[email protected] A NEW DC BUS POWER SYSTEM

Oct.26-28, 2011, Thailand
www.cigre-aorc.com
PL-21
CIGRE-AORC 2011
A NEW DC BUS POWER SYSTEM BASED ON DC MICROGRID
Wenbo Chen
Golden Cooperate Information&Automation Technology CO.,LTD.
China
SUMMARY
This paper describes the DC-BUS system,It is based on the DC-DC conversion
technology of microgrid, but also a smart distribution system of smart grid, to provide users
with a more stable and reliable, high quality, economical, flexible and interactive, friendly
open power supply method. It can achieve a two-way interaction between users and the grid.
According to users needs and TOU price, the system can choose the right time to use the
clean energy power. It can increase the economic and security for user using the power. It can
more easily put distributed energy power into micro-grid, in order to achieve efficient use of
clean energy and get some economic benefits.
DC-BUS system consists of two-way converter of grid, wind and solar access to DC
conversion system, energy storage system and converter, various voltage levels of DC power
distribution station, these devices are controlled through a same voltage standard and docking
on the DC bus, and according to power generation, matching of power using to realize the
controllable of micro-grid to achieve several different operating modes, and they can
alternate each other. Compare with traditional AC distribution grid, power quality of DC
microgrid are more reliable, much easier to connect to the grid. Exchange of the distribution
grid can solve some difficult problems of AC microgrid. It ’s suitable especially for some of
the important load such as LED lighting, DC/AC speed control system, field instruments,
DCS control systems, computers, network equipment and so on.
It can be mainly used in these places: distributed storage electricity power station,
intelligent power distribution system in factory, wind power station, PV station, short-term
use large capacity load distribution, etc. DC-BUS system achieves a function with clean,
high quality, efficient, safe, self-healing, economic power.
KEYWORDS
DC-DC conversion; microgrid; clean energy power ，liquid flow batteries，lead-acid
batteries，boost，central management system
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I. INTRODUCTION
With the gradual exhaustion of conventional energy and the increasing of environmental
pollution, all the world are focusing on distributed generation, an environmental, efficient and
flexible power generation. As one of the most effective way to use distributed power,
distributed generation system makes good use of various forms of energy.
Microgrid, one of the important forms of distributed generation, refers to a mini-grid
consist of small power generation unit (i.e. distributed power) of one region , which supply
cooling, heat or electricity for local load, and can be in parallel with the traditional power
grid. Microgrid can either operate in parallel with the large-scale power grid when it is
connected to large grid, or supply power for the local load independently. As a result, it is
more reliable for the load side. Besides, the effect on the traditional grid is much smaller
when we connect the microgrid to large grid by one node than that of a large number of small
distributed power. When different series of small power(i.e. distributed power) are combined
together in the micro-grid, they all achieve higher efficiency. Power electronic devices inside
the DC microgrid convert the power and provide necessary control for the system.
DC microgrid performs as a single controlled unit to the external power grid.
II.DC-BUS System
Intelligent DC microgrid refers to a system which combines small distributed power
together to supply cooling, heat and electricity for users along with the low voltage
distribution grid system. The DC-BUS system uses MW-level storage unit and gives priority
to the adoption of new energy supply. (Fig 1)
Fig 1 Intelligent DC microgrid diagram
A. System Components
The DC-BUS system consists of photovoltaic plant, wind power plant, MWlevel storage unit, commercial power charging equipment, low voltage DC-DC substation for
control and lighting system (Fig2), high voltage DC-DC substation for VFD system (Fig 3)
and central management system. Photovoltaic devices include solar modules, a management
system, a convergence boost module, while wind power plant consists of fans, a management
system, a rectifier boost module etc. MW-level storage unit is made up of liquid flow
batteries or lead-acid batteries (Fig 4). The access system is almost the same with the original
one for the commercial power equipment. The low voltage DC-DC substation for control
and lighting system, includes a DC transformer module, a management system and a
distribution system. The high voltage DC-DC substation for VFD system, includes a high
voltage DC transformer module, a management system, a high voltage power distribution
system and a frequency converter. In addition, the central management system (Fig 5)
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1
includes computers, a management system and a communication management system, which
monitors the new energy power generation in real time and realize seamless switching
between new energy and the large grid and so on. Other functions of the central management
system include monitoring each subsystem, intelligent self-test to ensure the system safe and
reliable, intelligent manage of all types of power supply according to the tariffs at peak time,
monitoring of all kind of failure, monitoring the capacity of storage units, temperature and so
on.
