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The dual-active bridge (DAB) topology is commonly preferred in bidirectional applications due to several attractive features, including auto-adjust of power flow, galvanic insulation, wide voltage gain, and zero voltage switching (ZVS) capability over some power ranges. However, the efficiency of the converter drops at light loads because the ZVS range is directly dependent on the circulating current. Assuming that the processed power is variable, the DAB converter's design must find a compromise between extending ZVS ranges and reducing the reactive power processing to ensure higher efficiency. Aiming this compromise, many papers propose hybrid approaches in which the modulation strategy is selected according to the processed power. However, this is not a simple solution because it demands multivariable control and offline optimizations. This paper proposes a modulation strategy to ensure ZVS and reduce the circulating current for the DAB converters. While the usual phase-shift modulation provides ZVS operation in a range of 40% to 100% of rated power, the proposed asymmetrical pulse-width modulation can obtain ZVS operation in a range of 2% to 100% of rated power. Experimental results demonstrated that the proposed strategy improves the converter efficiency for all power ranges, especially at light loads. [ABSTRACT FROM AUTHOR]

Demanding higher power, higher power quality, lower switching loss, and eliminating interface transformers in industrial applications caused significant attention toward multilevel converters. This paper presents current control of a seven-level topology for medium-voltage high-power applications. This topology has fewer active switches and components, and less control complexity in comparison to the other existing classic and advanced seven-level topologies. A comprehensive review has been done on seven-level topologies to demonstrate the advantages of this topology in this paper. A control method based on model predictive control (MPC) is developed to balance the flying capacitors of this topology at their desired values and control the output currents without the need of pulsewidth modulation blocks, and proportional-integral (PI) controllers, which is the advantage of MPC in power electronics applications. In order to evaluate the performance of the seven-level topology and the developed control method effectiveness, experimental results are shown for different conditions, which demonstrate the feasibility of the seven-level topology and the developed control technique. [ABSTRACT FROM AUTHOR]

In this paper, the modeling of storage elements and a unified theory liberated of the I–V characteristics of a specific technology is developed. First, the definition of an ideal storage element with limited energy capacity is presented, then the semiideal storage properties are discussed. The addition of power conservative two-port network denoted POPI (Pout = Pin) is added in order to define a flexible storage element in terms of characteristics. The paper demonstrates the theory by examples of storage elements integrated in power electronics systems. The ideas and methodology presented in this work can be applied to power electronics applications as well as power systems, smart grids, and microgrids, where storage is an important factor. [ABSTRACT FROM AUTHOR]

To meet the great need for distributed and sustainable power sources, mechanical energy in the environment is widely used for electricity generation. Based on the coupling effect of triboelectrification and electrostatic induction, triboelectric nanogenerator (TENG) as an innovative energy technology has advantages of collecting fluctuating amplitude and low-frequency mechanical energy. In this paper, a leaf-shaped TENG has been demonstrated to harvest multiple ambient mechanical energy. By the characterization with different mechanical energy sources, the leaf-shaped TENG has been proven as an effective tool to scavenge wind, vibration, and falling raindrop energy. Furthermore, based on numerous leaf-shaped TENGs, a leaf-shaped TENG tree has been developed, which can be used for continuous collection of environmental mechanical energy at large-scale. This paper has first exhibited a conformal structure for simultaneously harvesting various mechanical energy, which has bright potentials in environmental monitoring, Internet of things, and wireless sensor networks. [ABSTRACT FROM AUTHOR]

Multi-objective optimization of power converters is a time-consuming task, especially when multiple operating points and multiple converter topologies must be considered. As a result, various steps are often taken to simplify the design problem and restrict the size of the design space prior to going through an optimization procedure. While this saves time, it produces potentially sub-optimal designs, and existing approaches must tradeoff between running time and design optimality. This paper presents an optimization-oriented method for modeling power converters and their components as posynomial functions, allowing multi-objective optimization of converters to be formulated as a geometric program, a type of convex optimization problem. This allows the use of fast, powerful solvers that guarantee global optimality of solutions. The method is demonstrated using the example of low-power multi-level flying capacitor step-down converters. Results show that, using geometric programming, sets of globally Pareto-optimal designs of two-, three-, and four-level converters with respect to efficiency and power density, for one design space and one operating point, can be generated in as little as 25 s, on a mid- to upper range laptop computer. Thus, optimal designs for three different converter topologies for hundreds of different operating points and/or design spaces can be generated in several hours—less than the time required to globally optimize one converter topology at one operating point for one design space using currently prevalent methods. This paper also demonstrates how geometric programming can be used to quickly perform sensitivity and tradeoff analysis of optimal converter designs. [ABSTRACT FROM AUTHOR]

In this paper, state-of-the-art power electronics and energy management solutions utilized in low-power (less than 5 mW), low-voltage (less than 3 V) energy harvesting powered wireless sensors for Internet of things related applications are detailed. All aspects of an energy harvesting powered sensor system are examined, including the challenges of low-power energy harvesting sources, energy management circuits including power converters and energy storage elements, as well as the impact of wireless sensor pulsed power profiles. In particular, this paper focuses on existing voltage step-up energy management techniques, including the issues of cold-start and maximum power point tracking, as well as energy storage which is necessary for wireless sensor operation. Both academic and commercially available energy harvesting powered systems are examined to provide a comprehensive analysis of existing solutions. Issues that are limiting the current system performance are identified to help define future developments needed to enable efficient and effective energy harvesting powered wireless sensor operation. [ABSTRACT FROM AUTHOR]

