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© 2024 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works., Grid-forming (GFM) control has been considered a promising solution for accommodating large-scale power electronics converters into modern power grids thanks to its grid-friendly dynamics, in particular, voltage source behavior on the AC side. The voltage source behavior of GFM converters can provide voltage support for the power grid, and therefore enhance the power grid (voltage) strength. However, grid-following (GFL) converters can also perform constant AC voltage magnitude control by properly regulating their reactive current, which may also behave like a voltage source. Currently, it still remains unclear what are the essential differences between the voltage source behaviors of GFL and GFM converters, and which type of voltage source behavior can enhance the power grid strength. In this paper, we will demonstrate that only GFM converters can provide effective voltage source behavior and enhance the power grid strength in terms of small signal dynamics. Based on our analysis, we further study the problem of how to configure GFM converters in the grid and how many GFM converters we will need. We investigate how the capacity ratio between GFM and GFL converters affects the equivalent power grid strength and thus the small signal stability of the system. We give guidelines on how to choose this ratio to achieve a desired stability margin. We validate our analysis using high-fidelity simulations., This work was jointly supported by the National Key Research and Development Program (2023YFB2406600) and the National Natural Science Foundation of China (No. U2166204 and No. 51922094). (Corresponding author: Linbin Huang.) H. Xin, C. Liu, and Y. Wang are with the College of Electrical Engineering, Zhejiang University, Hangzhou, China. (Email: xinhh@zju.edu.cn) X. Chen is with the School of Electrical and Electronic Engineering, Huazhong University of Science and Technology, Wuhan 430074, China. E. Prieto-Araujo is with the Electrical Engineering Department, Technical University of Catalonia, 08034 Barcelona, Spain. L. Huang is with the Department of Information Technology and Electrical Engineering at ETH Z¨ urich, Switzerland. (Email: linhuang@ethz.ch), Postprint (author's final draft)

This project focuses on the design of linear and non-linear controllers for a single-phase full-bridge photovoltaic (PV) inverter connected to the grid through two types of filters: L and LCL. Different simulation profiles in the Matlab/Simulink environment make it possible to verify the appropriate functionality of the system and, subsequently, to establish the differences and similarities between controllers with respect to their robustness and the resulting dynamics, among others. In addition, with the Typhoon ITL emulator, both the PV array and the inverter can be simulated in real time to observe their behaviour in a more realistic way., Este trabajo presenta el diseño de controladores lineales y no lineales para un inversor monofásico fotovoltaico de puente completo conectado a la red mediante dos tipos de filtros: L y LCL. Distintos perfiles de simulación en el entorno de Matlab/Simulink permiten verificar el correcto funcionamiento del conjunto y, posteriormente, establecer las diferencias y similitudes entre controladores respecto a su robustez y la dinámica resultante, entre otros. Además, con el emulador Typhoon ITL se consigue simular tanto la agrupación fotovoltaica como el inversor en tiempo real para observar su comportamiento de una manera más realista., Aquest treball presenta el disseny de controladors lineals i no lineals per un inversor monofàsic fotovoltaic de pont complet connectat a la xarxa mitjançant dos tipus de filtres: L i LCL. Diferents perfils de simulació a l'entorn Matlab/Simulink permeten verificar el correcte funcionament del conjunt i, posteriorment, establir les diferències i similituds entre controladors respecte la seva robustesa i la dinàmica resultant, entre d'altres. A més, amb l'emulador Typhoon ITL s'aconsegueix simular tant l'agrupació fotovoltaica com l'inversor en temps real per observar el seu comportament d'una manera més realista.

