AC Voltage Sensorless Predictive Duty Cycle Control of a Five-level Unidirectional Rectifier

In this article, a predictive duty cycle control strategy for a five-level Dual Flying Capacitor-Active Neutral Point Clamped (5L-DFC-ANPC) unidirectional rectifier is proposed. The control objectives for this rectifier are to have (a) regulated line currents and (b) balanced FC and dc-link voltages. Discretized models for the dynamics of the line currents, FC voltages, and the dc-link voltages are developed based on the input current oriented reference frame. The optimized pulse width modulated (PWM) rectifier input voltages (and hence, the duty cycle of the switches) are predicted based on these models. Using this control strategy, unity terminal displacement factor can be obtained without using any ac voltage sensors. The effectiveness of the proposed control strategy is verified by the simulation results obtained from a 3MW, 3.3kV system.