HomeMy WebLinkAbout3AUP000A130-V3 Rev0Copyright 2015 ABB. All rights reserved.
External doc. no.
Based on Project 12225KW Kotzebue ESS
Prep. Javier E. Mendoza 4/23/2015 Customer SAFT / KEA
Appr. Tom Harper 6/26/2015 Proj. no. 1333580
Doc. kind Doc.
des. Ref.
des.
Title Control Concept
Resp. dept PSPC Status Released
ABB
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3AUP000A130-V3 en 0 No. of p. 13
FILE: 3AUP000A130-V3 Rev0 ConceptofControl; SAVEDATE: 06/26/2015 16:04; TEMPLATE: TECHN_DOC_DELIV_P.dot B; SKELETON:
Control Concept
SAFT / KEA
1225KW ESS
KOTZEBUE, ALASKA, USA
PROJECT: 1333580
Doc. kind Project 12225KW Kotzebue ESS
Title Control Concept Customer SAFT / KEA
Proj. no. 1333580
ABB
Doc. no. Lang. Rev. ind. Page 2
3AUP000A130-V3 en 0 No. of p. 13
Table of Contents
1 LIST OF ACRONYMS .................................................................................... 3
2 CONTROL ARCHITECTURE ......................................................................... 4
3 INVERTER BASE MODES ............................................................................. 5
3.1 CSI Mode .......................................................................................... 5
3.2 VSI Mode .......................................................................................... 5
3.2.1 VSI PQ ................................................................................ 5
3.2.2 VSI VF ................................................................................. 6
3.2.3 VSI ISO ............................................................................... 7
3.2.4 Control Strategies in VSI VF or ISO ..................................... 8
4 CONTROL MODES IN VSI PQ ....................................................................... 9
4.1 Scheduled Dispatch .......................................................................... 9
4.2 SOC Management .......................................................................... 10
4.3 Manual Mode .................................................................................. 10
5 ISLANDING AND SYNCHRONIZATION ...................................................... 11
5.1 Micro Grid Synchronization ............................................................. 11
5.2 Islanding and Resynchronization of Two Separate Grids ................ 11
5.2.1 Going Into Islanded Operation ........................................... 11
5.2.2 Going Back To Grid Connected Operation ........................ 12
6 REVISION .................................................................................................... 13
Doc. kind Project 12225KW Kotzebue ESS
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1 LIST OF ACRONYMS
Acronym Phrase
AGC Automated Generation Control
BMS Battery Management System
CSI Current Source Inverters
ESS Energy Storage System
GDM Graphic Display Monitor
HMI Human Machine Interface
IBL Inverter/Battery Lineup
LV Low Voltage
LUC ABB Local Unit Controller
PCC Point of Common Coupling
PLC Programmable Logic Controller
PCS Power Conversion System
PQM Power Quality Monitor
MUC ABB Multiple units controller
SOC State of Charge
VSI Voltage Source Inverters
VF Voltage and Frequency
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2 CONTROL ARCHITECTURE
The ESS control system consists of the following 4 components for a single lineup ESS.
Component Description
Battery
Management
System (BMS)
Responsible for battery system supervision and protections. The BMS must at
the very least communicate battery voltage, current limits and SOC back to the
LUC. The communication is done over Modbus TCP where the LUC acts as
master and the BMS as slave.
Inverter Controller Responsible for operation and supervisor of the inverter modules. The inverter
controller also implements the inverter base modes (see section: 3 INVERTER
BASE MODES). It communicates with the LUC via Modbus RTU.
Local Unit
Controller (LUC)
Responsible for operation of the Inverter & Battery Lineups (IBL’s). As well the
LUC supervises the IBL enclosure. In single enclosure installation, the LUC will
implement the higher level controls and will provide the client interface.
Client Interface Client communication to the LUC depending on the system.
Figure 1: Diagram of a system with higher controls implemented at the LUC.
PCS Enclosure
LUC01
Supports up to 4 inverter
controllers
Supports up to 4 BMS
Control inverter startup
and stop sequence
Control inverter cooling
Controls enclosure
environment
Implements higher level
controls
Inverter Controller
Responsible for operation
of the inverter modules
Responsible for inverter
system protections
Implements Inverter base
modes
BMS
Report back
battery
status to
LUC
Protect
batteries
Client Interface
System
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3 INVERTER BASE MODES
The inverter controller is capable of operating in two modes, Current Source Inverter mode (CSI) and
Voltage Source Inverter mode (VSI). It is not possible to switch between CSI and VSI mode while the
modules are running (IGBT’s switching), the modules must be stopped to make this transition, therefore
either in shutdown or standby mode. It is recommended to operate in CSI mode unless the ESS needs
to be able to switch into islanded operation unexpectedly, if so the ESS must operate in VSI mode.
3.1 CSI Mode
CSI mode presents a high impedance source to the AC grid. The inverter controller operates with a power
set point (P&Q control) and provides a fast positive sequence fundamental AC current response. Main
points to consider:
Provides balanced 3-phase sinusoidal currents to the grid regardless of grid conditions.