This paper presents a control strategy for the triple active bridge (TAB) converter based on the generalized average model (GAM). The TAB operation is summarized and the GAM derivation for the TAB is presented in detail. A control strategy based on the sum of feedback (FB) and feedforward (FF) terms is proposed to control the voltage at the output ports. The FB term comes from a PI controller designed using the pole placement method. On the other hand, the FF term depends on the load currents measurements and the transformer currents estimation obtained from GAM. Simulation results are presented to validate the control effectiveness. Also, the proposed control strategy is compared to the PI controller alone, exhibiting an improvement in the dynamic response., This work is part of the iPLUG project. This project has received funding from the European Union’s Horizon Europe research and innovation programme under grant agreement N. 101069770., Peer Reviewed, Postprint (published version)

Inertia emulation is claimed to play a decisive role in the regulation and management of frequency in modern electrical systems. The support offered by renewable energy power plants and distributed generators is key to diminish the rate of change of frequency (RoCoF), as many synchronous generators are being replaced all around the globe. It is a reality that the implementation of the swing equation in the power converter control has been the core of several proposals on grid-forming controllers to emulate inertia. This kind of controller has been heavily studied and integrated in some demonstrators around the world during the last years, providing dynamic inertia support functionalities. However, the need to modify the synchronization strategy in already deployed power units has been one of the key opposition factors on industry, leading to a severe shortcoming on the integration. In contrast to the traditional swing equation implementation this paper presents a lightweight inertial phase-locked loop (IPLL) able to take the most of inertial features introducing minor changes on classical power converter control and synchronization structures. As shown in this work, the straightforward implementation significantly reduces the technological and computational effort compared to other synchronous emulation proposals. Moreover, it integrates not only dynamic inertial response to the converter, but also all grid-forming capacities to the power conversion unit. This modification on the synchronization structure enables the converter to work in grid-following mode in grid-tied applications, and grid-forming in islanded ones. The integration of the proposed IPLL, the stability analysis and a sample of its performance in HIL and experimental environments will be presented in this paper., This work was supported by the Margarita Salas Program promoted by the Spanish Ministry of Universities under Grant GA 94126., Peer Reviewed, Postprint (published version)

© 2022 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works., In islanded AC microgrids, when multiple voltage source inverters (VSIs) operate in parallel, it is challenging to simultaneously obtain both accurate complex (active and reactive) power sharing and voltage regulation (in terms of frequency and amplitude). State-of-the-art strategies that target these two objectives often rely on hierarchical primary droop plus communication-based both secondary controls and adaptive virtual impedance methods. However, control dynamics and/or accuracy are still affected by inverters line impedances mismatches. To overcome these limitations, this paper presents for balanced AC microgrids a distributed control strategy that simultaneously guarantees both voltage regulation and accurate power sharing. The distributed strategy is based on having at each VSI a single controller that merges two control loops that can be designed in isolation, thus decoupling the design of the power sharing control from the design of the voltage control. The cooperative operation of all VSI controllers, that requires exchanging control data over a communication network, ensures meeting both control objectives with independence of the line impedance mismatches or the connection and disconnection of inverters and loads. And these properties are achieved without changing the controller structure and (easy-to-tune) parameters nor increasing the control effort. Experimental results corroborate the control proposal., This work was partially supported by I+D+i RTI2018-100732-B-C22 re-search project, financed by MCIN/AEI/10.13039/501000011033 and FEDER“Una manera de hacer Europa”., Peer Reviewed, Postprint (published version)

