Summary of WP5 Deliverables - FLEXITRANSTORE

LCE-04-2017

Innovation Action

An Integrated Platform for Increased FLEXIbility in smart TRANSmission grids with STORage Entities and large penetration of Renewable Energy Sources

This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 774407

Summary of WP5 Deliverables

Report Identifier:

Work-package, Task: WP5 Status – Version: 1.00

Distribution Security: CO Deliverable Type:

Editor: ABG

Contributors:

Reviewers:

Quality Reviewer:

Keywords: ADN, BESS, Battery Energy Storage, Control, Cyprus, EMS, PCS, RTU, WAMS

Project website: www.flexitranstore.eu

http://www.flexitranstore.eu/

D5.1 Description and full documentation of the ADN’s detailed demonstration scenario

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Copyright notice

© Copyright 2017-2021 by the FLEXITRANSTORE Consortium

This document contains information that is protected by copyright. All Rights Reserved. No part of this work covered by copyright hereon may be reproduced or used in any form or by any means without the permission of the copyright holders.

Abbreviations

ADN Active Distribution Node

BESS Battery Energy Storage System

BMS Battery Management System

BOL Beginning of Life

BS Battery System

DSL Digital Subscriber Line

EMS Energy Management System

EOL End of Life

FAT Factory Acceptance Tests

FSS Fire Suppression System

GOOSE Generic Object-Oriented Substation Events

HMI Human-Machine Interface

HVAC Heating, Ventilation and Air Conditioning

ICT Information and Communication Technology

ISP Internet Service Provider

IT Information Technology

KPI Key Performance Indicator

MU Merging Unit

O&M Operation & Maintenance

OT Operational Technology

P2P Point-to-point

PCC Point of Common Coupling

PCS Power Converter System

PDC Phasor Data Concentrator

PLC Programmable Logic Controller


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PMU Phasor Measurement Unit

RTU Remote Terminal Unit

SAT Site Acceptance Tests

SCADA Supervisory Control and Data Acquisition

SOC State of Charge

SOH State of Health

UPS Uninterrupted Power Supply

VPN Virtual Private Network

VSC Virtual Synchronous Controller

WAMS Wide Area Measurement System


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Executive Summary This deliverable describes the conceptual and basic engineering phase of the ADN demonstrator to be installed in Athienou substation, Cyprus. The Cyprus grid code has been analysed in order to evaluate the benefits and challenges of the BESS which will be installed in the substation, as well as the operation philosophy.

There is also a general description of the system considering the main engineering areas: electrical, mechanical, communication and control, as well as a general overview of main equipment involved.

It shall be noticed that this is an initial stage of the project, and it will be subjected to an evolution during next tasks, especially in those aspects related to the control of the BESS.

The scope of the present document is a summary of the deliverables submitted for the WP5. At the current state of the project, it has been developed two deliverables, D5.1 and D5.2. It was scheduled a third deliverable to be submitted, but due to delays in the project and the Covid-19 situation, the works related to the deliverable D5.3, that include the installation and start-up of the demo, is delayed. In spite the deliverable is not available, there are many documents and works that will be included in the deliverable that will be also commented in the present summary.


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1 Summary Deliverable D5.1 The demonstrator of WP5 consist on an Active Distribution Node (ADN). This ADN proposed in the will be installed in Athienou substation (Cyprus) and consist on a BESS, based on Lithium Ion batteries, and all necessary equipment to be functional, installed in a single 40ft container. There are many other supporting devices that will be installed in the substation, and also in the BESS, in order to create a network where all necessary and relevant data can be collected and analysed, as will be described in detail below. Cyprus is a country with a high penetration of renewable energy resources, especially at distribution level. However, renewable energy resources usually have an important drawback related to the lack of stability and the variability of the weather conditions. There is other consideration to be taken into account related to the location of the substation that is the variability of the energy demand between summer and the rest of the year. With the installation of a BESS, this stability problem can be solved: the BESS can supply energy when climate conditions reduce the generation of energy from renewable resources. Nevertheless, BESS can provide other grid services that will be adjusted according to the Cyprus grid code analysis carried out by University of Cyprus (UCY), Electric Authority of Cyprus (EAC) and Transmission System Operator Cyprus (CTSO). This analysis leads to the description of the project operation philosophy, even though this is an initial and conceptual stage of the ADN description. In order to provide grid services in a considerable scale, the BESS will have a power of 1 MW and an energy capacity of approximately 2 MWh, as specified in the proposal. According to this specification and the constrains in the interconnection and equipment of the substation, a specification for BESS main equipment has been prepared and also a first version of the communication and control diagram based on RTU and measurement systems involved and the development of control algorithms and communication protocols has started. The first deliverable of the WP5 was D5.1 “Description and full documentation of the ADN’s detailed demonstration scenario”. This document described the general concept of the demo, a brief presentation of the partners involved and their duties, as well an initial description of technical solution and basic engineering, including a first approach to the following:

• Definition of communication protocols between measurement devices, BESS and substation

• Definition of communication diagrams

• Basic electrical and mechanical design of the BESS

• Analysis of grid services

• Analysis of Cyprus grid code and BESS

• Analysis and selection of main BESS equipment

The conceptual definition of the ADN consist on a 1MW / 2MWh BESS, connected through a MV cabinet to the existing substation of Athienou, in Cyprus. Athienou substation is a 11/132kV substation located near Athienou, between Nicosia and Larnaca.


