Open Access
Control of a photovoltaic array interfacing current-mode-controlled boost converter based on virtual impedance emulation
(IEEE, 2019) Urtasun Erburu, Andoni; Samanes Pascual, Javier; Barrios Rípodas, Ernesto; Sanchis Gúrpide, Pablo; Marroyo Palomo, Luis; Ingeniería Eléctrica, Electrónica y de Comunicación; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren
Due to the nonlinear characteristics of a photovoltaic (PV) array, its regulation is highly dependent on the operating point. Focusing on a dc-dc boost converter, this paper first shows how the PV voltage and inductor current controls are affected by the PV array. It then proposes to emulate an impedance virtually connected to the PV array, making it possible to greatly improve the control robustness. Thanks to the proposed strategy, the crossover frequency variation for the whole operating range is reduced from 42 times for the traditional control to 3.5 times when emulating parallel resistance or to 1.4 times when emulating series and parallel resistances, all with simple implementation. Experimental results with a commercial PV inverter and a 4-kWp PV array validate the theoretical analysis and demonstrate the superior performance of the proposed control.
Open Access
High frequency power transformers with foil windings: maximum interleaving and optimal design
(IEEE, 2015) Barrios Rípodas, Ernesto; Urtasun Erburu, Andoni; Ursúa Rubio, Alfredo; Marroyo Palomo, Luis; Sanchis Gúrpide, Pablo; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
Foil conductors and primary and secondary interleaving are normally used to minimize winding losses in high frequency transformers used for high-current power applications. However, winding interleaving complicates the transformer assembly, since taps are required to connect the winding sections, and also complicates the transformer design, since it introduces a new tradeoff between minimizing losses and reducing the construction difficulty. This paper presents a novel interleaving technique, named maximum interleaving, that makes it possible to minimize the winding losses as well as the construction difficulty. An analytical design methodology is also proposed in order to obtain free cooled transformers with a high efficiency, low volume and, therefore, a high power density. For the purpose of evaluating the advantages of the proposed maximum interleaving technique, the methodology is applied to design a transformer positioned in the 5 kW 50 kHz intermediate high frequency resonant stage of a commercial PV inverter. The proposed design achieves a transformer power density of 28 W/cm3 with an efficiency of 99.8%. Finally, a prototype of the maximum-interleaved transformer is assembled and validated satisfactorily through experimental tests.
Open Access
Control design and stability analysis of power converters: the discrete generalized Bode criterion
(IEEE, 2021) Urtasun Erburu, Andoni; Samanes Pascual, Javier; Barrios Rípodas, Ernesto; Sanchis Gúrpide, Pablo; Ingeniería Eléctrica, Electrónica y de Comunicación; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren
For the controller design and stability analysis of power electronic converters, the Bode stability criterion and its subsequent revisions are the most practical tools. However, even though the control of the power converter is usually implemented in a microprocessor, none of these methods is infallible when applied to a discrete system. This article therefore proposes a new stability criterion, named the Discrete Generalized Bode Criterion (DGBC). This method is based on the Nyquist criterion but developed from the open-loop Bode diagram, evaluated also at 0 Hz and at the Nyquist frequency. The proposed criterion combines the advantages of the Nyquist and Bode criteria, since it is always applicable and provides an interesting and useful tool for the controller design process. The method is applied to design an active damping control of an inverter with LCL filter, showing how the proposed criterion accurately predicts stability, in contrast to the existing Bode criteria. The theoretical analysis is validated through experimental results performed with a three-phase inverter and an LCL filter.
