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www.renewables-made-in-germany.com Lima, October 28th 2014
Stable electrical grids
with a high share of renewable energies
Prof. Dr.-Ing. Bernd Engel
Technische Universität Braunschweig – Germany
Institute for High Voltage Technology and Electrical Power Systems – elenia
23.10.2014 | Prof. Dr.-Ing. Bernd Engel | Fundamentals of ancillary services | Page 2
Introduction
Fundamentals ancillary services (AS)
Frequency control
Voltage control
Grid restoration
System management
Changes demand and requirements on AS
Summary & outlook
Outline
23.10.2014 | Prof. Dr.-Ing. Bernd Engel | Fundamentals of ancillary services | Page 3
Since 2011 Professor at Technical University Braunschweig for components for sustainable energy systems at the elenia institute
Representative of the Board for grid integration at SMA Solar Technology AG
Member of the WG system stability at the Federal Ministery for Economics and Energy (BMWi)
Vice President of the Forum Network technology/Network operation (FNN) in VDE
2003 – 2011 Senior Vice President SMA Technology AG (solar inverter)
1996 – 2003 Site Engineering Director, Alstom Transport (trains)
Bernd Engel
19.09.2014 | Prof. Dr.-Ing. Michael Kurrat | Prof. Dr.-Ing. Bernd Engel | Vorstellung elenia | Seite 4
=
~
=
~
Elektromobility
Research focus of the institute elenia
Smart grid
Components for electricity transport and distribution
19.09.2014 | Prof. Dr.-Ing. Michael Kurrat | Prof. Dr.-Ing. Bernd Engel | Vorstellung elenia | Seite 5
Emil - Elektromobilität mit
induktiver Ladung
(Schaufenster E-Mobilität)
PV frequency control (BMWi)
FNN-Study „Statische
Spannungshaltung“
PV-
Storage-meter
(BMWi)
23.10.2014 | Prof. Dr.-Ing. Bernd Engel | Fundamentals of ancillary services | Page 6
Motivation – conventional vs. renewable energies
Share in the brutto generation
* Braunkohle, Kernenergie, Steinkohle, Erdgas, Mineralölprodukte
** Wind, Wasser, Biomasse, PV, Hausmüll
1991 2013 2035
71,9 % 93,8 %
3,2 % 24,1 % 55-60 %
Quellen: Spiegel, dena
16.05.2014 FNN-Fördererkreissitzung 2014 7
In FNN grid operators, the industry, scientists and authorities cooperate closely
By law all VDE standards are mandatory in Germany
Herausforderungen
konkrete Themen
/ weiteres
Vorgehen
AnforderungenTAB
Normen
Speicher Massen-
markt
Installierte
Leistung
Anzahl /
Struktur
Erzeuger
Netzausbau
/
Netzumbau
Schwung-
masse
Wechsel-
richter
Sicherung der Versorgungsqualität
Herausforderungen
konkrete Themen
/ weiteres
Vorgehen
AnforderungenTAB
NormenHerausforderungen
konkrete Themen
/ weiteres
Vorgehen
AnforderungenTAB
Normen
Speicher Massen-
markt
Installierte
Leistung
Anzahl /
Struktur
Erzeuger
Netzausbau
/
Netzumbau
Schwung-
masse
Wechsel-
richter
Speicher Massen-
markt
Installierte
Leistung
Anzahl /
Struktur
Erzeuger
Netzausbau
/
Netzumbau
Schwung-
masse
Wechsel-
richter
Sicherung der VersorgungsqualitätSicherung der Versorgungsqualität
Storage Mass
production
Installed
power
Quantity/
structure
generators
Grid
development
Inertia
Inverter
Conservation of the power supply quality
Challenges Studies Requirements VDE Standards
FN
N
23.10.2014 | Prof. Dr.-Ing. Bernd Engel | Fundamentals of ancillary services | Page 8
In the past all major power plants were connected to the transport network operated by the TSO
Now wind parks and solar plants are connected to the distribution grid of the DSO
• Solar mainly in the LV grid (70 % out of 36 GW)
• Wind mainly in MV and HV grid (approx. 36 GW)
Paradigm shift: From unidirectional to fluctuating bidirectional power flows
c
German grid structure and integration of renewables
G G G
110 kV
10/20 kV
400 V
households
380/220
kV G
G G G
G
TSO
DSO
23.10.2014 | Prof. Dr.-Ing. Bernd Engel | Fundamentals of ancillary services | Page 9
Besides the mere distribution of active power, other parameters of the electrical
energy supply such as frequency, voltage level and waveform are important
„Ancillary services are strictly necessary for the function of the power
system. These services are provided for the network user by the system
operators in addition to the mere transmission and distribution of
electricity. Thus they define the quality of supply:
frequency control
voltage control
grid restoration
system & operation management.“
What are ancillary services?