In a dual active bridge (DAB) dc–dc converter, modulating the phase-shift ratios can suppress reactive power and increase the efficiency under non-unity voltage gain conditions. Derivation of the optimal phase-shift ratios to achieve the minimum reactive power is challenging because a DAB can operate in four different scenarios (forward/backward, buck/boost) and each scenario has five operating modes. This paper first introduces a transformation in which different DAB operating scenarios (forward/backward, buck/boost) can be equivalent to one another; then optimization of only one scenario (forward/buck) is required. Next, for the five modes in forward/buck scenario, based on a graphical method, this paper proves that each operating point of Modes 1, 2, and 5 can be mapped into that of Mode 3 with lower conduction losses, and only two modes require detailed analysis. The optimization process of these two modes are derived step-by-step. Global optimal phase-shift signals that minimize the reactive power under four different DAB operating scenarios (forward/backward, buck/boost) are presented. A simple table and control block diagram are presented for practical implementation of global reactive-power minimization control. Experimental comparison with other modulation schemes verifies the efficiency improvement of the proposed control method. [ABSTRACT FROM AUTHOR]

Multilevel inverters (MLIs) are being used in wide range of power electronic applications. These converters have attracted a lot of attention during recent years and exist in different topologies with similar basic concepts. This paper presents five main submodules (SMs) to be used as the basic structures of MLIs. The paper reviews the common MLI topologies from the structural point of view. The topologies are divided into the different SMs to show conventional MLI configurations and future topologies that can be created from the main SMs. A comparative study between different topologies is performed in detail. The MLIs are categorized and investigated with from different perspectives such as the number of components, the ability to create inherent negative voltage, working in regeneration mode and using single dc source. [ABSTRACT FROM AUTHOR]

This paper presents a unified physics-based insulated-gate bipolar transistor (IGBT) compact model for circuit simulation that predicts the performance of both Si and SiC, n- and p-channel devices. The model can predict the detailed switching waveforms of these technologies based on its charge-based formulation. Further, this compact IGBT model is presented alongside a unique datasheet-driven parameter extraction process. The parameter extraction process enables users to quickly extract model parameters from data typically published without the need of taking physical measurements. The model has been validated with both Si and SiC devices for static and dynamic characteristics. The SiC IGBTs used for validation are a 12.5-kV n-channel device and a 13-kV p-channel device, while the Si IGBT chosen was IXDH30N120 from IXYS Corp. (Milpitas, CA, USA). This is the only IGBT model that predicts the performance of both n- and p-channel, Si and SiC devices, providing more freedom for the development of complex power electronics circuit designs. The convergence of the model has been verified by implementing a complex circuit consisting of both a dc–dc converter and a dc–ac inverter. The results presented here show that the unified model can be used to describe the behavior of a wide range of Si and SiC IGBT circuits. This paper is accompanied by a Verilog-A source code and a power point file demonstrating the model parameter extraction sequence. [ABSTRACT FROM AUTHOR]

This paper proposes a methodology for active thermal control of power electronic modules in ac applications, which includes a loss manipulation unit, a thermal observer structure, and an active thermal cycle reduction algorithm. It aims to reduce the thermo-mechanical strain in the inter-connects of the module in order to enhance its reliability and lifetime. The loss manipulation unit operates in a minimally invasive manner by manipulating adaptive gate resistances and the pulsewidth modulation frequency. This allows the individual thermal control of multiple devices within a power module, which has not been achieved in prior work. A thermal observer structure that estimates averaged junction temperatures by combination of a thermal model and sensor information is introduced. The observer technology makes this paper the first to realize closed-loop control of averaged temperatures achieving an increased robustness and insensitivity to modeling errors. A key element of the active thermal cycle reduction algorithm is the virtual heat sink that derives feasible and stress-relieving thermal trajectories. The trajectories are applied with a unique thermal feedback control that smoothly manipulates the averaged junction temperature of the power module even in the presence of loss manipulation limits. The active thermal control methodology is evaluated experimentally with a state-of-the-art insulated-gate bipolar transistor (IGBT) power module. [ABSTRACT FROM AUTHOR]

In modern power systems, the increasing penetration of renewables and power electronics, particularly inverter-based wind and solar power generation, is altering power system dynamics and bringing new stability concerns. One challenging issue that is attracting considerable attention is the wide range of power oscillations associated with multiple parallel grid-connected inverters. In such systems, the characteristics in terms of resonance and oscillation are significantly different from single-inverter systems. This paper investigates the mutual interaction and stability issues of multiple grid-interfacing inverters with LCL-filters in power-electronics-based power systems under various grid conditions. The investigation reveals that such interactions between power inverters and the grid may excite multiple resonances at various frequencies under certain grid conditions. The nodal admittance matrix concept, which was originally from power systems engineering, is adopted here. Moreover, this paper further develops an Interaction-Admittance model that can effectively describe these mutual interactions in terms of a physical network admittance. We apply our model to various scenarios such as stiff grid conditions and inductive grids with/without power factor correction capacitors. The results with the proposed framework demonstrate an intuitive interpretation of multi-inverter system resonance and instabilities. Finally, simulations and experiments on a lab-scale system are provided to verify the theoretical analysis. [ABSTRACT FROM AUTHOR]

System identification is fundamental in many recent state-of-the-art developments in power electronic such as modeling, parameter tracking, estimation, self-tuning and adaptive control, health monitoring, and fault detection. Therefore, this paper presents a comprehensive review of parametric, non-parametric, and dual hybrid system identification for dc–dc switch mode power converter (SMPC) applications. The paper outlines the key challenges inherent with system identification for power electronic applications; speed of estimation, computational complexity, estimation accuracy, tracking capability, and robustness to disturbances and time-varying systems. Based on the literature in the field, modern solutions to these challenges are discussed in detail. Furthermore, this paper reviews and discusses the various applications of system identification for SMPCs; including health monitoring and fault detection. [ABSTRACT FROM AUTHOR]