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BESS will consist of one 40ft container where batteries and PCS will be installed, being part of a single unit container following a plug and play concept. The container will also include all the auxiliary equipment needed, such as Fire suppression system and HVAC to ensure a safe and reliable battery system operation since the beginning of the installation at site.

The deliverable described the equipment and technology selected for the BESS:

1.1 Battery System:

The battery technology selected for the BESS will be Li-Ion. Currently, this is the dominant technology for grid stationary applications, it already has a significant track-record of successful projects in operation, and the market consensus is that it will remain in this position in the near-term future. Some of the main advantages of Li-Ion technology are:

o High energy density. o High round-trip efficiency. o Low response time. o Low self-discharge

1.2 Power Converter System (PCS):

The PCS is the system in charge of converting power from the Energy Storage to the grid and vice versa complying with the required operation modes allowing a precise and fast control of both active power (P) and reactive power (Q).

The PCS will consist of the following components:

o AC/DC Converter. o Control Unit. o Connecting Bus bars. o Protections.

1.3 Control System

At this stage of the project, it stated the development of the 3-level control, currently developed by LUA, that will work in parallel with the EMS developed by Abengoa. An explanation follows describing how the 1st level controller (response controller) will interact with the BESS, exchanging operational parameters, commands and signal values with the BESS. A general structure showing the interface between the BESS and the 1st-level controller is demonstrated in Error! Reference source not found.. As shown in the figure, the BESS is connected to the 1st-level controller through two independent communication channels, i.e., the operational bus and the control bus.


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Figure 1. General diagram of the interface between the BESS and the 1st-level controller

1.4 Substation monitoring system

In this deliverable, there were describe a first approach of the communication system. The communication between the different levels is performed by using different communication protocols, like IEC 60870-5-101, IEC 60870-5-104, Modbus, DNP, etc. For FLEXITRANSTORE project, Schneider Electric is implementing IEC 61850 Process Bus standard to communicate through Ethernet between the RTU acquisition system and the RTU front-end.

Main requirements for the different RTU are the following ones:

o Possibility of acquiring data in real-time from different elements of the substation, as well as synchronization capabilities.


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o Data acquisition and processes for digital, analogue values inputs and outputs. o Support of communications through serial interfaces like RS232 and RS485. o Support of different tele-control protocols, to interact with other devices. o Support of IEC 61850 Process Bus based communications. o Control and monitoring of switching devices. o Visual indications about the RTU status (i.e., through LEDs). o Support of standardized and proprietary communication protocols.

1.5 Electrical design.

The objective of this point was to describe the basic design of the electrical installation of the electrical storage system. The design was carried out according to the objective of the project and therefore an energy sizing has been made to cover the needs of the electric plant.

The connection between energy storage system and the substation will be through an oil transformer and medium voltage switchgear provided by the substation. The electric line where the system will be connected is of 11 kV with an insulation voltage above 15 kV.

The low voltage winding transformer will be connected to a 40ft container, where the batteries are located, by an automatic switch with magnetothermal and overcurrent protection through which the system can be separated from the network. The system has two main electrical lines, one electric power line and another electrical line of auxiliary systems.

o Electric power line: This line will feed the converter and batteries with a power of 1

MVA.

o Auxiliary system line: This line will feed the following services of the container and

will be provided by the substation, in order not to reduce the capacity of the BESS.

▪ UPS. ▪ HVAC. ▪ FSS. ▪ Lighting. ▪ Emergency system. ▪ Control.

1.6 Mechanical design.

As explained in the general description of the project, BESS system will be integrated in a 40ft High Cube ISO container, which will contain all necessary elements to be operative as soon as it will be installed in the substation.

Mechanically, the container will have some modifications compared to the basic 40ft HC container that has been specified to the container manufacturer. Main modifications are:

o Container is internally divided in two zones: Battery room and PCS room.

o Two personnel access doors: one for the battery room and one for PCS room. Battery

room shall be fully accessible for personnel for maintenance and operation tasks,

meanwhile PCS room shall be accessible just for maintenance.


