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This paper presents a new soft switching high voltage gain interleaved dc-dc converter with a three-windings coupled inductor for a fuel cell vehicle. Two interleaved and intercoupled boost cells are connected by the input parallel and output series (IPOS) configuration, realizing low input current ripple and high voltage gain simultaneously. All power switches can operate under soft switching conditions by only adding a simple auxiliary circuit composed of one auxiliary inductor and one power switch. Besides, the auxiliary inductor is coupled with the main inductors, which results in a rapid zero convergence of the auxiliary current and a small conduction loss of the auxiliary circuit. The operating principle, steady state characteristic, comparison with other converters, and parameter design are analyzed in this paper. Finally, the main characteristics of the proposed converter are verified by a 1-kW laboratory prototype. [ABSTRACT FROM AUTHOR]

Miniaturization and low cost contribute to the development and popularization of wireless power transfer (WPT). Reducing the number of power conversion stages can reduce the volume and cost of the WPT converter, and even make it possible to improve the efficiency. A single-stage WPT converter with constant current (CC) and constant voltage (CV) output and its asymmetric modulation method are proposed in this paper. A direct AC-AC converter is applied to the primary side of the WPT converter to directly convert line-frequency AC to high-frequency AC. The applied direct AC-AC converter that can replace the commonly used multi-stage primary converter reduces the number of circuit devices, thereby reducing the volume and cost of primary converter. The proposed WPT converter can realize zero voltage switching (ZVS) and power factor correction (PFC). In order to achieve CC and CV output, a switchable hybrid compensation topology is applied to the proposed WPT converter. A 720-W experimental prototype was manufactured to verify the rationality of the proposed WPT converter and the correctness of the theoretical analysis. [ABSTRACT FROM AUTHOR]

The DC-DC converter for fuel cell vehicles should be characterized by high-gain, low voltage stress, small size and high-efficiency. However, conventional two-level, three-level and cascaded boost converters cannot meet the requirements. A new non-isolated DC-DC converter with switched-capacitor and switched-inductor is proposed in this paper, which can obtain high-gain, wide input voltage range, low voltage stresses across components and common ground structure. In this paper, the operating principle, component parameters design, and comparisons with other high-gain converters are analyzed. Moreover, the state-space averaging method and small-signal modeling method are adopted to obtain the dynamic model of converter. Finally, simulation and experimental results verify the effectiveness of the proposed topology. The input voltage of the experimental prototype ranges from 25 V to 80 V. The rated output voltage is 200 V and rated power is 100W. The maximum efficiency is 93.1% under rated state. The proposed converter is suitable for fuel cell vehicles. [ABSTRACT FROM AUTHOR]

This paper presents a reduced-stage three-phase isolated AC/DC converter topology used for auxiliary power units (APUs) in avionics and electric vehicle (EV) applications. Traditional two-stage cascaded AC/DC converters are widely used for these applications due to their ease of implementation and simple control schemes. With the objective of improving the power density of the APUs, the proposed converter achieves reduction in the number of active power devices along with a smaller DC link capacitance by implementing an unconventional structure with a bandpass filter, to allow only the required frequency components to transfer the rated power. To accurately characterize the proposed converter, a detailed formulation of the filter design for the circuit along with mathematical derivation of the control scheme is presented. In terms of achieving enhancement in the overall efficiency, a comparative study is presented that focusses on the conduction and switching losses incurred in the proposed topology as compared to the state of the art (SOA) two-stage AC/DC conversion topologies. The analyses portray efficiency improvement of 0.8% for a 6 kW rated load, with significant reduction in active device losses. Additionally, to support the formulations and derivations, simulation studies and experimental verifications are also presented. The results show an input power factor of 0.9918 (lagging) with a conversion efficiency of 97.6%, a tightly regulated output voltage with less than 1% peak-peak ripple and the input current total harmonic distortion (THD) of as low as 1.57%. [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]

