H-bridge cascaded active power filter and control method thereof

The invention discloses a control method of an H-bridge cascaded active power filter. The control method is designed aiming at solving the problem of low accuracy because of asymmetrical voltage in the existing method. The control method comprises the steps that: nonlinear load current is detected to obtain an expected compensating current value; the reference current value of the active power filter is obtained; the active power filter outputs current to track reference current; and the trigger signal of a cascaded H-bridge power device is obtained through carrier phase-shift pulse width modulation to drive a main circuit power device. The method for detecting the nonlinear load current is an improved synchronous reference coordinate system detection method based on fundamental-wave positive sequence voltage phase locking. The invention additionally discloses the three-phase star-connected H-bridge cascaded active power filter, wherein the capacitance and the voltage of a filter unit are controlled through a voltage controller, and the on and off of a power switch is controlled through a pulse width modulation strategy to adjust an equivalent resistance value. Under the situations that power voltage is asymmetrical and is distorted, the compensating current required by a load can be accurately detected.