Control of microgrids with flexible9 structure: a passivity framework

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1 Control of microgrids with flexible9 1 0 structure: a passivity framework 2 a h p m Giancarlo Ferrari Trecate C T E S y r é Automatic Control Laboratory École Polytechnique Fédérale de Lausanne (EPFL), Switzerland n 2 F d P E 07 February 2019

2 Outline Decentralized control design for systems with flexible structure DC microgrids: primary voltage control A passivity framework for stability of interconnected systems DC microgrids: passivation of different generation units Conclusions and perspectives

3 Systems with flexible structure Models Network of coupled subsystems Flexibility: subsystems enter/leave faulty components, hardware upgrade, subsystem addition,

4 Systems with flexible structure Models Network of coupled subsystems Flexibility: subsystems enter/leave faulty components, hardware upgrade, subsystem addition, Control architecture Decentralized/distributed How to design local controllers without a global model? when subsystems plug in/out?

5 Scalable design Decentralized design Pros [Bailey 66], [Findeisen 82], [Bakule & Lunze, 88]... Scalable algorithm Coupling-independent properties Privacy compliant

6 Scalable design Decentralized design Pros [Bailey 66], [Findeisen 82], [Bakule & Lunze, 88]... Scalable algorithm Coupling-independent properties Privacy compliant Subsystem plug-in: no need to update other controllers

7 Scalable design Decentralized design Pros [Bailey 66], [Findeisen 82], [Bakule & Lunze, 88]... Scalable algorithm Coupling-independent properties Privacy compliant Subsystem plug-in: no need to update other controllers Cons: limited information When decentralized design is feasible? 1

8 Decentralized design of primary voltage control in DC microgrids

9 DC microgrids E S C T a h 2 y r é p m Courtesy of Siemens Energy Networks of distributed generation units (DGUs) and loads P E Technology drivers for DC microgrids DC loads and storage: servers, electric vehicles, batteries... Renewable DC sources: PV panels,... n 2 F d Key challenge in islanded mode control of individual DGUs for voltage stabilization, current sharing,

10 DC microgrids: model

11 DC microgrids: model Buck i RL filter i V ti I ti PCC i Low-voltage DGU - Buck converter with RLC filter I Li C ti V i R ij Coupling L ij Control input

12 DC microgrids: model Buck i RL filter i V ti I ti PCC i Low-voltage DGU - Buck converter with RLC filter I Li C ti V i - ZIP load at PCC R ij L ij

13 DC microgrids: model Buck i RL filter i V ti I ti PCC i Low-voltage DGU - Buck converter with RLC filter - ZIP load at PCC I Li C ti V i R ij L ij DGUs connected by RL lines

14 DC microgrids: voltage control Buck i RL filter i V ti I ti PCC i I Li C ti V i Goal: tracking of voltage references at PCCs irrespectively of coupling/loads Related works under simplifying model assumptions: [Tucci et al. 16], [Zhao et al. 15], [De Persis et al. 18],... R ij L ij

15 DC microgrids: voltage control Buck i RL filter i V ti I ti PCC i I Li C ti V i R ij L ij M. Tucci, S. Riverso, and G. Ferrari-Trecate. Line-independent plug-and-play controllers for voltage stabilization in DC microgrids. IEEE Transactions on Control Systems Technology, 2018

16 Decentralized control design Buck i RL filter i V ti I ti PCC i I Li C ti V i R ij L ij P. Nahata, R. Soloperto, M. Tucci, A. Martinelli, and G. Ferrari-Trecate. A Passivity-Based Approach to Voltage Stabilization in DC Microgrids with ZIP loads, Tech. report. EPFL and IEEE American Control Conference (ACC), 2018

17 Decentralized control design Buck i RL filter i V ti Main results I ti PCC i I Li C ti V i Asymptotically stable offset-free voltage tracking in the whole microgrid Decentralized design of local controllers R ij L ij P. Nahata, R. Soloperto, M. Tucci, A. Martinelli, and G. Ferrari-Trecate. A Passivity-Based Approach to Voltage Stabilization in DC Microgrids with ZIP loads, Tech. report. EPFL and IEEE American Control Conference (ACC), 2018

18 Why it works? Buck i RL filter i V ti I ti PCC i I Li C ti V i DGUs and lines are interconnected in a skew-symmetric, (energyneutral) fashion Asymptotic stability of the controlled microgrid R ij L ij

19 A passivity framework for interconnected system

20 Stability and skew-symmetric interconnection <latexit sha1_base64="d2x

21 Stability and skew-symmetric interconnection <latexit sha1_base64="d2x

22 Stability and skew-symmetric interconnection <latexit sha1_base64="d2x

23 Stability and skew-symmetric interconnection <latexit sha1_base64="d2x

24 Stability and skew-symmetric interconnection <latexit sha1_base64="d2x Related results: [Kiang, 2017], [Van der Schaft, 2017], [Arcak, 2016, 2007], [Burger & De Persis, 2015],

25 Application to DC microgrids Lines and DGUs are input-affine systems (up to a state shift) Controlled DGUs are locally passive with Lines are inherently passive with Skew-symmetric interconnection P. Nahata, R. Soloperto, M. Tucci, A. Martinelli, and G. Ferrari-Trecate. A Passivity-Based Approach to Voltage Stabilization in DC Microgrids with ZIP loads, Tech. report. EPFL and IEEE American Control Conference (ACC), 2018

26 Passivation of different DGU models

27 Voltage-controlled DGU with exponential load Buck i RL filter i V ti ZIE load at PCC I ti PCC i I Li C ti V i R ij L ij

