215 research outputs found

    An LVDC distribution system concept

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    An LVDC distribution system is a new innovation in a field of electricity distribution. This paper presents the basic principles to use power electronics devices in electricity distribution systems. Recent technological and economical developments in power electronic components enable to apply power electronics in LV network. This development makes an LVDC distribution system concept establishment possible. In this respect the occurring progression connects power electronics and distribution system development strongly together. The LVDC distribution system basic concept concentrates at DC/AC interface focusing on implementation of customer-end inverter. The previously made analyses have shown that presented LVDC distribution system has existing techno-economical potential in electricity distribution networks.reviewe

    PV inverters for module level applications

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    Dissertação para obtenção do Grau de Mestre em Energias Renováveis – Conversão Eléctrica e Utilização SustentáveisNowadays, the photovoltaic (PV) energy is presented as one of the most promising source of clean energy, and so a good way for greenhouse gas emissions mitigation and reduce the fossil fuel dependence. Within it, the photovoltaic energy has caused a huge interest in the electronic converters, and the need to improve their efficiency and reducing their cost. With this work I present a solution for a module scale grid-connected single-phase inverter. The solution consists in a two-stage inverter insolated with a grid line transformer. The two-stage inverter is composed by a DC-DC converter and a DC-AC converter connected through a DC-link capacitor. The DC-DC converter in case is a boost converter used to elevate the voltage from the PV module to a higher level. For the DC-AC converter it is used a full-bridge inverter, and both the DC-DC and the DC-AC converters use the IGBTs form an integrated module with its respective drivers. To the boost control it is implemented a Maximum Power Point Tracking algorithm that can optimize the power extraction from the PV source and for the inverter it is used a sliding mode hysteretic control. Once this inverter is conceived to work connected to the grid, a single-phase PLL system is used to synchronize the injected current to grid voltage. All the control part is made digitally using an Arduino Uno board, which uses an Atmel microcontroller

    A Multifunctional SiC DC-DC Converter Topology with Normalized Fault Detection Strategy for Electric Vehicle Applications

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    The automotive industry is experiencing a monumental shift in technology and propulsion strategies. More than ever before, car manufacturers and suppliers are shifting development and funding away from combustion engines in favor of electrified powertrains. One of the main obstacles contributing to customers reluctance to buy EVs is the lack of infrastructure for charging. Traditional 110/220VAC outlets equipped at residential buildings are relatively low power compared to the batteries used in EVs today. These AC chargers, classified as level 1 and level 2, will take approximately 12-24 hours to completely charge a battery, depending on battery size and state-of-charge. Additionally, because this method of charging uses alternating current, vehicles must have chargers on-board to convert the energy from AC to DC to recharge the battery because EV batteries are direct current energy sources. Millions of dollars from the government and private companies are being invested to create an adequate DC fast charging infrastructure. The advantages of DC charging are two-fold, much quicker charging times and the elimination of onboard chargers. However, there is one blatant problem with current investments into a DC charging infrastructure – technological advancement. Most electric vehicles in production have battery pack voltages between 300V and 400V and current DC fast chargers are being developed for the current technology. This will likely change rather quickly; the development of wide-bandgap devices will allow for higher voltage devices. Furthermore, the energy densities of batteries will also likely improve, allowing for higher bus voltages. Higher bus voltages will offer several advantages over current architectures – more power, smaller devices, improved efficiencies, and more. The problem is, once higher bus voltages are achieved and popularized, the current fast charging infrastructure will be deemed obsolete. An intermediate solution needs to be developed to allow higher bus voltage vehicles to continue to utilize the current fast chargers being deployed nation-wide. The proposed DC-DC converter is a practical design that offers multiple purposes when implemented in electric vehicles that utilize permanent magnet synchronous machines (PMSM) and bus voltages of ~800V. It consists of a bi-directional interleaved DC-DC cascaded with an isolated full bridge converter. This configuration provides a 12V source with galvanic isolation during normal propulsion. The interleaved converter can boost in reverse to allow for charging of the 800V bus with current generation DC fast chargers operating at ~400V. Finally, an inverter fault detection methodology has been realized to take advantage of the interleaved DC-DC structure. If an open switch fault is detected on any of the 3-phases driving the PMSM, the appropriate phase-leg is isolated, and a phase-leg from the interleaved DC-DC is used to maintain propulsion. This is realized by monitoring the phase currents of the AC motor and analyzing the difference in value between all three. A threshold value is implemented in C-code, not contingent on the system parameters. A difference of phase currents greater than the threshold value is a clear indication that an open switch fault has occurred. The proposed power conversion structure and the motor inverter fault detection, isolation, and compensation approaches are verified by a PSIM simulation. The simulation results successfully validate the feasibility of proposed electric powertrain structure and inverter switch fault detection and compensation methods.Master of Science in EngineeringEnergy Systems Engineering, College of Engineering & Computer ScienceUniversity of Michigan-Dearbornhttp://deepblue.lib.umich.edu/bitstream/2027.42/156398/1/Brandon Pieniozek Final Thesis.pdfDescription of Brandon Pieniozek Final Thesis.pdf : Thesi

