Power Efficiency and Power Density Enhancement of Pure Sinusoidal Output Single-Phase Multilevel Current-Source Inverter Using Class-A Amplifier-Based Current Compensator

In the previously developed pure sinusoidal output single-phase current-source inverter (CSI), a conventional multilevel current-source inverter was successfully combined with a linear amplifier to realize a hybrid multilevel current-source inverter. Linear amplifier utilization was performed to reform a staircase multilevel current waveform into a pure sinusoidal current one by using a superimposition technique. To obtain very low harmonics by only using a small output filter capacitor, a class-A linear amplifier was utilized as the current compensator. However, this hybrid multilevel CSI must be applied in a high number of levels to achieve an acceptable power efficiency. Consequently, the system requires the use of many current modules that leads to a high semiconductor device count. Excessive semiconductor devices utilization, in turn, leads to performance deterioration due to switching and gate charge losses, and also decreases the power density of the system. Therefore, the recursive multilevel technique is proposed to handle the current module activation sequences, such that the high number of levels in the multilevel CSI can be constructed by only using a small number of current modules. The simulation and experimental results confirmed the applicability of the proposed technique with some advised discretions.