Due to load imbalance

the dc-link capacitor voltage imbalance problem will occur in the actual operation of cascaded H-bridge rectifier. To solve the problem of dc-link voltage balance under unbalanced load

we put forward the range of load imbalance within the dc-link reference voltage. In order to reduce the complexity of the phase-locked loop to the system control

the lockless loop control structure is adopted. Through in-depth study of the two-dimensional control algorithm

the voltage waveform of two-bridge modulation wave is deduced. Then

according to the principle of power balance

the load unbalance limit range is deduced when the system is under unit power factor. Meanwhile

the reference range of dc-link voltage is given. The simulation and experiment results have verified the validity and effectiveness of dc-link reference voltage selection range and the load imbalance limit range

which provides an important basis for the design of cascaded H-bridge rectifier system parameters.