Power calculation algorithm under nonlinear loads and Hopf oscillator-based synchronization controller for grid-forming inverters in a microgrid

(English) In the grid-forming control of microgrids, the droop control is a widely used for the parallel operation of power inverters, but has some peculiarities as slow dynamic and inaccuracy in the power sharing. In the droop control, the power calculation of the active and reactive powers determi...

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Autor: Li, Mingshen
Tipo de recurso: tesis doctoral
Fecha de publicación:2023
País:España
Institución:Universitat Politècnica de Catalunya (UPC)
Repositorio:UPCommons. Portal del coneixement obert de la UPC
Idioma:inglés
OAI Identifier:oai:upcommons.upc.edu:2117/396557
Acceso en línea:https://hdl.handle.net/2117/396557
https://dx.doi.org/10.5821/dissertation-2117-396557
Access Level:acceso abierto
Palabra clave:Àrees temàtiques de la UPC::Enginyeria elèctrica
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repository_id_str
dc.title.none.fl_str_mv Power calculation algorithm under nonlinear loads and Hopf oscillator-based synchronization controller for grid-forming inverters in a microgrid
title Power calculation algorithm under nonlinear loads and Hopf oscillator-based synchronization controller for grid-forming inverters in a microgrid
spellingShingle Power calculation algorithm under nonlinear loads and Hopf oscillator-based synchronization controller for grid-forming inverters in a microgrid
Li, Mingshen
Àrees temàtiques de la UPC::Enginyeria elèctrica
title_short Power calculation algorithm under nonlinear loads and Hopf oscillator-based synchronization controller for grid-forming inverters in a microgrid
title_full Power calculation algorithm under nonlinear loads and Hopf oscillator-based synchronization controller for grid-forming inverters in a microgrid
title_fullStr Power calculation algorithm under nonlinear loads and Hopf oscillator-based synchronization controller for grid-forming inverters in a microgrid
title_full_unstemmed Power calculation algorithm under nonlinear loads and Hopf oscillator-based synchronization controller for grid-forming inverters in a microgrid
title_sort Power calculation algorithm under nonlinear loads and Hopf oscillator-based synchronization controller for grid-forming inverters in a microgrid
dc.creator.none.fl_str_mv Li, Mingshen
author Li, Mingshen
author_facet Li, Mingshen
author_role author
dc.contributor.none.fl_str_mv Matas Alcalá, José
Guerrero Zapata, Josep Maria
dc.subject.none.fl_str_mv Àrees temàtiques de la UPC::Enginyeria elèctrica
topic Àrees temàtiques de la UPC::Enginyeria elèctrica
description (English) In the grid-forming control of microgrids, the droop control is a widely used for the parallel operation of power inverters, but has some peculiarities as slow dynamic and inaccuracy in the power sharing. In the droop control, the power calculation of the active and reactive powers determines the speed of the controller capability to share linear and nonlinear loads. Therefore, the thesis address first the design of advanced filters to improve the dynamic response for droop-based inverters. And, a fast and accurate power calculation technique is proposed for three-phase inverters by using a two-stage combined Second Order Generalized Integrator (SOGI) approach to overcome this obstacle. The two-stage combined SOGI filter structure achieves the average active and reactive powers, used as the kernel for the droop-method operation. A small-signal model of a paralleled three-phase inverters is developed for determining the dynamic response of the system, which shows that the proposal is faster than the conventional droop method when both methods are designed under the same conditions. The proposal can be used to improve the stability and transient response of droop-operated inverters. After, a novel synchronization method based on Andronov-Hopf oscillators is proposed for driving paralleled single and three-phase power inverters, which show to have lower harmonics, faster dynamic response, and higher synchronization speed than the achieved by previous nonlinear Van der Pol oscillators, used as virtual oscillator controllers (VOC). The coupling strength between Hopf oscillators relies on the local feedback of the output current, which is able to synchronize with the rest of parallel inverters, without using communications. The Hopf equations considering the current feedback generates the voltage reference for the power inverters, and has a dual-loop that is designed in a static reference frame. The Hopf has a pre-synchronization stage that allows a softer connection of additional inverters. A small-signal state-space model for two parallel VSI is built and compared with a standard droop controller. The root locus exhibits a larger stability margin and lower parameter sensitivity. Finally, a grid-forming controller based on the Hopf oscillator is proposed that is able to synchronize and achieve accurate power tracking of the references. The Hopf model is analyzed and the synchronization region is obtained by using the Arnold tongue method. In this controller, the active power can be regulated by phasor, and a PI regulator is introduced in the reactive loop to control the amplitude voltage based on the Q - V relationship achieved by the Hopf. Matlab/PLECS simulation studies and experiments on a single phase and three-phase inverters platform are conducted in a microgrid laboratory to verify the proposed control strategies. The simulations of the proposed power calculation method presents a faster and more accurate performance when sharing nonlinear loads compared with the LPF-droop. In the case of the Hopf oscillator, the simulation and experimental results demonstrate a faster transient response and better robustness compared with the standard droop controller, and a wider operating range compared with the Van der Pol VOC. The Thesis has been organized in five sections: Section 1 introduces the background, state of the art, objectives, methodology, contributions and limitations of the work; Section 2 describes the proposed power calculation method using the combined SOGI filters approach; Section 3 is devoted to the Hopf oscillator control operating in an islanded microgrid; Section 4 describes the desing of the Hopf oscillator to operate with grid forming inverters; Section 5 is devoted to conclusions and forecast future line works.
