Study On Power System Restoration Strategy Considering Uncertainty Of Wind Farm Output

With the continuous improvement of new energy permeability and the continuous development of its control technology,it is possible for new energy sources to supply power for surrounding loads as black-start power sources.This paper proposes a control strategy for the isolated operation of wind farms in a black start scenario.The strategy first uses diesel generators as auxiliary power to start the wind farm,and then uses the isolated grid system formed by diesel generators and wind farms to supply power for the surrounding load.In order to eliminate the influence of wind power fluctuation,on the basis of future wind power prediction,this paper adopts power-limited control to make the wind farm run steadily under the minimum stable output within the power supply time range of the black-start power source,and introduces droop control based on power-limited control is adopted to improve the frequency modulation capability of the system.At the same time,by calculating the reactive power output limit of the DFIG,the dynamic reactive power regulation ability of the DFIG is given priority,so that it can respond to the system reactive power change quickly during the black-start process.The simulation results show that the proposed control strategy can stabilize the load around the wind farm in the black-start scenario until the main network restores power supply to the load in the area,at the same time the outage time and loss of the load in the area are reduced,and the small isolated network system composed of the wind farm and the surrounding load has fast reactive power response ability,which improves the stability and security of the system.Besides being the first batch of black-start power sources,in the process of the network reconfiguration,the power support of wind farms can speed up the restoration of the system,but the output of wind farms is uncertain,which therefore poses a new challenge for the formulation of system restoration plans.This paper presents a method of power network reconfiguration restoration considering the uncertainty of the wind farm output.Firstly,the prediction error uncertainty model is used to describe the uncertainty of the wind farm output,and then the wind farm limited output strategy is used to eliminate the negative impact of wind power volatility on grid reconfiguration,and meanwhile the indicator which reflects the success rate of network restoration is defined to depict that the uncertainty of the wind farm forecast output may lead to the risk of restoration failure.After that,the stochastic dependent-chance programming model is established under the condition that the success rate of node restoration is not lower than a certain confidence level.And then the model for the optimal objective of maximizing the success rate of network restoration and minimizing the restoration time of grid is solved using the hybrid intelligent algorithm composed of discrete particle swarm optimization algorithm and stochastic simulation techniques.Finally,the comparison and analysis of the proposed method and the traditional restoration method has been made based on the example of IEEE 39-bus system.The result shows that the restoration strategy proposed in this paper can speed up the process of network reconstruction and reduce the restoration time of the grid while effectively coping with the uncertain of the wind farm output.