Design considerations on the line-side filter used in the dynamic voltage restorer

The effects of harmonic voltages generated by the voltage-source inverter within a dynamic voltage restorer can be mitigated through the use of a line-side filter. However, injudicious design of the harmonic-filtering system can degrade the power-quality-enhancement capability of the restorer. Inappropriate filter design may also result in the need for the inverter current rating to be increased significantly. The purpose of the investigation is therefore to carry out a systematic analysis of the filter design by considering first the selection of the filter-capacitor on the basis of meeting a prespecified harmonic-performance criterion. The effect of the capacitor on the inverter rating is then evaluated and the method of determining the filter capacity is presented. An example, which involves electromagnetic transient studies, is included to demonstrate the efficacy of the proposed design method.