Nghiên cứu giải pháp tối ưu hoá quá trình điều khiển và vận hành trạm sạc tích hợp điện mặt trời tại Việt Nam

BỘ CÔNG THƯƠNG
TRƯỜNG ĐẠI HỌC ĐIỆN LỰC

NGUYỄN NGỌC VĂN

NGHIÊN CỨU GIẢI PHÁP TỐI ƯU HĨA Q TRÌNH ĐIỀU KHIỂN
VÀ VẬN HÀNH TRẠM SẠC TÍCH HỢP ĐIỆN MẶT TRỜI
TẠI VIỆT NAM

LUẤN ÁN TIẾN SĨ: KỸ THUẬT NĂNG LƯỢNG

Hà Nội – 2023


BỘ CÔNG THƯƠNG
TRƯỜNG ĐẠI HỌC ĐIỆN LỰC

NGUYỄN NGỌC VĂN

NGHIÊN CỨU GIẢI PHÁP TỐI ƯU HĨA Q TRÌNH ĐIỀU KHIỂN
VÀ VẬN HÀNH TRẠM SẠC TÍCH HỢP ĐIỆN MẶT TRỜI
TẠI VIỆT NAM

Ngành: Kỹ thuật Năng lượng
Mã số: Thí điểm

LUẬN ÁN TIẾN SĨ: KỸ THUẬT NĂNG LƯỢNG

NGƯỜI HƯỚNG DẪN KHOA HỌC
PGS. TS. NGUYỄN HỮU ĐỨC

Hà Nội - 2023


THE MINISTRY OF INDUSTRY AND TRADE
ELECTRIC POWER UNIVERSITY

VAN NGUYEN NGOC

A RESEARCH ON OPTIMAL SOLUTIONS FOR CONTROL AND
OPERATION OF PHOTOVOLTAIC INTEGRATED CHARGING STATIONS
IN VIETNAM

Field: Energy engineering
Code: Pilot

DISSERTATION: ENERGY ENGINEERING

SUPERVISOR
ASSOC. PROF. DR. DUC NGUYEN HUU

Hanoi - 2023


i
DECLARATION
I hereby declare that this is my original research work. The cited information in
the dissertation has been properly referred and the sources are clearly indicated. The
data and research results presented in this thesis are truthful and have not been
published in any other scientific work.
Hanoi, August 10th, 2023

Supervisor

Ph.D. Candidate

ASSOC. PROF. DR. Duc Nguyen Huu

Van Nguyen Ngoc


ii
AKNOWLEDGEMENTS
I would like to express my sincere gratitude to the supervisor, Assoc. Prof. Dr.
Duc Nguyen Huu, for his supervision, support, and encouragement throughout the
course of my research. He has motivated and inspired my research and was constantly
supportive of my endeavors. His profound expertise and insightful advice had been
invaluable in my research. Under his supervision, I not only built my research skills
but learnt a lot of interpersonal skills as well.
I am deeply appreciative of the Electric Power University's leadership, the
Postgraduate Training Department, the Faculty of Energy Technology, and the
Electrical Engineering Faculty, as well as professors, colleagues etc. who had
provided me assistance and motivation during the research.
I had the opportunity of collaborating with numerous fellow students and
engineers throughout my Ph.D. journey. I am sincerely grateful for their valuable
contribution.
Lastly, I would like to thank my wife and my beloved family. Their unconditional
love had been invaluable in maintaining my dedication and enthusiasm during the
research.
Hanoi, August 10th, 2023
Ph.D. Candidate

