Synthetic inertia from wind generation – power electronic … · 2019-05-02 · DFIG and network...

Infrastructure Access Report

Infrastructure: SINTEF Renewable Energy Lab - SmartGrids

User-Project: SYNERTIA

Synthetic inertia from wind generation – power electronic converter capabilities

Olimpo Anaya-Lara, University of Strathclyde

Marine Renewables Infrastructure Network

Status: Interim Report (2nd phase visit) Version: 01 Date: 19-Aug-2013

EC FP7 “Capacities” Specific Programme Research Infrastructure Action

Infrastructure Access Report: SYNERTIA

Rev. 01, 19-Aug-2013 of 14

ABOUT MARINET MARINET (Marine Renewables Infrastructure Network for emerging Energy Technologies) is an EC-funded network of research centres and organisations that are working together to accelerate the development of marine renewable energy - wave, tidal & offshore-wind. The initiative is funded through the EC's Seventh Framework Programme (FP7) and runs for four years until 2015. The network of 29 partners with 42 specialist marine research facilities is spread across 11 EU countries and 1 International Cooperation Partner Country (Brazil). MARINET offers periods of free-of-charge access to test facilities at a range of world-class research centres. Companies and research groups can avail of this Transnational Access (TA) to test devices at any scale in areas such as wave energy, tidal energy, offshore-wind energy and environmental data or to conduct tests on cross-cutting areas such as power take-off systems, grid integration, materials or moorings. In total, over 700 weeks of access is available to an estimated 300 projects and 800 external users, with at least four calls for access applications over the 4-year initiative. MARINET partners are also working to implement common standards for testing in order to streamline the development process, conducting research to improve testing capabilities across the network, providing training at various facilities in the network in order to enhance personnel expertise and organising industry networking events in order to facilitate partnerships and knowledge exchange. The aim of the initiative is to streamline the capabilities of test infrastructures in order to enhance their impact and accelerate the commercialisation of marine renewable energy. See www.fp7-marinet.eu for more details. Partners

Ireland University College Cork, HMRC (UCC_HMRC)

Coordinator

Sustainable Energy Authority of Ireland (SEAI_OEDU)

Denmark Aalborg Universitet (AAU)

Danmarks Tekniske Universitet (RISOE)

France Ecole Centrale de Nantes (ECN)

Institut Français de Recherche Pour l'Exploitation de la Mer (IFREMER)

United Kingdom National Renewable Energy Centre Ltd. (NAREC)

The University of Exeter (UNEXE)

European Marine Energy Centre Ltd. (EMEC)

University of Strathclyde (UNI_STRATH)

The University of Edinburgh (UEDIN)

Queen’s University Belfast (QUB)

Plymouth University(PU)

Spain Ente Vasco de la Energía (EVE)

Tecnalia Research & Innovation Foundation (TECNALIA)

Belgium 1-Tech (1_TECH)

Netherlands Stichting Tidal Testing Centre (TTC)

Stichting Energieonderzoek Centrum Nederland (ECNeth)

Germany Fraunhofer-Gesellschaft Zur Foerderung Der Angewandten Forschung E.V (Fh_IWES)

Gottfried Wilhelm Leibniz Universität Hannover (LUH)

Universitaet Stuttgart (USTUTT)

Portugal Wave Energy Centre – Centro de Energia das Ondas (WavEC)

Italy Università degli Studi di Firenze (UNIFI-CRIACIV)

Università degli Studi di Firenze (UNIFI-PIN)

Università degli Studi della Tuscia (UNI_TUS)

Consiglio Nazionale delle Ricerche (CNR-INSEAN)

Brazil Instituto de Pesquisas Tecnológicas do Estado de São Paulo S.A. (IPT)

Norway Sintef Energi AS (SINTEF)

Norges Teknisk-Naturvitenskapelige Universitet (NTNU)

http://www.fp7-marinet.eu/


Rev. 01, 19-Aug-2013 of 14

DOCUMENT INFORMATION Title Synthetic inertia from wind generation – power electronic converter capabilities Distribution Public Document Reference MARINET-TA1-SYNERTIA User-Group Leader, Lead Author

