Integrated Battery Charger Research Articles

Integration of Six-Phase EV Drivetrains Into Battery Charging Process With Direct Grid Connection

The paper proposes two novel topologies for integrated battery charging of electric vehicles. The integration is functional and manifests through re-utilization of existing propulsion drivetrain components, primarily a six-phase inverter and a six-phase machine, to serve as components of a fast (three-phase) charging system. An important feature of the proposed charging systems is that they are with direct grid connection, thus nonisolated from the mains. Torque is not produced in machines during the charging process. The paper provides a comprehensive evaluation of the novel systems, together with an existing topology. Various aspects of the considered chargers are detailed and elaborated, including current balancing, interleaving modulation strategy, and influence of rotor field pulsation on control and overall performance. A control strategy is proposed and the theory and control scheme are verified by experiments.

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In this paper, a zero torque control scheme adopting current sharing function (CSF) used in integrated Switched Reluctance Motor (SRM) drive with DC battery charger is proposed. The proposed control scheme is able to achieve the keeping position (KP), zero torque (ZT) and power factor correction (PFC) at the same time with a simple novel current sharing function algorithm. The proposed CSF makes the proper reference for each phase windings of SRM to satisfy the total charging current of the battery with zero torque output to hold still position with power factor correction, and the copper loss minimization during of battery charging is also achieved during this process. Based on these, CSFs can be used without any recalculation of the optimal current at every sampling time. In this proposed integrated battery charger system, the cost effective, volume and weight reduction and power enlargement is realized by function multiplexing of the motor winding and asymmetric SR converter. By using the phase winding as large inductors for charging process, and taking the asymmetric SR converter as an interleaved converter with boost mode operation, the EV can be charged effectively and successfully with minimum integral system. In this integral system, there is a position sliding mode controller used to overcome any uncertainty such as mutual inductance or DC offset current sensor. Power factor correction and voltage adaption are obtained with three-phase buck type converter (or current source rectifier) that is cascaded with conventional SRM, one for wide input and output voltage range. The practicability is validated by the simulation and experimental results by using a laboratory 3-hp SRM setup based on TI TMS320F28335 platform.

Single-Phase On-Board Integrated Battery Chargers for EVs Based on Multiphase Machines

The paper considers integration of multiphase (more than three phases) machines and converters into a single-phase charging process of electric vehicles (EVs) and, thus, complements recently introduced fast charging solutions for the studied phase numbers. One entirely novel topology, employing a five-phase machine, is introduced and assessed jointly with three other topologies that use an asymmetrical nine-phase machine, an asymmetrical six-phase machine, and a symmetrical six-phase machine. In all topologies, both charging and vehicle-to-grid (V2G) mode are viable. Moreover, all are capable of unity power factor operation. A torque is not produced in machines during charging/V2G process so that mechanical locking is not required. Hardware reconfiguration between propulsion and charging/V2G mode is either not required or minimized by using a single switch. Theoretical analysis of operating principles is given, and a control scheme, applicable to all topologies and which includes current balancing and interleaving strategy, is developed. Finally, operation of all topologies is compared by means of experiments in both charging and V2G mode, with a discussion of influence of current balancing and interleaving strategy on the overall performance.

Overview of fast on‐board integrated battery chargers for electric vehicles based on multiphase machines and power electronics

The study provides an extensive overview of on-board integrated chargers for electric vehicles that are based on multiphase (more than three phases) machines and power electronics. A common attribute of all discussed topologies is that they do not require a charger as a separate device since its role is transferred to the already existing drivetrain elements, predominantly a multiphase machine and an inverter. The study demonstrates how additional degrees of freedom that exist in multiphase systems can be conveniently utilised to achieve torque-free charging operation. Therefore, although three-phase (or multiphase) currents flow through machines' stator windings, they do not generate any torque; thus the machines do not have to be mechanically locked. Cost and weight saving is achieved in this way, while the available space is increased. For each topology operating principles are explained, and its control elaborated in detail for both charging and vehicle-to-grid mode. Finally, the validity of theoretical considerations and control algorithms of some of the existing charging solutions is experimentally verified and experimental performance of all discussed topologies is compared.

On the Feasibility of Integrated Battery Charger Utilizing Traction Motor and Inverter in Plug-In Hybrid Electric Vehicles

For the practical use of an integrated battery charger (IBC), this paper proposes an improved IBC based on a detailed analysis of the conventional IBC with respect to the inherent limitations such as switching frequency, motor inductance, common-mode noise, power loss, and input current and voltage sensing. Moreover, battery charging performance according to pulse-width-modulated switching schemes is mathematically analyzed and explained. The informative simulation and experimental results are provided with the traction motor/inverter hardware of an actual plug-in hybrid vehicle.

