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In order to achieve the purpose of extending the speed range and reducing power electronics devices for the permanent-magnet linear motor drive system, a half-centralized open-end winding (OEW) topology is studied for rail transit applications in this paper. In this topology, compared with the traditional OEW topology, the number of voltage-source-inverters (VSIs) can be reduced from four to three to drive two OEW movers and all these VSIs share a common dc bus voltage. In order to improve the steady-state performances, a four-vector phase model predictive voltage control (FV-PMPVC) is proposed in this paper. Due to the spatial distribution of phase voltage vector (PVV), an orthometric synthesis principle (OSP) is proposed to calculated the duration time for the vector synthesis, which reduces the computation burden and enhances the robustness. Comparing the existing control method, FV-PMPVC can get similar dynamic performances but better steady-state performances. Additionally, the half-centralized topology using FV-PMPVC can have same speed range while less VSIs are required. The effectiveness of FV-PMPVC is verified by experimental results. [ABSTRACT FROM AUTHOR]

Aiming at the low-frequency oscillation (LFO) phenomenon in high-speed railways, this paper proposes a feedback linearized virtual inertia control (VIC) strategy of the traction converter based on a sliding mode observer (SMO) to improve the robustness of the system and suppress the occurrence of LFO. First, to optimize the total harmonic distortion of the traction grid-side current, the inner loop controller is designed as the feedback linearization control. Then, the voltage outer loop is designed as a combination of the VIC designed in this paper and SMO, which enhances the system inertia and reduces the impact of external interference on the system, while reducing the controller's demand for electrical power on the DC-side. Furthermore, a small-signal model is established to analyze the stability of the single-phase vehicle-grid system under the proposed control. The influence of the control parameters on stability is discussed in detail. Finally, the comparison of software simulation and hardware-in-the-loop experimental results between traditional PI control, feedback linearization control, feedback+SMO, feedback+VIC and the proposed control method shows that the proposed control has better dynamic and static characteristics, and can effectively inhibit the occurrence of LFO. [ABSTRACT FROM AUTHOR]

This paper presents a novel active power control scheme for SRMs that are used as S/G units at MEAs; the proposed method uses a vector-controlled SAF, facilitating the acceleration of the SRM during starter mode and the efficient power control of the SRG at various operational points during generator mode. Moreover, an energy storage unit is incorporated in the SAF, aiming at enhancing the SRM's starting torque production and taking full advantage of the SRG's energy generation capability, through the appropriate phases’ magnetization regulation that is imposed by the developed adaptive SAF vector control. In addition, the proposed scheme provides enhanced FRTC during both modes of operation. The mathematical analysis is verified through MATLAB/Simulink simulations, while the performance of the S/G concept under study is evaluated via real-time CHIL tests, with the use of the dSPACE 1202 (MicroLabBox) platform and the 16-bit dsPIC30F4011 microcontroller. [ABSTRACT FROM AUTHOR]

The installation of a ground energy storage system (ESS) in the substation can improve the recovery and utilization of regenerative braking energy. This paper proposes an energy management strategy (EMS) of adaptive threshold adjustment for ground ESS. In this regard, this paper analyzes the energy flow in traction power supply system (TPSS) with different headways and no-load voltage. According to the influence of charge and discharge threshold on the energy flow in TPSS, the laws of energy flow are formulated. Subsequently, an EMS based on fuzzy logic control (FLC) is designed. The proposed EMS is adaptive to the variation of headway and no-load voltage. By monitoring the charge-discharge effect of ESS and the variation of substation output energy within two adjacent periods, the charge-discharge threshold is adjusted adaptively to guarantee the recovery effect of regenerative braking energy. Finally, the simulation and field experiment of proposed EMS are carried out with ground energy storage device and actual line conditions of Beijing Batong line. The experiment results indicate the good performance of proposed EMS in terms of energy saving. [ABSTRACT FROM AUTHOR]

This paper presents a multi-stage series model predictive control (MS-MPC) for PMSM drives in order to further improve the control performance of MPC. Firstly, the basic principle of conventional MPC is introduced. Then, the multi-stage series MPC is proposed in this paper, in which the cost functions of different prediction instant are adopted to form series control structure. In this method, the current prediction trajectory of one voltage vector is extrapolated to multiple control periods, and the control performances of every voltage vector during multiple control periods are evaluated by multi-stage series cost functions. Additionally, the implementation process of the proposed method is described. Finally, the comparison experiments between the conventional MPC and the proposed method show that the proposed method can effectively reduce the switching frequency under the same control frequency. In addition, the improvement of current control performance can be achieved by the proposed method under the condition of the same switching frequency. [ABSTRACT FROM AUTHOR]

This paper presents an adaptive neural fault-tolerant control algorithm for the path-following activity of the underactuated surface vehicle (USV) using the novel output-based triggering approach. In the algorithm, the event-triggered mechanism is designed utilizing the attitude states from the kinematics aspect of USV. Both the control inputs and the related calculation thread are implemented only at the trigger instants. Furthermore, neural networks (NNs) are employed to remodel the model uncertainties, and the adaptive observer is developed to estimate and compensate for the effect of the unknown actuator faults. With the direct Lyapunov theorem, the semi-global uniformly ultimately bounded (SGUUB) stability can be guaranteed for the closed-loop system in aspects of both the trigger instant and the continuous interval. The comparison experiment has been illustrated to verify the effectiveness of the proposed algorithm, which can effectively improve the information transmission performance and the fault-tolerant capability. [ABSTRACT FROM AUTHOR]