Source: Distribution Code 2007, VDN
23.10.2014 | Prof. Dr.-Ing. Bernd Engel | Fundamentals of ancillary services | Page 10
Fundamentals of ancillary services
Control reserve for balancing demand and supply Network-frequency as controlled variable Rotating masses for inertia Control chain: Primary, secondary
and tertiary control reserve Providing by conv. power plants &
deferrable loads Frequency-dependent power
reduction („50,2 Hz“)
Monitoring and supervision in all network levels Congestion- and feed-in management
Prevention of asset overload Coordination of network operation
Network control unit as central controlling tool
Grid restoration after blackout Disconnecting disturbing sources
Formation of island grids Switching measures for successive
restoration of supply Coordinated by central control unit
and provided by power plants with start-up ability
(Storage/Hydro and gas turbine power plants)
Reactive-Power-Management for voltage control
Voltage support in case of short circuit
Phase-shifting operation Compensation systems
(STATCOM, FACTS,…)
23.10.2014 | Prof. Dr.-Ing. Bernd Engel | Fundamentals of ancillary services | Page 12
Control reserve for frequency control
Source: Verstege
Absorbing / releasing energy (in case
of over- / under-frequency) by the
rotating masses is called
instantaneous power reserve
(“spinning reserve”)
Primary control reserve (PCR) is
activated directly by a controller at
the power plant
Secondary control and minute
reserve, activated by the TSO, are
relieving the PCR
The national (international) reserve-
market-platform is
“regelleistung.net”
5 s 10 s 15 min 1 h
5 s 10 s 15 min 1 h
5 s 10 s 15 min 1 h
Frequency
Demand and Supply
Primary and secondarycontrol reserve
f
P
∆P
∆P
23.10.2014 | Prof. Dr.-Ing. Bernd Engel | Fundamentals of ancillary services | Page 13
Prequalification procedure and market conditions
TSO announce demand of control reserve
Prequalified supplier are able to bid on these amount of control reserves
Different market conditions for the three control reserve qualities
Conventional power plants provided so far the control reserve
Market-opening for renewables slowly but surely
Primary control reserve Secondary control reserve Minute reserve
Time slice 24 h for one week Two slices (peak and off-peak) Six slices each 4 h
Minimum Power ±1 MW +5 MW or -5 MW +5 MW or -5 MW
Auction period weekly weekly daily (except Sat., Sun. & on public holiday)
Activation time Full power after 30 s After 30 s reaction measurable, full power after 5 min Announcement 7,5 min before activation, full power after 15 min
Max. duration 15 min 4 h Replaced by intra-day-market
Tech. requirements Automatic (on frequency-change) Automatic, external signal from TSO Automatic, external signal from TSO
Payment Capacity price (€ / MW) Capacity-(€ / MW) and energy-(€ / MWh)price Capacity-(€ / MW) and energy-(€ / MWh)price
Pooling Only inside the control area Only inside the control area – to achieve the minimum
power also across control areas
Only inside the control area – to achieve the minimum power also
across control areas
Current demand 628 MW (+ and -) (DE, CH, NL) 1906 MW (-) and 1992 MW (+) (DE) 2208 MW (-) and 2476 MW (+) (DE)
23.10.2014 | Prof. Dr.-Ing. Bernd Engel | Fundamentals of ancillary services | Page 14
Reactive-Power-Management for voltage control
Capacitive (e.g. Cables) or inductive (e.g. transformers, overhead lines, loads) elements generate reactive power demand
Network assets have to be designed for the additional reactive power transmission
Transmission of reactive power causes active power losses Reactive power should be provided where it is needed
Voltage can be influenced by reactive power (EN 50160 ± 10% of 𝑈𝑁𝑒𝑛𝑛):
capacitive → voltage increase
inductive → voltage decrease
Compensation systems are used by the TSO for voltage control
Static voltage control
Adjustment of the voltage by limited active-power feed-in (P (U))
Dynamic voltage control
Supply of short-circuit power:
For a secure trigger of the protective devices
To limit the voltage drop in case of a fault
Voltage control in the event of a fault Sou
rce:
ech
o-o
nlin
e.d
e
Phase-shifter in the former Nuclear power plant Biblis A
9
Example: PV plant installation: In the low load hours before lunch, a power
flow reversal occurs. Violation of the voltage criterion in accordance with EN 50160
PV
PP P
MS-Netz 20 kV
Trafo
0,4 kV Leitung HAS 1
HAS 2
Last 1Last 2
PV
UL1
Länge
P
3~
~
1,1 p.u. = 253 V
1,0 p.u. = 230 V
High feed-in, low load
Max. load0,9 p.u. = 207 V
Netzstation
Voltage Problems were previously associated with costly grid development involving increased amounts of copper, new cables and more powerful transformers.
