| At present,China’s power system has entered a highly interconnected era.The high interconnection of power systems solves the imbalance of China’s energy pattern,but it also brings new challenges to the safe and stable operation of power systems.Extreme events often cause large-scale damage to the electrical components in the transmission system.The power system may have serious cascading failures,resulting in large-scale blackouts,which will cause heavy losses to the development of social economy.Therefore,there is an urgent need for a power system preventive control strategy to deal with extreme events to reduce the impact of extreme events on power supply.In this paper,an active islanding strategy of power system under extreme conditions is proposed to realize the preventive control of power system in response to extreme events.The main contents and results of this paper are as follows:Based on the graph theory model of power system,a mathematical model of active splitting surface searching problem is proposed.The mathematical model transforms the calculation of the active splitting surface into a node combination problem based on active power balance.The model also proposes general constraints such as connectivity constraints,output of balanced nodes constraints and island number constraints,as well as specific constraints adapted to various extreme conditions.These constraints ensure the rationality of the splitting surface solved by the model and the applicability to various extreme conditions.Genetic algorithm is used to optimize the mathematical model of active islanding surface of power system under extreme conditions.Aiming at the problem of power system damage caused by extreme typhoons,a staged active islanding strategy of power system under extreme typhoon conditions is proposed to prevent the occurrence and spread of cascading failures.Firstly,based on the Batts typhoon model and the vulnerability curve,the outage probability model of each transmission branch in the system is established.Based on the power flow calculation,the active islanding criterion under extreme typhoon conditions is proposed to evaluate the damage degree of the typhoon to the power system and determine whether to perform active islanding.Then,a specific constraint is set for the mathematical model of the splitting surfaces search problem—the required splitting branch constraint,and the vulnerable branch is set as the required splitting branch to adapt to the dispersed damage of the typhoon to the power system.Besides,an optimal load shedding model considering node voltage offset is proposed.The model minimizes the voltage offset of each node in the island by optimizing the reactive power output of the generators in each island and the load shedding of each node.Finally,the staged active islanding strategy of power system under extreme typhoon conditions is systematically expounded.The simulation results verify the feasibility and superiority of the proposed strategy.Aiming at the problem of power system damage caused by extreme earthquakes,an active islanding strategy for power system under extreme earthquake conditions is proposed to prevent the occurrence and propagation of cascading failures.Firstly,based on the elliptical seismic intensity attenuation model and vulnerability curve,the outage probability model of each transmission branch in the system is established.Based on the power flow calculation,the active islanding criterion under extreme earthquake conditions is proposed to evaluate the damage degree of the earthquake to the power system and determine whether to perform active islanding.Then,a specific constraint—isolated vulnerable branch constraint is set for the mathematical model of the splitting surfaces search problem,and the vulnerable branches caused by the earthquake are isolated within the same island to adapt to the characteristics of the earthquake’s damage to the power system.Finally,the active islanding strategy of power system under extreme earthquake conditions is systematically expounded.The simulation results verify the feasibility and superiority of the proposed strategy. |