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o One side of the container will have a large opening for the PCS, due to the fact that it

will be operated from the outside of the container.

o Container surface will be prepared and painted to achieve a protection degree

appropriate for the location to avoid corrosion of the metal structure.

o Container will be insulated with rockwool sandwich panels, due to good fire behaviour

and good insulation properties. Insulation is useful due to the fact that batteries need

to be in a controlled environment. Temperature in the substation location can be high

during summer. Nevertheless, in order to control the room conditions, container will

have a HVAC system.

o For safety reasons, the installation of a fire detection and suppression system is highly

recommended, because lithium ion batteries fire can be very aggressive and requires

a very fast response in an event of fire. In this case, an aerosol fire suppression system

has been selected

In order to achieve a reliable and plug & play system, the container (with all the equipment

already described) passed a FAT in the manufacturer facilities before being shipped to the

substation.

1.7 Control and communication system.

A simplified diagram of the communication diagram of the first stage of the project is shown:

Figure 2. Facility concept design

In the same way, the initial communication architecture of the system was starting to be define:


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Figure 3. Information & Technology schema

1.8 Syncrophasor technology

The ADN will have installed syncrophasor technology devices for data acquisition at PCC. WAMS is based on PMUs that are deployed on different busses along the system. In large


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systems PMU cover backbone and the most important busses. However, Flexitranstore will require a so-called “pocket” WAMS. The target of this “pocket” WAMS is making the transmission system particularly prone to problems induced by high penetration of renewables. In such systems, like Flexitranstore project at Athienou substation, PMU are deployed at nodes (PCC) that can bring information for mitigating detected problems – e.g. reducing power flow on critical line or mitigate false tripping.

1.9 Chanllenges and benefits

Finally, there were an initial analysis of challenges and benefits that the demo will regarding the following substation boundary conditions:

• Relevant penetration of Renewable Energy Sources (RES) at distribution level • High variability of demand depending on the period of the year. In summer, energy demand

is much higher in comparison with the rest of the year

Regarding these conditions, the main challenges the demonstrator will face are the following:

• Frequency and voltage instability • Power factor correction • Power supply during peak periods of demand

Benefits that BESS can provide to the grid are limited due to the size of the system, only 1MW, that can be observed in the simulations done by Loyola University in task 4.1, for a standard electric network (IEEE 39-bus), not the real one for this substation. However, in spite of the fact that the impact on the grid will be low in this standard network, it can be observed that BESS will positively contribute to the frequency, voltage and power factor regulation.

As the BESS can provide power on high demand periods, the benefit on the grid will be positive but very limited due to the size, as mentioned before. The size of the BESS limits its impact to a grid of around 5000 MW as the network simulated by Loyola University. However, the analysis of the contribution of larger BESS derived from the demonstrator would be interesting, due the scalability of it.


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2 Summary Deliverable D5.2 The second deliverable related to the WP5 was D5.2 “Description of the engineering procedures of the ADN demonstrator and detailed specification of all components”.

This deliverable is a report of the work that has been developed during the task 5.2, ADN detailed engineering and system procurement, and a continuation of the previous task 5.1 and its deliverable (D5.1). Following to the D5.1, that was focused on a conceptual and basic engineering phase, the present deliverable shows the progress from the initial ideas to a specific system composed by a Battery Energy Storage System (BESS) and all the auxiliary systems necessary for the purpose of the ADN and the flexibility concept of the Flexitranstore Project. Some of the works related to the development of this task 5.2, are included in tasks of others WP, such as task 4.2, 4.3, 10.2 and 10.3. These tasks are related to the development of the control and communication system of the ADN, connecting, controlling and monitoring the BESS to the substation, and defining the procedures, considering the results of LUA simulations. According to the procurement process, during the task 5.2 the specifications of all the components of the BESS have been defined:

o Lithium Ion Batteries system of 1MW / 2MWh

o Power Converter System

o 40ft Container and auxiliary system features

o Electrical protections and interconnections inside the container

o HMI – Control equipment

o Power transformer from BESS to substation

2.1 Battery Energy Storage System BESS) – Detailed Engineering

ABG has led the detailed engineering of the BESS and its auxiliary systems. Main works related to this process are the following:

Definition of specification for main BESS components:

• Battery System (BS) • PCS • BESS enclosure • Power transformer • EMS hardware equipment • Development of the communication architecture and protocols in agreement with

LUA, EAC, SCHN, CTSO and STER • Description of grid services to be provided in agreement with LUA • Development of the BESS data modelling in agreement with LUA • Development of the AEMS (Abengoa Energy Management System) basis • Simulation and calculation of electrical characteristics of the BESS components • Simulation of thermal dissipation and HVAC design for BESS container


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• Simulation and calculation of mechanical loads for civil works definition

2.2 Battery System

In order to fulfill the requirements set for Flexitranstore Project, ABG has defined the specifications for suppliers to receive technical and economical offers of a 1 MW / 2 MWh battery system.

According to this, suppliers were requested the following scope of supply:

• Design and manufacture of BS, including provision of tools and other means required for installation/O&M

• BS FAT execution in Supplier´s premises • BS commissioning & start-up after completion of BESS assembly • O&M training • BS product documentation package

Parameter Value Unit

Net Power 1 MW AC

Net Energy 2 MWh AC

Operational Lifetime 10 Years

Response time < 100 ms

Availability >97 %

Minimum Voltage 610 V DC

Maximum Voltage 1000 V DC

Table 1. General Battery System requirements

Voltage range was defined according to typical PCS voltage range.

