Study On Thermal Units Frequency Regulation Ability In Multi-area Power Systems With High Penetration Wind Power

The lack of electricity and fossil energy consumption has already become the important reason restrict the economic development of our country. Wind power has the characteristics of rich reserves, low cost, renewable and pollution-free, which make it the most commercial potential and one of the most dynamic renewable energy. The main use of wind energy is wind power generation, in our country, under the background of vigorously promote the construction of the UHV project, wind power transmitt through the UHV transmission network would be the development trend of wind power in the future. However,wind power output has the characteristics of randomness and uncertainty due to the uncertainty of wind speed. Large-scale wind power integration will influence the operation of the power grid. In our country, the situation of abandoning the wind power is still very serious at present, large-scale wind power integration still has problem.Analyses the reason of restricting wind power integration can be taken from multiple perspectives, this article take it from the perspective of power grid frequency stability. The analysis of the uncertainty of wind power fluctuations gives a effective way to study the influence of wind power fluctuations on power system frequency regulation.Firstly, the historical data of wind farm are used and based on it wind power fluctuations indexes are defined: wave intensity and intensity change. Wavelet decomposition and least squares fitting are used to obtain the wind power fluctuation intensity model which has the three parameters of power law. In the power law model, it gives the relationship between the instantaneous fluctuation of wind power and the 15 minute average wind power. Based on that, we can achieve real-time estimation of instantaneous wind power fluctuation. This result provides the basis for the analysis of the influence of wind power fluctuation on power grid frequency stability.In order to further evaluate the influence of wind power fluctuations on grid frequency regulation. Using the theory of stochastic process, the frequency regulation ability(FRA) consider wind power fluctuations is defined and its quantitative calculation method is presented. Combined with the two-area power system, FRA under different operation condition is calculated, factors which have influence on FRA are analyzed. Then, we explores how FRA can be applicated in power system and provide a method for deploting frequency regulation resources in system based on the calculation of FRA. The effectiveness of the proposed method is verified by simulation.Finally, consider with the wind power fluctuation characteristics, this paper from the perspective of primary frequency regulation and secondary frequency regulation, proposes two strategies to improve the performance of power grid frequency regulation ability. For primary frequency regulation, primary frequency control is changed to use dynamic control strategy to improve its responsiveness to low frequency disturbance; For secondary frequency regulation, the measured values of wind farm output is introduced to the feedforward control of AGC and improve the ability of the secondary frequency regulation of the power grid. The effectiveness of the above two control strategies are verified in time domain simulation.This work was financially supported by the National Basic Research Program of China( 973 Program)(2012CB215201), Technical Project of State Grid Corporation of China(2013320001510213) and The National High Technology Research and Development Program(863 Program)(NO. 2011AA05A105).