byd dc power supply system for substation_20130614

8/11/2019 BYD DC Power Supply System for Substation_20130614

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BYD DC Power Supply System

for

MEA

Version No. / Modification No.: A/0

2013.06.14


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I

Content

1 Project Introduction ............................................................................................................................... 1

2 Supply Range .......................................................................................................................................... 2

3 System Solution ..................................................................................................................................... 2

3.1 System Characteristics and Technical Strength ......................................................................... 2

3.2 System Technical Parameters ..................................................................................................... 4

3.3 System Protection Design ........................................................................................................... 4

3.4 System Function Design .............................................................................................................. 5

3.4.1 Battery System .................................................................................................................. 6

3.4.1.1 Battery .................................................................................................................... 6

3.4.1.1.1 Single Cell ..................................................................................................... 7

3.4.1.1.2 Battery Module ............................................................................................ 8

3.4.1.2 Battery Cabinet Design ........................................................................................... 9

3.4.1.3 BMS Design ........................................................................................................... 11

3.4.2 Charger ............................................................................................................................ 20

3.4.3 Communication Topology ............................................................................................... 21

3.4.4 Control Strategy .............................................................................................................. 21

4 System Installation Requirements ...................................................................................................... 22


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Bui ld Your Dr eams 1

1 Project Introduction(1) Background

MEA now has almost 200 substations in operation. Most of them are transformingvoltage from transmission voltage (115kV or 69 kV) to distribution voltage (24 kV or 12

kV) system. In each substation there are many switching equipment for the control,

operation and protection of the power delivery system.

These switchgears are all powered by DC source located within each substation, both

in normal operation and during the power outage.

These DC source come from Battery. They are all Ni-Cd battery now. BYD will provide

Li-iron phosphate 110VDC power supply system to replace the Ni-Cd system.

(2) Technical Requirements

Load: DC110V, 300Ah, 5hours backup

Voltage controlled shall be within 1% regardless of variation in load between

0 and 100%

Frequency variation 50Hz5%

Main voltage fluctuations 10%

(3) Environment Requirements

Altitude :approximately mean sea level

Maximum ambient temperature :40

Average ambient temperature in any one year :30

Average relative humidity in any one year :79% Average maximum relative humidity in any one year :94%


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2 Supply RangeThis 110VDC power supply system consists of Li-iron phosphate battery, battery

management system and DC charger. Supply range is showed as below:Table 2-1-1 Supply range list

Items Name Type Unit Quantity Remarks

1 Battery C12 pcs 72

2 BMS Set 1

3 DC Charger Including power module and switches Set 1

4 CableIncluding power cable, communication

cable and distribution cableSet 1

3 System Solution3.1 System Characteristics and Technical Strength

Adopt BYD mature, safe and reliable Li-iron phosphate battery which already beenwidely used in DC power system of BYD PV station and energy storage system,

other battery energy storage system and BYD electric vehicle e6 and K9.

The design and testing for Li-iron phosphate battery are followed UL 1642.5 th and

IEEE 1625-2004 standard.

Modularized design with simple configuration, easy for maintenance and

Installation.

Intelligent BMS with balancing for single cell and battery and battery moduledynamic consistency to ensure reliable and long time operation for battery system.


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Fig.3.1-1BYD 1MWpPV Station DC Power System

Fig.3.1-2 BYD 1MW-4MWhBattery Energy Storage System DC Power System


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3.2 System Technical Parameters

Rated capacity for energy storage: 39 kwh

Input voltage/frequency: 230/400 50Hz; three phases four lines

Output voltage: 110VDC

Table 3.2-1 System Parameters

ITEMS PARAMETERS REMAKS

1 System rated voltage DC110V

2 Input voltage range 400V10%

3 Input frequency range 50Hz5%

4 Rated output voltage DC115V

5 Output voltage range DC115V1%

6 Ripple factor 0.5%

7 Voltage stabilization accuracy 0.5%

8 Current stabilization accuracy 0.5%

9 Current-sharing unbalance 5%

10 Noise 55 dB(A)

11 Allowed ambition temperature +0 +40

12 Allowed relative humidity 10% 95% Non-condensing

13 Allowed Elevation 2000m

14 Installation Indoor IP20

15 External communication type CAN

3.3

System Protection DesignThere are perfect protections for battery system and DC charger to ensure the system

and maintenance workers safety. System protection includes but not limited below

items:

Automatic recovery protection

Below protections are all automatic protections. At the same time, adjustments for

the system failure warning value through remote or local monitoring system are

allowed; receive the control system warning information from clients side thenresponse as requirements to lowest the system potential damages.