Works only with P and Q set points.
Has faster response to P and Q set points.
Cannot be used to island.
Minimizes DC ripple current on the DC storage.
Parameters
P Set Point Real power reference in kW.
Q Set Point Reactive power reference in kVAr.
3.2 VSI Mode
VSI mode presents a low impedance source to the AC grid, using “virtual generator” technology which
mimics a typical generator with “synthetic inertia”. Main points to consider:
VSI mode can operate in three variants: VSI PQ, VSI VF and VSI ISO.
The inverters can switch between the three variants while running.
VSI mode must be used if the ESS is required to switch to islanded operation automatically upon
grid loss detection.
3.2.1 VSI PQ
VSI PQ mode is similar to CSI in that it regulates to a P&Q set point with slightly slower response than
CSI due to the virtual generator’s synthetic inertia.
Parameters
P Set Point Real power reference in kW.
Q Set Point Reactive power reference in kVAr.
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3.2.2 VSI VF
VSI VF mode regulate the voltage and frequency at the inverter terminals with regard to the voltage and
frequency set points. The response is characterized by the voltage and frequency droops. This mode is
mainly used for islanded operation on a grid with other parallel generators with larger capacity than the
inverter system i.e. the inverters are not forming the grid.
Parameters
F Set Point
Frequency set point in hertz, note that the frequency set point and droop will govern the
real power response only.
F Droop Frequency droop in percentage. The droop defines the response slope. For example
assume a frequency set point of 60Hz and droop value of 1%. This defines an upper
limit of 60Hz + 1%*60Hz = 60.6Hz and a lower limit of 60Hz – 1%*60% = 59.4Hz.
At the upper frequency limit the inverters will charge at nominal power. At the lower
frequency limit, the inverters will discharge at nominal power.
V Set Point Voltage set point in volts, note that the voltage set point and droop will govern the
reactive power response only.
V Droop Voltage droop in percentage. The droop defines the response slope. For example
assume a voltage set point of 480V and droop value of 4%. This defines an upper limit
of 480V + 4%*480V = 499.2V and a lower limit of 480V – 4%*480V = 460.8V.
At the upper voltage limit the inverters will output at nominal inductive power. At the
lower voltage limit, the inverters will output nominal capacitive power.
Figure 2: Droop curve for a unit with nominal power of 1000kW, frequency set point of
60Hz and 1% droop.
-1500.0
-1000.0
-500.0
0.0
500.0
1000.0
1500.0
59.2 59.4 59.6 59.8 60 60.2 60.4 60.6 60.8
Power Outut (kW)Frequency (Hz)
Power Output (kW)
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3.2.3 VSI ISO
VSI ISO mode regulates the voltage and frequency at the inverter terminals with regards to the voltage
and frequency set points but unlike VSI VF does not accept droop set points. The inverter operate like a
grid forming generator keeping the grid frequency and voltage as close as possible to the set points. This
mode is used for islanded operation when the inverter system is the only source of generation or is the
largest source of generation. If the load exceeds the capacity of the ESS the grid parameters will fall out
of range.
Parameters
Frequency
Set Point
In hertz, this is the target frequency.
Voltage
Set Point
In volts, this is the target voltage at the inverter LV terminals.
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3.2.4 Control Strategies in VSI VF or ISO
An advantage of operation the ESS in VSI VF or ISO is that it will quickly respond to changes in the grid
and therefore help with grid stability. The PCS100 regulates to the frequency set point, higher grid
frequency will force the system to charge. If the micro grid’s renewable sources are producing more
power than the site requires this should create an increase in frequency and therefore the excess power
would be absorbed by the ESS. When batteries nears full charge, the charge current limit will decreas e
and the ESS will no longer be absorb power from the grid, therefore it is the client’s responsibility to
monitor the batteries’ SOC and have an appropriate curtailment scheme in place.
If the loads are higher than the renewable production, the remaining power to the loads will be provided
by the generators and ESS. The ESS’s output to the load will depend on the droop settings. However,
since the ESS has a smaller inertia than the generators, it will react first to a change in load conditions.
When batteries nears full discharge, the discharge current limit will decrease and the ESS will no longer
be able to supply power to the grid, therefore it is the client’s responsibility to monitor the batteries’ SOC
and have enough generation capacity online to take over the load.
Figure 3: PCS100 VS Diesel Generator Response to Load Steps
If the client wishes to charge the ESS while it operates in VSI VF, the client would be responsible for
bringing additional generation online to charge the ESS to maintain an appropriate SOC. The SOC is
available over the standard Modbus interface.
