Abstract
Frequency control is one of the most critical tasks in isolated power systems, especially in high renewable penetration scenarios. This paper presents a new hydropower pumped-storage dual control strategy that combines variable-speed-driven pumps and fixed-speed-driven pumps. A possible case for implementation of such a control scheme is described based on El Hierro Island’s power system. This isolated power system consists of a hybrid wind pumped-storage hydropower plant and diesel generators. The pumped-storage power plant is divided into a hydropower plant equipped with four Pelton turbines and a pump station equipped with both fixed- and variable-speed pumps. According to the proposed control scheme, frequency regulation will be provided by a dual controller: a continuous controller for the variable-speed pumps and a discrete controller for the fixed-speed pumps. The Pelton units, which operate as synchronous condensers, also supply the power system inertia. Therefore, diesel units may be disconnected, decreasing generation costs and greenhouse gas emissions. Owing to the combination of both controllers and the inertia of the Pelton units, an acceptable frequency regulation can be achieved. This technique has been validated through computer simulations.
Highlights
One of the known methods of increasing renewable energy integration in power systems is by means of pumped-storage hydropower plants (PSHPs) [1]
The PSHP is divided into a hydropower plant equipped with four Pelton turbines and a pump station
This paper has studied the frequency control in an isolated system consisting of diesel units and a hybrid wind pumped-storage hydropower plant
Summary
One of the known methods of increasing renewable energy integration in power systems is by means of pumped-storage hydropower plants (PSHPs) [1]. Results showed that the converter response was virtually instantaneous compared to rotor speed deviations or wicket gate movements so that the response to the power command signal was improved These results were confirmed in Reference [19], where the dynamic response of a PSHP providing primary regulation in pumping mode was simulated. Simulation results confirmed that variable-speed units operating in pumping mode reduced frequency deviations caused by wind speed fluctuations. Simulation results demonstrated that variable-speed units in pumping mode in this isolated power system could compensate fluctuations in the power generated by the wind farm. The pump station must consume the difference between the wind power supplied and the power consumed In this scenario, some diesel units are connected so they can provide primary reserve and inertia, both enough for maintaining frequency under safe values.
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