Reactive-Power-Management for voltage control in the LV grid
10
Source: PV plants in the medium-voltage grid BDEW (German Association of Energy
and Water Industries), drafted April 2008
> New grid connection directives:
PV plants must make their reactive
power available during normal
operation
> Grid operator specifies QSet, cosjSet or
cosj(P),Q(U) characteristics
> MV guidelines: In the event of a drop in
active power, operate with a power
factor ranging from
cos j = 0.95inductive to 0.95capacitive
> LV directives: In the event of a drop in
active power, operate with a power
factor ranging from
cos j = 0.90inductive to 0.90capacitive
>> By supporting the voltage in the
inverter, the capacity of the low-
voltage grid can potentially be tripled (source: Federal Ministry for Environment, Nature Conservation and
Nuclear Safety project PV-EMS)
New LV Grid Code
VDE-AR-N 4105
½ P/Pn
Reactive-Power-Management for voltage control in the LV grid
11
PV
PP P
20 kV
Trafo
0,4 kV Leitung HAS 1
HAS 2
Last 1Last 2
PV
UL1
Länge
P
3~
~
1,1 p.u. = 253 V
1,0 p.u. = 230 V
High feed-in, low load
Max. load0,9 p.u. = 207 V
Netzstation
Q
Q
Like above but with
reactive power
MS-Netz
> Example: Inductive/underexcited operation of the PV inverter
(absorption of reactive power) reduces the voltage boost
Reactive-Power-Management for voltage control in the LV grid
23.10.2014 | Prof. Dr.-Ing. Bernd Engel | Fundamentals of ancillary services | Page 18
Grid restoration after a black out
The current concept after a blackout provide a grid restoration via the transmission network level
Power plants with start-up ability (Hydro and gas-turbine power plants) build up the supply on the maximum voltage level
Thereby they help other power plant in the island to restart
Several island-network are synchronized to bigger grid system
Than lower network-levels and loads are step by step connected
A complex grid restoration concept via the transmission network level
Frequent trainings of the restoration process with the control center personnel
23.10.2014 | Prof. Dr.-Ing. Bernd Engel | Fundamentals of ancillary services | Page 19
Congestion- and feed-in management
Monitoring the currcent network-status
Continuous monitoring only on the maximum and high voltage
levels, partially on the mid-voltage levels
In the most low-voltage-grids there is no monitoring
Congestion-management for prevention of local asset overloads
E.g. by feed-in-management (renewables), re-dispatch (conv.