Fig 2 low voltage DC-DC substation
Fig 3 high voltage DC-DC substation
Fig 4 battaries
Fig 5
the central management system
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2
B. Function and Working Condition
New energy supply is the first choice in DC-BUS system. When the new energy plants
work in the best state, part of the energy is delivered to the local load, and the other is
provided for the energy storage system. When the new energy power is inadequate
or interrupted in case, commercial electricity works as a supplement or the second choice.
(Fig 6)When neither the new energy nor the commercial electricity works well, high-voltage
DC power distribution subsystem executes unit action, so that storage unit (i.e.
battery) power can be released in order to protect the load of non-stop operation. Local load
will be automatically switched to the new energy power if solar power turned well when the
power is supplied by the storage or commercial electricity. Peak shift could be achieved by
adjusting the power supply time of the storage unit with the central management system
when the battery capacity is large enough. (Fig7)
Fig 6 Peak shift
Fig 7 New energy supply
C. The Advantages of DC-BUS
The advantages of DC-BUS are mainly as follows
1. Green new energy is fully utilized in this system.
2. The power supply for the user is more stable, for instance, the load will not stop working
even when commercial electricity fail to work.
3. The power quality is improved than AC power syetem thanks to DC-DC power system
4. Peak shift could be achieved so that the investment on large grid could be reduced and the
users can enjoy cheaper power supply.
5. Bidirectional reversible charging technology between the DC micro-grid and large grid is
allowed, so that the extra power of the micro-grid could be delivered to the large grid.
6. The power output will be more stable and the impact of loads on large grid will be reduced.
D. Application Areas
The DC-BUS system is especially useful for the following conditions:
1. Used to achieve peak shifting with distributed energy storage.
2. Electric car charging stations --- the pollution and pressure on the grid is reduced.
3. Intelligent distribution system for enterprise, including new energy access, peak shifting,
reducing large grid dependence, micro-grid operation, self-healing ability.
4. Grid-connected wind power plant, solar power plant--- for more stable output and less
impact on the large grid.
5. Short-term use of large capacity load distribution---to reduce the line transformer capacity.
E. The Protection
The protections of the whole system are as follows
• Output overvoltage protection. Overvoltage protection circuit is built in high-frequency
module, so that when overvoltage happens the circuit will lock automatically and the fault
module will be out of work, not affecting the whole system.( Fig 8)
• Output current limit protection. The output power of each module is limited and the output
current cannot be infinitely increased, so that each module output current is limited
to maximum rated output current. The module will automatically reduce the output voltage to
protect itself if overloaded.
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3
• Module parallel protection. Each module has a protection circuit in parallel to ensure that the
fault module will automatically exit the system without affecting other normal modules.
• Overcurrent protection. The power devices will be powered off to be protected if the
current exceeds their withstand current in each cycle of the converter.
• Output under voltage protection. The module will alarm automatically when the output
voltage is too low.
• Over-temperature protection. Over-temperature protection mainly refers to high-power
converters, which have a junction temperature and current overload safety limits. In some
special circumstances, such as high ambient temperature, the devices will be shut down to be
protected when the module detects heat sink temperature exceeding the set value , and started
when the temperature drop to normal range.
C
C
C
C
C
C
Fig 8 voltage/current
III.CONCLUSIONS
The DC-BUS system, a DC microgrid system, is an intelligent distribution system at the
terminal of large grid, which supplies more stable, reliable, quality, cheap, flexible and
friendly electricity for users. Consumers are able to interact with large grid more conveniently
with this system, choosing suitable time to give priority to clean energy according to the
consumer’s requirement and the tariffs at peak time, thus cutting down the expense and
improving the safety. When DC-BUS system works well, the load is powered by the solar
power, while the commercial electricity works as a supplementary. When neither the new
energy nor the commercial electricity works well, the storage unit (i.e. battery) power can be released
in order to protect the load of non-stop operation. Local load will be automatically switched to the
new energy power if solar power turned well when the load is powered by the storage or commercial
electricity. Compared with traditional AC distribution network, the DC microgrid has the
advantages of more reliable power quality and easier networking. It is suitable especially for
some important load in the factory such as LED, VFD drive systems, DCS control systems,
computers and network devices.
