IEEE Journal of Emerging and Selected Topics in Power Electronics

Published by Institute of Electrical and Electronics Engineers
Online ISSN: 2168-6785
Print ISSN: 2168-6777
Publications
A high temperature wirebond-packaged phase-leg power module was designed, developed, and tested. Details of the layout, gate drive, and cooling system designs are described. Continuous power tests confirmed that the designed high-density power module can be successfully operated with 250 $^{circ}{rm C}$ junction temperature. The power module was further utilized in an all-SiC rectifier system that achieves a 2.78 kW/lb power density.
 
This paper presents an extensive comparative study between a two- and three-level inverter for electric vehicle traction applications. An advanced control strategy for balancing the two dc-link capacitors is also proposed. In this paper, the main focus is on the total voltage harmonic distortion (%THDv), the analytical derivation of the three-level capacitor currents, and the voltage balancing of two capacitor voltages. For generating the gate signals, space vector pulse width modulation (SV-PWM) is used. The developed voltage-balancing scheme helps to reduce the number of converter switching sequences, compared with the conventional SV-PWM strategy, and keeps the voltage difference between the two dc-link capacitors at the desired voltage level. The developed test-bench is used for a permanent magnet synchronous machine drive for electric vehicle (EV) applications. Detailed simulation studies are performed using MATLAB/Simulink block set and experimental verification is achieved using dSpace based real-time simulator. Both the simulation and experimental results show a significant improvement in reduction of total harmonic distortion (%THD (_{textit{v}}) ) for the three-level inverter.
 
This paper deals with an original control strategy for AC multidrive systems able to mitigate the effects of failures occurring on one or more drives. A key feature of the proposed technique is that fault tolerance capability is achieved by a suitable reconfiguration of the system in order to allow the healthy drives to provide additional paths for the currents of the faulty drives. Moreover, a modified control algorithm able to enforce the vector control in damaged drives has been implemented, by cooperatively managing some or all the drives of the system. Therefore, differently from previous techniques, the fault tolerance capability is achieved by exploiting the healthy drives, rather than activating back-up inverter legs. As a result, no additional high-frequency switching power devices and related drives circuitries are needed. In the following, two different scenarios will be analyzed, highlighting pros and cons of the proposed approach through simulations and experimental results.
 
This paper presents a method for minimizing the cost of vehicle battery charging given variable electricity costs while also accounting for estimated costs of battery degradation using a simplified lithium-ion battery lifetime model. The simple battery lifetime model, also developed and presented here, estimates both energy capacity fade and power fade and includes effects due to temperature, state of charge profile, and daily depth of discharge. This model has been validated by comparison with a detailed model developed at National Renewable Energy Laboratory, which in turn has been validated through comparison with experimental data. The simple model runs quickly, allowing for iterative numerical minimization of charge cost, implemented on the charger controller. Resulting electric vehicle (EV) charge profiles show a compromise among four trends: 1) charging during low-electricity cost intervals; 2) charging slowly; 3) charging toward the end of the available charge time; and 4) suppression of vehicle-to-grid power exportation. Simulations based on experimental Prius plug-in hybrid EV usage data predict that batteries charged using optimized charging last significantly longer than those charged using typical charging methods, potentially allowing smaller batteries to meet vehicle lifetime requirements. These trends are shown to hold across a wide range of battery sizes and hence are applicable to both EVs and plug-in hybrid EVs.
 
This paper proposes an improved vector space decomposition current control scheme for dual three-phase permanent magnet (PM) synchronous motors having two sets of three-phase windings spatially shifted by 30 $^{circ}$ electrical degrees. A proportional-integral (PI) and resonant (second) controller is developed for eliminating the current unbalance in $alphabeta$ subplane, which is effective irrespective of the degree of current unbalance, while PI plus multifrequency resonant (second and sixth) control is employed to eliminate the current unbalance, fifth and seventh current harmonics in $z_{1}z_{2}$ subplane. Compared with existing methods only accounting for current unbalance in $z_{1}z_{2}$ subplane, the proposed method has considered the current unbalances in both $z_{1}z_{2}$ and $alphabeta$ subplanes and can eliminate them simultaneously at the steady-state of operation. Consequently, the full compensation of current unbalance can be achieved, by which both the current unbalance between two sets and current unbalance between phase windings in each set are eliminated. Meanwhile, the fifth and seventh current harmonics caused by nonsinusoidal back electromotive force and inverter nonlinearity can also be fully compensated. The effectiveness of proposed method is verified by a set of comparative experiments on a prototype dual three-phase PM machine system. It shows that fully balanced currents without the fifth and seventh current harmonics at the steady state of operation can be achieved.
 