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Battery over-current protection

Single cell over/low voltage protection

Single cell over/low temperature protection

AC over/low voltage protection

DC over/low voltage protection

Communication abnormal protection

Manual recovery protection

If failure value is in the range of protection, the protection can be recovered

automatically. When the value is over the protection range, manual recovery or

replacing is needed. Battery short-circuit protection

Battery isolated monitoring

Short-circuit protection

Grounding failure protection

Emergency stop protection

Contactor abnormal protection

Grounding protection

3.4 System Function Design

This system consists of battery system and DC charger. 36pcs C12 batteries are in

series as one array, two arrays are in parallel as one battery group to connect with one

6.6KW power module to realize uninterrupted DC power supply as below:


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400VAC

SOURCE

DC LOAD

CB2100A

CB3100A

CB4

100A

CB1

32A

Battery andBMS

Charger

MK

DW

Fig.3.4-1 DC Power Supply Topology

Working principle of the DC power supply system:

(1) When the AC input is normal, 400VAC will be transferred to 110VDC through

power rectification module to provide power supply to the 110VDC loads.

400V AC SOURCECB1MKCB2DWCB4DC LOAD

When the battery capacity is not enough, power from 400VAC will also charge

the battery. 400V AC SOURCECB1MKCB2CB3Battery.

(2) CB3 is a polar switch module which can be controlled, when the battery is

fully charged, battery cannot be charged continually; when there is no

electricity from grid, battery will provide power continually through CB3 with

seamless switch.

(3) When there is something wrong with the grid, close the discharging loop

through CB3, battery will provide power to the loads continually.

BatteryCB3DWCB4DC LOAD.

When the AC power recovery, battery will stop discharging, the system will

work as (1).

3.4.1 Battery System

3.4.1.1 Battery


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3.4.1.1.1 Single Cell

Adopt BYD C12 Li-iron phosphate battery with squareness aluminum shell through

strict producing and checking to ensure the quality of the battery.

Fig.3.4-2 BYD C12 Single Cell

Table 3.4-1 C12 Single Cell Parameters

NO. ITEM PARAMETER REMARK

1 Cell type C12

2 Nominal Voltage(V) 3.2

3 Cell charge cut-off voltage (V) 3.6

4 Cell discharge cut-off voltage (V) 2.8

5 Cell nominal capacity(Ah) 200

6 Cell nominal capacity (Wh) 640

7 Volume ratio of energy (Wh/L) 182.5

8 Weight ratio of energy (Wh/kg) 106.7

9 Voltage sampling channel 1

10 Temperature sampling channel 1

11 Enclosure material Aluminum

12 Cell shell flame retardant rating ULV-0

13 Cell dimension(mm) 58146417

14 Cell weight(kg) 6.0


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3.4.1.1.2 Battery Module

Each battery module consists of 4 single cells in series. Single cells voltage and

temperature monitoring are included in the battery module. Each single cells rated

capacity is 190Ah; named voltage is 3.2V, 4 cells in series as one 12.8V 190Ah battery

module. Battery module can increase the safety, reliability and easy for installation

and maintenance.

enclosureBMU

cell module

Fig.3.4-3 Battery Module

Table 3.4-2 Parameters for Battery Module


1 Battery module nominal Voltage(V) 12.8

2 DOD 90%~95%DOD Recommend

3 Battery module charge cut-off voltage (V) 3.6V Cells highest voltage

4 Battery module discharge cut-off voltage (V) 2.8V Cells lowest voltage

5 Charge current (A) 40A(Standard)

200A(Max. constant current)

6 Discharge current (A) 40A(Standard)

400A(Max. constant current

@25)

7 Nominal working temperature ( ) 25


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8 Working voltage range ( ) +10~+40 Without derating

9 Connection method between modules Bolt or connector

10 Enclosure material PPO

11 Modules Dimension(mm) 474285170mm

12 Sampling circuit interface Connector type: Tyco

connector 1318774-1

13 Voltage sampling channel number 4

14 Voltage sampling frequency >1Hz

15 Voltage sampling Accuracy 2%

16 Temperature sampling channel number 4

17 Temperature sampling frequency >0.25Hz

18 Temperature sampling Accuracy 2

3.4.1.2 Battery Cabinet Design

36 cells are in series as one array, 2 arrays are in parallel as one group using 2 units

BYD BMS. Two arrays battery, fuse type isolated switch, contactor, checking unit,

sampling line, BMS control unit are all placed in one battery cabinet.