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4
BIBLIOGRAPHY
[1]
[2]
[3]
[4]
[5]
[6]
Design and research on protection and control of smart distribution grid.(Proceedings of the
CSEE,Vol.29,NO.supported,pp.1-6,Dec.2009)
Smart grid and its implementations.(Proceedings of CSEE,Vol.29,NO.34,pp.1-8,Dec.2009)
Generation control circuit for photovoltaic modules.(IEEE Transactions on Power
Electronics,2001,16(3):293-300)
Real-world MicroGrids-an overview[C].(IEEE International conference on System of Systems
Engineering,USA,2007:Z535-Z542)
Distributed generation:definition,benefits aissues[J].(Energy Policy,2005,33(6):787-798)
Renewable energy scenario to 2040:half of the global energy supply from renewables in
2040[R].May 2004.
Short Bio-data of Main Author
Wenbo Chen is the General Manager of COOPERATE INFORMATION&AUTOMATION
TECHNOLOGY CO.,LTD.He is committed to the research on power quality management. And he is
the major member in the research on a series productions such as SGS furnace safety systems , DCBANK system ,power ride-through module and so on.Besides he has delivered many articles about
management of voltage dip. He also has the security of the power chamber with SGS and RTC101
which is a practical electronic switch.
Xuezhong Zhu is the graduate tutor of Nanjing University of aeronautics and
astronautics.
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5
PL-21
A NEW DC BUS POWER SYSTEM
BASED ON DC MICROGRID
Green Your
Wenbo Chen
Golden Cooperate
Information&Automation Technology
CO.,LTD
China
Life
Microgrid, one of the important forms of distributed generation, refers
to a mini-grid consist of small power generation unit (i.e. distributed
power) of one region , which supply cooling, heat or electricity for
local load, and can be in parallel with the traditional power grid.
Microgrid can either operate in parallel with the large-scale power
grid when it is connected to large grid, or supply power for the local
load independently. As a result, it is more reliable for the load side.
Besides, the effect on the traditional grid is much smaller when we
connect the microgrid to large grid by one node than that of a large
number of small distributed power. When different series of small
power(i.e. distributed power) are combined together in the micro-grid,
they all achieve higher efficiency. Power electronic devices inside the
microgrid convert the power and provide necessary control for the
system. Microgrid performs as a single controlled unit to
the external power grid.
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AC MICROGRID
Cool/ heat
冷热电联供
pv
Access of
microgrid
太阳能
Central
managem
ent
system
battaries
Cool/heat
冷热电联供
储能
装置
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Wind
plant
DC MICROGRID
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• Intelligent DC microgrid refers to a system
which combines small distributed power
together to supply electricity for users
along with the low voltage distribution grid
system.
• The DC-BUS system uses MWlevel storage unit and gives priority to the
adoption of new energy supply.
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DC-BUS POWER SYSTEM
PV
large grid
发电量
DAY NIGHT
WIND
access
~
BTM (MPPT)
=
‥
‥
=
=
=
~
时间
6:00
18:00
6:00
工业配电
‥
‥
‥
=
RTM
RTM
=
=
RTM
=
DC540V
AC 380V
厂内各负载
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battaries
MWh
=
RTM
=
DC400V
=
=
DC540V
DC-BANK
UPS
EPS
···
重要负载
重要负载
重要负载
···
Function and Working Condition
• New energy supply is the first choice in
DC-BUS system. When the new energy
plants work in the best state, part of the
energy is delivered to the local load, and
the other is provided for the energy
storage system.
