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Chair of Power ElectronicsChristian-Albrechts-Universitรคt zu KielKaiserstraรe 224143 Kiel
Unlocking the Hidden Capacity of the Electrical Grid through Power Electronics
Prof. Dr. Ing. Marco Liserre
Chair of Power Electronics | Marco Liserre | [email protected] 1
Outline
Unlocking the hidden capacity of the el. grid through power electronics: in the distribution through Smart Transformer in the transmission through HVDC with voltage control
Integrating power electronics into the electrical grid: Grid following operation: impedance detection and correct PLL modelling Grid forming operation: facing weak and low inertia grid challenges
Chair of Power Electronics | Marco Liserre | [email protected] 2
Outline
Unlocking the hidden capacity of the el. grid through power electronics: in the distribution through Smart Transformer in the transmission through HVDC with voltage control
Integrating power electronics into the electrical grid: Grid following operation: impedance detection and correct PLL modelling Grid forming operation: facing weak and low inertia grid challenges
Chair of Power Electronics | Marco Liserre | [email protected] 3
โข Goal: To make electric grids moresustainable and intelligent by means ofpower electronics-based transformer, mostly in view of the mobility electrification.
โข Realization: Investigation and developmentof a highly efficient and reliable Smart Transformer that allows DC connection andoffers grid services, with the goal to defer oravoid grid infrastructure upgrade
โข Project Volume: 2 Mio. โฌ (ERC Grant )
HEART: Excellence Research for electric grids at theChair of Power Electronics
Chair of Power Electronics | Marco Liserre | [email protected] 4
โข Releases capacity within existing LV network for connection of future LCT generation and load prior to costlyreinforcement.
โข Provides distribution network with increased flexibility and adaptability to cope with uncertainties in how energy will begenerated and consumed.
โข Significant reduction in 11kV/LV network reinforcement caused by the uptake of LCTs &electrification of heat & transport sectors.
โข Lay ground works for future LVDC network reducing customer losses (avoided losses of~ยฃ100m annually by 2040 in EV charging)
Financial Savings:
โข ยฃ62m by 2030โข ยฃ528m by 2050โข 16% of GBs 11kV/LV GM subs by 2050
Carbon Savings:
โข 523 kt.CO2 by 2030โข 2,032 kt.CO2 by 2050
LV-Engine Project Overview
Chair of Power Electronics | Marco Liserre | [email protected] 5
The Smart Transformer
Chair of Power Electronics | Marco Liserre | [email protected] 6
Meshed Grid Operation
Meshed 1: at LV ac bus
Meshed 2: the terminal of LV ac feeders
Meshed 3: LV dc and LV ac-1
Meshed 4: LV dc and LV ac-2
Chair of Power Electronics | Marco Liserre | [email protected] 7
ST Achievements in:
b) High DG penetration
c) High load demand
d) Combined High DG and high load demands
Grid Assets update can be deferred, further changes in the production/consumption can be dynamically accommodated with
light infrastructures
Meshed Grid Operation
Chair of Power Electronics | Marco Liserre | [email protected] 8
Frequency variation
Power variation request
G. De Carne, G. Buticchi, M. Liserre and C. Vournas, "Real-Time Primary Frequency Regulation using Load Power Control by Smart Transformers," in IEEE Transactions on Smart Grid, Early Access.
Regulation downwards (+20% load)
HV F
requ
ency
Activ
e pow
erHV
syst
em
ST-based load control:Real Time Frequency Regulation service
Chair of Power Electronics | Marco Liserre | [email protected] 9
Impact on the Irish systemMax Wind penetration
Real Time Frequency Regulation:Irish test case
Chair of Power Electronics | Marco Liserre | [email protected] 10
Outline
Unlocking the hidden capacity of the el. grid through power electronics: in the distribution through Smart Transformer in the transmission through HVDC with voltage control
Integrating power electronics into the electrical grid: Grid following operation: impedance detection and correct PLL modelling Grid forming operation: facing weak and low inertia grid challenges
Chair of Power Electronics | Marco Liserre| [email protected] slide 11
Frequency support provision by HVDC systems
โข Power variation in Area 1 โ10% total load
โข The HVDC can work at constant power
Large frequency variation in Area 1
No frequency variation in Area 2
โข The HVDC can provide frequency support
Reduced frequency drop in Area 1
Area 2 sees a frequency deviation
Area 2 constantpowerArea 2 frequencysupport
Area 1 frequencysupport
Area 1 constantpower
Chair of Power Electronics | Marco Liserre| [email protected] slide 12
1. Terminal 2 identifies load sensitivity (e.g., every15 minutes)
2. Terminal 1 measures a frequency variation
3. Terminal 2 varies the load voltage to extract thesame amount of energy needed to supportfrequency in Area 1
Load voltage
Load power
Area 2 frequencywith LCArea 2 frequencywithout LC
Area 1 frequency
Frequency support provision by HVDC systems
Chair of Power Electronics | Marco Liserre | [email protected] 13
ENSURE: Neue EnergieNetzStruktURen fรผr die Energiewende
โข Goal: Development of solutions for optimal operations of the future German grid in scenarios with high integration of RES.