Van Nguyen Ngoc


iii
TABLE OF CONTENTS
DECLARATION ........................................................................................................ i
AKNOWLEDGEMENTS.........................................................................................ii
TABLE OF CONTENTS ........................................................................................ iii
ABBREVIATIONS .................................................................................................. vi
LIST OF TABLES ..................................................................................................vii
LIST OF FIGURES .............................................................................................. viii
INTRODUCTION ..................................................................................................... 1
1. Motivation for research .......................................................................................1
1.1 COP26 and PDP VIII – the commitments of Vietnam to sustainable
development ................................................................................................................1
1.2 The transition to electric two-wheeler mobility in Vietnam’s urbans ..............2
1.3 Rooftop solar power development in Vietnam and its impacts ........................4
1.4 PV-integrated charging stations – A solution for both E2W and rooftop solar
development ................................................................................................................5
2. Research goals, scope, and research questions ...................................................7
3. Research methodology ......................................................................................10
4. Research contributions and outline of the thesis ..............................................10
CHAPTER I: OVERVIEW OF ELECTRIC VEHICLE CHARGING
STATIONS – ARCHITECTURES AND CONTROL ALGORITHMS............ 12
1.1 Charging station architectures.........................................................................12
1.1.1 Centralized control architecture ...................................................................13
1.1.2 Decentralized control architecture ...............................................................13
1.1.3 Hierarchical control architecture .................................................................14
1.1.4 Proposal of E2W charging station architecture ...........................................15
1.2 EV charging station control algorithms ..........................................................16

1.2.1 Algorithms focus on technical aspects ........................................................17
1.2.2 Algorithms focus on economic objectives ...................................................22
1.3 Summary .........................................................................................................24


iv
CHAPTER

II:

MODELING

OF

PV-INTEGRATED

ELECTRIC-

TWOWHEELER CHARGING STATIONS........................................................ 25
2.1 Chapter objectives ...........................................................................................25
2.2 Charging station block diagram ......................................................................25
2.3 Realtime model ...............................................................................................26
2.3.1 PV module and PV array .............................................................................26
2.3.2 Battery model ...............................................................................................28
2.3.3 DC-DC boost converter and maximum power point tracking (MPPT)
algorithm ...................................................................................................................31
2.3.4 Grid-tie inverter ...........................................................................................33
2.3.5 Bi-directional charger/discharger ................................................................34
2.4 Long-term model ............................................................................................35
2.5 Summary .........................................................................................................36

CHAPTER III: CHARGING POWER ALLOCATION ALGORITHM FOR
E2W CHARGING STATIONS ............................................................................. 37
3.1 Chapter objectives ...........................................................................................37
3.2 Input data requirements...................................................................................37
3.2.1 Electric bike and electric motorcycle specifications ...................................38
3.2.2 Charging behaviors ......................................................................................39
3.2.3 Conventional load profile ............................................................................44
3.2.4 Solar power output profile ...........................................................................44
3.2.5 Battery degradation - A crucial consideration of V2G technology .............44
3.3 Charging power allocation algorithm for E2Ws .............................................45
3.3.1 Mathematical formulation of the algorithm.................................................47
3.3.2 Algorithm flowchart ....................................................................................50
3.3.3 Case study ....................................................................................................54
3.4 Summary .........................................................................................................62
CHAPTER IV: OPTIMAL CHARGING ALGORITHM BASED ON
RECEDING HORIZON FRAMEWORK ............................................................ 64


v
4.1 Chapter objectives ...........................................................................................64
4.2 Mathematical formulation, control framework and algorithm flowchart .......65
4.2.1 Objective function........................................................................................65
4.2.2 Quadratic Programming with MATLAB.....................................................67
4.2.3 Receding horizon framework ......................................................................68
4.2.4 Flowchart algorithm .....................................................................................71
4.3 Case study and simulation results ...................................................................72
4.3.1 Charging station at university ......................................................................74
4.3.2 Office charging station ................................................................................87
4.3.3 Apartment charging station ..........................................................................93
4.3.4 Charging station at factory...........................................................................99

4.4 Summary .......................................................................................................106
CHAPTER V: REALTIME RESPONSES OF E2W CHARGING AND
PRACTICAL VERIFICATION .......................................................................... 108
5.1 Chapter objectives .........................................................................................108
5.2 Real-time charging/discharging simulation ..................................................108
5.3 Testing workbench set up .............................................................................110
5.3.1 The technical scope of the test bench ........................................................110
5.3.2 Test bench design and operation................................................................112
5.3.3 Test bench set up........................................................................................114
5.3.4 Testing results ............................................................................................121
5.4. Summary ......................................................................................................124
CONCLUSIONS ................................................................................................... 127
LIST OF PUBLICATIONS .................................................................................. 129
REFERENCES ...................................................................................................... 130


vi
ABBREVIATIONS
No.

