Three-Phase VIENNA Rectifier Interval Control Strategy to Improve Light Load Performance

The three-phase VIENNA rectifier operates in a low-power standby mode for a long time, where fluctuations in the DC output voltage will lead to reduced system performance and reliability. Therefore, stability in light load conditions is crucial. Due to the unidirectional feature of the VIENNA rectifier, as long as the switching device is turned on, energy will be transferred from the AC side to the DC side. Inserting zero level signals with intervals in the duty cycle is proposed to reduce the average, thereby reducing the switch-on time while maintaining the sinusoidal characteristic. The proposed light load interval control strategy designs a criterion voltage to be compared with the absolute value of the grid voltage for inserting zero levels. Moreover, a function relationship between the criterion voltage and the current reference is constructed to dynamically adjust the zero level duration. The proposed strategy does not rely on the DC-side current sensor to determine the operating state, which has advantages in terms of cost and simplicity. To verify the validity of the proposed strategy, a 50 kW VIENNA rectifier prototype is designed and built. The experimental results show that the output voltage ripple at 1.2kW, 720W, and 100W is about 12V, 7V, and 0V, and the ripple rate is 2%, 1.16%, and 0. The experimental results show that the proposed method can control the DC voltage to remain stable, effectively improving the dynamic and steady-state performance under light load.