Olimpo Anaya-Lara University of Strathclyde 204 George Street, Glasgow, G1 1XW, United Kingdom

User-Group Members, Contributing Authors

Fan Zhang University of Strathclyde David Campos University of Strathclyde

Infrastructure Accessed: SINTEF Renewable Energy Lab - Smartgrids Infrastructure Manager (or Main Contact)

Atsede Endegnanew

REVISION HISTORY Rev. Date Description Prepared by

(Name) Approved By Infrastructure

Manager

Status (Draft/Final)

01 19/8/13 Interim report – second 2-week visit O. Anaya-Lara A. Endegnanew Final


Rev. 01, 19-Aug-2013 of 14

ABOUT THIS REPORT One of the requirements of the EC in enabling a user group to benefit from free-of-charge access to an infrastructure is that the user group must be entitled to disseminate the foreground (information and results) that they have generated under the project in order to progress the state-of-the-art of the sector. Notwithstanding this, the EC also state that dissemination activities shall be compatible with the protection of intellectual property rights, confidentiality obligations and the legitimate interests of the owner(s) of the foreground. The aim of this report is therefore to meet the first requirement of publicly disseminating the knowledge generated through this MARINET infrastructure access project in an accessible format in order to:

• progress the state-of-the-art • publicise resulting progress made for the technology/industry • provide evidence of progress made along the Structured Development Plan • provide due diligence material for potential future investment and financing • share lessons learned • avoid potential future replication by others • provide opportunities for future collaboration • etc.

In some cases, the user group may wish to protect some of this information which they deem commercially sensitive, and so may choose to present results in a normalised (non-dimensional) format or withhold certain design data – this is acceptable and allowed for in the second requirement outlined above.

ACKNOWLEDGEMENT The work described in this publication has received support from MARINET, a European Community - Research Infrastructure Action under the FP7 “Capacities” Specific Programme.

LEGAL DISCLAIMER The views expressed, and responsibility for the content of this publication, lie solely with the authors. The European Commission is not liable for any use that may be made of the information contained herein. This work may rely on data from sources external to the MARINET project Consortium. Members of the Consortium do not accept liability for loss or damage suffered by any third party as a result of errors or inaccuracies in such data. The information in this document is provided “as is” and no guarantee or warranty is given that the information is fit for any particular purpose. The user thereof uses the information at its sole risk and neither the European Commission nor any member of the MARINET Consortium is liable for any use that may be made of the information.


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EXECUTIVE SUMMARY Extensive research has been conducted on the provision of frequency support from variable-speed wind turbines employing different methodologies. However, in addition to the impacts on network operation, provision of short-term frequency support has implications on the turbines themselves. In essence, the control implementation to deliver the ‘synthetic inertia’ response required for the power system will introduce additional and significant torque demands on the turbine. In this research context, the main goal of this project is to observe experimentally and to assess the impact of different control loops for provision of synthetic inertia in the Doubly-fed Induction Generator (DFIG), and Fully-rated converter (FRC) power electronic converters. The work to be conducted in this project has been organised over 6 weeks of effective work in the lab at SINTEF. This is an Interim Report that covers the activities performed and results achieved during the second two-week visit. During these two weeks, a small scale power system which is able to demonstrate typical load change-frequency variation characteristic is set up as the test rig for DFIG frequency support controller. Two different types of . The DFIG and network models, which enable to represent the inertia response of the DFIG have been significantly improved and made compatible with the Opal-RT to be tested on the real machine.


