Future challenges for grid integration testing and needs

© 2019 Fraunhofer IWES 1© 2019 Fraunhofer IWES 1© 2020 Fraunhofer IWES 1

Torben Jersch

Future challenges for grid integration testing

and needs for standardization of testing

29.04.2020

2© 2019 Fraunhofer IWES 2© 2019 Fraunhofer IWES 2© 2020 Fraunhofer IWES

Who are we

Grid Integration testing actual developments

Testing at test benches

Actual model requirements according to 61400-27

HVDC blocking

EMT-Models

Outline

Agenda


Department System Validation Mechanical Drive Train

Department System Technology

33 employees + students

Mechanical integration and cooling

Non-torque load application

Control of 10 MW prime mover and inertia-control

MV system and grid emulation

Automation system and data handling

Mechanical, electrical measurement and data handling

Numerous research Projects

Grid Integration Testing at DyNaLabWho

Certification ofelectrical properties

Nacelle testing


Electrical models are required for grid integrations studies

Validation of grid code requirements

Why do we need standardized validation processes

Standard models for embedding them in various simulation tools

Standardized validation process for assuring high quality measures

Unified process will reduce overall costs

Interest of Industries in Grid Integration Testing


WEC System tests in the field

Functional tests of components

Necessary improvements

Reproducibility of test results

Accelerated testing and certification

process

Cost reduction

Grid Integration of Wind Turbines2011-2013 IWES starts thinking about development of novel test methodologies on test

benches

Actual Design and Validation ProcessIdeal Design and Validation Process

Inverter Testing

Subsystem Testing

System Testing

Field Testing

Field System Testing

SW -Hil Testing

Inverter & Components

Electrical Drivetrain

Electrical System (Nacelle)

WEC

Wind Farm

Controller & PLC

Product Requirements

Validated Product Product

RequirementsValidated Product

Engineering Testing

N.A.

N.A.

Field Testing

Model Aggregation

Hil*

Inverter & Components

Minimal-Sys.

Electrical System (Nacelle)

Wind Turbine

Wind farm

Controller & PLC


Use of nowadays validation and certification process

Objective: Obtaining equivalent results on test benches compared to field tests

Electrical system testing on test benches – (IWES concept/spec./development 2013-2015)

Grid Compliant Testing on DyNaLab

LSS M1Gbx.

HSS

Gen.

AC

DC

DC

AC

Aux.

Nacelle

TurbineControlSystem

Switch gear

Conv.

TestbenchHIL

control

Wind, P, Q, Pitch

Torque

M2Trafo

Filter

Feed-forward controlled Voltage 50 HZ impedance control

MV-Grid EmulationEmulation of WEC

wind rotor dynamicEmulation of voltage

behavior

Emulation of realistic field conditions

Focus on FRT testing by design of 44 MVA grid emulator


DyNaLab Test Bench: Nacelle and drive train TestingCommissioned 2015

Developing test benches Together with test

methodology

ACS 6000 3,3kV IGCT-Inverter

2x Drive 5MW @11rpm

Junction-Box(Disconnect/Grounding

& Measurement)

SpecimenIWES DyNaLab(existing)

3x4~

2=2x3~

2=

44MVA18MVA

2x3~

2=

2x3~

2=

13 MVA 13 MVA

9MVATransformer

15 MVATransformer

ESM ESM


Objective: Obtaining equivalent results on test to that of the DyNaLab nacelle test bench

Reduction of through-put times on the test bench

HiL-Grid-CoP – Testing of reduced systems / (relevant WEC E-Systems) - 2016/2017

Grid Compliant Testing on HiL-Grid-CoP

Emulation of wind rotor and drive train

dynamics

Emulation of voltagebehavior

Accelerate the certification process

Creation of broad acceptance for test procedures on test benches

HSS

Gen.

AC

DC

DC

AC

Minimal System

TurbineControlSystem

Conv.

TestbenchHIL

control

Wind, P, Q, Pitch

Torque

Trafo

Filter

M1

Feed-forward controlled Voltage 50 HZ impedance control

MV-Grid Emulation


Advantages of the IEC61400-27

High simulation speed

Fully documented model

Visible open and modular model structure

Verified model structures

High model accuracy

Model user can use the models independently

Limits of the IEC61400-27

Usable bandwidth is recommended to 15 Hz

Range of model validity down to SCR of 3

Advantages / Limits of IEC 61400-27 modelsWEC Models for grid studies

• Increasing usage of renewable energy

• Changing grids to inverter dominated grids

• Classical modelling approaches won’t be valid


Future Grid Integration Requirements – ToDo’sUnsolved challenges due to HPoPEIPS (High Penetration of Power Electric Interfaced Power Sources)

Wind turbines 15 MW +

Windfarm

GridformingControl

Further Cost Reduction

Time-to-Market

RoCoF

EMT-Model requirements

Black-Start

Impedance requirements

Weak-Grid-Conditions

Grid-WEAResonance

Harmonics

Low Total system

intertia


Specific Application of HPoPEIPSNormal Operation of Offshore Wind Farm

Trafo

Conv.

