Influence of LCU and Governor Combined Control of Hydropower Unit on Power System Frequency Stability

With the continuous optimization and adjustment of power grid structure in China, the frequency characteristics of power system also change. The frequency problem of hydropower high proportion power system is becoming increasingly prominent. After the system disturbance, the grid frequency faces the double test of slow recovery speed and low oscillation damping. In order to more accurately analyze the regulation characteristics of system frequency, it is necessary to comprehensively study the dynamic characteristics of the unit active power/frequency control system. The active power/frequency regulation of hydropower units is realized by the local control unit (LCU) active power control of the computer supervision and control system (CSCS) and the governor. The primary frequency regulation characteristics of the governor have been accurately mastered in the current electromechanical transient simulation of the system, but the influence of LCU of the unit CSCS on the frequency characteristics is less considered. In this paper, based on the full investigation of the operation status of active power joint control of main hydropower units in southwest power grid, the simulation model of LCU power closed-loop control was established, and the key parameters were measured. The influence of LCU active power joint control of CSCS on frequency oscillation damping was analyzed from the mechanism. In the simulation example, the influence of LCU active power control on frequency dynamic damping level and frequency recovery level was analyzed.