Optimum generation direction for transmission system maximum loading margin considering static voltage stability

Owing to the difficulties in building new generators and transmission facilities to accommodate the regionally increasing load demands, it becomes vulnerable to voltage instability from over-utilization of the existing facilities or any contingency. In addition to installing FACTS devices, a good generation direction (GD) can also alleviate voltage instability and thus increase loading margin (LM) for more power transferred to the loads. This paper proposes an optimum GD seeking method based on the particle swarm optimization (PSO) algorithm, involving in the continuation power flow (CPF) process to compute the maximum LM (MLM) for the particles, each of which represents a candidate GD for the participating generators. Three objective functions are suggested for possible purposes. The first one is simply used to solve for the MLM without considering operating cost, therefore the MLM derived is the largest. The second one is to minimize the operating cost and accordingly a corresponding MLM is derived. While, the last one is simultaneously to minimize the operating cost as well as maximize the MLM; thus a compromised result is obtained. Also, the results obtained with cost participating factor (Cost PF) approach are used to compare with the propose method and the effectiveness of the proposed method can be validated from the test results.