Optimal Wind DG Integration for Security Risk-Based Line Overload Enhancement: A Two Stage Approach

Line congestion margin is the available line capacity before the line becomes fully loaded. It is a quantity to measure the transmission lines security level. Placing of large scale distributed generation (DGs) units can be a key technique to alleviate line congestion, hence enhance the transmission line congestion margin, and grid security levels. However, the influence of DG integration on line congestion margin is effective at locations where transmission lines operate near to their maximum capacity. In addition, determining the required penetration level of DG (DG size) is crucial for maximizing the DG system support benefits in transmission system. A two stage approach is presented in this paper for optimal integration of large-scale wind DG for improving line congestion risk based on the congestion margin level. In stage one, a probabilistic approach is developed to predict lines with the highest probability to be congested considering the uncertainty of the line congestion margin. Once lines with a highest risk to be congested are determined at the end of the first stage, the result from stage one is employed to place DG at the node bus to which the predicted most congested line is delivering power. A Mixed Integer Linear Programing (MILP) optimization model is developed in the second stage to determine the optimal DG penetration level (DG size) for improving transmission line congestion margin considering transmission line investment deferral.