Voltage feedback flux-weakening control scheme for vector-controlled interior permanent magnet synchronous motor drive systems is considered in this paper. The voltage controller is based on the difference between the amplitude of the reference voltage space vector and a proper limit value, related to the feeding inverter limitations, and adopts the phase angle of reference current space vector as the control variable. A novel theoretical analysis of the dynamics of the voltage control loop is carried out by considering nonlinear effects and discrete-time implementation issues as well. The design of the controller can therefore be optimized for each operating condition by an adaptive approach, allowing to define stability properties and to maximize bandwidth of the voltage control loop. Maximization of the dynamical performances provides the main advantage of the proposal, that is, allows a lower voltage (control) margin to be considered with respect to standard approaches, leading to a higher torque and system efficiency and/or a reduced value of the dc bus capacitance. A motor drive system for home appliances is considered as a test bench to prove the effectiveness and importance of the proposal.
 
Nowadays, the use of multiphase fault tolerant permanent magnet (PM) machines is a suitable solution for increasing the reliability of high-performance motion control applications. This solution requires fault detection, isolation, and control adaptation. For this reason, a new open switch fault detection scheme in voltage-source inverter supplying a PM motor is presented in this paper. The detection method is based on model identification of the motor phase currents. The detection scheme is fast, robust, general, and capable of detecting multiple faults. The control algorithm, detection method, isolation, and reconfiguration strategies are discussed. After that, the proposed method is implemented in the fault tolerant control of a five-phase brushless direct current (BLDC) motor drive. Simulation results in MATLAB/Simulink are shown to demonstrate the effectiveness of the proposed detection technique. Experimental results on a five-phase fault tolerant BLDC motor validate the theoretical developments.
 
In APRIL 2013, a call was sent out to authors to propose papers for publication in the IEEE JOURNAL OF EMERGING AND SELECTED TOPICS IN POWER ELECTRONICS (JESTPE) for a Special Issue on advanced control of electric motor drives. Seventy nine papers were received for review and 21 were accepted for publication. The accepted papers are broadly divided into four parts: 1) sensorless control of electric machines; 2) fault-resilient control strategies; 3) advanced motor control techniques; and 4) design and analysis of synchronous-type electric machines.
 
Recently, extensive research has been conducted in the field of battery management systems due to increased interest in vehicles electrification. Parameters, such as battery state of charge (SOC) and state of health, are of critical importance to ensure safety, reliability, and prolong battery life. This paper includes the following contributions: 1) tracking reduced-order electrochemical battery model parameters variations as battery ages, using noninvasive genetic algorithm optimization technique; 2) the development of a battery aging model capable of capturing battery degradation by varying the effective electrode volume; and 3) estimation of the battery critical SOC using a new estimation strategy known as the smooth variable structure filter based on reduced-order electrochemical model. The proposed filter is used for SOC estimation and demonstrates strong robustness to modeling uncertainties, which is relatively high in case of reduced-order electrochemical models. Batteries used in this research are lithium-iron phosphate cells widely used in automotive applications. Extensive testing using real-world driving cycles is used for estimation strategy application and for conducting the aging test. Limitations of the proposed strategy are also highlighted.
 
The current phase in our transportation system represents a paradigm shift from conventional, fossil-fuel-based vehicles into the second-generation electric and hybrid vehicles. Electric vehicles (EVs) provide numerous advantages compared with conventional vehicles because they are more efficient, sustainable, greener, and cleaner. The commercial market penetration and success of EVs depend on the efficiency, safety, cost, and lifetime of the traction battery pack. One of the current key electrification challenges is to accurately estimate the battery pack state of charge (SOC) and state of health (SOH), and therefore provide an estimate of the remaining driving range at various battery states of life. To estimate the battery SOC, a high-fidelity battery model along with a robust, accurate estimation strategy is necessary. This paper provides three main contributions: 1) introducing a new SOC parameterization strategy and employing it in setting up optimizer constraints to estimate battery parameters; 2) identification of the full-set of the reduced-order electrochemical battery model parameters by using noninvasive genetic algorithm optimization on a fresh battery; and 3) model validation by using real-world driving cycles. Extensive tests have been conducted on lithium iron phosphate-based cells widely used in high-power automotive applications. Models can be effectively used onboard of battery management system.
 
This paper addresses an emerging reliability and safety requirement for more electric transportation systems by proposing an on-board diagnostics plug-in tool. For this purpose, a compact diagnostic algorithm is presented using an advanced speed feedback error management technique for traction motor and generator faults which is one of the most critical parts of the vehicle powertrain. The speed measurement accuracy can be degraded for various reasons such as: sensor issues, vehicle vibration, hardware tolerances, and environmental impacts like temperature, moisture, and electromagnetic interferences. Although the speed feedback errors within an acceptable level can be tolerated by most of the drive systems, the accuracy of speed measurement is critical for the reliability of fault diagnosis. The major reason behind this fact is the frequency of fault signature in the spectrum is primarily determined using the motor speed. It is shown how the reliability of a motor fault diagnosis decision can significantly be improved under erroneous speed feedback conditions by using the developed effective error localization and coarse-to-fine detection technique. The proposed scheme is implemented through effective strategies to minimize computational complexity and memory occupancy in every step of signal processing according to manufacturers' strict cost limitation.
 
