Simulation Research on Neutral Point Voltage Balance Control Strategy of Three-level Frequency Conversion System

For the participation of the neutral point potential of the three-level inverter in energy transmission, it will bring the problem of inconsistent voltages of the two voltage-dividing capacitors. In this paper, changing the action time of the small vectors can control the neutral point voltage without changing the output voltage, that is, detecting the voltage magnitude of the DC side capacitors, and then, according to the deviation direction of the neutral point voltage, reasonably arranging the action time of the positive and negative small vector PWM pulses for neutral point voltage compensation. Through modeling and simulation analysis, the results show that this control method can maintain the neutral point voltage balance without going through complex logical judgments.