Abbreviation

English

1

BESS

Battery energy storage system

2
3

DOD
DSM

Depth of discharge
Demand side management

4

DSO

Distributed system operator

5
6
7
8
9
10
11
12
13
14
15
16
17
18
19

20

E2W
EV
EVCS
EVG
FIT
G2V
GHG
HEV
ICE
OP
PCC
PDF
PDP
PEV
PHEV
PV

Electric Two-wheeler
Electric vehicle
Electric vehicle charging station
Electric vehicle group
Feed-in-tariff
Grid to vehicle
Greenhouse gas
Hybrid electric vehicle
Internal combustion engine
Optimization problem
Point of common coupling

Probability density function
Power development plan
Plug-in electric vehicle
Plug-in hybrid electric vehicle
Photovoltaic

21

QP

Quadratic programming

22

RES

Renewable energy source

23

SO

System operator

24
25
26
27
28

SOC
TOU
UI
V2G
VIS

State of charge
Time of use
User interface
Vehicle to grid
Vehicle information system

Vietnamese
Hệ thống tích trữ năng
lượng bằng ắc quy
Mức xả sâu
Quản lý nhu cầu điện
Người vận hành hệ
thống phân phối
Xe điện hai bánh
Xe điện
Trạm sạc xe điện
Nhóm xe điện
Biểu giá FIT
Lưới tới xe điện
Khí nhà kính
Xe điện lai
Động cơ đốt trong
Bài tốn tối ưu
Điểm kết nối

Hàm mật độ xác suất
Quy hoạch điện
Xe điện có cắm sạc
Xe điện lai có cắm sạc
Quang điện
Quy hoạch toàn
phương
Nguồn tái tạo
Người vận hành hệ
thống
Trạng thái sạc
Thời điểm sử dụng
Giao diện người dùng
Xe điện tới lưới
Hệ thống thông tin xe


vii
LIST OF TABLES
Table 1.1 Classification of charging station problems ..............................................17
Table 2.1 PV panel specifications .............................................................................27
Table 2.2 Voc = f (SOC, temp) ..................................................................................30
Table 2.3 Rchg = f (SOC, temp) .................................................................................30
Table 2.4 Rdis = f (SOC, temp) ................................................................................30
Table 3.1 The family of L-category vehicles ............................................................38
Table 3.2 E2W specifications ...................................................................................39
Table 3.3 System Information ...................................................................................55
Table 3.4 Load variance in four different scenarios .................................................58
Table 4.1 Load variance in different scenarios..........................................................78
Table 4.2 Arrival/ departure time probability distribution parameters ......................80

Table 4.3 Load variance in different scenario ...........................................................85
Table 4.4 Arrival/ departure time probability distribution parameters ......................87
Table 4.5 Load variance in different scenarios..........................................................92
Table 4.6 Arrival/ departure time probability distribution parameters ......................93
Table 4.7 Load variance in different scenarios..........................................................98
Table 4.8 Arrival/ departure time probability distribution parameters ......................99
Table 4.9 Load variance in different scenarios ........................................................104
Table 5.1 Cell specifications ...................................................................................115
Table 5.2 Battery pack specifications .....................................................................116
Table 5.3 Micro grid tie inverter specifications ......................................................116
Table 5.4 Specifications of boost/buck converters .................................................117
Table 5.5 Specifications of solar inverter and solar panel ......................................118
Table 5.6 Other devices...........................................................................................120


viii
LIST OF FIGURES
Figure 1 Private vehicle ownership in Vietnam and other countries ..........................2
Figure 2 Traffic congestion in Hanoi ..........................................................................2
Figure 3 The fifteen most polluted cities in Southeast Asia in 2018 ..........................3
Figure 4 Map of average daily global horizontal irradiance (GHI) in Vietnam .........4
Figure 5 Top 10 countries by PV installed capacity in 2020 ......................................4
Figure 6 A PV-integrated E2W charging station. .......................................................6
Figure 7 Charging station block diagram. ...................................................................7
Figure 1.1 Charging station architecture. ..................................................................13
Figure 2.1 Charging station block diagram. ..............................................................25
Figure 2.2 The one-diode model and Thevenin equivalent circuit ...........................26
Figure 2.3 PV panel model........................................................................................28
Figure 2.4 The equivalent circuit model of a battery ................................................29
Figure 2.5 Battery model...........................................................................................30

