Research On The Dispatch Flexibility Of The Power System With Wind Power Penetration

The wind power industry has been developing rapidly in recent years. Owing to the variety and the uncertainty of the wind power, the operation of the power system is influenced by the wind power. With the penetration of the wind power, the conventional units of the power system turn to changing their running state more frequently. The interior point and the bound-branch mixed integer method is introduced into the paper to work out the unit commitment models. Then the flexibility of the power system is introduced and a flexibility index of the power system is proposed. Then the simulation of the example is manipulated to verified. The work that has been done in this paper is listed as follows.(1) Firstly, the conventional unit commitment model is analyzed in this paper. The objective of the unit commitment model is to minimize the operation costs of the power system. And the start-up cost of the unit is also added in the objective. The constraints are consisted by the system constraints and the generator constraints. The system constraints include the balance between system output and loads, and the spinning constraints. The generator constraints include the maximum and minimum output constraints, the ramping constraints and the time constraints. With the wind power penetration, the unit commitment model is modified with the balance between system output and loads, and the spinning constraints.(2)Unit commitment model is a high dimension, mixed and nonlinear optimization problem. with 0-1 variables. With the wind penetration, the wind power is based on a dividing-stage strategy. The expectation of the wind power production every stage is used for power output. The inner point method and branch-bound method is used to solve this problem. Firstly, the 0-1 variables are relaxed as the continuous variables. The continuous model is worked out by the interior point method. Then the bound and branch method is applied to find the integer solution. The IEEE-57 test system is simulated and observed to verify the algorithm.(3) The flexibility of the power system is introduced in this paper. The flexibility index is proposed. This index can honestly reflect on the uncertainty and the variability of the wind power. The wind power output is modified by taking the wind power forecast error. The power forecast error is calculated by Monte Carlo method. Then use the new winder power output and modify the conventional units output. Then the output is used to calculate the flexibility index. This flexibility of the power system focuses on the spinning reserve. The index is calculated by the ramping constraints and the differences between units output and the maxi- or mini-mum output of the units. The IEEE-57 test system is simulated and observed to verify the algorithm.