May 2017, Andreas Falk ANCILLARY SERVICES WITH VRE (VARIABLE RENEWABLE ENERGY): FOCUS PV SMA Solar Technology AG September 2017 1st International Conference on Large-Scale Grid Integration of Renewable Energy in India Andreas Falk, Ancillary services with VRE
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May 2017, Andreas Falk
ANCILLARY SERVICES WITH VRE (VARIABLE RENEWABLE ENERGY): FOCUS PV
SMA Solar Technology AG
September 2017 1st International Conference on Large-Scale Grid Integration of Renewable Energy in India Andreas Falk, Ancillary services with VRE
CONTENT
2
Voltage support
Frequency support
Dynamic voltage control during a voltage dip
Inter area oscillation damping
Summary
September 2017, 1st International Conference on Large-Scale Grid Integration of Renewable Energy in India, Andreas Falk, Ancillary services with VRE
MOTIVATION – PV IS RELEVANT FOR THE SYSTEM
Relevance of PV is increasing:
> Current situation in Germany: 37 GW PV installed base: 40-50% OF THE LOAD is covered
> Present plan for grid development counts with 50-60 GW ( This is rather conservative): ABOVE 80% OF THE LOAD is covered With such a scenario more and more hours with DOMINATING PV supply can be considered
3
In case of PV dominates generation, PV has to generate sufficient ancillary services
Da
tes:
EEX
Tra
nsp
are
nzpl
attf
orm
0
10
20
30
40
50
60
0:00 4:00 8:00 12:00 16:00 20:00 0:00
Po
we
r (G
W)
time
Example (2016) real data
Solar
Wind
Konventionell0
10
20
30
40
50
60
0:00 4:00 8:00 12:00 16:00 20:00 0:00
Po
we
r (G
W)
time
...same day with double the wind and PV power in 2030
Solar 2035
Wind 2035
Konv 2035
Load profile with distributed generation
September 2017, 1st International Conference on Large-Scale Grid Integration of Renewable Energy in India, Andreas Falk, Ancillary services with VRE
DENA-Study „Ancillary services 2030“
CHARACTERIZATION OF ANCILLARY SERVICES
4
High system responsibility requires more system interaction and new operation modes
Local global
Reactive power management
Sec. reserve
Spinning reserve
Black start capability
Zone of influence
aut
ono
mo
us
coo
rdin
ate
d
Sy
ste
m in
tera
ctio
n
Static voltage control
Dynamic voltage control
Power reduction @ high frequency
Prim. reserve
Established functions for grid connected PV
Future functions for grid connected PV
> Basic demand for RENEWABLE SOURCES for ancillary services
> Static voltage support
> Dynamic voltage support
> Frequency support in case of over frequency
> Additional developments in the direction of:
> Control and coordinated operation
> Active power reserve
> Black start
Most important contribution of« 3. GENERATION » PV- Systems
> Aggregated operation of many distributed PV-plants as a tool for VOLTAGE SUPPORT MANAGEMENT
> Provision of ACTIVE POWER RESERVE for frequency support (e.g. with batteries)
September 2017, 1st International Conference on Large-Scale Grid Integration of Renewable Energy in India, Andreas Falk, Ancillary services with VRE
CONTENT
5
Voltage support
Frequency support
Dynamic voltage control during a voltage dip
Inter area oscillation damping
Summary
September 2017, 1st International Conference on Large-Scale Grid Integration of Renewable Energy in India, Andreas Falk, Ancillary services with VRE
REACTIVE POWER MANAGEMENT (WITHOUT AND WITH VRE)
Motivation
> Transmission and distribution grids NEED REACTIVE POWER to fulfil their tasks even with light load
> Reactive power demand of the grid VARIES WITH LOADS. Reactive power flow may change its direction
Status Quo
> POWER STATIONS cover the reactive power in both directions
> VRE sources NEED LAGGING REACTIVE POWER for local voltage support in the distribution grid
Challenge for the future
> Nearly the entire reactive power has to be COVERED FROM VRE.