Using a practical relay model, in which an energy transmitter (ET) transmits energy to a sensory node S and an information receiver D, information freshness or age of information (AoI) under outdated-channel-state-information (oCSI) severity and line-of-sight (LoS) power is examined in this paper. The sensory node—equipped with a finite-size-battery capacitor—harvests energy from the ET to sustain its operation. Rician fading under non-oCSI and oCSI environments is employed to study the AoI, in which benefits and severity of LoS power and oCSI will be elaborated. The proposed AoI results exactly reduce to existing ones under Rayleigh fading, which validates this work. Simulation results are additionally deployed to validate the proposed AoI results. Impact of parameters such as capacitor capacity, system incoherence coefficient and spectral efficiency on AoI under specific scenarios is also discussed. [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 proposes a new topology-reconfigurable capacitive compensation network, aiming to achieve the energy encryption of the contactless charging for multiple electric vehicles (EVs). The proposed variable topology of compensation network consists of an M × N capacitor matrix, where capacitors can be connected either in series or in parallel by controlling switches. Then, the proposed capacitor matrix can be formed in the series-parallel and the series-parallel–series-parallel topologies according to the adjustment of the resonant frequency. In such ways, the proposed topology-reconfigurable capacitor matrix can significantly extend the capacitive compensating range while reducing the number of capacitors, thus effectively enhancing the security performance of multiple-objective contactless charging systems. Finally, this paper gives the simulated and experimental results to verify the theoretical analysis, which can further illustrate the feasibility of the proposed topology-reconfigurable capacitor matrix for the energy encryption of EV contactless charging systems. [ABSTRACT FROM AUTHOR]

This paper proposes a current-fed single-phase inverter without constant intermediate DC link. It eliminates electrolytic capacitor from the DC-link and introduces an intermediate pulsating DC bus. The proposed topology is modular with three full-bridges making it scalable for high-power applications. New pulsating-DC-modulation for back-end pulsating DC-link inverter and secondary modulation (SM) for front-end DC-to-pulsating DC converter is proposed. Soft-switching and device voltage clamping of both primary side and secondary side devices of front-end current-fed full-bridge converter is realized. A rotating partial hybrid pulsewidth modulation has been introduced. One leg of inverter is commutated at a low switching frequency, while the other leg is operated at a high switching frequency for partial period of a line frequency cycle. Thus, switching losses of the back-end inverter are considerably reduced. Rotating mechanism is used to equalize the switching losses of four switches of the inverter. This paper presents detailed operation and analysis of the topology with a proposed modulation scheme. Simulation and experimental results validate the effectiveness and accuracy of the proposed modulation scheme as well as soft-switching and performance of the converter. [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]

The essential features of a DC–DC converter for fuel cell vehicle are to ensure the higher voltage gain to meet out the higher DC link voltage demand, continuous input current to improve the life span of the fuel cell, presence of common grounding to avoid electromagnetic interference issue and lower voltage stress with reduced components. This paper presents a high voltage gain DC–DC converter by combining the switched capacitor and quasi switched boost network modules. The proposed high voltage gain converter provides the continuous input current, lower voltage stress, utilizes a fewer number of elements and common grounding feature. The operating characteristics, steady-state analysis both in continuous current mode (CCM) and discontinuous current mode (DCM), comparative analysis with contemporary converters are discussed. The theoretical claimed analysis is validated by the simulation and experimental study. The proposed converter is operated for 200 W output power rating and tested for providing the voltage gain in the range of 5–8 times the input voltage gain by varying the input voltage from 25 V–40 V. The efficiency of the proposed converter is also reported for different output power rating which is in the range 91.3%–93.7%. [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]

Lithium-ion capacitors (LiCs) have emerged as a promising technology for automotive applications due to the solution offered by their power density, high voltage operation and their excellent durability (more than 2 million cycles). Nevertheless, the reliability of LiCs can be drastically affected by overheating issues which raise the importance of thermal management. Nowadays, active cooling is employed to keep the battery systems temperature in range. However, due to the bulkiness and weight of the existing active cooling systems, latent heat thermal energy storage through the use of phase change materials (PCMs), represents an attractive way. In this paper, paraffin is investigated experimentally and simulated as a PCM cooling solution for the thermal management of a dual-LiC module. Moreover, since paraffin presents a low thermal conductivity characteristic, an additional component such as aluminium mesh grid is inserted to the system to solve the low conductivity issue. Results show good performance of the Al-PCM on the battery thermal management for both ESSs with a relatively lower temperature. The Al-PCM combination was able is lower the temperature to 36 °C compared to natural convection (46 °C). [ABSTRACT FROM AUTHOR]

