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

Abstract

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.

Keywords

• power electronic transformer (pet)
• multi-machine operation
• parallel operation
• pulse width modulation (pwm)
• cooperative control
• cloud-side collaboration