Power Electronic Components Research Articles

A switch-source cell-based cascaded multilevel inverter topology with minimum number of power electronics components

Multilevel inverters are a new generation of DC–AC converters at medium and high voltage and power levels. In this paper, a new single-phase cascaded multilevel inverter is presented. For this purpose, a new basic cell is presented at first. Then, the new multilevel inverter structure is yielded by series connection of these cells. The proposed new cell is only capable of generating positive voltage levels, and therefore, to produce zero and negative voltage levels, the proposed structure is constructed based on H-bridge module. In order to reduce the maximum blocking voltage especially on H-bridge switches, the cascaded connection of the proposed converter is investigated. A comprehensive comparison is carried out between the proposed multilevel inverter with the classical and recently introduced structures in terms of the number of switching devices, the number of drivers, the total blocking voltage of the switches as well as the loss and efficiency. The accuracy of the proposed inverter’s performance is simulated in MATLAB/Simulink in symmetric and asymmetric topologies for a 17-level and 23-level output voltage respectively, and then evaluated by the laboratory prototype.

Effects of alternating current on Li-ion battery performance: Monitoring degradative processes with in-situ characterization techniques

With the rapidly growing markets for electric vehicles and renewable energy systems, the complex duty cycles imposed by electric machines and power electronics components are now a common feature of battery service. As a result, lithium-ion, increasingly the battery of choice, must cope with superimposed alternating current (AC) across a broad range of frequencies. To advance understanding of how AC may influence the ageing of Li-ion batteries (LIBs), this work uses electrochemical impedance spectroscopy to investigate the interaction of AC with key aspects of LIB operation (charge-transfer, properties of the solid electrolyte interphase, and lithium-ion diffusion), along with analysis of capacity performance to quantify the main modes of degradation. For a set of fresh LiFePO4 cells, subjected to nearly 200 days of service, comparison of DC profile with coupled DC + AC duty reveals that high-frequency superimposed AC does not contribute to ageing, with some evidence that it can actually enhance the battery life. In contrast, low-frequency superimposed AC accelerates both loss of lithium inventory and loss of active material (as the most pertinent degradation modes of LIBs) and consequently induces greater capacity loss. This important correlation between AC frequency and extent of degradation was confirmed in AC-only studies, which showed that the voltage polarization induced by AC perturbation is the key indicator of any likely effect. These findings can serve as a guide for deciding whether a given combination of frequencies and amplitudes is likely to have an adverse impact.

Eight‐switch CHB‐based three‐level three‐phase shunt active power filter

This study presents a reduced switch three-phase three-level H-Bridge-based shunt active power filter (SAPF) for the mitigation of current harmonics, the reduction of current unbalance and the injection of reactive power. This recommended SAPF is developed by using two H-bridge and two DC-link capacitors. Compared to the conventional three-level H Bridge-based SAPF, the eight-switch cascaded H bridge (ES-CHB)-based topology saves four semiconductor switches and one DC-link capacitor. The ES-CHB-based SAPF saves the power electronic components and reduces voltage stress across each switch by introducing a small AC capacitor in series with coupling inductor in each phase. This LC circuit also reduces the harmonic stress of SAPF by tuning at the sixth order of current harmonics. The only drawback of the suggested SAPF is the DC link voltage unbalances. To address this problem, a modified feedback control strategy is proposed in this study. The modified controller regulates the DC link voltage at the desired voltage and mitigates the DC link voltage unbalances, by using reactive power flow control and active power flow control, respectively. The performance of the suggested eight-switch three-level CHB-based SAPF is evaluated through MATLAB simulation and experimentally verified through the hardware implementation.

Power Electronics Reliability: State of the Art and Outlook

This article aims to provide an update of the reliability aspects of research on power electronic components and hardware systems. It introduces the latest advances in the understanding of failure mechanisms, testing methods, accumulated damage modeling, and mission-profile-based reliability prediction. Component-level examples (e.g., Si IGBT modules, SiC MOSFETs, GaN devices, capacitors, and magnetic components) are used for illustration purposes in addition to system-level studies. The limitations and associated open questions are discussed to identify future research opportunities in power electronics reliability.

