Lagrange Relaxation Based Optimization Of Generator Restoration Sequence For Blackout System

Generator restoration after large scale blackout is a nonlinear combinatorial optimization problem in the interconnected power grid.Reasonable generator restoration sequence play a very important role in speeding up the system restoration process and minimizing the outage lost.With the expansion of interconnected power grid,the safe operation of the system face test,and it is easy to occur large area blackout,it becomes an important problem for the researchers to improve the computing speed of restoration control strategy of the large scale units.At present,optimization of generator restoration sequence for blackout system is mostly based on the operation experience and expert system.Heuristic algorithm,intelligent algorithm and other methods subsequently are applied to generator restoration sequence optimization problem.The workload of establishment and maintenance of the knowledge base in expert system is very large,expert system is limited,it is difficult to get information of system in an all-round way.Although heuristic algorithm and intelligent algorithm can speed up the calculation in some degree,the computation time of large scale units is still long.Therefore,we need further study the algorithm which can improve the computing speed of generator restoration sequencing problem.This paper proposes a Lagrange Relaxation based optimization of generator restoration sequence for blackout system.The main work completed is as follows:1.For the current mathematical mode of generator restoration sequence for blackout system is complex and various,we analyzed generator restoration process in principle,on this basis we simplified objective function and constraint conditions,thus established the mathematical model of generator restoration sequence of blackout system.The unit state variables as the decision variables of objective function and constraint conditions,it isn't to specifically distinguish black start units with non black start units,unified the form,and it is convenient for the algorithm to solve the problem.2.Considering the shortcomings of the traditional algorithm computing speed,proposed a generators restoration sequence optimization method for the large scale blackout system which is based on Lagrangian Relaxation,analyzes the mathematical principle of Lagrangian Relaxation algorithm,and in the process of solving the dual problem,combining with the decomposable integer programming problem to explain why this method can improve the computing speed.3.In view of the slow convergence speed problem of Lagrangian Relaxation algorithm,on the one hand the paper gives the selection method of the initial value of the Lagrange multiplier,on the other hand the subgradient algorithm and the adaptive subgradient algorithm are adopted to amend lagrangian multiplier in the process of optimization,speeding up the convergence speed of the algorithm,further reduce the computation time.4.Based on the actual New England system,partition system of the guangdong power grid,and partition system of the jiangsu power grid,we verified the effectiveness of the algorithm through simulation and analysis.