A Method For Available Quantity Transfer Capability Calculation

Wind power industry is growing fast these years, while the energy center is far apart from the load center in China. In order to bring nationwide electric supply and demand into balance, wind power need to be transferred across the areas in a planned way. The quantity of the wind power trading is determined by not only the generation side and the load side, but also the transmission side.In this paper, we define a new concept-Available Quantity Transfer Capability (AQTC) to represent the quantity of the Available Transfer Capability (ATC) in the period, and we also present a rapid AQTC calculation method. The steps of the method are:firstly, the trading period should be divided into several small parts according to the typical operation mode; then the probabilistic ATC in each small period should be calculated; then the AQTC in each small period will be obtained by the product of each probabilistic ATC and its corresponding duration; finally, the AQTC in the whole period can be calculated by the sum of the expectation of each probabilistic ATC.The existing probabilistic ATC methods can hardly achieve the required accuracy and speed simultaneously. Therefore, we also present a new method based on the probabilistic power flow, and define a new concept-Element Available Transfer Capability (EATC). The steps of the method are:firstly, the max system state should be obtained by the deterministic ATC calculation; then the distributions of the state-variables can be calculated by the probabilistic load flow calculation; then the distributions of EATCs will be obtained using the proposed models; finally, the distribution of ATC will be calculated based on the distributions of EATCs, the impact factors of EATCs and the correlations of EATCs.The result of the simulation shows:the model of EATC is effective, and with the impact factors of EATCs and the correlations of EATCs, the influences of more elements can be taken into account in the final result of probabilistic ATC; compared to the existing methods, the proposed ATC method can achieve the requirement of both accuracy and speed; the model of AQTC calculation is effective, and the result can be used for decisions in wind power trading. At last, the feasibility about the application in larger systems is studied.