Reliability of Power Electronic Systems for EV/HEV Applications

The electrification of the transportation sector is moving on at a fast pace. All car manufacturers have strong programs to electrify their car fleet to fulfill the demands of society and customers by offering carbon-neutral technologies to bring goods and persons from one location to another. Power electronics technology is, in this evolution, essential and also in a rapid development technology-wise. Some of the introduced technologies are quite mature, and the systems designed must have high reliability as they can be quite complicated from an electrical perspective. Therefore, this article focuses on the reliability of the used power electronic systems applied in electric vehicles (EVs) and hybrid EVs (HEVs). It introduces the reliability requirements and challenges given for the power electronics applied in EV/HEV applications. Then, the advances in power electronic components to address the reliability challenges are introduced as they individually contribute to the overall system reliability. The reliability-oriented design methodology is also discussed, including two examples: an EV onboard charger and the drive train inverter. Finally, an outlook in terms of research opportunities in power electronics reliability related to EV/HEVs is provided. It can be concluded that many topics are already well handled in terms of reliability, but issues related to complete new technology introduction are important to keep the focus on.

Distributed power management with adaptive scheduling horizons for more electric aircraft

A more electric aircraft is expected to have low emissions, decreased fuel consumption, high efficiency, and low maintenance costs. To fully enjoy those benefits, major technical obstacles must be overcome first. In terms of power management, an increasing number of power electronic components used in aircraft power systems and their ever-increasing functional sophistication will lead to high modeling and computational complexities, making real-time power management a daunting challenge. To address this challenge, in this paper we will first propose a novel architecture for real-time power scheduling, which allows a user to easily incorporate fault diagnosis, stability analysis and power scheduling together, and then present a locally tactical power scheduling strategy based on a Lagrangian relaxation, which allows a user to adopt different computation techniques to undertake local computations within sub-systems in parallel to ensure good scalability of the distributed strategy. Moreover, the power scheduling is calculated based on an adaptive scheduling horizon to further reduce the computational complexity. Simulations are carried out to illustrate the effectiveness of our proposed distributed architecture, in particular, the optimality of the solution and the balanced computational complexity.

Distributed Energy Resources and the Application of AI, IoT, and Blockchain in Smart Grids

Smart grid (SG), an evolving concept in the modern power infrastructure, enables the two-way flow of electricity and data between the peers within the electricity system networks (ESN) and its clusters. The self-healing capabilities of SG allow the peers to become active partakers in ESN. In general, the SG is intended to replace the fossil fuel-rich conventional grid with the distributed energy resources (DER) and pools numerous existing and emerging know-hows like information and digital communications technologies together to manage countless operations. With this, the SG will able to “detect, react, and pro-act” to changes in usage and address multiple issues, thereby ensuring timely grid operations. However, the “detect, react, and pro-act” features in DER-based SG can only be accomplished at the fullest level with the use of technologies like Artificial Intelligence (AI), the Internet of Things (IoT), and the Blockchain (BC). The techniques associated with AI include fuzzy logic, knowledge-based systems, and neural networks. They have brought advances in controlling DER-based SG. The IoT and BC have also enabled various services like data sensing, data storage, secured, transparent, and traceable digital transactions among ESN peers and its clusters. These promising technologies have gone through fast technological evolution in the past decade, and their applications have increased rapidly in ESN. Hence, this study discusses the SG and applications of AI, IoT, and BC. First, a comprehensive survey of the DER, power electronics components and their control, electric vehicles (EVs) as load components, and communication and cybersecurity issues are carried out. Second, the role played by AI-based analytics, IoT components along with energy internet architecture, and the BC assistance in improving SG services are thoroughly discussed. This study revealed that AI, IoT, and BC provide automated services to peers by monitoring real-time information about the ESN, thereby enhancing reliability, availability, resilience, stability, security, and sustainability.