Open Access
On the stability of advanced power electronic converters: the Generalized Bode Criterion
(IEEE, 2019) Lumbreras Magallón, David; Barrios Rípodas, Ernesto; Urtasun Erburu, Andoni; Ursúa Rubio, Alfredo; Marroyo Palomo, Luis; Sanchis Gúrpide, Pablo; Ingeniería Eléctrica, Electrónica y de Comunicación; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
A key factor in the design of power electronic converters is the development of control systems and, in particular, the determination of their stability. Due to ease of application, the Bode criteria are currently the most commonly used stability criteria, both with regard to its classic version and to the subsequent revisions proposed in the literature. However, as these criteria have a limited range of applicability, on occasions it is necessary to resort to other universally applicable criteria such as the Nyquist criterion. Unlike Bode, the Nyquist criterion can always be applied, although its use considerably complicates the tuning of the controller. This paper proposes a new stability criterion, called Generalized Bode Criterion, which is based on the Nyquist criterion and, therefore, always applicable, but calculated from both the Bode diagram and the 0 Hz phase of the open-loop transfer function, thus making the criterion easy to be applied. This way, the proposed criterion combines the advantages of Nyquist and Bode criteria and provides an interesting and useful tool to help in the controller design process. The validation of the criterion is made on a voltage control loop for a stand-alone PV system through simulation and experimental tests made on a voltage control loop for a stand-alone PV system including a battery, a boost converter, an inverter and an ac load. The tests are also used to show the limitations of the classic Bode criterion and its revisions to correctly determine the stability of complex systems. IEEE
Open Access
Hydrogen educational activities developed by APERNA: a renewable-energy student association
(Asociación Española del Hidrógeno, 2016) Berrueta Irigoyen, Alberto; San Martín Biurrun, Idoia; Samanes Pascual, Javier; Pascual Miqueleiz, Julio María; Barrios Rípodas, Ernesto; Parra Laita, Íñigo de la; Urtasun Erburu, Andoni; Sanchis Gúrpide, Pablo; Ursúa Rubio, Alfredo; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren; Institute of Smart Cities - ISC; Ingeniería Eléctrica, Electrónica y de Comunicación
In this paper, we present APERNA, a recently-created student association at Public University of Navarre (UPNA) with the aim of promotion of renewable energies.
Open Access
Control design and stability analysis of power converters: the MIMO generalized bode criterion
(IEEE, 2020) Samanes Pascual, Javier; Urtasun Erburu, Andoni; Barrios Rípodas, Ernesto; Lumbreras Magallón, David; López Taberna, Jesús; Gubía Villabona, Eugenio; Sanchis Gúrpide, Pablo; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren; Institute of Smart Cities - ISC; Ingeniería Eléctrica, Electrónica y de Comunicación
Three-phase dynamic systems and multiphase generators are frequently modeled and controlled in the synchronous reference frame. To properly model the cross-coupling terms in this reference frame, complex vector theory and transfer function matrices are commonly applied, obtaining multiple-input multiple-output (MIMO) dynamic models. The stability of MIMO systems can be assessed through the Nyquist generalized stability criterion. However, the use of the Nyquist diagram complicates the controller design. The Bode diagram is a more intuitive tool for the controller design; however, the Bode stability criterion is not applicable to MIMO systems. In this article, the MIMO generalized Bode criterion is proposed. Since this stability criterion is based on the Nyquist generalized stability criterion, it can be applied to any system. Furthermore, it is simple to use, as it only requires information contained in the open-loop transfer matrix and the Bode diagram. The proposed stability criterion thus offers an interesting tool for the controller design procedure in MIMO systems, as it is shown in this article for two common applications: the current control loop of a power converter, a 2 × 2 system, and the current control loop of two independent power converters in parallel, a 4 × 4 system.
Open Access
Frequency-based energy management strategy for stand-alone systems with distributed battery storage
(IEEE, 2015) Urtasun Erburu, Andoni; Barrios Rípodas, Ernesto; Sanchis Gúrpide, Pablo; Marroyo Palomo, Luis; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
Distributed generation is an attractive solution for stand-alone AC supply systems. In such systems, the installation of two or more energy-storage units is recommended for system redundancy and may also be required when there is a consumption increase following installation. However, energy management with multiple energy-storage units has been but vaguely analyzed in the literature and the few studies made are based on communication cables with a central supervisor. This paper proposes an energy management strategy for a multiple-battery system which makes it possible to avoid the use of communication cables, rendering the system more cost-effective and reliable. The strategy modifies the conventional droop method so that the power becomes unbalanced, allowing for the regulation of one or more battery voltages or currents, as required. Furthermore, whenever the frequency is high, the PV inverters reduce their power in order to prevent the battery from overcharge or high charging currents. On the other hand, whenever the frequency is low, then either the non-critical loads are regulated or the system stops in order to prevent the battery from over-discharge or high discharging currents. Simulation and experimental validation are performed for a system with two battery inverters, two PV inverters and a number of loads.
Open Access
The generalized bode criterion: application to the dc voltage control of a three-phase photovoltaic grid-tied inverter
(IEEE, 2019) Lumbreras Magallón, David; Barrios Rípodas, Ernesto; Urtasun Erburu, Andoni; Sanchis Gúrpide, Pablo; Institute of Smart Cities - ISC; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
As renewable energies are becoming more important in the electrical generation system, power electronic converters are facing new design issues related not only to their components but also to their control loops. In this context, the Generalized Bode Criterion (GBC) appears as a good tool to correctly determine stability and to help the controller design. In order to show the potential of the GBC and how it can be applied, this paper studies a dc voltage regulation with compensation of the photovoltaic power in a three-phase photovoltaic grid-tied inverter.