LLC topology demonstrates optimal efficiency near its resonant frequency, where its normalized voltage gain is close to unity. However, in plug-in electric vehicle (PEV) charging applications, the voltage gain of the LLC converter needs to vary in a wide range. This makes the switching frequency deviate away from the resonant frequency. In this paper, an improved LLC-based PEV charger is proposed to cope with this challenge. The proposed converter adopts a reconfigurable two-level turns-ratio transformer. With the increase of output voltage, the transformer secondary side reconfigures from low turns to high turns. Thus, the switching frequency range can be effectively squeezed around the resonant frequency in constant current charging stage. In constant voltage charging stage, the switching frequency of the LLC converter is exactly tuned to the resonant frequency. Therefore, the overall efficiency can be enhanced over the entire charging process. The design considerations of the proposed PEV charger are addressed in detail. A 1.35-kW prototype to charge a 250–450 V battery pack is designed and tested both in steady state and dynamically. The prototype demonstrates 97.47% peak efficiency and enhanced efficiency performance over the wide output range. [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]

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]

In order to use the dynamic low-voltage fuel cell stack in a fuel cell vehicle with a constant high voltage (400 V) dc bus, a capacitor-clamped H-type boost dc-dc converter with a wide voltage gain is proposed in this paper. In the input-voltage side, a capacitor clamped H-type structure is adopted to reduce input current ripple, avoid narrow-pulse of pulsewidth modulation voltage waveforms, and decrease the conduction loss of power switches; while in the output-voltage side, a switched-capacitor structure is adopted to achieve high voltage gain and decrease the voltage stress of all power semiconductors and capacitors. The operating principle, characteristic, control strategy, parameters design, and comparison with other converters are analyzed, and a 400 W prototype is developed. As a result, the converter can transform low-voltage from 25 V to 70 V in to 400 V with a wide voltage-gain range, which maximum efficiency is 94.72%. The experimental results also validate the aforementioned characteristics of the proposed converter and the correctness of theoretical analysis. This converter is suitable to serve as power interface for fuel cell vehicles. [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]

To improve reliability and realize electric isolation, an integrated topology of the charger and drive for medium/high-power electric buses is presented in this paper. The proposed integrated topology can solve the voltage matching problem between the power grid and the battery voltage and between the battery voltage and the drive system. The integration can be realized by using the common hardware of the charging system and the drive system, which can reduce the cost and weight of the whole system. To improve the power level, a three-phase combined full-bridge converter based on the magnetic-combination transformer is adopted in the charging system, which has a single-stage power-factor-correction function, electric isolation, and no electrolytic capacitor. To better reflect the integration, the motor drive system adopts a single-stage boost dual-inverter that is the reconfiguration of the magnetic-combination transformer and the 3-H bridge converter in the charging system and few extra components. The drive system has a single-stage boost/buck function, high reliability, and strong fault-tolerant ability. The proposed integrated topology, which can realize a charging function and a driving function, has been analyzed in this paper. Finally, the experimental results verify the feasibility of the integrated topology. [ABSTRACT FROM PUBLISHER]

Wireless power transfer (WPT) is an emerging technology that can realize electric power transmission over certain distances without physical contact, offering significant benefits to modern automation systems, medical applications, consumer electronics, etc. This paper provides a comprehensive review of existing compensation topologies for the loosely coupled transformer. Compensation topologies are reviewed and evaluated based on their basic and advanced functions. Individual passive resonant networks used to achieve constant (load-independent) voltage or current output are analyzed and summarized. Popular WPT compensation topologies are given as application examples, which can be regarded as the combination of multiple blocks of resonant networks. Analyses of the input zero phase angle and soft switching are conducted as well. This paper also discusses the compensation requirements for achieving the maximum efficiency according to different WPT application areas. [ABSTRACT FROM PUBLISHER]

