A new analysis method for compensation strategy of DVR and minimum energy control

The compensation strategy of the dynamic voltage restorer (DVR) has significant impact on the compensation result. A new analysis method which is based on pre-sag load voltage is proposed in the paper. The new method chooses the pre-sag load voltage phasor as the reference phasor and put the centre of the limit compensation voltage circle at the terminal of the system voltage phasor. It not only has definite physical concept but also is convenient to determine the compensation range. More importantly, it could be applied to unbalanced load. The basic theory and process of the new method was explained and compensation strategy of the three-phase DVR was analyzed. Using the new method, the minimum energy compensation strategy was realized through the simulation when unbalanced voltage sag happened in the case of the unbalanced load. The conditions for zero active power compensation was also analyzed which could prolong the compensation time of DVR. The simulation result shows the correctness of the theoretical analysis.