Distributed Control Strategy for Energy Storage Systems in AC Microgrids

174 Pages·2016·11.65 MB·English

by  Omid Palizban

OMID PALIZBAN
Distributed Control Strategy
for Energy Storage Systems
in AC Microgrids
Towards a Standard
Solution
ACTA WASAENSIA 356
ELECTRICAL ENGINEERING 5
Reviewers Associate Professor Alberto Borghetti
University of Bologna
Department of Electrical Power Systems
Viale del Risorgimento 2
40136 BOLOGNA BO
Italy
Professor Olli Pyrhönen
Lappeenranta University of Technology
School of Energy Technology
P. O. Box 20
FI-53851 LAPPEENRANTA
Finland
III
Julkaisija Julkaisupäivämäärä
Vaasan yliopisto Syyskuu 2016
Tekijä(t) Julkaisun tyyppi
Omid Palizban Artikkeliväitöskirja
Julkaisusarjan nimi, osan numero
Acta Wasaensia, 356
Yhteystiedot ISBN
Vaasan yliopisto 978-952-476-694-4 (painettu)
Teknillinen tiedekunta 978-952-476-695-1 (verkkojulkaisu)
Energiatekniikka ISSN
PL 700 0355-2667 (Acta Wasaensia 356, painettu)
FI-65101 VAASA 2323-9123 (Acta Wasaensia 356,
verkkojulkaisu)
1799-6961 (Acta Wasaensia. Sähkötekniikka 5,
painettu)
2343-0532 (Acta Wasaensia. Sähkötekniikka 5,
verkkojulkaisu)
Sivumäärä Kieli
174 englanti
Julkaisun nimike
Energiavarastojärjestelmien hajautettu säätöstrategia vaihtojännitteisissä
mikrosähköverkoissa: Tavoitteena standardiratkaisut
Tiivistelmä
Energiavarastot ovat merkittävä osa mikrosähköverkkoa. Tässä väitös-
kirjassa esitellään akkupohjaisten energiavarastojen hajautettu säätötapa,
joka perustuu kunkin yksittäisen akkuvaraston energia- eli varaustasoon.
Menetelmän toimivuus on verifioitu simulointien avulla. Akkuvaraston
varaustason poikkeama määritellään sekundäärisellä säätötasolla. Sieltä
se välitetään primääriselle säätötasolle, jossa tehty ohjaus palauttaa
varaustason haluttuun ohjearvoon. Primäärisellä säätötasolla käytetään
muokattua P/f-Q/V droop-säätöä, joka ottaa huomioon akkujen varaus-
tason.
Säätö asettaa droop-kertoimet perustuen kunkin akkuvaraston varaus-
tasoon siten, että kerroin on kääntäen verrannollinen varaustasoon akun
purkamisen aikana ja suoraan verrannollinen akun latauksen aikana. Tällä
säätöstrategialla varastoyksikkö, jolla on korkein (alin) energiataso,
syöttää enemmän (vähemmän) tehoa kuormaan varastojen toimiessa
tuotantoyksikköinä ja vastaanottaa energiaa pienemmällä (suuremmalla)
teholla sähkön tuotannon ylittäessä kysynnän.
Viime vuosina on pyritty löytämään standardiratkaisuja mikrosähkö-
verkkoihin ja tähän liittyen väitöskirjassa ehdotetaan IEC/ISO 62264 stan-
dardin soveltamista mikrosähköverkkoihin ja energiavarastoihin. IEC/ISO
62264 standardissa määritellään viisi tasoa, joilla on samat tavoitteet
aivan kuten hierarkkisessa mikrosähköverkkojen ja energiavarastojen
säädössä. Kehitettyä säätömenetelmää on tässä väitöskirjassa arvioitu
myös sovelletun standardin kannalta perustuen IEC/ISO 62264 standardin
eri tasojen määritelmiin ja vastaaviin hajautetunsäädön tasoihin.
Asiasanat
Hajautettu säätö, energiavarastojärjestelmät, hierarkkinen säätö, mikro-
sähköverkko, IEC 62264 standardi

