Distributed generation
BATTERY Connection
board & Fuses BMS PLC-SCADA
Battery management Communication
Protection Breaker AFE Control & Communication DSP DC / AC AC DC AFE DC BUS 550-800 V DC Filter 400 V AC 50 Hz DSP DC / DC DC DC Pbat Pgrid / FPF
Fig. 24 shows a simplified connection diagram for a MV storage system in a distribution substation.
Similarly, Fig. 25 shows the connection of storage on the low voltage side of a distribution substation, where different distributed generation systems are also connected.
The functions that energy storage systems provide are: • Management of active power:
– Discharge line sections that are overloaded during certain time bands. – Act as a UPS for a certain Client of the DS.
– Reduce peaks of consumption-generation. – Reduce the losses in the line.
• Management of reactive power: Enables compensation of reactive power in the node where the storage is connected.
• Voltage monitoring: This enables the voltage of the MV connection node to be monitored, although this value will be strongly influenced by the installed storage power and the short circuit power.
The advantages of having distributed resources are only possible in an automated grid, with a decentralised control system that governs the flow of energy to improve the quality, maintenance, and safety of the supply. These monitoring algorithms are implemented in grid controllers (in Smartcity Malaga: iNodes and
iSockets), developments that are possible thanks to information and communication
technologies.
Fig. 24. Distribution
substation with storage connected to an MV node of the distribution grid
P M MV Line Distribution substations for Storage
The Smartcity Malaga project has integrated various systems of distributed generation and storage into the distribution grid of the city of Malaga, connected at the MV level (mini-storage) and at the LV level (micro-generation and micro-storage). Similarly, the iNodes and iSockets and their corresponding monitoring algorithms have been implemented.
Thus, 10 facilities for renewable generation and 2 for power storage in batteries have been integrated, as already stated in section 2.1. Fig. 26 shows, on a map of the Smartcity area in the city of Malaga, the location of the different elements of distributed generation and storage integrated into the distribution grid.
There are different storage methods that have been implemented and tested in Smartcity Malaga. We can divide them into three main categories:
• Optional storage, such as that carried out by the electric vehicle in its V2G function, and by the battery system within the microgrid on the seafront. They do not have an exclusive operation mode, but can be used either to supply the lighting or vehicles being recharged, or to inject energy into the microgrid.
• Instantaneous storage, to adapt to the grid connection of the streetlamps with wind turbines, designed originally to function in an island mode.
• Seasonal storage, such as that of the congress hall, a large storage point intended for very stable use, designed to be operated either by the customer directly or using set points or recommendations of the control and monitoring system of the smart grid. In the storage installations of the Malaga congress hall and the microgrid on the seafront, with a total capacity of 106 and 24 kWh respectively, technology based on lithium-ion batteries have been used, formed by carbon anodes and lithium, iron, and magnesium phosphate powder cathodes.
Fig. 25. Distribution
substation with consumption, generation and storage
P M MV LINE Endesa distribution substation Storage Generation Customer 1 [P,Q] Customer 2 [P,Q] Customer i [P,Q] P M P M P M P M P M
Solar Photovoltaic Storage Wind Cogeneration
Fig. 26. Distributed generation and storage in the Smartcity Malaga grid
• Regarding the low voltage grid, we must emphasise the microgrid connected to DS 80159, in the seafront area of Malaga, that integrates distributed generation, storage systems and manageable loads, as can be seen in detail in Fig. 27:
• Photovoltaic installation on 10 streetlamps, with 95 W each. Their location is marked in Fig. 27 with numbers 1, 2, 3, 4, 5, 8, 9, 10, 11 and 12 in red.
• Wind installation on 9 streetlamps, with 680 W each. The location of these
streetlamps is indicated in Fig. 27 by the numbers 54, 55, 56, 57, 58, 59, 28, 27 and 26 in pink.
• Isolated wind turbine of 4 kW, marked on the map with the symbol . • A storage system of 24 kWh, next to distribution substation 80159. • A recharge point for electric vehicles with V2G function.