In this paper, a battery charging and swapping optimization model is established for electric vehicles (EVs) and battery charging/swapping stations (BCSS). The EVs are categorized into private electric vehicles (PrEVs) and electric taxis (ETs), where the charging behaviors of PrEVs are modeled based on the Monte Carlo (MC) method, and the battery swapping (BS) strategies of ETs are optimized by bi-level dynamic game. Moreover, the voltage deviation of the power grid is considered in the load regulation process of ETs. A “path-location” model is established combining with the Floyd algorithm in the simulation and the IEEE 14-Bus system is used to derive the node voltage. Numerical results show that the proposed strategy can simultaneously increase the revenue of BCSS and ETs and reduce the voltage deviation. [ABSTRACT FROM AUTHOR]

This paper presents a framework to determine the feasible dispatch limits of solar photovoltaic (PV) generation in the unbalanced distribution network considering the interconnection of electric vehicles (EVs) and associated uncertainties. The proposed framework determines the lower and upper dispatch limits of PV generation considering the worst-case realization of a) the minimum and maximum storage capacity of EVs, b) the minimum and maximum power dispatch of EVs, c) the lower and upper bounds for the arrival and departure times, and d) the available energy at arrival and departure times. The unbalanced operation of the distribution network as well as the uncertainty in the maximum PV generation and demand forecasts were considered. The problem formulation and solution approach are validated using the modified IEEE 34-bus and IEEE 123-bus distribution systems. The impacts of the budget of uncertainty and the vehicle-to-grid operation mode of EV clusters were addressed in the case studies. It is shown that integrating EVs with charging capability will increase the lower dispatch limit or increase the upper dispatch limit of the PV generation. Moreover, the increase in the budget of uncertainty will reduce the difference between the upper and lower dispatch limits by increasing the lower dispatch or decreasing the upper dispatch limit of the PV generation. Finally, it is shown that the vehicle-to-grid capability will reduce the total lower dispatch limit or increase the total upper dispatch limit of the PV generation in the operation horizon. [ABSTRACT FROM AUTHOR]

Two-stage AC-DC converters are considered as a prominent solution for DC-type electric vehicle (EV) chargers. However, this kind of architecture suffers from high switching losses with large heatsink and DC-link capacitor volume. To relieve this issue, this paper presents a new hybrid modulation for DC-type EV chargers, where a two-phase clamped discontinuous pulse-width-modulation (DPWM) in the front-end circuit is cooperated with the variable frequency triangular-current-mode (TCM) zero voltage switching (ZVS) or its simplified implementation, i.e., boundary-ZVS (B-ZVS) strategy, in the back-end circuit. The former can stop the switching actions in the front-end stage during two-thirds of the grid period, while the AC currents are at their highest values, which can yield to the best switching loss reduction and deliver high power factor operation. Besides, TCM-ZVS or B-ZVS modulations can achieve ZVS turn-on action for all semiconductors during all operating range in the DC-DC stage to further reduce the power losses on the semiconductors. With such characteristics, the proposed strategies can reduce the switching losses of the system to the best extent, and thus allow an enhancement of the system power density by improving the power conversion efficiency. The proposed strategy is described, analyzed, validated, and benchmarked in a 5 kW SMD SiC MOSFET-based two-stage AC-DC converter. A 99% power efficiency can be achieved with the solution implementing the TCM-ZVS strategy at an output voltage of 400 V and rated power. [ABSTRACT FROM AUTHOR]

This paper presents an isolated single-stage on-board electric vehicle charger without an intermediate DC-link. Based on an isolated current-source topology, the converter features soft-switching in semiconductors regardless of load variation for the full AC line voltage range. Moreover, it requires no external snubber or clamp circuits. The power factor correction and voltage regulation are provided by a relatively simple phase shift modulation, while the amount of circulating energy is kept at minimum. The charger is distinguished by its efficiency characteristic – the maximum is achieved in the constant power charging mode. The control method, component stresses, and design constraints of the topology are analyzed. The concept is verified using a 3 kW experimental SiC-based prototype, which reaches a peak efficiency of 96.4%. Moreover, the charger has demonstrated efficiencies above 95% with the THD of 4.1% when operating in constant power mode at the maximal power. [ABSTRACT FROM AUTHOR]

The ‘train-rail’ integrated grounding system for high-speed trains plays the critical role in providing the unique path for power feedback, which mainly consists of two parts - the on-board dynamic grounding sub-system and the fixed terrestrial grounding sub-system. The on-board dynamic grounding sub-system can be classified into two types of grounding modes – working grounding provides the discharging path for transferring the traction power; while the protective grounding maintains reference ground potential for the train body – both of which share the rail as the common path for discharging current. Thus, the traction current discharged from the working grounding wheel sets flows through the neighboring protective grounding wheel sets back to the train body, forming as the ‘train-rail’ current reflux. The ‘train-rail’ current reflux may result in the appearance of a ‘train body’ (TB) current, which may rise the potential of the train body. The TB current and voltage may cause electromagnetic interference to the on-board equipment, electrochemical corrosion on grounding wheel bearing or even on-board partial temperature surging. In this paper, a ‘train-rail’ coupling integrated grounding model is launched to evaluate both the TB current and voltage. Based on this model, different grounding distribution schemes have been tried and compared, considering the impact brought from TB current and voltage. The external grounding resistors are installed in series at the protective grounding wheel sets implemented, with the aim of restricting the TB current and voltage. Ultimately, the best-performed grounding scheme of installing external resistors is found out. [ABSTRACT FROM AUTHOR]