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CONTENTS

1 INTRODUCTION & BACKGROUND ....................................................................................................................7

1.1 INTRODUCTION ..................................................................................................................................................... 7 1.2 DEVELOPMENT SO FAR .......................................................................................................................................... 8 1.2.1 Stage Gate Progress ..................................................................................................................................... 8

2 OUTLINE OF WORK CARRIED OUT ....................................................................................................................9

2.1 TESTS ................................................................................................................................................................ 10 2.1.1 Test Plan ..................................................................................................................................................... 10

2.2 RESULTS ............................................................................................................................................................ 10

3 REFERENCES ................................................................................................................................................. 14


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1 0BINTRODUCTION & BACKGROUND

1.1 3BINTRODUCTION Extensive research has been conducted on the provision of frequency support from variable-speed wind turbines employing different methodologies. However, in addition to the impacts on network operation, provision of short-term frequency support has implications on the turbines themselves. In essence, the control implementation to deliver the ‘synthetic inertia’ response required for the power system will introduce additional and significant torque demands on the turbine. In this research context, the main goal of this project is to observe experimentally and to assess the impact of different control loops for provision of synthetic inertia in the Doubly-fed Induction Generator (DFIG), and Fully-rated converter (FRC) power electronic converters. The capability tests will consist in triggering a kinetic energy release from the generators under different input torque conditions (emulating different wind speed inputs), and measuring the generated power output, its magnitude and behaviour, for both the DFIG and the FRC. Also, the impact of the sudden release of kinetic energy in the form of active power from the generators will be assessed for the partial-power back-to-back converter of the DFIG and the full-scale back-to-back converter of the FRC. Questions to be answered by this project are: How the proposed synthetic inertia controllers work in real conditions? Which wind generator technology is better suited for providing synthetic inertia? Which generator technology imposes less stress to their associated power electronics during the kinetic energy release? Do the back-to-back converters of the two wind generator technologies under test require being over-dimensioned? A diagram of connexion of the generators to the laboratory electrical network when studied separately is shown in Figure 1.

Figure 1. a) Connexion FRC generator to the laboratory electrical network. b) Connexion of the DFIG generator to the laboratory electrical

network.

a) b)


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1.2 4BDEVELOPMENT SO FAR Over the first two-week visit a working model of the DFIG in Simulink compatible for implementation in the Opal-RT has been completed and tested. This proved to be a challenging task as it required the preparation of a new model in Simulink (although preparation were made previously further refinement was carried out on site. In addition, a current controller for the DFIG was implemented and tested in the induction machine it he laboratory. Some connection issues were in the DFIG configuration were identified and corrected. Then the proper operation of the DFIG with controllers implemented in the Opal-RT was confirmed. This will allow the test experiment to carry as planned during the next two-week stay. During the second two-week visit, a completed simulation platform to test the inertia response of DFIG is set up. The DFIG and its control system which is prepared in the first visit is further tested and improved to be compatible with the grid. The controller parameters of the DFIG are carefully adjusted so that the DFIG has enough damping against the fluctuation in the power system. A synchronous generator with power control is set up to represent the power system behaviour. The power control allows the frequency of the test system to be adjusted manually. A resistor bank is injected to the grid as the total load. The resistor bank is designed with multi-level of resistance so that the load change in real power system can be simulated with this system. By connecting all components above, a one-bus simple power system is implemented for the test of the inertia response of the DFIG. Using the simulation platform, the test of the inertia response of DFIG using different control system and frequency support concept are carried out. The effect of having inertia support control on DFIG is tested under various load conditions. The result shows that DFIG is able to provide inertia response to a certain degree. However, it is also observed that the additional control loop has influence on the original DFIG controller. The design of the inertia response has to be chosen carefully. Further test on the DFIG with fully rated converter will be carried out in the next stage of this project.

1.2.1 7BStage Gate Progress Previously completed: Planned for this project:

STAGE GATE CRITERIA Status Stage 1 – Simulations • DFIG model in Matlab/Simulink • Grid model to represent inertia response characteristic • 3 types of DFIG controller to increase the inertia support from DFIG in Simulink • Validation of the effectiveness of the proposed controller • Modification of the Simulink model to be applied to real machine Stage 2 – Hardware set-up • Induction machine with speed control • Rotor and grid side converter for DFIG set-up • Applying DFIG controller on the induction machine and converters. • Synchronous generator set-up • Synchronous generator controller implementation • Load(capacitor bank) implementation • Integration of load and synchronous generator • Integration of DFIG into the test grid