Three basic intermediate bus architectures are reviewed for electronic power distribution system and components developers from a system perspective. Salient features for each system are discussed in detail. They cover input power stage, bus voltage level, output power stage, output regulation, multiple outputs, thermal property, system stability, and output impedance. Design tradeoffs are also presented to guide practical designs. It is concluded that the double regulated intermediate bus architecture has the best efficiency, regulation, thermal, and stability performances. Engineering hardware achieved a record efficiency of 99%, validating the superiority of the double regulated intermediate bus architecture.
 
This paper deals with objective criteria to compare conventional electric traction systems composed of a dc–dc boost converter, a voltage source inverter, and a permanent magnet synchronous machine with alternative topologies such as $Z$ -source inverter (ZSI) or quasi $Z$ -source inverter (QZSI). Rather focusing only on efficiencies issues, this paper deals with other relevant criteria. The stored energy in the systems is for instance linked with their passive elements weight, size, or cost. The currents rms values and the stepup voltage ratio are also considered. A complete losses evaluation is given and validated by both simulation and experimental results. The results show that the QZSI exhibits real advantages in terms of passive elements size since the stored energy during one operating cycle is lower than that for the conventional topologies.
 
Induction machine (IM)-based electric vehicle applications have gained significant popularity over recent years. However, failure of IM drivetrain components can lead to system malfunction and result in vehicle shutdown. Controller redundancy method is often used to tolerate microcontroller failure. However, this method results in high cost and complicates system design in terms of controller synchronization. This paper proposes a simplified digital control method for IM with low hardware requirements. Potentially, digital control method can work using simple auxiliary circuits without a microcontroller and can be used as a backup control strategy to maintain continuous operation of the IM in the event of microcontroller failure. This paper focuses on introducing the principle and implementation of digital control for IM and evaluating its performance. This digital control method can control three-phase squirrel cage IM system and enables motoring and generating operation. This method is extremely simple in design and implementation. Simulation and experimental results are included in this paper to validate our claims.
 
This paper presents an advanced switching sequence for space-vector pulsewidth modulation (SV-PWM)-based three level neutral-point clamped inverter. The developed scheme helps to reduce the number of converter switching sequences, compared with the conventional SV-PWM strategy, and keeps the voltage difference between the two dc-link capacitors at the desired voltage level. The developed test bench is utilized for a permanent magnet synchronous machine (PMSM) drive for electric vehicle applications. The proposed strategy is compared with the performance of a PI controller-based voltage balancing strategy. The proposed control strategy is based on the nearest three-vector (N3V) scheme, with a hysteresis control of the dc-link capacitor voltage difference. Conventional N3V scheme uses a higher number of switching sequences, which makes the switching losses higher. In addition, these switching sequences are not same for all subsectors. This makes the switching frequency to vary extensively. In the proposed control strategy, a reduced number of switching sequences are used, and they are same for all subsectors. This makes the system operate with constant switching frequency. Detailed simulation studies are performed to verify the performance of the proposed control strategy. The performance-based test results are then compared with those of a PI controller-based strategy. Experimental test results show significant improvement in the performance of the PMSM with respect to dc-link capacitor voltage variation as well as wide speed and torque range of machine operation.
 
The current state of wide bandgap device technology is reviewed and its impact on power electronic system miniaturization for a wide variety of voltage levels is described. A synopsis of recent complementary technological developments in passives, integrated driver, and protection circuitry and electronic packaging are described, followed by an outline of the applications that stand to be impacted. A glimpse into the future based on the current technological trends is offered.
 
A study was designed to investigate the potential benefits that ultracapacitors (UCs) may provide on the lifetime of lead-acid batteries. An experimental setup allowed the comparative cycling of two packs designed for a hybrid electric heavy-duty vehicle. Spectroscopy plots, charging current acceptability, and capacity tests were used to track the batteries’ degradation. The lifetime of the batteries was improved significantly as a result of the association of UCs.
 
The power train of fuel-cell vehicles (FCVs) can be composed of onboard hybrid energy sources to reduce fuel consumption, extend driving range through regenerative braking energy recovery, and possibly increase the specific power density. One of the main issues significantly affecting the FCV performance is the chosen hybrid system topology along with system components, which requires research to find the best hybrid structure for the lowest fuel consumption. Although several hybridization topologies have been studied separately in the literature, an overall investigation and fuel consumption comparison of the most promising fuel-cell (FC) power-train topologies along with the experimental verification should be realized. In this regard, this paper demonstrates a detailed comparison of four different hybrid FC power-train configurations with feasible battery and ultracapacitor (UC) combinations, on a test bench using normalized ECE-15 drive cycle. The results demonstrate that the lowest equivalent fuel consumption can be achieved with FC/battery/UC hybrid combination.
 