A high-efficiency three-dimensionally (3-D) shaped polymer multi-jet impingement cooler based on cost-efficient fabrication techniques is introduced for the cooling of high-power applications. State-of-the-art highly efficient multi-jet cooling solutions rely on expensive Si or ceramic fabrication techniques, while low-cost cooling solutions have been proposed for less performant single-jet impingement. In this paper, we present the concept, modeling, design, fabrication, experimental characterization, and benchmarking with literature data of a multi-jet impingement based liquid cooling solution, fabricated using low-cost polymer fabrication techniques, targeted to directly cool the backside of high-power devices. For the modeling study, unit cell model and full system level models are used to study the nozzle array scaling trends and thermal and fluidic jet-to-jet interactions. Furthermore, design guidelines for high-power electronics cooling are provided, including geometry selections, material selection, and fabrication techniques. Based on the design guidelines and cooling concept, this paper demonstrates a 3-D-shaped polymer impingement cooler with a 4 × 4 nozzle array, showing a very good thermal performance with low required pumping power. The multi-jet cooler can achieve heat transfer coefficients up to 6.25 × 104 W/m2·K with a pump power as low as 0.3 W. The benchmarking study confirms furthermore that multi-jet cooling is more efficient than single-jet cooling and that direct cooling on the backside of the semiconductor device is more efficient than cooling the substrate or base plate. [ABSTRACT FROM AUTHOR]

This paper discusses various types of failure mechanisms, precursor parameters, and accelerated aging-based procedures to estimate the remaining life of power electronic devices. Special attention has been given to summarize the different techniques typically used for measuring the junction temperature, because it plays a vital role during accelerated aging and condition monitoring. We reviewed more than 250 papers, and the references list 139 of them in order to explain and address the advantages and disadvantages of various techniques toward the reliability prognosis. Thus, this paper can be considered as an expedient reference to conduct future research on lifetime prediction of existing power electronic devices. [ABSTRACT FROM AUTHOR]

This paper proposes a novel dc power electronic transformer (DCPET) topology for locomotive, ac/dc hybrid grid, dc distribution grid, and other isolated medium-voltage and high-power applications. Compared with conventional PET topology, the proposed DCPET has fewer power semiconductor devices and high-frequency isolation transformers, which can improve the power density and reliability. Fault handling or redundancy design can be achieved to further improve the reliability when some dc–dc modules break down. Also, input voltage sharing control can be omitted to simplify the control system and improve the stability. Meanwhile, soft switching is guaranteed for all the switches, which is beneficial to increase switching frequency and improve power density. In this paper, the principle, evolution, and control of the proposed DCPET are respectively presented and studied in detail. Finally, a prototype of the proposed DCPET is built and the experimental results verify the validity and superiority of the proposed topology. [ABSTRACT FROM AUTHOR]

The doubly fed induction machine has been traditionally adopted in adjustable-speed ac power generation drives in order to take advantage of the reduced rating for the power electronic interface. Aside this well-established application where the doubly fed induction generator (DFIG) is controlled by a back-to-back converter, recent literature records a growing interest toward un-conventional DFIG drives for dc power generation, combining DFIG high control freedom with simplified power electronic interfaces to achieve an overall cheap and fully controllable system. Despite several concepts have been demonstrated on small-scale rigs, there is a lack of systematic comparison among different topologies and control solutions. This paper bridges this gap by providing a review of recent topologies, their control, design and performance, and operation issues. As major novelties, this paper includes off-spec performance comparison of different torque-ripple mitigation strategies, discussion of sizing requirements for generator and power electronics, fundamental aspects of the behavior under voltage dips, and priorities and challenges for future research on the subject. [ABSTRACT FROM AUTHOR]

Power converters and electric motor drives when tightly regulated behave as constant power loads. These loads are different from resistive loads and have destabilizing negative impedance characteristics, which impact a system's stability. A boost converter is intrinsically nonlinear and is a nonminimum phase system at the output voltage with respect to the control input. The linear approximation of this boost converter loaded with a constant power load has a zero and poles in the right half of the $s$ -plane, making the system unstable and very difficult to control. Control techniques that employ some form of system inversion cannot be implemented for a nonminimum phase system. This paper describes a technique to modify the nonminimum phase boost converter to a minimum phase for a constant power load, further implementing the input–output linearization technique to stabilize the system. This paper also provides a methodological analysis of the problem followed by the proposed solution. Furthermore, it verifies the analysis of the proposed solution through simulation and experimental results. [ABSTRACT FROM AUTHOR]

This paper investigates the possibility of deploying a finite control set model predictive control (FCS-MPC) algorithm for dynamic stabilization of a dc microgrid (MG) that supplies tightly regulated point-of-load (POL) converters. Within their control bandwidth, such converters behave as constant power loads (CPLs), where the MG sees them as impedances with a negative incremental resistance. Due to this characteristic, POL converters have a destabilizing impact that may cause large voltage oscillations or even a blackout of the whole MG. This paper proposes an active damping method realized by introducing a stabilization term in the cost function of the FCS-MPC algorithm that is used for regulation of the POL converter. This approach, on one hand, stabilizes a dc MG without implementing any additional active or passive components; thus, providing higher energy efficiency and better cost-effectiveness than methods that rely on such components. On the other hand, when compared to other approaches that focus on dc link stabilization via POL converter control, the proposed method has a significantly lower influence on the load voltage regulation performance. These findings are confirmed through comprehensive analytical investigation that shows how the proposed stabilization term affects the input impedance of the POL converter and the load voltage tracking performance. This is followed by experimental validation, where an FCS-MPC regulated uninterruptible power system inverter was used as a particular CPL example. [ABSTRACT FROM AUTHOR]

This paper presents a study on the gate driver circuitries that need to be implemented to drive several power devices when associated in series connection. More specifically, the propagation paths of parasitic currents through the gate driver circuitries, exited under high switching speeds, are studied in different configurations trying to minimize common mode currents generated. In a gate driver circuitry for a regular low side–high side switching cell configuration with one upper switch and one lower switch, the voltage transient dv/dt at the middle point applied across the primary-secondary parasitic capacitance of gate driver supplies, and control signal isolation units are the reasons for the generation of conducted electromagnetic interference (EMI) perturbations. In complex power converters, multicell, multilevel, or even series connection of power devices, many driver circuits are required and implemented. Similarly, in such converters, there are several dv/dt sources generated at different floating points producing conducted EMI perturbations from the power part to the control part through many gate driver circuitries. Based on previous works, this paper analyzes the best configuration to minimize parasitic currents, especially reducing the conducted common mode currents in series connected transistors topologies. Simulations and practical results validate the analysis for two power devices in series connection, and then the extrapolations for more power devices in series connection, up to six are discussed and analyzed with the help of simulations results. [ABSTRACT FROM AUTHOR]

