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Onload tap changers based on silicon-controlled rectifiers or triacs are widely used to regulate ac voltage. Response time is bigger than half-cycle due to the natural commutation used during the zero-current crossing. N. Burany proposed a commutation method for direct ac/ac matrix converters based on power transistors, or other switches with active turn-off, by permitting a freewheeling current path during commutation. This can be applicable to tap changers and release commutation from the zero-current crossing, thus allowing a faster voltage regulation. This paper presents a new two-tap chopped ac/ac voltage stabilizer with compensating transformer and PWM frequency in the order of S kHz based on this kind of commutation. The circuit proposed, resulted from a topology search guided by an iterative analysis+synthesis cost comparative method, fits well to low voltage stabilizers and regulators in the range of 0.1 to 1000 kVA and 1 ms response time. The switching behavior and the input and output filtering is fully analyzed. An exhaustive synthesis study follows, giving the component rates as a function of the equipment specification. This allows an easy equipment cost evaluation. Experimental results with IGBT switches are obtained in a 1 kVA prototype. [ABSTRACT FROM AUTHOR]

This paper presents a different Finite Control Set – Model Predictive Control (FCS-MPC) for grid-connected three-phase bidirectional power inverters. These are typically used in dc or ac renewable-based microgrids (MGs), where bidirectional operation and fast dynamic response is required. The bidirectional grid-connected inverters are an essential part of MG, which inject energy into the ac grid or demand energy from it. The dynamic behavior of the system is a major concern since the current can suddenly change depending on the hierarchical controller. This paper proposes a different cost function using sliding mode theory, which offers a good dynamic response, reduced computational burden, and a parameter-free control model. The operation principle of the proposed controller is given and evaluated using a Hardware-In-the-Loop (HIL) system, but also experimentally with a 1kW laboratory prototype. The final results demonstrate the advantages of using this approach in grid-connected three-phase bidirectional power inverters in terms of dynamic response and reduced computational burden, making this solution technically attractive and viable. [ABSTRACT FROM AUTHOR]

A single-phase common-mode transformerless grid-connected photovoltaic (PV) converter, which is based on the integration of two stages, is proposed in this paper. Transformer elimination in grid-connected PV systems has many advantages. It not only reduces cost, size, and weight but also increases the complete system efficiency. Since there is no galvanic isolation between grid and PV array, a leakage current may appear due to the PV parasitic capacitance to the ground, if this is not taken into account in the converter design. This paper presents a dc/dc boost converter integrated with a full-bridge inverter. The integration of these two stages reduces the ground leakage current. The neutral line of the grid is directly connected to the negative terminal of the PV array, eliminating any possibility of leakage current in this terminal. The principle of operation of the transformerless converter is analyzed, and a 200-W topology is experimentally tested. [ABSTRACT FROM PUBLISHER]

This paper presents a case study analyzing the advantages and disadvantages of using project-based learning (PBL) combined with collaborative learning (CL) and industry best practices, integrated with information communication technologies, open-source software, and open-source hardware tools, in a specialized microcontroller and embedded systems engineering Master's course. In addition to addressing industry requirements in both contents and methodology, the course develops capabilities and competencies in problem solving, independent learning, teamwork, and technical knowledge. Since PBL methodology alone does not ensure teamwork, it was complemented with CL. Design review meetings (as described in IEC 61160), deliverables, and organizational resources were also introduced to mirror industry demands. This structure integrated course content and student academic achievement in a simulated industrial environment. The course had students build a modular management system for home appliances, implementing control software on the “Arduino” open-source platform, as well as using wireless communications. The results show that teaching, learning, and student assessment processes can be improved by using PBL with CL. In addition, the introduction of industry practices, such us peer review meetings, brings academia closer to a real-world context. [ABSTRACT FROM AUTHOR]

Photovoltaic (PV) electricity is widely used because of its positive environmental impact. To properly feed this energy into the grid, an electronic power converter, known as a PV inverter, is needed, which may or may not use a transformer. This article details the analysis and design of a transformerless photovoltaic inverter topology for grid-connected applications. This converter offers high efficiency, a low number of elements, and negligible leakage current, which makes it a good alternative for this application. The converter has been validated through an experimental prototype and compared with other topologies with similar characteristics. [ABSTRACT FROM AUTHOR]

Firefighter's interventions under dense smoke and flames are hazardous and ideally need an efficient in-advance geo-located actuation plan. The existing communication and sensing technologies should be customized, optimized, and integrated to better know the conditions (flame locations, air condition) before and during the rescue team's interventions. In this paper, we propose a firefighter intervention architecture, which consists of several sensing devices (flame detectors, carbon dioxide air content) a navigation platform (an autonomous ground wheeled robot), and a communication/localization network (BLE IoT network) that can be used before and during an intervention in rescue or fire extinguishing missions even for indoor or confined spaces. The paper's key novelty presents our integrated solution, giving some key implementation details and an intensive experimentation campaign in two real firefighter scenarios with real controlled fires. Results carried out in these real indoor scenarios are presented to demonstrate the feasibility of the system. A fire detection system is proposed to improve fire focus in real time and moving in confined spaces with no visibility and physical references. The results obtained in the experimentation show the proposal's effectiveness in locating the fire focus's position and orientation reducing time and risk exposure. This kind of location-aware fire integrated systems would significantly impact the speed and security of first responder interventions. [ABSTRACT FROM AUTHOR]

Low power grid-tied photovoltaic (PV) generation systems increasingly use transformerless inverters. The elimination of the transformer allows smaller, lighter and cheaper systems, and improves the total efficiency. However, a leakage current may appear, flowing from the grid to the PV panels through the existing parasitic capacitance between them, since there is no galvanic isolation. As a result, electromagnetic interferences and security issues arise. This paper presents a novel transformerless single-phase Current Source Inverter (CSI) topology with a reduced inductor, compared to conventional CSIs. This topology directly connects the neutral line of the grid to the negative terminal of the PV system, referred as common mode configuration, eliminating this way, theoretically, the possibility of any leakage current through this terminal. The switches control is based on a hysteresis current controller together with a combinational logic circuitry and it is implemented in a digital platform based on National Instruments Technology. Results that validate the proposal, based on both simulations and tests of a low voltage low power prototype, are presented. [ABSTRACT FROM AUTHOR]