The definition of Net Power provided indicated that BS shall be able to discharge continuously at the net value at any SOC, within the total SOC range to be defined by supplier, at any time during a discharge cycle and whenever it is required during the whole project lifetime, regardless of the described charge/discharge pattern.

As part of the specification there was a requirement about BMS and the electrical protection (DC Switchgear).

The BS must include a Battery Management System (BMS) to allow remote operation of the BS and to monitor the main operation and status parameters.

Regarding the DC Switchgear, it was required that each battery rack must have its own fuse and rated DC circuit breaker/disconnector for protection.

ABG received several proposals from Lithium-ion battery manufacturers. Between those that fulfilled all requirements, the decision for awarding a supplier was made according to commercial


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aspects (price and warranties mainly) and track record in terms of previous projects in which the technology has been successfully implemented. In addition, it has been also considered the best value for money of each proposal received in terms of quality of the batteries and it characteristics, as commented in the Grant Agreement.

The awarded supplier has been Sungrow-Samsung SDI, a joint venture company that manufacture battery modules with Samsung technology.

Sungrow-Samsung has supplied at the beginning of 2019 a Li-ion Battery System of 2,176 kWh, including battery racks, BMS, Switchgear box and all necessary items for its integration.

The Lithium ion Battery System supplied relies on advanced Nickel Cobalt Manganese (NMC) chemistry.

2.3 Power Conversion System

In parallel to the BS specification, PCS specifications were elaborated to be sent to suppliers. As the project proposal indicates, BESS shall supply 1 MW / 2 MWh, so the PCS shall be able to handle at least 1 MW. The specification included the following general characteristics:

Parameter Value Unit

Rated Power at POI 1000 (pf 0.95) kW

Type Indoor -

Operational Lifetime 20 Years

Availability >98 %

Communication protocols Modbus TCP -

Table 2. General characteristics of the PCS

Main functionalities required to the PCS was the capacity of operating in all four quadrants at rated power. The PCS shall also be able to receive set points (P, Q) from EMS to execute the different control modes.

Suppliers were also requested to provide the following data:

• Capability curves, depending on DC Bus Voltage, AC Voltage Level and Impedance transformer

• Derating curves, depending on temperature and altitude.

ABG received several proposals from PCS manufacturers. Between those that fulfill all requirements, the decision for awarding a supplier was taken according to commercial aspects (price and


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warranties mainly) and track record in terms of previous projects in which the technology has been successfully implemented.

The awarded supplier was Ingeteam, one of the most important companies in the field of the PCS worldwide. They offer their INGECON ® SUN PowerMax STORAGE inverter, that is a bidirectional three-phase transformerless power converters, designed to work either in grid-connected, stand-alone and self-consumption modes, that offer grid-support functions through Reactive Power (Q), Frequency and Voltage regulation, among others.

This inverter is certified for outdoor use; however, it can be installed indoor having some considerations regarding the ventilation.

Figure 4. Ingeteam PCS

2.4 BESS Enclosure

In order to make a compact and plug-and-play BESS, ABG designed in agreement with EAC and CTSO a BESS installed in a 40ft HQ container. This design allows ABG to install all components in their facilities in Seville and making tests before sending the BESS to Cyprus, in order to make a safer and more reliable system and to correct possible deviations before the final installation.

ABG elaborated a specification for portable electrical rooms manufacturer to receive technical and economical offers that fulfill with the requirements and the preliminary design made on the task 5.1.

An evolution of the design leads to the following layout:


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Figure 5. BESS Equipment Arrangement

From the layout:

• DC SW Panel is the panel where DC switchgear and fuses are installed, to protect BS. • LV Panel is the panel where all power supply devices to each DC switchgear of each

battery rack and battery module fans. • HMI is the panel where all the equipment for the AEMS is installed. • AC SW Panel is the panel that connect the PCS AC Module to the transformer. It

includes an automatic switchgear to protect the system. • UPS to cover outages. • Auxiliary transformer to feed the electrical devices and auxiliary systems inside the

container. • HVAC system to maintain the temperature inside the container in the range specified

by the battery manufacturer (23 ± 5ºC).

As it can be seen in the layout, PCS will be installed inside the container, but shall be operated from outside regarding its outdoor feature. Ventilation of the PCS is guaranteed thanks to the grille located in the rear front of the container.


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Figure 6. Render of Flexitranstore BESS

2.5 Power Transformer

The power transformer that connects the BESS to the Athienou Substation is part of the scope of supply of ABG. ABG, in coordination with EAC and CTSO and the PCS manufacturer, has defined the characteristics of the power transformer.

