CCECE 2014 1569888237
Integrated Battery Charger for Delta Connected Machines in Plug-in Hybrid Electric Vehicles Syed Q. Ali, Student Member, IEEE, Diego Mascarella, Member, IEEE, and Geza Joos, Fellow, IEEE Electrical and Computer Engineering Department McGill University Montreal, Canada
[email protected]
converter (VSC) as a boost converter with an additional rectifier and an input inductance; the other used two windings of the motor as input inductances connected to two legs of the VSC and had a rectifier at the input. The two legs were operated as parallel current-sharing boost converters. Configurations using neutral point of one star (Y) connected machines were presented for single phase and multi-phase chargers using breakers to re-arrange the circuit [3-6], two Y connected machines [7, 8] and for four Y connected machines [9]. An integrated charger for a DC motor drive with a bidirectional Cuk converter was presented in [10] for application in industrial forklifts. It also presented a way to use a 3 phase wound rotor machine as a transformer by locking its rotor. [11] presented an integrated charging solution for a switched reluctance motor (SRM). Integrated chargers for retrofit kits for HEVs were presented in [12, 13]. These utilized the same bulky inductor for traction mode, regenerative mode and charging mode and were required in addition to the motor drive inverter to maintain the DC link voltage. [14, 15] presented integrated chargers for machines having open ended windings with split phases and without split phases respectively. A fully reconfigurable topology was demonstrated in [16] for low power levels. An eight switch inverter was presented in [17] that integrates the single phase charging function with the traction drive but still requires a bulky input inductance. [18-20] present a way of using Y or delta (ll) connected AC machine as a rotating transformer in the charging mode and already connected traction inverter serves as a power factor correction active rectifier. Most of the proposed configurations require an additional single phase rectifier [4-6, 10, 12, 13, 15] with additional input inductance [2, 12, 13, 17] and/or breakers to reconfigure the topology to make it suitable for charging mode [2-4, 9-11, 16, 18-20]. Circuit breakers maybe tolerable for low power applications, but for HEVs the cost and weight of the high rated breakers overshadow the benefits gained. This paper presents a viable integrated charger solution for a dual II connected 3 phase motor that can be extended for multi-phase motors. The paper is organized as follows. Section II shows a suitable battery model for simulation of batteries for electric and hybrid electric vehicles. Section III defmes and discusses the design requirements for an IBC according the relevant standards. Section IV presents the
Abstract-The paper presents an integrated battery charger
topology for a dual three phase delta connected surface mounted permanent magnet synchronous machine used in plug-in hybrid electric vehicles. Design requirements for the battery charger are also summarized from the relevant standards. A suitable battery model is also developed and used to validate the simulation of the charger. Simulation results are presented which confirm the functionality of the charger. Keywords-Battery Modeling, Integrated Charger Design, Plug in Hybrid Electric Vehicles, Unity Power Factor Correction.
I. INTRODUCTION YBRID
electric
vehicles
(HEVs)
have
gained
Hunprecedented importance in the past decade due to its
higher fuel efficiency and decreased dependence on fossil fuel. However they face a challenge of high cost and weight for the battery required and its associated hardware. One way to reduce the hardware associated with the battery is by eliminating its charger. Off board fast chargers have been introduced for fuel pump type charging, but they lack mobility. Therefore on-board chargers are required to allow users to plugin to charge at any available outlet. Electric Vehicle Battery
I I I I I I ------------------- , -I - � ---I I I - -_-_-_-_1 I I 1_-_-_-_-_-_-_-_-_-__ L ________________ l Fig. I Integrated Battery Charger
Researchers have proposed reusing the motor drive components as on-board integrated battery chargers (IBC). The concept of IBCs was fust introduced in [1] and is shown in Fig. 1. It used a thyristor based motor drive with a few circuit breakers to make a battery charger for the charging mode of the converter. Two configurations were proposed in [2], one of which used a leg of the motor drive voltage source
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proposed topology and explains its operation. Section V contains the simulation results for the model and Section VI concludes the paper. II.
RTS and CTS: Short time transients are modeled by an RC network with a small time constant. This models the battery's fast transient behavior. RTL and CTL: Long transient behavior is modeled by an RC network with a large time constant. This models the battery's larger transient behavior. All the parameters depend on the SoC (V sod , number of cycles, temperature and the battery current. Lithium Ion (Li Ion) battery are especially affected by extreme negative temperatures, but now batteries that are capable of working at temperatures as low as 30°C with not more than 15% capacity loss are also available [26].
BATTERY MODELING
Li-Ion battery was selected to be modeled to validate the operation of the integrated charger via simulation. Electrochemical, mathematical and electrical models for the battery have been reported in literature. Detailed electrochemical and mathematical models have little value for circuit simulation software, since they either do not directly relate the IV characteristics to parameters or are so computationally intense that they lose viability [21]. Electrical models, however, could be broadly classified into the following [22]. i) impedance based models [23J These models cater for the internal impedance and the dynamic response of the battery but fail to cater the dependence of open circuit voltage and the loss elements on the state of charge (SoC) of the battery. 2) Thevenin models [24J These models again do not cater for the SoC dependence of the elements and fail to capture the long term capacity fading and self-discharge of the battery. 3) Run time model [25J These models use complex circuit modeling to model all aspects of the battery. These models are resource expensive and are impractical in system level simulations. The model selected is a combination of Thevenin and runtime based models [22]. The circuit model used for battery simulation is shown in Fig. 2.
A. Battery selection and parameter modeling
The model as shown in Fig. 2 was implemented in SimPower Systems ignoring the effect of temperature and cycles on all the parameters by modeling them as a single variable function of Soc. However, we can easily incorporate the effects of temperature and cycles on the parameters, once we develop the battery model. The selected battery is a 850mAh Polymer Li-Ion battery TCL PL-383562 [27]. It was selected because of the availability of its parameters. Thus the model was developed and validated against the results presented in [22] and are shown in Fig. 3.
I
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Fig. 3 Pulse discharge of the developed model Fig. 2 Selected Battery Model
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