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Inadequate frequency response can arise due to a high penetration of wind turbine generators (WTGs) and requires a frequency support function to be integrated in the WTG. The appropriate design for these controllers to ensure adequate response has not been investigated thoroughly. In this paper, a safety supervisory control (SSC) is proposed to synthesize the supportive modes in WTGs to guarantee performance. The concept, region of safety (ROS), is stated for safe switching synthesis. An optimization formula is proposed to calculate the largest ROS. By assuming a polynomial structure, the problem can be solved by a sum of squares program. A feasible result will generate a polynomial, the zero sublevel set of which represents the ROS and is employed as the safety supervisor. A decentralized communication architecture is proposed for small-scale systems. Moreover, a scheduling loop is suggested so that the supervisor updates its boundary with respect to the renewable penetration level to be robust with respect to variations in system inertia. The proposed controller is first verified on a single-machine three-phase nonlinear microgrid, and then implemented on the IEEE 39-bus system. Both results indicate that the proposed framework and control configuration can guarantee adequate response without excessive conservativeness.

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The power system must be operated to withstand any single equipment outage as well as other credible contingencies. At times, this is either not possible or requires overly conservative operation of the system. In response, utilities have developed numerous specialized actions in response to specific events that ensures continued reliable operation of the grid. Such a defined response is generally referred to as a Remedial Action Scheme RAS). RAS have proliferated in recent years as they may allow deferred transmission upgrades and new interconnections. This chapter overviews various approaches to RAS design and related defense systems.