Dynamic Voltage Restorer Utilizing a Matrix Converter and Flywheel Energy Storage

A new series power-conditioning system using a matrix converter with flywheel energy storage is proposed to cope with voltage sag problem. Previous studies have highlighted the importance of providing adequate energy storage in order to compensate for deep voltage sags of long duration in weak systems. With the choice of flywheel as a preferred energy storage device, the proposed solution utilizes a single ac/ac power converter for the grid interface as opposed to a more conventional ac/dc/ac converter, leading to higher power density and increased system reliability. This paper develops the dynamic model for the complete system, including the matrix converter in dual synchronous reference frames coupled to the flywheel machine and the grid, respectively. The dynamic model is used to design a vector control system that seamlessly integrates functions of compensating load voltage and managing energy storage during voltage sag and idling modes. The numerical simulation and experimental results from a laboratory-scale hardware prototype are presented to verify system performance.