โข Realization: Holistic, systematic approach foranalyzing new grid topologies and control, andfor integrating new technologies in the supplysystem.
โข Project Volume: 40 Mio. โฌ (Total), 600.000 โฌ (CAU budget)
โข Partner: 23 (Universities, Industries, Gridoperators, Civil Societies)
Chair of Power Electronics | Marco Liserre | [email protected] 14
Outline
Unlocking the hidden capacity of the el. grid through power electronics: in the distribution through Smart Transformer in the transmission through HVDC with voltage control
Integrating power electronics into the electrical grid: Grid following operation: impedance detection and correct PLL modelling Grid forming operation: facing weak and low inertia grid challenges
Chair of Power Electronics | Marco Liserre| [email protected] slide 15
EEMSWEA: Mittelspannungsnetzanalyse
โข Ziel: Analyse der elektrischen Eigenschaften von Mittelspannungs-netzen in Hinsicht auf eine Optimierung bei hoher Einspeisung aus Wind-energieanlagen und Verbesserung der Oberschwingungsbelastung
โข Realisierung: Entwicklung eines mobilen Mess- und Analysesystems zur Einspeisung harmonischer Strรถme und zur Messung der Netzimpedanz
โข Projektvolumen: 3.8 Mio. โฌ2.9 Mio. โฌ (CAU)
Chair of Power Electronics | Marco Liserre| [email protected] slide 16
EEMSWEA-PROJEKTMITTEL SPANNUNGS NETZ ANALYSATOR
NPC 1-4
Control Cabinet 1, 2
Control Cabinet 3
NPC 5,6
Feldmessung in Vollstedt (Nordfriesland)
Messcontainer Netzcharakterisierung
Night: resonance at 1.8 kHz with a magnitude |Zg|= 1.3ฮฉ and capacitive phase angle in a frequency range between 1.6kHz and 4.8kHz;
Day: the magnitude at 1.8 kHz is |Zg|=0.5ฮฉdue to the changing operation of loads and generators by the grid customers.
Public LV grid Northern Germany
Chair of Power Electronics | Marco Liserre| [email protected] slide 17
Resonance Identification
โข By using time-domain data, the transfer function of impedance can be obtained by vector fitting method;
โข The main idea is to use a rational function to approximate poles {am};
N is the approximation order,d and e are optional for the rational function
An example of measured & estimated grid impedance in German grid
Chair of Power Electronics | Marco Liserre| [email protected] slide 18
DFG-Schwerpunktprogramm: Stabilitรคtsbewertung von hybriden Stromnetzen
โข Ziel: Formal evaluation of thestability of hybrid power electronics-based grids
โข Realization: Development ofaccurate model and stabilitycriteria for converter-based grids, considering the impact of the gridsynchronization.
โข Project Volume: 330.000 โฌ (DFG-funded)
โข Partner: EPFL (Lausanne, Switzerland)
HVDC
MV power link
Smart
transformer
Model of theconverter
Chair of Power Electronics | Marco Liserre| [email protected] slide 19
Accurate modeling of the grid synchronization of converters through PLL
PLL-synchronized Power Converter
Z. Zou and M. Liserre, "Study of phase-locked-loop-based synchronization of grid inverter during large phase jump," IEEE Energy Conversion Congress and Exposition (ECCE), Portland, OR, 2018, pp. 1-7.
