Abstract
Nowadays, microgrids (MGs) play a crucial role in modern power systems due to possibility of integrating renewable energies into grid-connected or islanded power systems. The Load Frequency Control (LFC) is an issue of paramount importance to ensure MGs reliable and safe operation. Specifically, in AC MGs, primary frequency control of each energy source can be guaranteed in order to integrate other energy sources. This paper proposes a micro-hydro frequency control scheme, combining the control of a reduced dump load and the nozzle flow control of Pelton turbines operating in autonomous regime. Some works have reported the integration of dump load and flow control methods, but they did not reduce the dump load value and adjust the nozzle flow linearly to the power value demanded by users, causing the inefficient use of water. Simulation results were obtained in Matlab®/Simulink® using models obtained from previous research and proven by means of experimental studies. The simulation of the proposed scheme shows that the frequency control in this plant is done in correspondence with the Cuban NC62-04 norm of power energy quality. In addition, it is possible to increase energy efficiency by reducing the value of the resistive dump load by up to 7.5% in a case study. The validation result shows a 60% reduction of overshoot and settling time of frequency temporal behavior of the autonomous micro-hydro.
Highlights
Microgrids are being used mainly to increase resilience and reliability of electrical grids, to integrate the addition of distributed renewable energy sources like wind, solar photovoltaic (PV) or micro-hydropower generation, to provide electricity in isolated areas not served by centralized electrical networks, and to reduce greenhouse gases emissions
More than 130 million people around the world are served by MGs and a 67 percent of these are by autonomous micro-hydro power plants (AMHPP) [2]
When user load demand is greater than 11%, the frequency variations are greater than 1 Hz, so they would be outside the norm considered
Summary
Microgrids are being used mainly to increase resilience and reliability of electrical grids, to integrate the addition of distributed renewable energy sources like wind, solar photovoltaic (PV) or micro-hydropower generation, to provide electricity in isolated areas not served by centralized electrical networks, and to reduce greenhouse gases emissions. According to [1], a MG is a group of interconnected loads and distributed energy resources within clearly defined electrical boundaries that acts as a single controllable entity with respect to the grid. The future development of electricity and its universal availability is an extremely important issue and depends on the possibility of providing access to it for all those who demand it in constantly growing economies, assuming that this energy comes from sources that are reliable, safe and environmentally friendly [3].
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