Analysis of Electromagnetic Torque and Effective Winding Inductance in a Surface-Mounted PMSM During Integrated Battery Charging Operation

During integrated charging (IC) from a single phase ac utility employing permanent magnet machines, the magnetic field produced by the sinusoidal ac current passing through the stator windings: 1) affects the effective winding inductance used in the charger circuit as a function of different stator winding combinations and 2) produces oscillating torque of varying magnitudes as a function of rotor position. Understanding these challenges, this paper exclusively investigates the electromagnetic effects inside a surface-mounted permanent magnet synchronous machine (SPMSM) when it is used for IC operation in electric vehicles. Variation of oscillating electromagnetic torque magnitude as a function of rotor angle is investigated through finite-element analysis, and recommendations are provided to determine the lowest torque position favorable for IC operation. Thereafter, numerical investigations are conducted for five different stator winding combinations to analyze the issue of varying effective inductance as a result of magnetic coupling in the motor. Furthermore, a mathematical model is developed to obtain these inductances in the five winding configurations. Finally, the numerical investigations are validated by performing experimentations on a 21 hp SPMSM.

Onboard Integrated Battery Charger for EVs Using an Asymmetrical Nine-Phase Machine

This paper considers an integrated onboard charger for electric vehicles that incorporates an asymmetrical nine-phase machine and an inverter into the charging process. The charging is from three-phase mains, and it employs exclusively the power electronic components that already exist on board the vehicle and that are mandatory for the propulsion. No new elements are introduced. Moreover, the charging is achieved without any hardware reconfiguration since the existing elements and their connections are not altered during the transfer from propulsion to the charging mode. Instead, the operating principle is based on additional degrees of freedom that exist in nine-phase machines. These degrees of freedom are employed to avoid electromagnetic torque production in the machine during the charging process, although currents flow through its stator windings. The configuration operates with a unity power factor and is capable of vehicle to grid (V2G) operation as well. A detailed theoretical analysis is given, and the control for the charging/V2G and propulsion modes is discussed. Theoretical analysis is validated by experiments for charging, V2G, and propulsion operating regimes.

Integrated battery charger with power factor correction for electric‐propulsion systems

This paper proposes an on-board integrated battery charger for an electric-propulsion system. The system includes a rectifying diode bridge, an inverter, a permanent magnet motor, a digital signal processor, a battery set and three relays. By suitably controlling the three relays and the power switches of the inverter, the proposed system can be operated as either an electric-propulsion system or a battery charger. The integrated battery charger can be used to charge a 48 V battery set or a 192 V battery set from a single-phase 110 Vrms grid. The battery charger can be operated in a boost-converter charging mode or in buck-converter charging mode with input power factor higher than 0.9 when operating with 48 V battery or 192 V battery, which can meet the IEC 1000-3-2 standard. Only a diode bridge, an inductance-capacitance (LC) filter, and three additional relays are required in addition to the components for propulsion. The windings of the motor and the power switches of the inverter are shared for both the electric-propulsion system and the battery charger. A digital signal processor, TMS-320-F-2808, is used to execute all of the control algorithms. Experimental results validate the theoretical analysis and separately show the correctness and feasibility of the proposed method.

Design and Control of an Optimized Battery Charger for an xEV Based on Photovoltaic Power Systems

The continuous growth of electric vehicles has caused electric power shortages in conventional utilities owing to the charging of electric-vehicle batteries. In order to increase the capacity of these utilities, photovoltaic systems may be an appropriate solution because of their benefits. However, a large amount of loss is generated in a conventional charging structure using photovoltaic sources owing to the many power conversion processes. This paper describes a simple integrated battery charger that utilizes a PV generation system. Moreover, the system control algorithm is deduced by analyzing the operation modes in order to control the proposed integrated system. The proposed system and algorithm are verified by a 3.3-kW prototype, resulting in an increase in the efficiency of approximately 7% to 15% compared with the conventional system. And, to examine the feasibility of the proposed system, the simulation for multi-charger with various conditions are progressed.

Integrated motor drive and non‐isolated battery charger based on the split‐phase PM motors for plug‐in vehicles

A novel integrated motor drive and non-isolated battery charger based on a split-phase permanent magnet (PM) motor is presented and described for a plug-in vehicle. The motor windings are reconfigured by a relay for the traction and charging operation. In traction mode, the motor is like a normal three-phase motor, whereas in the charging mode, after windings reconnection, the system is a three-phase Boost rectifier. One important challenge to use the motor as three inductors in charger circuit is to have it in standstill during the battery charging. Based on the presented mathematical model of a split-phase PM motor, the zero-torque condition of the motor is explained which led to a proper windings reconnection for the charging. Simulation and experimental results of two separate practical systems are provided to verify the proposed integrated battery charger. Some practical limitations and design recommendations are provided to achieve a more realistic practical system.

An Off-line Battery Charger based on Buck-boost Power Factor Correction Converter for Plug-in Electric Vehicles

This paper presents an off-line battery charger based on the buck-boost power factor correction (PFC) converter for plug-in electric vehicles (EV). The integrated battery charger is obtained from the traditional three-phase voltage source inverter (VSI) for EV, which operates as buck-boost converter with power factor correction ability. The PFC controller is regulates the battery voltage and controls the supply current of the converter to achieve unity power factor which is very simple and gives good performance. The proposed buck-boost PFC converter is operating in buck mode and boost mode, which is alternatively carried out according to the relationship between the rectified input voltage and battery voltage. The practicality and performance of the battery charger of the proposed converter topology has been verified via simulation.

