Medium-voltage level dynamic voltage restorer compensation strategy by positive and negative sequence extractions in multiple reference frames

This paper presents a new compensation strategy based on the instantaneous reactive power theory which can be used in the dynamic voltage restorer (DVR). This strategy uses a multiple DQ transformation with separation modules to extract the positive and the negative sequence components from the fundamental and the harmonic waves so as to analyse and adjust each component separately. As a result of this new strategy, the dynamic response and the tracking accuracy are improved and the fluctuations of the DQ components are decayed. To verify its effectiveness, a cascade DVR simulation model has been built in MATLAB/SINMULINK and a series of simulations have been performed. The results show that the DVR is competent to make a better compensation with this new strategy in the case of the complex conditions such as sags, harmonics and unbalances. The compensation strategy is tested by a 10 kV/500 kVA voltage drop generator test rig and the experimental results validate that the strategy can improve the dynamic response and obtain a high accuracy in both the dynamic and the steady states. Therefore the strategy has potential engineering application values.