QS

KM

CTR

BMS

36 battery cell

_

Fig.3.4-4 Battery Array Intelligent Sketch


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Fig.3.4-5 Battery Cabinet Design and Installation Sketch (for reference)

Fig.3.4-6 Appearance of Battery Cabinet (for reference)


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The intelligent type for battery system and voltage range is all suitable for the power

module voltage output and loads voltage requirements.

Table 3.4-2 Battery System Parameters

Items Specification Remarks

1 Cells quantity for one battery array 36pcs

2 Battery array parallel quantity 2array

3 Battery array voltage range 100.8V 129.6V This range can be set through software.

4 Battery rated voltage 115.2V Rated voltage for single cell can be limited.

3.4.1.3 BMS Design

The proposed unit adopts BYD self-developed battery management system for the

LiFePO4 battery, each battery management system including:

Battery management unit (BMU);

Battery Gateway Unit (BGU);

Battery electrical controlling Unit (BECU);

Battery stack management unit (BSMU).

The functions of BMS shows below ensure normal, stable and reliable operation of the

batteries.

Battery status monitor

Operation control

Insulation monitor

Dynamic balancing management

Protection alarm

Communication

1) BMS Principle and Characteristic

The BMS monitors the voltage and temperature of single cells, and the current of the

battery string in real time. It calculates the State of Charge (SOC), State of Health (SOH)

of the battery string, detects the insulation status, and also communicates with the


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upper machine, sends alarm information, conducts protection action, balance cells

and so on.

IMD

Module 10

Module 18

BMU10

BMU18

BGU2

BSMU

BECU 2V T

V T

CAN CAN

Module 1

Module 9

BMU1

BMU9

BGU1 BECU 1V T

V T

CAN CAN

Fig.3.4-7 Schematic diagram of BMS structure

a) BMU Principle and Characteristic

Every module is equipped with one BMU, the functions of BMU are as following:

Monitor the voltage of each single cell in the module and track the real-time

battery voltage changes;

Monitor the temperature of each single cell in the modules and track

real-time battery temperature changes.

Battery balancing -balance cells to ensure battery consistency;

With isolation CAN communication interface transmitting battery voltage,

temperature and alarm information, and also communicate with BGU to

accept system level management.


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Fig.3.4-8 Schematic diagram of BMU installed position

b) BGU Principle and Characteristic

Each battery string is furnished with one BGU. The BGU communicates with the

BMU on the battery module in real time through CAN interface to monitor the

battery status of battery modules and send the battery voltage, temperature and

alarm information to the upper management unit. The upper management unit

will then control battery modules working status based on the information sent

by BGU to ensure safety operation of the module.

Fig3.4-9 Schematic diagram of BGU enclosure

c) BECU Principle and Characteristic

Each battery string is furnished with one BECU. The BECU communicates with the BGU

of the battery string through CAN interface to manage the working of the whole string,

controlling the battery string working state base on the information sent by the BGU,

to insure the safety operation of the battery string.


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Fig.3.4-10 Schematic diagram of BECU enclosure

The functions of the BECU contain:

Battery information management: cooperate with BGU, BMU to manage the

voltage and temperature of every cell, deal with the alarm information sent

by BGU, BMU and then feed back to the upper manager;

Monitoring and control of the battery string state including voltage monitor,

temperature monitor and current detection, etc.;

Control of the on-gird operation or off-gird standby status of the battery

string;

Battery balancing control: manage the balancing of the whole string and

cooperate with the BMU to balance battery;

Power circuit relay control: control the on and off of the battery string circuit

to make the battery string status (on-grid or off-grid) controllable;

Pre-charge circuit relay control: control the on and off of the pre-charge

circuit relay;

