Novel modulation method for common-mode noise reduction in Solid-State Transformer based on ISOP configuration

This paper proposes a modulation method for the reduction of the common-mode noise in Solid-State Transformer (SST) with the ISOP connection. Modular multilevel configurations based on the ISOP connection increase the common-mode noise path because of increasing the switching components. Moreover, the cancellation of the common-mode noise using active common-mode canceler is not able to be applied because of complex common-mode noise path in SST with the ISOP connection. In the proposed method, one of the cells is driven by PWM in order to compensate for the harmonic component. The other cells are driven by square-wave operation in order to share the load. Therefore, the common-mode voltage is suppressed by the switching state of PFC. The advantage of the proposed method is that the additional EMC filter is not necessary for the reduction of the common-mode noise. The operation waveform with the proposed method is shown in the experimental results. The conducted emission is reduced by 11 dB and 7 dB in 200 kHz-band and 1 MHz-band, respectively.