Stable electrical grids with a high share of renewable energies www.renewables-made-in-germany.com Prof. Dr.-Ing. Bernd Engel Technische Universität Braunschweig – Germany Institute for High Voltage Technology and Electrical Power Systems – elenia

Lima, October 28th 2014

Outline  Introduction  Fundamentals ancillary services (AS)  Frequency control  Voltage control  Grid restoration  System management  Changes demand and requirements on AS  Summary & outlook

23.10.2014 | Prof. Dr.-Ing. Bernd Engel | Fundamentals of ancillary services | Page 2

Bernd Engel  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)

23.10.2014 | Prof. Dr.-Ing. Bernd Engel | Fundamentals of ancillary services | Page 3

Research focus of the institute elenia Components for electricity transport and distribution ~ = ~

=

Elektromobility

Smart grid 19.09.2014 | Prof. Dr.-Ing. Michael Kurrat | Prof. Dr.-Ing. Bernd Engel | Vorstellung elenia | Seite 4

PVStorage-meter (BMWi) FNN-Study „Statische Spannungshaltung“

PV frequency control (BMWi)

Emil - Elektromobilität mit induktiver Ladung (Schaufenster E-Mobilität)

19.09.2014 | Prof. Dr.-Ing. Michael Kurrat | Prof. Dr.-Ing. Bernd Engel | Vorstellung elenia | Seite 5

Motivation – conventional vs. renewable energies Share in the brutto generation

93,8 %

71,9 %

1991

2013

2035

3,2 %

24,1 %

55-60 %

23.10.2014 | Prof. Dr.-Ing. Bernd Engel | Fundamentals of ancillary services | Page 6

Quellen: Spiegel, dena

Speicher

Storage

MassenMass markt

production

Installierte Installed Leistung

power

Quantity/ Anzahl / structure Struktur generators Erzeuger

Grid Netzausbau development / Netzumbau

SchwungInertia masse  WechselInverter richter

Conservation of the power supply quality

FNN

Sicherung der Versorgungsqualität

Challenges Herausforderungen

Studies konkrete Themen / weiteres Vorgehen

Requirements Anforderungen

VDE Standards TAB Normen

 In FNN grid operators, the industry, scientists and authorities cooperate closely

 By law all VDE standards are mandatory in Germany 16.05.2014

FNN-Fördererkreissitzung 2014

7

German grid structure and integration of renewables  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

TSO

G

G GG

G GG

110 kV

G

10/20 kV

400V

DSO 23.10.2014 | Prof. Dr.-Ing. Bernd Engel | Fundamentals of ancillary services | Page 8

380/220 kV

households

What are ancillary services? 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.“

23.10.2014 | Prof. Dr.-Ing. Bernd Engel | Fundamentals of ancillary services | Page 9

Source: Distribution Code 2007, VDN

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“) 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 10



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) 

Control reserve for frequency control 

Absorbing / releasing energy (in case of over- / under-frequency) by the

f

rotating masses is called instantaneous power reserve

Frequency

(“spinning reserve”) 

Primary control reserve (PCR) is activated directly by a controller at

P

5s

10 s

15 min

1h

the power plant 

Secondary control and minute

∆P

Demand and Supply

reserve, activated by the TSO, are 5s

relieving the PCR 

The national (international) reserve-

10 s

15 min

1h

∆P

Primary and secondary control reserve

market-platform is “regelleistung.net” 5s

10 s

15 min

1h Source: Verstege

23.10.2014 | Prof. Dr.-Ing. Bernd Engel | Fundamentals of ancillary services | Page 12

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

4h

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

Only inside the control area – to achieve the minimum power also

power also across control areas

across control areas

1906 MW (-) and 1992 MW (+) (DE)

2208 MW (-) and 2476 MW (+) (DE)

Current demand

628 MW (+ and -) (DE, CH, NL)

23.10.2014 | Prof. Dr.-Ing. Bernd Engel | Fundamentals of ancillary services | Page 13



  





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 Phase-shifter in the former Nuclear power plant Biblis A

23.10.2014 | Prof. Dr.-Ing. Bernd Engel | Fundamentals of ancillary services | Page 14

Source: echo-online.de

Reactive-Power-Management for voltage control

Reactive-Power-Management for voltage control in the LV grid 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

Netzstation HAS 2

MS-Netz

20 kV

0,4 kV

Leitung

HAS 1

Trafo P

P

P UL1 1,1 p.u. = 253 V

3~

~

P

Last 2

Last 1 High feed-in, low load

PV

1,0 p.u. = 230 V

Länge 0,9 p.u. = 207 V

Max. load

 Voltage Problems were previously associated with costly grid development involving increased amounts of copper, new cables and more powerful transformers. 9

Reactive-Power-Management for voltage control in the LV grid > New grid connection directives: PV plants must make their reactive power available during normal ½ P/Pn

operation

> Grid operator specifies QSet, cosjSet or cosj(P),Q(U) characteristics New LV Grid Code VDE-AR-N 4105

Source: PV plants in the medium-voltage grid BDEW (German Association of Energy and Water Industries), drafted April 2008

>> By supporting the voltage in the inverter, the capacity of the lowvoltage grid can potentially be tripled (source: Federal Ministry for Environment, Nature Conservation and Nuclear Safety project PV-EMS)

> 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

10

Reactive-Power-Management for voltage control in the LV grid > Example: Inductive/underexcited operation of the PV inverter (absorption of reactive power) reduces the voltage boost

PV

Netzstation HAS 2

MS-Netz

20 kV

0,4 kV

Leitung

HAS 1

Trafo

P

P Q UL1

Last 1

P

3~

~

PQ

Last 2

High feed-in, low load

1,1 p.u. = 253 V Like above but with reactive power

PV

1,0 p.u. = 230 V

Länge 0,9 p.u. = 207 V

Max. load

11

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 18



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)

23.10.2014 | Prof. Dr.-Ing. Bernd Engel | Fundamentals of ancillary services | Page 19

Source: fernglasagentur.de

Congestion- and feed-in management

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 70

GW

40

30

Source: Fraunhofer ISE

Power

50

20

10 0

Mo 23.06

Tu 24.06

We 25.06

Th 26.06

Fr 27.06

Sa 28.06

Su 29.06

Example for the feed-in of renewables and conventional power plants in the June of 2014

  

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

23.10.2014 | Prof. Dr.-Ing. Bernd Engel | Fundamentals of ancillary services | Page 20

 

Voltage control





System management/ grid restoration

Frequency control

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

23.10.2014 | Prof. Dr.-Ing. Bernd Engel | Fundamentals of ancillary services | Page 22

In future: the ancillary services have to be provided by „area power plants“ ancillary services

new world: decentral

old world: central

ancillary services

TSO

TSO 380/220 kV

central power plants DSO

„area power plant“

23.10.2014 | Prof. Dr.-Ing. Bernd Engel | Fundamentals of ancillary services | Page 23

DSO 110/20/0,4 kV

The prove since more than 10 years: modular AC connected island grid on Kythnos

> 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

24

Parallel operation of inverters with frequency and voltage droops

> 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

PV diesel hybrid island grids are saving fuel

> 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

26

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

23.10.2014 | Prof. Dr.-Ing. Bernd Engel | Fundamentals of ancillary services | Page 27

Thank you very much for your attention!

Stable electrical grids with a high share of renewable energies Contact: Prof. Dr.-Ing. Bernd Engel TU Braunschweig – elenia Email: [email protected]

www.renewables-made-in-germany.com

23.10.2014 | Prof. Dr.-Ing. Bernd Engel | Fundamentals of ancillary services | Page 29