The invention provides an unbalance compensation control method of a cascaded power electronic 
transformer, comprising a control component and a 
transformer, wherein the 
transformer is composed of aninput 
rectifier stage, an isolation stage and an output 
inverter stage. The input stage is a three-phase star-connected cascaded H-bridge 
rectifier, the isolation stage is a plurality of independent dual-active-bridge 
converters, and the output stage is a single-phase 
PWM inverter. The control method of the present invention includes an input 
rectifier stage stratification 
control unit, a voltageclosed 
loop control unit of an isolation stage and a 
constant voltage and 
current sharing control unit of an output 
inverter stage. The input rectifier stage stratification 
control unit, is further divided into an upper control unit and a lower control unit, wherein the upper control unit is composed of a coordinate transformation, a positive sequence decoupling control and a 
negative sequence current suppression, and the lower control unit is an in-phase 
voltage sharing control. The control method provided by the invention can simultaneously solve the 
negative sequence current compensation problem of the PET when the 
voltage at the network side and the three-phase load are unbalanced, thereby promoting the application of the power electronic transformer in the 
engineering practice.