Multiple coupled inductors are used in power electronics to improve the dynamic cross regulation and to reduce mass and volume, mainly in high performance application, such as space or defense, where manufacturing cost is not the main driver. These elements can be modeled with its inductance matrix which is a symmetric and positive semidefinite matrix. The inductance matrix eases circuit analysis, many known circuital models are directly related to it and it can be used in SPICE simulation via its coupling coefficient component, which can be identified as the normalized matrix of the inductance matrix. Therefore, a precise and correct measurement technique of the inductance matrix or coupling coefficient matrix is needed. This paper analyzes different measuring techniques described in the technical literature and proposes a new method to measure the coupling coefficient or inductance matrix of tight coupled or dissimilar turns’ number windings, where other methods fail. A discussion follows, to know the influence of parasitic elements in the accuracy of the new proposed method called resonance (RE) method. The paper adds three experimental examples to verify the theoretical study and concludes that the RE method provides correct values of the coupling coefficient $k$ of tight coupled or dissimilar turns’ number windings compared to other measurement techniques. [ABSTRACT FROM AUTHOR]

This paper presents a novel platform for accurate mathematical modeling of the propulsion system of electric cars. It provides, for the first time, a hardware-in-the-loop (HIL) real-time experimental verification case study of a General Motor Chevrolet Volt for power, control systems, and the mechanical systems. The contribution of this paper can be categorized into three approaches: First, each component of the powertrain is accurately modeled taking transient dynamics of all components of the electric vehicle into consideration. Further, a PSIM simulation platform is consequently developed to demonstrate the validity of this mathematical modeling. Finally, the Typhoon HIL is used to provide the experimental verification of the proposed model in real time, which precisely validates the viability of the model. HIL technology is used to prototype and test the proposed control system while simulating the power circuit on the HIL module platform. The permanent magnet synchronous motor and the power electronics hardware components are simulated in real time at which the parameters can be changed during the simulation. However, the control algorithm is generated as a C code and downloaded to the TI controller that exists on a digital signal processing board. The results from the simulation based on PSIM environment and hardware validations using HIL are in agreement, which validates the developed model. The performance has been investigated under different load operating conditions in real time to verify its robustness. The case study can be extended for any electric car as it provides a generic platform for modeling any propulsion system. [ABSTRACT FROM AUTHOR]

This paper presents an inverter topology named the multi-source inverter that aims to connect several independent DC sources to the same AC output using a single stage of conversion. This power converter has been developed for applications, such as electrified powertrains. Compared to the conventional hybrid powertrains that use a DC/DC converter to provide an adaptable voltage to the load, the multi-source inverter can drive a traction motor from variable DC voltages without the use of an additional power converter. Hence, the high power DC/DC converter can be dissociated from the traction mode and its use will be restricted to the engine $^{\prime }$ s start-up and regenerative braking, allowing a significant reduction of its power rating from tens of kWatts to a few kWatts. The overall efficiency of the electrified traction drive can also be improved due to the single conversion stage between the battery and the motor. In this paper, the multi-source inverter topology is introduced and its different operating modes are determined through the study of the inverter circuit. Closed-loop control simulations and experiments with a scaled-down prototype and an induction motor were performed to validate the effectiveness of the proposed topology and concept. [ABSTRACT FROM AUTHOR]

This paper proposes a hybrid electronic and magnetic structure named a variable-inverter-rectifier-transformer (VIRT) that enables a transformer with fractional and reconfigurable effective turns ratios (e.g., 12:0.5, 12:2/3, 12:1, and 12:2). This functionality is valuable in converters with wide operating voltage ranges and high step-up/down, as it offers a means to reduce the turns count and copper loss within the transformer while also facilitating voltage doubling and quadrupling. These properties are especially beneficial for miniaturizing the transformer stage in many power electronics applications, such as universal serial bus wall chargers. We introduce the principle of operation of the structure and present models for its magnetic and electrical behavior. The instance of VIRT described in this paper comprises four half-bridge switching cells distributed around a planar magnetic core and connected to two “half-turns” wound through that core. By controlling the operating modes of the half-bridge cells, we gain control over the flux paths and current paths used in the transformer, and this hybridization enables fractional and reconfigurable effective turns ratios. An experimental prototype integrates the VIRT with a stacked-bridge LLC converter to accommodate a widely varying input (120–380 \textV\text{dc}) and output (5–20 \textV\text{dc}), and VIRT is shown to be highly beneficial in keeping efficiency high over this wide output voltage range. [ABSTRACT FROM AUTHOR]

Constant on-time V^2 control for point-of-load buck converters has instability issues in the cases that the output capacitors' RC time constants are small. This paper intensively studies the proposed solution using capacitor current ramp compensation, which is a superior solution featuring fast response and universality. A frequency-domain small-signal model based on describing function method is proposed in this paper. The time-domain large-signal response to the load step change is analyzed. The analysis illustrates the unique transient response behaviors of the capacitor current ramp compensated V^2 control. The design optimization methodology based on frequency-domain and time-domain analysis is presented. The proposed model and the design guidelines are verified by the experimental results. [ABSTRACT FROM AUTHOR]

The output voltage of power electronic converters is a very important quantity for dynamic control of power electronic systems. In electrical drives without electromechanical position or speed sensor, the terminal reference voltage is used to obtain the rotor position. Dead-time effects and semiconductor voltage drop lead to distortion in the actual output voltage and degrade the control performance when the back electromotive force magnitude is low. Thus, for stable low-speed operation, output voltage sensing becomes necessary. Due to the switching nature of power electronic systems, this is not a trivial task, especially when instantaneous measurement of the terminal voltage is required. In this paper, an instantaneous switching-period average voltage sensing technique is proposed that utilizes a combined approach of oversampling and filtering. Based on the theoretical analysis of the sampling- and filter-induced measurement distortion, a general solution for an optimal filter design is derived. The additional sensing circuit is integrated into the low-side gate driver of the converter outputs. This paper includes details about the hardware implementation and extensive verification measurements. [ABSTRACT FROM AUTHOR]