Figure 2.6 DC-DC boost converter block .................................................................31
Figure 2.7 Flowchart of P&O algorithm ...................................................................32
Figure 2.8 P-V curve .................................................................................................32
Figure 2.9 Flowchart of INC algorithm ....................................................................33
Figure 2.10 Transformation to the 𝑑𝑞 coordinate system. ........................................33
Figure 2.11 Determination of 𝑤𝑡. .............................................................................33
Figure 2.12 Control signal block for generating PWM signals. ...............................34
Figure 2.13 PWM signal generation and the inverter power circuit. ........................34
Figure 2.14 Bi-directional charger ............................................................................34
Figure 3.1 Arrival/departure distribution function - trip home .................................41
Figure 3.2 Probability densities of home arrival and departure times ......................42
Figure 3.3 Probability densities of workplace arrival and departure times ..............43
Figure 3.4 Arrival/departure distribution function (shift operation) .........................43
Figure 3.5 Flowchart of stage 1 algorithm ................................................................52
Figure 3.6 Flowchart of stage 2 algorithm ................................................................52


ix
Figure 3.7 Flowchart of stage 3 algorithm ................................................................53
Figure 3.8 Initial SOC distribution. ...........................................................................54
Figure 3.9 Non-EV load profile. ...............................................................................55
Figure 3.10 PV power profile in a typical day of months. ........................................56
Figure 3.11 Total load profile after stage 1 implementation. ....................................57
Figure 3.12 Load variance in four scenarios .............................................................58
Figure 3.13 Smart charging power profile. ...............................................................59
Figure 3.14 Group charging power profile in January. .............................................61
Figure 3.15 Group charging power profile in June. ..................................................61
Figure 3.16 Individual charging pattern for group 9 .................................................61
Figure 3.17 Individual charging pattern for group 1 .................................................61
Figure 3.18 Profiles of a typical E2W in groups in January......................................62

Figure 3.19 Profiles of a typical E2W in groups in June ...........................................62
Figure 4.1 Scheduling and implementing timeline. ..................................................66
Figure 4.2 Illustration of receding horizon time window .........................................69
Figure 4.3 Flowchart of the algorithm.......................................................................72
Figure 4.4 Average charging pattern .........................................................................75
Figure 4.5 Max rate charging pattern ........................................................................75
Figure 4.6 Total load profile in scenarios 1, 2, 3 .......................................................75
Figure 4.7 Charging profile – RHC based algorithm (scenario 4.1) .........................75
Figure 4.8 Total load profile – RHC based algorithm (scenario 4.1) ......................76
Figure 4.9 Charging profile – RHC based algorithm (scenario 4.2) .........................76
Figure 4.10 Total load profile – RHC based algorithm (scenario 4.2) .....................76
Figure 4.11 Load variance in different cases .............................................................78
Figure 4.12 Load variance in the two proposed algorithms ......................................79
Figure 4.13 Average charging pattern .......................................................................81
Figure 4.14 Max rate charging pattern ......................................................................81
Figure 4.15 Total load profile in scenarios 1, 2, 3.....................................................82
Figure 4.16 Charging profile – RH algorithm scenario 4.1 ......................................83


x
Figure 4.17 Total load profile – RH algorithm scenario 4.1 .....................................84
Figure 4.18 Charging profile – RH algorithm scenario 4.2 ......................................84
Figure 4.19 Total load profile – RH algorithm scenario 4.2 .....................................85
Figure 4.20 Load variance in different scenarios ......................................................86
Figure 4.21 Average charging pattern .......................................................................88
Figure 4.22 Max rate charging pattern ......................................................................88
Figure 4.23 Total load profile in scenarios 1, 2, 3 .....................................................89
Figure 4.24 Charging profile – RH algorithm scenario 4.1 ......................................90
Figure 4.25 Total load profile – RH algorithm scenario 4.1 .....................................90
Figure 4.26 Charging profile – RH algorithm scenario 4.2 ......................................91