Parameter Value Unit / Remarks

Type Oil Type Outdoor

Power 1,2 MVA

Voltage 11/22 / 0,45 kV

Frequency 50 Hz

Connection Dd -

Isolation class 11 kV

Phases 3 -

Coil Material Al -

Temperature probe For each phase -

Temperature Switchboard Yes -

Electrostatic screen Yes -

Lifting points Yes -

Table 3. Main characteristics of power transformer

2.6 BESS Control Equipment

Among the control and communication equipment, it is necessary to differentiate between the control of the BESS including its auxiliary systems, and the ADN Control. The control of the BESS is in development by ABG. It is the so-called AEMS and it will control the status of the batteries, HVAC, PCS…

In order to develop this system, ABG has designed an HMI panel, installed inside the BESS Enclosure. This panel include a PLC, an embedded PC, an HMI monitor, a switch, a protocol gateway and a powermeter.


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2.7 ADN Control Equipment

As part of the development of the ADN Control, LUA has developed the specification for the components dedicated to the 3-levels control system, especially for 1st and 2nd level.

The process followed included some basic designs for each block, or subsystem, and then completing the detailed design by including the different elements to provide reliable and safe operation of each block. The technical discussions about different approaches to implement the basic design led to a long iterating process of proposals in order to achieve the best solution.

A list of components has been defined as follow:

• PLCs • Computers (i3, i9) • Protection devices • 24VDC Auxiliary power supply units • Cooling fans • Communication switches, with and without time-stamped capabilities (PTP protocol

used) • UPS, 2-3 kVA

2.8 Breaker IED

This Breaker IED is a new development in the project. It will be a compact device with integrated digital I/O, but able to be extended with additional acquisition modules if necessary. It will be used in the Cyprus substation to monitor and manage a breaker of the new RMU to be installed at the substation.

2.9 Control IED

Apart from that, Schneider Electric will provide the Control IED of the substation, which is an existing RTU (MiCOM C264C), in which a new board integrating IEC 61850 Process Bus communications is being developed.

2.10 Ring Main Unit

The equipment for the interconnection between the substation and the BESS through the transformer is a MV Switchgear located in the substation.

EAC has selected Siemens type 8DJH for secondary distribution system. This switchgear is a 3-pole metal enclosed and single busbar for indoor installation, specially designed for the use as local ring main unit at utility substations.

It has a rated voltage of 12 kV and a RRML configuration, which means:

• 2 Ring Main feeders • 1 Busbar voltage metering panel • 1 Circuit breaker feeder


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Figure 7. RMU Topology (Siemens 8DJH Catalogue)

The RMU will include Current and voltage transformers to measure current and voltage and use them for the control system of the ADN.

2.11 ADN Communication Diagram

One of the most important issues that has been developed during the development of D5.2, is the communication relationships between the existent equipment and the monitoring and operation system in the substation, and the new elements that the project introduce. This issue has been discussed long time between all partners involved in the WP.

Several revisions of the communication diagram have been done in order to achieve the best solutions and integration among all the elements. At the present status of the project, the diagram is in a very advanced status, however it is still a living document, due to it is not defined yet if PMUs can be used for the demo and even the final topology of the networks at substation level.

All the information included in the previously presented BESS data model will be available through the different networks included in the communication architecture design.

A detailed view of the interaction between the BESS and the rest of the elements of the AND is depicted below:


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Figure 8. BESS Communication integration in the AND (initial version)

The front end element of the BESS is the Abengoa Energy Management System (AEMS) that performs the control and monitorization of all inner elements of the container, and also monitors the Point of Common Coupling of the storage system and the status of the Ring Main Unit (RMU) switchgear, where the system is connected at the substation.

The data flow will be distributed in three communication networks, the BESS LAN, where all the internal elements of the container will be connected, the Process Bus LAN, where all the equipment with high speed sampling rate will be connected and the Substation LAN, that will gather the rest of the equipment. Remote communication will be also possible in order to provide information to external applications and also for O&M purposes.

Therefore, the AEMS will collect information from the battery, the power conversion system and all the ancillary equipment such as UPS, ventilation and fire suppression system to actuate at the point of interconnection according to the parameters and orders received through its communication server.


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Figure 9. Information flow diagram

The AEMS will also have an available interface connection for the Flexible Energy Grid (FEG) platform, making easier the quantification of the performance of the battery system by providing critical information as the system state of charge, state of health, battery cell data, etc.

Table 4. FEG Platform and ADN connection


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2.12 Services and functionalities

The ADN control layer architecture has been designed to perform the control of the electrical characteristics at the Point of Common Coupling to comply with regulatory requirements and economic constraints.

The application development applied to this has a high innovative component, including the design of the data modeling and the transmission of information through standard protocols.

The figure above describes the conceptual approach of the ADN application layers, showing the relationship between the main components of the BESS and the ADN.

