dc-industrie | april 2018 a concept for a dc grid in ......emc filter in each individual equipment...
TRANSCRIPT
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Verbundvorhaben: DC-Industrie – Intelligentes offenes DC-Netz in der Industrie
für hocheffiziente Systemlösungen mit elektrischen Antrieben
DC-INDUSTRIE |
A concept for a DC grid in
industrial production
April 2018
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Page 2 April 2018
Table of contents
1) Targets and boundaries of an industrial DC grid
2) Concept for load sectors
3) Concept for grounding and EMC
4) Concept for protection
5) Voltage control
6) Conclusions
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Page 3 April 2018
Customer expectations
Requirement DC grid features
Reduced downtime • Very fast disconnection from AC grid faults by semiconductor switch
• Long ride through capability by storage devices and
renewable energy sources
Improved energy efficiency • regenerative braking via the DC link• Reduced conversion losses for storage and renewable
energy
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Page 4 April 2018
Typical devices in an industrial DC grid
=3~
==
==
-+
==
3~=
DC - Bus
=3~
Storage devices (e.g. batteries,
capacitors, flywheels)
Variable speed drives
Passive loads
renewable energy sources
(solar, wind)
Infeed from the AC grid
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Page 5 April 2018
Boundaries of an industrial DC grid
Spatial extension up to one production hall (e.g. 400m)
Indoor (no overhead lines)
Industrial environment (no private homes)
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Page 6 April 2018
Table of contents
1) Targets and boundaries of an industrial DC grid
2) Concept of load sectors
3) Concept for grounding and EMC
4) Concept for protection
5) Voltage control
6) Conclusions
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Page 7 April 2018
Overview of the DC grid
=
3~
=
3~
=
3~
M M M
=
3~
M M M
=3~
=3~
=
=
storage
=
=
generation
3~ Netz
network
management
system
· control
· planning
· simulation
communication
networkM
=3~
3~
=
DC network
LZ1 LZ2 LZ3 LZ4
LZ5LZ6
3~
=
A
V
V
A
V
V
A
V
VA
V
VA
V
VA
V
V
… form a common logical unit
… contain components with strong
functional interconnections
Load sectors…
… are connected to the DC grid via a
DC connection box
… contain sufficient capacitance to
keep transient events inside
themselves
LS1 LS2 LS3 LS4
LS5LS6
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Page 8 April 2018
Connection of the load sectors
Fast current rise
Challenges
Pre-charging of the load sector
Disconnection of the load sector
Optionally: Measurement functions
Features of the DC connection box
Protection of other load sectors and lines
All load sectors feed into a short circuit Selectivity
Switching of DC current
Connection point A
Connection point B
DC connection
box
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Page 9 April 2018
Table of contents
1) Targets and boundaries of an industrial DC grid
2) Concept of load sectors
3) Concept for grounding and EMC
4) Concept for protection
5) Voltage control
6) Conclusions
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Page 10 April 2018
Grounding concept: principles and solutions
Simple solutions (diode rectifier infeed) shall be possible
Fast transients of the DC grid against ground should be prohibited for EMC reasons
All grounding concepts shall require the same creepage and clearance distances
inside the equipment
Principles:
Two dedicated solutions:
a) Low impedance grounding of the star point of the AC grid
b) Capacitive grounding of the DC midpoint
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Page 11 April 2018
Low impedance grounding of the AC grid star point
Infeed will usually be an uncontrolled rectifier
DC voltage to ground is impressed, both DC lines require a protective device.
Grounded secondary side
of the AC transformer
Line
switch
AC
fuseAC side
EMC filter
Infeed (e.g. diode rectifier) DC connection
box
transformer housing filter housing infeed housing
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Page 12 April 2018
Capacitive grounding of the DC midpoint
The DC grid is de facto operated without connection to ground („quasi-IT“), there is only a high ohmic
resistive ( >75kΩ for the complete installation) and capacitive grounding
Stable potential of the DC lines to ground due to EMC capacitors
The AC grid is insulated from ground (insulating transformer)
Only one DC line requires a fast protection device
Operation may continue in case of one DC fault to ground
Insulated secondary side
of the AC transformer
Line
switch
AC
fuseAC side
EMC filter
Infeed (e.g. Active infeed
converter)
DC connection
box
Grounding and
insulation monitoring
transformer housing filter housing infeed housing
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Page 13 April 2018
Overview of EMC ports
EMC filter in each individual
equipment
DC-BUS: Unscreened DC cables / rails
Conducted limits similar to
limits on AC side
AC grid:conducted emission limits
according to the
environment
No long overhead lines to
renewable energy sources
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==
3~=
DC - Bus
=3~
Shielded motor cables
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Page 14 April 2018
EMC concept - requirements
Two basic requirements:
1) All pieces of equipment in the industrial production site must not disturb
each other
2) Radiated emissions must not disturb radio services
Standard requirements for motor cables and AC grid ports are identical to
equipment used in today‘s AC grids
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Page 15 April 2018
EMC concept - solutions
Particular issues for a DC grid:
1) High frequency common mode transients (DC ground) may radiate
grounding concept avoids those
2) High frequency DC current may radiate
minimize area between DC rails
keep high frequency currents inside a load sector (e.g. use shielded
cabinet)
shielding of DC rails is unwanted by customers
First artificial test results are positive
Final validation on test sites
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Page 16 April 2018
Table of contents
1) Targets and boundaries of an industrial DC grid
2) Concept of load sectors
3) Concept for grounding and EMC
4) Concept for protection
5) Voltage control
6) Conclusions
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Page 17 April 2018
Scenario 1: Fault inside a load sector
=
3~
=
3~
=
3~
M M M
=
3~
M M M
=3~
=3~
=
=
storage
=
=
generation
3~ Netz
network
management
system
· control
· planning
· simulation
communication
networkM
=3~
3~
=
DC network
LZ1 LZ2 LZ3 LZ4
LZ5LZ6
3~
=
A
V
V
A
V
V
A
V
VA
V
VA
V
VA
V
V
All equipment in LS 6 is down
DC connection box of LS 6 must open
quickly
LS 1 to 5 continue operation without
interruption
After clearing the fault, the DC
connection box of LS 6 closes and pre-
charges LS6. Equipment in LS 6 starts
operation again.
