# Smart Grid Architecture for Rural Distribution Networks: Application to a Spanish Pilot Network
## 3 Electrical Actuations to Evolve the Rural Grid
### Back-Up Resources  
Diverse types of back-up resources can be adopted so as to improve the network reliability. One option is the inclusion of diesel generators. Such systems enable the isolated operation of the network, even in the absence of DGs and storage. Alternatively, one could opt for power electronic-based solutions. In this regard, the SRG project developed the IDPR [31; 39; 43; 44]. An IDPR, like diesel generators, enables isolated operation of the system in case of faults [45]. Thus, the IDPR is a device located at strategic nodes of the distribution network and its main goal is to control power flows. As can be seen in Figure 2, the PN is comprised of three IDPRs. There are only two IDPRs equipped with a Battery Energy Storage System (BESS) because of space limitations in secondary substations. In addition, an auxiliary diesel generator (GS) is set up in SS 010, thus enabling isolated operation in the absence of DGs and storage. Note also in Figure 2 that, in the case of protection devices, the back-up resources are also integrated into the PN through RTUs. The biggest challenge of the SRG project has been the development of an IDPR. This device is comprised of an innovative electronic-based power conversion system. The IDPR is a modular power converter connected in parallel with the low voltage grid and it can be connected with an energy storage device. Moreover, the control system of the IDPR is easily managed by the system operator setpoints as well as a permanent monitoring of the power flow upstream and downstream of its coupling point via Modbus RTU protocol In terms of performance, the power stage implements an extremely compact transformer-less topology based on the new highly efficient silicon carbide power semiconductor devices [26; 39; 45]. Figure 3 presents the IDPR architecture. The power converter is based on a determined number of controlled current source power cells, each of them based on two converters. Each power cell has its own control board (slave control), which is responsible for controlling the cell output current. The current setpoints are received on each cell from the master control through an Ethernet communication link, centralized in an Ethernet switch. In order to make the system safe in the event of a communication failure of the Ethernet link, a hardware wired output is included, allowing notification of any error in a cell to all other cells and to the outside of the power converter. The switching frequency of the converters is fixed to 30 kHz and the switching signals are synchronized by fibre optic triggers. The number of power converters depends on the number of stages of the converter (i.e., if it integrates a BESS) and the rated current in  
Figure 3: Architecture of an Intelligent Distribution Power Router (IDPR) with a battery [39]. each IDPR (i.e., the rated power of the IDPR). There are DC and AC switchgears consisting of a main relay and a precharge circuit. The function of these parts is to allow the precharge of the converter DC bus from both sides and to connect or isolate the power electronics to the outside (grid or battery) in order to respectively operate or turn off the converter. A thermal magnetic and residual circuit breaker protects the IDPR from an overcurrent, a shortcircuit or a ground fault in AC side. In addition, there are auxiliary circuits for ensuring that all the signals from the master control to/from the switchgears, emergency button, door sensors, and power cells are correctly adapted. Finally, the master control board is the responsible for managing the different power cells, and communicating with the battery management system and system operator [39]. The IDPR enables the integration of distributed generation, renewable sources, domestic and industrial loads and electric vehicles into the distribution systems. Moreover, it favours the integration of energy storage devices and, finally, it improves the power quality and grid support [46; 47].