This paper proposes a novel double-grid-frequency-ripple-reducing technique for electric vehicle (EV) battery charger applications. In 1- $\phi$ EV battery chargers, due to double-frequency ripple, it is not possible to control the current using a single-power-stage approach. Hence, a two-stage approach is used. However, a bulky inductor and a capacitor are required to control the current, which adds to the system's weight and cost. The single-stage charging system described in this paper can charge the battery with almost ripple-free current without using a bulky electrolytic capacitor. At the same time, it can maintain high power factor (PF) and low total harmonic distortion on the input ac side. The proposed ripple compensation solution is realized by an innovative combination of boost and zeta converters connected in series with the battery charger, which reduces the filter capacitor value considerably. This facilitates the use of a film capacitor, which has a much longer life compared with an electrolytic capacitor. Similarly, the value of the filter inductor used in series with the battery is reduced significantly. Battery ripple current is not increased in the process; therefore, the battery life remains unaffected. Representative analytical, simulation, and experimental results are presented. [ABSTRACT FROM AUTHOR]

In the rapidly growing field of electrified transportation technology, hybrid electric and electric vehicle (HEV/EV) manufacturers have been placing increasing demands on the designers to improve the efficiency and reduce the costs of vehicle components to sustain a niche in the EV market. To understand the significance and challenges in an efficient and economical drivetrain design, this paper presents a part of an ongoing project that aims at developing a comprehensive study on dc/ac drive motor technology in EV applications. In this paper, a new three-level three-phase matrix converter topology, along with two conventional frequently used three-level three-phase dc/ac converter topologies, namely, diode-clamped and H-bridge converters, are implemented. Furthermore, comprehensive analysis and comparative studies are conducted to examine the performance and efficiency of these converter topologies according to EV design criteria. In addition, experimental investigations are carried out on the aforementioned converter configurations to help EV designers choose the most suitable converter topology. [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]

To overcome the problem that the balancing performance of existing switched-capacitor (SC) cell balancing systems drops along with the increase in the number of series-connected battery cells, a novel SC cell balancing circuit is presented in this paper. The same as other SC balancing systems, only a pair of complementary square-wave signals is required to control the proposed circuit. With resonant SC design, all switches employed in the proposed balancing circuit operate under zero-current switching. The equivalent model is derived to reveal the balancing performance of the proposed balancing circuit. The system feasibility and theoretical analysis are verified by both of simulation and experimental results. [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]

Electric vehicle technology has been adopting fuel cells (FCs) for hybrid applications over the past few years. Therefore, the development of advanced power electronic systems for the integration of fuel cells with on-board energy management is fundamental for achieving high-performance systems. An FC for vehicular applications is usually a low-voltage current-source like device that produces electricity and heat directly from input hydrogen and oxygen. Most often, it is required that the FCs be stacked for high-voltage dc-link in order to supply the input power for the drivetrain and electric motor drive system. The FC has a nonlinear nature, and it must be controlled to operate in the high-efficiency operating range. Hybrid electric vehicles have physical constraints such as volume and weight under limited cost and expected lifetime. There is a need for high-voltage input/output ratio of dc-dc boost converters to be connected between the FC to the motor drive dc-link. In addition, it is necessary to have low input ripple at the dc-dc boost converter in order to maximize the FC lifetime, and the traditional dc-dc boost converter topologies have poor performance on these specifications. This paper proposes a new dc-dc converter family of topologies aimed at improving the application to electric vehicle power control. This family is defined as floating-interleaving boost converters (FIBCs). The paper will thoroughly show analysis and experimental verification of FIBC's, and they will be compared with conventional boost converter characteristics. The paper supports how performance figures related to the passive components, i.e., the inductor and capacitor, will have better volume and weight, extremely low input current ripple, and improved efficiency and transfer ratio. The analysis presented in this paper shows how to choose the most suitable topology in order to achieve the desired specifications. The selected topology is fully validated experimentally using advanced nonlinear sliding mode control, which has the additional feature of operating even in faulty conditions. [ABSTRACT FROM PUBLISHER]

The aim of this paper is to present the practical control structure (PCS) and energy management strategy of a testbed hybrid electric vehicle (HEV). This vehicle is equipped with batteries, a supercapacitor system, and a fuel cell system (FCS). The PCS, based on the energetic macroscopic representation methodology, is used to evaluate and compare the different energy management strategies to be implemented in the vehicle. This paper introduces a dynamic strategy to manage the energy in the hybrid electric vehicle; this strategy uses a fuzzy logic controller and considers the slow dynamics in the FCS, the vehicle speed, and the state of charge in the supercapacitors. [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]