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Function and Working Condition
• When the new energy power is inadequate or interrupted
in case, commercial electricity works as a supplement or
the second choice. (Fig 6)When neither the new
energy nor the commercial electricity works well, highvoltage DC power distribution subsystem executes unit
action, so that storage unit (i.e. battery) power can be
released in order to protect the load of non-stop
operation. Local load will be automatically switched to
the new energy power if solar power turned well when
the power is supplied by the storage or commercial
electricity.
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Function and Working Condition
• Peak shift could be achieved by adjusting the
power supply time of the storage unit with the
central management system when the
battery capacity is large enough.
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parallelpower
with the
power
grid
supply
for large-scale
the local load
independently
LARGE GRID
~
ACCESS
~
~
=
WIND
=
BTM (MPPT)
=
‥ ‥
‥ ‥
‥
=
DISTRIBUTION
PV
RTM
=
厂内各负载
DC540V
AC 380V
BATTRIES
MWh
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RTM
=
=
DC540V
RTM
=
=
RTM
=
DC400V
=
=
DC540V
DC-BANK
UPS
EPS
···
IMPORTA
NT LOAD
IMPORTA
NT LOAD
IMPORTA
NT LOAD
···
System Components
The DC-BUS system consists of
• photovoltaic plant,
• wind power plant,
• MW-level storage battaries unit,
•
commercial power charging equipment,
• low voltage DC-DC substation for control and
lighting system ,
• high voltage DC-DC substation for VFD motor
system
• central management system.
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System Components
• Photovoltaic devices include solar module
s, a management system, a
convergence boost module (RTM)
• wind power plant consists of fans, a
management system, a rectifier boost
module (RTM) etc.
• MW-level storage unit is made up of liquid
flow batteries or lead-acid batteries
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System Components
• The access system is almost the same with the
original one for the commercial power
equipment.
• The low voltage DC-DC substation for control
and lighting system, includes a DC transformer
module, a management system and a
distribution system.
• The high voltage DC-DC substation for VFD
system, includes a high voltage DC transformer
module, a management system, a high voltage
power distribution system and a frequency
converter.
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System Components
• the central management system includes computers, a
management system and a communication management
system, which monitors the new energy power
generation in real time and realize seamless switching
between new energy and the large grid and so on. Other
functions of the central management system include
monitoring each subsystem, intelligent self-test to ensure
the system safe and reliable, intelligent manage of all
types of power supply according to the tariffs at peak
time, monitoring of all kind of failure, monitoring the
capacity of storage units, temperature and so on.
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ZBB flow batteries
New energy supply
lead-acid batteries
Only back-up
battaries
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low voltage DC-DC substation
SUPPLY TO LED,DCS control systems, computers and network devices.
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high voltage DC-DC substation
Supply to the VFD motor systems,
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DC-BUS supply to the VFD motor
~
=
MAN
AGE
MENT
=
MAN
AGE
MENT
=
=
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~
~
=
=
DC-BUS
~
=
~
=
VFD
BATT
ARIE
S
MAN
AGE
MENT
~
~
=
=
=
=
=
=
~
M
~
M
~
M
the central management system
• EASY CONTROL
• Adjusting the input and output voltage of
the DC-DC transformer module chooses
that the new energy supply is the first
choice
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the central management system
•
The Protection
•
•
•
The protections of the whole system are as follows
• Output overvoltage protection.
Overvoltage protection circuit is built in high-frequency
module, so that when overvoltage happens the circuit
will lock automatically and the fault module will be out
of work, not affecting the whole system.( Fig 8)
• Output current limit protection.
The output power of each module is limited and the
output current cannot be infinitely increased, so that
each module output current is limited
to maximum rated output current. The module will
automatically reduce the output voltage to protect itself
if overloaded.
•
•
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the central management system
• The Protection
• • Module parallel protection.
• Each module has a protection circuit in parallel to
ensure that the fault module will automatically exit the
system without affecting other normal modules.
• • Overcurrent protection.
• The power devices will be powered off to be protected
if the current exceeds their withstand current in
each cycle of the converter.
• • Output under voltage protection.
• The module will alarm automatically when the output
voltage is too low.
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the central management system
• The Protection
• • Over-temperature protection.
• Over-temperature protection mainly refers
to high-power converters, which have a junction
temperature and current overload safety limits.