Figure 4.27 Total load profile – RH algorithm scenario 4.2 .....................................91
Figure 4.28 Load variance in different scenario ........................................................92
Figure 4.29 Average charging pattern .......................................................................94
Figure 4.30 Max rate charging pattern ......................................................................94
Figure 4.31 Total load profile in scenarios 1, 2, 3 .....................................................95
Figure 4.32 Charging profile – RH algorithm scenario 4.1 ......................................96
Figure 4.33 Total load profile – RH algorithm scenario 4.1 .....................................97
Figure 4.34 Charging profile – RH algorithm scenario 4.2 ......................................97
Figure 4.35 Total load profile – RH algorithm scenario 4.2 .....................................97
Figure 4.36 Load variance in different scenario ........................................................98
Figure 4.37 Average charging pattern .....................................................................100
Figure 4.38 Max rate charging pattern ....................................................................101
Figure 4.39 Total load profile in scenarios 1, 2, 3 ...................................................102
Figure 4.40 Charging profile – RH algorithm scenario 4.1 ....................................103
Figure 4.41 Total load profile – RH algorithm scenario 4.1 ...................................103
Figure 4.42 Charging profile – RH algorithm scenario 4.2 ....................................103
Figure 4.43 Total load profile – RH algorithm scenario 4.2 ...................................104
Figure 4.44 Load variance in different scenarios ....................................................105
Figure 5.1 Typical total charging profile. ...............................................................109


xi
Figure 5.2 Total charging current at 5.6 kW charging power command ................109
Figure 5.3 Charging response when power command changes from 5.6 kW (charging)
to -1.95 kW (discharging) .......................................................................................109
Figure 5.4 Total charging power at charging commands of 5.6 kW, -1.95 kW, -6.56
kW ...........................................................................................................................109
Figure 5.5 PV power, grid power, conventional load and charging load ...............109
Figure 5.6 SOC and battery voltage of a typical E2W............................................110
Figure 5.7 Test bench block diagram ......................................................................111

Figure 5.8 Testing workbench design .....................................................................113
Figure 5.9 Battery pack ...........................................................................................115
Figure 5.10 Single phase grid-tie inverter ...............................................................116
Figure 5.11 Boost/Buck converter ..........................................................................117
Figure 5.12 Solar inverter and solar panel ..............................................................118
Figure 5.13 Modbus RTU connection .....................................................................119
Figure 5.14 Test bench set up. ................................................................................121
Figure 5.15 Real-time charging response ...............................................................122
Figure 5.16 Real-time discharging response ...........................................................123
Figure 5.17 Real-time charge to discharge response. .............................................124


1
INTRODUCTION
1. Motivation for research
1.1 COP26 and PDP VIII – the commitments of Vietnam to sustainable
development
At the COP26 conference, Vietnam made strong commitments and responsible
contributions to tackle global climate change. Accordingly, Vietnam has committed
to bring net emissions to zero by the middle of the century and joined the Global Coal
to Clean Power Transition Statement. In line with these commitments, the
government has outlined a comprehensive roadmap with eight key tasks aiming at
achieving sustainable and low-emission economic development [143].
These tasks involve promoting the transition from fossil fuel to green/clean
renewable energy sources (RESs), reducing greenhouse gas (GHG) emissions in
energy, transportation, and other sectors. Notably, the reduction in the use of fossil
fuel vehicles, the encouragement of electric vehicle (EV) research, EV development
and adoption are also promoted. The Ministry of Transport needs to study the
feasibility of phasing out fossil fuel vehicles by 2040 and develop a roadmap for the
transition to clean energy transportation.