Stand Alone 1 MW Microgrid for Remote locations of Armed Forces with PV Battery Diesel Generator

Many times, Armed Forces are deployed in bases in remote areas on the borders or Islands, which are far flung areas away from mainland. In many such cases, these areas do not have their power requirements through the main grid supply and entire power requirement of the deployment is supplied by diesel generators. These diesel generators have high environmental impact due to emission of greenhouse gases and are highly uneconomical as logistic sustenance of remote bases for supply of fuel is very challenging, Fossil fuel has to be supplied by vehicles, helicopters, boats or manually carried to hill tops. This increases the overall cost of deploying armed forces in remote areas. In recent years with the advancements in power electronic components and renewable energy, development in Microgrids (MGs) have shown a way to reduce dependency on main power grids. Hence, with the help of MGs, renewable energy can be used to fulfill power requirements of the armed forces deployed in remote places. In this work, a MG with capacity of 1MW has been designed keeping the special needs of armed forces as a major consideration. Solar power has been used as a primary renewable energy source in the proposed design. In order to mitigate the adverse effects of meteorological and extreme conditions on the solar power generation capacity, energy storage system in the form of batteries has also been provided. Batteries store power when excess power is generated from the photo voltaic (PV) system and discharge the power when power demand is higher than the PV generated power. Diesel generator sets have also been used to run critical loads, provide reliability and as backup to critical operations catering for outages, night time needs and un-expected meteorological conditions. MATLAB has been used to design and simulate the proposed MG. Working of the MG has also been demonstrated for varying meteorological and varying load conditions as well. The proposed design works satisfactory in all cases.

A multi-method control strategy for numerically testing a fuel cell-battery-supercapacitor tramway

A fuel cell-battery-supercapacitor powertrain, for railways, is investigated and numerically modelled. Each main powertrain component, such as energy sources, power electronic and drivetrain components, is analysed in detail; electrochemical, logic and physic equations are used to design the models, formalizing and implementing them in Matlab-Simulink. To achieve a proper behaviour and high performance, two control strategies are implemented: an ad-hoc power-sharing system, designed for railways, that connects principles of global drive-cycle knowledge and real-time methods; a motor control, composed of a proportional-integral speed and a direct torque control. Therefore, the controllers can take advantage of the powertrain component peculiarities, selecting a proper role for each energy source, and accurately manage the electric motor. The fuel cell-based powertrain is tested on a real urban route, offering a public service from/to the University of Calabria. The simulation results are investigated on different levels of details: a meticulous energy efficiency and performance analysis is conducted. The output power and hydrogen consumption (approximately 0.3 kg/km) are examined and losses and efficiencies of each component are evaluated, reaching 42.5% overall vehicle efficiency, in order to study the energy flux and form conclusive considerations regarding the pros and cons of fuel cell hybrid systems for railways.

Reducing Environmental Impacts through a Smart Design of Microgrids: Life Cycle Assessment for AC and DC

Microgrids with integrated renewable energies show promising potentials in terms of reliable, efficient, and clean smart grid concepts. Further improvements are expected when such a microgrid is operated on a direct current instead of an alternating one. Our study aims to systemically analyze the environmental impacts of microgrids operating on ac and on dc using power distribution within office buildings as an example. For this purpose, a comparative and scalable life cycle assessment is conducted based on a technical bottom up analysis of differences between ac and dc microgrids. Particularly, our approach combines the assessment of required power electronic components on a micro-level using a generic grid model on a macro-level. The results indicate that the environmental impacts of employed power electronics can be substantially reduced when utilizing a microgrid operating on dc instead of ac.

A new generalized cascade multilevel converter topology and its improved modulation technique

SummaryIn this paper, a basic unit for the nine‐level converter is firstly presented. Then, a new developed basic unit topology for the multilevel converter is proposed. This topology comprises several bidirectional and unidirectional switches along with dc voltage sources. In order to increase the number of generated levels, a cascade topology based on the series connection of developed basic units is studied. Due to the extensive nature of the presented cascade multilevel converter, the optimization analysis is presented for generating the maximum number of levels with minimum numbers of IGBTs, drivers, dc voltage sources, and voltage on switches. All required mathematical analysis consisting of switching losses, conduction losses, and voltage on switches is illustrated. In order to indicate the merits of the proposed multilevel converter, comparison results are provided. It is shown that the presented topology uses the least numbers of power electronic components. Also, the voltage on the switches in the presented cascade topology is low. For controlling the switches, a modified triangular carrier signal for dual pulse generation is proposed. The performance of the proposed multilevel converter is proven with experimental results of a typical 25‐level converter.

