Under the c ondition of t hree-phase unbalanced load in micro-grid, three-phase four-leg inverter can solve the unbalanced three-phase output voltage because of unbalanced load. Nevertheless, in the dq0 synchronous reference frame, the output voltage and current of three-phase four-leg inverter are coupled with each other. If the load is unbalanced and the open-loop control is directly used in the dq0 synchronous reference frame, the output voltage is still unbalanced because of double frequency disturbance caused by unbalanced load. To solve these problems, this paper established the mathematical model of three-phase four-leg inverter, derived the open-loop transfer function of the controlled plant and deeply analyzed the mechanism of unbalanced output voltage of three-phase four-leg inverters. In addition, according to the system model information, a second-order active disturbance rejection controller(ADRC) controller was designed to decouple the voltage and current in dq axis, and it could reduce the number of originals measured. Proportional resonant controller was introduced to eliminate the disturbance caused by 100 Hz. Finally, the effectiveness of the solution was verified by Matlab/Simulink.
Power Generation Technology
three-phase four-leg inverter
dq axis decoupling
active disturbance rejection controller(ADRC)
proportional resonant controller