This work deals with the study and design of solar panel charge regulators, which are responsible for mediating between the generated energy of photovoltaic panels and the loads to feed, in DC. Specifically, two typologies are studied, the PWM typology (from its acronym Pulse Width Modulation) and the MPPT (from its acronym Maximum Power Point Tracking), each using a different power management algorithm and hence a different electrical circuit design. First is explained the theory behind each of these regulators, followed with designs and simulations and ended with the physical realization of a prototype and a printed circuit board. To conclude, the results are extracted and the two typologies are compared. It should be mentioned that every charge regulator has a part of hardware and software and in this work only the hardware part is studied, thus deepening the physical design of the electrical circuit., Este trabajo trata el estudio y el diseño de los reguladores de carga de paneles solar, estos son los encargados de hacer de mediadores entre la energía generada de placas fotovoltaicas y las cargas para ser alimentadas, en continua. Concretamente, se estudian dos tipologías, la tipología PWM (de su acrónimo Pulse Width Modulation) y la MPPT (de su acrónimo Maximum Power Point Tracking), cada una utiliza un algoritmo de gestión de energía diferente y, por lo tanto, un diseño del circuito eléctrico diferente. Primero se explica la teoría detrás de cada uno de los reguladores, se sigue con los diseños y simulaciones y se acaba con la realización física de un prototipo y de una placa de circuito impreso. Para concluir se extraen los resultados y se comparan las dos tipologías. Hay que mencionar que todo regulador de carga tiene una parte de hardware y una de software y en este trabajo solo se estudia la parte de hardware, profundizando así en el diseño físico del circuito eléctrico., Aquest treball tracta l’estudi i el disseny dels reguladors de càrrega de panells solar, aquests són els encarregats de fer de mediadors entre l’energia generada de plaques fotovoltaiques i les càrregues per ser alimentades, en contínua. Concretament, s’estudien dues tipologies, la tipologia PWM (del seu acrònim Pulse Width Modulation) i la MPPT (del seu acrònim Maximum Power Point Tracking), cada una utilitza un algorisme de gestió d’energia diferent i, per tant, un disseny del circuit elèctric diferent. Primer s’explica la teoria darrera de cada un dels reguladors, se segueix amb els dissenys i simulacions i s’acaba amb la realització física d’un prototip i d’una placa de circuit imprès. Per concloure s’extrauen els resultats i es comparen les dues tipologies. Cal esmentar que tot regulador de càrrega té una part de hardware i una de software i en aquest treball només s’estudia la part de hardware, profunditzant així en el disseny físic del circuit elèctric.

This study proposes a control scheme for high power grid-connected wind power converters, which is oriented to enhance their performance when connected to weak grids with low short circuit ratio. The proposed controller consists of an outer current reference generation loop and an inner current loop, working in stationary reference frame. In the outer loop, the current reference is calculated to comply simultaneously with the grid code requirements, the control of the DC link, and the operational safety margins of the converter during faulty conditions. On the other hand, the proposed inner current loop consists of a proportional resonant controller, a capacitor voltage feedforward and a phase shifter. Moreover, simulation results considering different weak grid conditions, as well as experimental results of a full-scale 4 MW converter test-bench are presented to validate the good performance of the proposed method., This work has been partially suported by the Spanish Ministry of Science and Universities under the code RTI2018-100921-B-C21 and Tecniospring programme under the code TECSPR16-1-006., Peer Reviewed, Postprint (published version)

This paper is a postprint of a paper submitted to and accepted for publication in IET Power Electronics and is subject to Institution of Engineering and Technology Copyright. The copy of record is available at the IET Digital Library., During voltage sags, distributed generation systems must fulfil specific grid-code requirements for reactive current injection. This ancillary service can produce overvoltage problems in networks operating in unbalanced conditions when the amplitude of one of the phase voltages is higher than the others and a balanced reactive current is injected through large grid impedance. This study proposes a control scheme to avoid these overvoltage problems, thus reducing the risk of cascade disconnection that this incident may produce. The derivation of the control scheme starts from the flexible oscillating-power control, introduces the necessary modifications so that this control meets the grid-code requirements for current injection and combines it with a slope voltage control to achieve a good voltage regulation. A theoretical analysis is included to determine the expressions that quantify the voltage support characteristics of the proposal. Finally, selected experimental results are reported to validate the characteristics of the proposed control., Peer Reviewed, Postprint (author's final draft)

© 2020 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works, In this work, a complex-valued controller for a three-phase VSC with an LC output filter is proposed. The system is first transformed into its complex representation with the consequent order reduction and simpler analysis. The proposed complex controller places all the poles at desirable locations in the complex plane. Unlike classical controllers with an inner current-control loop and outer voltage-control loop, the proposed controller considers the complete dynamics of the system, thus ensuring the closed-loop stability. Furthermore, the complex representation facilitates the pole placement in the complex plane compared to the real domain. The performance of the proposed controller is validated through simulations and experiments., Postprint (published version)

