# A Real Model of a Micro-Grid to Improve Network Stability
## 3 Description of the DC Micro-Grid
### Hydrogen Circuit
The CompactRIO regulates the flow of energy from different sources and controls the actual electricity consumption; the CC system can thus determine the power from the different simulated power plants. Figure 6: A block diagram of the hydrogen circuit. Figure 7: A diagram of the CB1 power controller. The real power stations physically connected to the grid are the applied FC and solar panels, and each of them supplies the SEM with approximately 200-300 W peak. The simple physical materialization, the safety of the experiments, and the low cost all enable the SEM to operate with 24 V\({}_{\text{DC}}\) and to store the surplus energy in electric car batteries. Instead of a large, centralized battery storage, the designed SEM employs a number of batteries, one for each power station. Although storing electric energy into hydrogen appears to be a less promising solution, a hydrogen FC (a metal-hydride container as serving as the hydrogen storage) will be integrated into the SEM to form a peak energy source. The data transfer from the remote energy sources is performed using the Global Systgem for Mobile Communications (GSM) data logger. The related power meters are located near the water and wind power plants, and the measured data of the immediate generated power are transmitted wirelessly (GPRS) to the control centre with the CompactRIO. The laboratory provides for wired connection (RS 232 or RS 485) between the CB1 and CB2 power controllers. The physical model of all the remote renewable energy sources (RES) is simulated by a QPX1200 SP 1200 W DC power supply (Huntingdon, UK). The RES battery is connected to the SEM via one of the CB1 control blocks, a bidirectional power switcher enabling us to pump power to and from the grid. The block comprises a controlled DC/DC converter for voltage adjustment (upward) and utilizes the power from the local 12 V batteries (which can supply from 8 V to 14 V, according to the current charge level). Based on the information from the meter, the CompactRIO regulates the voltage and employs the related CB1 to control the power supplied into the SEM; this power corresponds to that obtained from the remote energy sources. For any case where the energy produced by the RES connected to the SEM is greater than the total consumption of the SEM, each current regulator (CB1) is equipped with a controlled battery charger. According to the chosen algorithm, the SEM charges the batteries with controlled power until the selected recharge level is reached. Another physical source of the SEM is the FC; this cell is connected to the SEM via its own voltage regulator. The energy consumption from the grid is regulated by the CompactRIO control system and the CB2 box. The described smart grid part of the SEM is connected with the smart metering one [15; 16]. The actual smart metering and the consumption control represent a typical small energy consumer to participate in the smart energy system, utilizing the demand-response principle. Depending on the cost of the energy, an individual consumer, in cooperation with the control centre, will switch on or off the main electrical appliances in the household; in other words, and more generally, he or she will \"control\" their consumption. Importantly, household consumption is also simulated, including 30 appliances turned on according to their use during the day. The relevant tables invariably define the frequency and duration of an appliance's activity within a definite time period. The switching times are generated randomly to operate as close to reality as possible. From these data, we then obtain the total generated appliance power, which is recalculated and communicated partly to the real appliances in the laboratory and partly to the electrical load. The battery capacity and power output of the sources are used to calculate the individual appliance powers in such a manner that they correspond to the real operating conditions At this point, it is important to note that our model is 30-fold smaller than a real home network.