Split-Capacitor Self-Balancing of Single-Phase Half-Bridge Inverters

This paper uncovers the mechanism of the unbalanced split capacitor voltage caused by the deviation of the sensing signal. For the single-phase half-bridge (SPHB) inverter, the deviation of the sensing signal will lead to an offset on the output current and further causes the deviation of split capacitor voltage. However, this unbalance capacitor voltage will help to compensate the output current offset. Consequently, the capacitor voltages will drift to a certain stable voltage level, which is commonly called the self-balancing effect. This paper presents the precise mathematical equations by analyzing the self-balancing mechanism and accurately predict the value of capacitor voltage variations. Computer simulations and hardware experimental results of a 1kVA SPHB inverter are shown to verify the accuracy of the mathematical equations.