Formula Student es una competición mundial en la que los estudiantes fabrican autos de carreras de tipo fórmula. El año pasado, el equipo Driverless UPC, formado por alumnos de la ETSEIB y la ETSETB, adaptó todos los sistemas electrónicos de un coche de fórmula eléctrico clásico, para transformarlo en un coche autónomo. El nuevo automóvil trajo consigo nuevos desafíos, las computadoras, actuadores y dispositivos de enfriamiento agregados aumentaron el consumo total de corriente del suministro regulado de 24V. El primer año resolvimos el problema con los reguladores DC-DC comerciales, pero resultaron ser costosos y no se integraron correctamente con el paquete electrónico ya establecido. Entonces, para el segundo año, decidimos desarrollar nuestros propios convertidores que se adaptaran mejor a nuestras necesidades. Este proyecto tiene como objetivo desarrollar una prueba de concepto para un convertidor DC-DC que funcione con el paquete electrónico ya establecido, utilizando el conocido microcontrolador STM32 y utilizándolo como dispositivo de potencia para un convertidor DC-DC buck-boost., Formula Student és una competició mundial on els estudiants fabriquen cotxes de carreres de tipus fórmula. L’any passat, l’equip Driverless UPC, format per estudiants de l’ETSEIB i l’ETSETB, va adaptar tots els sistemes electrònics d’un cotxe de fórmula elèctrica per transformar-lo en un cotxe autònom. El nou cotxe va comportar nous reptes, els ordinadors, actuadors i dispositius de refrigeració afegits van augmentar el consum total actual de subministrament regulat de 24 V. El primer any vam resoldre el problema amb reguladors DC-DC comercials, però van resultar ser cars i no es van integrar correctament amb el paquet electrònic ja establert. Per tant, al segon any vam decidir desenvolupar els nostres propis convertidors que s’adaptessin millor a les nostres necessitats. Aquest projecte té com a objectiu desenvolupar una prova de concepte per a un convertidor de DC-DC que funcioni amb el paquet electrònic ja establert, utilitzant el conegut microcontrolador STM32 i fent-lo servir com a dispositiu de control per a un convertidor de DC-DC de tipus Buck-boost., Formula Student is a worldwide competition where students manufacture formula race cars. Last year, the Driverless UPC team, formed by ETSEIB and ETSETB students, adapted all the electronic systems of a classic electric formula car, to transform it into an autonomous car. The new car brought in new challenges, the added computers, actuators and cooling devices increased the total current consumption from the regulated 24V supply. The first year we solved the issue with commercial DC-DC regulators but they turned out to be expensive and did not integrate properly with the already stablished electronics package. So, for the second year we decided to develop our own converters that would suit better our needs. This project aims to develop a proof of concept for a DC-DC converter that works with the already stablished electronics package, using the well-known STM32 microcontroller and using it as a power device for a buck-boost DC-DC converter.

This article aims to present the design of a 4.5-V, 450-mA low drop-out (LDO) voltage linear regulator based on a two-stage cascoded operational transconductance amplifier (OTA) as error amplifier. The aforementioned two-stage OTA is designed with cascoded current mirroring technique to boost up the output impedance. The proposed OTA has a DC gain of 101 dB under no load condition. The designed reference voltage included in the LDO regulator is provided by a band gap reference with the temperature coefficient (T¿) of 0.025 mV/ºC. The proposed LDO regulator has a maximum drop-out voltage of 0.5 V @ 450 mA of load current, and has the worst case power supply rejection ratio (PSRR) of [54.5 dB, 34.3 dB] @ [100 Hz, 10 kHz] in full load condition. All the proposed circuits are designed using a 0.35 µm CMOS technology. The design is checked in order to corroborate its performance for wide range of input voltage, founding that the circuit design works fine meeting all the initial specification requirements., Postprint (published version)

The increasing penetration of grid-connected RES systems, advanced control algorithms have been developed to operate under grid faults and fulfill strict requirements of the grid codes. In order to overcome this, the current controller performance is critical considering it as the inner control loop of any grid-connected RES system. Based on the resonant control concept, this paper presents a modified structure for this controller which results advantageous when implemented on RES systems, as it permits better performance during the dynamic state of the controller. This paper also deals with the analysis of the decoupling terms in the aß reference frame, as well as the capability to generate a decoupled control of the positive and the negative sequence. The proposed controller will be analyzed, discussed and finally validated by means of simulation analysis., Peer Reviewed, Postprint (author's final draft)