The stationary supercapacitor energy storage system (SCESS) is one of effective approaches for the utilization of train's regenerative braking energy in urban rail systems. In this paper, the capacity configuration of SCESSs, the no-load voltage of substation, the control of onboard braking resistors and train operation diagrams are considered comprehensively. Based on the equivalent circuit model, the effects of traction power system parameters on the energy transmission between powering trains, braking trains and SCESSs are analyzed, and the relationships between the train operating parameters and system energy consumptions are revealed. A multi-variable synthetic optimization method is proposed to optimize the SCESS capacity, train operation diagrams and traction power system parameters collaboratively. In order to reduce the search space and improve the efficiency of the optimization algorithm, a hierarchical multi-objective optimization model is established, based on which the design variables and the control variables are optimized iteratively. And as the traffic density has a great impact on the regenerative braking energy distribution of the system, the optimization objective function fully considers the frequency distribution of headways throughout the day. Combined the Elitist Non-dominated Sorting Genetic Algorithm (NSGA-II) with the traction power flow simulator, the flowchart of the two-stage optimization algorithm is designed, and the pareto set of the multi-objective problem is obtained. The advantages of reducing system energy consumptions and configuration cost under the proposed algorithm are verified based on case studies of Beijing Batong Line. [ABSTRACT FROM AUTHOR]

Rotational speed detection is important for alternator-voltage-regulator (AVR) to starts-up and generates regulated electric power for vehicles. However, the rotational speed detection in standby mode for self-start is challenging with low loss rectifier, such as the Schottky diode. In this paper, a novel rotational speed detection method by sensing phase voltage or field voltage at specific modes is proposed to solve the issue without extra wiring or external components. The analysis of phase voltage in standby mode considering rectifier leakage current explains the challenges of conventional detection. The derivation of field voltage in standby mode with ANSYS Maxwell simulation verifies the proposed method. The experimental platform with a three-phase six-pole pairs alternator verified that the proposed method can detect rotational speed even in self-start and low speed of 200 rpm. [ABSTRACT FROM AUTHOR]

This paper presents a direct voltage control method for interior permanent magnet synchronous motors (IPMSMs) with a single speed regulator. The method achieves maximum torque per ampere (MTPA) operation by controlling the magnitude and the angle of the voltage vector. For that, the mathematical model for the MTPA trajectory of the IPMSM is derived in the voltage plane. As such, no current sensor is needed, which makes the proposed strategy tolerant to current sensors failure unlike cascaded control loop based methodologies. Although no current sensor is used, the control strategy tracks MTPA trajectory by taking into account both voltage and current limits of the machine. The complete MTPA derivation in the voltage plane is presented in this paper; but, only the final solution is needed for real-time implementation. Henceforth, the simplicity of the control scheme combined with its current sensor dependence free characteristics make it a good candidate for real-time implementation in vehicular applications. The concept is developed and evaluated experimentally on a 10-HP IPMSM. [ABSTRACT FROM AUTHOR]

A doubly-fed induction machine (DFIM) is a promising choice for the shipboard propulsion system (SPS) of a more-electric ship (MES) to increase the system safety level by employing less power electronics. In this paper, the detailed impedance model of DFIM-SPS is established, with a salient-pole synchronous generator (SPSG) acting as the power source and a DFIM functioning as the propulsion load. The impedance modelling of DFIM is carried out from the aspect of ac coupling between the stator and rotor circuits, which is easy for physical understanding. In addition, the back-to-back power converter (BTBPC) is regarded as controlled voltage sources with impedances in the equivalent circuit. The phase-locked loop (PLL) is a key element in influencing the system stability, and it is integrated to upgrade the system dq impedance model. Moreover, the impedance shaping effect caused by dc-bus voltage control is investigated. Nyquist stability criterion is employed for system small-signal stability analysis, which is implemented with respect to the DFIM operation mode and PLL controller effect, and the time-domain simulations are carried out to verify the stable operation of a 5 MW DFIM-SPS in Matlab/Simulink. Furthermore, the experimental verification is done on a 1.5 kW DFIM electric drivetrain platform. [ABSTRACT FROM AUTHOR]

As electric vehicles (EVs) are connected to the distribution power system, EV owners desire to charge their EVs economically, reliably, confidentially and without requiring major modification to the charging systems in their EVs. At the same time, the increasing EV connections to the distribution power system can increase the electric load demand and decrease the power quality (PQ) of the power system due to the charging current of the EV chargers. It is, therefore, necessary to devise novel strategies for the coordination of the connection of EVs at the distribution level. Although different control methods have been proposed previously, most of these solutions require costly advanced infrastructures and computational resources. In this paper, a charging control system (CCS) using a hierarchical decision-making (HDM) approach is devised that can be easily applied for the economical and reliable charging of commercial EVs with minor modifications while improving the PQ in the power grids. The HDM approach includes a primitive energy management strategy and an adaptive droop control for the real-time operation. A thorough investigation of the effectiveness of the proposed CSS to meet the major needs of EV owners while improving the PQ of the distribution network has been carried out. The results from the case studies show that the CCS can satisfy the preferences of the EV owners, while improving the PQ of distribution grids. Specifically, the CCS can meet the economical and reliable EV charging for the EV owners, and at the same time maintain the voltage deviation within the acceptable PQ limits. [ABSTRACT FROM AUTHOR]

