Sensorless power balance control for cascaded multilevel converter based solid state transformer

For the control strategy of cascaded multilevel converter based solid state transformer (SST), in order to solve the power unbalanced problem caused by mismatch of the parameters of each dual active bridge (DAB) module, power balance control strategy is proposed. This strategy uses the active power component of the duty cycle of each module of the multilevel rectifier as power feedback to adjust the duty cycle of each DAB module, and it can be easily realized by algorithms in DSP without current sensor. The strategy is verified through simulation and experimental implementation in a seven-level three-stage SST.