Switching Strategy of Electronic Divider for Hybrid On-load Tap Changers Based on Zero-crossing Signal

This paper presents an expanded electronic divider for the hybrid on-load tap changers, and the associated switching strategy to determine the make and break of the power electronic devices is proposed. Depending on the state of the thyristor, the switching process of the studied design can be divided into three stages, and the equations of signal waveform in each stage are derived in detail. In this way, the variation of the waveform parameters, such as withstand voltage and flow capacity, along with the operating conditions can be illustrated quantitatively. Result analysis shows that the zero-crossing instant of the voltage across thyristor to be turned on is an effective timing for a continuous commutation between the electronic devices. The robustness and effectiveness of the proposed strategy has been validated by means of simulation tests.