A study on the DC voltage control techniques of cascaded multilevel APF

For its significant advantages on topology and control techniques, cascaded multilevel inverters has been widely used in the studies of APF (Active power filter) in recent years. The control difficulty of this type converter lies in its DC capacitor voltage balance. Many papers adjust active voltage to solve this problem. But due to the delay of the PI module in these control strategies, a certain phase difference occurs between the actual current and the reference current, affecting the real-time current tracking effect and capacitors balance performance. This paper proposed a novel balance control method that uses the direct current control with transient power regulation for each H-bridge cells to achieve phase to phase and inside phase DC capacitors voltage equilibrium. This method is simple and easy to be implemented. Simulation and engineering results verified the excellent DC capacitors balance performance.