9. Ley General de Asentamientos Humanos
9.2. Regulaciones a la propiedad en los centros de población
Medium voltage
Regarding products associated with energy storage in MV, it is important to highlight the design and installation of the system connected in the distribution substation of the Malaga congress hall.
improved, reducing the cost. Similarly, the process gives the cathode powder excellent properties of duration, conductivity and ease of processing.
The batteries consist of cylindrical cells with a rated voltage of 3.2 V that are joined together to make blocks by connecting the positive and negative electrodes with metal plates so that the cells are connected in parallel. The cells are joined in parallel, increasing the energy per block, by connecting them in series. The voltage of the battery is the sum of the voltages in the blocks connected in series; thus the rated voltage of the battery module is 12.8 V, and has a range between 10 V and 14.6 V, depending on the load status. The energy of each module is 1.766 kWh.
The complete assembly of installed batteries consists of 60 modules, connected in two series of 30 modules with each module having 12.8 V and 138 Ah. Therefore, the series achieve a voltage of 384 V, and 276 Ah, storing a total of 106 kWh. This energy can be discharged in one hour, providing the value of rated current, or in half an hour giving values of approximately double the rated values.
Each battery module has a monitoring unit which communicates, via RS-485, with the battery management system (U-BMS). This monitoring includes temperature, voltage, current and charge status, in addition to other multi-level alarms. Each control system is capable of communicating with up to 100 battery modules. The U-BMS communicates through a CAN bus with the communication units of the installation’s central control
Fig. 73. Diagram of control in distributed mode
i-Socket 1 VSCunit VSC unit VSC unit VSC unit VSC unit i-Socket 2 i-Socket 3 I-NODE Distributed operation i-Socket i i-Socket N Diesel generator Battery bank Wind turbine Non-priority Load Priority Load e e P2, Q2 P1, Q1 Pi, Qi PN, QN PN*, QN* Pi*, Qi* P3*, Q3* P2*, Q2* P1*, Q1* P3, Q3
system, and can send status and alarm signals, and receive commands. It also has four outputs for the control of relays or similar battery protection elements.
In addition, the monitoring element can also function in isolated mode, with no communication, acting as the only control unit of the batteries, saving the alarms and statuses in a data logger to be downloaded by an operator.
The batteries are connected to the grid through a power converter, that on one hand is responsible for rectifying the alternating current to convert it into the direct current needed to supply the batteries, and, on the other hand acts as an inverter to convert the direct current that the batteries provide into alternating current to be injected into the distribution grid. The converter used consists of a three phase rectifier bridge, a three phase inverter bridge, a continuous current filter, and a control and communications module. In addition, this unit has a DC/DC converter, so the voltages of the electronic circuit board and batteries are compatible. Both converter bridges have IGBT type transistors as interrupting element, which are tripped with fibre optic drivers.
The storage system control unit consists of a programmable logic controller equipped with the following boards:
• CPU with two Ethernet ports. The first is for communication via Modbus TCP with any other control element of the system, and the second (VPN) is used to communicate via Internet with the programmable logic controller and to be able to activate and deactivate the system, obtain information on its status, change the operation mode and, in general, any other action that may be carried out remotely.
• Communication board with two CAN ports for communication with the battery management unit.
• Board with three RS-232/RS-485 ports for communication with the electronic protection relay.
• Profibus-DP communication board for communication with the power electronics. • Digital input cards for receiving binary signals coming for auxiliary units, such as
alarms from cells, climate control, fans, power cabinets, etc.
• Boards with digital relay outputs to send binary signals to the auxiliary units. • Input power supply at 230 V AC.
The communication of the programmable logic controller signals can be made through a conventional telephone network for data communication, using TCP/IP protocols, through a backup system of wireless telephony, should there be a failure in the wired telephone connection, or through Power Line Communication (PLC), using the energy wiring as a means for the communication.
Fig. 75 outlines, diagrammatically and on a plan view of the building, the installation carried out in the distribution substation of the Malaga congress hall. Fig. 76 shows a diagram of the implemented communication.
Low voltage
In the field of distributed storage, one of the main products developed in the Smartcity Malaga project is a bidirectional domestic storage system installed in the microgrid on the promenade. The purpose of the system is to flatten the demand curve and reduce the consumption peaks that can exist in domestic loads, with the possibility of controlling the reactive power.
