A Novel Switching Vector Sequencing Method to Optimize DC Voltage Ripple in Dual Inverter Drive Without Affecting Load Current Ripple

In voltage source inverters (VSIs), the pulsewidth modulation (PWM) techniques of the inverter generate the load current ripple and dc voltage ripple. This work thoroughly analyzes the switching state correlation to optimize the dc voltage ripple without affecting the ac current ripple. The analysis revealed that the switching algorithms must act to place the switching states by computing instantaneous dc capacitor current polarity. Using the polarity information, this work proposes the novel PWM dynamic sequencing mechanism that independently places the null and active vector in the sampling time interval to accomplish the optimum dc voltage ripple. Unlike conventional PWM methodologies, a prior capacitor current polarity computation makes the proposed algorithm dynamic in realizing the optimum switching sequence at any load condition without influencing the load current ripple. Further, the proposed method identifies the dwell times from the instantaneous phase reference voltages, freeing the algorithm from complex dwell time computations and sector identification. Therefore, the proposed methodology is simple in realizing variations in PWMs by simply shifting/segregating the null time. Further, it is demonstrated that discontinuous PWMs with low current ripple can yield the lowest voltage ripple with the proposed sequence; otherwise, it is the highest among all other PWM variants.