-100
-50
0
50
100
150
200
250
300
0 200 400 600 800 1000 1200 1400 1600 1800 2000Power (kW)Samples (every 250ms)
PCS100 VS Diesel Generator Response to Load Steps
Load kW
Gen kW
Inverter kW
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4 CONTROL MODES IN VSI PQ
4.1 Scheduled Dispatch
If scheduled dispatch is active, the ESS will dispatch active and reactive power based on the profiles
defined on by the time tables. There are 2 time tables, one for workdays and one for weekends. A time
tables allow the user to enter up to 12 break points. Break points are a time of day at which the reference
to the inverter is set to change. In this fashion the inverters can be made to follow a defined profile.
Reference after a break point remains until next break point is reached.
Time Table Parameters
Enable Enables scheduled time table logic.
dS/dt Common rate of change for all power set points for all break points.
Break 1 Break point 1
Break 2 Break point 2
Break 3 Break point 3
Break 4 Break point 4
Break 5 Break point 5
Break 6 Break point 6
Break 7 Break point 7
Break 8 Break point 8
Break 9 Break point 9
Break 10 Break point 10
Break 11 Break point 11
Break 12 Break point 12
Break Point Parameters
Enable Used to enable or disable a specific break point
Time Start time for a given break point
P Set Point Real power reference for a given break point in kW,
Q Set Point Reactive power reference for a given break point in kVAr.
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4.2 SOC Management
SOC management is allowed in the following situations:
If the ESS is placed into SOC management mode, in which case no other active compensation
routines are executed.
When SOC management is allowed, the ESS supervises the battery’s SOC. The user provides a target
SOC and dead band. If the battery’s SOC goes outside of the dead band, the ESS will either charge or
discharge the battery until the target SOC is achieved. SOC management then remains idle until the SOC
falls outside of the range again.
Parameters
SOC Set Point SOC Target in percentage (%)
SOC Dead Band SOC dead band in percentage (%), defines a range around the SOC set
point. When the battery SOC goes outside of this range, the SOC
management logic executes.
SOC Management
Max kW Reference
Max power reference which can be used for SOC maintenance.
SOC Management kW
Reference Ramp Rate
Ramp rate used for SOC management power references.
4.3 Manual Mode
In this mode, the client provides a direct active and reactive power reference to the ESS. This allows the
client to use their own site management logic. The client must command the lineups individually so as to
be able to handle issues such as different states of charge.
Parameters
P Set Point Real power reference in kW.
Q Set Point Reactive power reference in kVAr.
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5 ISLANDING AND SYNCHRONIZATION
5.1 Micro Grid Synchronization
The term micro grid is used to refer to a small grid completely independent from any larger grid. Even
though a micro grid may be called an island, this term is normally not applicable to a micro grid
applications unless there is a small part of the micro grid which becomes islanded from the micro grid. It
is typically never necessary to synchronize two separate grids in a micro grid. If the micro grid is being
established by the generators, then the ESS will automatically synchronize to them on startup. If the
micro grid is being established by the ESS, then the generators will synchronized to it on startup.
Therefore, the synchronization procedure described in this following section does not normally apply to
micro grids.
5.2 Islanding and Resynchronization of Two Separate Grids
Islanded operation occurs when the ESS is disconnected from the main grid and feeds only local loads.
Islanded operation is only possible in VSI mode. The client may command if islanding is allowed.
5.2.1 Going Into Islanded Operation
Islanding is initiated by the opening of the grid tie breaker:
If the ESS is already operating in VSI VF droop mode or VSI VF Iso (no droop) mode, it will simply
continue to feed the local loads.
If the ESS is operating in VSI PQ mode, it will automatically switch to VSI VF mode and continue
to feed the local loads.
If the ESS is operating in CSI mode, it will trip since islanding is not possible in this mode.
If islanding is not allowed, the system will trip.
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5.2.2 Going Back To Grid Connected Operation
The synchronization sequence must be commissioned by an ABB service engineer, failure to properly
configure this function will likely result in equipment damage. It is necessary to synchronize the ESS’s
islanded grid back to the main grid before reconnecting the two, failure to do so will likely result in
equipment damage. Only one PCS100 inverter lineup can be synchronized at a time using the procedure
described here. System with multiple PCS100 inverter lineups will require a synchronization relay (this is
not described in this document).
To synchronize a PCS100 inverter lineup:
The client latches the synchronization command.
The PCS100 synchronizes and provides a feedback to the client.
The client closes the grid tie breaker.
The client removes the synchronization command.
Required Feedbacks
Grid Tie Breaker
Closed Status
Hardwire grid breaker position indication, required to be able to switch to
islanded operation.
Grid Sync Voltage
Feedback
Three phase PT feedback from the main grid required for the
synchronization.
Parameters
Islanding Allowed System will remain online when grid tie breaker opens if true.
Synchronization
Command
Command to begin the synchronization process
Status Indication
PCS100 Synchronized Indication that synchronization is complete and that the grid breaker may be
closed.
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6 REVISION
Rev. ind. Page (P)
Chapt. (C)
Description Date Dept./Init.
A ALL Released 04/28/2015/TH
0 ALL Released 06/26/2015/JEM