1 a fully functional bidirectional charger for the application

1       Contents. 1
2       Abstract 3
3       Introduction. 4
4       Objectives. 4
4.1       Bidirectional Power Flow.. 5
4.2       Power Quality Performance. 5
4.3       Simulation. 5
4.4       Hardware Implementation. 5
4.5       Evaluate performance. 5
5       Literary Review.. 5
5.1       Current status of both PEV
and smart grid technologies and markets. 6
5.1.1        Plug in Electric Vehicles. 6
5.1.2        Smart Grids. 6
5.2       Environmental impact of both
PEVs and smart grid technology. 6
5.2.1        Environmental 6
5.3       Ethical impact of this
project, PEVs and smart grids. 6
5.3.1        Safety. 7
5.3.2        Recognition. 7
5.3.3        Privacy. 7
5.3.4        Security. 7
5.4       Technical investigation of
bidirectional charging systems. 8
5.4.1        Grid. 8
5.4.2        AC Filter. 8
5.4.3        AC – DC Converter. 8
5.4.4        DC – DC Converter. 8
5.4.5        Batteries. 8
6       Work Plan. 10
6.1       Mind Map. 10
6.2       Gantt chart 11
6.3       Risk Management 11
7       References. 11
8       Appendix A Risk Assesment 12
9       References. 15



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Through the integration of renewable energy sources the
growing demand for electrical energy.  
The grid is becoming more and more diverse and complex. This has
accentuated the need reliable, secure and sustainable solutions. Solid state
power electronic converters will be utilised to tackle these complexities and
improve the quality of national grids.

Plug-in electric vehicles (PEVs) have the ability to act as
both a load and/or as source of energy with respect to the grid. Connecting
PEVs to the grid allows for them to be used for ancillary services such as
reactive power control and load balancing. By the use of bidirectional power flow
technology, this project aims to evaluate the performance of bidirectional
chargers individually and as an aggregated groups.

Three elements are required for successful vehicle to grid operation:
power connection to the grid, control and communication between vehicles and
the grid operator, and on-board/off-board intelligent metering. A
charging/discharging infrastructure must be deployed. Economic benefits of V2G
technologies depend on vehicle aggregation and charging/recharging frequency
and strategies. The benefits will receive increased attention from grid
operators and vehicle owners in the future.

The purpose of this project is to design and build a fully
functional bidirectional charger for the application of PEVs. The bidirectional
charger should support bidirectional power flow while not having a negative
impact on power quality.


Plug in
electric vehicles (PEVs) are becoming more and more prevalent on the market. A
PEV can act as both load or as an energy source. Smart grid concepts being
explored are vehicle-to-grid (V2G) and grid-to-vehicle (G2V). PEVs could be
used for energy storage for the electrical power system, V2G, and as controlled
loads, G2V. 1

directives such as the 2009 EU renewable energy directive has driven the growth
of renewables on national power systems. The growing trend towards renewable
energy has increased the importance of energy storage. The intermittency of
renewable energy systems can lead to the curtailment of generators. For
example, when wind is high and the load is low some wind turbines may need to
be switched off. This along with other possible ancillary services such as reactive
power support, frequency control, and load balancing has lead to research and
development of V2G technologies.

One of the
components of V2G and G2V technology is bidirectional power flow. This project
will encompass the design and development of a bidirectional charger. The
bidirectional charger will have the primary ability to control the flow of
power from an AC power supply to a battery or from the battery to the AC power
source. The use of solid state switches shall not have a negative impact on
power quality. Solid state switching, and pulse width modulation, shall provide
the ability of reactive power control and load balancing.     


The overarching
objective of this project is to design, model, build and test a bidirectional
charger for use with PEVs. The bidirectional charger shall have the ability to
control the flow of power from V2G or G2V. The bidirectional charger shall be
designed using power electronics and solid state switching devices, a high
level overview can be seen in Figure 1.

Figure 1 High Level Block Diagram of
Bidirectional Charger

Matlab will
be used to design and build the simulation model. The model will be used to aid
in the design of hardware version of the model. All components will be selected
and controlled using mathematical techniques. The objective of the project can
be further broken down into sub sections.

4.1      Bidirectional Power Flow

power control shall be achieved by controlling the direction of the dc current
flow of the battery. This determines whether the PEV will be operating in a V2G
or G2V mode. The amount of power being delivered or received will be determined
using pulse width modulation (PWM). 

4.2      Power Quality Performance

will be performed due impact of the high frequency switching on the current. An
appropriated filter will be designed using basic electrical elements such as
capacitors, inductors and resistors to reduce the impact of this switching.

4.3      Simulation

As a Matlab
will be used to design and build a model of the bidirectional
charger. The model will be test using a real time simulator.

4.4      Hardware Implementation

A prototype
charger will built be using the calculated values of components. The
appropriate rated of the components are to be used such as voltage, current
power etc.

4.5      Evaluate performance

performance the hardware implementation will be evaluated against the modelled
version. The efficiency of the charger will analysed and the losses will be
accounted for.

Literary Review

Research consisted
of a search and review of available literature. This included a full search of
international journals, conference proceedings, international standards, and
published texts from respected bodies and parties in the area. Internet based
searches of online articles, press releases, government documents, professional
publications, vendor literature, and industry publications.

