Person: Marroyo Palomo, Luis
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Marroyo Palomo
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Luis
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Ingeniería Eléctrica, Electrónica y de Comunicación
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ISC. Institute of Smart Cities
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0000-0002-8344-8374
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495
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Publication Open Access A PV ramp-rate control strategy to extend battery lifespan using forecasting(Elsevier, 2022) González Moreno, Alejandro; Marcos Álvarez, Javier; Parra Laita, Íñigo de la; Marroyo Palomo, Luis; Ingeniería Eléctrica, Electrónica y de Comunicación; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren; Universidad Pública de Navarra / Nafarroako Unibertsitate PublikoaThis study analyses and presents a new ramp-rate control algorithm for smoothing PV power fluctuations, designed to address three fundamental objectives: to reduce battery cycling, to meet minimum storage requirements and to be able to operate, without ramp-rate violations, with real publicly-available forecasting. The algorithm was compared to three benchmark methods and, as a performance limit, also to a hypothetical perfect prediction. Different performance variables were analyzed for all the strategies within a restricted ramp-rate constraint (2%/min): minimum storage requirement, battery power distributions, throughput energy, state of charge (SOC) distributions, degradation (calendar and cycling), expected battery lifespan and levelized cost of energy (LCOE). The proposal proves to be the most cost-effective smoothing technique and the simulation results show that its performance is comparable to the obtained with the use of an assumed perfect prediction.Publication Open Access Energy management for an electro-thermal renewable based residential microgrid with energy balance forecasting and demand side management(Elsevier, 2021) Pascual Miqueleiz, Julio María; Arcos Avilés, Diego; Ursúa Rubio, Alfredo; Sanchis Gúrpide, Pablo; Marroyo Palomo, Luis; Ingeniería Eléctrica, Electrónica y de Comunicación; Institute of Smart Cities - ISC; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio IngeniaritzarenThis paper proposes an energy management strategy for a residential microgrid comprising photovoltaic (PV) panels, a small wind turbine and solar thermal collectors. The microgrid can control the power exchanged with the grid thanks to a battery and a controllable electric water heater, which provide two degrees of freedom to the control strategy. As input data, the proposed control strategy uses the battery state of charge (SOC), the temperature of the hot water tank, the power of each microgrid element as well as the demand and renewable generation forecasts. By using forecasted data and by controlling the electric water heater, the strategy is able to achieve a better grid power profile while using a smaller battery than previous works, hence reducing the overall cost of the system. The strategy is tested by means of simulation with real data for one year and it is also experimentally validated in the microgrid built at the Renewable Energy Laboratory at the UPNA.Publication Open Access Analysis of a CIS based PV generator versus a multicrystalline generator under outdoor long-term exposure(IEEE, 2021) Parra Laita, Íñigo de la; Guerra Menjívar, Moisés Roberto; Marcos Álvarez, Javier; García Solano, Miguel; Marroyo Palomo, Luis; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren; Institute of Smart Cities - ISC; Ingeniería Eléctrica, Electrónica y de ComunicaciónThe worldwide growth of the PV market has been almost exponential during the last years. Together with conventional crystalline (c-Si) PV modules, “new” commercially available PV technologies such as copper indium selenide (CIS) based solar cells have appeared achieving a similar efficiency comparable to c-Si at similar production cost. In addition to the use of cheaper materials, CIS solar cells manufacturers claim some enhancements such as lower temperature coefficient or higher absorption of diffuse light that achieve to reduce the cost of electrical energy. Although several papers deal with this topic, little is known about real comparisons between CIS technology and conventional crystalline at a PV generator level with real test conditions. This paper analyses the in-field performance and degradation of a commercially available CIS solar based PV generator compared to a conventional c-Si one during four years of operation attributing the differences observed to the possible factors that can influence in both technologies.Publication Open