Decision Tree GPS Global Positioning System OP Operating Point PMU Phasor Measurement Unit PSS®E Power System Simulator for Engineering RBF Radial Basis Function RF Random Forest SCADA Supervisory Control and Data Acquisition SVM Support Vector Machine

An active machine learning technique for monitoring the voltage stability in transmission systems is presented. It has been shown that machine learning algorithms may be used to supplement the traditional simulation approach, but they suffer from the difficulties of online machine learning model update and offline training data preparation. We propose an active learning solution to enhance existing machine learning applications by actively interacting with the online prediction and offline training process. The technique identifies operating points where machine learning predictions based on power system measurements contradict with actual system conditions. By creating the training set around the identified operating points, it is possible to improve the capability of machine learning tools to predict future power system states. The technique also accelerates the offline training process by reducing the amount of simulations on a detailed power system model around operating points where correct predictions are made. Experiments show a significant advantage in relation to the training time, prediction time and number of measurements that need to be queried to achieve high prediction accuracy.