Phase-Shifted Modulation Strategy for Voltage Balancing in Neutral-Point Clamped Converter

This paper suggests a new method to balance the voltage of the two capacitors in the three-level neutral-point clamped (NPC) converter. The proposed method only needs the information of two capacitor voltages. The two capacitor voltages are fed back to the controller and then the controller generates phase shifting value with which sinusoidal modulation will be adjusted to the left or right. This method has upper and lower modulation signals. The outcome of the closed-loop is a phase compensation which will be applied to the upper and lower modulation signals. By applying the phase compensation in a different direction on the two modulation signals, this method provides voltage balancing. The new voltage balancing technique is verified by simulation and experimental results.