Figure 10. ADN Application layers approach

The power injection/absorption of energy from the BESS is controlled by the Abengoa Energy Management System (AEMS), which will be in charge of:

• Control and Monitoring BESS (SCADA)

• PCS & BMS managing

• Batteries SOC Management

• Monitor system degradation

• Auxiliary Systems Control

• Orders and set-points from upper control layers

Regarding the control capabilities of the system, the proposed architecture defines each control mode as one independent module that can be activated or deactivated without any impact in the


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operation of the remaining modules and ensuring a smooth transition during the activation/deactivation process.

2.13 BESS Engineering additional calculations

As part of the detailed design of the container, some simulations have been run to optimize the BESS container and to have information for the installation at site.

2.13.1 Mechanical design

As commented before, the BESS has been designed to fit in one 40ft HQ container, to make a compact and plug-and-play concept system, to ease the transportation and installation in Cyprus, as well as ease the tests to be done in Abengoa facilities in Seville.

From a mechanical point of view, the standard container has received interesting changes and adaptation works. However, these modifications do not affect to the integrity and structural safety of the container.

There has been made four main perforations on the container walls:

• Two perforations on one of the long side, one for a personnel access door and one for the PCS.

• One perforation on one of the short side, for a personnel access door. This door leads to the back side of the PCS and the AC SW Panel and will be operated in a very few occasions.

• One perforation on the other long side, for a big ventilation grille. This grille is necessary because the PCS requires a big quantity of air for refrigeration. PCS takes the air from the front side and exhausts it through the back.

Each personnel access door is equipped with anti-panic bar to ease the evacuation of personnel if necessary. They are also equipped with groom door closer, to avoid dangerous movements of the doors.

In one of the front of the container, there is a double door, typical of maritime containers. This door is very useful for the integration of the equipment, but during the operation will be opened in very few occasions, just for maintenance.

Inside the container, main mechanical modifications consist on the installation of a rockwool isolation sandwich panel (for thermal and safety reasons that will be explained later) and the insertion of a separation wall between the battery room and the PCS room, to achieve a better climate control in the battery room, and even for a better protection against fire.

In this sense, one of the most important point for the enclosure design is the safety. ABG has drafted the container to get the maximum safety standards for the people and other equipment. To achieve this, the design has paid special attention to the following issues:

• Fire protection • Battery safety protection • Personnel protection • Facilities protection


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2.13.2 Fire protection

As part of the Substation requirement and also as fire protection measure, enclosure shall withstand it stability in an event of fire during at least 60 minutes. To get this, the isolation material of the container has been modified from 50 mm as initial proposal, to 80 mm. According to the rockwool panel manufacturer, 80 mm is certified to resist more than 60 minutes without structural damage.

In the way of minimizing damages in case of fire, container includes an automatic detection and extinguishing system, composed by an innovative and efficient condensed aerosol. Unlike gaseous agent, the chosen system achieves the total flooding of the enclosure, without increasing the pressure of the protected area. Fire extinguishing is accomplished by the interruption of the chemical chain reaction, and not by the depletion of oxygen or cooling as suggested by the traditional triangle of fire:

• Cooling – Absorbing heat from the fire • Starvation – cutting-off the fuel supply • Smothering – removing or reducing the oxygen

The chosen system (aerosol system) inhabits the chemical chain reaction on a molecular level, without depleting the oxygen. The main component of the aerosol is potassium salt-based (K2CO3), N2 and CO2.

The solid particles of Potassium salts, which are of a few microns in size, are suspended in an inert gas that displays an extremely high surface to reaction mass ratio - a fact that increases efficiency - which results in less quantities of fire extinguishing agent required.

When the condensed aerosol reaches and reacts with the flame, Potassium radicals (K*) are formed mainly from the disassociation of K2CO3. The K*s bind to other flame free radicals (hydroxyls - OH-) forming stable products such as KOH. This action extinguishes fire without depleting the ambient oxygen content. KOH reacts further in the presence of CO2 and forms K2CO3.

The solid particles of Potassium Carbonate (K2CO3) have a diameter of less than five microns and remain in suspension in the protected room/enclosure for at least 30 minutes, preventing further re-ignition of the fire.

The system is certified for use on class A, B, C & F fire hazards according to EN2 and A, B & C fire hazards as per NFPA 10.

In addition to the detection and extinguishing system, the container includes an external visual and audible alarm in case of fire.

2.13.3 Electrical design

The objective of this chapter is the detailed description of the electrical installation, focusing on the principal equipment, connections and the main protections to maintain the normal operation and security.

The electrical installation of the BESS includes all equipment that are connected electrically inside the container. The BESS will be connected to the substation through of a power transformer of 1 MVA and it will be protected by a medium voltage switchgear placed at control room of the plant, the Ring Main Unit (RMU) that EAC is purchasing for the substation.

The BESS contains two principal electrical lines with different objectives. One of them is the power line to connect the principal equipment of the plant, bidirectional converter and batteries and the second one is the electrical line to feed the auxiliary services of the BESS container. These auxiliary


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services will be connected to the grid by a transformer of 30 kVA, that is the calculated consumption of these services.