In this paper, we demonstrate how latency insertion method (LIM) can be used for real-time simulation of high switching frequency power electronics systems and how this approach can be implemented for scalable Field Programmable Gate Array (FPGA) execution. We first present a summary of the LIM and how this method can be developed into a solver for high-performance FPGA execution. We then present how common power electronics topologies—buck and boost—can be modeled using the LIM approach, followed by how the LIM model of a three-phase dc/ac converter is created. Afterward, we demonstrate the accuracy of the developed FPGA solver through a set of power electronic system examples, with each example compared with near ideal results of same example provided by a traditional electromagnetic transient type solver. We complete the paper analyzing the scalability of the proposed approach on FPGA devices, both in terms of achievable time step as well as of resource usage. [ABSTRACT FROM AUTHOR]

In power electronics, the $\ell _1$-norm (instead of the squared $\ell _2$-norm) is often used in the objective function of model predictive controllers (MPCs) with reference tracking. Although the $\ell _1$-norm is preferred for its computational simplicity, it might lead to a performance deterioration and closed-loop instability. This paper analyzes the root cause for this and discusses the benefits of using the $\ell _2$-norm instead. Given the theoretical nature of this paper, a power electronics-oriented case study is employed to visualize and exemplify—through examples and simulations—the mathematical concepts and arguments presented. To this end, a variable speed drive system with a three-level voltage-source inverter serves as an illustrative example to clearly demonstrate the effectiveness of using the $\ell _2$-norm. [ABSTRACT FROM AUTHOR]

Silicon carbide (SiC) devices enable more compact and efficient design of applications such as traction inverters and rectifiers. With miniaturization of power electronics, the volume and weight of heatsink or cold plate occupies a significant portion. So, thermal design, especially power loss evaluation, is crucial to the whole system. Analytical switching model based on datasheet parameters is usually adopted to evaluate devices’ switching loss due to its convenience. However, when applied on SiC metal-oxide-semiconductor field-effect-transistors (mosfets), turn-on waveforms of conventional analytical switching model show obvious discrepancy from experiments at both current rising and voltage falling stages. The transfer and capacitance characteristics from datasheet are responsible for that. Due to short channel effect and drain-induced barrier lowering, transfer characteristic during turn on period varies with different drain-to-source voltage vds. Cgd during actual turn on period is also different from that on the datasheet. So, considering the actual turn on process, dynamic transfer characteristic and Qgd are proposed and measured in this paper. After these modifications, switching-on waveforms of the analytical switching loss model match the experiments very well, and error of the estimated loss is less than 5%. [ABSTRACT FROM AUTHOR]

Water treatment is one of the most important issues for all walks of life around the world. Different from the conventional water treatment technology, the advanced power electronic pulse technology has unique features and advantages for the modern water treatment. Unfortunately, there is no literature reported to describe them in a comprehensive and systematic way. To fill this gap, an overview of modern power electronic pulse generators (PPGs) for water treatment is presented. This article, for the first time, classifies the different types of PPGs from the viewpoint of pulse formation. Each of them is discussed, and the advantages and disadvantages are compared and summarized. Aside from that, this article presents the development and trend of the pulse generators suitable for the specified water treatment processes such as electrolysis, sterilization, and discharge degradation. Finally, a list of more than 100 relevant technical papers is also appended for a quick reference. [ABSTRACT FROM AUTHOR]

Peak-current-mode (PCM) control was published first time in open literature in 1976. The observed peculiar behavior caused by the application of PCM control in a power electronic converter have fascinated the researchers to attempting to capture the dynamics associated to it. It is commonly assumed that the peculiar phenomena originate from the sampling process in the PCM control. A resistor is usually connected as a load, when modeling the converter dynamics and during the frequency-response measurements. The load resistor will actually dominate the frequency responses and hide the real dynamics associated to PCM control. Other measurement problems will arise from the nonmodeled circuit elements dominating, especially, the high-frequency dynamic behavior of the converters. As a consequence of these problems, the PCM models are not usually properly validated. The investigations, in this paper, show the following: 1) the PCM models have to be accurate also at the low frequencies for ensuring, for example, stable design of output-current-feedback-controlled converters; 2) the high low-frequency accuracy can be obtained only by means of duty-ratio gain becoming infinite at the mode limit; 3) the high-frequency accuracy of the PCM models can be obtained by means of different high-frequency extensions; 4) the key for the PCM modeling lies in the proper duty-ratio constraints; and 5) the high-frequency magnitude and phase behaviors are caused by the second-harmonic-mode operation of the converter due to the frequency-response-measurement injection signal. The main objective of this paper is to show that such a modeling technique, which fully matches the aforementioned criteria, has been developed already in early 1990s and later elaborated for more a general form. Validation of the dynamic models is performed by simulation, where the converter and its operational environment are perfectly known. The load-resistor effect is removed computationally for performing the complete validation. A PCM-controlled buck converter is used as an example. [ABSTRACT FROM AUTHOR]

This paper presents a novel six-pulse low-frequency (LF) fluctuating high-voltage dc-bus-based power system architecture for fuel cell vehicles (FCVs) application. A novel hybrid modulation scheme consisting of six-pulse modulation at LF scale and modified secondary modulation and 33% pulse width modulation at high-frequency (HF) scale is proposed. Three-phase ac waveforms for the propulsion system of FCVs are generated from LF fluctuating high-voltage dc bus. The proposed modulation technique significantly reduces the switching losses of the bidirectional dual-stage inverter: 1) soft-switching of both sides of the front-end current-fed full-bridge converter is realized; and 2) at any moment, only one leg of back-end three-phase inverter is switched at HF, while the other two legs are kept in on or off states. This tremendously reduces the bidirectional inverter's switching losses and improves the system efficiency. The LF fluctuating high-voltage dc bus allows the elimination of large electrolytic dc-link capacitor, which contributes to a more reliable and compact design. This paper presents the operation, analysis, and design of a bidirectional inverter implementing the proposed hybrid modulation technique. Simulation results obtained from power electronics simulation software PSIM and experimental results from the lab prototype clearly validate the effectiveness of the proposed modulation technique. [ABSTRACT FROM PUBLISHER]

