Voltage measurement method based on three phase instantaneous point

The invention relates to a voltage measurement method based on three-phase instantaneous points. The method has high efficiency in rapidly determining the declination or swell of voltages by calculating the effective values of voltage or current by simple calculation according to the relationship among instantaneous values of three-phase components by using the characteristics three-phase symmetrical structure or near symmetrical structure without increasing additional transducer. By sampling instantaneous points, the invention shortens the time of the determination process, however, the common voltage measurement method can obtain the effective values in at least one sampling period. Accordingly, the instantaneous value calculation method shortens the response time and simplifies the calculation. The method is very effective in occasions for rapidly determining voltage such as dynamic voltage restorer. The method improves the dynamic response characteristics of a dynamic voltage restorer system.