Voltage sourced converters (VSCs) in electric vehicle (EV) drive-trains are conventionally implemented by silicon Insulated Gate Bipolar Transistors (IGBTs) and p-i-n diodes. The emergence of SiC unipolar technologies opens up new avenues for power integration and energy conversion efficiency. This paper presents a comparative analysis between 1.2-kV SiC MOSFET/Schottky diodes and silicon IGBT/p-i-n diode technologies for EV drive-train performance. The switching performances of devices have been tested between −75 °C and 175 °C at different switching speeds modulated by a range of gate resistances. The temperature impact on the electromagnetic oscillations in SiC technologies and reverse recovery in silicon bipolar technologies is analyzed, showing improvements with increasing temperature in SiC unipolar devices whereas those of the silicon-bipolar technologies deteriorate. The measurements are used in an EV drive-train model as a three-level neutral point clamped VSC connected to an electric machine where the temperature performance, conversion efficiency and the total harmonic distortion is studied. At a given switching frequency, the SiC unipolar technologies outperform silicon bipolar technologies showing an average of 80% reduction in switching losses, 70% reduction in operating temperature and enhanced conversion efficiency. These performance enhancements can enable lighter cooling and more compact vehicle systems.
 
The design and test of the first undervoltage lock-out circuit implemented in a low-voltage 4H silicon carbide process capable of single-chip integration with power MOSFETs is presented. The lock-out circuit, a block of the protection circuitry of a single-chip gate driver topology designed for use in a plug-in hybrid vehicle charger, was demonstrated to have rise/fall times compatible with a MOSFET switching speed of 250 kHz while operating over the targeted operating temperature range between 0 °C and 200 °C. Captured data show the circuit to be functional over a temperature range from −55 °C to 300 °C. The design of the circuit and test results is presented.
 
This paper presents a self-sustaining integrated regulator for ultralow power two-input energy harvesting systems. The energy sources include photovoltaic panels and high frequency radio-frequency identification tags. An input-powered charge pump utilizing dynamic charge transfer switches with tunable voltages at the bottom of the pumping capacitors is proposed. No external pulse signal is required. An output-powered digitally controlled dc–dc switching converter with a low-complexity oversampling analog-to-digital converter is also proposed to analyze the error signal between the dc–dc switching converter output and the reference voltage. In order to avoid limit-cycle oscillation, a digital sigma-delta modulator is adopted to increase the equivalent resolution of the digital pulsewidth modulator. The system is completely implemented and fully integrated in a standard 0.18- (mu ) m CMOS process with a die area of 2.1 mm (^{2}) . The system output voltage is successfully regulated at 1 V and the measured maximum end-to-end conversion efficiency is (sim 57) %, when the loading current is 65 (mu ) A.
 
A new design approach for compact multiband transmitters, using a miniaturized outphasing power combiner is proposed. The technique is applied to design a dual-band (0.9/1.8 GHz) outphasing power amplifier with a fully integrated power combiner in 90-nm CMOS technology. Power losses in the combiner are minimized using high- (Q) slab inductors. The measured maximum output powers at 0.9 and 1.8 GHz are 24.3 and 22.7 dBm with maximum efficiencies of 51% and 34%, respectively.
 
It is known that constant power loads (CPLs) can yield instability in dc-power systems under certain operating conditions. This instability phenomenon is due to the interaction between the dc-grid and the negative input impedance characteristic of the CPLs. Dynamic behavior and stability analysis of a dc-microgrid with CPLs is presented in this paper. Then, a method to design a fault-tolerant stabilizing system for a dc-microgrid with CPLs is presented. It consists in implementing a local stabilizing agent on each CPL. Then, a method to design the stabilizing system is proposed. The method is based on the definition and resolution of a constrained optimization problem. It permits to consider several fault scenarios, such as the electrical reconfiguration of the dc-microgrid, or the failure of an agent. To illustrate the method's effectiveness, it has been implemented and experimentally tested on a test bed.
 
Peak torque and power density requirements for traction motor drives continue to increase, while demands on reliability are getting increasingly stringent as well. With the knowledge that most of the failure mechanisms are related to excessive temperature (cycling), thermal management is a key for increasing performance, without jeopardizing reliability. This paper proposes a control strategy for active thermal management of permanent magnet synchronous motor (PMSM) drives, based on real-time estimation and feedback of switching device and motor temperatures. By regulating the switching frequency and current control limit, critical components can be safeguarded from excessive temperature rise. Furthermore, optimal $dq$ -current control vectors are calculated within the temperature and voltage constraints, to maximize the drive's efficiency and speed–torque envelope. Hence, the control strategy enables the drivetrain to operate safely at maximum attainable performance limits. The strategy is experimentally validated on an 11-kW PMSM drive for a number of representative vehicle loads, including a maximum standstill torque test, a maximum acceleration test, and a driving cycle test.
 
