Capacitors Voltage Ripple Complementary Control on Three-Level Boost Fed Single-Phase VSI With Enhanced Power Decoupling Capability

Abstract

Power decoupling is always a strong desire for single-phase voltage source inverter (VSI) due to the inherent double-line (2ω) frequency ripple caused by the instantaneous power unbalance between dc- and ac-side. The existing solutions either apply a large capacitor or employ a small power converter to compensate it, which inevitably increases the system cost and control complexity. To overcome these drawbacks, this article performs the transient modeling analysis and it reveals that 2ω frequency power component in the converter achieves minimum value when the inductor current ripple is minimized. A novel capacitors' voltage ripple complementary control algorithm based on three-level boost fed single-phase VSI is proposed. By mitigating the 2ω power component from the inductor and redistributing the stored energy between two intermediate series-connected capacitors, the oscillating power is absorbed with notably eliminated input current ripple and significantly reduced dc-link voltage ripple. Thus, the good power quality of both dc- and ac-side is guaranteed. Furthermore, the total capacitance requirement is minimized under the given dc-link ripple tolerance without any more electric stress increment and lifetime reduction. Simulation and experiment results verify the theoretical analysis and proposed control method. It is promising in applications, where both input current ripple is strictly limited and ac output voltage quality is highly required with small dc-link capacitance.