The lack of synchronous inertia, associated with the relevant penetration of variable speed wind turbines (VSWTs) into isolated power systems, has increased their vulnerability to strong frequency deviations. In fact, the activation of load shedding schemes is a common practice when an incident occurs, i.e., the outage of a conventional unit. Under this framework, wind power plants should actively contribute to frequency stability and grid reliability. However, the contribution of VSWTs to frequency regulation involves several drawbacks related to their efficiency and equipment wear due to electrical power requirements, rotational speed changes, and subsequently, shaft torque oscillations. As a result, wind energy producers are not usually willing to offer such frequency regulation. In this paper, a new control technique is proposed to optimize the frequency response of wind power plants after a power imbalanced situation. The proposed frequency controller depends on different power system parameters through a linear regression to determine the contribution of wind power plants for each imbalance condition. As a consequence, VSWTs frequency contribution is estimated to minimize their mechanical and electrical efforts, thus reducing their equipment wear. A group of sixty supply-side and imbalance scenarios are simulated and analyzed. Results of the case study are compared to previous proposals. The proposed adaptive control reduces the maximum torque and rotational speed variations while at the same time maintaining similar values of the load shedding program. Extensive results and discussion are included in the paper.

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The increase in the penetration of renewable energy is a reality in the vast majority of countries, both in Europe and in the rest of the world. This increase is not only occurring in continental power systems, but also on small islands that have high wind and/or solar potential. However, a high renewable energy penetration may compromise the stability of power systems, especially in the case of islands, which constitute isolated power systems. This is due to the inherent characteristics of renewable resources (uncertainty, intermittency and independence between availability and demand). These drawbacks are amplified by the power system inertia reduction caused by the fact that renewable generators are normally decoupled from the grid through a power electronics interface that do not add inertia to the system. It is well known that the long-term variability of renewable energy is well managed by pumped storage hydropower plants (PSHP). Thus, PSHP play an important role in the renewable resources integration,