publishDate 2023
dc.date.none.fl_str_mv 2023
2023-01-23
2023
2023-11-16
dc.type.none.fl_str_mv doctoral thesis
http://purl.org/coar/resource_type/c_db06
VoR
http://purl.org/coar/version/c_970fb48d4fbd8a85
dc.type.openaire.fl_str_mv info:eu-repo/semantics/doctoralThesis
format doctoralThesis
dc.identifier.none.fl_str_mv https://hdl.handle.net/2117/396557
https://dx.doi.org/10.5821/dissertation-2117-396557
url https://hdl.handle.net/2117/396557
https://dx.doi.org/10.5821/dissertation-2117-396557
dc.language.none.fl_str_mv Inglés
eng
language_invalid_str_mv Inglés
language eng
dc.rights.none.fl_str_mv open access
http://purl.org/coar/access_right/c_abf2
dc.rights.openaire.fl_str_mv info:eu-repo/semantics/openAccess
rights_invalid_str_mv open access
http://purl.org/coar/access_right/c_abf2
eu_rights_str_mv openAccess
dc.format.none.fl_str_mv application/pdf
dc.publisher.none.fl_str_mv Universitat Politècnica de Catalunya
publisher.none.fl_str_mv Universitat Politècnica de Catalunya
dc.source.none.fl_str_mv reponame:UPCommons. Portal del coneixement obert de la UPC
instname:Universitat Politècnica de Catalunya (UPC)
instname_str Universitat Politècnica de Catalunya (UPC)
reponame_str UPCommons. Portal del coneixement obert de la UPC
collection UPCommons. Portal del coneixement obert de la UPC
repository.name.fl_str_mv
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spelling Power calculation algorithm under nonlinear loads and Hopf oscillator-based synchronization controller for grid-forming inverters in a microgridLi, MingshenÀrees temàtiques de la UPC::Enginyeria elèctrica(English) In the grid-forming control of microgrids, the droop control is a widely used for the parallel operation of power inverters, but has some peculiarities as slow dynamic and inaccuracy in the power sharing. In the droop control, the power calculation of the active and reactive powers determines the speed of the controller capability to share linear and nonlinear loads. Therefore, the thesis address first the design of advanced filters to improve the dynamic response for droop-based inverters. And, a fast and accurate power calculation technique is proposed for three-phase inverters by using a two-stage combined Second Order Generalized Integrator (SOGI) approach to overcome this obstacle. The two-stage combined SOGI filter structure achieves the average active and reactive powers, used as the kernel for the droop-method operation. A small-signal model of a paralleled three-phase inverters is developed for determining the dynamic response of the system, which shows that the proposal is faster than the conventional droop method when both methods are designed under the same conditions. The proposal can be used to improve the stability and transient response of droop-operated inverters. After, a novel synchronization method based on Andronov-Hopf oscillators is proposed for driving paralleled single and three-phase power inverters, which show to have lower harmonics, faster dynamic response, and higher synchronization speed than the achieved by previous nonlinear Van der Pol oscillators, used as virtual oscillator controllers (VOC). The coupling strength between Hopf oscillators relies on the local feedback of the output current, which is able to synchronize with the rest of parallel inverters, without using communications. The Hopf equations considering the current feedback generates the voltage reference for the power inverters, and has a dual-loop that is designed in a static reference frame. The Hopf has a pre-synchronization stage that allows a softer connection of additional inverters. A small-signal state-space model for two parallel VSI is built and compared with a standard droop controller. The root locus exhibits a larger stability margin and lower parameter sensitivity. Finally, a grid-forming controller based on the Hopf oscillator is proposed that is able to synchronize and achieve accurate power tracking of the references. The Hopf model is analyzed and the synchronization region is obtained by using the Arnold tongue method. In this controller, the active power can be regulated by phasor, and a PI regulator is introduced in the reactive loop to control the amplitude voltage based on the Q - V relationship achieved by the Hopf. Matlab/PLECS simulation studies and experiments on a single phase and three-phase inverters platform are conducted in a microgrid laboratory to verify the proposed control strategies. The simulations of the proposed power calculation method presents a faster and more accurate performance when sharing nonlinear loads compared with the LPF-droop. In the case of the Hopf oscillator, the simulation and experimental results demonstrate a faster transient response and better robustness compared with the standard droop controller, and a wider operating range compared with the Van der Pol VOC. The Thesis has been organized in five sections: Section 1 introduces the background, state of the art, objectives, methodology, contributions and limitations of the work; Section 2 describes the proposed power calculation method using the combined SOGI filters approach; Section 3 is devoted to the Hopf oscillator control operating in an islanded microgrid; Section 4 describes the desing of the Hopf oscillator to operate with grid forming inverters; Section 5 is devoted to conclusions and forecast future line works.