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STAGE GATE CRITERIA Status • Stability improvement of test platform Stage 3 – Controller performance test • Frequency response of DFIG without supplementary controller • Inertia support of DFIG based on current mode control • Inertia support of DFIG based on FMAC • Inertia support of DFIG with fully rated converter

2 1BOUTLINE OF WORK CARRIED OUT The work carried out during these two weeks focuses on the set-up of a small scale electrical network which is employed to represent the characteristic of the grid, the integration of the DFIG and controller which is built during the first visit into the electrical network and the test of two different types of frequency control loop for DFIG. The details of the achievement during these two weeks are described below. 1. A synchronous generator with power/speed control is set up and tested. The generator with larger capacity than

the DFIG is built to represent the power system. 2. A resistor bank with variable resistance is connected to the electrical network to represent the load characteristic

of the power system. 3. The DFIG is connected to the simple power system and the basic controller of DFIG is proved to be effective. The

DFIG is able to supply desired power into the grid. 4. A frequency support control loop works on the frequency deviation in the power system is tested and the result

shows that this control loop is able to effectively reduce the frequency deviation in the power system. 5. A frequency support control loop with FMAC controller is tested. The control loop is designed based on frequency

domain analysis. The effect of improved grid frequency response is observed in low frequency domain. However, the DFIG operation in high frequency is affected which leads to poor transient response of DFIG FMAC control. The performance of the controller may be improved by tuning the controller. Due to the time limit, this work is not able to be done during this visit. The tuning and possibly design of the controller will be adjusted in the next visit and the result will be reported.


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2.1 5BTESTS The proposed frequency controller is tested with the test rig described above. The effect of having inertia support on DFIG is briefly shown below.

2.1.1 8BTest Plan 1. Case study of inertia response of DFIG when grid experiencing sudden load increase. 2. Case study of inertia response of DFIG when grid experiencing sudden load lost. 3. Inertia response of DFIG with FMAC concept

2.2 6BRESULTS Selected results showing that DFIG provides inertia response is provided in this section. The inertia response control system is switch on when grid is experiencing over frequency caused by sudden loss of loads.

Figure 2-1: Grid frequency


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Figure 2-2: Stator power

Figure 2-3: Rotor power


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Figure 2-4: Rotor converter d-axis voltage

Figure 2-5: Rotor converter q-axis voltage


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Figure 2-6: Stator converter d-axis voltage

Figure 2-7: Stator converter q-axis voltage

It is shown in the result that the DFIG is able to provide inertia support to the grid. The amount of the frequency support is limited by the capacity of the DFIG. Both the rotor and stator side converter are stressed to a certain level.


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The voltage and power in converters are increased to provide additional power to the grid in order to control the frequency. The result using FMAC control is not able to be recorded because of the hardware limit. The FMAC control is effective in longer term therefore requires record with longer time duration which current OPAL-RT system is not able to provide. With improved design, it is observed that the transient response of the FMAC control with inertia support is improved as well. This control scheme will be re-designed or re-tuned and the improved result may be able to be provided in the next phase of this project.

3 2BREFERENCES 1. Campos-Gaona, D., Moreno-Goytia, E., Anaya-Lara, O., "Fault Ride-Through Improvement of DFIG-WT by

Integrating a Two-Degrees-of-Freedom Internal Model Control," IEEE Transactions on Industrial Electronics, In-Press, DOI: 10.1109/TIE.2012.2216234, June 2012

2. Anaya-Lara, O., Hughes, F. M., Jenkins, N., and Strbac, G.: “Contribution of DFIG-based wind farms to power system short-term frequency regulation,” IEE Proceedings Generation, Transmission and Distribution, Vol. 153, No. 2, pp. 164-170, March 2006.

3. Hughes, F. M., Anaya-Lara, O., Jenkins, N., and Strbac, G.: “Control of DFIG-based wind generation for power network support,” IEEE Transactions on Power Systems, Vol. 20, No. 4, pp. 1958-1966, November 2005.

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