This paper presents a comprehensive analysis about bus bar design procedure. Some applications in terms of rated power and shape are investigated regarding their particular requirements and challenges. The dc-link capacitor selection is one of the first and most important steps. It not only dictates the bus bar complexity but also is the key to accomplish a high-power density prototype. Current density and distribution is discussed in this paper based on simulation results. Moreover, the effects of stray inductance and capacitance are explained along with the dc-link capacitors and power semiconductor devices. Simulated results are compared with measurements by a high precision impedance analyzer, which shows the reliability of 3-D modeling-based designs. [ABSTRACT FROM PUBLISHER]

In this paper, a voltage balance control strategy based on dual active bridge (DAB) dc/dc converters in a power electronic traction transformer (PETT) is proposed. Based on this strategy, the output-parallel DAB converters can be equivalent to an input-series-output-parallel system. Furthermore, a PETT starting control method is put forward, which can effectively avoid risks of overcurrent and overvoltage in the PETT starting process. In order to carry out the controller design and system stability analysis, three different kinds of mathematical models of DAB converters are set up. The first model is related to a single DAB converter, the second model reflects the equivalent relation between an output-parallel DAB system and a single DAB converter in terms of the output-voltage control loop, and the third model indicates that the voltage balance control system based on DAB converters is a multiinput-multioutput system. Due to the nonzero off-diagonal elements of the controlled plant, there is a mutual effect between different control loops, which is defined as “interaction” in the multivariable feedback control theory. The stability of the voltage balance control system is made up of two parts, including the stability of each single-input-single-output (SISO) control loop and the influence of the interaction on the system stability. The research is carried out to measure the intensity of the interaction in this paper, and a criterion directly based on the controlled plant is proposed to predict the influence of the interaction, which can obviously simplify the system stability analysis. Considering the particular traction onboard application, a new control structure toward the voltage balance controller is introduced. Based on the new structure, the controller is designed and the stability of the SISO system is analyzed. Finally, a five-cell PETT prototype with rated power of 30 kW is taken to carry out further research, and the experiment results verify the effectiveness and correctness of the proposed algorithms. [ABSTRACT FROM AUTHOR]

The thermal stress of power electronic components is one of the most important causes of their failure. Proper thermal management plays an important role for more reliable and cost-effective energy conversion. As one of the most vulnerable and expensive components, power semiconductor components are the focus of this paper. Possible approaches to control the semiconductor junction temperature are discussed in this paper, along with the implementation in several emerging applications. The modification of the control variables at different levels (modulation, control, and system) to alter the loss generation or distribution is analyzed. Some of the control solutions presented in the literature, which showed experimentally that the thermal stress can be effectively reduced, are reviewed in detail. These results are often mission-profile dependent and the controller needs to be tuned to reach the desired cost-benefit tradeoff. This paper analyzes also the many open questions of this research area. Among them, it is worth highlighting that a verification of the actual lifetime extension is still missing. [ABSTRACT FROM PUBLISHER]

This paper analyzes two fault-tolerant dual-multiphase motor drives, a series-connected topology, and a standard H-bridge topology. Previous studies have shown that the series connected topology is appropriate to an aerospace application and has lower peak current in degraded mode in comparison with the H-bridge topology, which may consequently diminish the system's weight and cost. This paper extends the study to compare different control strategies of these structures under two fault conditions: short-circuit of an inverter's switch and an open-phase of the machine. The control strategies analyzed in this paper do not impact the fundamental current or the torque generation, but the amplitudes of some harmonics in degraded mode are expected to be narrowed down in order to reduce the inverter's size. Some analyses of maximum voltage and peak current in degraded mode have been used for inverter dimensioning. Experimental results are shown and compared to the simulated ones to confirm the validity of this study. [ABSTRACT FROM PUBLISHER]

The subject of this paper falls under the development of power electronics for more electric aircraft systems. The study concerns the design of a converter whose function is to generate a 300-V dc bus from a standard 28-V dc avionic network. Various systems, such as motor drives, need to be connected to the 28-V dc network. Their design could be simplified significantly, and standardized, by introducing this intermediate 28–300-V stage. The step-up converter in the proposed configuration is integrated as a part of the system. The power specification is 10 kW, which leads to very high-current values on the 28-V side. The choice of the converter topology, therefore, needs to match this central constraint. The proposed converter uses six boost cells, associated to constitute a series–parallel architecture. This arrangement leads to significantly more optimal sizing for high step-up ratios than conventional boost-cell configurations. Cell interconnection is implemented by means of a monolithic InterCell transformer to reduce the weight of the magnetic part. This paper describes the topology, design, and construction of the lab prototype, as well as experimental results obtained during testing. [ABSTRACT FROM PUBLISHER]

The unified knowledge on power converter design and manufacturing technology establishes a powerful tool, where the cost and topology realization can be analyzed simultaneously. This paper collects the design practice and cost estimation of various components in a power electronics converter and unites that to a choice of the assembling and manufacturing processes and resulting cost of the complete converter. The outcome of this work specifies the power converter at predefined power level and cooling condition and demonstrates the cost drivers of the complete unit depending on production volumes. As a case study, the cost of an inverter for a full electric or hybrid vehicle application is estimated and the results are compared with figures available in the literature, yielding the conclusion that the validity of such figures is highly dependent on production volumes and power levels. The essence of this paper is a set of general, reliable, and fast design models and production charts, in accordance with realistic cost estimates for the sake of system optimization and development of cost effective electric drives from small series to large volumes. [ABSTRACT FROM AUTHOR]

