Research On Wind Power Penetration Limit Calculation Based On Conditional Value At Risk Theory

With more emphasis put on the new energy increasingly, Wind power technology has been developed rapidly. Installed capacity of the wind power station is also more and more strong. Large-scale grid integration of wind energy conversion systems will change the tideway distribution and voltage level of the local power grid. What's more, since the randomness of the wind power output also will affect the stability of the system. The size of the wind power penetration limit is one of the key factors which affecting system stability and safety. As a result, define the limit of the wind power penetration is the necessary problem that must to be solved in the engineering calculation.In order to determine the penetration limit of wind power, the optimization model is built with a new mathematical method of Conditional Value-at-Risk (CVaR). In this model, the randomness characteristic of the output of the wind power is considered. The maximum allowable capacities of wind farm can be calculated under different probability levels. Moreover, the extreme impact can be deal with effectively under tail risk over the probability. It is difficult to analysis the function of CVaR, the function is transformed into integral form of probability density function. Penalty function is added to smooth the piecewise function. In order to simplify the model to linear optimization, Aided variable is introduced and continuous integral calculation is instead of discrete points.Make the IEEE30 bus system as the simulation example in the model. Wind power penetration limits in different confidence level are calculated and analyzed when wind farm power system was access to a single wind farm and multiple wind farms. The results of different schemes show that, the wind power penetration limit is related with wind speed and the network nodes of wind farm directly. The results has indicated that the CVaR model and it's solution methods of wind power penetration limit is simple, effective and feasible.Actual examples have compared to the CVaR model and the traditional algorithm works of the steady-state power flow, and to carry on transient state verification combined with the time domain simulation method. The analytical results has demonstrated that the optimized calculation method of CVaR model is more reasonable due to its consideration on the randomness of the wind speed, in addition, transient state verification can test whether or not the steady-state calculation consequence is correct.