A method of rapid detection of the grid voltage

That large-scale wind farm connects to the power grid has affected the safe and stable operation of the grid. Low Voltage ride through (LVRT) capability is required by new power system operating codes. At the same time, the sudden change of the grid voltage is a shock for wind turbine. Fast and accurate detection of grid voltage sudden change fault is an important condition to achieve safe operation of the power grid and LVRT of wind power system. This paper fully analyzes the existing voltage sudden change detection method and presents a method of comparing the instantaneous value of test signals with the instantaneous value of “standard sinusoidal digital signal”. It generates the standard signal with the same frequency and phase as the test signal by Phase Locked Loop (PLL) technology. It gets values of test signal at some point in a cycle by the digital signal processing technology. Then, the difference between each present value of test signal and its corresponding “standard sinusoidal digital signal” values is used to reflect the real-time status of the signal under test. This instantaneous value comparison method can accurately and without delay detect the sudden change of voltage (sudden drop or a sudden jump in) and the computing is small. In order to ensure the accuracy of the detection without changes in grid frequency, but also from the impact of voltage sag depth, we improve the PLL signal input circuit. The fast and accurate detection of the grid voltage sudden change supplies the timely and accurate condition for wind turbine to through the low voltage.