Reduce Response Time of Single-Phase Dynamic Voltage Restorer (DVR) in a Wide Range of Operating Conditions for Practical Application

Voltage sag is one of the most serious power quality (PQ) problems for many loads; thus, the dynamic voltage restorer (DVR) is developed to mitigate the impact of voltage sag. However, in the practical application nowadays, according to the recent survey, for many sensitive loads, the requirement on the response time of the DVR has been even stricter (shorter in a wider range of operating conditions). Focusing on the single-phase system, the study on reducing the response time of the single-phase DVR in a wide range of operating conditions is introduced in this article. Considering the state of the art, key approaches and ideas to reduce the response time of the DVR in a wide range of operating conditions are discussed, based on which a fast detection method for the grid voltage sag based on the comparisons [combined with bool signal filters (BSFs)] of the multitimescale variables of the restructured voltages, as well as a fast and reliable commuting strategy for the bypass thyristors in the DVR based on the double-voltage-step method, is proposed in this article. The proposed detection method is capable of detecting the grid voltage sag with the time delay about 0.75 ms in a wide range of operating conditions, and the proposed commuting strategy is capable of fast turning off the bypass thyristors in the DVR reliably even with the unreliable sampled current. Then, with the widely used double-closed-loop control with double feedforward, the response time is achieved less than 3 ms in a wide range of operating conditions in a prototype of the single-phase DVR, verifying the feasibility and the performance of the proposed detection method and the commuting strategy.