一种减小三相级联型PET各中间直流侧电容的方法

摘要

三相级联型电力电子变压器(PET)因其模块化和可扩展性而得到广泛应用,但其中间直流侧中限制功率波动的大电容会降低其功率密度.为解决这一问题,提出一种基于DC-DC谐振变换器的三相级联型PET正弦功率传输概念,以减小中间直流侧电容,将交流侧2倍频率的功率波动传递到公共直流侧,并保证了恒定的直流电源.当谐振变换器工作在近似谐振模式下时,可以简单有效地实现正弦功率传榆概念,并简化PET控制结构实现单级控制.虽然PET的正弦传输只有较小的功率因数调节能力,但是它可以有效地减小单向功率传输的PET的电容和制造成本.研制并测试一台样机,实验结果验证了对于基于DC-DC谐振变换器的三相级联型PET正弦功率传输的可行性.%The three-phase cascaded PET(Power Electronics Transformer) is widely applied due to its modularity and expandability,but its intermediate bulk DC-link capacitors for limiting power fluctuation may reduce its power density.To solve this problem,the SPT(Sinusoidal Power Transfer) concept is proposed for three-phase cascaded PETs to reduce the intermediate DC-link capacitance,transfer double-frequency AC-side DLF(Double-Line-Frequency) power fluctuation to the common DC side and maintain the constant DC power supply.When the resonant DC-DC converters operate in the quasi-resonant mode,the SPT concept is simply and effectively realized,and the PET control system structure is simplified to a single-stage control system.Although the SPT for PET has small capability of power factor control,it is a new trend for unidirectional PET to effectively reduce the volume and cost.A hardware prototype is designed and tested.The experimental results verify the feasibility of applying the proposed SPT concept to three-phase cascaded PETs with DC-DC resonant converters.