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This paper proposes a novel emulation system for emulating the power system in the fuel cell electric vehicle. The major purpose of the proposed emulation system is to test the dc–dc converter between the fuel cell and high-voltage powertrain. The bidirectional buck–boost type dc–dc converter is applied in the emulation system as the basic elements. A modularized approach is presented for easily scaling up and down the power level of the emulation system. Meanwhile, an energy loop structure is implemented in the proposed emulation system for power capability boosting purpose. Because of the proposed energy loop configuration, the emulation system offers long-term running capability with high power rating without the grid connection. A neutral current control mechanism is applied in this paper to further enhance the long-term testing capability as well as extending the lifespan for the battery packages. The simulation studies are proposed in this paper to validate the control mechanisms of the emulation system. A 10 kW hardware prototype has been built and the experimental tests are presented for validating the functionalities of the emulation system. [ABSTRACT FROM AUTHOR]

In order to increase the torque density of the five-phase machines, the third harmonic is commonly employed. In this paper, the optimal and critical ratios for the third harmonic current injection are analytically derived and validated by finite element (FE) analyses. It is found that the optimal and critical injection ratios along with the torque improvement are dependent on the ratio of the third harmonic back electromotive force to the fundamental one. In order to improve the electromagnetic torque contributed by the third harmonic component, this paper employs unequal tooth to increase both the fundamental and third harmonic winding factors. Meanwhile, the optimal unequal tooth width combination is deduced and demonstrated by the FE method. When the third harmonic current is injected under the same amplitude constraint, the output torque can be improved. When the third harmonic current is injected under the same RMS value constraint, for the ten-slot/eight-pole equal tooth machine, the output torque can barely be increased, whilst for the unequal tooth machine, the output torque can be increased by 2.1%. Finally, the ten-slot/eight-pole machine with unequal teeth is prototyped and tested to prove the analyses. [ABSTRACT FROM PUBLISHER]

This paper proposes the series–series compensation topology to realize a low-voltage and high-current inductive power transfer system (IPT) for the automatic guided vehicles (AGVs). Since the height of the AGV chassis is in the tens of mm, the coupling coefficient is close to 1, resulting in a tightly coupled IPT system. This paper has three main contributions. First, it reveals that the high-order harmonic currents in a tightly coupled IPT system could be very significant. Second, it quantifies the impact of the high-order harmonic currents on the efficiency, which shows the efficiency can be reduced. Third, it proposes an effective method to design the parameters in order to reduce the harmonics and maintain high efficiency. Aiming at the charging of AGVs, a prototype is constructed. The magnetic coupler size is 220 mm × 220 mm × 10 mm. When the airgap is 10 mm, it achieves 1.8-kW power transfer with a dc–dc efficiency of 89.9% from a 400-V dc source to a 24-V dc load, and the charging current is 74 A. When the airgap varies from 5 mm to 15 mm, the power variation is within ±350 W, and the efficiency is not affected. The fast Fourier transform analysis of the experimental currents also validates the theoretical analysis and the simulation results. [ABSTRACT FROM AUTHOR]

Electric motorcycles use a battery storage system and a controlled inverter (motor drive) to drive the wheels. Given that the sale of electric motorcycles is expected to grow significantly over the next decade, the aim of this research is to add a supercapacitor storage system to this simple network in order to extend the autonomy of the motorcycle. This paper analyzes and demonstrates the benefits of two different structures for adding a supercapacitor bank to a lithium-ion battery pack: a passive filter and a buffer for the battery. The advantages of each structure are presented and design guidelines are provided. In addition, we propose a synthetic inductor filter typology based on the two analyzed structures in order to increase the autonomy of the motorcycle. Simulations and experimental results using real data validate the analysis. This paper then uses real data extracted from an electric motorcycle to compare the four topologies: batteries only, the passive filter, the buffer, and the synthetic inductor semi-active hybrid storage system. The comparison shows that battery capacity is extended up to 7.8% with a smoother current profile. However, due to the losses from the added converter in cascade, the net capacity of the whole system is extended only up to 3.7%. Therefore, improvements in the dc/dc converter can further increase the entire system capacity. [ABSTRACT FROM AUTHOR]

This paper presents the development of an electric-vehicle (EV) interior permanent-magnet synchronous motor (IPMSM) drive and its operation control. The power circuit of the established EV IPMSM drive consists of a two-leg interleaved bidirectional front-end dc/dc buck–boost converter and a three-phase inverter. The front-end converter can establish adjustable and boostable dc-link voltage for the motor drive to enhance its high-speed driving performance. It can also allow the battery bank to be charged from the motor during regenerative braking. Good current sharing control between converter modules and dc-link boosted voltage regulation response are preserved via the developed robust control scheme. Moreover, fast disturbance rejection response against the module fault and recovery is achieved. The comparative driving performance enhancements via dc-link voltage boosting and commutation instant tuning are conducted. Then, through proper setting and control, the established EV IPMSM drive possesses good driving performances, including starting, acceleration/deceleration, regenerative braking, and reversible operation characteristics. [ABSTRACT FROM PUBLISHER]

LLC resonant converters are widely used in On-board Power Converter but the pumping voltage of traditional LLC converter is unavoidable under light-load conditions due to the existence of parasitic parameter. In this paper, an LLC resonant converter with damping split inductor is proposed to improve the light-load regulation capability. The original resonant inductor is divided into two parts in series. Then, a simple damping resistor connected on one part in parallel and the other part can be integrated into the transformer. Using damping split inductor, significant regulation improvements could be achieved under light-load conditions with not any change in control strategy and almost zero hardware cost. In addition, based on impedance analysis of the resonant tank, the effects of the proposed method are analyzed including voltage gain, soft switching characteristics, suppression of high frequency interference components, and system power loss. Moreover, the detailed design process and optimization conditions of the damping split inductor parameters are carefully illustrated. Eventually, the experimental results demonstrate the characteristics mentioned above for the 96 W prototype at the expense of a maximum increase in device loss of 0.85 W. [ABSTRACT FROM AUTHOR]