    Off-Grid Inverter with Regulated Output Voltage Amplitude

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    The paper discusses the design, simulation, and implementation of a 60W, 115VAC, 60Hz off-grid power inverter. The off-grid inverter creates a mains-level voltage from a 12V lead-acid battery input without connection to a conventional electric grid. The inverter includes a low-voltage H-Bridge circuit that is controlled with 3-level Pulse Width Modulation (PWM), and uses a low frequency step up transformer from 12V to 115V. A feedback system based on IQ sampling and a Proportional, Integral, Derivative controller (PID) is implemented to maintain a constant output voltage amplitude over an input range of 10 to 15VDC. A microcontroller is used to generate PWM and implement the feedback loop. The inverter successfully powers small household loads such as a desktop fan and laptop

    Guest Editorial: Special Section on Smart DC Distribution Systems

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    Multi-technology battery storage system for optimal demand-side management

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    Demand-side management (DSM) provides additional system flexibility for the electric energy environment. To enable the spread of DSM policies the use of automatic systems combined with a local battery energy storage system (BESS) is proposed. Following this statement, it has been developed and tested a 50 kVA low-cost multi-technology energy storage system, with a novel converter topology that permits the integration of multiple battery types or aging. It consists of a 50 kVA bidirectional three-level AC/DC converter for grid connection which feeds five 10 kW isolated bi-directional DC/DC battery converters, based on SiC and Si MOSFETs. The development leads in a pick-and-place system, adding interoperability, ease of connection and modularity

    Factors Affecting Efficiency of LVDC Distribution Network – Power Electronics Perspective

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    The power distribution network will be changed towards the future Smart Grid due to increased number of installed renewable power generation units to fulfill the tightened environmental regulation. The control of the future Smart Grid will be challenging due to increased number of renewable power generation units, which are variable in nature, and at the same time, the customers are highly dependent on uninterruptable, high quality power supply. The Smart Grid control is intensively studied. It can be concluded that the control might be simpler and the grid operation more reliable if the AC grid would be replaced by DC grid. However, the detailed energy efficiency analysis of the DC grid is not thoroughly studied. The efficiency and total lifetime costs are the key parameters when the network owners consider the future grid structure.This thesis addresses the factors, which affect the energy efficiency of the low voltage DC (LVDC) distribution network from power electronics perspective. The power loss models for the converters and their AC filters are developed and verified by measurements. The impact on the converter topology, used power semiconductor switches, AC filter design and inductor core material, DC network configuration, customer behavior, the need of DC voltage balancing in the bipolar DC network as well as the grounding issues to fulfill the electrical safety standards are treated. For facilitating the design of cost effective LVDC distribution networks, the total power losses of the network with different configurations are evaluated and compared.It is revealed that the used filter inductor core material has a significant impact on the power losses of the LVDC distribution network. The inductor core material having low high-frequency power loss characteristics, such as amorphous alloy, is recommended. The LVDC distribution network should be grounded to minimize the power losses whenever it is possible according to the local safety standardization and grounding conditions. The three-level NPC converters connected to 1500 VDC should be used to minimize the power losses. The grid-frequency isolation transformer is the main power loss source if the galvanic isolation is needed to isolate the ungrounded LVDC distribution network and the grounded customer electrical installations. In this case, the highest energy efficiency is achieved by using two- or three-level converters connected to 750 VDC if the DC cable length is less than 600 m. Otherwise, slightly higher energy efficiency is achieved by using three-level converters connected to 1500 VDC. Therefore, voltage transformation ratio of the isolation transformer must be 800V/400V instead of 400V/400V. Moreover, the efficiency of the power converters is increased by using SiC MOSFETs instead of conventional IGBTs as power semiconductor switches

    Advanced Power Electronic Interfaces for Distributed Energy Systems Part 1: Systems and Topologies

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    Review of Electric Vehicle Charging Technologies, Configurations, and Architectures

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    Electric Vehicles (EVs) are projected to be one of the major contributors to energy transition in the global transportation due to their rapid expansion. The EVs will play a vital role in achieving a sustainable transportation system by reducing fossil fuel dependency and greenhouse gas (GHG) emissions. However, high level of EVs integration into the distribution grid has introduced many challenges for the power grid operation, safety, and network planning due to the increase in load demand, power quality impacts and power losses. An increasing fleet of electric mobility requires the advanced charging systems to enhance charging efficiency and utility grid support. Innovative EV charging technologies are obtaining much attention in recent research studies aimed at strengthening EV adoption while providing ancillary services. Therefore, analysis of the status of EV charging technologies is significant to accelerate EV adoption with advanced control strategies to discover a remedial solution for negative grid impacts, enhance desired charging efficiency and grid support. This paper presents a comprehensive review of the current deployment of EV charging systems, international standards, charging configurations, EV battery technologies, architecture of EV charging stations, and emerging technical challenges. The charging systems require a dedicated converter topology, a control strategy and international standards for charging and grid interconnection to ensure optimum operation and enhance grid support. An overview of different charging systems in terms of onboard and off-board chargers, AC-DC and DC-DC converter topologies, and AC and DC-based charging station architectures are evaluated
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