Abstract
Currently, some small islands with high wind potential are trying to reduce the environmental and economic impact of fossil fuels by using renewable resources. Nevertheless, the characteristics of these renewable resources negatively affect the quality of the electrical energy, causing frequency disturbances, especially in isolated systems. In this study, the combined contribution to frequency regulation of variable speed wind turbines (VSWT) and a pump storage hydropower plant (PSHP) is analyzed. Different control strategies, using the kinetic energy stored in the VSWT, are studied: inertial, proportional, and their combination. In general, the gains of the VSWT controller for interconnected systems proposed in the literature are not adequate for isolated systems. Therefore, a methodology to adjust the controllers, based on exhaustive searches, is proposed for each of the control strategies. The control strategies and methodology have been applied to a hybrid wind–hydro power plant on El Hierro Island in the Canary archipelago. At present, in this isolated power system, frequency regulation is only provided by the PSHP and diesel generators. The improvements in the quality of frequency regulation, including the VSWT contribution, have been proven based on simulating different events related to wind speed, or variations in the power demand.
Highlights
The increased use of intermittent renewable energy sources in most electric power systems has been documented [1,2]
The aim of this study is to evaluate the variable speed wind turbines (VSWT) contribution to frequency regulation in an isolated power system when it operates solely based on the use of wind and hydro resources
A pump storage hydropower plant (PSHP) and a VSWT connected to an isolated system have been modeled in MATLAB
Summary
The increased use of intermittent renewable energy sources in most electric power systems has been documented [1,2] These increases constitute a good way to reduce polluting gases generated by fossil fuel combustion. This class of renewable energies involves inherent drawbacks, such as unpredictability [3] or demand independence [4]. According to Albadi and El-Saadany [3], the impact of renewable energies on power systems depends mainly on its penetration rate and the system inertia For this reason, the negative effects of renewable energy sources are amplified in isolated systems. Kaneshiro [11] has analyzed how wind ramps affect the quality of supply in a Hawaiian power system, considering different rates of renewable penetration and highlighting the importance of wind forecasting in the medium and long term in order to operate the system safely and efficiently
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