This paper compares the characteristics of the series–series and double-sided Inductor-Capacitor-Capacitor (LCC) compensation topologies for electric vehicle (EV) wireless chargers. Both the well-tuned and mistuned topologies for the two compensation methods are analyzed in detail. The mistuning considered here is mainly caused by the variations of the relative position between the primary and secondary sides. The output power displacements caused by mistuning are compared for both compensation topologies, as well as the impacts of the load variations on the performances of the mistuned topologies. The voltage and current stresses on components are also studied. The comparative result shows that the double-sided LCC compensation topology is less sensitive to mistuning. A double-sided LCC-compensated EV wireless charger system with up to 7.7-kW output power is built to verify the analysis results. A peak efficiency of 96% from dc power source to battery load is achieved. [ABSTRACT FROM PUBLISHER]

Electric vehicles based on high-energy lithium-ion batteries often exhibit a substantial loss in performance at subzero temperatures: Due to slower electrochemical kinetics, the internal resistances of the batteries rise and diminish available power and capacity. Hybrid energy storage systems (HESSs) can be used to overcome these weaknesses. In this paper, the performance of two HESSs, combining a high-energy lithium-ion battery with either a high-power lithium-ion battery or a lithium-ion capacitor, has been investigated experimentally for a driving scenario at various temperatures. Both configurations enable driving at -20 °C, which was not possible without hybridization. The HESS using the high-power lithium-ion battery provides a substantially higher driving range due to its higher energy density. An analysis of different operating strategies has helped to maximize the driving range: Discharging the high-energy battery with a constant current and keeping the high-power cell at a higher state of charge (SoC) extend the driving duration, as the requested driving power can still be provided at a lower SoC of the high-energy battery. In addition to the HESSs, two energy storage systems without hybridization, consisting of different generations of high-energy lithium-ion cells, have been examined to disclose improvements in battery technology. These improvements narrow the benefits of HESSs, as the high-energy batteries have become less reliant on the support of an additional high-power device. Although HESSs lose importance for current lithium-ion battery systems, they can be a valuable option for next-generation lithium batteries, which are expected to provide higher energy densities but exhibit reduced rate capability. [ABSTRACT FROM AUTHOR]

This paper provides a detailed comparative analysis of optimal sizing of battery-only, ultracapacitor-only, and battery–ultracapacitor hybrid energy storage systems (ESSs) for a plug-in electric city bus (PECB). It is shown how the configuration affects the optimal size of the ESS. The problem of optimal sizing of the storage system for the PECB is formulated and solved for a specific set of vehicle parameters, battery, and ultracapacitor cell data, as well as a specific daily drive cycle. A modified particle swarm optimization algorithm is used to solve the optimal sizing problem. The optimization platform developed by the authors and used for this study is highly flexible and accepts different component data, vehicle parameters, and drive cycles as the input for determining the optimal sizes of the storage system. [ABSTRACT FROM PUBLISHER]

This paper proposes a double-sided LCC compensation network and its tuning method for wireless power transfer (WPT). With the proposed topology and its tuning method, the resonant frequency is irrelevant with the coupling coefficient between the two coils and is also independent of the load condition, which means that the system can work at a constant switching frequency. Analysis in frequency domain is given to show the characteristics of the proposed method. We also propose a method to tune the network to realize zero voltage switching (ZVS) for the Primary-side switches. Simulation and experimental results verified analysis and validity of the proposed compensation network and the tuning method. A wireless charging system with output power of up to 7.7 kW for electric vehicles was built, and 96% efficiency from dc power source to battery load is achieved. [ABSTRACT FROM PUBLISHER]

Silicon carbide (SiC)-based switching devices provide significant performance improvements in many aspects, including lower power dissipation, higher operating temperatures, and faster switching, compared with conventional Si devices. However, tradeoffs in efficiency, size, and weight between Si- and SiC-based converters are still unclear in the literature. In this paper, a bidirectional dc–dc converter that is suitable for hybrid or electric vehicle application is studied based on three sets of device combinations, e.g., all-silicon [conventional silicon insulated-gate bipolar transistors (IGBTs) and silicon PN diodes], hybrid (silicon IGBTs with SiC Schottky diodes), and all-SiC (SiC metal–oxide–semiconductor field-effect transistors with SiC Schottky diodes). At the switching frequency of 20 kHz, comparative analyses regarding the power loss reduction of power devices and efficiency improvements are carried out for the converters. Possible size and weight reduction is also investigated by increasing the operating frequencies of hybrid and all-SiC converters while reducing the capacitance and inductance values. [ABSTRACT FROM PUBLISHER]