Access Power angle-frequency droop control to enhance transient stability of grid-forming inverters under voltage dips(IEEE, 2022) Erdocia Zabala, Ioseba; Urtasun Erburu, Andoni; Marroyo Palomo, Luis; Ingeniería Eléctrica, Electrónica y de Comunicación; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio IngeniaritzarenDue to the replacement of synchronous generators, grid operators are currently demanding to control grid-connected inverters in grid–forming mode to make them participate in the maintenance of the grid. To carry this out, the traditional droop controls based on the active and reactive powers are usually adopted, achieving a satisfactory performance in normal operation. Nevertheless, the power-frequency (P-ω) droop may become transiently unstable under voltage dips. This is because of the modification of the active power response caused by the inverter current limitation together with the voltage reduction. To enhance this, the power angle-frequency (δinv-ω) droop is proposed, consisting in employing an estimation of the inverter power angle as input to obtain the inverter frequency. The proposed method provides the inverter with the same performance as the P-ω droop in normal operation, while enhancing considerably the transient stability margins under current limitation. This is thanks to the higher variation of the inverter power angle with the phase difference between the inverter and the grid. Simulation results show the transient stability problems of the P-ω droop as well as the superior performance of the proposed δinv-ω droop control, which has also been verified by means of HIL results.Publication Open Access Effect of the inner current loop on the voltage regulation for three-phase photovoltaic inverters(IEEE, 2020) Urtasun Erburu, Andoni; Sanchis Gúrpide, Pablo; Marroyo Palomo, Luis; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren; Institute of Smart Cities - ISC; Ingeniería Eléctrica, Electrónica y de ComunicaciónIn three-phase grid-connected PV inverters, regulating the input voltage is a fundamental requirement. In order to reduce the influence of the PV non-linear behavior and ensure stability in the whole operating range, the input capacitance is currently oversized. This paper reveals the important effect of the inner current loop in the voltage stability and proposes to use a Proportional (P) controller instead of a PI controller. If tuned following the guidelines provided in this paper, the P controller makes it possible to design a stable voltage loop without increasing the input capacitance, thus reducing the converter cost.Publication Open Access Long-term degradation rate of crystalline silicon PV modules at commercial PV plants: an 82-MWp assessment over 10 years(Wiley, 2021) Pascual Miqueleiz, Julio María; Martínez Moreno, Francisco; García Solano, Miguel; Marcos Álvarez, Javier; Marroyo Palomo, Luis; Lorenzo Pigueiras, Eduardo; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren; Institute of Smart Cities - ISC; Ingeniería Eléctrica, Electrónica y de ComunicaciónDue to high competitiveness in the PV sector, despite the low degradation rate of crystalline silicon PV modules (below 0.5%/year), it is still important for utilities to know its actual value due to its impact on energy yield and hence, profitability, over the lifetime of a PV plant. However, uncertainties related to both the influence of downtime periods due to problems that may appear under normal operation of a commercial PV plant and to the measurement of degradation rates at PV plant level make this a challenging task. In order to obtain a significant value, in this paper, three measuring methods with different uncertainty sources are used for 82 MWp of PV modules on different locations in Spain and Portugal over 10 years. According to the different methods used and PV plants analyzed, excluding PV plants with problems, a range of degradation rates between 0.01 and 0.47%/year has been found. The overall average value observed is 0.27%/year. The findings of this work have also revealed the great importance of good operation and maintenance practices in order to keep overall low degradation rates.Publication Open Access High-dynamics P-E and Q-f control of PV inverters for strong and weak grids(IEEE, 2023-08-31) Urtasun Salinas, Ibai; Urtasun Erburu, Andoni; Marroyo Palomo, Luis; Ingeniería Eléctrica, Electrónica y de Comunicación; Ingeniaritza Elektrikoa, Elektronikoa eta Telekomunikazio Ingeniaritza; Institute of Smart Cities - ISCThe increase of power electronic-based generators is causing the replacement of synchronous generators, which poses new challenges to electrical grid stability. In particular, when grid-following inverters are connected to weak grids, stability problems related to the