| Cascading failures caused by line overload is one of the major threats to the safe and stable operation of power systems.For a long time,the control of line overload has been mainly based on the means of shedding the generation and the load.However,shedding the machine and the load will bring serious economic losses,and the reconnection of the generation and the load will have a greater impact on the power system,affecting the stability of the system.With the large-scale application of new energy,researchers have proposed to coordinate controllable generation power adjustment to restore the overload line power,but the existing method ignores the influence of power dynamic changes on the temperature rise rate during the power generation adjustment process,which may be caused by temperature.The margin is too large to avoid large-scale generation and load shed.At the same time,due to the influence of generation regulation,it is difficult to reliably set the action time of transmission line overload protection,which may increase the risk of cascading failures in the power system.Therefore,considering the influence of dynamic power changes on the temperature rise process of overload lines,and describing the dynamic relationship between line temperature and power during overloading,it is the key to correctly and reasonably control and protect transmission lines from overloading.First of all,through the analysis of the power control response of synchronous generators(SG)and renewable energy generators(REG),the power control capability model of SG and REG is established;the sensitivity relationship between SG and REG power adjustment and overload line power is considered,the dynamic change model of the overload line power under SG and REG power adjustment is established;combined with the dynamic power change of the overload line and the thermal balance equation,the temperature change expression of the overload line under the dynamic power change is derived;based on this Combining the safety conditions of overload lines,the safety criterion of overloaded lines under power regulation is analyzed,the dynamic security domain of overload lines is described,and the prevention and control method of line overload is proposed,thereby realizing the accurate prevention of line overload control.Then,the generation bus and load bus shedding capacity models are established,and the dynamic power expression of the line under the coordination of generation and load shed and power adjutment is established.Based on this,combined with the derivation and analysis of the heat balance equation,a feasibility-based The line overload control method in the control domain puts forward an optimal control idea aiming at the minimum cutoff power;at the same time,considering the generation constraint,the load constraint and the balance bus adjustment speed constraint,the optimal control idea is proposed.The method of calculating the load and generation shedding amount of the excellent is to ensure the safe operation of the overload line and the grid,so that the load shedding power of the generation is minimized,and the economy and stability of the power system are improved.Finally,an adaptive overload protection idea that considers dynamic changes in power is proposed.Through power sampling at a certain time interval,the estimated dynamic allowable overload time is calculated,thereby setting the overload protection action time;at the same time,it proposes a calculation based on power sampling.The realization method of estimating the dynamic allowable overload time;the protection method proposed in this paper can adaptively set the protection action time under the premise of ensuring the line safety,delaying the protection action time to the greatest extent,and ensuring the correctness and reasonableness of the line overload protection Actions can leave enough time for the overload control method proposed in this article to ensure the applicability and reliability of the overload control method proposed in this article. |
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