Alarm: take judgment of any battery string fault and send alarm informationbase on the state of monitored information;

Communication: provide communication interface to send information to the

upper system and meanwhile accept the management from the upper

system;

Charge and discharge management: control the start and stop of battery

string charge/discharge, monitor the battery operation state during the

charge or discharge process;


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Self-protection: when the BECU detects serious fault of the battery string (i.e.

no upper management instructions issued), the BECU will automatically enter

the protection state, opening the power circuit switch, stopping execute

charge/discharge command and sending fault alarm information.

d) BSMU Principle and Characteristic

The battery stack management unit (BSMU) manages multiple strings, namely one

BSMU corresponds with multiple BECU to form a battery stack system. The BSMU

is in charge of the operation of the whole battery stack.

Fig.3.4-11 Schematic diagram of BSMU

BSMU functions contain:

Information management: collect and deal with the information of the

corresponding battery strings and send out the necessary information to the

upper monitoring system.

Battery status monitoring: monitor the state of each string and control the

battery to carry out on-grid or off-grid action to manage the battery

operation state.

Event statistic and logging: cooperate with the relative storage devices to

storage the working events, and by the logging of the events, the history can

be checked and analyzed.

Communication: communicate with other devices through CAN or RS485

interface to manage the system working mode together.


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Insulation detection: Each battery management systems are equipped with

insulation monitor equipment (IMD) and this device is mainly used to detect

the insulation character between DC system power circuit and the earth.

Once the insulation grade drop, the insulation monitor will send alarm signals

immediately and the BSMU will prohibit the charging or discharging of the

battery strings. Principle of the insulation detect unit is shown as below.

IMD

cathode

anode

batterystring

Fig.3.4-12 Schematic diagram of IMD application

2) BMS Functions

a) Detection

(i) Detect single cell voltage and temperature in real time;

(ii) Detect the total voltage of the battery string to determine whether the

battery strings can connect to the grid;

(iii) Detect the charge or discharge current of the battery string in real time. With

high sampling frequency, current change can be quickly followed;

(iv) Detect the state of fuse and power circuit repair switch to determine whether

the system can operation;

(v) Detect the insulation state of power circuit to earth to determine whether


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insulation reducing situation occurs.

b) Dynamic Balancing ManagementAs many batteries work in series, capacity imbalance between the cells will affect the

whole string capacity. The string available capacity then decreases due to battery

capacity imbalance. As the total available string capacity is decided by the lowest

battery capacity, the battery balancing is necessary to keep the string available

capacity.

BYD BMS adopts dynamic balancing method and all batteries can be automatically

balanced online.

The BMU, cooperated by the BECU and the BGU, decides whether the batteries need

balancing according to the status of single cells and the use state of the battery string.

When the single cell voltage imbalance, the single cell status differ within the string.

The BMU will start battery balancing action to make the whole string batteries charge

and discharge status to be consistent.

Advantages of BMU balancing function:

Online balancing;

Dynamic balancing: Synchronization balancing can be achieved during battery

operation;

Cumulative effect: the longer of the usage time the more obvious of the

effect;

Small current balancing help to reduce the cost and loss;

No additional lines needed, system reliability increased;

c) Statistic Storage Function

The BMS can collect statistics of the maximum voltage, minimum voltage,

maximum temperature, minimum temperature of single cells in each string

and the maximum allowable charge and discharge current of each battery

string;


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The BMS collects charge and discharge capacity of every battery and battery

stack system and calculates the SOC,SOH of battery strings and battery

stacks;

The BMS can record battery stack system events for historical inquiry and

in-depth analysis.

d) Data Uploading and Receiving Control Order Function

BMS can send the voltage, temperature, current, power; working condition, SOC and

SOH information to the monitoring system through communication interface and

receive the orders from monitoring system.

e) Charge and Discharge Management

The BMS monitors the battery status in real time. When the voltage of single cell

exceeds the working voltage range, the BMS will send alarm information to the

controller and notice controller to stop charging or discharging. In extreme cases, for

instance there is big battery fault but controller makes no corresponding action, theBMS will cut off the power line switch automatically to quit charge/discharge.