PLL used for synchronization arise. To address this issue, grid-forming controls are widely proposed. However, the conventional implementations, such as droop control or virtual synchronous generator, lead to slow power controls, which are not suitable for photovoltaic systems with no storage. Thus, to improve the control dynamics, this paper proposes a new P-E and Q-f control. This control uses the reactive power for grid synchronization, avoiding the use of a PLL, and is valid for both inductive and resistive lines. Furthermore, thanks to the controller design developed in the paper, the control remains rapid and stable for very weak grids. Simulation results validates the control design and shows that the proposed control is much faster than the droop control for all types of grids.Publication Open Access Analysis of polyamide and fluoropolymer backsheets: Degradation and insulation failure in field-aged photovoltaic modules(John Wiley & Sons, 2022) Pascual Miqueleiz, Julio María; García Solano, Miguel; Marcos Álvarez, Javier; Marroyo Palomo, Luis; Ingeniería Eléctrica, Electrónica y de Comunicación; Institute of Smart Cities - ISC; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren; Universidad Pública de Navarra / Nafarroako Unibertsitate PublikoaDurability of photovoltaic (PV) modules is of great concern not only from the point of view of cost-effectiveness but also from the point of view of safety and sustainability. The backsheet of a PV module is one of the most critical parts of the PV module from the point of view of protection and also one of the most important sources of PV modules' failure; hence, it is of great importance to understand its different forms of failure. In this paper we analyze the case of an 8-MW PV plant, which had suffered a rapid degradation of their PV modules' backsheets. The case is especially relevant as all the PV modules are from the same model and manufacturer but with different backsheet materials (polyamide and fluoropolymer) and different times of exposure: on one hand, all PV modules originally installed in the plant (i.e., 6 years under operation when tested), and also, extra modules that had been stored indoors for replacement and had been mounted in the plant for less than 1 year when tested, serving as reference modules. In this paper we present the signs of degradation of these PV modules after different times of exposure under real operation using different on-field and laboratory tests. We propose different techniques for rapid diagnosis of backsheet degradation so that the problem can be detected at a very early stage, before it results in major energy losses or in safety issues.Publication Open Access Modeling the inherent damping of high-power inverters(IEEE, 2020) Erdocia Zabala, Ioseba; Urtasun Erburu, Andoni; Marroyo Palomo, Luis; Ingeniería Eléctrica, Electrónica y de Comunicación; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio IngeniaritzarenIn order to decide whether passive or active damping is required in a three-phase inverter, a previous step is to assess the intrinsic damping of the system. However, few works focus on modeling this damping for DC/AC operation. This paper proposes two models to reproduce the damping sources: the simulation model, used to validate the system in large-signal, and the small-signal model, which can be employed for the controller design. Both models have been validated by means of experimental results for a 1.64 MVA inverter.Publication Open Access Outdoor performance of a CdTe based PV generator during 5 years of operation(IEEE, 2022) Guerra Menjívar, Moisés Roberto; Parra Laita, Íñigo de la; Marcos Álvarez, Javier; García Solano, Miguel; Marroyo Palomo, Luis; Ingeniería Eléctrica, Electrónica y de Comunicación; Institute of Smart Cities - ISC; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio IngeniaritzarenTogether with the huge growth of the traditional crystalline silicon (Si-x) PV manufacturers, other thin-film solar cells have also emerged such as cadmium telluride (CdTe) manufacturers. They are characterized by the fact that they were created to reduce costs and by the scarcity of silicon, from which the rest of the modules are made. Despite they need more space to generate the same amount of energy as crystalline modules, their price is supposed to be much lower, and argue that they have a better performance at high temperatures. However, real comparisons between the outdoor performance of CdTe and Si-x modules have been scarcely addressed in the literature. This paper provides a comparison under real operating conditions of a CdTe photovoltaic generator versus a conventional silicon generator during 5 years of operation in a mid-latitude area, identifying the causes of the differences observed.