Control Strategy with Self Voltage-balancing of Cascade Converter

Abstract

The cascaded converter topology with series on the DC side and parallel on the AC side is currently a better choice for the converter of the DC system in the scenario of medium /low voltage and small capacity. Aiming at the problem of capacitor voltage-balancing on the DC side of the cascaded converter, a cascaded converter control strategy with self voltage-balancing function that can supply power to the passive/weak AC microgrid is proposed in this paper, including voltage/frequency control with self voltage-balancing and optimal droop control with self voltage-balancing. Compared with the traditional voltage-balancing strategy, this strategy can participate in the frequency regulation of the system, and the optimal droop control can also avoid the data communication between sub-modules(SMs). The simulation results show that the proposed strategy can realize the voltage sharing function under steady-state and various fault conditions, and can also participate in the frequency regulation of passive/weak AC microgrid to ensure that the system frequency does not exceed the safety threshold.