Stability Analysis And Control Strategy Optimization Of AGC In Yunnan Power Grid

Yunnan power grid has been operating in an asynchronous mode.In this situation,Yunnan power grid becomes a high-proportion hydropower system,and the whole inertia of the grid becomes smaller,the local load damping decreases.Within the deadband of the hydropower governor,the frequency change is very sensitive to the load disturbance.The single-step 100 MW power regulation may cause 0.1Hz frequency oscillation,and it also faces the challenge of fast frequency fecovery after 10 million-kilowatt peak-shaving and large disturbance.It is of great practical significance to study and formulate the coordinated control strategy of AGC for a large-scale HVDC sending system with high-proportion hydropower,and to realize the fast frequency fecovery after 10 million-kilowatt peak-shaving and large disturbance on the basis of maintaining frequency stability.The paper firstly compares the frequency characteristics of Yunnan power grid before and after asynchronous operation,and systematically analyzes the changes of frequency characteristics relationship among frequency limit controller(FLC),Primary Frequency Control(PFC)and Automatic Generation Control(AGC).From the actual operation case,the problems of the AGC control on the main station,the power plant and the unit are analyzed in depth.Secondly,for the frequency oscillation(period of 40-60s)caused by AGC control,a piecewise linear analysis model of frequency stability including AGC control is established to analyze the effect of operation mode change and AGC control parameters on small disturbance stability.Further research reveals the interaction between primary frequency modulation and AGC in the process of frequency oscillation.A method for setting the frequency response coefficient of AGC in high-proportion hydropower system is proposed.Finally,combined with the actual operation of Yunnan Power Grid,the AGC control coordination strategy of large-scale HVDC sending system with high-proportion hydropower is proposed.On the main station side,the advantages and disadvantages of four control strategies are discussed,and improved FFC+FFC strategy is proposed.On the power plant side,SCHER frequency reverse small step return mode is reformed to prevent the large step return to the base point having a new impact on the system frequency.On the unit side,the coordination control problem of primary frequency regulation and AGC is improved to reduce the Effect of AGC on primary frequency regulation.The actual operation shows that the AGC coordinated control strategy proposed in this paper can effectively suppress the frequency oscillation while taking into account the fast regulation performance of AGC under large disturbances.The qualified rate of 0.1Hz frequency in Yunnan Power Grid is significantly improved,and the frequency quality reaches a high level.