(Català) En el control per la formació de microxarxes, es fa servir àmpliament el control droop per la paral·lelització d'inversors de potència. No obstant, aquest tipus de control, encara es caracteritza per tenir una dinàmica lenta i un repartiment imprecís de les potències entre convertidors. En primer lloc, en el control droop, el càlcul de les potències activa i reactives determina la velocitat a la qual el control és capaç de compartir càrregues lineals i no lineals. Per tant, aquesta tesi s'enfoca primer en el disseny de filtres avançats per la millora de la resposta dinàmica dels convertidors que fan servir aquest mètode, proposant un nou mètode de càlcul per obtenir, de forma ràpida i precisa, aquestes potències per inversors trifàsics, fent servir una doble estructura combinada de filtres SOGI (Second Order Generalized Integrator), capaç d'obtenir les potències promitjades activa i reactives, necessàries per al sistema. Pel disseny es fa servir un model en petit senyal d'un sistema paral·lelitzat de dos inversors trifàsics, que mostra ser més ràpid que el mètode convencional, considerant les mateixes condicions operatives. La proposta millora l'estabilitat i la resposta transitòria del sistema. En segon lloc, es presenta un mètode innovador de sincronització basat en oscil·ladors de tipus Andronov-Hopf per aconseguir la paral·lelització de convertidors de potència monofàsics i trifàsics, que mostra resultats amb menys harmònics, resposta transitòria més ràpida, i major velocitat de sincronització que l'aconseguida pels oscil·ladors no lineals de Van der Pol. Els oscil·ladors Hopf es caracteritzen pel seu llaç local de realimentació del corrent de sortida, que és capaç de sincronitzar els inversors paral·lelitzats sense fer servir comunicacions. L'oscilador Hopf està constituït per unes equacions que inclouen els corrents de l'inversor i proporcionen les tensions de referència que han de seguir els inversors de potència i que formen un llaç de control dual que es dissenya en el domini estàtic de referència. L'oscil·lador Hopf contempla una part de pre-sincronització per assegurar una connexió suau dels convertidors addicionals a la xarxa de convertidors operant en paral·lel. Aquí també es desenvolupa un model en petit senyal d'un sistema de convertidors en paral·lel que es compara amb el model droop estàndard. L'anàlisi de les arrels en el domini de Laplace mostra que el sistema d'oscil·ladors aconsegueix un millor marge de fase, millora l'estabilitat i té menor sensibilitat paramètrica. Finalment, l'oscil·lador Hopf es dissenya per donar suport a la xarxa (grid-forming) amb la capacitat de sincronitzar i tenir un seguiment acurat de les consignes de referència. Aquest control fa servir una estructura PI dins del llaç de potència reactiva per regular l'amplitud del voltatge, fent servir la relació natural Q - V de l'oscil·lador. Es presenten simulacions amb Matlab i resultats experimentals per inversors monofàsics i trifàsics per contrastar l'anàlisi teòric fet. Els resultats de la proposta pel càlcul de les potències mostren ser més ràpids i precisos en el compartiment de càrregues no lineals que els obtinguts per l'estàndard mètode droop. En el cas de l'oscil·lador Hopf, les simulacions i resultats experimentals mostren també una resposta transitòria més ràpida i més robustesa que els obtinguts pel control estàndard droop, a més d'un major marge d'operació en contrast amb el mètode de Van der Pol. Aquesta tesi està organitzada en cinc seccions: la secció 1 introdueix l'estat de l'art, els objectius, la metodologia, les contribucions i limitacions; la secció 2 descriu el mètode de càlcul de les potències basat en l'estructura combinada de filtres SOGI; la secció 3 descriu el control amb l'oscil·lador Hopf operant dins una microxarxa en mode illa; la secció 4 descriu el disseny del control Hopf dissenyat per als inversors grid-forming; i la secció 5 dona les conclusions i futures línies de treball.Universitat Politècnica de CatalunyaMatas Alcalá, JoséGuerrero Zapata, Josep Maria20232023-01-2320232023-11-16doctoral thesishttp://purl.org/coar/resource_type/c_db06VoRhttp://purl.org/coar/version/c_970fb48d4fbd8a85info:eu-repo/semantics/doctoralThesisapplication/pdfhttps://hdl.handle.net/2117/396557https://dx.doi.org/10.5821/dissertation-2117-396557reponame:UPCommons. Portal del coneixement obert de la UPCinstname:Universitat Politècnica de Catalunya (UPC)Inglésengopen accesshttp://purl.org/coar/access_right/c_abf2info:eu-repo/semantics/openAccessoai:upcommons.upc.edu:2117/3965572026-05-27T15:37:01Z
score 15,301629

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