Grupo de Sistemas Electrónicos Industriales
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- PublicationA Control Stage for Parallel-Connected Interlinking Converters in Hybrid AC-DC Microgrids(Institute of Electrical and Electronics Engineers, 2023) Liberos Mascarell, María Antonia; González Medina, Raúl; Patrao Herrero, Iván; Torán Mort, Enric; Garcerá Sanfeliú, Gabriel; Figueres Amorós, Emilio; Dpto. de Ingeniería Electrónica; Escuela Técnica Superior de Ingeniería del Diseño; Escuela Técnica Superior de Ingeniería Industrial; Grupo de Sistemas Electrónicos Industriales; AGENCIA ESTATAL DE INVESTIGACION[EN] Having two or more interlinking converters connected in parallel in hybrid microgrids has some benefits, like modularity, flexibility, and redundancy. However, the parallelization of the inverters leads to circulating currents that can cause system malfunctions. This work uses a method for suppressing low-frequency circulating currents in interlinking converters by controlling the zero-sequence component of the phase currents, showing that the control structure is valid for interlinking converters. The proposed control scheme has been applied to two parallel interlinking inverters of 5 kW and 2.5 kW, respectively. The interlinking inverters are connected to the grid, and they control the voltage in the DC bus of the hybrid microgrid. To validate the concept, simulation and experimental results are shown.
- PublicationDC-Bus Signaling control laws for the operation of DC-microgrids with renewable power sources(IEEE, 2023) Patrao Herrero, Iván; Torán Mort, Enric; González Medina, Raúl; Liberos Mascarell, María Antonia; Figueres Amorós, Emilio; Garcerá Sanfeliú, Gabriel; Dpto. de Ingeniería Electrónica; Escuela Técnica Superior de Ingeniería del Diseño; Escuela Técnica Superior de Ingeniería Industrial; Grupo de Sistemas Electrónicos Industriales; Agencia Estatal de Investigación; European Regional Development Fund; Ministerio de Asuntos Económicos y Transformación Digital[EN] DC-Bus Signaling (DBS) is a proven method to coordinate different microgrid agents, using the DC voltage of the microgrid as a communication signal. The droop control applied in a DC microgrid achieves accurate power-sharing among converters while leading to a certain voltage regulation error in the microgrid bus. The behaviour of the different agents in a microgrid is managed by using the voltage at each node of the microgrid as the DBS signal. The technique proposed in this paper uses an improved DBS technique to coordinate interlinking converters, photovoltaic generators, Energy Storage Systems and loads in a microgrid. The operation of the renewable power sources of a microgrid at the full generated power is desired due to economic and environmental reasons. The DBS technique proposed in this paper is adapted to integrate renewable power sources in the microgrid. The DBS-controlled Energy Storage Systems (ESS) will store the surplus energy if the generated power exceeds consumption. In the case of fully charged ESS, the renewable generators will limit their output power to those demanded by the loads. The proposed control laws have been tested in an experimental microgrid.
- PublicationA Control Scheme to Suppress Circulating Currents in Parallel-Connected Three-Phase Inverters(MDPI AG, 2022-11) Liberos Mascarell, María Antonia; González Medina, Raúl; Patrao Herrero, Iván; Garcerá Sanfeliú, Gabriel; Figueres Amorós, Emilio; Dpto. de Ingeniería Electrónica; Escuela Técnica Superior de Ingeniería del Diseño; Escuela Técnica Superior de Ingeniería Industrial; Grupo de Sistemas Electrónicos Industriales; AGENCIA ESTATAL DE INVESTIGACION; European Regional Development Fund[EN] The parallel operation of inverters has many benefits, such as modularity and redundancy. However, the parallel connection of inverters produces circulating currents that may result in malfunctions of the system. In this work, a control technique for the elimination of the low-frequency components of the circulating currents in grid-connected inverters is presented. The proposed control structure contains n - 1 zero-sequence control loops, with n being the number of inverters connected in parallel. Simulation and experimental results have been carried out on a prototype composed of two 5 kW inverters connected in parallel. The results have been obtained by considering the following mismatches between both inverters: inductance values of the grid filters, unbalance of the delivered power, and the use of different modulation techniques.
