Control of Power Electronic Converters
Technical Dialogue Session
Three-level inverter, paralleled inverter, circulating current, space vector modulation
In paralleled three-phase three-level voltage source inverters, sometimes the currents of paralleled inverters need to be separately adjusted to control power sharing, and the reference vectors will differ in phase and amplitude. In other cases, although the current references of the paralleled inverters are set to be the same, the d-axis and q-axis current closed-loop control outputs of each converter cannot be exactly the same due to the asymmetry in hardware or software. As a result, the reference vector of each inverter may also be different in terms of phase and amplitude. When conventional three-level space vector pulse width modulation (SVPWM) is applied, periodical jump can be observed in the phase current of each inverter and the zero sequence circulating current (ZSCC). This paper investigates the current jump phenomenon in paralleled three-level inverters with space vector modulation (SVM). The mechanism that causes the current jump is illustrated. A modulation method to eliminate this current jump is proposed. Simulation and experimental results are presented to verify the effectiveness of the proposed method and conducted analysis.