To process the power in hybrid energy systems using a reduced part count, researchers have proposed several multiinput dc–dc power converter topologies to transfer power from different input voltage sources to the output. This paper proposes a novel bidirectional nonisolated multi-input converter (MIC) topology for hybrid systems to be used in electric vehicles composed of energy storage systems (ESSs) with different electrical characteristics. The proposed converter has the ability to control the power of ESSs by allowing active power sharing. The voltage levels of utilized ESSs can be higher or lower than the output voltage. The inductors of the converter are connected to a single switch; therefore, the converter requires only one extra active switch for each input, unlike its counterparts, hence resulting in reduced element count. The proposed MIC topology is compared with its counterparts concerning various parameters. It is analyzed in detail, and then, this analysis is validated by simulation and through a 1-kW prototype based on a battery/ultracapacitor hybrid ESS. [ABSTRACT FROM PUBLISHER]

With finite element method (FEM), cuboid elements (or tetrahedron elements) are often used in the traditional grounding analysis. In the irregular boundary, smaller and denser elements are usually applied to approximate the real boundary. However, this increases the number of elements in the boundary, leading to an increase in computation time. In order to introduce FEM into tunnel integrated grounding system (IGS) in high-speed railway better, a curved hexahedron element is proposed for tunnel structure. In this paper, the stiffness matrix of curved hexahedral element in space is first derived based on coordinate transformation. Two different stiffness matrices are compared in the condition that the structure of curved hexahedron element is highly similar to that of cuboid element. Later, the number of required elements according to the proposed method is compared with that of the traditional one on the basis of meeting same accuracy requirement. Finally, the results of the proposed method are compared with those of current distribution, electromagnetic fields, grounding and soil structure analysis (CDEGS). Through the above-mentioned three comparison schemes, the curved hexahedron element model is verified by its precision and applicability. From this, the distribution of the electromagnetic field inside the tunnel IGS is obtained. [ABSTRACT FROM AUTHOR]

Reported researches on smart charging methods have the disadvantages of low calculation efficiency or have not simultaneously taken the three-phase imbalance, voltage, and power flow constraints into account. It is an important topic to improve the computational speed to meet the online rolling optimization requirement for EVCC problems. In this paper, the branch power flow equations of balanced and unbalanced distribution system are derived. The linearization methods for the nonlinear terms of the branch power flow equations are proposed. Two stages linear programming (LP) is introduced for EVCC to minimize the total charging costs of the holders where three-phase imbalance, charging demand, voltage, and power flow constraints have been taken into account. Via ignoring the nonlinear terms of the branch power flow equations, the first stage LP is formulated to calculate the estimated branch power and node voltages as the initial points for linearizing the nonlinear terms of branch power flow equations. The second stage LP is formulated to calculate the optimal charging power using the linearized branch power flow equations. Four case studies show that the proposed method without the compromise of precision is significantly faster than state-of-the-art works with respect to the computational speed. [ABSTRACT FROM AUTHOR]

The recent increasing penetration of plug-in electric vehicles (PEVs) has provided an opportunity to develop individual PEVs aggregators who benefit from coordinating the vehicles. Optimal self-scheduling of such an aggregator, considering network operation indices, and distribution system operator's (DSO's) policies on the aggregator's performance are the key issues investigated in this paper. The proposed method maximizes the aggregator's daily profit through participating in day-ahead and real-time electricity markets and offering power quality services to DSO in an incentive and regulatory scheme. These services are designed in terms of the daily voltage profile and the power losses cost of the network. The problem is modeled as a two-stage stochastic scheduling problem considering customers’ satisfaction, impacts of uncertainties of driving patterns and real-time market prices, and effects on network operation indices. The model is formulated as a mixed-integer linear programming problem and implemented in GAMS $^{\bigcirc \!\!\!\!{\hbox{R}}}$ software. The technical and financial aspects of the plug-and-play uncoordinated and the proposed coordinated approaches are finally compared for different penetrations of PEVs in a test grid. The results show that applying the proposed strategy can benefit the aggregator in electricity markets and satisfy PEV owners too. Moreover, the reliable and economic operation of the grid can be guaranteed through applying incentive and regulatory policies on the aggregator's performance in high penetration levels. [ABSTRACT FROM AUTHOR]

Research studies of vehicle-to-grid (V2G) are gaining more and more attention, because of its attractive features, such as, transferring bidirectional power between electric vehicles and grid, regulating grid voltage/frequency etc. This paper investigates the damping technique of the grid-connected inverter for a V2G application. As the silicon carbide (SiC) mosfet has obvious advantages in high-power-density inverters with a high switching frequency, an LLCL filter-based SiC mosfet inverter is designed to suppress the harmonics and increase the power density in this paper. By analyzing and comparing the suppression effects of four passive damping methods on the resonance peak of the LLCL filter, it is found that passive damping control strategy brings extra loss into the V2G system, and affects the performance of LLCL filter. An active damping control method is proposed to reduce losses and ensure better dynamic performance. The feasibility of the design scheme and performance are verified by simulations and experiments. [ABSTRACT FROM AUTHOR]

Traditional current control methods for a single-phase rectifier in an electric traction drive system suffer from either long response time or nonzero steady-state error. A novel current vector control strategy in stationary-frame is therefore proposed, in this paper, to improve the control performance of a rectifier. The mathematic model of the single-phase two-level pulse rectifier was first analyzed by complex space vector. Then, the principle of the proposed current control method was described. Based on this, the implementation and parameter tuning method of the current control algorithm based on a space complex vector in a two-phase stationary coordinate system are presented. Moreover, two kinds of general current control algorithms are analyzed and compared with the proposed algorithm to demonstrate the advantages of the proposed algorithm. The proposed control scheme absorbs advantages of the conventional control schemes, including fast response, zero steady-state error, and active and reactive power independent control, but overcomes their shortcomings. Finally, the theoretical analysis is verified by means of simulation as well as a hardware-in-loop experimental test on an experimental laboratory setup and some comparisons with conventional current control algorithms prove the advantages of the utilized method. [ABSTRACT FROM AUTHOR]