This paper proposes a single-stage reconfigurable topology for an isolated dc/dc converter that supplies the 12 V power net from high voltage (HV) battery pack in hybrid and electric vehicles. The proposed topology solves the problem of reduced converter efficiency in the upper range of HV battery voltages. The converter is based on a zero voltage transition (ZVT) phase shift (PS) full bridge dc/dc converter that is during its operation, depending on the instantaneous value of battery voltage, reconfigured into a push–pull converter. The more efficient ZVT PS configuration covers the upper range of input voltages whereas the hard-switching push–pull configuration covers the lower, less significant range. The ZVT PS configuration, due to tighter voltage range, operates with reduced turn-off losses, significantly decreased circulating current in the freewheeling period as well as improved efficiency of the rectifier stage. The point of reconfiguration is chosen to maximize the average efficiency according to the histogram of HV battery voltage during a typical driving cycle. The operation of the proposed converter and the efficiency improvement are validated experimentally.
 
This paper demonstrates a two-stage approach for power conversion that combines the strengths of variable-topology switched capacitor techniques (small size and light-load performance) with the regulation capability of magnetic switch-mode power converters. The proposed approach takes advantage of the characteristics of complementary metal–oxide–semiconductor (CMOS) processes, and the resulting designs provide excellent efficiency and power density for low-voltage power conversion. These power converters can provide low-voltage outputs over a wide input voltage range with very fast dynamic response. Both design and fabrication considerations for highly integrated CMOS power converters using this architecture are addressed. The results are demonstrated in a 2.4-W dc–dc converter implemented in a 180-nm CMOS IC process and co-packaged with its passive components for high performance. The power converter operates from an input voltage of 2.7–5.5 V with an output voltage of ≤1.2 V, and achieves a 2210 W/in (^{3}) power density with ≥80% efficiency.
 
A multilayer planar interconnection structure was used for the packaging of liquid-cooled automotive power modules. The power semiconductor switch dies are sandwiched between two symmetric substrates, providing planar electrical interconnections and insulation. Two minicoolers are directly bonded to the outside of these substrates, allowing double-sided, integrated cooling. The power switch dies are orientated in a face-up/face-down 3-D interconnection configuration to form a phase leg. The bonding areas between the dies and substrates, and the substrates and coolers are designed to use identical materials and are formed in one heating process. A special packaging process has been developed so that high-efficiency production can be implemented. Incorporating high-efficiency cooling and low-loss electrical interconnections allows dramatic improvements in systems’ cost, and electrical conversion efficiency. These features are demonstrated in a planar bond-packaged prototype of a 200 A/1200 V phase-leg power module made of silicon (Si) insulated gate bipolar transistor and PiN diodes.
 
Due to increasing environmental concerns and decreasing fossil fuel supplies, electric vehicles (EVs) are fast becoming attractive alternatives to conventional fossil-fuel driven vehicles. Inductive power transfer (IPT) is a method that can be used to transfer power to EVs over an air-gap and can dramatically increase the range, convenience, and safety of EV battery charging. One of the major difficulties is determining the physical sizes of the primary IPT coupler, buried in the roadway, and the EV mounted secondary coupler. This is mainly due to the variation in vehicle classes and charging locations that may be encountered. This paper seeks to determine if suitably sized couplers can be selected, which can realize all these demands. A recently proposed EV charging coupler, known as the Double-D (DD), which has been shown to provide the best power to size ratio over typical expected air gaps is selected. As such a method to select the best design from eight approximately square DD couplers ranging from 300 to 1000 mm in length to meet the challenge of delivering high power over large air-gaps is presented. The performance of these couplers, or power pads, is simulated and the results can be used to select couplers for EV charging systems. A practical design example is presented involving the IPT charging of sedans and SUVs in multiple practical charging locations. The proposed pad sizes and systems are capable of transferring 10 kW to the EVs for realistic horizontal misalignments $({pm}{rm 200}~{rm mm})$ and air-gaps (100–400 mm).
 
This paper proposes a new modulation technique dual three-pulse modulation (DTPM) to switch dual full-bridge output capacitorless dc/dc converters to develop a pulsating dc link voltage encoding six pulse rectified output information. The pulsating voltage is directly fed to a standard six-pack inverter to develop three-phase ac output voltage. Proposed inverter and modulation are suitable for electric, hybrid electric, and fuel cell vehicles. The absence of the dc link capacitor and DTPM produce pulsating dc voltage that retains the sine-wave information (six- or three-phase rectified output) at the input of three-phase inverter. Inverter devices are modulated for 33% (one-third) of the line cycle and remains in their unique switching state (either on for 33% or off for 33%) and results in average device switching frequency of one-third of switching frequency. This results in 66% savings in switching losses. In addition, devices are not switched when the current through them is at its peak value and total savings in switching loss accounts to be up to 86.7% in comparison with a standard voltage source inverter with sine pulsewidth modulation. This paper presents operation and analysis of the pulsating dc link two-stage inverter controlled by the proposed DTPM at the front end and 33% modulation for the six-pack inverter along with the implementation. Design of the two-stage three-phase inverter has been illustrated. Analysis has been verified through simulation results using PSIM 9.0.4. Experimental results on a lab prototype have been demonstrated to validate the claims and the proposal.
 