In this paper, a two-stage onboard battery charger is analyzed for plug-in electric vehicles (PEVs). An interleaved boost topology is employed in the first stage for power factor correction (PFC) and to reduce total harmonic distortion (THD). In the second stage, a full-bridge LLC-based multiresonant converter is adopted for galvanic isolation and dc/dc conversion. Design considerations are discussed, focusing on reducing the charger volume and optimizing the conversion efficiency over the wide battery-pack voltage range. A detailed design procedure is provided for a 1-kW prototype, charging the battery with an output voltage range of 320–420 V from 110-V 60-Hz single-phase grid. Experimental results show that the first-stage PFC converter achieves THD of less than 4% and a power factor higher than 0.99, and the second-stage LLC converter operates with 95.4% peak efficiency and good overall efficiency over wide output voltage ranges. [ABSTRACT FROM PUBLISHER]

In this paper, an inductor–inductor–capacitor (LLC) resonant dc–dc converter design procedure for an onboard lithium-ion battery charger of a plug-in hybrid electric vehicle (PHEV) is presented. Unlike traditional resistive load applications, the characteristic of a battery load is nonlinear and highly related to the charging profiles. Based on the features of an LLC converter and the characteristics of the charging profiles, the design considerations are studied thoroughly. The worst-case conditions for primary-side zero-voltage switching (ZVS) operation are analytically identified based on fundamental harmonic approximation when a constant maximum power (CMP) charging profile is implemented. Then, the worst-case operating point is used as the design targeted point to ensure soft-switching operation globally. To avoid the inaccuracy of fundamental harmonic approximation approach in the below-resonance region, the design constraints are derived based on a specific operation mode analysis. Finally, a step-by-step design methodology is proposed and validated through experiments on a prototype converting 400 V from the input to an output voltage range of 250–450 V at 3.3 kW with a peak efficiency of 98.2%. [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]

An onboard charger is responsible for charging the battery pack in a plug-in hybrid electric vehicle (PHEV). In this paper, a 3.3-kW two-stage battery charger design is presented for a PHEV application. The objective of the design is to achieve high efficiency, which is critical to minimize the charger size, charging time, and the amount and cost of electricity drawn from the utility. The operation of the charger power converter configuration is provided in addition to a detailed design procedure. The mechanical packaging design and key experimental results are provided to verify the suitability of the proposed charger power architecture. [ABSTRACT FROM PUBLISHER]

Plug-in hybrid electric vehicles (PHEVs) will play a vital role in future sustainable transportation systems due to their potential in terms of energy security, decreased environmental impact, improved fuel economy, and better performance. Moreover, new regulations have been established to improve the collective gas mileage, cut greenhouse gas emissions, and reduce dependence on foreign oil. This paper primarily focuses on two major thrust areas of PHEVs. First, it introduces a grid-friendly bidirectional alternating current/direct current ac/dc–dc/ac rectifier/inverter for facilitating vehicle-to-grid (V2G) integration of PHEVs. Second, it presents an integrated bidirectional noninverted buck–boost converter that interfaces the energy storage device of the PHEV to the dc link in both grid-connected and driving modes. The proposed bidirectional converter has minimal grid-level disruptions in terms of power factor and total harmonic distortion, with less switching noise. The integrated bidirectional dc/dc converter assists the grid interface converter to track the charge/discharge power of the PHEV battery. In addition, while driving, the dc/dc converter provides a regulated dc link voltage to the motor drive and captures the braking energy during regenerative braking. [ABSTRACT FROM PUBLISHER]

This paper presents a fuel cell (FC)–supercapacitor traction drive and its power control. The proposed solution allows increasing efficiency and performances of an FC-based powertrain by means of a dual cascaded voltage source inverter and a supercapacitor bank. An optimal control algorithm allows avoiding the fast transition of the FC output power under whatever operating condition. It is based on five operation modes, which are selected as a function of the actual traction power request. This way, both power peaks and slopes are controlled during vehicle accelerations. A supercapacitor charge stabilization strategy, which uses the same cascaded converter power circuit, is also proposed. Experimental implementation has been performed for validation. [ABSTRACT FROM PUBLISHER]

