A Common-Mode Voltage Mitigation Method Based on the Universal PWM Algorithm for Neutral Point Clamped Converters

In this paper, a new method to mitigate the common-mode (CM) voltage in neutral point clamped (NPC), three-level converters is proposed by analyzing the voltage vectors and related CM voltages. Currently, only 19 of 27 available voltage vectors are used in order to reduce the amplitude of CM voltage to be one sixth of the dc-link voltage. This is achieved by adding a constraint to the universal, multilevel PWM algorithm proposed by an earlier paper. The constraint will determine the value of the zero-sequence component adding to the fundamental component, thus selecting of the required voltage vector. Simulation and experimental results validate the proposed method, and show that the CM voltage is effectively mitigated and the maximum output voltage is not affected.