V
Publisher Date of publication
Vaasan yliopisto September 2016
Author(s) Type of publication
Omid Palizban Doctoral thesis by publication
Name and number of series
Acta Wasaensia, 356
Contact information ISBN
University of Vaasa 978-952-476-694-4 (print)
Faculty of Technology 978-952-476-695-1 (online)
Energy Technology ISSN
P.O. Box 700 0355-2667 (Acta Wasaensia 356, print)
FI-65101 Vaasa 2323-9123 (Acta Wasaensia 356, online)
Finland 1799-6961 (Acta Wasaensia. Electrical
Engineering 5, print)
2343-0532 (Acta Wasaensia. Electrical
Engineering 5, online)
Number of pages Language
174 English
Title of publication
Distributed Control Strategy for Energy Storage Systems in AC Microgrids:
Towards a Standard Solution
Abstract
The energy storage system is a major part of a microgrid. A decentralized
control system for battery energy storage that operates on the basis of
the energy level of each storage unit is presented in this doctoral
dissertation together with some simulation based verifications. The
deviation of the SoC in the secondary control level is determined here
through proposed secondary control and sent to the primary control to
restore it. The primary level uses the P/f–Q/V droop control method, and
a modified droop control in the primary level based on the SoC of the
storage units is also employed here.
To set the droop coefficients based on the energy level of each storage
unit, the droop coefficient is inversely proportional to the energy level
during the discharging period and directly proportional during the
charging period. When this strategy is implemented, the storage unit with
the highest (lowest) energy level provides more (less) power to support
the load when the storage unit operates as a power supplier, and absorbs
less (more) power when the power generated exceeds the demand.
Over the last several years, efforts to standardize MGs have been made,
and it is in light of these advances that the current doctoral dissertation
also proposes the application of IEC/ISO 62264 standards to MGs and
ESSs. The IEC/ISO 62264 standard has five levels, with the same
objectives at each level as the hierarchical control of MGs and ESSs.
Considering the definitions of each level of the IEC/ISO 62264 standard
and the matching roles of the levels in decentralized control, the
proposed method is also evaluated based on the adopted standard.
Keywords
Distributed control , Energy storage system, Hierarchical control,
Microgrid, IEC 62264 standard

VII
ACKNOWLEDGEMENT
This work has been carried out at the Smart Electric System (SES) research group
of the Department of Electrical Engineering and Energy Technology, University
of Vaasa (UVA) from 2012 to 2016. Part of the research behind this thesis has
been conducted within the Smart Grids and Energy Market (SGEM) research
program of CLEEN Ltd. and funded by Finnish Funding Agency for Technology
and Innovation (Tekes). Furthermore, part of the doctoral dissertation has been
supported by UVA graduate school through two years of scholarship grants.
First of all, I would like to express my gratitude to the Almighty for His infinite
kindness. Next, I am indebted to the supervisor of this work, Professor Kimmo
Kauhaniemi, and I wish to express my deepest gratitude to him for his
guidance, encouragement, and valuable contributions during this work and his
long-time support of my research path. I am also thankful to Professor Josep
M. Guerrero of the Department of Energy Technology, Aalborg University,
Denmark, for his excellent advice and experience in encouraging my publications
and thesis. Moreover, I would also like to express thanks to Mr. Timo
Kankaanpää, who first introduced me to the leader of SES research group.
I thank the preliminary examiners, Professor Olli Pyrhönen from
Lappeenranta University of Technology (LUT) and Associate Professor
Alberto Borghetti from the University of Bologna for their valuable feedback
and comments, as well as their genuine interest in the topic and their willingness
to engage in the pre-examination process.
In addition, I would like to thank my research colleagues at SES research
laboratory who have created a great atmosphere for carrying out research work.
September 2016

IX
Contents
ACKNOWLEDGEMENT ............................................................................ VII
1 INTRODUCTION ................................................................................. 1
1.1 Microgrids ............................................................................... 1
1.2 Energy Storage Systems ........................................................... 3
1.3 Standardization ....................................................................... 4
1.4 Motivation for the work ........................................................... 5
1.5 Objectives of the work and research methods .......................... 6
1.6 Scientific Contribution ............................................................. 7
1.7 Outline of the thesis ................................................................ 8
1.8 Summary of publications ......................................................... 9
2 THEORETICAL FOUNDATION ............................................................ 12
2.1 Hierarchical control ............................................................... 12
2.1.1 Inner control loop (Zero level) ....................................... 13
2.1.2 Primary control ............................................................. 13
2.1.3 Secondary control ......................................................... 16
2.1.4 Tertiary Control ............................................................ 19
2.2 Energy storage systems ......................................................... 21
2.2.1 Energy storage technologies ......................................... 21
2.2.2 Energy storage applications .......................................... 23
2.2.3 Matrix of technologies and applications ........................ 25
2.3 Summary of the chapter ........................................................ 27
3 STANDARDIZATION ......................................................................... 29
3.1 Distribution system standardization ...................................... 30
3.1.1 IEC standards ............................................................... 30
3.1.2 IEEE standards .............................................................. 31
3.2 Hierarchical control based on IEC62264 standard .................. 32
3.3 Microgrid control standardization based on IEC 62264 .......... 34
3.4 Summary of the chapter ........................................................ 37
4 DISTRIBUTED CONTROL STRATEGY FOR ENERGY STORAGE
SYSTEMS.......................................................................................... 38
4.1 DG and ESS configuration ...................................................... 38
4.2 Decentralized energy control strategy for BESSs ..................... 41
4.3 Droop control based on SoC .................................................. 42
4.3.1 Discharging mode ........................................................ 43
4.3.2 Charging mode ............................................................. 45
4.4 Summary of Chapter .............................................................. 47
5 EVALUATION AND DISCUSSION ........................................................ 48
5.1 Evaluation .............................................................................. 48
5.2 Discussion ............................................................................. 51
5.3 Summary of the chapter ........................................................ 54
X
6 CONCLUSION .................................................................................. 55
6.1 Summary of research ............................................................. 55
6.2 Contributions ........................................................................ 56
6.3 Future work ........................................................................... 57
REFERENCES ......................................................................................... 59