A novel SVM algorithm for reducing oscillations in cascaded H-bridge multilevel inverters

Cascaded H-bridge inverters have been selected as one of the preferred power converter topologies for high-voltage, high-power applications. However, undesired oscillations could occur in the H-bridge inverter drive system particularly under light load conditions, which would cause high voltage or current stress on the motor and inverter. In this paper, the mechanism of the oscillations is analyzed and a novel mitigation method is proposed. The mitigation involves a simple inverter output voltage adjustment in the space vector PWM control in real time, such that the oscillation loop would be broken, leading to effective suppression of the oscillations. The proposed method features simple algorithm and easy implementation requiring only one voltage measurement per phase for any level H-bridge inverter. Simulation and experimental results are provided to demonstrate the efficiency of the method.