The maximum power tracking (MPPT) is necessary for

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The advent of rapid advances in Electric Vehicle (EV) technology has prompted an increase in
interest in EV battery charging at different locations including homes, shopping malls, rest
areas, and work place, etc. Although there are numerous publications on EV charging from
utility grid, there is less focus on the use of PV for EV charging despite the advantage of its
advantage as a dc source. This thesis concentrates on the design and control of grid-connected
PV charging station in a smart grid environment next to a working place or a university.
Emphasis will be on the control strategies to improve utilization efficiency, reduce harmonics
and speed-up charging. One of the reasons for this is the lack of high PV irradiance in most of
the developed countries where EV use is wide spreading. However, in some developing
countries with high level of PV irradiance such as The Kingdom of Saudi Arabia, EV charging
using PV is promising especially at the work place where long day-time hours are available for
charging hence eliminating the need for fast charging techniques. However, maximum power
tracking (MPPT) is necessary for maximum utilization efficiency of the PV panels.
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1. Introduction
The increasing demand and the quest for inexhaustible clean sources of energy as made
renewable energy to get more attention in recent time. Renewable energy systems has a lot of
advantages. It helps to eliminate harmful emissions from polluting the environment it also
offers inexhaustible resources of primary energy. When compared to the traditional exhaustive
fossil fuels which have various restrictions such as geographical abundance, import regulations
and price fluctuations, the renewable energy sources are not subject to above factors 1. Thus,
more attention is placed on energy utilization especially solar and wind which are more
accessible and abundant than others. Radiant light and heat from the Sun that is harnessed
through solar heating, photovoltaics, solar thermal energy, solar architecture, molten salt
power plants and artificial photosynthesis is called solar energy 2. Solar cells, also called
photovoltaic (PV) cells, convert sunlight directly into electricity through semiconductor
devices. PV gets its name from the process of converting light to electricity, which is called
the PV effect. Photoelectric properties of some semiconducting devices causes them to absorb
photons of light and release electrons. When these free electrons are captured, an electric
current are generated that can be used as electricity 3.
The application of solar energy is rising because of its abundance and accessibility as a means
of electric power generation. One of the areas of its application is the use of solar energy for
electric vehicle charging. Photovoltaic Electric Vehicle Charging (PVEVC) offers a lot of
technical and economical benefits. The effect of greenhouse gases emitted by the conventional
internal combustion engines is seen as a major factor that will accelerate and sustain the growth
of the electric vehicle (EV) usages and more so, PV system is almost maintenance free, both
in terms of fuel and labor. During daytime, the EV is parked idly in the parking area under the
exposure of the full sun 4. If the car-park is roofed by PV, the availability of PV power allows
for an opportunity for “charging while parking” 5. This is an economical and convenient
solution to charge EV at workplaces and parking areas 6.
Fig 1. An example of PV based parking lots for EV charging 7.
Structural-wise, the roofed parking provides free shelters from sun and rain, which is a
favorable feature in hot climate countries 8. In residential charging station, the EV users plug
in when they return home, and their car get recharged overnight. Charging station at home
usually has no user, no metering, authentication, this can be convenient and cot effective. Some
portable chargers can be wall mounted as a charging station.
However, the efficiency of a solar cell is greatly affected by irradiance and temperature. Since
irradiance and temperature level changes momentarily, fluctuation in output becomes
paramount. Efficiency is one of the most essential factors which determine the feasibility and
quality of a power generation unit. In a PV system, the ultimate purpose is to achieve maximum
power output from a solar cell. Maximum Power Point Tracking (MPPT) is used to obtain the
maximum power from these systems. Several of the various means of MPPT techniques are,
Constant Voltage, Open Circuit Voltage, Short Circuit Current, Perturb and Observe,
Incremental Conductance. The figure below shows the I-V characteristics comparison of the IV
and power characteristics at different values of irradiance.

