Single Phase On-board Charger for Plug-in Electric Vehicle (PEV) Charging applications

Electric Vehicles and Plug-in Electric Vehicles are growing very fast in today?s environment and will remain in upcoming years. These are the best alternative to conventional Internal Combustion Engine (ICE) vehicles [1]. The electric vehicles are powered by an electric motor rather than

Project Title

Single Phase On-board Charger for Plug-in Electric Vehicle (PEV) Charging applications

Project Area of Specialization

Electrical/Electronic Engineering

Project Summary

Electric Vehicles and Plug-in Electric Vehicles are growing very fast in today’s environment
and will remain in upcoming years. These are the best alternative to conventional Internal
Combustion Engine (ICE) vehicles [1]. The electric vehicles are powered by an electric
motor rather than petrol/diesel engine. So electric vehicles do not have a tailpipe and hence
do not cause pollution. Large numbers of electric vehicles produce the congestion problem in
distribution grid during peak load hours. So, to overcome this problem, coordinated charging
will be must to decrease the bad impact on the grid.

The Battery charger proposes of two converters that share a DC link. The DC link is used to
connect these two converters. DC link plays a vital role in charging of the battery from the
grid to vehicle. AC to DC transformation of power is carried out with the help of charger.
The electric vehicle charger is power linkage device that links the grid to the vehicle. The
only purpose of the charger is to follow Power commands that are provided by grid or utility.
These commands are of various types which will be explained further. The single phase Onboard charger can also fulfill power quality functions such as support of reactive power,
regulation of voltage, filtering of harmonics and power factor improvement. The profit of
plug-inan electric vehicle is the capability to keep up the steady and secure operation of the
grid by making cooperation between utility and vehicle.V2G (Vehicle to Grid) operation can
also take place by using PEV charger. There is a necessity of providing reactive power back
to the grid during peak load times. During peak load times the voltage profile of grid
decreases which results in an increase in voltage regulation and hence increase in line current.
The increased line current helps to create a huge amount of copper losses. So, to maintain and
reduce copper losses reactive power supply to the grid is a must.

Project Objectives

To develop the charger which is transformerless and hence alleviates the size, cost and losses of the charger

.To develop the dc-dc buck converter that controls the battery charging current.

To develop the ac-dc full bridge boost converter, which reduces the size of DC-link capacitor.

To develop the proposed charger as shown by Simulink model and the verification of Simulink results has been done with mathematical analysis

Project Implementation Method

The biggest advantage of using these two converters is that it makes the charging operation transformerless. Usage of transformer makes the system bulky and lot of wear and tear takes place by using transformer. The usage of transformer increases the size and weight of transformer. This dissertation consists of transformerless charger. The transformerless charger has ac-dc and dc-dc converters. The function of ac-dc converter is to boost up supply voltage, which is available at 120V or 230V, up to 400V dc link voltage [28]. The nominal battery taken is 365V. Hence the dc link voltage is kept up to 400V. In ac-dc boost converter, the inductor is connected in series with the supply to boost the supply ac voltage, which converts 120V ac supply voltage to 400V dc voltage at converter output across dc-link capacitor (Vdc). MOSFET (Metal Oxide Semiconductor Field Effect Transistor) switches are utilized in ac-dc boost converter. MOSFET switches are used in low power and high frequency applications. The advantage of using MOSFET switches is that they are cheap. In the DC-DC buck converter, fixed voltage across the dc-link capacitor is transformed into

variable voltage at the output of the converter, so that, the battery charging current can be regulated. The prime motive of this dissertation is to charge the battery in fully controllable way.

Benefits of the Project

The biggest advantage of using these two converters is that it makes the charging operation transformerless. Usage of transformer makes the system bulky and lot of wear and tear takes place by using transformer. The usage of transformer increases the size and weight of transformer. This dissertation consists of transformerless charger. The transformerless charger has ac-dc and dc-dc converters. The function of ac-dc converter is to boost up supply voltage, which is available at 120V or 230V, up to 400V dc link voltage [28]. The nominal battery taken is 365V. Hence the dc link voltage is kept up to 400V. In ac-dc boost converter, the inductor is connected in series with the supply to boost the supply ac voltage, which converts 120V ac supply voltage to 400V dc voltage at converter output across dc-link capacitor (Vdc). MOSFET (Metal Oxide Semiconductor Field Effect Transistor) switches are utilized in ac-dc boost converter. MOSFET switches are used in low power and high frequency applications. The advantage of using MOSFET switches is that they are cheap. In the DC-DC buck converter, fixed voltage across the dc-link capacitor is transformed into

variable voltage at the output of the converter, so that, the battery charging current can be regulated. The prime motive of this dissertation is to charge the battery in fully controllable way.

Technical Details of Final Deliverable

The topology used in this dissertation is used to probe battery grid intercourse. Electric Vehicles consists of onboard charger that comprises of two stages: i) ac-dc converter ii) dc-dc converter. The ac-dc converter is a boost rectifier that boosts up low ac supply voltage to high dc link voltage. The regulator for AC-DC boost converter only regulates dc interface voltage and tracks reactive power command (Qcmd). The dc-dc converter is a buck converter that lowers the dc link voltage to battery voltage. The dc-dc converter regulates battery 

charging current. The main motive of charger is to charge the battery along with reactive power compensation to grid. Fig 2.4 represents circuit diagram of the battery charger. The ac- dc converter is experienced with bipolar modulation which means converter output is either

+Vdc or –Vdc. During the turn-on interval of switches S1 and S4, switches S2 and S3 remains switched off and vice-versa. MOSFET switches carry peak current equal to ?2???????? where Ic is RMS charging current. DC link voltage (Vdc) takes part in both ac-dc and dc-dc controllers

and hence Vdc can be taken as a reference to control the battery charging current (ibt). To obtain dc-dc buck operation switches S5 and D6 are switched on as shown in Fig. 2.4. When switchS5is switched on, the battery charging current (ibt) will pass through S5 and Lf, and further charges the Cf and battery. During turn off period of switch S5, diode D6 freewheels the inductor current that passes via inductor Lf and PEV battery while Cf is discharged into battery. In this dissertation the charger operates in charging only mode. However, the inductor at grid side (Lac) is also used to boost up low ac grid voltage to high dc link voltage (Vdc) across dc link capacitor.

Final Deliverable of the Project

HW/SW integrated system

Core Industry

Others

Other Industries

Core Technology

Others

Other Technologies

Sustainable Development Goals

Affordable and Clean Energy

Required Resources

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