A NEW APPROACH FOR CORRECTIVE AND PREVENTIVE CONTROL TO UNSOLVABLE CASE IN POWER NETWORKS HAVING DERs

Abstract

In recent times, Korean power system operating conditions have gradually approached an upper limit. When a contingency occurs, the power system may have unsolvable cases for which a power flow solution does not exist. Different from the cases of bad initial guesses or the solutions are too close to the solvability boundary in which numerical methods such as optimal multiplier or continuation power flow method can be applied, in unsolvable cases, the only way to restore solvability would be structure modifications. In this thesis, a new approach for corrective and preventive control to such cases is proposed. The strategy is implemented in two steps: (i) finding any solution regardless its feasibility (Corrective control)

(ii) for the infeasible solution, make it feasible with additional modifications to voltage at load buses having Distributed Energy Resources (Preventive control). The test case built based on the peak load profile of 2008 in Korea by KEPCO including 1336 buses is analyzed. The most important contribution of the proposed method is ability to prevent voltage collapse. In addition, a new approximation technique which is able to capture high non-linear factors is introduced. Finally, since reactive power compensation is optimized to restore solvability, all demands are met- in other words, no blackouts happen. The proposed method has been being integrated in the load flow program designed by power 21 Corporation.