Development of low-voltage intelligent compensation device with high accuracy used in distribution substation

Abstract

In response to the problems of the three-phase unbalance and the large grouping capacity of low-voltage reactive power compensation devices in the low-voltage distribution stations, as well as the inaccurate coordination between capacitor switching and zero-crossing point, the precise zero-crossing switching control method considering grid frequency and magnetic holding relay action time is proposed in the paper. The precise compensation capacity of capacitors is designed, and the low-voltage intelligent compensation device with high accuracy is developed. After testing, within the frequency range of 45-55Hz in the power grid, the time error between the input and output of the magnetic holding relay is within 100us, and accuracy of reactive power compensation can reach 1kvar. The low-voltage intelligent precise compensation device is fast and reliable in the distribution network. With the flexible configuration number, the device can accurately achieve the voltage zero-crossing capacitor input and the capacitor current zero-crossing cutoff. This device has small impact on the power grid, safe and reliable operation effect, and expands the application range.