Collaborative Optimization Strategy For Power System Restoration With Renewable Energy Integration

In recent years,the trend of shortage of fossil energy and continuous growth of electricity demand,and the phenomenon of global warming is also becoming increasingly significant.On one hand,the rapid development of renewable energy power generation technology provides solutions to this phenomenon.On the other hand,it also brings great challenges to the secure and stable operation of power systems,and even leads to frequent worldwide blackouts.After a blackout,the formulation of a reasonable and orderly emergency response plan for power system restoration can significantly reduce the large economic losses,casualties and social impacts caused by the blackout.Due to the complexity of the power system,it is difficult to carry out the power system restoration strategy.In addition,renewable energy generators can be utilized for black-start power sources and assist to accelerate the resoration speed of the power system,but the uncertainty of their generation outputs will enhance the risk of system operation in the process of system restoration.Based on the above problems,this paper studies the collaborative restoration optimization of power system considering renewable energy integration:(1)The restoration characteristic of the generators in the black-start stage is introduced.The start-up power curve and the output characteristic curve of the generators are analyzed,and the linearization method based on the Big-M method is proposed.Considering the influence of the critical restoration paths on the generator start-up sequence in the process of system restoration,a generator start-up sequence optimization strategy considering the critical restoration paths is proposed.The objective function is to maximize total active power capacity of the system.Considering the constraints of the generator start-up power and transmission line status,a mixed integer linear programming model is established.The commercial solver is used to obtain the optimal generators start-up sequence,and the collaborative restoration optimization of the generators start-up sequence and the transmission lines is realized.(2)The generation output curves of wind turbine and photovoltaic are obtained by employing the non-parametric kernel density estimation method.Due to the complementary of wind turbine and photovoltaic generation output in the wind-solar hybrid system,the Frank-Copula function is used to obtain the joint output characteristic curve of the wind-solar hybrid system.Considering the influence of integration timing of the wind-solar hybrid system on the generators start-up sequence,an optimization model of generators start-up sequence considering the wind-solar hybrid system is proposed.Due to the uncertainty of generation of the wind-solar hybrid system,the generators start-up sequence optimization strategy based on confidence gap decision theory is constructed,and the probability constraints in the model are handled by the scenario-based method.The robust optimal solution of generators start-up sequence is obtained by commercial solvers,which verifies the positive effect of renewable energy generators on accelerating system restoration speed.(3)Aiming at the single-step load restoration optimization problem,a bi-level load restoration optimization strategy for the wind-storage combined system is proposed.The upper model takes maximizing the current restorable load as the objective function,and establishes a mixed integer linear programming model to attain the current optimal load point and transmission line restoration scheme,and delivers the solution to the lower model.The lower level model adopts a nonlinear one,and aims to minimize the length of the current time step,which is delivered to the upper lever model.By iteratively solving the upper and lower models,the optimal load restoration scheme of the current time-step shortest load restoration duration is obtained.By solving the bi-level optimization model,the dispatch output of wind-storage combined system can be obtained at the current time step.In order to reduce the error between the dispatch output and the actual output of the wind-storage combined system,a real-time schedule model of the energy storage system is proposed.By constantly updating the power system operation status and iteratively solving the proposed single-step load restortion model,the complete load restoration strategy can be obtained.The optimization strategy of power system collaborative restoration considering renewable energy integration proposed in this paper provides a theoretical basis for exploring the optimization of power system collaborative restoration and the modeling of cold load characteristics in the restoration process.On the other hand,it provides research ideas for solving the problem that how renewable energy generators participate in the power system restoration process.