| To achieve the goal of carbon peaking and carbon neutrality,China has vigorously promoted the development of renewable energy and a high proportion of non-fossil energy sources have been connected to the grid on a large scale.This has reduced the environmental pressure but increased the uncertainty of the power system on both the source and load sides.Power system imposes higher requirements for flexibility.The traditional planning method simulates the operation environment of power system in a relatively simple way,which leads to overly optimistic planning results.And the planning results cannot meet the flexibility requirements of power system.It can also affect the safety,economy and reliability of power system during dispatch.Therefore,how to consider operational flexibility more detailed and comprehensively in transmission network planning model is an urgent issue in the current research of power system.This paper is based on the transmission network planning problem.And this paper investigates transmission network planning problem considering operational flexibility from model to cope with uncertainty of net load fluctuations between adjacent periods and time point.This paper also investigates the algorithm improvementFirst,in order to address the problem that traditional planning model ignores the ramping constraints of units and cannot deal with the uncertainty of net load,a transmission network planning model considering operational flexibility is established.This model quantifies the lack of flexibility of power system.In addition,this model further considers maintenance factors.A two-layer joint planning model of unit and transmission capacity that takes planning,maintenance and operation into account is established.The upper model makes joint decisions on transmission capacity,units to be built,and line maintenance plans.In this paper,the N-1 expected accident analysis of the line is carried out by the iterative posterior iteration algorithm of adding one by one.The lower model simulates the operation of the power system under the condition that the expansion plan as well as the maintenance plan are determined.And the lack of flexibility is quantified in the lower model.Then this data is transferred back to the upper model to assist in the decision to build units and transmission capacity.The upper and lower models interact with each other to obtain the optimal solution.Finally,the proposed model is verified in a modified IEEE-RTS system.Secondly,to address the problem of strong volatility of high percentage renewable power systems between adjacent periods,this paper models the uncertainty of net load fluctuations and obtains four extreme fluctuation scenarios of net load.If these four extreme fluctuation scenarios can be addressed,the system will be robust enough to address any fluctuation process between adjacent periods.And in this way the system can describe the requirement for transmission capacity and operational flexibility.In this basis,a transmission network planning model considering extreme fluctuation scenarios of net load is established.The effectiveness of the proposed model is finally verified on the IEEE-RTS system.Finally,a transmission network planning model considering operational flexibility is established.And a time decoupling algorithm based on the Benders decomposition method is proposed:the model is decomposed into the main planning problem in the upper layer and the operational subproblem in the lower layer,and solved iteratively.Further,the lower operating subproblems with multiple time scales are decoupled in time to further reduce memory occupied by the model.The problem that the large-scale transmission network planning problem is difficult to solve is addressed.Finally,the effectiveness and superiority of the proposed method is verified based on the IEEE-RTS algorithm. |