Worth mentioning, on May 15th, 2023, the Vietnamese government adopted the
Power Development Plan VIII (PDP VIII), showing a strong commitment towards
decarbonization.
The PDP VIII sets a new RES development direction by increasing the amount of
renewable power generation capacity (i.e., up to 48 percent of the total capacity by
2030, and 65.8-71 percent by 2050) while significantly reducing coal power share in
the electricity distribution plan (i.e., from 20 percent of the total capacity to 0 percent
by 2050). The PDP VIII no longer prioritizes grid-connected solar power projects. It
strongly promotes the development of solar energy for self-consumption (i.e., solar
power on rooftops of residential houses and buildings for on-site consumption,
without injection into the electricity grid). Specifically, it sets a target of 50 percent of


2
office buildings and residential houses using rooftop solar power for selfconsumption by 2030.
The commitments at the COP26 and the PDP VIII demonstrate the Vietnamese
government's determination toward sustainable development across various sectors,
especially energy and transportation. Follow the orientation, this research is proposed
to study solutions to promote the development of both RESs and clean transportation
in the context of Vietnam.
1.2 The transition to electric two-wheeler mobility in Vietnam’s urbans
Currently, in Hanoi, Ho Chi Minh City (HCMC), public transport has not been
able to satisfy the travel demand, constituting about 15 % and 9 % of travel need in
Hanoi and HCMC, respectively. Urban traffic heavily depends on private vehicles, in
which gasoline-powered motorcycles take a dominant role of about 80 % [25]. The
overwhelming majority of private fossil fuel vehicles (Figure 1) leads to traffic
congestion (Figure 2), increased GHG emissions and air pollution [134].

Figure 1 Private vehicle ownership in Vietnam and

Figure 2 Traffic

other countries

congestion in Hanoi

Research shown that in developing countries as in Vietnam, poor traffic
infrastructure [133], [146], inadequate public transport [43], [133], [151], low- and
middle-income level and weather condition are factors which cause most people to
choose private motorcycles as the preferred means of transportation in urban traffic
[53].
The high number of private vehicles puts a burden on urban traffic, causing traffic
congestion, noise, and air pollution (Figure 3). To address these issues, solutions had


3
been proposed such as applying stricter exhaust emission standards, limiting private
vehicles, developing public transport, and encouraging fewer polluting vehicles ...
Among the solutions, transport electrification can
contribute to both air pollution reduction and energy
diversification.

Benefits

include

zero

tail-pipe

emissions, higher efficiency than vehicles using
internal combustion engines (ICE), high potential for
GHG emissions reduction when coupled with a lowcarbon

electricity

sector,

reducing

fossil

fuels

dependence, lesser noise and being able to provide
ancillary services to the energy system [99].
Regarding electric mobility transition in Vietnam, in
the first periods, with low purchase price (about 400
USD [99]), low speed, no driver's license and vehicle
registration requirements, electric bicycles had been
widely used by students and elders. However, these

Figure 3 The fifteen most

vehicles were not attractive because of their low

polluted cities in Southeast

quality, and they couldn’t perform as well as gasoline-

Asia in 2018

powered counterparts [134].
Electric two-wheelers (E2Ws) gradually attracted the public’s attention when
major manufacturers such as Honda, Yamaha, Piaggio, Vinfast etc. engaged in the
market. Modern designs, good quality, diverse features (e-Sim, anti-theft, cruise
control, operation history record, waterproof) and reasonable purchase price were
factors that had propelled E2Ws to the forefront of the public interest.
In 2019, many high-quality E2W products were debuted in Vietnam. A remarkable
growth from 0.9 million E2Ws by 2017 to five million units by 2019 was recorded
by the International Association of Public Transport (UITP). By 2019, there were
eleven enterprises producing E2Ws with the output volume reaching 52,938 units


4
(Registry Department). Annually, the growth rate of the E2W market is up to 30 - 40
%.
The transition from traditional motorcycles to E2Ws might be the result of current
high rate of motorbike adoption, socio-economic conditions, and limited transport
infrastructure [13], [49]. E2Ws still retain remarkable features of motorcycles in urban
traffic, while providing benefits of electric mobility and having potential of
developing intelligent transportation systems, effectively improving connection to the
public transport services at transit hubs.
However, the continuing growth of these emerging vehicles has been projected to
result in an accelerated burden on the distribution grid which is designed to meet the
expected growth rate of traditional load demand. Thus, in order to accommodate the
transition, research on solutions addressing this issue should be considered.
1.3 Rooftop solar power development in Vietnam and its impacts
With a high average annual total radiation, Vietnam is considered a place with
special potential for developing solar power (Figure 4).