The different systems of generation and storage integrated in this microgrid are described in more detail below.
Wind turbine of 4 kW
The wind turbine installed on the seafront, Urban Green Energy UGE-4K, has a maximum generation power of 4 kW. This wind turbine has a vertical axis of rotation, which enables it to be integrated aesthetically in urban environments, with space limitations and the need to preserve the aesthetics of its area. Fig. 28 (See Index of
figures, page 156) shows this unit.
Connected to the 4 kW wind turbine and with output to circuit 7 of the LV grid of DS 80159, an AURORA Power One PVI-7200 Wind Interface Box regulator, a resistive braking system, and an AURORA Power One PVI-6000 Inverter have been installed.
Photovoltaic streetlamp units and streetlamps with mini-wind turbines
The installation of public lighting has been carried out on the “Antonio Banderas” promenade, beside the new building of Malaga Provincial Council.
To connect the new streetlamps, the existing electrical installation was used with only small modifications to adapt it.
The lighting switchboard is supplied from the underground LV grid from DS 80159, through conductor RV 06/1 kV 3.5×150mm2 connected to the general low voltage
switchboard of the centre, at output 6. The connection between the LV circuit and the switchboard was made through conductor RV 06/1 kV 4×50mm2 and
compression connectors.
Fig. 29 and Fig. 30 shows images of these systems, where the integrated distributed generation units can be seen: wind turbines and photovoltaic panels.
Fig. 29. Micro-
generation systems integrated in streetlamps
The wind turbines integrated in the streetlamps are the model Urban Green Energy UGE-600, with a rated power of 680 W. Their rated wind speed is very low, 12 m/s, so they are capable of supplying energy even in areas without strong winds.
The 9 streetlamps with wind power generation are connected to circuit 6 of the seafront LV grid through a GPTech PV-5 inverter. This inverter connects to an iSocket for communication with the iNode located in DS 80159.
Regarding the photovoltaic system integrated in the streetlamps, the panels are provided by the manufacturer ATERSA, model A-95P, 95 W. The modules, as shown in Fig. 31, consist of 36 polycrystalline cells. Each module consists of a layer of glass with a high level of transmissivity. The encapsulate is made of modified ethylene-vinyl acetate (EVA). The connection of the set of 10 streetlamps with photovoltaic generation to circuit 6 of the LV grid along the promenade is made with a GPTech PV-1 inverter. Within the inverter there is an iSocket for communication with the iNode located in the seafront DS. Fig. 32 (See Index
of figures, page 156) shows the installation of this inverter and the GPTech PV-5.
With respect to the distributed storage, the energy storage systems installed in the Smartcity Malaga project are based on the use of batteries. Specifically, Valence
Fig. 30. Streetlamps
with integrated solar photovoltaic panels
Fig. 31. Photovoltaic module model A-95P from ATERSA
Tempered glass
Hook frame (aluminium) Black-Sheet
Ethyl-Vinyl-Acetate (EVA) IP54 connection box (with protection diodes) Ethyl-Vinyl-Acetate (EVA) High-performance cells CHARGER DC/AC RS 485 CANbus GRID CONTROL U-BMS-HV
+
-
14 U27-36XP 2 series strings of 7 modules connected in parallel Contactor ContactorLiFeMgPO4 batteries with individual storage capacities of 138 Ah at 12.8 V. The full
storage system consists of one rack, containing 14 batteries connected in series. Similarly, the charge and discharge monitoring system of the batteries uses the U-BMS- HV system.
Like the generation systems, distributed storage operates in direct current, so inverter systems are needed to convert this power into alternating current and integrate it into the distribution grid. The VALENCE storage system uses the inverter GPTechPV-15 as its regulation unit. In the same way as the inverters mentioned previously, inside the inverter there is an iSocket for communication with the iNode located in the seafront distribution substation.
The storage systems have been installed in cabinets like those shown in Fig. 34 (See Index of figures, page 156).