The auxiliary services are separated in essential services and not essentials services depending of the its final application.

The principal electrical equipment that can be seen in the diagram are two transformers (one for the substation interconnection and one for auxiliaries), power converter, batteries, Uninterruptible Power Supply (UPS) and the electrical protections. It is described below the protections of each element:

• Power transformer: this element will transform the medium voltage of the grid (11 kV) to low voltage (450 V) to feed the BESS plant. The configuration of the transformer is a delta-delta (Dd) configuration because the converter needs this type of configuration in the low voltage winding. The transformer contains several protection devices to operate in a normal mode (Temperature sensor, earthing, electrostatic screen, etc.)

• Auxiliary Services Transformer: It is an isolation transformer and adapts the voltage to 400 V for the power supply of the auxiliary services of the system. It has a delta-star (Dyn) configuration and is protected to withstand overcurrent and short-circuit.

• Power Converter System: The specifications have been defined before, this is one of the most important equipment of the system because it converts the DC current from batteries to AC current and control the flows of the active and reactive power in order to supply the different grid services that has been defined in the project. The converter is designed with several stages which are dedicated for different purposes (Switch, filter signals, protect, control, etc). The stage of protection has a circuit breaker in AC and contactors in DC; however, to protect overcurrent and short-circuit fuses will be installed at output of the converter. Moreover, in the AC inputs the converter will be protected with an insulation monitoring device. The control of the converter provides SW protection communicating with several sensors that have been connected in order to obtain measurements and to manage the operation.

• Batteries: The most important equipment in the BESS are the batteries and for this reason it will be necessary to protect and to operate in very goods conditions. The protections are integrated in the BMS where it will have ultra-fast fuses per pole and contactors to open / close the system. Other protections are switchgear protections which are managed for the control taking measurements of temperatures, overcurrent or voltages per cells.

• UPS: It will be the equipment that supply energy in case of outages of the service. The principal objective will be to maintain the power supply for essential auxiliary services. These services are the controls of the principal equipment. The inputs and outputs of the UPS are protected with circuit breakers while the protection of the UPS´s batteries are with fuses.

2.13.4 Electrical protections

Regarding to the protections of the plant, the principal protections we integrated inside the container. All elements are in three cabinets from where they are interconnected to the different lines and equipment, conducted by the container through trays.

Before starting the description of the panels that are integrated inside the container to protect electrically the system, it is necessary to indicate that over the principal transformer, placed at


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substation, it will be a medium voltage switchgear at connection point with capacity to separate the substation and the BESS.

• AC Panel: Inside AC Panel, it will be installed a switch disconnector to isolate the BESS to the transformer, that is the separation between substation and the container, and a circuit breaker to protect for overcurrent and short-circuit the low voltage installation of the system. The AC Panel includes lights to indicate voltage at input and output side.

• LV Panel: The LV Panel has two main lines that feed the auxiliary services. Each line contains a circuit breaker with differential protection of 300 mA. The essential services, which they need 24 V, will be fed by power supplies changing 230 V AC to 24 V DC. All loads are protected with circuit breaker and, in some cases, they are also protected with differential switches.

Regarding to balance of charges, all bipolar charges have been connected in the similar form between R, S y T phases and the neutral line. The tripolar charges have been connected directly to the three phases.

• DC Panel: The DC Panel has been designed with the objective to protect the DC side of the installation. It is composed by a load disconnector switch to isolate the batteries and to protect overcurrent or short-circuit it has been installed fuses. The DC Panel disposes of lights to supervise the voltage.

Electrical interconnections have been calculated, inside container between racks and DC panel, and DC Panel to PCS; and also for the interconnection from the BESS to the substation.

However, to obtain the best solution to connect the batteries racks, that is a sensitive part of the installation, ABG has simulated different cases:

2.13.5 Electrical simulations

In order to eliminate losses and to avoid a malfunction in the charge or discharge of the batteries, ABG has simulated several cases of interconnections between battery racks and DC Panel:

• All racks are connected to a copper bus bar • All racks are connected with cables with different length • All racks are connected with cables with the same length, the longest cable possible

from DC Panel to the farthest rack.

The connection of the battery racks with cables with different length, it could have different levels of state of charge (SOC) at the end of the charge between racks, due to the impedance of the electrical lines changes. For this reason, it has studied the possibility to install cupper busbar instead of cables. Other studies have been done to simulate the connections with cables with the same length and to oversize the sections of the cables to do not obtain more losses and to keep the state of charge equal in all racks.

To simulate the different options, it has been used batteries models in Simulink, controlled current sources, resistances to simulate length and sections of the cables. The battery models contain the


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real parameters provided by the battery supplier, such capacity, maximum current in charge or discharge, voltage ranges and response time.