Under the unbalanced condition of grid voltages, the second-order harmonic voltage ripple will appear on the DC bus of the three-phase PWM rectifier due to the existence of the negative sequence voltages. In addition, the total harmonic distortion (THD) of the grid currents will increase correspondingly. In this paper, the coupling mechanism between the DC bus voltage ripple and the grid harmonic currents is revealed. Based on the situation above, a grid harmonic current suppression method is proposed. Compared with existing methods, the proposed method has the advantages in the following three aspects. Firstly, the proposed method does not require either the extraction of positive/negative sequence or the positive/negative sequence current control, which can highly reduce the complexity of the system. Secondly, the grid current harmonics can be reduced by an improved proportional quasi resonant (IPQR) controller. Thirdly, the IPQR controller has little effect on the parameter design of the control system, which facilitates the control design. Finally, the experiments show the accuracy of the theoretical analysis and the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

This paper proposes a battery charger (BC) for electric vehicles based on sinusoidal-ripple-current (SRC) method. The SRC method is used as an advanced charging-discharging method. On the one hand, the sinusoidal current variations alternately change output active power of the BC, negatively affect AC-side terminal current of the BC, and therefore, cause a power quality problem. On the other hand, the output active and reactive powers must be regulated at constant values without any variations for participation in vehicle-to-grid technology. Thus, a particular topology is suggested and then a control system is precisely designed in order to implement SRC charging-discharging method and adjust the output active and reactive powers for vehicle-to-grid technology without the power quality problem. SRC method can also be used in online electrochemical impedance spectroscopy (EIS) for state of charge and state of health estimation in battery management. The proposed control system can also generate the SRC signals, suitable for online EIS, in a controlled way unlike the recently proposed BCs. The simulation and experimental results demonstrate the effectiveness of the proposed solution. [ABSTRACT FROM AUTHOR]

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]

On-road dynamic charging of electric vehicles by wireless power transfer (WPT) systems has emerged recently as a cost-saving means for modern transportation. Thus, maximizing power transfer efficiency is essential in the system design stage as well as during the operation. In addition, the voltage regulation of EV power bus, supplied by the power transfer system and battery, is needed for a long life of the battery. In this paper, these two requirements are fulfilled under varying EV driving conditions by a single control system applied to a wireless power transfer system. The control system simultaneously tunes the switching frequency of the primary side inverter and the conversion ratio of the secondary side converter to achieve the maximum possible efficiency. In addition, the system adjusts the duty cycle of the primary side inverter to regulate the output voltage. Furthermore, an allowable range for the optimal frequency is determined and imposed to the primary inverter to compensate the power factor reduction according to IEEE std-1547.1. The system needs just one dc/dc converter instead of two as reported in the literature, without any restriction in zero state and start-up conditions. The control system does not need any information of the coupling coefficient and compensating circuit elements. The system is applied to a 710 W experimental wireless power transfer setup. Extensive simulation and experimental results are presented to validate the proposed control system. [ABSTRACT FROM AUTHOR]

Hybrid energy storage systems (HESS) involves two or more energy sources with complementary electrical charge/discharge characteristics to provide both energy and power requirements of the load. This paper presents an improved frequency sharing control algorithm used along with average current mode control for battery/ultracapacitor (UC) hybrid system in the presence of delay. The control algorithms implemented in different digital platforms have a delay due to computation and sampling time. The presence of delay limits the bandwidth (BW) of inner current loops. At such reduced BW, the improved algorithm proposes to compensate the battery current loop error during transients by UC current loop since the latter is faster. This leads to faster settling of the output. The control algorithm has been implemented in a microcontroller, and the effect of delay time has been considered for controller design to ensure system stability. For efficient HESS operation for load demand at all times, an EMA has also been proposed to charge/discharge the UC for ensuring its nominal voltage. An experimental prototype of the overall system is designed, and the effectiveness of the proposed control algorithm over conventional algorithm has been demonstrated. [ABSTRACT FROM AUTHOR]

In single-phase AC charging system for electric vehicles (EVs), the single-phase pulse width modulation (PWM) rectifier with deadbeat predictive current control (DPCC) is characterized by fast current dynamic response and simple algorithm. However, in steady state, the performance of the DPCC is affected by the circuit parameters mismatch and control delay, which will result in the AC side power-factor degradation and the input current distortion. Moreover, the performance of dynamic response to load mutation can be improved, as the traditional DPCC adopted PI controllers in the voltage loop. In this paper, an improved deadbeat control method is proposed. In the current loop, the AC side voltage compensation parameter is proposed to improve the power factor and reduce the total harmonic distortion (THD). The voltage loop uses an active disturbance rejection controller (ADRC), which improves the dynamic performance of the system. The feasibility and effectiveness of the proposed deadbeat control method is verified by simulation and experimental results. [ABSTRACT FROM AUTHOR]

