# Design and Development of a Management System for Energy Microgrids Using Linear Programming
## 2 Materials and Methods  
### Microgrid Control System  
One important component of microgrids is the energy source. There are different sources for the generation of energy that can be classified according to their predominance, called conventional and non-conventional sources, or according to the type of resources used, that is, renewable and non-renewable sources [9]. Conventional sources refers to the most widely used energy sources worldwide, among which the energy supplied by means of hydroelectric plants or the burning of fossil fuels, such as diesel, coal, and gas, stand out. Less predominate sources in the market are called unconventional sources, where the primary source is produced by natural resources or it is an emerging energy source under development. In the same way, renewable energy sources are those whose potential is abundant and include solar energy, hydraulic energy, wind energy, biomass energy, and geothermal energy [10]. Conversely, there are other sources of energy that are not renewable, that is, they are found in a limited quantity in the world and the rate of their consumption is higher than their regeneration time; some of these non-renewable energy sources are fossil fuels such as coal, oil, and natural gas, as well as uranium. A traditional microgrid system generally consists of a set of wind turbines, photo-voltaic panels, small hydro power, diesel micro-turbine engine, and battery storage.  
The unpredictable nature of renewable energy sources such as solar and wind affects the performance and reliability of the microgrid, due to excess electricity generation or lack of generation, which is considered to be the main drawback for its adoption [11]. However, some approaches such as those presented by [12] argue that this problem can be solved by combining two or more power sources together with a backup unit to form a hybrid renewable energy system. In other words, the system is operated with a set of energy sources and storage devices to satisfy the demand, even when some of them are not available.  
The microgrid control system is described in [13] as a four-levels system: the fourth level has a system that assigns the production of active and reactive power to each generator element of the grid according to the demand. The third level sets the voltage and frequency references in the nodes, while the second level of the control system corrects the voltage and frequency deviations in the network. Finally, the primary control level executes actions locally on the generation sources, keeping the voltage and power at the reference values.  
Within the fourth level of the control system mentioned above, setting the active and, sometimes, reactive power from each generator unit at each time period is a core element of the strategy adopted to manage the power generated by the microgrid. This strategy would depend of the system goals, minimizing costs and/or maximizing coverage. In this study, the management strategy is a Unit Commitment (UC) that defines an optimization problem that seeks the optimal scheduling of generation units in a specific time horizon (hourly, daily, or weekly). The objective of the UC strategy described in [14] is to satisfy the demand at minimum cost, considering the on/off states of each generation unit, its ramps, reliability restrictions, system capacity, transmission, environmental impact, etc.