For large power application of inductively coupled power transfer (ICPT) system, such as traffic railway, multiple pickups have to be adopted. The condition exists that current unbalance of ICPT system with multiple parallel pickup modules, which will cause instability and low reliability. Aimed to solve the issue, the paper analyses the uncoupled module of ICPT system, assesses the impact of the mutual inductance, compensated state, and coil resistance on current unbalance, and put forward a novel current-balance strategy to balance the parallel currents by introducing the circuit of impedance transformation including semi-controlled rectifier, and BUCK, and BOOST circuits. Experiments have been done on the platform of ICPT prototype, and the experimental results are presented to show the correctness of the theoretical analysis and the effectiveness of the control strategy. When the output voltage is 220 V and load is 6 Ω, the output power is 8 kW. The amplitude ratio of the two parallel currents is 2.04 without control, and the amplitude of the two current is almost equal when adopting the strategy. System efficiency stays constant or increases slightly after adopting the proposed control strategy. [ABSTRACT FROM AUTHOR]

This paper proposes a new energy storage system (ESS) design, including both batteries and ultracapacitors (UCs) in hybrid electric vehicle (HEV) and electric vehicle applications. The conventional designs require a dc-dc converter to interface the UC unit. Herein, the UC can be directly switched across the motor drive dc link during the peak power demands. The resulting wide voltage variation due to UC power transfer is addressed by the simple modulator that is introduced in this paper, so that the motor drive performance is not disrupted. Based on this new methodology, this paper further introduces two ESS schemes with different topologies, namely 1) UC rating and 2) energy flow control. They are applicable to both lightly and heavily hybridized HEVs. Both schemes have the benefits of high efficiency (without a dc-dc link) and low cost. The simulation and experimental results validate the new methodology. [ABSTRACT FROM AUTHOR]

It is well known that batteries do not perform equally throughout their lifetimes. Their properties are in constant degradation, their capacity fades, and the maximum power reduces. Battery aging has been widely studied under laboratory-controlled conditions for different types of cells. In real life, however, every person has their own driving profile, which is almost unique and unpredictable, making the state of health (SOH) during real-life cycles highly difficult to estimate accurately. This paper presents a methodology for aging estimation based on data extracted from onboard data loggers installed in an electric vehicle (EV). When a driver turns off the vehicle, the battery voltage slowly increases until it finally reaches the open circuit voltage (OCV). It has been observed that the recovery voltage transition depends on the temperature and aging, providing new elements to verify the battery SOH. [ABSTRACT FROM PUBLISHER]

Nodal voltages and feeder currents are acquired by running load flows for electric vehicle (EV) charging purposes. The impact of the charging is analyzed by either visually inspecting the voltages and currents or calculating appropriate impact indices. Optimal charging, on the other hand, is performed by incorporating the voltages and currents in charging strategies. Though the impact indices are frequently used for assessing the impact, their usage for optimizing charging has been minimal. Therefore, this paper develops probabilistic impact indices for nodal voltage violations and feeder overloading, which can be applied not only for investigating the impact but also for optimizing charging. Also, aggregated EV load demand of a large EV population is modeled by using a new combined state of charge (SOC)-based charging strategy in time series, for assessing the applicability of the developed impact indices for practical purposes. The combined SOC dynamically integrates arrival and departure of EV and delivered energy. The numerical results show that the proposed impact indices in conjunction with the SOC-based charging have numerous advantages over the conventional charging strategies aided by the load flows. [ABSTRACT FROM AUTHOR]

In order to improve the working performance of linear metro, the multistep model predictive control (MMPC) is applied to linear induction machine (LIM) in this paper. However, due to the maximum current and voltage limitations, the optimal problem of multistep model predictive control (MMPC) becomes difficult to handle in practice. For simplifying the optimal problem of an MMPC with constraints, first, the optimal problem of MMPC is solved off-line, with the assumption that the input voltage of the LIM is continuous without limitations. And, the expression of current constraint is expressed by voltage variables through the mathematical model of the LIM to simultaneously consider both the voltage and current limitations. Then, according to the solved optimal value without constraints, one iterative algorithm is proposed to search a suboptimal value, which satisfies both the current and voltage limitations. Finally, the proposed strategy is applied to two 3-kW arc induction motors to verify its effectiveness. [ABSTRACT FROM AUTHOR]

This paper proposes a design technique for electric ship traction machines to achieve high torque density and low torque ripple by adopting dual m-phase windings with an appropriate phase shift. Firstly, the general relationship between the slot number and the phase number for dual m-phase windings is investigated. Secondly, the uniform analytical expressions of torque with different phase shifts are derived. Also, the optimal phase shift angle is summarized from the perspective of improving torque performance. Then, the 48-slot and 22-pole permanent-magnet machines for electric ship with different windings configurations are designed. The finite-element method is used to calculate their electromagnetic performances, such as back electromotive force, torque capability, stator magnetic motive force and radial force. Finally, some experiments on the prototype machine for electric ship are carried out for validation. [ABSTRACT FROM AUTHOR]

Thermal and state-of-charge (SOC) imbalance is a well-known issue that causes nonuniform aging in batteries. The modular battery based on cascaded converters is a potential solution to this problem. This paper presents bipolar control (BPC) of a modular battery and compares it with previously proposed unipolar control (UPC) mode in terms of thermal/SOC balancing performance and energy efficiency. The BPC needs four-quadrant operation of a full-bridge (FB) converter using bipolar pulsewidth modulation (PWM) inside each module, whereas UPC only needs a half-bridge (HB) converter with unipolar PWM. The BPC, unlike UPC, enables charging of some cells while discharging others. An averaged state-space electrothermal battery model is derived for a convex formulation of the balancing control problem. The control problem is formulated on a constrained linear quadratic (LQ) form and solved in a model predictive control (MPC) framework using one-step-ahead prediction. The simulation results show that BPC, without even requiring load current variations, gives better balancing performance than UPC but at the cost of reduced efficiency. The UPC requires at least current direction reversal for acceptable balancing performance. In short, the UPC is a more cost- and energy-efficient solution for electric vehicle (EV) and plug-in hybrid EV applications, whereas the BPC can be beneficial in applications involving load cycles with high current pulses of long duration. [ABSTRACT FROM PUBLISHER]

