Hybrid voltage stability assessment (VSA) for N−1 contingency

•This is the first report about VSA for N−1 contingency using a hybrid approach.•It is a combination of measurement data and model-based sensitivity.•The measurement data is used to build the Thevenin equivalent.•An enhanced model-based sensitivity is proposed to estimate N−1 status.•The hybrid approach provides a highly accurate VSA for N−1 contingency. With the growing deployment of phasor measurement units (PMUs), measurement-based voltage stability assessment (VSA) that estimates the system Thevenin equivalent has been widely discussed in recent years. This approach attracts favorable attentions mainly for its simplicity and great potential in real-time applications, as opposed to the continuation power flow (CPF) method which is model-based VSA. However, the existing measurement-based VSA deals with the normal case, but not any contingency case because there is no measurement data for a contingency case which is hypothetical. With this motivation, a hybrid VSA method is proposed based on both model-based and measurement-based techniques. First, an enhanced model-based sensitivity analysis estimating the post-contingency status is proposed, and then it is combined with the measurement-based Thevenin equivalent approach. The proposed sensitivity analysis has the feature of simplicity, which is aligned with the measurement-based Thevenin equivalent. Test results with the IEEE 14, 39, and 118-bus systems show that the proposed sensitivity is highly accurate in estimating N−1 contingency system variables and the proposed hybrid VSA method for N−1 contingency captures the insecure contingencies successfully. The proposed method greatly broadens the practical application of PMUs for VSA under N−1 contingency.