A Fast and Robust DC-Bus Voltage Control Method for Single-Phase Voltage-Source DC/AC Converters

Abstract

This paper presents a fast and robust dc-bus voltage control method for single-phase grid-connected dc/ac converters. The proposed technique precisely estimates the double-frequency (2-f) ripple of a dc-bus voltage and removes it from the voltage-control loop without adding any additional dynamics or oscillations. Conventionally, the 2-f ripple is managed by using large capacitors which increase the cost and bulkiness of a converter. As a state-of-the-art approach, a notch filter (NF) or a dc-voltage estimator is used to effectively block the 2-f ripple from the voltage-control loop, which can significantly reduce the capacitor size. However, such an approach introduces new dynamics in the control loop, causes additional oscillations on the bus voltage and increases the settling time of its response. This limits the degrees of freedom of the design to improve the overall system damping. The proposed method in this paper has no adverse impact on the original bus-voltage dynamic response. As a result, the bus-voltage control can be designed with higher speed and robustness and the whole system can operate with a reduced transient at both the bus voltage and the output ac current. The proposed approach is thoroughly analyzed and its effectiveness is validated through simulations and experimental results.