In this paper, the possibility of utilizing a wind turbine to recapture a portion of the kinetic energy losses of a car, irrespective of being a traditional car that is propelled by an internal combustion engine or an electric vehicle (EV) that is propelled by an electric motor, is appraised. To investigate the topic, a small wind turbine has been inserted at the back of the condenser of a car to recover a portion of the kinetic energy of wind passing through the condenser's crisscrossed bars. A portion of this wind is caused by wind existing outside the car, and the main portion is caused by the kinetic energy originating from the car movement. In the absence of the wind turbine, the wind passing through the condenser's crisscrossed bars hits the middle part of the car's chassis and loses its energy. Thus, not only the wind turbine uses a portion of the kinetic energy losses of the car to produce electricity but also, since it has been embedded at the back of the condenser, it has no impact on the aerodynamic coefficient of the car, i.e., it does not produce any extra resistive force. When the car is parked, and there is no kinetic energy resulting from the car movement, a small flow of wind available outside the car is converted into electricity stored in the car's battery. To realize the proposed scheme, a 100-W wind turbine, a permanent-magnet synchronous generator coupled to the turbine, and a novel built hybrid power generation system combining the wind-driven generator's output power with that of the car's battery have been embedded in an EV having a total weight of 1855 kg. Experimental measurements conducted under realistic operation of the EV are given that prove the traveling range of the EV and the power efficiency of the EV's power supply are enhanced by, 6.4 km and 0.2% respectively, by recovering only a portion of the kinetic energy losses of the EV. These two benefits also prove the novelty and contributions of this work in successfully recovering a portion of the kinetic energy losses of a car by using a small wind turbine embedded in the car. [ABSTRACT FROM AUTHOR]

Most fuel cell electric vehicles require wide voltage-gain DC–DC converters to increase and equalize the relatively low voltage of fuel cell stacks with DC link bus or energy-storage devices, such as supercapacitors or batteries. This paper proposes two new non-isolated DC–DC converters suitable for such applications, which can be extended to other electric vehicles as well. The proposed converters combine the main characteristics of both quadratic Boost and Ćuk converters, offering high step-up voltage and control simplicity using only one ground referenced active power switch. Additionally, the proposed topologies present reduced voltage stress across the active power switch when compared to other boost converters. Considerations about the design of the proposed converters will also be presented. Experimental results obtained using a laboratory prototype validate the effectiveness and feasibility of the proposed topologies and its suitability for fuel cell electric vehicles. [ABSTRACT FROM AUTHOR]

Regenerative braking energy feedback system (RBEFS) can effectively feed the regenerative braking energy (RBE) of the trains back to the ac power grid. This improves the economy of the urban rail transit system greatly. The RBEFS that is utilized for both recycling the RBE and controlling the voltage of the traction network is proposed in this paper. First, the structure of the medium voltage RBEFS with the higher recovery efficiency is presented, and its parameters are designed in detail. Then, the double closed-loop control strategy of the RBEFS is studied, which not only achieves unit power factor feedback but also stabilizes the voltage of traction network effectively. Finally, simulation based on MATLAB/Simulink, laboratory experiments, and the field test are used to verify the performance of the presented RBEFS. The simulation and experiments results show that the RBEFS is able to feed RBE back into the ac grid effectively and the power quality of its output current satisfies the requirements of grid connection, as well as mitigate the voltage rise of the traction network under different startup threshold perfectly. [ABSTRACT FROM AUTHOR]

Ultracapacitor (UC) based dc–dc power supplies are widely used for addressing surge power demands and to provide energy backup to critical loads. The conventional control techniques, such as unified control strategy, though ensure seamless mode transition, do not offer complete flexibility in charging and discharging controls which is crucial in UC-based backup systems. On the other hand, controls, such as independent switch control, though allow great flexibility in control, do not ensure seamless mode transition without appropriate mode-switch logic. This paper proposes a time-varying virtual resistance based mode transition control for independent switch control which not only ensures smooth, seamless transition between charging and discharging control modes but also ensures complete control over the mode transition durations. The proposed control is found to be robust to error mode identification as compared to introducing dead band between control modes. The proposed control is verified on a proof of concept experimental setup at a power level of $P_o=65$ W, voltage level of $V_g=26$ V with the dc–dc converter switching at $f_{\text{sw}}=100$ kHz. The performance comparison with PWM blocking method is also evaluated where the proposed control is found to work well. [ABSTRACT FROM AUTHOR]

In this paper, two commonly utilized control methods for active disturbance rejection are designed and evaluated in a column formation (i.e., convoy) application of ground vehicles. Specifically, a variable structure controller and a robust sign of the error controller are utilized to achieve inter-vehicle distance tracking despite 1) not measuring the preceding vehicle's velocity and 2) being subjected to environmental influences. Both controllers utilize headway (i.e., variable inter-vehicle distance based on vehicle velocity) to: 1) promote overall convoy stability and 2) utilize only the preceding vehicle's position measurement. The performance of the controllers are evaluated and analyzed on experimental scale vehicles in both on- and off-road settings. [ABSTRACT FROM AUTHOR]

Compared with energy storage equipment based on supercapacitors, flywheels, or lithium batteries, inverters have obvious advantages in installation space, cost, reliability, and service lifetime. For this reason, regenerative inverters are increasingly installed in the substations of urban rail transit systems. They have controllable operating characteristics, but their impact on the energy saving and railway operation cost has not been fully studied. In this paper, based on the typical application scheme of regenerative inverters, the operating characteristics of the inverter including power limitation, start working voltage, and virtual internal resistance are introduced at first. A simplified power system model containing regenerative inverters and trains has been built. The impact of operating characteristics on the amount of regenerative braking energy and its distribution is analyzed. The inverter operating characteristics are optimized by a cost function considering total energy consumption, brake shoes wear, and inverter expense. A case study based on a multiple-train scenario is presented to validate the cost-saving performance. The work is expected to provide some guides for the design and optimization of the traction power supply system with inverting substations. [ABSTRACT FROM AUTHOR]