power plant) or other action to influence the feed-in
(countertrading)
Securing and providing the other ancillary services
(frequency control, voltage control and grid restoration)
Responsibilities TSO: Organization of the use of the control reserve and reactive power,
congestion management and grid restoration
Responsibilities DSO: local voltage control and grid restoration (supportive for the TSO)
Sourc
e:
fern
gla
sagentu
r.de
23.10.2014 | Prof. Dr.-Ing. Bernd Engel | Fundamentals of ancillary services | Page 20
New power generation structure causes different requirements
Drop out of conventional power plants due to lack of profitably, lower full load hours and the German energy turnaround
Temporary a high amount of renewable energies are feeding in (e.g. 06 of June – 24,2 GW Photovoltaics – 35 % of the load)
Their feed-in could be limited in the future due to the must-run-units and their ancillary services
Providing ancillary services with renewable energies to shut down more must-run-units
E.g.: Ireland’s Island-network with a high amount of wind power, stability problems in some hours
Small Island-networks reach faster their “critical mass” of fluctuating suppliers of energy
Solution in IE: Limitation by a few percent of the feed-in for grid-support with primary reserve
Sour
ce: F
raun
hofe
r ISE
Example for the feed-in of renewables and conventional power plants in the June of 2014
Mo 23.06 Tu 24.06 We 25.06 Th 26.06 Fr 27.06 Sa 28.06 Su 29.06
Power
0
10
20
30
40
50
GW
70
23.10.2014 | Prof. Dr.-Ing. Bernd Engel | Fundamentals of ancillary services | Page 22
Inverter systems are suitable for the provision of ancillary services
Support form the distribution to the transmission network
Frequency stabilization with wind-power (PRC – e.g. Irland) or PV-systems (PRC and “spinning reserve”)
Pooling different renewable sources to a control reserve pool
Active Reactive-Power-Management with inverter system without active power feed-in (Phase-shifter-mode with inverter systems)
New droop control mechanisms (Q(u), P(u))
In case of a blackout, 110kV-networks catch themselves in a island-network (under the support of renewable generators)
Re-dispatch, feed-in- & congestion-management in some hours instead of network expansion
Controlled introduction of smart meters with bagatelle limit
Fre
qu
ency
co
ntr
ol
Vo
lta
ge
con
tro
l
Sy
stem
m
an
ag
em
ent/
g
rid
res
tora
tio
n
23.10.2014 | Prof. Dr.-Ing. Bernd Engel | Fundamentals of ancillary services | Page 23
In future: the ancillary services have to be provided by „area power plants“
old world: central new world: decentral
central
power plants „area power plant“
TSO 380/220 kV
DSO 110/20/0,4 kV
DSO
TSO
ancillary
services
ancillary
services
24
> First modular AC connected
system with Sunny Island
(2001)
> New approach: parallel
operation of battery and
solar inverter
> Solution: ancillary services
provided by the inverters for
frequency and voltage control
The prove since more than 10 years:
modular AC connected island grid on Kythnos
> Adaption of properties of a
synchronous alternator in a power
plant to the battery inverter
> Active power/frequency droop for
the frequency control
> Reactive power/voltage droop for
voltage control
25
Parallel operation of inverters with frequency and voltage droops
PV diesel hybrid island grids are saving fuel
26
> PV diesel hybrid system for the supply of a
chrom mine in Thabazimbi (SFA)
> 1MW PV / 2,1MW diesel-gensets
> expected saving: 450,000 l diesel / year
> start operation 2012
In 2014 follows the wold largest PV diesel hybrid system with Li-Ion battery in Bolivia:
5 MW PV, 2,5 MW battery
Energietechnisches Symposium – Netzsystemdienstleistungen durch Solaranlagen
23.10.2014 | Prof. Dr.-Ing. Bernd Engel | Fundamentals of ancillary services | Page 27
Summary and outlook
Frequency control: - to balance the supply and demand at any moment - today: provided by conventonal power plant (coal, gas, nuclear) - future: integrate renewables for frequency control
Voltage control: - to keep the voltage within their limits (± 10% of 𝑈𝑁𝑒𝑛𝑛) - today: reactive-power-provision on the transmission network level - future: reactive-power-management out of the distribution networks
Grid restoration: - central power plants with start-up-ability build up the transmission network - cellular concept (catch the system on the 110kV-network-level)
System management: - complex system management due to increasing fluctuating feed-in
- suitable processes and tools to control the lower voltage network levels
Future ancillary services will be provided through the distribution grid level
PV with storage system s can already provide ancillary services for large-scale diesel hybrid island grids e.g. for mines in Peru in rural regions with short pay-off times
www.renewables-made-in-germany.com
23.10.2014 | Prof. Dr.-Ing. Bernd Engel | Fundamentals of ancillary services | Page 29
Stable electrical grids
with a high share of renewable energies
Contact: Prof. Dr.-Ing. Bernd Engel
TU Braunschweig – elenia
Email: [email protected]