Endesa
Centro de Monitorización y Diagnóstico SCADA
WIMAX Endesa
WIMAX ISocket IEC 61850
WIMAX ISocket IEC 61850
WIMAX ISocket IEC 61850
MT measure PV panels
9
5
6
SAN RAFAEL PALACIO DE FERIAS 2 STORAGE LOADS 3 Non selected loads 4 AC DC BACNET AIR CONDITIONING CABINET BACNET MEASUR E & PROTECTION STORAGE CONTROLFig. 76. Mini-storage in the distribution substation of the congress hall. Communication diagram PLC-IC3 BMS CCU PMM LOCAL SCADA Start up & Maintenance
Remote SCADA INGETEAM
Endes a Centro de Monitorizació n y Diagnóstico SCADA GateWay Switch VPN INTERNET Palacio de Ferias
Plant Control System
Remot e MT Measure Switch Switch MEASUREMENT V W A VAR Phl Wh Modem 3G Modem 3G PV Panels LOADS BACnet Wimax IEC 61850 Wimax IEC 61850 Wimax IEC 61850 MODBUS MODBUS-TCP MODBUS-TCP CAN-BATTERIES P-DP PMLink (O. F.) ETH ETH ETH ETH
Mode 1: The charging and discharging of the unit are programmed, depending on the status of the battery charge:
• The battery will be charged at night, which increases the demand in these hours and it is discharged during times of maximum demand in the home (programmed by the user). It shall be charged at a constant current and with a low charge rate (as recommended by the manufacturer for cyclical applications) to obtain a greater efficiency at the end of the process. Likewise, it shall also be discharged at a constant current, with a discharge rate programmed by the user and in the desired time bands. • The charge/discharge status will depend on the battery charge status.
• The battery will never be charged at times of maximum demand.
• When the charging period begins, the battery will be in a situation of minimum voltage. To ensure this, if the energy stored in the battery exceeds a certain minimum value, the battery will provide energy, even if the power consumed does not reach the maximum pre-set value, depending on the time of day. This behaviour will guarantee that the battery will always be fully discharged, which safeguards the useful life of the battery and at the same time achieves maximum energy efficiency.
Mode 2: Like in mode 1, the system will be charged at night, in the hours of lowest demand, and during the day it will deliver constant power, except when the maximum demand element installed in the home detects overconsumption. When the power consumed is above the house’s maximum threshold, the domestic storage system is activated, if it was not already, to compensate the excess energy consumed. Thus, while the energy stored and the power of the unit allows it, more energy than the contracted level can be consumed without problems, decreasing the consumption peak required from the grid. In addition, after responding to a consumption peak in the home, the system recalculates the plan for the remaining energy in the battery to remain within the established hourly program.
Mode 3: Remote control by an external management company. Using a standard fieldbus, one or more domestic storage systems can communicate with a unit that manages the operation of all of them. Thus, the consumption peaks are not only compensated at the level of the home, but also between several homes. At the same time, the instantaneous measurements of the consumption made in the home, the operation point of the Domestic Storage System (DSS), and the batteries’ charge status are accessible through this same fieldbus.
To meet the objectives and operating modes described, the key characteristics of this product are the following:
• It is a two-way storage system, in other words, both charging and discharging are possible through the same unit.
• The system is connected to the single-phase grid of the home as yet another electrical appliance, with a conventional Schuko socket of 16 A (grid: 230 V rms and 50 Hz). • The system uses electrochemical batteries, with the objective of flattening the demand
curve and reducing the peak power consumed by the home.
• The maximum power that the system is capable of absorbing or delivering to the grid is 2 kW, measured at the mains connection socket.
• The control system adjusts the input or output power according to the predicted operating modes. The system has a simple human-machine interface so that the user can program the operating parameters. Similarly, the system is fitted with a communication interface that allows the connection with the maximum demand element installed in the panel of the home (this communication with the maximum demand element is wireless, and takes into account that various units must coexist in the same radio-electric space).
• The optimum usage of the battery places conditions on the system operation. In other words, if at a given point in time a certain action that is harmful for the battery is required of the system, this action will be limited to prolong its life cycle.
• One of the “non-functional” requirements defined for this unit is that it is as silent as possible. Taking into account that the energy will be stored in the batteries during the night, it is preferable if this appliance does not emit any sound due to the switching of the power electronics or mechanical elements.
• The thermal design of the unit ensures that the fan is hardly ever turned on, especially during the night. To do this, a heat sink has been selected that cools the electronic circuit board by natural convection and radiation. The fan is therefore only for contingencies and it only comes on in the event of operation with excessive power during extended periods, which rarely occur during the night.
• To avoid the switching of the electro-mechanical elements, the system remains in “stand-by” mode when at rest. To reduce the losses in this state a toroidal transformer with a very low reluctance and, therefore, low loss was used. To improve its stability, an algorithm for the dynamic compensation of imbalances in the hysteresis cycle has been implemented.
So that the batteries are safe, the following criteria have been taken into account: • The rated voltage of the batteries has been limited to what is considered very low
voltage in the EC Regulation on Low Voltage Electrotechnical Regulation.
• Galvanic insulation has been included with respect to the electricity grid in the direct current sections.
