Design and Comparison of High Performance Stationary-Frame Controllers for DVR Implementation

The performance of a dynamic voltage restorer (DVR) is determined solely by its controller. The design of high performance control algorithms for DVR control with improved robustness and desirable steady-state and transient characteristics is therefore an important area of study. In this paper, two voltage controllers are proposed in the stationary frame for DVR voltage regulation. A P+resonant controller is first designed to achieve good positive- and negative-sequence fundamental voltage control with the virtue of having high gains around plusmn50Hz. Stationary-to-synchronous frame transformations carried out in traditional synchronous proportional-integral regulators are no longer required with this method. However, with the purpose of achieving explicit robustness in face of parameter variations, an Hinfin controller is also designed. Detailed design procedure is presented to show how an Hinfin controller with high gains around plusmn50Hz can be synthesized through careful selection of its weighting functions. A thorough discussion and performance comparison of these two controllers in both transient and steady-state conditions are also carried out. Finally, both controllers are extensively tested on a laboratory 10-kV medium voltage level DVR system with various voltage sags and loading conditions