10

United Kingdom

9

Republic of Korea

8

Vietnam

7

Australia

6

Italy

5

India

4

Germany

3

Japan

2

United States of America

1

PV Installed Capacity (2020)

China

13462.5
14574.8
16660.5
17983
21650
39042.7
53719
69764
73813.7
253417.8
0

100000 200000 300000

Installed Capacity (MW)

Figure 5 Top 10 countries by PV

Figure 4 Map of average daily global
horizontal irradiance (GHI) in Vietnam

installed capacity in 2020


5
In 2015, only 4 MWp of installed solar capacity for power generation was
available, of which about 900 kWp was connected to the grid [2]. In 2018, the total
solar power capacity was 106 MWp. However, by 2019, the capacity increased
dramatically to around 5 GWp, including nearly 0.4 GWp from rooftop photovoltaic
(PV) systems. By the end of 2020, the country's total PV capacity reached
approximately 16,500 MW [14], placing it among the top 10 nations globally (Figure
5). With regards to rooftop solar, there were 105,212 systems installed throughout the
country by December 2020, with a total capacity of 9,730.87 MWp [142].
However, it has been generally believed that once PV penetration exceeds a certain
limit, problems and challenges could arise, affecting the operation and security of the
grid. High PV penetration level affects the grid stability, triggering frequency and
voltage anomalies, overloading the existing infrastructure and mismatching demand
and supply [6], [74], [85], [86], [98], [100]. According to [14], about 365 GWh of
solar output was curtailed in 2020 as a result of balancing supply and demand.
In order to increase the hosting capacity of the grid, the utility could introduce
mitigation techniques or adopt grid optimization solutions to coordinate PV operation
with the rest of the grid. Besides, the power grid needs to be upgraded and flexibly
managed to better accommodate the RESs.
Another method to promote PV usage without affecting the distribution grid
operation is to encourage self-consumption, which was clearly mentioned in the PDP
VIII. With the target of 50 percent of buildings and residential houses utilizing
rooftop solar power for self-consumption by 2030, it would definitely be a challenge
that needs comprehensive solutions to reach.

1.4 PV-integrated charging stations – A solution for both E2W and rooftop solar
development
Generally, for the urban distribution grid in Vietnam, there are two factors that
might have significant impacts in the immediate future. Firstly, it is the remarkable
emergence of charging loads which are deferrable and not planned for the current
grid infrastructure. Secondly, it is the continuing popularity of distributed RESs


6
which possess stochastic and intermittent nature and are encouraged to self-consume.
The emergence of these two factors needs solutions to deal with and also leads to
opportunities as well as challenges for the
energy system.
Studies show that any form of EV such as
HEV (Hybrid EV), PHEV (Plug-in hybrid EV),
PEV (Plug-in EV) has lower emissions than ICE
counterparts. Noteworthily, the amount of
emissions depends on the proportion of clean

Figure 6 A PV-integrated E2W

energy supplied to the vehicle [42], [45], [50].

charging station.

If EVs are charged from the grid and if the grid electricity is primarily generated
by fossil fuels such as coal or natural gas, then the emissions are significant. Thus,
the adoption of EV only contributes significantly to the reduction of GHG emissions
if EVs are charged from RESs or from the grid with high share of renewable
electricity.

Wind power, solar power, hydropower, biogas, or tidal energy can be considered
as sustainable energy sources to power EVs. Regarding urban areas in Vietnam,
rooftop PV could be an attractive option because of the following factors:
1) Vietnam has a large potential of PV power with solar radiation reaching up to
5kWh/m2 and annual sun hour being from 1600-2600 hours [55]. Rooftop PV
is encouraged as it does not consume many land resources [119], [126].
2) The costs of PV module, hardware and inverter are continuously decreasing.
By Q1/2019, the cost of PV module was less than $0.3/Wp [89].
3) Since PV modules can be installed on the roofs close to the charging stations
or placed on/used as the parking lot’s roof, PV power can be accessed easily.
4) The combination of EV charging, and solar power can reduce the amount of
PV power injected into the distribution grid and, at the same time, satisfy
charging needs. Thus, it can help mitigate unwanted impacts of charging load
and high penetration level of RESs on the grid.