Due to an increasing in-vehicle electric load demand, a new 48-V electric system architecture proposed by German premier car manufacturers has been gaining increasing attention recently for electrified vehicles. In this paper, a multiple-voltage bus converter for the 48-V and existing 12-V dual supply system, providing additional flexible dc bus voltages, is proposed. The proposed converter can provide a dual flexible dc voltage bus and an additional dependent voltage bus while simultaneously managing the 12-V supply net using only one single-leg switch pole and a diode. The additional dc voltage buses will provide more options to accommodate variable electric load components in a vehicle, improving their power density. Due to the multiple control objectives, the single-leg pole requires a multimode switching strategy to regulate the additional bus voltages. To improve the onboard vehicle system reliability and performance, an impedance network structure is implemented in the converter to obtain a dead-time-free pulsewidth modulation (PWM). Simulation and experimental results are presented to verify the feasibility and effectiveness of the proposed structure and control method. [ABSTRACT FROM PUBLISHER]

On account of complementary control, reduced size, and energy saving, the switched-capacitor (SC) based equalizer becomes promising for the energy management of energy storage system. Traditionally, the number of the bypass capacitor in the SC based equalizer equals to the number of the battery module in series or parallel connections. The amount of bypass capacitors is enormous, thus costly and bulky for electric vehicles (EVs). In this paper, the integrated energy storage is proposed to reduce cost and save space, meanwhile, the equalizations between the batteries and the ultracapacitors (UCs) are achieved by the reutilization of SC network. UCs not only perform as energy storage units, but also work as energy exchange units. Thus, the number of balanced elements can be reduced significantly. The operational principles of the storage system and the analyses of the balancing process are examined in detail. The system simulation is performed for functionality evaluations. Meanwhile, an experimental prototype is also implemented for six cells to demonstrate the balancing process. The accordance of experiment and simulation can further testify the feasibility and effectiveness. [ABSTRACT FROM AUTHOR]

In this paper, the model predictive thrust control (MPTC) method is applied in combination with the arbitrary two voltage vectors modulation strategy so as to acquire the more accurate modulation. Because of the huge number of possible voltage vector pairs that need to be evaluated, it may consume high calculation cost to find the best pair of voltage vectors (BPVV). So, one simplified method is proposed to avoid the tedious process of enumerating and comparing all possible cases, which can find directly the BPVV from large number of possible voltage vector pairs. Besides, the current limit is introduced into MPTC to avoid the overcurrent in dynamic transients, and the proposed search method is also effective to the case with current limit. This method has been numerically simulated and experimentally tested on a platform consisting of two coupled 3kW arc induction motors. Both simulation and experimental results show that the MPTC performance is improved by using the modulation of BPVV under different conditions, and its complexity is reduced obviously. [ABSTRACT FROM AUTHOR]

This paper presents the analysis and design procedure of a voltage equalizer, which consists of a boost full-bridge input cell and a symmetrical voltage multiplier (SVM). The batteries under different initial voltage conditions can be charged to a desired uniform voltage level by the proposed voltage equalizer. The fundamental operation principle of the voltage equalizer is described, and a dc equivalent resistance model is derived to analyze the charging and equalization behaviors. The design procedure based on analytical models is presented to give the optimal parameter configuration for the voltage equalizer to reduce voltage imbalance among the batteries and improve the power conversion efficiency. The model of the equivalent resistance is verified by simulation study of an equivalent circuit. A 10-W prototype for 3 series-connected energy storage modules was built and tested with voltage imbalance. Experimental results confirm the validity of the design method, and demonstrate that the proposed voltage equalizer can achieve a good voltage equalization with a standard deviation reduced to a few millivolts. [ABSTRACT FROM AUTHOR]

The linear permanent magnet vernier (LPMV) machines have been paid more attention in railway vehicles because of its simple structure and low cost. In this paper, the ring type winding (RTW) is adopted in both non-modular and modular LPMV machines to improve force density. The configuration and operating principle of two LPMV-RTW machines are presented. The coil connection and mechanism of RTW are explained and compared with conventional distributed winding (DW) and concentrated winding (CW). The back electromotive force and thrust force are investigated by the time-stepping finite-element method. It is found that non-modular LPMV-RTW machine possesses larger force density than non-modular LPMV-DW machine while modular LPMV-RTW machine has higher force density and utilization ratio of winding than modular LPMV-CW machines under the constant copper loss. Finally, the experiment result is obtained on the prototype, verifying the theoretical analysis. [ABSTRACT FROM AUTHOR]

This paper designs and implements an electro- mechanical propulsion system for a 42-V battery-sourced integrated starter-alternator (ISA) using an indirect-field-oriented (IFO) controller with a speed sensor on the shaft of the machine. The design aspects of the ISA energy conversion system are discussed, with emphasis on the motor selection and comparison of various candidate machines, power electronics, motor controller development and its integration with the engine controller, and a strategy for charging and discharging the energy source. A boost converter powered by the 42-V battery charges three 1-F ultracapacitors to 300 V, thus running the motor drive system at 300 V. The designed 300-V motor drive system is compared with the 42-V drive system directly powered by the 42-V battery. To improve the performance of the propulsion system, two modifications are proposed in this paper. First, terminal-quantities-based accurate voltage and current model flux observers (CMFOs) are designed, which can be used for any off-the-shelf machine. Second, a current model flux-observer-based sensorless controller is presented, which eliminates the need for the speed sensor on the rotor shaft, thus reducing the cost as well as the maintenance of the drive system. The proposed terminal-quantities-based flux observers and sensorless controller form the core of direct and IFO controllers commonly used in any alternative energy vehicular application including the ISA. The designed voltage model flux observer is insensitive to the stator resistance, and the CMFO is insensitive to the rotor resistance and speed, thus overcoming the long-standing problems in the area of flux observer design. The experimental results obtained while driving the vehicle are presented to demonstrate the effectiveness of the prototype ISA and to investigate its performance requirements as a sensorless drive system. Finally, the performance of the proposed flux observers and sensorless controller is evaluated through experimental results on a prototype induction machine to evaluate their potential for implementing a sensorless ISA drive system. [ABSTRACT FROM AUTHOR]