Equipment inside LS 6 must protect itself
LS1 LS2 LS3 LS4
LS5LS6
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Page 18 April 2018
Scenario 2: Fault on the DC bus
=
3~
=
3~
=
3~
M M M
=
3~
M M M
=3~
=3~
=
=
storage
=
=
generation
3~ Netz
network
management
system
· control
· planning
· simulation
communication
networkM
=3~
3~
=
DC network
LZ1 LZ2 LZ3 LZ4
LZ5LZ6
3~
=
A
V
V
A
V
V
A
V
VA
V
VA
V
VA
V
V
All load sectors feed into the fault
All DC connection boxes open
All equipment is down
After clearing the fault, the DC grid is
powered up again.
No equipment is damaged
LS1 LS2 LS3 LS4
LS5LS6
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Page 19 April 2018
Today‘s ideas for fast protection switches
a) Fully electronic b) Hybrid:
Very fast reaction time (few µs)
High on-state losses
Low on-state losses
Slower reaction time (few hundred µs)
Choke required (careful design of resonances)
T1
T2
A +
A - B -
B +
T1
T2
A +
A - B -
B +
SL
D
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Page 20 April 2018
Table of contents
1) Targets and boundaries of an industrial DC grid
2) Concept of load sectors
3) Concept for grounding and EMC
4) Concept for protection
5) Voltage control
6) Conclusions
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Page 21 April 2018
010
020
030
040
050
060
070
080
090
0
400V
AC
480V
AC
&u
nge
erd
eter
Ste
rnp
un
kt
DC
-Sp
ann
un
g in
Vo
lt
Eige
nsc
hu
tz U
nte
rsp
ann
un
g
Tran
sien
te U
nte
rsp
ann
un
g
Stat
ion
äre
Un
ters
pan
nu
ng
Nen
nb
etri
eb
Stat
ion
äre
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ann
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g
Tran
sien
te Ü
ber
span
nu
ng
Eige
nsc
hu
tz Ü
ber
span
nu
ng
400V
540V
800V
Range of transient over / under voltage
Range of stationary over / under voltage:
Rated operating range:
Voltage ranges
Equipment may be permanently operated in this range
Functionality of equipment may be reduced (e.g. reduced power capability)
Active equipment tries to compensate the voltage deviation
Equipment may lose its function, but has to start operation again without any additional
measures when the voltage comes back into the specified range
Voltage may stay in this range for a limited time only
Equipment switches off permanently
650V: Suitable for 400V active infeed and 480V passive infeed
650V
Manufacturers may define different power ratings for equipment when
operated at different rated voltage
Two possible rated voltages for the DC grid
540V: Suitable for 400V passive infeed
Operation of equipment without restrictions
Protection limits: 400V / 800V
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Page 22 April 2018
Voltage regulation algorithms
a) Uncontrolled operation (basic solution):
No active control of the DC voltage (diode rectifier)
b) Droop control (decentralized voltage control): All active infeeds control their power according to the DC voltage
Non-linear control characteristic
No communication required
d) Central voltage control: Central control unit calculates setpoint values for the power of the infeeds
Fast communication required
The support of one or more algorithms is a feature of the equipment and not defined by the
concept
c) Extended decentralized voltage control: Control characteristic is adapted during operation by a central control unit
Slow communication required
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Page 23 April 2018
Table of contents
1) Targets and boundaries of an industrial DC grid
2) Concept of load sectors
3) Concept for grounding and EMC
4) Concept for protection
5) Voltage control
6) Conclusions
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Page 24 April 2018
Conclusions
The DC grid consists of several independent load sectors
Energy exchange between different loads and sources is very easy
Grounding concepts are fixed and allow to use existing equipment with regard to creepage and
clearance distances
Main challenge is the development of fast and low loss protection devices
Voltage ranges are fixed
The DC grid may be operated with or without a higher-ranking management system for energy control
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Page 25 April 2018
Assoz. Partner: ABB STOTZ-KONTAKT, E-T-A Elektrotechnische Apparate, HARTING, HOMAG Group, Jean Müller GmbH Elektrotechnische Fabrik , U.I. Lapp, LEONI
Special Cables, Phoenix Contact, SEW-Eurodrive, Yaskawa, ZVEI.