© 2017 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works., The accurate control of the line current, robust and dynamic behavior even under distorted grids and other system faults are the most important requirements for grid-connected inverters. Applying direct current control to multilevel inverters combines the advantages of both and is an enabling step towards improved inverter performance. Direct current controllers suffer from high complexity at increased level count, which is resolved by using geometrical principles and simple analytical calculations for switching vector selection within the space vector diagram. The simplified, novel parametric controller concept is scalable to inverters with arbitrary level count, which does not require any switching tables and the new fully symmetric setup guarantees equal switching frequencies among the three phases. The hypotheses are further confirmed on a real hardware test setup on the example of a three-level NPC inverter hardware and a Xilinx development platform. Experimental results prove the expected behavior of the direct current control under various conditions, which shows a general approach to balance the dc-link capacitors of diode-clamped inverters within the theoretical limits and demonstrates the benefits of using field programmable gate arrays as a controller platform., Postprint (author's final draft)

This paper discusses the implementation of proportional resonant (PR) current controllers for a Voltage Source Converter (VSC) with LCL filter which is synchronized to the grid by virtual flux (VF) estimation with inherent sequence separation. Even though there is an extensive amount of literature and studies on the PR current controller for tracking the current reference of a VSC in the stationary reference frame, there is no discussion taking into account voltage sensor-less operation based on virtual flux estimation with an LCL-filter. Separate estimation of the positive and negative sequence virtual flux components at the grid-side of the LCL-filter, as well as current sequence separation, using the Second Order Generalized Integrator-Frequency Locked Loop (SOGI-FLL) is presented as part of a proposed method. The LCL filter is characterized in order to reduce the parameter deviation that might affect the virtual flux estimation. The stability of the proposed method is analyzed in the frequency domain while the operation and performance of the proposed system is verified by simulation studies., Peer Reviewed, Postprint (author's final draft)

Actualmente la sociedad se está concienciando cada vez más de la importancia y el alto coste que supone generar energía, y por ello, una buena gestión de la energía se está tornando un imperativo, haciendo de la electrónica de potencia algo indispensable en la industria. Los convertidores de potencia permiten controlar los flujos de potencia eléctrica y adaptar la forma en la que se presenta para adecuarla a las necesidades de cada situación, y todo ello minimizando las pérdidas que se puedan ocasionar en dicha gestión. Sin embargo, para conseguir su objetivo, introducen armónicos de alta frecuencia a la corriente eléctrica. El presente trabajo trata sobre el análisis y diseño de un controlador para un convertidor de potencia de topología SEPIC, siempre desde un marco teórico. El trabajo engloba desde las bases de teoría de circuitos para modelizar el convertidor hasta las simulaciones llevadas a cabo para varias tensiones de alimentación y cargas, pasando por el cálculo de puntos de operación, la dinámica cero del convertidor y el diseño del controlador y sus parámetros. Finalmente se concluye el trabajo con los resultados obtenidos, validando el diseño del controlador obtenido; seguido de un análisis de impacto medioambiental y un presupuesto.

Renewable energy sources are increasing their penetration in power systems, making necessary new control systems that offer services usually provided only by conventional generators. In this paper, an active power controller able to achieve synchronization with the grid and to control the DC link voltage is proposed. This controller allows identifying the converter with a virtual synchronous generator whose inertia can be modified online, considering that its virtual kinetic energy is stored in the DC link. Additionally, the resulting active power loop is a second order system whose damping factor can be defined freely., Peer Reviewed, Postprint (published version)

This paper describes a control design methodology based on output impedance analysis for multiphase synchronous buck converters. This design leads to an optimal output voltage transient response. Two design alternatives are proposed. The first alternative uses an equivalent single-phase converter to design the control parameters. This approximation is valid as long as the deviations between the phases of the converter are within the usual tolerance limits. The second one achieves exact constant resistive output impedance regardless of the differences that exist between the phases. Simulation and experimental results are reported in order to validate the two design approaches., Postprint (published version)

