1. PMU Based RAS for a Hybrid AC/DC System

In current practice, RAS design is derived from off-line studies based on some performance criteria and response to events. Depending on the method of detection, existing RAS can be classified as event-based or response-based. Event-based RAS are designed to operate on the recognition of a particular combination of events (such as loss of several ties). Response-based RAS are based on real-time measurement and initiate control actions when the responses hit the trigger level. Event-based RAS can be fast since one need not wait for the response development. On the other hand, a response-based RAS has been mainly for slower phenomena, and can operate for unknown events and varying operating scenarios. The next generation of corrective controls requires fast detection of the system instability based on both events and responses from wide area monitoring. This has become possible with the deployment of real time phasor measurements (PMUs), as well as with modern communication systems. In addition, the PMUs may allow disturbances to be detected more quickly allowing less severe action.