This paper proposes a new-type Tan-Sun coordinate transformation system, which is an extended version of Clarke coordinate transformation system. The main purpose of the proposed coordinate transformation system is to convert three-phase unbalanced alternating-current quantities into two orthogonal alternating-current quantities with equal amplitudes, and further into two direct-current quantities without second harmonic components through Park transformation method. By applying Tan-Sun coordinate transformation system to three-phase unbalanced converters, we can realize the direct-current decoupling of the three-phase unbalanced currents in the direct-quadrature synchronous rotating coordinate system, so the control methods developed for three-phase converters under balanced voltage conditions can be migrated into those under unbalanced voltage conditions directly. Three-phase unbalanced phase-locked loop technique and active and reactive power definition and calculation for three-phase unbalanced power systems based on Tan-Sun coordinate transformation system are also proposed in this paper. The comparison between Tan-Sun coordinate transformation system and the traditional coordinate transformation system under unbalanced voltage conditions both from the aspects of theory analysis and simulation and experimental verification is provided, and these results indicate the superiority of Tan-Sun coordinate transformation system. [ABSTRACT FROM PUBLISHER]

This part of the paper illustrates the use of the expression derived in Part I for predicting subharmonic oscillation in switching regulators. Six case studies with different control schemes from the recent literature are used to validate the novel approach and the new derived expression, which is benchmarked for these case studies against results obtained using the discrete-time modeling approach or Floquet theory combined with Filippov method. Numerical simulations from the circuit-level switched models, implemented in PSIM software, are used to demonstrate the correctness of the derived closed-form condition. A procedure is presented to apply the approach of the paper to power converters with nonlinear sources, such as photovoltaic (PV) arrays or fuel cells. Experimental measurements from a boost converter prototype for PV applications are also provided to validate the theoretical predictions and the numerical simulations showing a remarkable agreement. [ABSTRACT FROM AUTHOR]

Battery energy storage system based on the modular multilevel converter (MMC-BESS) is able to realize the decentralized management of battery packs, which is suitable for the retired battery utilization to improve the efficiency of battery recycling. With multiple submodules (SM), the corresponding SM fault ride-through method is mandatory to improve operational reliability. This paper proposes a redistributed pulsewidth modulation method for MMC-BESS to ride-through the SM fault through employing the simple logic operation, which could avoid the unexpected carrier shift under various modulation indexes induced by the SM fault or grid voltage rise. MATLAB simulations and experimental results are presented to verify the performance of the proposed method. [ABSTRACT FROM AUTHOR]

Nine-switch converter (NSC) has been presented as a dual-output converter with common frequency (CF) or different frequency (DF) operation modes. This paper proposes a novel space-vector modulation (SVM) method for the NSC that supports both the CF and DF modes. This method is based on the simplification of the space-vector diagram of NSC into that of six-switch converter, and the SVM method for NSC can be done like conventional SSC. The proposed voltage vector selection method without using common logical xor operation and the calculation method for dwelling times of voltage vectors are described in detail. In addition, the modulation indices for two ac terminals of NSC have been analyzed deeply, and the derived fitting equations can guide engineering application. The performance of the proposed SVM is verified by the simulation and experimental results, and the low total harmonic distortions and harmonic components for phase currents prove the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

Asymmetrical CLLC-type dc transformers (ACLLC-type DCTs) are becoming more and more popular in the renewable energy system, thanks to the bidirectional power transmission (PT), high power density, and low-cost sensorless open-loop control. Nevertheless, the resonant frequency is not constant due to variations of the operation power and temperature in practice, which may make DCT lose its required voltage conversion gain and deteriorate the PT ability. This poses a challenge on the design of circuit parameters, especially when the open-loop scheme is usually recommended for the ACLLC-type DCT in the renewable energy system. Therefore, a semi-artificial intelligence (semi-AI)-based simplified parameter design approach is put forward in this paper for ACLLC-type DCT. It replaces all unknown parameters with two intermediate parameters through certain manipulations, and then utilizes a very simple computer-assisted procedure to optimally design the parameters of the ACLLC-type DCT. In addition, a detailed design example with a special planar transformer is presented via the aid of ANSYS Maxwell to achieve the desired resonant parameters of the ACLLC-type DCT. Finally, the proposed semi-AI-based method is experimentally demonstrated in a real renewable energy system prototype. [ABSTRACT FROM AUTHOR]

The phase-shifted-carrier (PSC) technique is preferred for multilevel converters in medium-voltage applications with low submodule (SM) number. This technique can elevate the equivalent switching frequency resulting in low total harmonic distortions. However, for half-/full-bridge hybrid modular multilevel converter (MMC) with boosted modulation index, the conventional PSC method is invalid due to the asymmetric voltage reference wave. The SM capacitor voltages deviate from the rated value and harmonics below equivalent switching frequency appear in the arm and equivalent ac voltages. This paper introduces an improved PSC technique with a capacitor sorting algorithm to overcome this problem. The negative part of the reference wave is turned over and then multiplied by a correction factor. The angular displacement for triangular carriers between the upper and lower arms is determined by the parity of the half-bridge number per arm. With the proposed method, the capacitor voltages are balanced and the ac voltage of MMC has the lowest harmonic distortion. Double-Fourier analysis for the proposed technique is carried out, and harmonic characteristics are revealed. The experimental results validate the correctness and feasibility of the improved PSC technique for hybrid MMC with boosted modulation index and asymmetric reference wave. [ABSTRACT FROM AUTHOR]

For stable and efficient drives of interior permanent-magnet synchronous machines (IPMSMs), stator flux should be observed across a wide speed range. However, distortions such as a dc offset and low-order harmonics are contained in the estimated flux due to various reasons. In this paper, a distortion-minimizing flux observer is proposed to suppress the effects of dc offset and harmonics by implementing frequency-adaptive observers. The proposed frequency-adaptive flux observer is designed to extract a fundamental flux while keeping a simple structure even if the rotating speed of the IPMSM varies. The fundamental flux could be estimated by the proposed current- and voltage-model based flux observer, which is implemented with the frequency-adaptive observer and harmonic extractors. Moreover, parameter sensitivity and model transition are discussed to improve the performance of the proposed observers. The validity and effectiveness of the proposed methods are verified with simulation and experimental results. [ABSTRACT FROM AUTHOR]