Knowing the values of the impedance of the cupper busbar and cables and the distance between racks, it is possible to simulate a close to real electrical installation. Other important parameters will be the area and conductivity of the cupper to obtain good results.

The Figure 11 and Figure 12 show the result for the case cupper busbar 50x10 mm for the 26 racks connection. The results represent the charge of the system, showing the state of charge (SOC). It can be observed that not all racks finish it charge at the same time, creating a difference between racks in functions of them distances to the DC Panel.

Figure 11. Result of SOC simulation with 50x10 mm Copper bar

The Figure 12 is zoom of the end of the charge simulation, that shows the differences between racks 1 and rack 26. While the rack 1 has reached the 100 % of the SOC the rack 26 is in the 97 %, furthermore the difference is a 3 %.


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Figure 12. Detail of the result of SOC simulation with 50x10 mm Copper bar

To compare the results obtained in the simulations, the following list indicate the differences of SOC between the cases.

Cable cases:

• Cable (Cu) 50 mm2 --> dif (SOCcable) = 3.6 % • Cable (Cu) 70 mm2 --> dif (SOCcable) = 2.5 %

Cupper busbar cases:

• Busbar (Cu) 50 x 10 mm --> dif (SOCbar) = 3 % • Busbar (Cu) 60 x 10 mm --> dif (SOCbar) = 2.5 % • Busbar (Cu) 80x10 mm --> dif (SOCbar) = 1.9 % • Busbar (Cu) 100 x 10 mm --> dif (SOCbar) = 1.2 %

Furthermore analyzing the situation of the different points of view, electrically, mechanically or thermally ABG conclude that the best option for this case is to install the same lengths of cable oversizing the section to 25 mm2.

2.13.6 HVAC Calculations

As mentioned before, the design of the container has had special caution with the climate conditions inside the enclosure to maintain the temperature and humidity requirements under control.

In addition, ABG has performed some simulations to get the best solutions, having in mind the concept of compactness.


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The type of HVAC chosen is a split system, with two internal machines and two external units. The design criteria were focused in the coverage of the heat loads from the batteries, to maintain the temperature around the area where the batteries are installed. As mentioned before, temperature for the batteries shall be 23ºC ±5ºC.

A CFD simulation has been done as part of the BESS design process. The objective is to verify the validity of the HVAC design solution proposed for the containerized Battery Energy Storage System (BESS).

A 3D model has to be created to build the simulation domain. The 3D model represents the container´s battery section and all equipment installed that is relevant for simulation purposes (mainly the battery racks, the HVAC equipment, and other electrical equipment). PCS section of the container is not included as it is physically isolated. Following the approach of the objective of the CFD simulation, geometry of all items has been simplified using hexahedrons and rectangular prisms. The idea is to remove all vortexes and other fluid dynamics phenomena that involves any increase of computational time but does not provide any relevant information for the simulation objective. Main equipment for simulations purposes are:

• Battery modules • HVAC equipment

Both are modelled in a similar way, as enclosures with air entrances/exits, heat/cold sources, and air fans, to simulate the heat dissipation/removal and the air flows produced.

There are 2 HVAC units inside the battery section, each of them with a rated power of 9.5 kW of rated power (sensible + latent cooling power). HVAC units are modeled as heat removal units with constant power as there are no data available to model the performance variations of the units associated to the variations of boundary conditions.

A CFD simulation provides a comprehensive amount of data, but CFD software packages have proper tools to handle these data. A very usual way to represent the results using colour maps (for scalar magnitudes, such as temperature, pressure, etc.) and vector maps (for vector variables, such as speed, force, etc.). Figure 13 shows an example of a temperature color map in the container. It shows two longitudinal plane cuts in the middle of the battery modules depth, close to the container walls. It shows some spreading along the corridor length, but maximum values are within the allowed range. Temperature distributions in both planes are very symmetrical. This is a good sign as symmetry should be expected due to the equipment distribution inside the container.


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Figure 13. Temperature distribution along batteries corridor

2.13.7 Mechanical calculations

For the purpose of the calculation for the civil works, it has been done a preliminary calculation of the reactions of the container in the several supporting points. To distribute in a better way the weight of the complete BESS container, including the equipment, there are eight fixation points. It has been designed some special devices to connect the container with the pillars. These devices are bolted to the lower container beam and it will be fixed to the foundations that substation designed.


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Figure 14. Fixation points position

It has been calculated the reaction forces on the 8 fixation points.

With the data shown above, ABG has performed a static calculation to indicate the center of gravity (COG) position and the reaction forces on each fixation points.

Figure 15. BESS Fixation points and COG position

This calculation that will be refined at the end of the BESS enclosure integration. It shall be considered that these results include the battery modules integrated in the container, and that the weight for the transportation will be much lower, since the battery modules will be transported in a separated and refrigerated container.

At the moment of the D5.2 submission, the transformer was not yet purchased, so ABG had no final data about weight and requirements for the civil works.

Summary of WP5 Deliverables - FLEXITRANSTORE

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