Synchronous Carrier-based Pulse Width Modulation Switching Method for Vienna Rectifier

Abstract

This paper proposes a synchronous switching technique for a Vienna rectifier that uses carrier-based pulse width modulation (CB-PWM). A three-phase Vienna rectifier, similar to a three-level T-type converter with three back-to-back switches, is used as a PWM rectifier. Conventional CB-PWM requires six independent gate signals to operate back-to-back switches. When internal switches are operated synchronously, only three independent gate signals are required, which simplifies the construction of gate driver circuits. However, with this method, total harmonic distortion of the input current is higher than that with conventional CB-PWM switching. A reactive current injection technique is proposed to improve current distortion. The performance of the proposed synchronous switching method and the effectiveness of the reactive current injection technique are verified using simulations and experiments performed with a set of Vienna rectifiers rated at 5 kW.

Fig. 1. Topology of the Vienna rectifier.

Fig. 2. Modulation signals for the CB-PWM.

Fig. 3. Impedance angle of the Vienna rectifier.

Fig. 4. Equivalent circuit of the Vienna rectifier.

Fig. 5. Block diagram of the control scheme for the Viennarectifier.

Fig. 6. Currents and reference voltages for CB-PWM.

Fig. 7. Current flow in Region 1 with conventional CB-PWM.

Fig. 8. Current flow in Region 2 with the conventional CB-PWMswitching method. (a) SW1: ON, SW2: ON (O State). (b) SW1: ON,SW2: OFF (O state).

Fig. 9. Output voltages of the rectifier and correspondingswitching states in Region 2 with the conventional CB-PWMswitching method.

Fig. 10. Currents and reference voltages for the synchronousCB-PWM.

Fig. 11. Current flow in Region 2 with the proposed CB-PWMswitching method. (a) SW1: OFF, SW2: OFF (N State). (b) SW1:ON, SW2: ON (O state).

Fig. 12. Voltage and input currents of the rectifier during DCM.

Fig. 13. Output voltages of the three phases in Region 2 with theproposed CB-PWM method.

Fig. 14. Phase differences depending on the impedance angle andpower factor angle.

Fig. 15. Power factor based on impedance angle.

Fig. 16. Simulated currents and switching signals for theconventional CB-PWM.

Fig. 17. Simulated currents and switching signals for thesynchronous CB-PWM.

Fig. 18. Results of simulations performed using the proposedalgorithm for improving current distortion.

Fig. 19. Performance of the proposed method under distortedvoltage. (a) 5th: 3%, 7th: 2%. (b) 5th: 5%, 7th: 3%.

Fig. 20. Prototype of a Vienna rectifier used in the experiments.

Fig. 21. Experiment results in the rated load condition. (a)Conventional CB-PWM. (b) Proposed synchronous CB-PWM. (c)Proposed synchronous CB-PWM and optimal reactive currentinjection.

Fig. 22. Experiment results in 1 kW load condition. (a)Conventional CB-PWM. (b) Proposed synchronous CB-PWM. (c)Proposed synchronous CB-PWM and optimal reactive currentinjection.

Fig. 23. Variation of THDi based on switching methods.

Fig. 24. Variation of power factor based on switching methods.

Fig. 25. Efficiency according to switching methods.

TABLE I SI BASE POSSIBLE WITCHING STATES IN DCM

TABLE II SIMULATION PARAMETER