Power electronic converters and electric motor drives are being put into use at an increasingly rapid rate in advanced automobiles. However, the new advanced automotive electrical systems employ multivoltage level hybrid ac and dc as well as electromechanical systems that have unique characteristics, dynamics, and stability problems that are not well understood due to the nonlinearity and time dependency of converters and because of their constant power characteristics. The purpose of this paper is to present an assessment of the negative impedance instability concept of the constant power loads (CPLs) in automotive power systems. The main focus of this paper is to analyze and propose design criteria of controllers for automotive converters/systems operating with CPLs. The proposed method is to devise a new comprehensive approach to the applications of power electronic converters and motor drives in advanced automotive systems. Sliding-mode and feedback linearization techniques along with large-signal phase plane analysis are presented as methods to analyze, control, and stabilize automotive converters/systems with CPLs. [ABSTRACT FROM AUTHOR]

In this paper, a higher fidelity battery equivalent circuit model incorporating asymmetric parameter values is presented for use with battery state estimation (BSE) algorithm development; particular focus is given to state-of-power (SOP) or peak power availability reporting. A practical optimization-based method is presented for model parameterization fitting. Two novel model-based SOP algorithms are proposed to improve voltage-limit-based power output accuracy in larger time intervals. The first approach considers first-order extrapolation of resistor values and open-circuit voltage (OCV) based on the instantaneous equivalent circuit model parameters of the cell. The second proposed approach, which is referred to as multistep model predictive iterative (MMPI) method, incorporates the cell model in a model predictive fashion. Finally, a SOP verification methodology is presented that incorporates drive cycle data to realistically excite the battery model. Simulation results compare the proposed SOP algorithms to conventional approaches, where it is shown that higher accuracy can be achieved for larger time horizons. [ABSTRACT FROM PUBLISHER]

A new single-switch high step-up dc–dc converter is proposed, in this paper, for fuel cell vehicles. The proposed topology utilizes an L2C3D2 network to obtain high voltage gain and reduce the voltage stress on the power switch. Additionally, the proposed converter has a universal input voltage in order to suit the soft output characteristics of the fuel cell. Comprehensive analyses of the steady-state operation in continuous conduction mode and discontinuous conduction mode, and design considerations of the proposed converter are given. Finally, a 400 V/1.6 kW scaled-down prototype is developed to validate the effectiveness and feasibility of the proposed converter. [ABSTRACT FROM AUTHOR]

The output characteristics and the transfer efficiencies of inductive power transfer (IPT) systems are affected by (but not limited to) the variation of parameters such as, variable load, misalignment between the primary and secondary coils, and resonance frequency detuning. This paper first analyzes the resonant conditions of all voltage-fed compensation topologies in IPT systems to achieve the load-independent voltage transfer characteristic at load-independent zero phase angle frequency. With these conditions, the parameters sensitivity to the key performance factors of the S-SP, LCC-S, LCC-P, and double-sided LCC compensated IPT systems are systematically investigated when considering the losses in coils and compensation networks. Comparisons of the quantitative sensitivity analysis and experimental results for all IPT systems are made in terms of the voltage transfer ratio and efficiency. These analyses can provide guidance for the selection of superior compensation networks to minimize the additional converter effort and simplify the control algorithm of closed-loop IPT systems. [ABSTRACT FROM AUTHOR]

With new developments in power electronics and semiconductor devices, there has been an increasing interest in the adoption of power electronic traction transformer (PETT) topologies in railways, mainly for the purpose of mass and volume reduction against conventional topologies. Apart from traction transformers, examples include isolation circuits for on-board auxiliary power units (APU) and even 750 VDC, 110 VDC and lower voltage (e.g., 72 VDC) battery chargers. Special attention has been given to the more mature technology of three-stage (ac–dc–MFac–dc) configurations with intermediate medium frequency ac (MFac) links. In contrast to conventional architectures, it becomes difficult to select a suitable multistage topology of power electronics for the design of complex traction systems with advanced requirements. The power electronics utilized in different configurations have a significant effect on performance, efficiency, power quality (harmonics and stability), and cost indicators for the whole system, making the selection and design process more complex. The objective of this paper is to provide a clear overview of proposed topologies with special emphasis on the power electronic architectures utilized in three-stage PETT systems particularly for railway traction systems and on-board APUs. With regards to the listed range of possible architectures provided to the reader, key characteristics, such as total semiconductor (switches and diodes) count numbers per module per phase, input/output voltage levels, operating frequencies, and the most commonly used resonant networks, are summarized and discussed. [ABSTRACT FROM AUTHOR]

Electric rail transit systems are large consumers of electricity, which face challenges related to improving their overall energy efficiency. Although various solutions have been proposed to achieve this target, it is not feasible to implement and test all of them. Since finding the solution that is most appropriate to a given system is typically a site-specific problem, an accurate, validated, and reliable simulation tool is crucial. In this paper, a simulation model for studying wayside energy storage systems in dc electric rail transit system is presented. The proposed model provides a reliable tool for analyzing the behavior of the transit system during intervals that span from a small fraction of time (milliseconds) up to 24 h. In order to validate the proposed simulation model, its results were compared with real measurements of a standard subway system. [ABSTRACT FROM AUTHOR]