> VRE sources connected on HV-grid or/ and a large number of COORDINATED VRE SOURCES in LV- and MV-grids must TAKE OVER THE ROLE OF POWER STATIONS
6
Flexible, distributed and coordinated reactive power generation is necessary
So
urc
e:
„FN
N H
inw
eis
Blin
dle
istu
ng
sma
na
ge
me
nt
in V
ert
eilu
ng
sne
tze
n“
Light load without decentralized generation
Heavy load with decentralized generation
September 2017, 1st International Conference on Large-Scale Grid Integration of Renewable Energy in India, Andreas Falk, Ancillary services with VRE
PV CONTRIBUTION TO REACTIVE POWER MANAGEMENT
Challenge
> Utilization of distributed PV plants
Solution
> PV-Systems with extended reactive power capability
> “VPP-Gateway”-Technology
> Connection to control (standard-protocol)
> Aggregation + protocol conversion Open point
> Regulation / Ability to charge the service
7
Base technologies do exist. The regulation framework is missing in some cases.
„VPP-Gateway“
Control center
P
Q
Q at distribution transformer controlled via external set point
Q
September 2017, 1st International Conference on Large-Scale Grid Integration of Renewable Energy in India, Andreas Falk, Ancillary services with VRE
Reactive power capacity at maximum power. A P/Q diagram must be defined within the thrashed lines in the following diagram. Most of the UTILITYs require the operation of the power plant inside the P/Q diagram within 0.95 pu ≤ V < 1.05 pu of the nominal grid voltage.
8
• This may imply the need to oversize the inverters. • E.g. the inverter must be able to supply Q= 0.5 pu and P=0.9
pu even if the voltage is 0.95 pu at S=100% Snom. • Transformers and other electrical components have an
influence on the power factor (reactive power self consumption of the plant)at the connection point, especially if a capacity behavior is required (0.95 pu ≤U < 1 pu), so that the reactive power provided at inverter terminals has to be even higher than 0.5 pu
VOLTAGE SUPPORT CAPABILITY DEPENDS ON AC-VOLTAGE AND SIZING OF THE EQUIPMENT
September 2017, 1st International Conference on Large-Scale Grid Integration of Renewable Energy in India, Andreas Falk, Ancillary services with VRE
VECTOR DIAGRAM
λ =1 (unity power factor) ⇒medium AC voltage required
λ =0,9 (legging) ⇒high AC voltage possible
λ =0,9 (leading) ⇒low AC voltage required
Vgrid
Iinverter
Vinverter Vinverter Vinverter
Vgrid Vgrid
Vgrid inductivity (inside
the PV-plant)
Vgrid resistor (inside the PV-plant)
→ Required Inverter voltage depends a lot on reactive power needs
September 2017, 1st International Conference on Large-Scale Grid Integration of Renewable Energy in India, Andreas Falk, Ancillary services with VRE
10
A preliminary assessment with special tools in order to estimate the obligations of a solar PV plant is necessary during an early stages of project implementation. It determines the number of inverters needed to realize the interconnection requirements for active and reactive power at the POI (Point of interconnection) See such an expertise on the left side
VOLTAGE SUPPORT WITH REACTIVE POWER INJECTION
September 2017, 1st International Conference on Large-Scale Grid Integration of Renewable Energy in India, Andreas Falk, Ancillary services with VRE
CONTENT
11
Voltage support
Frequency support
Dynamic voltage control during a voltage dip
Inter area oscillation damping
Summary
September 2017, 1st International Conference on Large-Scale Grid Integration of Renewable Energy in India, Andreas Falk, Ancillary services with VRE
12
Active Power Limitation on command: Needs communication link to each inverter or every entire PV-plant Reduction of active power depending on grid frequency: • in case of grid failures • in case of power surplus • to avoid grid instabilities
Active power limitation by frequency – Capabilities of the inverter should allow individual adjustment regarding the needs of the utility.
TRADITIONAL FREQUENCY SUPPORT: POWER REDUCTION IN CASE OF OVER FREQUENCY
September 2017, 1st International Conference on Large-Scale Grid Integration of Renewable Energy in India, Andreas Falk, Ancillary services with VRE
UTILITY MAY CEASE POWER PRODUCTION IN CASE OF OVER FREQUENCY
The Grid operator can send for instance a stop command to the plant. The plant stops power injection within a certain time and remains active (stay connected) until the stop signal disappears.