Premi extraordinari doctorat curs 2012-2013, àmbit d’Enginyeria Industrial, Wind power has emerged as one of the most promising renewable energy sources. The very penetration levels of wind energy in power systems have altered several aspects of power system operation, such as system stability. Owing to the large penetration of wind power, transmission system operators (TSOs) have established special grid codes for wind farms connection. These grid codes require wind farms to provide ancillary services to the grid such as frequency and voltage regulation. In the near future, the capability of damping power system oscillations will be required. As a result of the development of such requirements, the concept of wind power plant (WPP) arises being de ned as a wind farm which is expected to behave similarly to a conventional power plant in terms of power generation, control and ancillary services. As future grid codes will require power oscillation damping contribution from wind power, the thesis is mainly focused on the analysis of the power system stabilizer (PSS) capability of wind power plants. The change produced by wind power plants based on di erent wind turbine technologies on power system small signal dynamics is analysed to determine their possible contribution to damp oscillations. The eff ect of the distance from the tie line to the wind power plant on the controller response and the influence of wind power plants proximity to synchronous generators are demonstrated to be critical factors. At this point several questions are raised as: What are the most critical factors? How can be ensure a proper contribution, at least the best possible response? Can it be ensured to be independent to the power system and the controller selected? To answer these questions, this thesis conducts research on proper selection of input-output signal pairs to damp out electromechanical oscillations using wind power plants without drawing attention to a particular control design. This is necessary conclusions about the power system independently of a par, L'energia e olica s'ha convertit en una de les fonts d'energia renovable m es prometedores. Actualment, l'elevat nivell de penetraci o de l'energia e olica a la xarxa el ectrica ha conduï t a la modi caci o del comportament de diversos aspectes d'aquesta, com per exemple, l'estabilitat. Degut a aquesta gran penetraci o, els operadors de xarxes de transmissi o (TSOs) han establert procediments d'operaci o especials per a la connexi o de grans parcs e olics. Aquests codis requereixen als parcs elics que realitzin serveis auxiliars al sistema el ectric com, per exemple, la regulaci o de freqü encia i la regulaci o de la pot encia reactiva. En un futur proper, la capacitat dels parcs e olics per esmorteir les oscil lacions del sistema de pot encia es requerir a (en l'actualitat ja existeixen esborranys de nous procediments d'operaci o que ho inclouen). A causa d'aquest requeriments, el concepte de central de generaci o d'energia e olica es de neix com un parc e olic que s'espera que es comporti de manera similar a una central de generaci o el ectrica convencional en termes de poder realitzar tasques tals com generaci o, control i serveis auxiliars. Ja que un futur requeriment dels operadors de xarxa ser a la contribuci o de l'energia e olica en l'esmorteiment de les oscil lacions de pot encia, en aquesta tesi s'estudia la capacitat de les centrals e oliques per actuar com estabilitzador dels sistemes el ectrics de pot encia. A m es a m es, s'analitza l'efecte de les centrals d'energia e olica al comportament din amic del sistema el ectric considerant l'estabilitat de petita senyal, per a determinar quina podr a ser la possible contribuci o proporcionada per aquestes tecnologies. S'ha estudiat que l'efecte de la dist ancia des d'el punt de connexi o amb la central d'energia e olica a la resposta del control estabilitzant i la influ encia de la proximitat de les centrals e oliques als generadors s ncrons s on factors cr tics. D'aquest fet surgeixen algunes preguntes com, Award-winning, Postprint (published version)

In a voltage source inverter, overmodulation is required to extend the range of operation and enhance the dclink voltage utilization. A carrier-based implementation of a modulation strategy for the three-level neutral-point-clamped inverter is proposed for the overmodulation region. The modulation strategy ensures zero average neutral-point current in a switching period. A newly proposed boundary compression is used to regulate the dc-link voltage at all operating points. A description of the algorithm to implement the modulation strategy is also presented. The main advantage of the proposed algorithm is its simplicity. The reference signals for the PWM can be calculated using maximum six steps and does not require knowledge of the reference vector angle. The modulation strategy has been implemented in a three-level neutral-point-clamped inverter, and experimental results are presented., Postprint (published version)