• All the anti-islanding protection stipulated in the Low Voltage Electrotechnical Regulation has been included: grid over- and undervoltage, and grid over- and underfrequency. Thus, the unit is disconnected from the electricity grid as soon as it detects that there is no connection to the electric supply network, for example if, due to maintenance, the master switch of the home has been opened.
Therefore, the DSS is an ideal unit for use inside the home, as it is even safe in exceptional situations such as floods.
Fig. 77 DSS developed shows a photography of the product developed (See Index of
figures, page 161).
The benefits of the unit are summarised in Table 2.
The connection diagram of the DSS inside the home is shown in Fig. 78:
The maximum demand meter monitors the electricity demand in the home and sends it wirelessly to the storage unit. Depending on the operation mode selected, the current status, and set points received by the storage unit from the exterior, it decides how much power, both active and reactive, must be delivered or absorbed.
Additionally, the active power metering by the maximum demand meter, and all the values measured by the storage unit are accessible remotely by means of a MODBUS RTU fieldbus on RS-485 with two wires. This fieldbus can control up to 31 devices which can be connected in one line with a theoretical maximum length of 1,200 metres.
Fig. 78. Connection of the DSS
DSS
Maximum demand
meter
Other loads Other loads Home
switchboard Grid
Table 2. Characteristics of the DSS developed
Connection to the network
Rated voltage of the grid 230 V
Rated frequency of the grid 50 Hz
Maximum phase current 8.7 A rms
Maximum active power 2,000 W
Maximum reactive power 2,000 var
Maximum apparent power 2,000 VA
If the apparent power limit is reached, the control system prioritises the monitoring of the active power set point against that of the reactive power. In addition, other limitations were implemented to guarantee the integrity of the system:
Limitation of the power for charging and discharging the batteries to prevent it exceeding its voltage, current or thermal limits.
Automatic reduction of the active and reactive power injected if the Ferranti effect is detected on the grid. Connection to weak networks without causing overvoltage problems on the grid.
Connection to batteries
Rated voltage of the batteries 48 V
Maximum charge/discharge current 50 A
Includes a BMS algorithm for the management of charging and discharging, and the estimate of the SOC for different technology types such as NiCd and Lithium-ion.
Protective devices
— Overcurrent in the connection to the mains electric
— Overcurrent in the connection to batteries — Overvoltage in the DC-bus
— Overvoltage in the batteries — Undervoltage in the batteries — Overheating in the power electronics — Overheating in the battery
— Short-circuit in the connection to the batteries
— Short-circuit in the connection to the electric mains
— Short-circuit and desaturation in the power electronics
— Overvoltage in the electric grid — Undervoltage in the electric grid — Overfrequency in the electric grid — Underfrequency in the electric grid — Islanding
— Protection against control failures (watchdog)
— Protection due to excess losses
— Protection against supply defects in the control and in the drivers of the power electronics
Communications
— Wireless communication (433 MHz) with the maximum demand meter — Complete management of the unit by MODBUS RTU on RS-485.
— Possibility of connection to SCADA system for monitoring, control, statistics and historical data.
Fig. 79. Power converter of the DSS L2/2 L2/2 50/230 ~ ~ Cbus L1 Vbat
Fig. 80. Control structure implemented
Filtering Measures Boards Control WP10 Set point Gen. Time Gen. / 7 Igrid / 8 Ibat_Con_Time Ibat_Con Duty_PH Duty_BB Internal
config. Controllog
Maximum demand element Clock User Current time Pmaximum demand element Phome Sub-interval No. Sub-intervals Night-day interv. limits
Psad_Average
Because the batteries operate in DC and the electricity grid functions in AC, a power electronics topology has been developed to convert the energy between both sources, thus allowing both battery charging and discharging, and considering the specifications of the system (such as the single-phase connection). The topology implemented is a cascade of two converters; a diagram of this is shown in Fig. 79.
The electronic circuit boards necessary for this product were designed and manufactured exclusively by the CIRCE research centre; from the concrete specifications of each board, the design of the algorithm and its subsequent routing, to obtaining the physical board, properly drilled, insulated, welded and checked.
For the connection of the converter with the corresponding iSocket, a Modbus-type interface has been included on the two wire serial RS-485 line. The map of the bus connection boxes was imposed by the iSocket to guarantee compatibility. Using the variables shared with the iSocket, the system has the possibility of modifying the reactive power that the converter absorbs or injects into the grid.
The system control is structured in various functional blocks interconnected by signals, which divide the global problem into simpler problems so they can be tackled individually. This method is known as top-down design and is very commonly used for problem solving in complex designs. Fig. 80 shows the overall structure of the control with the partition made between subsystems and the communication.
This section describes the main products developed in the Smartcity Malaga project, in the area of efficient demand management. These products make it possible to offer the new services for active demand management explained in section 3.