Conv.

Trafo

OWP1

OWP2

Substation

HVDC-Station

33kV

33kV

155kV

155kV

220kV

380kV

DC

AC

DC

AC

SCR 1.1-2.2of holistic wind farm

Possibilities for controller interaction in HPoPEIPS Grids

Different legal entities


Trafo

Trafo

OWP1

OWP2

Substation

HVDC-Station

33kV

33kV

155kV

155kV

220kV380kV

DC

AC

Current Source

Current Source

Current Source

Current Source

Voltage Source

Conv.

Conv.

Specific Application of HPoPEIPSElectrical surrogate model in normal operation

WEC acting as current source

HVDC acting as voltage source

Principle stable operation due to voltage

generation of HVDC


Specific Application of HPoPEIPSElectrical surrogate model in HVDC blocking condition

Trafo

Trafo

OWP1

OWP2

Substation

HVDC-Station

33kV

33kV

155kV

155kV

220kV380kV

DC

AC

Current Source

Current Source

Current Source

Current Source

Rectifier

Conv.

Conv.

HVDC acting as Rectifier source

Not stabilized operation


Measurement of HVDC BlockingCrucial subsequent faults due to HVDC blocking

Source: Erlich, I., et al. "Overvoltage phenomena in offshore

wind farms following blocking of the HVDC converter." 2016

IEEE Power and Energy Society General Meeting (PESGM). IEEE, 2016.

300 ms300 ms

130% Overvoltage

Transformer Saturation

Excitation of System resonances


Modelling challenges:

High system dynamics

Non-linearity e.g. saturation of transformer

Dynamic change of the impedance

No Standards for EMT modelling of WEC or OWP

No Standards for EMT-Model Validation

No Standards for future Control Concepts (e.g. Grid-Forming)

No Standards for dealing with large HPoPEIPS-Grids

EMT-Modelvalidation Why actual models and validation processes are not sufficient


Back2Back inverter testing

8 MVA specimen @ 690 V

High switching inverters - 100 kHz accumulated

Dynamic control of grid impedance (2.5 kHz) for emulation of complex grid behavior

Harmonic injection up to 10 kHz

PQ4Wind Test Bench Focusing EMT-Model and impedance validation also for higher harmonics

AC

DC

DC

AC

Converter System

ConverterController

LV-HF-Grid Emulation

Conv.

WEA-HIL-ControlGenarator Impedance

Filter*

Grid-Impedance & el. Windfarm emulation

LV-HF-Generator Emulation

8 MW 8 MW

4 MW

Available in 2023


Mobile-Grid-CopCertifying large Grid Forming Power Generation Units up to 20 MW

Key points

28 MVA Continuous Power/ 50 MVA (10

Minutes)

20kV/33 kV/66 KV | 1,5 x U_n

45-65 HZ

Harmonic Injection

Impedance Emulation >> Grid Emulation of

High Penetration of Power Electric Interfaced

Power Sources

~=

~=

=~

=~

=~

=~

~=

~=

=~

=~

=~

=~

DC Bus DC Bus

10 kV20 kV30 kV

ORGrid

PCC

Direct Link

Input

Tran

sfor

mer

Conve

rter

Outp

ut

Tran

sform

er

20 kV33 kV66 kV

Coolin

g

Coolin

g

Filter

SG

DUT

SG SG

Auxi

liary

Supply

Available in 2022


Real-time Simulator for Offshore Energy Systems EMT-Model simulation for large Power Systems with 1 us Sample Time

Trafo

Conv.

Conv.

Trafo

OWP1

OWP2

Substation

HVDC-Station

33kV

33kV

155kV

155kV

220kV

380kV

DC

AC

DC

AC

1 GW Total Power


We cooperate with the best players from industry and research in order to tackle challenges concerted and focused.

This approach allows us to handle research projects of any complexity. And to improve our methodological competence further in a systematic manner.

Facing future challenges together


Thanks a lot for your attention!


Federal Republic of Germany

Federal Ministry for Economic Affairs and Energy

Federal Ministry of Education and Research

European Regional Development Fund (ERDF):

Federal State of Bremen

Senator of Civil Engineering, Environment and TransportationSenator of Economy, Labor and PortsSenator of Science, Health and Consumer ProtectionBremerhavener Gesellschaft für Investitionsförderung und Stadtentwicklung mbH

Federal State of Lower Saxony

Free and Hanseatic City of Hamburg

AcknowledgementsFraunhofer IWES is funded by:

Documents

Future challenges for grid integration testing and needs