In some special circumstances, such as
high ambient temperature, the devices will be
shut down to be protected when the module
detects heat sink temperature exceeding the set
value , and started when the temperature drop
to normal range.
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the central management system
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Alarm and events
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The real time data of power
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The history data
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Print the real time data of new energy
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1minite data
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1minite data of PV
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THE REAL TIME DATA OF BATTARIES
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THE REAL TIME DATA OF BATTARIES
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DC-DC TRANSFORMER MODULE DATA
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KWh data
实时趋势曲线查看发
电量实时数据信息
历史趋势曲线查看发
电量历史数据信息
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WEB broadcast
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The Advantages of DC-BUS
•
•
•
•
•
1. Green new energy is fully utilized in this system.
2. The power supply for the user is more stable, for
instance, the load will not stop working even when
commercial electricity fail to work.
3. The power quality is improved than AC power
syetem thanks to DC-DC power system
4. Peak shift could be achieved so that the investment
on large grid could be reduced and the users can
enjoy cheaper power supply.
5. Bidirectional reversible charging technology
between the DC micro-grid and large grid is allowed,
so that the extra power of the DC-BUS system could
be delivered to the large grid.
6. The power output will be more stable and the impact
of loads on large grid will be reduced.
Green Your Life
Application Areas
•
•
•
•
•
•
The DC-BUS system is especially useful for the
following conditions:
1. Used to achieve peak shifting with
distributed energy storage.
2. Electric car charging stations --- the pollution and
pressure on the grid is reduced.
3. Intelligent distribution system for enterprise building,
including new energy access, peak shifting, reducing
large grid dependence, micro-grid operation, selfhealing ability.
4. Grid-connected wind power plant, solar power plant-- for more stable output and less impact on the large
grid.
5. Short-term use of large capacity load distribution--to reduce the line transformer capacity.
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design for the airplane and train
station
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design for the airplane and train
station
• Power supply :
• PV on the building
• Lift VFD motor
• Large Grid
• lead-acid batteries
• Load:
• Colling water VFD motor
• Lighting and computer control system
• Lift VFD motor
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CASE FOR A MICRO-ELECTRONICS FAB
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•
•
•
•
•
•
•
Power supply :
PV on the building
Large Grid
lead-acid batteries
Load:
PE/PCW/PPCW/ VFD motor
Lighting and computer control system
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CENTRAL MANAGEMENT SYSTEM
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high voltage DC-DC substation
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THE DATA OF NON-STOP OPERATION
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• The DC-BUS system, a DC microgrid system, is an intelligent
distribution system at the terminal of large grid, which supplies more
stable, reliable, quality, cheap, flexible and friendly electricity for
users. Consumers are able to interact with large grid more
conveniently with this system, choosing suitable time to give priority
to clean energy according to the consumer’s requirement and the
tariffs at peak time, thus cutting down the expense and improving
the safety. When DC-BUS system works well, the
load is powered by the solar power, while the commercial
electricity works as a supplementary. When neither the new
energy nor the commercial electricity works well, the storage unit (i.e.
battery) power can be released in order to protect the load of nonstop operation. Local load will be automatically switched to the
new energy power if solar power turned well when the load is
powered by the storage or commercial electricity. Compared with
traditional AC distribution network, the DC microgrid has the
advantages of more reliable power quality and easier networking. It
is suitable especially for some important load in the factory such as
LED, VFD drive systems, DCS control systems, computers and
network devices.
Green Your Life
• Wenbo Chen is the General Manager of COOPERATE
INFORMATION&AUTOMATION TECHNOLOGY
CO.,LTD.He is committed to the research on power
quality management. And he is the major member in the
research on a series productions such as SGS furnace
safety systems , DC-BANK system ,power ride-through
module and so on.Besides he has delivered many
articles about management of voltage dip. He also has
the security of the power chamber with SGS and
RTC101 which is a practical electronic switch.
• Xuezhong Zhu is the graduate tutor of Nanjing
University of aeronautics and astronautics.
Green Your Life
• THANK YOU VERY MUCH AND HOPE
HAVE A GOLDEN COOPERATION WITH
YOU!
• WWW.GC-BANK.COM
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