The capability of misalignment tolerance is vital for inductive power transfer (IPT) systems. S/SP compensation topology can provide a strong capability of misalignment tolerance if it is properly designed. This paper presents a detailed deduction process to acquire the optimal coupling coefficient, tuned at which the system can achieve minimum output voltage fluctuation. The impact of primary and secondary coupling inductance on output voltage fluctuation versus load variation was also analyzed. The output voltage fluctuation is not affected by the primary coupling inductance, but it decreases when the secondary coupling inductance is increased. Theoretical analysis was validated by both simulation and experiment. Three 200-W IPT prototypes were built. An overall efficiency of 94.1% was achieved when the coupling coefficient was 0.1733. The output voltage fluctuation was as low as 1.5% when the coupling coefficient increased by 34.5%, from 0.1288 to 0.1733. With a 900% rise in load resistance (from 80 to 800 Ω), the output voltage fluctuation decreased from 5.8% to 4.0% when the secondary coupling inductance increased from 136.3 to 250.0 μH. [ABSTRACT FROM AUTHOR]

Cell voltage equalization is inevitable to ensure years of safe operation of series-connected energy storage cells, such as lithium-ion batteries and supercapacitors (SCs). Although various kinds of cell voltage equalizers have been proposed, most equalizer topologies require multiple switches and/or a multiwinding transformer, resulting in complex circuitry and poor modularity. In this paper, a single-switch single-transformer equalizer using a forward–flyback resonant inverter (FFRI) with a voltage multiplier is proposed. The required switch count of the proposed equalizer is the minimum without impairing modularity due to the single-switch circuitry with no need for a multiwinding transformer. An experimental equalization test performed for eight SCs connected in series successfully demonstrated the equalization performance of the proposed equalizer. The FFRI can be extended as a “resonant input cell,” and by combining one of resonant input cells and a voltage multiplier, a single-switch resonant equalization charger that is basically a charger with an equalization function is also derived. An experimental charging test using the resonant equalization charger was also performed, and its equalization-charging performance was demonstrated. [ABSTRACT FROM AUTHOR]

Battery charging is growing in importance as it has direct influence on battery performance and safety. This paper develops a generalized online estimation method for a charge-polarization-voltage-based resistance–capacitance (RC) circuit model to simulate the charging behavior of Li-ion batteries. The effects of charging current, initial state of charge (SOC), initial polarization state, and aging on the charge polarization voltage are quantitatively analyzed in both time and SOC domains. It is demonstrated that the charge polarization voltage is nonlinearly related to these impact factors. In the SOC domain, the change in the charge polarization voltage is also analyzed with the gradient analytical method, and the relations between current, polarization voltage amplitude at the inflection point, and SOC are quantitatively established. This can be used to estimate battery SOC and polarization voltage accurately. A constant-polarization-based fuzzy-control charging method is proposed to adapt charging current acceptance with battery SOC stages. Experimental results demonstrate that the proposed charging method significantly shortens charging time with no obvious temperature rise compared with the traditional constant-current–constant-voltage charging method. [ABSTRACT FROM AUTHOR]

This paper proposes a controller to minimize the overall drive system's losses and the key inverter and motor losses by mapping machine's speed and torque demands to an optimal state current and switching frequency. The objective function takes into account copper and core losses of the machine along with conduction and switching losses of the inverter. The effect of the inverter harmonics on the voltage and current waveforms is modeled and shows that while higher switching frequency increases inverter loss, it decreases the machine's loss. The inverter switching frequency varies with the speed and load torque. The voltage and current limitation are used as the constraint. The effects of the current, voltage, and switching frequency are shown on the losses of the machine and the inverter. The result of optimization for each pair of speed and load torque is the corresponding $dq$ axes current and switching frequency. A control system is implemented based on the optimization scheme to verify the optimization process. The effectiveness of the control system is verified experimentally. [ABSTRACT FROM AUTHOR]

State-of-health estimates of batteries are essential for onboard electric vehicles in order to provide safe, reliable, and cost-effective battery operation. This paper suggests a method to estimate the 10-s discharge resistance, which is an established battery figure of merit from laboratory testing, without performing the laboratory test. Instead, a state-of-health estimate of batteries is obtained using data directly from their operational use, e.g., onboard electric vehicles. It is shown that simple dynamical battery models, based on a current input and a voltage output, with model parameters dependent on temperature and state of charge, can be derived using AutoRegressive with eXogenous input models, whose order can be adjusted to describe the complex battery behavior. Then, the 10-s discharge resistance can be conveniently computed from the identified model parameters. Moreover, the uncertainty of the estimated resistance values is provided by the method. The suggested method is validated with usage data from emulated electric vehicle operation of an automotive lithium-ion battery cell. The resistance values are estimated accurately for a state-of-charge and temperature range spanning typical electric vehicle operating conditions. The identification of the model parameters and the resistance computation are very fast, rendering the method suitable for onboard application. [ABSTRACT FROM PUBLISHER]

This paper proposes a unique integrated and isolated dual-output dc–dc resonant converter, which can interface both HV traction batteries and LV loads. In addition, the proposed topology is bidirectional, capable of delivering power from HV traction batteries to the grid for vehicle-to-grid (V2G) applications. To increase the power density of the converter, the dual-output dc–dc resonant converter combines magnetic components of resonant networks into a single three-winding electromagnetically integrated transformer. The resonant converter uses a half-bridge topology with split capacitors as the resonant network components to further reduce the size of a converter. The variable dc-link voltage strategy is utilized to enhance the efficiency over the entire output voltage range. A 3.3-kW converter is designed and developed for validation of various operation modes, including grid-to-vehicle, V2G, and HV-to-LV charging. [ABSTRACT FROM AUTHOR]