This paper presents a high-gain boost converter (three-level converter and transformerless converter) for fuel cell (FC) vehicle applications. An original nonlinear control law based on the flatness principle for distributed dc generation is studied. Utilizing the flatness property, we propose simple solutions to the system performance and stabilization problems. The design controller parameters are straightforward and autonomous at the operating point. To validate the proposed method, a prototype FC power converter (1.2-kW three-level boost converter) is developed in the laboratory. The proposed control law is implemented with a digital estimate in a dSPACE 1104 controller card. The experimental results from the laboratory using a 1200-W and 46-A polymer electrolyte membrane FC (PEMFC) verify that this is a good control scheme. [ABSTRACT FROM PUBLISHER]

This paper presents a method to control the current of each battery cell in a serially connected battery stack according to each cell capacity. With this method, the performance of a battery stack can be increased significantly. In a second life concept, battery cells with different capacities and even battery cells with different chemistries can be connected together. Moreover, if one or more battery cells become inoperative, then the battery stack can still be used in the limp-home operation mode. The required power converter structure and the calculation of the individual cell currents are presented, and a simulation for two different power converters during discharging and charging is performed. A current equalization prototype is used to validate the simulation results and to show the performance on a real battery stack with 12 serially connected cells. Finally, the influence of the equalization currents and the capacity variance in the battery stack on the discharging energy are investigated. [ABSTRACT FROM PUBLISHER]

The cell voltage imbalance of series-connected energy storage cells, such as supercapacitors (SCs) and lithium-ion cells, causes premature deterioration and a decrease in the available energies of the cells. Various equalization techniques have been developed for diminishing such imbalances. However, since the number of switches, sensors, and/or multiwinding transformers present in conventional equalizers is directly proportional to the number of series connections of the cells, the circuit complexity and cost of the equalizers are prone to increase with the number of series connections. In this paper, single-switch cell voltage equalizers using multistacked buck-boost converters, such as the single-ended primary inductor converter (SEPIC), Zeta, and Ćuk converters, are proposed. These equalizers consist of passive components and a single switch, significantly reducing the complexity of the circuit when compared with that of conventional equalizers. In addition, when the proposed equalizers operate in discontinuous conduction mode, feedback control is not required to limit currents flowing through cells and circuit components. The proposed equalizers are compared with conventional topologies in terms of the number of active and passive components required. Operating analyses were conducted under both cell-voltage-balanced and -imbalanced conditions. Experimental equalization tests were performed for four series-connected SCs using the SEPIC-based single-switch equalizer. The energies of the series-connected SCs were preferentially redistributed by the equalizer to the cell(s) having the lowest voltage, resulting in the elimination of the cell voltage imbalance and subsequent uniformity of the cell voltages. [ABSTRACT FROM PUBLISHER]

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]

Various types of cell voltage equalizers that exchange charges among cells have been proposed for series-connected lithium-ion cells. During equalization, cells are possibly cycled not only over a conventional period that ranges from seconds to hours but at a high frequency that is equal to the operating frequency of the equalizers as well. This paper investigates how the high-frequency cycling occurs and the factor that affects the life performance of the cells during high-frequency cycling. Experiments on charge–discharge cycling at frequencies of 1–100 kHz were performed for lithium-ion cells. The capacity of cells cycled at frequencies below 10 Hz significantly deteriorated, whereas the capacity decay of cells cycled at higher frequencies were identical to the corresponding calendar degradation. Simulation analyses revealed that the cycling current at high frequencies served only to charge and discharge the double-layer capacitance C \rm dl, whereas the current that flows through the charge-transfer resistance Rct, indicating the charge-transfer process, dominated at low frequencies. A correlation between the degradation trend and current distribution to Cdl and Rct was observed, implying that the calendar degradation and the degradation due to the charge-transfer process were the major causes of capacity decay in the frequency range below 10 Hz. [ABSTRACT FROM PUBLISHER]

