stable electrical grids - camara- · pdf filestable electrical grids ... control reserve for...

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 |

Introduction

Fundamentals ancillary services (AS)

Frequency control

Voltage control

Grid restoration

System management

Changes demand and requirements on AS

Summary & outlook

Outline


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)


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


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


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


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


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)


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


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



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


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


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


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


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


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

Thank you very much for your attention!

www.renewables-made-in-germany.com


Stable electrical grids

with a high share of renewable energies

Contact: Prof. Dr.-Ing. Bernd Engel

TU Braunschweig – elenia

Email: [email protected]

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