Noise-Source Model for Frequency-Domain EMI Simulation of a Single-Phased Power Circuit

In recent years, power electronic converters have been downsized significantly by high-density packaging techniques. As a result, parasitic couplings between power electronic components have become larger. For the prediction of electromagnetic interference (EMI) noise considering such couplings, a 3-D electromagnetic simulation is more suitable than a circuit simulation using a huge number of parasitic models. The most-practical electromagnetic simulation method is the finite element method, which is based on a frequency domain. The switching noise must be modeled in the frequency domain for an EMI noise simulation. In this article, we propose a new noise-source model for a frequency-domain EMI noise simulation. We modeled a transistor and a freewheeling diode by voltage and current sources based on three model topologies: transistor-OFF-diode-ON topology (OFF-topology); transistor-ON-diode-OFF topology (ON-topology); and transistor-on-diode-ON topology (recovery topology). We also used OFF-topology to simulate the turn-OFF EMI noise as caused by the turning-OFF of a transistor. Meanwhile, we used a combination of ON-topology and recovery topology to simulate the turn-ON EMI noise including recovery noise as caused by the turning-ON of a transistor. After introducing the details of the model, we compared the measured and simulated results so as to show the validity of the model.

An advanced virtual synchronous generator control technique for frequency regulation of grid-connected PV system

The future power system is developing to an inverter-based system from a machine dominated power system due to a large integration of renewable energy sources (RESs). Lack of inertial part and intermittency of the RESs causes frequency instability in the power system. The virtual synchronous generator (VSG) development has been made to add inertial control to the power system for controlling the frequency deviation caused by the integration of the photovoltaic system. The VSG system comprised of power electronics components having a droop control mechanism like the conventional synchronous generator, which provides the necessary frequency stability to the power system. In this paper, three parallel VSG based photovoltaic systems integrated with battery storage systems are used to analyze the frequency response and its stability. Moreover, an advanced genetic algorithm optimization method is used to get the optimal values of parameters of the droop controller used in VSG. Furthermore, two different cases with respect to variation in supply and load power of the system are analyzed in detail. Additionally, an IEEE 14 bus system is utilized to validate the proposed system in MATLAB/Simulink. Evident improvements are observed in the simulation results presented through the suggested GA based VSG control technique.

Optimal design of a cascaded rectangular‐type and circle‐type multilevel inverters with a new switching technique

Multilevel inverters (MLIs) are extensively used in industrial and renewable energy applications. They are a promising solution for the effective transformation of dc to ac. Researchers are developing auspicious topologies to mitigate the use of an output filter, which reduces cost and complexity. Hence, it is necessary to develop a topology that is capable of increasing output voltage levels with an optimum number of power electronic components. However, in developed topologies, a large number of switches, gate driver circuits, and dc sources are used. To solve this problem, a new MLI structure is introduced. The proposed structure is cascaded to form cascaded rectangular-type and circle-type topologies capable of engendering maximum output voltage levels and incorporating an optimum number of switches, gate driver circuits, and dc-sources. Moreover, conventional switching techniques have become more complex, while generating a staircase output contains a large number of levels. Therefore, this study proposes a novel switching technique that is easy to implement in MLIs with large output voltage levels. To show the competency of the proposed topology, a comprehensive comparison is performed with various structures. At the end of this study, validation of the proposed switching technique and topology is verified by simulations and experimentations.

Design and Application Analysis of Intelligent Low-voltage Switchgear Based on Internet of Things

Low-voltage switchgear is a key control device in the power distribution network, which integrates a large number of lines and power electronic components. Once a failure occurs, it will cause serious economic losses. With the continuous upgrade and expansion of the power system construction scale, the traditional low-voltage switchgear can no longer meet the requirements in terms of function or performance, and is replaced by a new type of intelligent switchgear. This paper designs an intelligent low-voltage switchgear based on the Internet of Things, real-time monitoring of temperature and key electrical parameters, and improves the reliability and maintainability of the switchgear.

Extraction of Dynamic Frequency Response Characteristics and Modelling of Modern Air Conditioners

Modern inverter-based air-conditioners (IACs) are generally equipped with power-electronic components to achieve higher efficiency and more advanced controllability. Thus, their operating behaviours can be very different from the conventional air-conditioners with direct motor connections, and their new characteristics have not been adequately studied in the current literature. Thus, hardware experiments are conducted to extract the novel dynamic frequency response features of modern inverter-based air-conditioners under a range of different frequency disturbances. Then, a new IAC model with physical meanings is developed by accommodating the discovered new features such as time delays, load frequency relief and the minimum operating power limit. Further, this letter also demonstrates that the developed air-conditioner model can accurately represent the dynamics of the IACs under various frequency events. The extracted dynamic frequency response behaviours and the developed air-conditioner model will provide a solid foundation for the modern appliance modelling in a large scale and will assist to improve the accuracy of the inertia response representations of distribution network's loads.