In electric vehicle (EV) applications, the failure of phase current sensors often leads to emergency shutdown of induction machine (IM) drive to avoid system malfunction and protect the driver and hardware. However, emergency stop is not necessarily the best way to react if current sensor fails. This paper proposes a survivable operation technique for three-phase IM drives in the event of current sensor failure. The basic objective of survivable operation for IM is to seamlessly switch the control method from vector control to a simplified digital control with smooth transition strategy in the event of current sensor failure. Using this technique, the IM system can be kept running even when there are current sensor faults. It can therefore add one extra redundancy in EVs and make them safer and more reliable. Simulation and experimental results, including current sensor failure detection, speed and torque response, voltage vector, and phase-current waveforms, are included to show the effectiveness of the proposed strategy.
 
The challenges of achieving stability and good damping of a sensorless induction motor drive are much greater than for a sensored drive. In this paper, some frequently proposed flux and speed estimators—such as reduced- and full-order observers—are reviewed, along with their key static and dynamic properties as well as their parameter sensitivities. Three commonly occurring instability phenomena and their remedies are discussed, along with suitable analysis methods. Low-speed instabilities are most severe, and therefore, the stator resistance is the single most critical parameter. Methods for reducing the impact of this parameter are discussed.
 
The twenty-two articles in this special section focus on components, subsystems, systems, and grid interface technologies related to power and energy conversion for different types of electrified vehicles, including electric vehicles (EVs), range-extended EVs, hybrid electric vehicles, and plug-in hybrid electric vehicles as well as heavy-duty, rail, and off-road vehicles and airplanes and ships.
 
The eleven articles in this special section explore the technology and applications supported by miniaturized power electronics systems. Power electronics systems have gone through several generations of development during last half century. Its development has been significantly accelerated from late 1980s with the development of power MOSFET due to its superior performance, such as easier use, higher reliability, and higher switching frequency. High switching frequency operation plays a key role in miniaturizing the power electronics system as smaller inductor and capacitor can be used. In parallel, power system architecture, especially the intermediate bus architecture has facilitated this trend by reducing the overall size/board area needed for power system. Although it is by no means exhaustive, this special issue has provided a wide range of new technologies to minimize the size and volume of electronic power systems.
 
In this paper, the details of practical circuit and control implementation of an electric spring for reactive power compensation and voltage regulation of the ac mains are presented. With Hooke's law published three centuries ago, power electronics-based reactive power controllers are turned into electric springs (ESs) for regulating the ac mains of a power grid. The proposed ES has inherent advantages of: 1) ensuring dynamic load demand to follow intermittent power generation; and 2) being able to regulate the voltage in the distribution network of the power grid where numerous small-scale intermittent renewable power sources are connected. Therefore, it offers a solution to solve the voltage fluctuation problems for future power grids with substantial penetration of intermittent renewable energy sources without relying on information and communication technology. The proof-of-concept hardware is successfully built and demonstrated in a 10-kVA power system fed by wind energy for improving power system stability. The ES is found to be effective in supporting the mains voltage, despite the fluctuations caused by the intermittent nature of wind power.
 
Model-based rotor position/speed estimators are commonly used for sensorless control of interior permanent-magnet synchronous machines (IPMSMs) operating in the medium- and high-speed regions. A rotor position/speed estimation scheme usually contains three major parts: 1) a state observer; 2) a position estimator; and 3) a speed estimator. This paper proposes a sliding-mode observer (SMO) as the state observer to estimate the position-related system states, which are the extended electromotive force components in this paper. Then, two major contributions are made to achieve improved position and speed estimation. First, the rotor speed is estimated independently using a model reference adaptive system (MRAS)-based method, which is decoupled from the position estimation. To reduce the noise contents in the estimated speed, an adaptive line enhancer is proposed to work with the SMO, leading to an improved reference model for the speed estimation. The proposed MRAS-based speed estimator has two operating modes, which are suitable for generator and motor applications, respectively. Second, the estimated rotor speed is used as a feedback input signal to mitigate the oscillating error in the estimated rotor position, leading to an integrated position and speed estimation system. The effectiveness of the proposed position and speed estimators is verified by simulation using the data logged from a real-world test vehicle. Experimental results on a test stand of an IPMSM drive system used in off-road, heavy-duty hybrid electric vehicles are also provided to further validate the proposed rotor position/speed estimation schemes.
 
Existing position sensorless methods rely on: 1) one-to-one correspondence between magnetic characteristics of switched reluctance motor (SRM) and rotor position; and 2) access to terminal quantities (i.e., voltage and current) for all phases. The occurrence of a fault in one or more phases will prohibit the necessary access to the phase/s and as such introduces a challenge to successful implementation of the existing position sensing techniques. This paper investigates the existing sensorless methods with the occurrence of phase faults and introduces a family of generalized strategies for sensorless operation of SRM under single and multiphase faults. The experimental results of a four-phase SRM drive with different numbers of faulty phases are presented to validate the proposed strategy.
 
