Research On Uncertainty Caused By Wind Power Integration Into Power System

The large-scale development of wind energy will contribute to solve the current problems about energy depletion and environmental pollution. Due to the random variation of wind resources, wind power is uncertain and performs uncontroliability in a power system. Thus, the issues caused by grid-connected wind farms become the biggest constraints. Uncertainty caused by wind power integration into power system, poses a challenge to security and adequacy of the power system. With the increase of the relevance of between climate, environmental factors and security and adequacy of power system, how to extend the function and application of space-time blackout defense framework to deal with the uncertainty of wind power has become an important and urgent problem.In addition to the external uncertainties such as load and failure, internal uncertainties also exist in a wind power system. Internal uncertainties are composed of the ones caused by wind itself such as fluctuation, intermittence, and randomness and by wind power generation process. The factors and features of fluctuation and intermittence, and descriptions of uncertaintyies of the short time wind power, are analyzed comparatively. The impacts of wind power uncertainty on frequency, voltage, angle and adequacy etc., and their mechanism, are also analysed.Response measures, strategy optimization and coordination are discussed from the generation side, grid and demand side, respectively. The importance of quantitative and risk analysis methods in the large-scale wind power integration into power system, is stressed. The ultra-short-term forecast, the wind farm active/reactive power control and complementary with other power are strengthened in the generation side. In the grid side, optimization of the grid structure, rational electric power dispatch management, and enhancement of anti-disturbance ability of the grid, strengthen the link role of generation side and demand-side to jointly cope with the uncertainty of wind power. Demand side management, distributed generation, electric vehicles and other measures are used for peak load shifting. The issues of the wind power uncertainties can not be solved in a level or a measure alone. Early warning and comprehensive defense against operational risks due to uncertainty of wind power need to be jointly coped with from generation side, grid side and demand side.In terms of security, the interaction of grid operation and wind farms need to be considered for security. On the one hand, the impacts caused by wind power integration are considered in the three lines of defense. On the other hand, the impacts of power network failures on the stability of the wind farm are analysed. Transient voltage stability and transient angle stability of wind power system are analysed, and their risks are assessed. First, the similarities and differences of induction generator and induction motor in transient voltage stability are compared. Transient voltage stability criterions and stability margin definition of induction generators are proposed, corresponding to transient voltage stability criterions of induction motors. The impacts on transient voltage stability of both node voltage and rotor speed are comprehensively considered. A multi-criteria assessment process is designed to speed up the evaluation for cases far away from the critical condition, and to ensure the accuracy for the cases close to the critical condition. Sensitivity analysis is performed based on the fault critical clearing time obtained through trial-and-error based on full scale time domain simulations. Second, transient voltage stability domains are calculated based on quantitative analysis techniques of transient voltage stability. Then transient voltage instability risks are assessed.The research on adequacy includes quantitative assessment of the probability level of control scene, achievement of dynamic probabilistic forecasts of wind power, expansion of the different levels of risk control measures(such as cold, heat, spinning reserve), coordinated control of multiple time scales and development of different control methods to achieve the coordination of control before and after the wind power disturbance events. Only in this way, reserve costs caused by the uncertainty of wind power may be reduced to a reasonable level, and energy conservation can be truly achieved. Temporal and spatial information mining for wind power prediction data are analysed. There are significant limitations about optimizating the spinning reserve on a single reserve mode or in short term. The importance and superiority of coordination and optimization of multi-grade reserves (including abandoned wind power control) are emphasized. From a risk point of view, multi-grade reserves are coordinated and optimizated in multiple time scales for adaptive adequacy control. The impacts of reserve capacity and reserve prices on adequacy control in the open market environment are analysed.This work is jointly supported by National Science Foundation of China (No.91024028), State863Project (No.2011AA05A105),. State Grid Corporation of China (No. SG10&SG11), Hong Kong RGC Grant (5151/10E), and Australia ARC (DP120101345).