Improvement of Effectiveness of Cooling of Electronic Heat-Loaded Modules

There has been developed, manufactured, and researched by numerical and experimental methods an operating sample of a typical construction of a cooling system of electronic heat-loaded modules of dual application, which can be used in devices of both special and civil purposes. The main idea of organizing an effective cooling is to provide heat transfer from a heat-loaded module, located in conditions where it is impossible to provide the thermal regime necessary for trouble-free operation, to an area where it is possible to organize the dissipation of the transported heat flow through free convection. A gravity-assisted heat pipe with a threaded capillary structure was used as a heat transfer device. As heat-loaded modules there were used powerful volumetric electronic modules made in the form of a prism with flat side faces, on which powerful semiconductor electronic components were installed. Due to application of a highly efficient closed evaporation-condensation cycle of heat transfer occurred in heat pipes, it became possible to increase the power of the electronic module in almost two times while keeping its temperature within the specified limits., graphical dependences of the temperature of semiconductor electronic components on the consumed electric power in the range from 13 to 36 W were obtained by using a calculation method. The experimental data were compared with those obtained due to the calculation.

Advanced Laboratory Testing Methods Using Real-Time Simulation and Hardware-in-the-Loop Techniques: A Survey of Smart Grid International Research Facility Network Activities

The integration of smart grid technologies in interconnected power system networks presents multiple challenges for the power industry and the scientific community. To address these challenges, researchers are creating new methods for the validation of: control, interoperability, reliability of Internet of Things systems, distributed energy resources, modern power equipment for applications covering power system stability, operation, control, and cybersecurity. Novel methods for laboratory testing of electrical power systems incorporate novel simulation techniques spanning real-time simulation, Power Hardware-in-the-Loop, Controller Hardware-in-the-Loop, Power System-in-the-Loop, and co-simulation technologies. These methods directly support the acceleration of electrical systems and power electronics component research by validating technological solutions in high-fidelity environments. In this paper, members of the Survey of Smart Grid International Research Facility Network task on Advanced Laboratory Testing Methods present a review of methods, test procedures, studies, and experiences employing advanced laboratory techniques for validation of range of research and development prototypes and novel power system solutions.

Fault current limiter for the MMC‐based multi‐terminal DC grids

In the modular multilevel converter (MMC)-based multi-terminal high-voltage direct current (HVDC) system, the fault current rises rapidly due to sub-module capacitors discharging when a DC-side short-circuit fault occurs, which makes the MMC easily blocked for self-protection. To avoid the blocking of the converter station and lower the DC fault current, this study proposes a novel fault current limiter (FCL) for MMC-based multi-terminal DC grids. First, the fault current limiting circuit, which consists of resistance, capacitance and power electronic components is designed. Then, the operation principle of the FCL is analysed in detail. Afterwards, the startup criterion is constructed, and the selection method of the key parameters in the fault current limiting circuit is also introduced in order to prevent the converter station from blocking in the case of DC short-circuit fault. Finally, a simulation model was built using PSCAD/EMTDC software, and extensive simulation results verified the effectiveness of the proposed FCL.

Simplification of Thermal Networks for Magnetic Components in Space Power Electronics

The volume of magnetic components for space applications, directly related to the launch cost, and their performance are critically influenced by their capability to dissipate the internal electromagnetic power losses. This is the reason why accurate thermal models are required. Furthermore, these models need to be simple and versatile to allow a fast analysis of many different designs. In this study, a specific methodology to analyze inductors and transformers by thermal networks and a simplification based on the Thevenin’s theorem leading to a simple equation are proposed. The specific details to address thermal modelling for space magnetic components are discussed. A generic 50 W Flyback transformer for space applications is analyzed in this study and experimental validation is provided, showing that the proposed method leads to a deviation in the temperature estimation between 1 °C and 5 °C, which is considered quite a good result from the literature review carried out.