The electrification of a forced induction system (FIS) has emerged as a feasible solution for low greenhouse gas emission and high fuel economy in passenger cars and light-duty trucks. A high-speed electric motor in conjunction with the conventional FIS has numerous benefits including better transient response and higher engine output power. A single-phase brushless dc (BLDC) motor possesses a number of attractive features for this application including high efficiency, low cost, robustness, and high-speed operation capability. However, it generates higher torque ripple than that of three-phase BLDC motor due to the lack of alternate phases and phase current distortion. This paper proposes a new torque ripple minimization control technique, which has a linearly decreasing reference voltage to regulate phase current. The analytical estimation and experimental results verify that the new control technique reduces the motor vibration while improving the maximum speed and the efficiency of the motor drive. [ABSTRACT FROM AUTHOR]

This paper presents a single-inductor multiple-input single-output (SI-MISO) boost converter with a deadbeat-based control method. The proposed deadbeat-based control has the capability to simultaneously conduct the power regulation from multiple inputs and the output voltage regulation for the SI-MISO boost converter. The advantages of the proposed method are less component count, lower system cost, compatibility for arbitrary number of inputs, fast response, and simplicity for implementation. Hence, the SI-MISO boost converter is a promising interface for the regulation of multiple energy sources as a standalone power system, which can be utilized in electric vehicle applications. To verify the performance of the proposed deadbeat-based control method, a laboratorial prototype of the SI-MISO boost converter is built. The steady-state and dynamic operations are investigated based on the prototype. The experimental results demonstrate that input power and output voltage of the SI-MISO boost converter can be effectively regulated by the proposed control method. The comprehensive comparison with the existing methods is conducted to further illustrate the advantages of the proposed deadbeat-based method. [ABSTRACT FROM AUTHOR]

In this paper, a comprehensive sliding mode control (SMC) loop design for single-phase interleaved totem pole (ILTP) power factor correction (PFC) converters in electric vehicle onboard charger applications is proposed. The major objectives of the proposed SMC are to improve the converter dynamics, ensure a tight output voltage regulation under fast load fluctuations, and maintain a unity power factor. The sliding mode coefficients are selected to ensure both small signal and large signal stability for the robustness of the converter in wide operating conditions. As verification to the proof-of-concept, a hardware prototype of a single-phase ILTP PFC is developed and tested to validate the effectiveness of loop design by the load transient tests. The steady state results exhibit a power factor >0.995 and total harmonic distortion <3% at 800 W load power. At a 25% step-change in load power, SMC achieves 80 ms settling time, which is approximately 200 ms faster than the conventional PI control. [ABSTRACT FROM AUTHOR]

Fuel cells have increasingly become an attractive option for providing clean electricity at relatively high efficiency. This paper discusses the key features of a proton exchange membrane fuel cell for a fuel cell-based auxiliary power unit (FC-APU) to supply a portion of electric loads in a vehicle. The FC-APU includes two converters: a unidirectional converter to control the fuel cell current and a bidirectional converter to control the dc-link voltage and battery current. This paper proposes 1) an energy management system (EMS) to manage the power transfer between the load and energy sources with emphasis on low stress on the fuel cell, 2) an iterative method to size the fuel cell and battery for a given load profile, based on the proposed EMS, and 3) a current estimator to reduce the effects of system transients on the dc-link voltage and increase system modularity. Simulation and experimental results validate the proposed EMS, sizing, and controller design. [ABSTRACT FROM PUBLISHER]

This paper presents the main operation modes for an electric vehicle (EV) battery charger framed in smart grids and smart homes, i.e., present-day and new operation modes that can represent an asset toward EV adoption are discussed and proposed, respectively. Apart from the well-known grid-to-vehicle (G2V) and vehicle-to-grid (V2G) operation modes, this paper proposes two new operation modes: home-to-vehicle (H2V), where the EV battery charger current is controlled according to the current consumption of the electrical appliances of the home (this operation mode is combined with G2V and V2G), and vehicle-for-grid (V4G), where the EV battery charger is used for compensating current harmonics or reactive power, simultaneously with the G2V and V2G operation modes. The vehicle-to-home (V2H) operation mode, where the EV can operate as a power source in isolated systems or as offline uninterruptible power supply to feed priority appliances of the home during power outages of the electrical grid, is presented in this paper and framed with the other operation modes. These five operation modes were validated through experimental results using a developed 3.6-kW bidirectional EV battery charger prototype, which was specially designed for these operation modes. This paper describes the developed EV battery charger prototype, detailing the power theory and the voltage and current control strategies used in the control system. This paper also presents experimental results for the various operation modes, both in steady state and during transients. [ABSTRACT FROM AUTHOR]

A fault protection and location method for ungrounded dc traction power systems is presented in this paper. Many dc traction power systems have an ungrounded power circuit to increase the leakage path resistance. Although ungrounded systems can continue operating with a single ground contact, unlike solid- or low-resistance grounded systems, because of the very low fault current, a second ground fault in another pole will result in a line-to-line fault that could cause significant system damage. However, it is difficult to detect the first ground contact due to the low ground current and even harder to locate because it can be seen by many detectors in the network. The proposed scheme in this paper uses a probe unit to detect and locate the first single ground fault in ungrounded traction power systems. The probe unit applies probe voltage to detect the fault and, once the fault is detected, analyzes the response to dc or swept-frequency ac probe voltage to locate the fault. The proposed concepts have been verified with computer simulations and hardware experiments and demonstrated a successful performance. [ABSTRACT FROM PUBLISHER]