A three-level neutral-point-c1amped inverter needs a controller for the neutral-point voltage. Typically, the controller design is based on a dynamic model. The dynamic model of the neutral-point voltage depends on the pulse width modulation technique used for the inverter. A pulse width modulation strategy which allows modeling the neutral-point voltage as a first-order continuous function is proposed in this paper. The new model shows that the neutral-point current is proportional to the reactive power drawn from the inverter. Since the model is a first-order model, a simple proportional controller is used in this paper to control the neutral-point voltage. Experimental results verifying the proposed modulation strategy and the controller are also presented in this paper., Postprint (published version)

This paper proposes a simple method for inherently frequency-adaptive virtual flux (VF) estimation intended for voltage-sensor-less grid synchronization and control of voltage source converters. The frequency-adaptive characteristics are obtained by using a second-order generalized integrator configured as a quadrature signal generator (SOGI-QSG) with the grid frequency as an explicit input variable. It is also shown how the properties of VF estimation based on SOGI-QSGs can be utilized to achieve a simple and effective synchronization technique that integrates frequency-adaptive bandpass filtering, VF estimation, and symmetrical component sequence separation into one operation. This new method avoids cascaded delays of VF estimation and sequence separation and is labeled as dual SOGI-based VF (DSOGI-VF) estimation since it is based on two parallel SOGI-QSGs. The properties and performance of the DSOGI-VF estimation are analyzed in comparison to conventional configurations of VF estimation and sequence separation, demonstrating that it is a simpler structure with improved dynamic response. In fact, similar response time as for grid synchronization based on voltage measurements is achieved. The operation and performance of the proposed DSOGI-VF estimation method have been verified by laboratory experiments in a small-scale converter setup., Peer Reviewed, Postprint (published version)

Larger percentages of wind power penetration translate to more demanding requirements from grid codes. Recently, voltage support at the point of connection has been introduced by several grid codes from around the world, thus, making it important to analyze this control when applied to wind power plants. This paper addresses the analysis of two different voltage control strategies for a wind power plant, i.e. decentralized and centralized voltage control schemes. The analysis has been performed using the equivalent and simplified transfer functions of the system. Using this representation, it is possible to investigate the influence of the plant control gain, short circuit ratio, and time delays on the system stability, as well as the fulfillment of the design requirements., Peer Reviewed, Postprint (published version)

A possible methodology for the power sharing is based on DC voltage droop control at onshore station converters. The aim is to present an evaluation tool for the droop control parameter description in support of DC power sharing. Main limitation for this method regarding sharing factors definition and overvoltages are going to be revised. A study case using two different onshore stations are going to be used. Both of them are sized with different power ratings and they have different distances from the offshore converters. This benchmark is suitable as starting point for future prospects of DC supergrids. Using the concept of virtual impedances, the droop parameters are limited by the boundaries of the DC voltage limits and line characteristics. For the power sharing point of view, mainly the cable resistances are considered. Simulation results using time domain simulation (EMTDC/PSCAD) will reinforce the methodology. The approach can be considered as a general case from the previous control schemes based on voltage droop. The work extends the purpose to power sharing characteristic and it can be useful when the converters have different sizes or/and there are restrict agreements among all the operators at onshore AC systems, Postprint (published version)

This paper presents a novel hysteretic controller for a multiphase synchronous buck converter supplying low voltage, high current, and high slew-rate loads. The control scheme implements the main control functions for powering such demanding loads, including output-voltage regulation, adaptive voltage positioning, current sharing, and phase interleaving. This paper also describes a control-design methodology based on outputimpedance analysis. This design leads to optimal output-voltage transient response with a simple and low-cost control implementation. Simulation and experimental results are reported in order to validate the features of the novel control scheme., Peer Reviewed, Postprint (published version)

L'objecte d'aquest projecte consisteix en el disseny d'un sistema de control a través d'una xarxa amb el protocol de comunicació industrial CAN (Controller Area Network). Aquesta estarà formada per un node de perifèria descentralitzada proporcionant una entrada i una sortida analògiques, i per un node PC amb la finalitat de controlar el motor de corrent continu situat al laboratori d'Informàtica Industrial de l'edifici TR11 de l'Escola Tècnica Superior d'Enginyeries Industrial i Aeronàutica de Terrassa (Universitat Politècnica de Catalunya).