正弦及直流侧电压恒定,功率因数可调,降低了电路元件的耐压等级。隔离级采用LC谐振式的半桥三电平DC-DC变换器,该变换器可有效降低电路损耗,提高电能质量。在此基础上,结合系统的工作特征在本系统输入级、隔离级和输出级引入闭环控制策略,提高了电路的稳定性,保证了系统的输出电压的恒定,抑制了输入级电压突变对输出的影响。仿真结果验证了该方案的可行性和有效性。

For the inhibition ability of several existing typical power electronic transformer(PET)topologies for grid voltage sag or swell is weak,which is no guarantee that the load voltage constant,a power electronics transformer topology and control scheme based on resonance bidirectional half bridge tree-level DC-DC converter was proposed in this paper.The input stage of the system employed three-phase three-level PWM rectifier converter to ensure effectively the input voltage and current purely sinusoidal and dc voltage constant,power factor adjustable,and reducing the voltage stress rating of components.The isolation stage used LC resonance half bridge tree-level DC-DC converter,which c can reduce effectively the wastage of the circuit and improve power quality.According to the working characteristics of the system,the closed loop control strategy was introduced into input stage,the isolation stage and output stage of the system,aimed to improve the stability of the circuit,ensure output voltage of the system constant as well as restrain the influence of abrupt changing of grid voltage for output voltage.Simulation results verify the feasibility and validity of the proposed PET system in this paper.