Fig. 2. I-V characteristics at difference value of irradiance 10.
The growth of the Electric Vehicle market has led to novel and innovative ideas to charge them.
Chargers are one of the most integral part of EV plug-to-wheels (PTW) drive train efficiency.
Electric cars are more useful nowadays because of the reassurance drivers get knowing they
can quickly recharge which will aid faster effective trip speed. Fast-charge capable cars with
enough fast charging stations around them make car owners feel capable of taking longer trips.
Ideally, the PTW efficiency for EVs should be close to 45-50%. In order to improve the PTW
energy-efficiency, a high efficiency, high reliability, high power density, and cost-effective
charger design is mandatory 11. An example of PV–grid EV charging system (excluding the
PV array and utility grid) has three main components, namely (1) an MPPT dc–dc converter
(i.e. dc to dc power converter with a built–in MPPT), (2) a bi–directional dc charger and (3) a
bi–directional inverter. A typical set–up for this configuration is shown in Figure 3 12. The
dc common bus provides a convenient point for the integration of all associated components
13. Its voltage varies for different systems, but 200–400 V range is typical. The MPPT dc–
dc converter, which is usually based on the buck–boost or boost topology, is used to harvest
the maximum power from the PV array. The PV voltage is further conditioned so that it can be
transferred efficiently to the dc bus. The dc charger is used to control the voltage and current
so that it suits the EV that is being charged. It also has bi–directional power flow capability.
Figure 3. The PV–grid charging system for EV 13, 14
The bi–directional inverter has dual functions: if the power on the dc bus is to be fed back to
the grid, it behaves as a dc–ac converter (i.e. in inversion mode). On the other hand, if power
needs to be drawn from grid to charge the dc bus, it has to be configured as an ac–dc converter
(rectification mode) 15.
The motive of this thesis is to maximize the use of PV energy with EV charging with minimal
intake from the grid. The advantages of such an EV–PV charger will be reduced energy demand
on the grid due to EV charging as the charging power is locally generated. More so, the overall
performance will be enhanced by incorporating fast DC charging mechanism for the EV and
harmonic reduction when there is demand from the grid.
2. Literature Review
Interest in developing vehicles running on alternate and renewable sources of energy has led
to much research in the direction of improving the technologies involved in the electric and
plug-in vehicles. Along with the improvement of these EV technologies, several initiatives
have been undertaken by various government organizations across the globe to push for the
usage of vehicles which run on alternate sources of energy such as PV11.
The most crucial feature of the MPPT is its ability to track the MPP as quickly and efficiently
as possible. Various conventional MPPT techniques are used, for example perturb and
observe 12, incremental conductance 13 and hill climbing 14. These can be configured
using fixed or adaptive time step. The latter is preferable as it reduces steady state oscillation,
resulting in improved tracking efficiency. Recently, more advanced soft computing methods
such as artificial neural network, particle swarm optimization, fuzzy logic control and
evolutionary algorithm have been proposed for MPPT 15. These methods are more flexible
in handling abnormal conditions such as partial shading and module mismatch 16.
Refs. 16,17 provide excellent summary and performance comparisons among the available
MPPT techniques employed for PV systems.
EV charging imposes an additional loading to the electricity grid 18-19. Due to the fact that
the current drawn from the grid for fast charging EV, can be very large. Furthermore, if the
charging takes place during peak hours, the owner may have to pay a high premium for the
tariff. Because the grid is the principal dynamic entity in any electrical power system and hence
its burden should be controlled by proper way 20, 21. To offset this burden, a PV–grid
charging system is proposed 22. In the perspective of grid operator’s, the availability of PV
power translates to reduced spinning reserve requirements and greater grid stability 23. With
the new features adopted by various researchers in charging schemes, the system becomes more
flexible and is able to increase the battery lifetime 24. This is achieved by introducing the
battery management system, which is necessary to avoid the battery from overcharging and
hence increasing battery life. In 25, 26, the authors proposed a charging system where a dc–
dc charger transfers the charging of EV from PV to grid during the last 20–30% of the charging
phase to prevent the battery from experiencing sudden PV output variations. Another work in
7, proposed an extendable system having multiple charging ports with different levels
(variable) of voltage output. Therefore, it can accommodate different types of EVs. The power
control is done using the dc–dc converter and the algorithm unlike 26, which uses solid state
relays for the same purpose. On other place in 27, the authors used bi–directional dc–dc
charger capable of operating in three modes. (1) mode 1: to charge EV battery only, (2) mode
2: to charge battery and support grid to control any variation in inverter’s output and (3) mode
3: when battery is fully charged, the charger provides a support to grid to stable inverter output.
Authors used single bi–directional inverter unlike using two converters as in 7. The authors
in 28, 29 proposed an intelligent fuzzy logic based smart charging system for parking lots
that manages energy in real time using forecasting models for PV output power and EV power
requirement. For accurate prediction, hourly data, which have been collected over 15 years, are
used. The system sets charging priorities and the rate of charging. The charging priorities
depend upon some charging requirements of the EV like SOC and time of stay etc. While the
charging rates depend upon predicted PV output power, EV power demand and likewise the
grid energy price.
3. Research Objectives
The objectives of this thesis work are as follow:
a. Design of efficient grid-connected PV station for charging electric vehicles at the
work place.
b. The use of utility grid for support but with minimal dependence on power from the
c. Maximum power point tracking (MPPT), fast maximum utilization efficiency of
the PV panels.
d. Reduce harmonics resulting from power electronic devices.
4. Research Methodology
This research work will use theoretical methods as well as simulation programs such as
MatlabSimulink and

Categories: Management


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