Traction Motor-Inverter Utilized Battery Charger for PHEVs

Most eco-friendly cars can adopt the concept of an integrated battery charger (IBC), which uses currently available motor drive systems. The IBC has a lot of strong points such as low cost and minimum space for the high voltage battery charger. On the other hand, it also has some defects caused by its structure. In this paper, the shortcomings of the conventional IBC for PHEVs with interior permanent magnet motors are discussed, and two advanced IBCs with improved performance are presented. Compared with the conventional IBC, the two advanced IBCs have plenty of strengths such as low common noise, high efficiency, simple sensing methods, etc. Then, the digital control algorithm is modified and a power loss calculation is carried out with simulation software. Finally, experimental results are provided to show the performance of the IBC systems.

Grid-Connected Integrated Battery Chargers in Vehicle Applications: Review and New Solution

For vehicles using grid power to charge the battery, traction circuit components are not engaged during the charging time, so there is a possibility to use them in the charger circuit to have an onboard integrated charger. The battery charger can be galvanically isolated or nonisolated from the grid. Different examples of isolated or nonisolated integrated chargers are reviewed and explained. Moreover, a novel isolated-high-power three-phase battery charger based on a split-phase permanent-magnet motor and its winding configuration is presented in this paper. The proposed charger is a bidirectional high-power charger with a unity power factor operation capability that has high efficiency.

An Isolated High-Power Integrated Charger in Electrified-Vehicle Applications

For electric and hybrid vehicles that use grid power to charge the battery, traction circuit components are not normally engaged during the charging time; hence, there is a possibility of using the traction circuit components in the charger circuit to have an onboard integrated charger. An isolated high-power integrated charger based on a special electrical machine with a double set of stator windings is described. Through the reconfiguration of the motor stator windings in the charging mode, a six-terminal machine is achieved. The so-called motor/generator acts as an isolated three-phase power source after synchronization with the utility grid in the charging mode. This rotary isolated power source constitutes a three-phase boost rectifier (battery charger) with full utilization of the inverter. The motor windings are reconfigured by a relay-based switching device for the charging and traction modes. This paper presents the mathematical model of the motor/generator and explains the system's functionality for the traction and charging modes. Furthermore, the charger grid synchronization and charge control are described. Finally, the simulation results are presented for a practically designed system with a traction power of 25 kW and a possible charge power of 12.5 kW.

An Integral Battery Charger With Power Factor Correction for Electric Scooter

This paper presents an integral battery charger for an electric scooter with high voltage batteries and interior-permanent-magnet motor traction drive. The battery charger is derived from the power hardware of the scooter, with the ac motor drive that operates as three-phase boost rectifier with power factor correction capability. The control of the charger is also integrated into the scooter control firmware that is implemented on a fixed-point DSP controller. Current-controlled or voltage-controlled charge modes are actuated according to the requirements of the battery management system, that is embedded into the battery pack. With respect to previous integrated chargers, the ac current is absorbed at unitary power factor with no harmonic distortion. Moreover, no additional filtering is needed since the pulsewidth modulation ripple is minimized by means of phase interleaving. The feasibility of the integral charger with different ac motors (induction motor, surface-mounted phase modulation motor) is also discussed, by means of a general model purposely developed for three-phase ac machines. The effectiveness of the proposed battery charger is experimentally demonstrated on a prototype electric scooter, equipped with two Li-ion battery packs rated 260 V, 20 Ah.

An integral battery charger for four-wheel drive electric vehicle

In this study, an integral battery charger is proposed, which fully uses the hardware of the four-wheel drive electric vehicle. It has no extra component except a mechanical transfer switch. The inverters and the traction motors for the propulsion of the vehicle are transformed to a battery charger. It is verified by a prototype experiment that the charger can be operated at unity power factor and can match any kind of charging mode, such as constant voltage or constant current. >

An SCR Inverter with an Integral Battery Charger for Electric Vehicles

A thyristor-based inverter/charger for use in electric passenger vehicles is described, and prototype charger test results are presented. A battery charger is included integral to the inverter by using a subset of the inverter power circuit components. The integral charger employs the inverter commutation components as a resonant ac/dc converter rated at 3.6 kW. The resulting charger provides electrical isolation between the vehicle propulsion battery and ac line and is capable of charging a 25-kWh propulsion battery in 8 h from a 220-V ac line. Charger efficiency and power factor at an output power of 3.6 kW are 86 and 95 percent, respectively. The inverter, when operated with a matching polyphase ac induction motor and nominal 132-V propulsion battery, can provide a peak shaft power of 34 kW (45 hp) during motoring operation and 45 kW (60 hp) during regeneration. Thyristors are employed for the inverter power switching devices and are arranged in an input-commutated topology. This configuration requires only two thyristors to commutate the six main inverter thyristors. The combined ac inverter/charger package weighs 47 kg (103 lb).