Capacitive dc-links are widely used in voltage source converters for power balance, voltage ripple limitation, and short-term energy storage. A typical solution, which uses aluminum electrolytic capacitors for such applications, is assumed to be one of the weakest links in power electronic systems, therefore, also becoming one of the lifetime bottlenecks of power electronic systems. Various passive and active capacitive dc-link solutions have been proposed intending to improve the reliability of the dc-links qualitatively, making great effort to diverting the instantaneous pulsating power into extra reliable storage components. In this paper, a generic topology derivation method for single-phase power converters with active capacitive dc-link integrated has been proposed, which can derive all existing topologies, and identify a few new topologies. According to the synthesis results, the main achievements in research on capacitive dc-link solutions are reviewed and presented chronologically as well as thematically ordered. Furthermore, the reliability-oriented design procedure is applied to size the chip area of active switching devices and the passive components to fulfill a specific lifetime target and system specification, as well as compare the overall capacitive energy storage, energy buffer ratio, and the cost of different solutions. The cost comparisons are performed with a scalable lifetime target and power rating. It reveals that different conclusions can be drawn with different lifetime targets in terms of cost-effectiveness. [ABSTRACT FROM AUTHOR]

This paper proposes a new modulation strategy with balanced power device currents for the full-bridge three-level dc/dc converter. The proposed modulation strategy has two working patterns, which cannot only realize zero-voltage switching (ZVS) but also satisfy the wide input voltage range. More significantly, the two working patterns of the proposed strategy can balance the currents both among the power switches and clamping diodes in comparison with the conventional control strategies which cause current imbalances among the power switches and clamping diodes. Consequently, the proposed strategy can balance the thermal stresses among the power switches and clamping diodes, which would, thus, improve the converter's reliability. Finally, the experimental results, obtained using a built 1.5-kW experimental prototype, verify almost zero current difference and zero thermal-stress difference among the inner power switches, outer power switches, and clamping diodes under the proposed strategy. [ABSTRACT FROM AUTHOR]

This paper deals with near magnetic field characterization of power electronic modules. The purpose is to relate near-field (NF) measurement to switching behavioral characteristics. An elementary magnetic sensor is presented and its characterization is detailed. Isolated antenna simulations are computed, thanks to an equivalent lumped parameter model of the antenna. Experimental characterizations are also provided to be compared to simulations. Following that, the characterized antenna is integrated into a specific power electronic device. NF measurements allow us to compute magnetic field mappings of the device under test. Time and frequency analyses of the sensor output data are discussed based on current measurements and magnetic simulation of the power electronic device. Finally, NF measurement enables access to switching details, disturbance propagation paths, and radiation distribution of a power electronic module. [ABSTRACT FROM AUTHOR]

In the flexible dc grid, the dc fault propagates extremely fast. It requires the dc protection and the dc circuit breaker (DCCB) can identify and isolate the fault line very quickly, for the healthy network ride-through, especially in the multi-terminal dc grids. However, the existing protection and DCCB techniques for flexible dc grid can still not match the dc fault propagation speed. Therefore, a novel current-commutation-based fault current limiter (FCL) is proposed in this paper. It can limit the dc fault current effectively, to guarantee the converter continuous operation and healthy network ride-through after dc faults, so the requirement on the protection and DCCB acting speed can be decreased. Compared with the existing fault current limiting methods, the proposed FCL has tiny negative influence on the system transient response speed, operation stability, and DCCB isolating speed. The experiment tests and simulation case studies are carried out to verify the working principle and superiorities of the proposed novel FCL.3 [ABSTRACT FROM AUTHOR]

Three-phase power factor correction rectifiers are an essential area of power electronics, supplying a direct current load with tens of kilowatts, or more, from the public three-phase mains and achieving sinusoidal input currents. In many applications, isolation is required between the mains and the load, for example, due to safety reasons or different grounding schemes. This paper describes the modulation, design, and realization of a buck–boost-type, unity-power-factor, isolated matrix-type, dual-active-bridge, three-phase rectifier. It uses a circuit similar to a conventional dual-active-bridge converter, but employs a direct matrix converter to connect the high-frequency transformer's primary winding to the mains. A soft-switching modulation scheme is proposed and comprehensively analyzed, deriving closed-form solutions and numerical optimization problems to calculate switching times that achieve minimal conduction losses. Based on this analysis, the design of an 8-kW 400-V rms three-phase ac to 400-V dc prototype is discussed, striving for the highest possible efficiency. Using 900-V SiC mosfets and a transformer with an integrated inductor, a power density of ${\text{4}}\; {\text{kW}\cdot \text{dm}^{-3}}$ (${\text{66}}\; {\text{W}\cdot \text{in}^{-3}}$) is achieved. Measurement results confirm an ultrahigh full-power efficiency of 99.0% at nominal operating conditions and 98.7% at 10% lower input voltage. [ABSTRACT FROM AUTHOR]

Rooftop and building-integrated distributed photovoltaic (PV) systems are emerging as key technologies for smart building applications. This paper presents the design methodology, mathematical analysis, simulation study, and experimental validation of a digital twin approach for fault diagnosis. We develop a digital twin that estimates the measurable characteristic outputs of a PV energy conversion unit (PVECU) in real time. The PVECU constitutes a PV source and a source-level power converter. The fault diagnosis is performed by generating and evaluating an error residual vector, which is the difference between the estimated and measured outputs. A PV panel-level power converter prototype is built to demonstrate how the sensing, processing, and actuation capabilities of the converter can enable effective fault diagnosis in real time. The experimental results show detection and identification of ten different faults in the PVECU. The time to fault detection (FD) in the power converter and the electrical sensors is less than 290  $\mu$ s and the identification time is less than 4 ms. The time to FD and identification in the PV panel are less than 80 ms and 1.2 s, respectively. The proposed approach demonstrates higher fault sensitivity than that of existing approaches. It can diagnose a 20% drift in the electrical sensor gains and a 20% shading of a solar cell in the PV panel. [ABSTRACT FROM AUTHOR]