A Novel Control Strategy Based on Natural Frame for Vienna-Type Rectifier Under Light Unbalanced-Grid Conditions

In order to reduce the dc-link voltage ripple and the dc component of the reactive power under unbalanced input conditions, a novel natural-frame-based control scheme for a Vienna rectifier is proposed in this paper. First, by applying an early-developed direct decoupled synchronization method, the fundamental positive/negative-sequence voltage components are derived. Then, a natural-frame-based current control loop is designed based on the mathematical modeling of the Vienna rectifier under unbalanced input conditions. Based on the natural abc frame, the proposed control scheme considerably reduces total algorithm complexity and helps reduce the dc reactive components and total loss in comparison to the traditional dual-hybrid current control schemes. In addition, the stationary operation region of the Vienna-type rectifiers is analyzed, and the scheme is claimed to work out of the stationary operation region with severe voltage unbalance. The dynamic response of unbalanced input is presented. The experimental results are given to demonstrate the effectiveness of the proposed control scheme. In addition, the performance comparison between the traditional controller and the proposed controller is given by experimental results.