Chair of Power Electronics | Marco Liserre| [email protected] slide 20
Impact of higher accurate modeling of the PLL in the stability analysis
Instabiles Umrichterverhalten nacheinem Phasensprung Small Signal Model
(1. Order)
Higher accurate model(2. Order)
Stable
Unstable
Chair of Power Electronics | Marco Liserre| [email protected] slide 21
Outline
Unlocking the hidden capacity of the el. grid through power electronics: in the distribution through Smart Transformer in the transmission through HVDC with voltage control
Integrating power electronics into the electrical grid: Grid following operation: impedance detection and correct PLL modelling Grid forming operation: facing weak and low inertia grid challenges
Chair of Power Electronics | Marco Liserre| [email protected] slide 22
Industrial PhD in collaboration with the wind turbine manufacture ENERCON GmbH on thetopic โconverter control strategies for applications in grids with high power-electronics basedgenerationโ
Behaviour of grid-forming converters and conceptual differences compared to state of the artgrid-following units are investigated
Grid-forming operation
Chair of Power Electronics | Marco Liserre| [email protected] slide 23
Results of small-signal stability analysis showthe limitations of grid-following converterscaused by their synchronization units whenoperating under weak grid conditions
A Monte-Carlo based analysis shows that under such operating conditions, not only the stability margin of the converter is decreased, but the interactions between synchronization units of converters operating nearby become stronger
Grid-forming operation
Chair of Power Electronics | Marco Liserre| [email protected] slide 24
Robust stability of grid-forming converters has been investigated by means of ฮผ-analysis
It requires the state-space representation of the control and of the plant, obtained adopting thecomponent connection method (CCM)
The CCM for state-space representation of a complex system
Control C
Plant G Decomposition in separated subsystems with known
state-space representation
๐ด๐ด๐๐ = ๐๐๐๐๐๐๐๐ ๐ด๐ด๐ ๐ ๐ ๐ ๐ ๐ ๐ ,๐ด๐ด๐ ๐ ๐ ๐ ๐ ๐ ๐ , โฆ ,๐ด๐ด๐ ๐ ๐ ๐ ๐ ๐ ๐ ๐ ๐ต๐ต๐๐ = ๐๐๐๐๐๐๐๐ ๐ต๐ต๐ ๐ ๐ ๐ ๐ ๐ ๐ ,๐ต๐ต๐ ๐ ๐ ๐ ๐ ๐ ๐ , โฆ ,๐ต๐ต๐ ๐ ๐ ๐ ๐ ๐ ๐ ๐ ๐ถ๐ถ๐๐ = ๐๐๐๐๐๐๐๐ ๐ถ๐ถ๐ ๐ ๐ ๐ ๐ ๐ ๐ ,๐ถ๐ถ๐ ๐ ๐ ๐ ๐ ๐ ๐ , โฆ ,๐ถ๐ถ๐ ๐ ๐ ๐ ๐ ๐ ๐ ๐ ๐ด๐ด๐๐ = ๐๐๐๐๐๐๐๐ ๐ด๐ด๐ ๐ ๐ ๐ ๐ ๐ ๐ ,๐ด๐ด๐ ๐ ๐ ๐ ๐ ๐ ๐ , โฆ ,๐ด๐ด๐ ๐ ๐ ๐ ๐ ๐ ๐ ๐
Sub. 5
Sub. 4Sub. 1
Sub. 3Sub. 2
Sub. X Interconnection matrices describe the connections between inputs
and outputs of the subsystems
Chair of Power Electronics | Marco Liserre| [email protected] slide 25
The ฮผ-analysis allows the calculation of a stability margin of a controller for a MIMO systemby defining an uncertainty set affecting the plant
Grid-forming operation
Load X
Transformer Y
Converter Z
Plant uncertainties
Uncertainties are included as a freqeuncy-dependent function
Chair of Power Electronics | Marco Liserre| [email protected] slide 26
Robust stability analysis of a LCL filter based synchronverter connected to the grid
Grid-forming operation
Source: R. Rosso, J. Cassoli, G. Buticchi, S. Engelken, and M. Liserre, โRobust stability analysis of LCL filter based synchronverter under different grid conditions,โ IEEE Trans. Power Electron., June 2019.
Effects of parameter variations on robust stability of asynchronverter have been investigated
Following conclusions can be drawn:
Increase of virtual inertia J does not necessarilycorrespond to an increase of the robust stability (ifdamping is not increased accordingly)
Robust stability against the defined set of high frequencyuncertainties is augmented by the presence of highimpedance between the converter and the grid
Chair of Power Electronics | Marco Liserre| [email protected] slide 27
Conclusions
Real-time services offered by Power Electronics: Smart Transformer: avoid or delay network reinforcement HVDC: offer service to the AC network
Integration of Power Electronics into the grid: Grid Following: identify the electric grid impedance and modelling correctly the PLL Grid forming operation may reinforce the system stability