Download This paper suggests a new electrolytic capacitor-less bi

PERFORMANCE ANALYSIS OF BI-DIRECTIONAL DC-DC
CONVERTERS FOR ELECTRIC VEHICLES
ABSTRACT:
This paper suggests a new electrolytic capacitor-less bi-directional on-board
charger for electric vehicle. It has a cascade structure of constant frequency
resonant converter for electrical isolation and DCM buck/boost converter for
charging/discharging control and input harmonic regulation. Harmonic modulation
technique is also proposed to obtain a high power factor and structure change
method has been adopted to cope with a wide line voltage condition. Harmonic
regulation and charging/discharging control can be accomplished with very simple
control algorithm so that high performance controller is not required. Its feasibility
has been verified with a 3-kW prototype
INTRODUCTION:
The DC-DC converter needs to have bi-directional power flow capability so
that regenerative energy can be captured and stored in the energy storage. In
addition, some applications may require overlapping input-output voltage ranges.
The two DC-DC converters analyzed and compared in this research can be
used for DC fast charging in EV/HEVs to extend the all-electric drive range. A
municipal parking deck charging station with DC power distribution bus can
employ bi-directional DC-DC charger to allow Vehicle to Grid (V2G) operation .
V2G operation can be useful to inject real or reactive power to the grid to
ensure current harmonic filtering or load balancing. A bi-directional converter with
overlapping input output voltage range would enhance the operational flexibility
for G2V or V2G applications.
In, a battery charger comprised of interleaved CCM boost converter and FB
converter has been proposed and evaluated. Also, power factor correction (PFC)
converters suitable for EV based on bridgeless PFC converter and bi-directional Hbridge inverter have been studied.
They have good performances of high power factor (PF), wide line
regulation performance, and clean charging current but they have several
disadvantages to be applied for vehicle applications.
However, the intermediate dc link capacitor that should have a large value to
filter power fluctuation has been implemented with a high voltage electrolytic
capacitor that cannot be used in automotive applications due to its short lifetime.
To use a link capacitor mall enough to be implemented using film capacitor
and link capacitor ripple reduction, several techniques have been studied to reduce
the link capacitor ripple by using synchronization of input and output currents in
link capacitor or additional circuit of ripple compensator . In addition, other circuit
structures have been suggested using link voltage of the rectified ac waveform .
EXISTING SYSTEM:
This system requires two switching dc to ac converters operating at a high
frequency so as to convert the dc input to high frequency ac quantities. Galvanic
isolation between the source and load side is provided by the high-frequency
transformer. Transformer also performs voltage matching between the source and
the load side since the voltage ratio between them is very high. The transformer
works with ac quantities and hence a dc-ac converter is required at both the
terminals. Since the system is meant for the energy transfer in both the directions,
dc to ac converters employed must have the capability of bidirectional power flow.
This converters also like the non-isolated bidirectional DC-DC converters works in
two modes of operation i.e. in buck or boost.
PROPOSED SYSTEM:
The conventional Cascaded Buck Boost Inductor in the middle (CBB-IIM)
having an interfacing inductor between the input and output sides. On the other
hand presents the Cascaded Buck Boost Capacitor in the middle (CBB-CIM)
topology where the two half bridge converters are cascaded together with a
common dc bus capacitor. The DC bus voltage is typically higher than the battery
voltage in electric vehicles with a boost stage, but depending on the characteristics
of the batteries and design of the propulsion system the battery voltage may
overlap with the nominal DC bus voltage. Therefore, the converter must have the
capability to handle the input and output side voltages with overlapping ranges.
Both the converters, CBB-IIM and CBB-CIM, have the input and output voltage
overlap capability
ADVANTAGES:
 Low cost
 Less number of switches
BLOCK DIAGRAM:
TOOLS AND SOFTWARE USED:
 MPLAB – microcontroller programming.
 ORCAD – circuit layout.
 MATLAB/Simulink – Simulation
APPLICATIONS:
 Electric and hybrid electric vehicle (EV/HEV).
CONCLUSION:
A new bi-directional electrolytic capacitor-less EV on-board charger
comprised of a resonant converter and DCM buck/boost converter has been
proposed. To improve the power factor in the DCM operation and secure proper
operation under discharging mode, harmonicmodulation technique has been
proposed based on analysis of optimal operational duty-ratio. Also, structure
change method has been adopted to avoid high gain operation of buck/boost stage.
To verify the performance, a 3-KW prototype charger has been implemented with
the design guideline. Experimental results show that the efficiency of around 93%
under bi-directional power flow has been recorded at the rated condition,
maintaining high power factor near to unity. Therefore, it may be suitable for full
digital-controlled bi-directional EV chargers requiring for long lifetime and small
size.
REFERENCES:
[1] V. Monteiro, J. G. Pinto, B. Exposto, H. Goncalves, J. C. Ferreira, C. Couto,
and J. L. Afonso, “Assessment of a battery charger for electric vehicles with
reactive power control,” presented at the 38th Annu. Conf. IEEE Ind. Electron.
Soc., pp. 5142–5147, Montreal, Canada, 2012.
[2] O. C. Onar, J. Kobayashi, D. C. Erb, and A. Khaligh, “A bidirectional highpower-quality grid interface with a novel bidirectional noninverted buck–boost
converter for PHEVs,” IEEE Trans. Veh. Tech., vol. 61, no. 5, pp. 2018–2032, Jun.
2012.
[3] U. K. Madawala and D. J. Thrimawithana, “A bidirectional inductive power
interface for electric vehicles in V2G systems,” IEEE Trans. Ind. Electron., vol. 58,
no. 10, pp. 4789–4796, Oct. 2011.
[4] O. C. Onar, J. Kobayashi, D. C. Erb, and A. Khaligh, “Bi-directional charging
topologies for plug-in hybrid electric vehicles,” in Proc. Appl. Power Electron.
Conf., 2010, pp. 2066–2072.
[5] R. J. Ferreira, L. M. Miranda, R. E. Araujo, and J. P. Lopes, “A new
bidirectional charger for vehicle-to-grid integration,” in Proc. IEEE PES Int. Conf.
Exhib. Innovative Smart Grid Technol., 2011, pp. 1–5.