Reactive Power Control of Critical Mode-Based Soft Switching Modulation for Three-Phase Bidirectional AC-DC Converters
Based on the novel critical mode-based soft switching modulation proposed in previous work on bidirectional three-phase ac-dc converters under unity power factor conditions, the control concept is extended to bidirectional, non-unity power factor conditions. A generalized critical mode-based soft switching modulation is also proposed which is applicable to both inverter and rectifier modes during unity power factor and non-unity power factor conditions. With this generalized modulation, ZVS soft switching and narrow switching frequency variation ranges are still achievable.
Fig. 1 shows the switching cycle waveforms under a non-unity power factor condition, with the proposed generalized modulation at two arbitrarily selected intervals during CRM operation. This verifies that ZVS soft switching is achieved.