28 Voltage-controlled DGU with exponential load Buck i RL filter i V ti ZIE load at PCC I ti PCC i I Li C ti V i R ij L ij

29 Current-controlled DGU Current tracking grid-feeding converter R. Han, M. Tucci, R. Soloperto, J. M. Guerrero, G. Ferrari-Trecate Plug-and-play current controllers for grid-feeding converters in DC microgrids IEEE Asian Control Conference (ASCC), 2017

30 Cluster of V-DGU and C-DGU (ZI load) Grid-feeding/forming converters[1] [1] V. Nasirian, S. Moayedi, A. Davoudi, F. L. Lewis. Distributed cooperative control of dc microgrids. IEEE Transactions on Power Electronics, 2015 [2] R. Han, M. Tucci, A Martinelli, J. M. Guerrero, G. Ferrari-Trecate Stability Analysis of Primary Plug-and-Play and Secondary Leader-based Controllers for DC Microgrid Clusters IEEE Transactions on Power Systems,2018, online

31 Medium-voltage DGUs Nonlinear dynamics of Boost converter The DGU can be passivated by a nonlinear controller Monday's poster session A Martinelli, P. Nahata, G. Ferrari-Trecate Voltage Stabilization in MVDC Microgrids Using Passivity-Based Nonlinear Control, IEEE Conference on Decision and Control (CDC), 2018

32 Experiments 2 y (Intelligent Microgrid Laboratory, Aalborg University) r é p m a h Microgrid topology L 3 R 12 L2 R13 DGU DGU 2 R2 n 2 F d P E E S C T L13 DGU 3 Ring electrical topology ZI loads Communication network

33 Experiment stages t = 0 s: DGU 2 DGU 1 DGU 3 Secondary layer disabled DGUs isolated and equipped with voltage controllers I t (A) V PCC (v) V av (v) I t1 I t2 I t Plug-in of DGUs and lines Secondary control active V PCC1 V PCC2 V PCC time (s)

34 Experiment stages R 12 L 12 DGU 2 DGU 1 DGU 3 Secondary layer disabled t = 2.5 s: DGUs 1 and 2 connected together I t (A) V PCC (v) V av (v) I t1 I t2 I t Plug-in of DGUs and lines Secondary control active V PCC1 V PCC2 V PCC time (s) Voltage stability and fast transients

35 Experiment stages R 12 L 12 DGU 2 R 13 L 13 R 23 L 23 DGU 1 DGU 3 Secondary layer disabled t = 5 s and t = 10 s: connect DGUs 1-3 and 2-3 (electrical ring) I t (A) V PCC (v) V av (v) I t1 I t2 I t Plug-in of DGUs and lines Secondary control active V PCC1 V PCC2 V PCC time (s) Safe and stable plug-in operations

36 Experiment stages R 12 L 12 DGU 2 R 13 L 13 R 23 L 23 DGU 1 DGU 3 Secondary layer enabled t = 15 s: Goal: same current for all DGUs I t (A) V PCC (v) V av (v) I t1 I t2 I t Plug-in of DGUs and lines Secondary control active V PCC1 V PCC2 V PCC time (s)

37 Experiment stages R 12 L 12 DGU 2 R 13 L 13 R 23 L 23 DGU 1 DGU 3 Secondary layer enabled t = 25 s: Load switch at PCC3 I t (A) V PCC (v) V av (v) I t1 I t2 I t Plug-in of DGUs and lines Secondary control active V PCC1 V PCC2 V PCC time (s)

38 Conclusions and perspectives

39 Conclusions and perspectives 1176 Decentralized control design for systems with flexible structure Stable and safe plug-in/out of subsystems Passivity-based control of DC microgrids Offset-free voltage tracking For AC microgrids with clock synchronisation IEEE TRANSACTIONS ON SMART GRID, VOL. 6, NO. 3, MAY 2015 Plug-and-Play Voltage and Frequency Control of Islanded Microgrids With Meshed Topology Stefano Riverso, Member, IEEE, Fabio Sarzo, and Giancarlo Ferrari-Trecate, Senior Member, IEEE

40 Conclusions and perspectives 1176 Decentralized control design for systems with flexible structure Stable and safe plug-in/out of subsystems Passivity-based control of DC microgrids Offset-free voltage tracking For AC microgrids with clock synchronisation IEEE TRANSACTIONS ON SMART GRID, VOL. 6, NO. 3, MAY 2015 Plug-and-Play Voltage and Frequency Control of Islanded Microgrids With Meshed Topology Stefano Riverso, Member, IEEE, Fabio Sarzo, and Giancarlo Ferrari-Trecate, Senior Member, IEEE Current/future research Cybersecurity for networked secondary layers (see poster session) Coupling with EMS for long-term operation

41 EPFL Pulkit Nahata Mustafa Università di Pavia Fabio Sarzo Michele Aalborg University Josep Guerrero Juan Carlos Vasquez Renke UTRC Stefano University of Stuttgart Raffaele ETH Andrea Martinelli

42 j k Secondary consensus layer m Itj 1 s Itj Network Itk n i Vi ++ Local controller 1 s Itk +- 1 s Iti RL filter Vti Buck i Plug-in of DGUs and lines It (A) V PCC (v) F d V av (v) n P E a h DGU i C T V 25 PCC1 30 I t1 I t2 I 35 V PCC2 35 t3 40 V PCC3 40 Thanks! time (s) 2 y r é p m DGU j ILi E S 1 5 line ij Vi Secondary control active Iti Cti Primary control layer 0 ki s Communication Vref,i