A 12-V motor drive system using an onboard battery is promising in vehicle applications, e.g., to rotate an air pump to adjust its air delivery to the burner, thereby providing autonomous exhaust temperature control for the conventional diesel engine vehicle. The 12-V/1-kW motor drive system proposed in this paper consists of a series-resonant LLC MOSFET full-bridge converter, which provides high-efficiency power transfer by implementing zero voltage switching and boosts the dc bus to $\sim$300 V, and an insulated-gate bipolar transistor inverter, which provides the high-side phase currents to a 1-kW/6000-r/min brushless dc motor (BLDC). This design secures the high efficiency, low cost, and low volume. Meanwhile, with the variable output voltage of this dc/dc converter, this paper realizes a commutation torque-ripple reduction method, which will minimize the mechanical vibration. Experimental results on this prototype system demonstrate that: 1) the LLC dc/dc part efficiency is 97.6% with 92% of the inverter efficiency; and 2) the motor commutation torque ripple is reduced close to zero. [ABSTRACT FROM PUBLISHER]

This paper presents an adaptive radial basis function (RBF) network based speed control approach for interior permanent magnet synchronous machine (IPMSM) based vehicles. The presented control strategy achieves speed tracking without current measurement or control by acting directly on the machine's voltages. As a result, the current control loop is avoided, greatly simplifying the overall control strategy when compared to most existing speed control schemes. Moreover, no parameter knowledge is required unlike other control strategies. Furthermore, the closed-loop control system's stability is guaranteed by a Lyapunov theorem. Simulation and experimental results for different scenarios along with comparison against the well-established field oriented vector control technique demonstrate the controller's satisfactory behavior in both transient and steady state. The proposed method yields 99% and 97% tracking accuracy in the presence of parametric uncertainties and friction nonlinearities, respectively. [ABSTRACT FROM AUTHOR]

In this paper, an innovative method to minimize the intermediate dc-link capacitance in a cascaded two-stage combination of a three-phase six-switch power factor correction (PFC) and phase-shifted full-bridge (PSFB) dc/dc stage is introduced and analyzed. The proposed strategy has a significant impact on the minimization of the overall system weight and volume. Fundamentally, the method is based on minimizing the switching fundamental component of the dc-link current and is established by imposing a separate constraint on the phase duty ratios without compromising the unity PFC action. Furthermore, the control loop takes care of regulating the intermediate dc-link voltage along with the final output voltage. A 6 kW laboratory prototype of the integrated three-phase PFC and PSFB dc/dc as a part of auxiliary power unit in more-electric airplanes is developed and designed to validate the proposed algorithm. The experimental results show a conversion efficiency of 95.4% at full load, input total harmonic distortion of 4.1%, power factor of 0.998, output voltage ripple of ±1%, and a reduction of dc-link capacitor by 60%. [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 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]

This paper presents an integrated control strategy to achieve fast start-up and enable wide input frequency operation in a three-phase six-switch power factor correction (PFC) converter. Limiting the inrush current with simultaneously minimizing the start-up time is achieved by implementing a nonlinear compensator in the voltage control loop. In addition, the concerning issues regarding unity PFC operation with an accurate reference tracking in a system with wide input frequency variation (typical for more-electric-aircraft) are resolved by a second-order compensator integrated with a state-feedback controller in the current loop. For a proof-of-concept verification, a hardware prototype of 6 kW, three-phase six-switch PFC is developed and tested with the proposed integrated control strategy in a wide source frequency range (360–800 Hz) ac input that shows perfect unity power factor operation throughout. Both the start-up time and inrush current are reduced to < \text50\% of their values in conventional PI compensation. [ABSTRACT FROM AUTHOR]

A nonisolated single-stage on-board charger for electric vehicles has been proposed to increase system efficiency and power density in previous works. However, its ability to achieve high efficiency is limited by variations in the electric utility and battery, especially during the step-down operation. This paper proposes an advanced control algorithm that improves system efficiency in the step-down mode by controlling each switch asymmetrically using a phase-shift control. The proposed algorithm consists of only one controller, which prevents transient states from causing variations in the controller. The algorithm decreases the magnitude and ripple of the inductor current, which improves the charging efficiency by approximately 4.1% over at the 3.7-kW full load that of the conventional algorithm in the step-down mode, and measured total harmonic distortion and power factor are 3.2% and 0.995, respectively. [ABSTRACT FROM AUTHOR]

This paper proposes a novel integrated synchronous buck converter for the auxiliary power supply system of electric vehicles, which achieves multiple independently regulated outputs with reduced switching components in comparison with the conventional separate buck converters. In order to obtain a better understanding of the proposed converter, operational principle and performance characteristics of a simplified dual-output buck converter are introduced in detail, as an example. The analysis shows that zero-voltage-switching operation and lower conduction losses could be attained. In addition, its dynamic behavior is similar to the conventional buck converter and thus the controller design is simple. Finally, experimental results based on a prototype circuit in which two inductors are integrated into one magnetic core to achieve further reduced cost are demonstrated to verify the advantages. [ABSTRACT FROM PUBLISHER]