13
The plant is a black box for the operator. Important is the behavior at POI
POI
Actual values
Power Plant Controller
Actuating values
Stop command
Utility
Monitoring Data
HV transformer (optional)
Power Analyzer
Actuating values
Example for plant controller operation
September 2017, 1st International Conference on Large-Scale Grid Integration of Renewable Energy in India, Andreas Falk, Ancillary services with VRE
FREQUENCY SUPPORT IN CASE OF UNDER FREQUENCY
APR (Active Power Reserve) to be activated during under frequency:
• Two Different ways to comply with standards ( Main difference: Availability demand in case an under frequency occur)
14
STORAGE
99.9 % Availability
PV harvest is not reduced
Operates during all irradiation conditions
Other grid management functions (peak shaving, more sophisticated frequency behavior, fast response)
Curtailment
<98% Availability (poor behavior during power gradients e.g. moving clouds)
PV harvest is reduced due to curtailment
Disposable until power drops until a certain level, below this level it is not possible to provide active power reserve
Could be a proper alternative in grids with a lot of single plants operating with active power reserve (statistical balancing)
The agreement with the Utility will determine which one should be used
September 2017, 1st International Conference on Large-Scale Grid Integration of Renewable Energy in India, Andreas Falk, Ancillary services with VRE
ACTIVE POWER RESERVE: PLANT OPERATES BELOW MPP AND INJECTS ADDITIONAL POWER IF NECESSARY
15
POI
Actual values
Power Plant Controller
Actuating values
HV transformer (optional)
Power Analyzer
Actuating values
Irradiation sensors
Irradiation sensors
SMA Calibration algorithm
September 2017, 1st International Conference on Large-Scale Grid Integration of Renewable Energy in India, Andreas Falk, Ancillary services with VRE
16
Probabilistic forecast for different reliabilities in Germany
PROBABILISTIC FORECAST FOR A SINGLE PLANT
Example power feed-in and minute reserve potential for the verification method “fixed generation schedule” for overall Germany See also: Providing Control Reserve with PV Systems- Goal and Results of the Project PV-Regel, Daniel Premm,…,International ETG Congress 2015, November 17-18, Bonn, Germany
AS lower the requirements regarding probabilistic forecast are and as higher the no. of distributed plants been involved is, as lower are the losses for active power reserve provision.
September 2017, 1st International Conference on Large-Scale Grid Integration of Renewable Energy in India, Andreas Falk, Ancillary services with VRE
CURTAILMENT AND THE USE OF SENSORS
An alternative to storage is the operation of the plant with certain Active Power Reserve (operating the inverters at a lower power output than they could)
In order to calculate the potential available power from the PV plant, it is required to use irradiation sensors throughout the plant.
A special algorithm calibrates the sensors with the present power of the inverters. This results in very good accuracy. The Power Plant Controller will receive the information from the sensors and send the commands to the inverters to run at a different set point below MPP.
According to the IEC 61724-1 standard, the PV system performance can be measured with enough accuracy as long as there is a minimum number of irradiation sensors:
17 September 2017, 1st International Conference on Large-Scale Grid Integration of Renewable Energy in India, Andreas Falk, Ancillary services with VRE
LARGE-SCALE STORAGE INTEGRATION AS AN ALTERNATIVE FOR APR
SUPPORTS THE GROWTH OF RENEWABLE ENERGIES
Frequency support can be implemented very easily while using a battery. Support in both direction possible.
In this application the storage system complement the PV power plant to fulfill requirements that cannot naturally fulfilled with the renewable source alone
Storage provides renewable energy with the same grid-stabilizing characteristics of conventional power plants through the comprehensive provision of ancillary services
September 2017, 1st International Conference on Large-Scale Grid Integration of Renewable Energy in India, Andreas Falk, Ancillary services with VRE 18
RAMP RATE CONTROL WITH BATTERY SUPPORT
19
Which features to be fulfiled by Storage System?