The areas
deemed necessary for further research can be divided into three main sections:

·       An overview of current status of
both PEV and smart grid technologies and markets

·       Environmental and Ethical impact of
both PEVs and smart grid technology 

·       Technical investigation of
bidirectional charging systems

5.1      Current status of both PEV and smart
grid technologies and markets

5.1.1      Plug in Electric Vehicles

5.1.2      Smart Grids

5.2      Environmental impact of both PEVs
and smart grid technology

5.2.1      Environmental       

Issues related to air pollution are increasingly relevant in
EU countries. The parameters that are usually monitored for measuring air
quality are related to the concentration of specific substances (i.e., PM10,
PM2.5, NO2, C6H6, and CO2), and the sectors that most influence the presence of
these pollutants in the environment are industry, transport, agriculture and
domestic heating. 2

With regards to greenhouse gases and pollutant emissions,
the overall contribution of PEVs is certainly lower than conventional ones.  For example, the CO2 emissions of a Volkswagen
Golf running are respectively 0 g/km for the PEV version, 36 g/km for the PHEV
version, and 122 g/km for the ICE version 3. There are no CO2
emissions as a results of a travelling PEV. There are however CO2 emissions as
a result of the original energy production, this can however be further offset
by producing energy from renewable sources such as solar or wind energy.

5.3      Ethical impact of this project, PEVs
and smart grids

Ethics is a
broad topic covering many areas. This project will be completed to meet with
Engineer’s Ireland Code of Ethics. As such, two main areas require
consideration safety and recognition. Smart Grids use data and digital
electronic systems to control the interaction of various sources of power. The
use of data and control systems system opens the possibility of the violation
of privacy and security of the individual and the collective. As PEVs and
bidirectional chargers are relatively new technologies the consideration must
be given to poorer communities.

5.3.1      Safety

During the
design and implementation of this the safety of public and persons working on
the project shall not be jeopardised. As this project involves the use of
electricity the wiring of the hardware will adhere to the ETCI National Rules
for Electrical Installations. Appropriate signage

5.3.2      Recognition 

materials researched and used in this project will be referenced to give
recognition of the work completed by others. The help and efforts of colleagues
will also be recognised and acknowledged.

5.3.3      Privacy

monitoring and management of smart grid components requires constant and
detailed data collection. The issue of data being collected is a major ethical
consideration. For smart grids in particular, the data gathered from smart
meters may be able to show individual consumers minute by minute power
consumption habits. 4

5.3.4      Security

For the
individual, the information collected could indicate when people are likely to
be at home. This is an issue of personal security if this information was to
fall into the wrong hands. There is a need for a legal framework to be built,
as the current legal framework is not suitable with these new
technologies. 5 On the other hand this information may be used
to reward customers who use electricity to the benefit of grid operators. For
example if non-essential loads were reduced during peak demand times.

national perspective, the combining information and communication technology
with national power systems introduces the security issues of the internet. If
power systems are exposed to hackers this can lead to power disruptions which
can have implications on national security and safety.       Equity

issues arise when dealing with smart grids, since poor communities may not
afford the high costs associated with the necessary equipment to install a smart
grid technologies. 6
Subsidies to these communities may be required. The question must also be asked
that should consumers be burden with management of the load.

5.4      Technical investigation of
bidirectional charging systems

For this
project a major objective is to design, model and simulate a bidirectional
charger. The design will be implemented as a hardware model. A bidirectional
charger can be broken down into a high level components. Research

5.4.1      Grid

The nominal
single phase voltage in Ireland is 230 V 50 Hz. 7 The bidirectional charger
will be designed to these ratings and comply with the ESB networks ‘Conditions
Governing the Connection and Operation of Micro-generation’, document number
DTIS-230206-BRL. This document sets out the limits such as power factor,
harmonics, power ratings and disconnection conditions to prevent islanding of
the grid. A transformer may be required to reduce the magnitude of the voltage
to coordinate with the batteries.

5.4.2      AC Filter

The primary
function of the AC filter is to improve power quality such as introducing
harmonics and bad power factor. The AC filter will be built using a combination
of passive devices.

5.4.3      AC – DC Converter

The AC – DC
converters purpose is to convert AC current to DC current in G2V mode and DC to
AC in V2G mode. It is envisaged that this will be designed using IGBTs in a H
bridge arrangement. PWM will be used to control the switching frequencies of
the IGBTs.

5.4.4      DC – DC Converter

The DC to
DC converter controls the direction of current flow to or from the battery. After
reviewing the current topologies of DC to DC converters, 8 9,
it was decided to use a buck boost arrangement. This was chosen due to the simplicity
of using only two IGBTs to direct the flow of current.

5.4.5      Batteries

Batteries in
PEVs are typically lithium-ion and are usually arranged in series. 10




Initially ideas
based upon research will be used to design a crude simulink model in Matlab.
Using this model a deeper understanding will be used to develop of each
component. The design of the system lends itself well to modular type design.
Each component can be part can be designed individually initially and then
integrated together at a later stage.

6.1      Mind Map

A mind map,Figure
2,  was used to identify and visualise the stages
of the project. The project can be divided into three key sections:

?   Preparation:
Research and Work Plan

?   Implementation:
Design, construction, testing and analysis

?   Evaluation:
Analysis of test results, reporting


Figure 2 Overall Work Plan Mind Map

6.2      Gantt chart


6.3      Risk Management