This paper investigates the inverter nonlinearities in a drive system based on silicon carbide metal-oxide-semiconductor field-effect transistor (SiC-mosfets) and compares its performance with that of an equivalent silicon insulated-gate bipolar transistor (Si-IGBT) system. Initially, a novel comprehensive analytical model of the inverter voltage distortion is developed. Not only voltage drops, dead time, and output capacitance, but also switching delay times and voltage overshoot of the power devices are taken into account in the model. Such a model yields a more accurate prediction of the inverter's output voltage distortion, and is validated by experimentation. Due to inherent shortcomings of the commonly used double pulse test, the switching characteristics of both SiC-mosfets and Si-IGBTs in the pulse width modulation inverter are tested instead, such that the actual performances of the SiC and Si devices in the motor drive system are examined. Then, the switching performance is incorporated into the physical model to quantify the distorted voltages of both the SiC-based and Si-based systems. The results show that, despite its existing nonlinearities, the SiC-based drive has lower voltage distortion compared to the conventional Si-based drive as a result of its shorter switching times and smaller voltage drop, as well as a higher efficiency. Finally, the overriding operational advantages of the SiC-based drive over its Si-based counterpart is fully demonstrated by comprehensive performance comparisons. [ABSTRACT FROM PUBLISHER]

DC-link voltage fluctuation, originated from the single-phase power supply, has a significant impact on the railway traction drive system. Instead of employing a large LC filter to suppress the fluctuation, software solutions are of more interests, since they do not add additional components to the system. A state-of-the-art feedforward strategy predicts the dc-link voltage pattern based on its repetitive nature and directly modifies the duty cycle fed to the inverter to eliminate the impact of the fluctuation. Yet this strategy requires a symmetrical and consistent pulse pattern. In this paper, a compensation approach for synchronous space vector modulation with multiple pulse patterns is proposed. It utilizes the prediction of the dc-link voltage pattern and, based on the volt–second balancing principle, modifies the switching instants corresponding to different pulse patterns. Simulation and experimental results show that the proposed method can significantly eliminate the impact of the fluctuation. [ABSTRACT FROM PUBLISHER]

This paper proposes an interleaved equalization architecture for series-connected lithium-ion battery strings, which can deliver energy from a battery module to the cells in the next adjacent battery module, resulting in an enhancement of the equalization current and efficiency. Particularly, the global equalization is achieved without the need of additional stage circuits to balance among modules, leading to a small size and low cost. A two-module equalizer based on resonant LC converter and buck converter with soft switching is implemented to verify the validity of the proposed interleaved architecture. Furthermore, a self-learning fuzzy logic control (SLFLC) algorithm is employed to online regulate the equalization period based on the voltage difference among cells and the cell voltage, not only greatly abbreviating the balancing time but also effectively preventing overequalization. The SLFLC has the outstanding advantages of high balancing precision, easy implementation, and strong robustness. Experimental results demonstrate that the proposed equalizer has good balancing performances with soft switching and high efficiency, and achieves zero-voltage gap among cells. Moreover, the proposed SLFLC algorithm abridges the total equalization time by about 27%, and reduces the equalization cycles by about 59% compared with the traditional control algorithm. [ABSTRACT FROM AUTHOR]

In high-voltage dc power systems of advanced aircraft, most of the electrical motor drives and power electronic converters behave as constant power loads (CPLs) when tightly regulated and usually cause negative impedance instability problems. This paper presents stability criteria for an electrical system constituted of a dc power supply, multistage LC filters, and an ideal CPL. The derived criteria are based on the Brayton–Moser mixed potential theory and can be extended to actual CPLs. The dynamic negative incremental impedance of the CPL is used to place design constraints on the filter parameters to prevent instabilities. Simulation and experimental results confirm that the proposed criteria would guarantee system stability under different voltage disturbances. [ABSTRACT FROM PUBLISHER]

An adaptive Kalman filter algorithm is adopted to estimate the state of charge (SOC) of a lithium-ion battery for application in electric vehicles (EVs). Generally, the Kalman filter algorithm is selected to dynamically estimate the SOC. However, it easily causes divergence due to the uncertainty of the battery model and system noise. To obtain a better convergent and robust result, an adaptive Kalman filter algorithm that can greatly improve the dependence of the traditional filter algorithm on the battery model is employed. In this paper, the typical characteristics of the lithium-ion battery are analyzed by experiment, such as hysteresis, polarization, Coulomb efficiency, etc. In addition, an improved Thevenin battery model is achieved by adding an extra RC branch to the Thevenin model, and model parameters are identified by using the extended Kalman filter (EKF) algorithm. Further, an adaptive EKF (AEKF) algorithm is adopted to the SOC estimation of the lithium-ion battery. Finally, the proposed method is evaluated by experiments with federal urban driving schedules. The proposed SOC estimation using AEKF is more accurate and reliable than that using EKF. The comparison shows that the maximum SOC estimation error decreases from 14.96% to 2.54% and that the mean SOC estimation error reduces from 3.19% to 1.06%. [ABSTRACT FROM PUBLISHER]

Battery-charging algorithms can be used for either single- or multiple-battery chemistries. In general, single-chemistry chargers have the advantages of simplicity and reliability. On the other hand, multichemistry chargers, or “universal battery chargers,” provide a practical option for multichemistry battery systems, particularly for portable appliances, but they have some limitations. This paper presents a review of some charging algorithms for major batteries, i.e., nickel–cadmium, nickel–metal–hydride, and lithium-ion batteries for single- and multiple-chemistry chargers. A comparison between these algorithms in terms of their charging schemes and charge termination techniques is included. In addition, some trends of recent chargers development are presented. [ABSTRACT FROM PUBLISHER]

To meet the stringent cost targets for hybrid electric, plug-in hybrid electric (PHEV), and all-electric vehicles, serious improvement in battery cycle life and safety is undoubtedly essential. More recently, lithium batteries, in the form of lithium-ion, lithium-polymer, or lithium iron phosphate, have profoundly been explored. Despite critical research initiatives, lithium-based batteries have not yet been able to meet the steep energy demands, long lifetime, and low cost, which are unique to vehicularpropulsion applications. One of the most practical techniques of improving overall performance is to use suitable power electronics intensive cell-voltage equalizers in conjunction with onboard energy-storage devices. There have been some interesting developments in this area during the last few years, but cost constraints and high current specifications have prevented the complete deployment of this versatile technology. The purpose of this paper is to introduce a novel configuration for a cell-voltage equalizer, with the potential of fulfilling the expectations of low cost, high current capability, and high efficiency. A comprehensive comparison between the theoretical novel equalizer, a typical equalizer, and the experimental prototype of the novel equalizer will be presented, which will help analyze performance, complexity, and cost. [ABSTRACT FROM AUTHOR]