This paper presents an energy management method in an electrical hybrid power source (EHPS) for electric vehicular applications. The method is based on the flatness control technique (FCT) and fuzzy logic control (FLC). This EHPS is composed of a fuel cell system as the main source and two energy storage sources (ESSs)—a bank of supercapacitors (SCs) and a bank of batteries (BATs)—as the auxiliary source. With this hybridization, the volume and mass of the EHPS can be reduced, because the high energy density of BAT and high power density of SC are utilized. In the proposed novel control strategy, the FCT is used to manage the energy between the main and the auxiliary sources, and the FLC is employed to share the power flow in the ESS between the SC and the BAT. The power sharing depends on the load power and the state of charge of the SC and the BAT. EHPS is controlled by the regulation of the stored electrostatic energy in the dc buses. The main property of this strategy is that the energy management in the power source is carried out with a single general control algorithm in different operating modes, consequently avoiding any algorithm commutation. An EHPS test bench has been assembled and equipped with a real-time system controller based on a dSPACE. The experimental results validate the efficiency of the proposed control strategy. [ABSTRACT FROM PUBLISHER]

This paper presents the analysis and novel controller design for a hybrid switched-capacitor bidirectional dc/dc converter that is applicable for hybrid electric vehicle (HEV)/plug-in HEV energy-storage system (ESS) applications, based on the power of the traction motor and the gradient of the battery current. Features of voltage step-down, voltage step-up, and bidirectional power flow are integrated into a single circuit. The novel control strategy enables simpler dynamics, compared with a standard buck converter, with input filter, good regulation capability, low electromagnetic interference, lower source current ripple, ease of control, and continuous input current waveform in both modes of operation (buck and boost modes). [ABSTRACT FROM PUBLISHER]

This paper presents a hardware-in-the-loop experimental rig for testing a proton exchange membrane fuel cell (PEMFC) driving an electrical vehicle. The PEMFC includes an air-management system with a scroll compressor driven by a high- performance sensorless induction motor drive. The sensorless technique is based on a neural-network-based speed observer, i.e., the total least-squares EXIN full-order observer. The whole system is driven by a classic European Driving Cycle (EEC Directive 90/C81/01). An experimental rig has been built to test the system. The torque-speed characteristics of a real scroll compressor have first been measured. Then, these characteristics have been emulated by a brushless interior-mounted permanent-magnet machine controlled in torque. This emulated scroll compressor has been driven by a sensorless field-oriented controlled induction motor drive. The experimental results show that the system attains a global efficiency of about 50% and that the speed estimation accuracy is high at both very low and very high speeds with a stable behavior at zero speed at no load, which is particularly difficult to achieve for model-based sensorless techniques. [ABSTRACT FROM AUTHOR]

This paper introduces a new set of methods to directly integrate ultracapacitor banks into cascaded multilevel inverters that are used for large vehicle propulsion. The idea is to replace the regular dc-link capacitors with ultracapacitors in order to combine the energy storage unit and motor drive. This approach eliminates the need for an interfacing dc-dc converter and considerably improves the efficiency of regenerative braking energy restoration in large vehicles using multilevel converters. Utilizing the proposed modulation control set, the two cascaded inverters can have their dc voltage levels maintained at any ratio (even a noninteger ratio) or dynamically varied over a wide range without disrupting the normal operation of the electric motor. As an advantage, ultracapacitor voltage or state of charge can be freely controlled for braking and/or acceleration power management. A regenerative energy management scheme is also proposed based on the vehicle's speed range considerations. Detailed simulation and experimental results verified the proposed methods. [ABSTRACT FROM AUTHOR]

An energy source is the heart of a hybrid electric vehicle. If it is capable of supplying enough power at all times, then it is an adequate source. Major problems presently facing the industry include the size, cost, and efficiency of the energy source. The primary energy source presently used in automotive systems is a battery. In order to reduce the cost of the battery, the current needs to be decreased and stabilized so it is not very erratic. The purpose of this paper is to introduce and justify the use of a new model for an energy source: a battery in parallel with an ultra-capacitor. The ultra-capacitor can supply a large burst of current, but cannot store much energy. Conversely, the battery can store mass amounts of energy; however, without expensive and inefficient units, a battery cannot provide the current that the ultra-capacitor can. By combining the two energy sources in parallel, the storage and peak current characteristics desired can be achieved. The standards of the vehicle are not degraded, allowing this to be a promising technique to incorporate into hybrid electric vehicles to reduce their cost and increase the efficiency of their energy-source system. [ABSTRACT FROM AUTHOR]