多台电力电子变压器云-边脉宽调制同步控制策略

The cloud-edge signals based PWM synchronization strategy for multi-power electronic transformer

电力电子变压器(PET)单机功率较低,实际应用中常采用多台PET并联运行模式。多台PET运行时存在高频谐波交互现象,导致输出的高频谐波幅值上升,影响电能质量的同时威胁PET的运行安全。为提升多台PET的高频开关谐波协同控制能力,提出一种多台PET云-边脉宽调制(PWM)同步控制策略:当通信系统正常运行时,PET利用云端同步信号实现高精度PWM同步;当通信系统故障时,PET可利用边端计算结果实现高可靠PWM同步。研究结果表明,该策略能兼顾PWM同步的精度与可靠性,保证高频率开关谐波协同控制,避免多台PET运行时的高频谐波交互。因无需增加硬件,该策略易于推广应用,有利于在提高电能质量的同时降低PET的故障率。

Due to the limited rated power of individual power electronic transformer(PET),many PETs are always connected in parallel in practice.High-order harmonic interactions occur when PETs are in operation,resulting in a rise in the amplitude of the output high-order harmonics.Thereby,the power quality is influenced.The safety of PETs is also threatened by the high-order harmonics.In order to control the switching harmonics among the parallel PETs,a pulse width modulation(PWM)synchronization strategy based on the mixed information which is the combination of cloud signals and edge signals is proposed in this article.The basic idea has two parts.Firstly,the PWM synchronization is realized according to the cloud signals when the communication system works well.Secondly,the realization of PWM synchronization is switched to edge signals during the communication faults.It is proved that the high-precision and high-reliability can be guaranteed by the proposed strategy.The high-order harmonics can be coordinated-controlled well.Doing so,the interaction of high-order harmonics among PETs can be eliminated.The proposed strategy can be easily implemented due to limited requirement of additional hardware.With using the proposed strategy,the power quality and the reliability of PET can be improved.