When the unit is running, if faults such as sampling failure of battery voltage and

temperature, insulation fault of the power circuit to ground and communication fault,

etc. occur, the BMS will notice the controller to stop running to avoid harm.

f) Safety Management

(i) Monitor the voltage and temperature of each single cell to prevent battery

against overcharge, over discharge and over-temperature, thus to insure the

safety of battery usage. According to the monitoring temperature, control the

refrigeration and ventilation devices.

(ii) When battery string needs to be used in parallel, the BSMU will evaluate

whether the strings are ready for parallel or not base on the total string

voltage. If the voltage difference between the battery strings is large, the


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BSMU will not allow the battery string to be paralleled. And if the voltage

difference is small, the parallel can be gradually achieved by precharging the

circuit. The power resistance of pre-circuit can consume the rush current

generated during the parallel to mitigate the damage of rush current to the

high voltage devices and extend the device service life.

(iii) Connect fuses in series in the power circuit. When short-circuit or over-load

situation occurs outside the battery strings, the fuse will protect the battery,

cables and other components in the power circuit.

(iv) Insulation state inspection: when system power circuit leakage (the insulation

grade drop between power circuit and earth), the BSMU can detect fault

information through insulation detection device and request to stop system

operation and prohibit system charge/discharge.

(v) The output side of the battery string power circuit is parted by disconnector.

When maintenance needed, the disconnector can be opened to ensure the

safety and reduce accidents.

(vi) BMS can monitor each switch condition, fuse, temperature and humidity

in first loop to ensure the safety operation.

(vii) BMS can monitor the smog condition, if there is smog from fire, BMS will send

warning information to assort with other devices to act fire fighting.

g) Protection Functions

Under-voltage protection Over-voltage protection

Over-temperature protection

Over-current protection

Temperature abnormal protection

Short-circuit protection

Electricity leakage protection


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CB3 is a polar switch unit which also can be controlled. When the battery is fully

charged, it cannot be charged continually; when the grid power is off, battery will

provide power continually through CB3 with seamless switch.

(3) Step-down silicon chain DW

Adopt 35V-7 automatic step-down silicon chain to stabilize the voltage output to

provide stable DC power to the DC loads.

3.4.3 Communication Topology

The system has the function of local control, it supplies CAN (RS485 or Ethernet)

interface to communicate with the clients control system, and can be remotecontrolled by the clients control system.

Charger

CAN (RS485 or Ethernet)

BMSCAN

DC power supply system

Control SystemProvided by cilent

Fig3.4-14 S ketch map of the battery systems communication topology

3.4.4 Control Strategy

Grid is normal

The power module MK supplies power for the DC bus when grid is normal, and at

the same time, the control system will close the CB2 and CB3, then the charge

circuit is on and the battery is charged by the MK, if the output voltage of the MK

larger than the batterys, the battery will neither be charged nor discharge d.

Grid is abnormal or power off

1) The output voltage of the MK may be too low or fluctuate when grid is

abnormal, if the output voltage of the MK is lower than the batterys, the


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CB3 discharge circuit will be on and the battery system compensates for

the bus bar voltage automatically to make sure that the output voltage is

stable.

2) When grid is power off, the output voltage of the MK is zero, at this time,

the CB3 discharge circuit will be on, and the battery system will supply

power for the load uninterruptedly. During the battery is discharging, the

control system will monitor each cells voltage, and if one of the cell

voltage of the battery string is lower than the discharge cut-off voltage,

the battery system will stop discharging.

State of charge

When grid is workable and the battery system is needed charged according to the

judge of the control system, the control system will send charge order to the lower

computer equipments and the CB3 charge circuit will be on .During the battery

system is charged, the control system will monitor each cells voltage, and if one of

the cell voltage of the battery string is over the charge cut-off voltage, the battery

system will stop charging.

4 System Installation RequirementsThe DC power system should be installed on flat ground and leave enough space

before the tank, behind the tank and up the tank to meet the requirement of

installation, maintenance and cooling. The detailed requirements are as follows:

The installation site should be clean

The ground should be float and the gradient not over 1 degree so that the

tank will not swing.

The installation site should apart from the wall more than 1.5m

The door of the installation room should be over 3m while the width should

be over 2.5m

The altitude of the installation site should not be over 1000m

The temperature of the installation site should be 10 40 and the

relative humidity should be RH10% 75%The bearing load of the installation building is 2 tons/square

byd dc power supply system for substation_20130614

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