Security-Constrained Adequacy Evaluation of Bulk Power System Reliability

A framework of security-constrained adequacy evaluation (SCAE) based on analytical techniques is proposed to assess the ability of a bulk power system to supply electric load while satisfying security constraints. It encompasses three main steps: (a) critical contingency selection, (b) effects analysis, and (c) reliability index computation. Effects analysis is the most essential but computationally demanding procedure. It is important that effects analysis simulate contingencies in a realistic manner efficiently. However, effects analysis based on the traditional power flow technology often lacks the realistic system model and diverges when the system is severely stressed. In this paper, a non-divergent optimal quadratized power flow (NDOQPF) algorithm is proposed for effects analysis. It is implemented based on a single phase quadratized power flow (SPQPF) model that can improve solution efficiency, and a constrained optimization problem, which incorporates operational practices, security constraints, and remedial actions, is formulated to simulate contingencies realistically. The non-divergence of power flow is achieved by introducing fictitious bus injections that are driven to zero as the solution progresses. It guarantees convergence if a solution exists; if a solution does not exist, it provides a suboptimal solution that may include load shedding. The NDOQPF algorithm is capable of efficiently solving the RTO/ISO operational model as well. Such operational procedure is formulated as an optimization problem with the objective function being the bid cost function and congestion constraints. The proposed SCAE framework also includes an improved contingency selection/enumeration scheme based on SPQPF and reliability index computations. The methodology is demonstrated with the IEEE reliability test system