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 45-55 Hz in the power grid, the time error between the input and output of the magnetic holding relay is within 100 us, and accuracy of reactive power compensation can reach 1 kvar. 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.
|