Due to high efficiency, compactness, and less generated noise of permanent magnet synchronous motors, they have received a lot of attention for traction applications in land, sea, and undersea vehicles. In this paper, a new digital deadbeat controller is designed, implemented, and applied to a permanent magnet synchronous machine. The objective of the controller is to achieve a deadbeat dynamic response for the speed of the machine. The analysis of the controller shows that it adjusts the current and voltage of the machine with two and four sampling periods, respectively. A robust simple sensorless method is used to estimate the position and velocity of the rotor. The experimental results of a laboratory prototype is presented, which show the viability of the proposed controller for this machine. [ABSTRACT FROM AUTHOR]

This work proposes the use of inductive links to wirelessly power an autonomous sensor in a vehicle application. The selected application is intended for occupancy and belt detection in removable vehicle seats, where wiring the seat detectors from the vehicle chassis is impractical. The autonomous sensor includes seat detectors and a wireless transceiver to transfer the data on the state of detectors. To compensate the loose coupling between the coupled coils, resonant tanks were used. To drive the transmitting resonant network, a commercial class-D amplifier was used. Working frequency was restricted to 150 kHz. Commercial magnetic-core coils were selected as they provide high coil values and quality factors in a small-size factor, which is a requirement for the intended application. At the receiving network, a rectifier and a voltage regulator were used to provide dc voltage supply to the autonomous sensor. Three kinds of voltage regulators were compared from the point of view of the power efficiency. Both a theoretical analysis and experimental results are presented for different combinations of coils and working frequencies. Theoretical analysis shows that the operating points for the linear shunt regulator always lead to higher power efficiencies compared with other alternatives such as linear series and switching buck regulators. Experimental tests were carried out using a mechanical setup to fix the coil-to-coil distances. Experimental results agree with the theoretical analysis. Achieved power efficiencies ranged from around 50% to 10% for coil-to-coil distances from one to three times the inner diameter of the coils. Experimental tests also showed that the autonomous sensor was properly powered up to coil-to-coil distances of 2.5 cm, i.e., more than four times the inner diameter of the coils. [ABSTRACT FROM PUBLISHER]

The ungrounded scheme with overvoltage protection device (OVPD) has been adopted in the construction of Nanjing Metro Line 1. During the operation of Line 1, a high rail potential was observed, which caused the OVPDs installed at some traction supply substations (TSSs) to keep turning on at any moment, and the stray-current leakage increased obviously. Since the magnitude of rail potential and stray current depends on the modes of a running vehicle, including accelerating, coasting, constant speed, or braking, Line 1 suspected that the vehicle running modes were the cause of a potential rise in the rail. This paper presents the results of field tests and numerical simulations to study whether different vehicle running modes have an impact on rail potential and stray current in Line 1. The results show that the rail potential in the acceleration and brake modes is significantly higher than that in the other modes, which are in the opposite direction. Moreover, within the stray-current interference, the maximum shifts of buried-conductor potential may exceed the limit in these two modes. In addition, the high rail potential and buried-conductor potential occur when the running mode changes from acceleration to coasting or the maximum brake power is reached. As a vehicle is running between two different TSSs, the rail potential is highest in its position. [ABSTRACT FROM PUBLISHER]

Cell voltage equalizers are necessary to ensure years of operation for series-connected supercapacitors (SCs) by eliminating cell voltage imbalance. Conventional equalizers require numerous switches and/or magnetic components; hence, the circuit complexity and size tend to increase. In this paper, a double-switch single-transformer equalizer, which is based on the combination of a half-bridge inverter and a voltage multiplier, is proposed. The operation of the proposed equalizer is analyzed in detail, and a dc equivalent circuit is mathematically derived. Experimental equalization tests were performed for eight SCs connected in series under a voltage-imbalanced condition. The energy of the series-connected SCs was preferentially redistributed to SCs with low voltages, and eventually, the voltage imbalance was eliminated, demonstrating the equalization performance. Simulation-based equalizations using the derived dc equivalent circuit were also performed under the same condition as the experiments. The experimental and simulation results were in good agreement, indicating that the derived dc equivalent circuit can adequately express real equalization profiles. [ABSTRACT FROM PUBLISHER]

This paper concerns the study of contact opening under dc voltage in the case of high-intensity current (a few hundred amperes). The application fields are mainly automotive and aeronautical systems. An experimental device has been designed in order to study the opening of contacts under various conditions. The influence of several parameters on contact opening is studied. These are the following: the opening velocity, the current intensity through the closed contact, the nature of the contact materials (Ag, Ag-12wt%SnO2), the value of the inductance in the electrical circuit. The measured parameters characterizing the opening phase are as follows: the arc duration, the value of the electrode gap when the arc extinguishes, the arc energy, the maximal value of the contact voltage during the opening phase, and the electrode erosion. The study of the erosion is achieved with the help of a 3-D profilometer enabling the measurement of mass transfer and, for instance, of the amount of molten or evaporated metal. [ABSTRACT FROM AUTHOR]

Advancements in high-power semiconductor technology have opened new avenues for application of power electronics converters in safety critical applications such as in hybrid vehicle automotive power systems. This paper discusses the use of statistical moments to detect and identify faults. Existing system current and voltage sensors are used without the need for any additional sensors. The technique not only detects system malfunction but also provides information on the device under fault and the nature of the fault. An accurate knowledge of the same will allow appropriate action to be taken to avoid propagation of fault that may lead to catastrophic failure. [ABSTRACT FROM AUTHOR]