Towards a Demand/Response Control Approach for Micro-grid Systems

Recent studies have stated that storage devices, despite their actual high cost, could be used to tackle this issue by balancing the intermittent nature of RES production and the unpredictable building's occupancy. Storage devices could handle this issue, which is very complex without taking into consideration actual occupancy and environmental context. A demand/response control approach is introduced by focusing on micro-grid systems, which are composed of PVs, batteries, and buildings equipment (e.g., ventilation system, lighting, HVAC). A prototype was developed and deployed in a real-setting scenario at the EEBLAB. Experimentations have been performed, and results show the usefulness of the proposed control approach for micro-grid systems. The depletion of traditional resources, the increase of the electricity demand, together with the need of reducing CO2 emissions, have led to a large-scale deployment of renewable energy generators into electrical grids. Unfortunately, the random and discontinuous nature of these energies makes them difficult to control, and it is necessary to characterize as precisely as possible the production of these sources. The influence of their nature can be diminished by coupling two or more renewable energy sources (e.g., PV, Wind turbine) that could be connected with storage devices (e.g., Batteries, Fuel cell) or the electric grid network. The proposed control strategy aims to keep track of the amount of expected consumption (Demand) and the amount of produced energy (Response) in order to maximize the usage of renewable energy according to the actual context. The work presented in this paper is a part of an ongoing project aiming at developing a context-aware platform that could perform an instantaneous equilibrium of the Demand/Response balance. The aim is to integrate a control strategy for predicting, estimating, and controlling the interaction between power production, storage, and building demands. The system architecture includes a 70 Watts PV panel, a battery 25 Ah, and a ventilation system composed of two ventilators operating with a state feedback control with 24 Watts of maximum power. The connection with the grid is assured by a transformer which gives 12V in the output. This micro-grid is equipped with a platform for measuring the consumption and production (Demand/Response). A set of current and voltage sensors have been installed for measurement of the power in all branches of the installation. The purpose of this installation is to show the switching moments of the control approach between the battery and the electrical grid. The photovoltaic system is simulated with real irradiation and temperature data during 12 hours from 7:00am until 7:00pm. The temperature and irradiation profile are shown in Figures 4 (a, b), while the PV production during 12 hours is shown in Figure 4 (c). The battery characteristics are described in Table I, which includes the output voltage, rated capacity, float charge voltage, cyclic charge voltage, recommended maximum depth of discharge, and cycle life. For real experiments, only the voltage and the current can be measured, and all the others need to be estimated and the data provided in the catalogs of the batteries.