Fault-tolerant control (FTC) techniques for multiphase permanent magnet (PM) motors are usually designed to achieve maximum ripple-free torque under fault conditions with minimum ohmic losses. A widely accepted approach is based on flux distribution or back EMF (BEM) model of the machine to calculate healthy phase currents. This is essentially an open-loop technique where currents are determined (based on motor fault models) for each fault scenario. Therefore, it is highly model dependent. Since torque pulsation due to open-circuit faults and short-circuit faults are periodic, learning and repetitive control algorithms are excellent choices to minimize torque ripple. In this paper, iterative learning control (ILC) is applied as a current control technique for recovering performance in multiphase PM motor drives under fault conditions. The ILC-based FTC needs torque measurement or estimation, but avoids the need for complicated fault detection and fault diagnosis algorithms. Furthermore, BEM-based FTC and ILC-based FTC are proposed that initiates the learning from a model-based approximate guess (from the BEM method). Therefore, this method combines the advantages of both model information as well as robustness to model uncertainty through learning. Hence, the proposed method is well suited for high-performance safety critical applications. Finite element analysis and experimental results on a five-phase PM machine are presented for verification of the proposed control schemes.
 
In this paper, the total-flux representation for synchronous machines is presented. This representation is intended to supplement existing modeling tools, especially in machines which are highly nonlinear and for which standard models such as dq0 models are difficult if not impossible to implement.
 
In this paper, a new sensorless control strategy based on the square-waveform high-frequency pulsating voltage signal injection into the stationary reference frame is proposed. Similar to the sinusoidal-waveform injection method, by injecting the high-frequency square-waveform pulsating voltage carrier voltage into the $alpha$ - (or $beta$ -) axis of the stationary reference frame, the response carrier current will fluctuate with the position-dependent saliency, and then the rotor position information can be retrieved without any filtering. Furthermore, with higher frequency, the bandwidth of the position estimation can be significantly improved compared with all the sinusoidal-waveform injection strategies, and the influence of the winding resistance can also be fully eliminated. Meanwhile, the proposed new strategy injects a pulsating high-frequency carrier voltage into the stator stationary reference frame as stable as the rotating carrier signal injection method. Then, the rotor position information can be retrieved from the carrier current response, which is amplitude modulated by the machine saliency as simple as the pulsating carrier signal injection method. The experimental results validate that this strategy can achieve accurate rotor position estimation with good steady-state and dynamic performances by considering the cross-saturation effect even when there exhibits some noise in the estimated rotor position.
 
This paper presents an approach to design a measurement-based controller for induction machines. The proposed control approach is motivated by the fact that developing an appropriate mechanical model of such induction machines is a challenging task. Since our proposed control methodology is only on the basis of measured data, the controller design does not require any information about the model of the mechanical part. The control of motor drive is often based on sensorless field-oriented control techniques because of their advantages such as noise and cost reductions and high reliability. Hence, we assume here that measurements used for the controller design are collected using an estimator based on the electrical equations of the induction machine. A practical application to control the speed of an induction machine is presented to validate and demonstrate the efficiency of the proposed method.
 
Two-level voltage source inverter driving an IM. 
Voltage vectors of a two-level voltage source inverter and the corresponding switching states. 
Principle of the proposed strategy for torque ripple reduction. 
Block diagram of the variable switching point predictive torque controller (VSP 2 TC).
Experimental setup, including the two coupled squirrel-cage IMs (back), the two inverters (left), and the real-time computer system used for control (front).
This paper introduces an approach to include a variable switching time point into predictive torque control (PTC). In PTC, the switching frequency is limited by the sampling frequency; its theoretical maximum value is half the sampling frequency. However, in reality the switching frequency is lower than this value, and thus, high current and torque ripples occur compared with modulator-based control methods. In order to overcome this, an optimization problem is formulated and solved in real time. Thereby, apart from the regulation of the torque and the flux magnitude to their references, an additional control objective should be met: the minimization of the torque ripple. To do so, the time point at which the switches of the inverter should change state is calculated. Further advantages of the proposed method include the design flexibility and great performance during transients. Experimental results that verify the performance of the presented control strategy are included.
 
Application of inductive power transfer (IPT) to electric vehicles moving along the road can provide more charging flexibility with the reduction of weight and size of charge-storage batteries required in the vehicles. Existing research focuses on the efficiency improvement and alignment tolerance of the IPT transformer. Consideration of the transformer track length and the vehicle speed is rarely discussed. In this paper, an IPT vehicle charging system using a series of sectional tracks is studied. The relationship among various key parameters, such as vehicle speed, system efficiency, and power utilization of the IPT system, is studied in detail. Specifically, the impact on efficiency due to variation of track length and edge correction is reported. The extension of the system from a single pickup to multiple pickups is discussed. The results are verified with finite-element-analysis simulation and a scale-down experimental prototype.
 