The number of electric vehicles (EVs) is expected to increase significantly in the future to combat air pollution and reduce reliance on fossil fuels. This will impact the power system. However, appropriate charging and discharging of EVs through vehicle-to-grid (V2G) operations could also provide support for the power system and benefits for EV owners. This raises the questions of when and how EV battery storage should be dispatched, taking into account both vehicle users' and power system's requirements and priorities, as well as the constraints of the battery system. This paper proposes a novel decentralized dispatch strategy based on the analytic hierarchy process (AHP), taking into account the relative importance of the different criteria, including cost, battery state of charge (SOC), power system contingency, and load leveling. The proposed AHP-based dispatch strategy was tested on an IEEE Reliability Test System with different EV numbers and capacities to investigate the efficacy of such an approach. The simulation results demonstrate the feasibility and benefits of this dispatch strategy. [ABSTRACT FROM PUBLISHER]

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]

Although great effort has been devoted with various approaches on the improvement in energy efficiency of electric vehicles, much of the focus has been on the design of electric devices and power electronic systems and of energy storage systems with energy management strategies. This paper proposes a bus voltage control method that actively and dynamically controls the bus voltage applied to the inverter through a dc/dc converter, such that it tracks the rotational speed of the motor, that aimed to improve the energy efficiency of the inverter, or the overall energy efficiency of power electronic systems. A detailed energy efficiency model is first developed that takes into account the inverter loss and motor iron loss. Some detailed and in-depth analyses on energy efficiency have been conducted that conclude that the inverter's energy efficiency is largely related to the voltage applied, and the voltage is further closely related to the rotational speed of the motor. Simulations and in-vehicle experiments under a New European Driving Cycle (NEDC) have been conducted that demonstrate the effectiveness of the proposed method on the improvement in energy efficiency of the inverter, as well as the system as a whole. [ABSTRACT FROM PUBLISHER]

This paper presents the ultracapacitors (U) and fuel-cell/lithium-battery connection with an original energy management method for hybrid electric vehicle (HEV) applications. The proposed method is focused on the frequency approach to meet the load energy requirement. The ultracapacitors are connected to the dc link through a buck–boost converter, and the fuel cell is connected to the dc link via a boost converter for the first topology. In the second topology, the lithium battery is connected to the dc link without a converter to avoid the dc-link voltage control. An asynchronous machine is used like the traction motor; it is related to the dc link through a dc/ac converter (inverter). The main contribution of this paper is focused on HEV energy management according to the dynamics (frequency) of the hybrid sources using polynomial correctors. The performances of the proposed method are evaluated through some simulations and the experimental tests, using the New European Driving Cycle (NEDC). This study is extended to an aggressive test cycle, such as the U.S. driving cycle (USDC), to understand the system response and the control performances. [ABSTRACT FROM PUBLISHER]

The main advantage of asymmetrical multilevel inverters is the optimization of levels with a minimum number of power supplies. However, this optimized multilevel system still needs a large number of isolated and floating dc supplies, which makes these converters complicated to implement in electric vehicles (EVs), because the system will require many independent battery packs. In this paper, a very simple scheme, based on a small and cheap high-frequency link (HFL), allows the utilization of only one power supply for the complete multilevel inverter drive, with an inherent regulation of the voltages supplied among the H-bridges. It also allows voltage control with the full number of levels if the dc source is of a variable voltage characteristic. This paper is focused on a 27-level asymmetric inverter, but the strategy, using only one power supply, can be applied to converters with any number of levels. In particular, an asymmetrical 27-level converter needs nine isolated power supplies, and the proposed system reduces these nine sources to only one: the battery car. The topology also permits full regenerative braking working as a three-level converter. The proposed system is intended for application in EVs from power ratings up to 150 kW. Simulations and experimental results show the feasibility to implement this “one-source” multilevel system. [ABSTRACT FROM PUBLISHER]

This paper suggests a hybrid pulsewidth-modulation (PWM) dc/dc converter for an electric vehicle (EV) on-board charger (OBC). It is composed of a full-bridge (FB) converter and a resonant converter with secondary resonance tank (SRT). They are coupled in a single transformer so that any power distribution problem that causes a size increase in the transformer can be solved. Dual power flow of the proposed charger provides an increase in charger gain and a reduction of turn-off voltage spikes of the rectifying diodes caused by transformer leakage inductance and diode junction capacitance. These characteristics help reduce diode loss and remove dissipative snubber circuitry. In addition, this structure has the additional advantage of output inductor size due to the reduction of voltage variation applied to the inductor. The feasibility of the proposed charger is verified with a 6.6-kW prototype implemented by a design procedure. [ABSTRACT FROM PUBLISHER]

Rapid growth in the deployment of electric vehicles (EVs) is creating opportunities for system operators to improve the reliability and sustainability of electricity delivery system, while reducing the operating cost. EVs can respond quickly, improve system stability, and provide reactive power support without battery wear. Therefore, EVs could be a promising source of reactive power when they are connected to smart charging equipment. However, under certain scenarios, reactive power support may raise the vehicle charging cost by shifting part of charging power to times of the day when the price of electricity is higher. Participation of EVs in an ancillary service market for reactive power will thus require some level of compensation for EV owners. In this paper, we present a framework for the calculation of reactive power supply function for EVs. We define an objective function representing charging/discharging cost of EVs and then minimize the cost under realistic constraints. An algorithm is then introduced that extracts the EV's supply function for providing on-demand reactive power service at minimum cost. Thus, the system operator can include EVs, as reactive power service providers (RPSPs) along with other service providers, to meet the on-demand need of the reactive power. Simulation results indicate the EV's ability to provide reactive power service during on-peak periods, when the system operator's need for reactive power is most likely high, at almost no cost to the EV owner. [ABSTRACT FROM PUBLISHER]