Fulfillment of Regulations and Grid Requirements1
Ramp-Rate Control of PV Plants: Batteries provide reserve power to “firm” the output of the PV system and ensure stable power supply. Makes PV power “dispatchable”
Frequency Control/Regulation: Batteries provide/absorb power to support frequency in the grid
provides reserve power without running fossil generators
2 2.5 3 3.5 4 4.5 5 5.5 6 6.5 7
x 104
-0.5
0
0.5
1
2 2.5 3 3.5 4 4.5 5 5.5 6 6.5 7
x 104
0
0.2
0.4
0.6
0.8
1
PPV
PStrg
Target Value
Target Value
PCombined
SoC
1Day Profile for gradients of 1%Pn/min Requirements
May 2017, Andreas Falk, Inverter Topologies
LARGE-SCALE STORAGE INTEGRATION SUPPORTS THE GROWTH OF RENEWABLE ENERGIES
20
Conventional Power Plants
Various Loads
Power Grid
Ancillary Services
• Scheduling & Dispatch • Reactive Power supply
Renewable Power Plants
Renewable Integration • Ramp-Rate Control • Frequency Control P(f) • Peak shifting and shaving
Weak grid
Industrial Hybrid (Off-Grid or grid-connected) • All grid applications • Optimized Operation of Genset • Energy shifting
Large Commercial Loads
Ancillary Services
• Frequency control P(f)
September 2017, 1st International Conference on Large-Scale Grid Integration of Renewable Energy in India, Andreas Falk, Ancillary services with VRE
CONTENT
21
Voltage support
Frequency support
Dynamic voltage control during a voltage dip
Inter area oscillation damping
Summary
September 2017, 1st International Conference on Large-Scale Grid Integration of Renewable Energy in India, Andreas Falk, Ancillary services with VRE
DYNAMIC VOLTAGE CONTROL MEANS THE RESPONSE OF THE POWER PLANT DURING A VOLTAGE DIP
The power plant must remain connected to the grid and operate normally throughout the zone A in the following figure:
22
1.0
0.0 segt
puV
Zona A
Zona B
Zona B
0.9
1.1
PB1 PB2
PB3 PB4
PA1 PA2
PA3
PB5
1.0
0.0 segt
puV
Zona A
Zona B
Zona B
PB1 PB2
PB3 PB4
PB6
PA1 PA2
PA3
0.9
1.1
PB5
• Type B, C • Type D
In zone B stop of operation is allowed (example for Mexican grid regulations)
September 2017, 1st International Conference on Large-Scale Grid Integration of Renewable Energy in India, Andreas Falk, Ancillary services with VRE
DYNAMIC VOLTAGE CONTROL MEANS THE RESPONSE OF THE POWER PLANT DURING A VOLTAGE DIP
23
Inverter Protection >140% for 1 ms = trip
Voltage Ride Through (LVRT/HVRT) Voltage ride through in the Sunny Central is wider than the requirements. Behavior can be adjusted as per the local requirements
September 2017, 1st International Conference on Large-Scale Grid Integration of Renewable Energy in India, Andreas Falk, Ancillary services with VRE
BEHAVIOR DURING A THREE PHASE VOLTAGE DIP
Imax I32 (I21)
d 33,3 -11,9 11,7 41,7 -45,5 31,1 81,7 -83,3 55,0
3ph fault to 25%Un @ 2.27 MW, 50 °C, 3300A set point, 400 ms voltage dip
September 2017, 1st International Conference on Large-Scale Grid Integration of Renewable Energy in India, Andreas Falk, Ancillary services with VRE
CONTENT
25
Voltage support
Frequency support
Dynamic voltage control during a voltage dip
Inter area oscillation damping
Summary
September 2017, 1st International Conference on Large-Scale Grid Integration of Renewable Energy in India, Andreas Falk, Ancillary services with VRE
WHAT IS INTER AREA OSCILLATION?
Amplitude of the voltage in high voltage grid can vary with +/ - 10% and a frequency between 0.2 until 2 Hz
What to do? Injection of reactive power to damp the voltage oscillation (inter area oscillation damping) See also: A Contribution to Thorough Comprehension of POD Provided by FACTS Devices, Thomas Graber,…; University of Erlangen-Nürberg, Germany, International ETG Congress 2015, November 17-18, 2015, Bonn, Germany
September 2017, 1st International Conference on Large-Scale Grid Integration of Renewable Energy in India, Andreas Falk, Ancillary services with VRE
REQUIREMENTS FOR INTER AREA OSCILLATION DAMPING
Optimal placement: Distributed sources are in favor to solve such problems, because they may available at all places in the future
Reaction time: Dead time of the plant controller must be small enough to react ⇒ Dynamic sensors and communication means in the power plant
September 2017, 1st International Conference on Large-Scale Grid Integration of Renewable Energy in India, Andreas Falk, Ancillary services with VRE
CONTENT
28
Voltage support
Frequency support
Dynamic voltage control during a voltage dip
Inter area oscillation damping
Summary
September 2017, 1st International Conference on Large-Scale Grid Integration of Renewable Energy in India, Andreas Falk, Ancillary services with VRE
SUMMARY
Large PV-power plants can deliver all ancillary services to operate the grids: • Voltage support (with reactive power) • Frequency support (with active power reduction or active power reserve) • Dynamic voltage support • Inter area oscillation damping
Future services: • Spinning reserve. • Black start capability ⇒Both features can be achieved with batteries more favorable