Synchronous reluctance machines (SynRM) have been used widely in industries for instance, in ABB's new VSD product package based on SynRM technology. It is due to their unique merits such as high efficiency, fast dynamic response, and low cost. However, considering the major requirements for traction applications such as high torque and power density, low torque ripple, wide speed range, proper size, and capability of meeting a specific torque envelope, this machine is still under investigation to be developed for traction applications. Since the choice of motor for traction is generally determined by manufacturers with respect to three dominant factors: cost, weight, and size, the SynRM can be considered a strong alternative due to its high efficiency and lower cost. Hence, the machine's proper size estimation is a major step of the design process before attempting the rotor geometry design. This is crucial in passenger vehicles in which compactness is a requirement and the size and weight are indeed the design limitations. This paper presents a methodology for sizing a SynRM. The electric and magnetic parameters of the proposed machine in conjunction with the core dimensions are calculated. Then, the proposed method's validity and evaluation are done using FE analysis.
 
The aim of this paper is to present the mathematical proof of convergence of a position sensorless control algorithm. This algorithm is applied to control a drive with a nonsalient pole permanent magnet synchronous machine in low speed range including standstill. This paper shows that the convergence of this sensorless method does not depend on the machine parameters providing good robustness with respect to parameter uncertainties. In addition, the minimum saliency required for sensorless operation at zero speed is determined. The effectiveness of this technique is verified by simulation and experimentation on an eight-pole 1 hp–1000 r/min test machine. The experimental results confirm the effectiveness of the sensorless algorithm and the validity of the theoretical analysis.
 
In order to make the dual-direction silicon-controlled rectifier(SCR) which is highly robust in a high voltage environment, a gate controlled dual direction SCR(GC-DDSCR) device is proposed. After analyzing the working principle of the device through the equivalent circuit and Two-Dimensional(2D) device simulation, the Electro-Static discharge(ESD) characteristics of the device are verified through the transmission line pulse(TLP) test. The failure current of the gate controlled dual direction SCR(GC-DDSCR) structure is greatly improved to 14.19A compared to only 3.53A of the same size traditional dual direction SCR(TDDSCR) structure. The trigger voltage and holding voltage of the GC-DDSCR are 24.23V and 20.15V, respectively. In addition, this paper explains the principle of GC-DDSCR devices with high protection capability. That is, since the device has a polysilicon gate electrode shorted to the anode(cathode), the electric field effect generated by the gate promotes carrier movement in the SCR path. Thus, the electric field force promotes the opening of the SCR path of the device and the direction of the electric field force is always consistent with the current direction. The overall failure capability of the device is effectively improved.
 
While the functionality of emerging wireless microsensors, cellular phones, and biomedical implants, to name a few, is on the rise, their dimensions continue to shrink. This is unfortunate because smaller batteries exhaust quicker. Not surprisingly, recharging batteries wirelessly is becoming increasingly popular today. Still, small pickup coils cannot harness much, so induced EMF voltages vEMF.S are low. Modern receivers can resonate these low input voltages to rectifiable levels, but only with a finely tuned capacitor that resonates at megahertz when on-chip and at kilohertz when off-chip. In other words, resonant rectifiers are sensitive to frequency and dissipate considerable switching power when integrated on-chip. Unluckily, excluding the resonant capacitor requires a control signal that synchronizes switching events to the transmitter's operating frequency. The 0.18-μm CMOS prototype presented here derives this synchronizing signal from the coupled vEMF.S by counting the number of pulses of a higher-frequency clock across a half cycle during a calibration phase and using that number to forecast half-cycle crossings. This way, the prototyped IC switches every half cycle to draw up to 557 μW from 46.6 to 585-mVPK signals with 38%-84% efficiency across 1.0-5.0 cm.
 
This paper reports the first multiphase implementation based on the recently proposed nonlinear average current control (NACC) for power-factor-correction and dc–dc converters. A multiphase boost dc–dc converter with control and low-side power switches integrated on the same die using the 0.35- m HV CMOS process is designed and introduced. The converter benefits from using analog current controllers that are very simple, insensitive to noise, and independent of converter and control design parameters. Multiphase operation effectively enables higher operating frequency (seen from the converter input and output), which in turn enables smaller reactive components to be selected. The converter is dedicated to supplying the electric vehicle auxiliary board net (12 V) from the photovoltaic cell stack input, allowing a maximum power of 40 W to be transferred at 500-kHz switching frequency of each phase (effectively at 1.5 MHz). Maximum power point tracking is performed as the converter global control at 7.5 kHz, while the inner control loops are based on NACC. Suitability of such hybrid converters for integration with active solar cells makes them favorable to be used as a solar range extender for electric/hybrid vehicles, making this a step forward toward a complete system miniaturization of solar regenerative energy solutions in automotive applications—solar-module-integrated dc–dc converters. Experimental measurements performed with a converter prototype including a chip based on 0.35- m HV triple-well CMOS technology verify the proposed multiphase operation and NACC control method.
 
Top-cited authors
F. Blaabjerg
  • Aalborg University
Xiongfei Wang
  • Aalborg University
Marta Molinas
  • Norwegian University of Science and Technology
Lennart Harnefors
Alejandro Gómez Yepes
  • University of Vigo