- PublicationAn Algorithm for Emulating Photovoltaic Strings With Dynamic Partial Shadowing Capability: A Practical Study(Institute of Electrical and Electronics Engineers, 2023-06) Patrao Herrero, Iván; González Medina, Raúl; Garcerá Sanfeliú, Gabriel; Figueres Amorós, Emilio; Dpto. de Ingeniería Electrónica; Escuela Técnica Superior de Ingeniería del Diseño; Escuela Técnica Superior de Ingeniería Industrial; Grupo de Sistemas Electrónicos Industriales; AGENCIA ESTATAL DE INVESTIGACION; European Regional Development Fund[EN] In photovoltaic (PV) systems, a maximum power point tracking (MPPT) algorithm is needed to maximize the energy obtained from the PV strings [1] , [2] . A bad tracking of the maximum power point (MPP) degrades the overall performance of the photovoltaic facilities [3] , [4] , [5] , [6] . The panels in a PV string may be working under different operating conditions of irradiance and temperature because of eventual shades produced by near obstacles, different orientation of modules or dusting, resulting in the partial shadowing phenomenon [7] , [8] .
- PublicationPerformance Evaluation of the B4 Topology for Implementing Grid-Connected Inverters in Microgrids(MDPI AG, 2024-05) Torán Mort, Enric; Liberos Mascarell, María Antonia; Patrao Herrero, Iván; González Medina, Raúl; Garcerá Sanfeliú, Gabriel; Figueres Amorós, Emilio; Dpto. de Ingeniería Electrónica; Escuela Técnica Superior de Ingeniería del Diseño; Escuela Técnica Superior de Ingeniería Industrial; Grupo de Sistemas Electrónicos Industriales; AGENCIA ESTATAL DE INVESTIGACION; Ministerio de Ciencia e Innovación[EN] The B4 topology is an interesting alternative to the conventional B6 inverter due to its reduced number of parts and lower cost. Although it has been widely used in the past, especially in low-power motor drive applications, its application as a grid-connected inverter is an open area of research. In this regard, this paper analyses the feasibility of the B4 inverter topology for grid-connected applications. A versatile 7 kW inverter prototype, which may be configured as B4 and B6, was built, allowing for a comprehensive evaluation of the performance of both topologies. Through an analytical study and experimental tests, the performance of the B4 and B6 topologies was comparatively evaluated in terms of efficiency, total harmonic distortion of line currents, current unbalance, cost, and mean time between failures. The study was carried out in the context of microgrid systems, highlighting their role in the integration of renewable energy and distributed generation.
- PublicationSmall-Signal Model of the NPC + GCC Multilevel Transformerless Inverter in Single-Phase Photovoltaic Power Systems(MDPI AG, 2023-09) Patrao Herrero, Iván; Liberos Mascarell, María Antonia; González Medina, Raúl; Torán Mort, Enric; Figueres Amorós, Emilio; Garcerá Sanfeliú, Gabriel; Dpto. de Ingeniería Electrónica; Escuela Técnica Superior de Ingeniería del Diseño; Escuela Técnica Superior de Ingeniería Industrial; Grupo de Sistemas Electrónicos Industriales; AGENCIA ESTATAL DE INVESTIGACION; European Regional Development Fund[EN] Photovoltaic transformerless inverters are very efficient and economical options for solar-power generation. The absence of the isolation transformer improves the converters' efficiency, but high-frequency voltage to ground can appear in the photovoltaic string poles. The high capacitance to ground of the photovoltaic generator leads to undesirable high-leakage currents. Using half-bridge topologies dramatically reduces the leakage to ground, and using a multilevel half-bridge inverters improves the output quality compared with classical inverters. The neutral point clamped + generation control circuit (NPC + GCC) topology is a multilevel single-phase transformerless inverter capable of tracking the maximum power point of two photovoltaic sources at the same time. This paper presents the control structure and the dynamic modeling of the NPC + GCC inverter. The pulse-width modulated (PWM) switch model in continuous conduction mode (CCM) was used to obtain the small-signal model of the two switching converters that make up the inverter. The resulting dynamic model was used to quantify the stability margins of both converters' current and voltage loops.