VỀ một GIẢI PHÁP điều KHIỂN QUÁ TRÌNH TRAO đổi NĂNG LƯỢNG hãm của tàu điện ĐƯỜNG sắt đô THỊ VIỆT NAM tiếng anh

Therefore, the author selected the topic with the name: "About a solution to control the energy exchange process of Vietnam urban railway electrified trains" with the aim of saving energ

INTRODUCTION

1, The urgency of the thesis: Electric transportation with outstanding advantages

is the ability to transport large passengers, reduce environmental pollution, reduce traffic congestion [63,78] In Vietnam, the planned urban railway network in the near future has 5 routes deployed in Hanoi city 6 routes in Ho Chi Minh city However, the energy required to operate urban railway is up to billions of kWh Therefore, the goal

of energy saving on train operation is a very urgent issue, with high scientific and practical significance, but so far, no research group in Vietnam has proposed energy saving solutions operate urban electric trains Therefore, the author selected the topic with the name: "About a solution to control the energy exchange process of Vietnam urban railway electrified trains" with the aim of saving energy by a solution for regenerative braking energy when the train operates in braking mode and in combination with the optimal theory of determining the optimal train speed profile

2 Research objectives: Introducing energy saving solutions in electrified train

operation Thereby, proposing solutions suitable to the characteristics and conditions

of Vietnam's urban railways; and applying these solutions for Cat Linh-Ha Dong urban railway to assess saving energy

3 Research objects: Urban electric trains have traction drive system integrated with

supercapacitor energy storage device

4 Research content: The thesis structure consists of 4 chapters

- Chapter 1: Overview of braking energy recuperation solutions: Synthesizing, analyzing previously published works, thereby proposing research directions, research objects, and developing solutions to solve research problems

- Chapter 2: Implementation of modeling of electric train and supercapacitor energy storage system

- Chapter 3: Strategies for optimal control of train operation energy with trains integrated supercapacitor energy storage system (SCESS)

- Chapter 4: Verification of the correctness of theoretical research through simulation results on Matlab software with parameters of Cat Linh - Ha Dong urban electric train line, and an experimental part of Interleaved DC -DC converter in SCESS

- Finally, some conclusions and further research directions of the thesis are presented

in the conclusions

5 The novelty of the thesis:

 Proposing SCESS on board integrated with traction motor drive system via Interleaved bidirectional DC-DC converter and designing supercapacitor control according to the operation characteristics of a railway vehicle

 Applying Pontryagin's maximum principle to find optimal transfer points of operating modes, determine the optimal speed profile of train operation using supercapacitors on board

CHAPTER 1 OVERVIEW OF SOLUTIONS FOR BRAKING ENERGY

RECUPERATION 1.1 The announced researches on solutions for braking energy recuperation

Energy -efficient driving

Regenerative braking energy

Energy storage device

optimised timetables

Energy-Optimal speed profile

Eco-driving tools: ATO, DAS

Hình 1.7 Strategies for effective management of train operation energy Studies have shown that there are two groups of solutions with higher energy-saving percentages: Regenarative recuperation solutions and energy efficient driving solutions [31]

1.1.2.1 Research on regenrative braking energy recuperation

a) Regenerative braking energy recuperation by energy storage device

The supercapacitor energy storage system (SCESS) is installed onboard, at the traction substations, or at points along the train track to recover regenerative braking energy when the train operates in traction mode [9, 12, 21, 25, 44, 45, 46, 53, 58, 66, 68, 69,

Typically, Subin Sun (2017) [71] combines the operation of two trains in the same station, recuperating the regenerative braking energy represented by the power ( )q t in

the motion equation:v dv u f vf ( ) q t ( ) / v u b vb ( ) r v ( ) g x ( )

With braking mode occuring in interval [tb, tc],

0 ( ) ( ) 0

1.1.2.2 Energy - efficient driving

a) Determining the optimal train journey on the route

- The research team of the University of South Australia including Howlett, Benjamin, Pudney, Albrecht, Xuan has determined the optimal speed profile through finding the optimal transfer points with 5 control rules taking into account the actual conditions

on the route such as the slope, the speed limit, etc., it is possible to find the optimal time and distance at each train operation mode

Comment: The research team of the University of South Australia in published studies does not mention the problem of train running on time

Hai Nguyen (2018) [2] applied PMP to trains with long-distance diesel locomotives, found the optimal speed profile corresponding to the lines with different slopes, and in the objective function also mentioned to the station problem on time

Comment: In his thesis, Hai Nguyen does not mention the problem of recovering braking energy

1.2 Selecting the research direction and the tasks solved of the thesis

Through analysis of published works, there are no works that combine both the regenerative braking energy recuperation solution by ESS and the optimal speed profile determination with the on-board ESS while ensuring fixed trip time

Therefore, the author proposes the selected structure for research

Braking energy recuperation Technology Energy converter system stratergies Control

DC Link

IM

Train Wheel

Traction substation

- Control charge/

discharge of supercapacitor

- PMP for train with board SCESS, finding optimal speed profile.

On-ESS VSI

- DC-AC converter

- DC-DC converter

Voltage source inverter

Fig 1.14 The selected structure for research

 Technology: Learning about technology of electric train operation in some urban railway lines in Vietnam; namely, urban railway of Cat Linh - Ha Dong line

 Energy conversion system on electric trains: focusing on studying Interleaved DC-DC converter in an effort to ensures energy exchange between supercapacitor and traction drive system

 Control strategies: Proposing the control method for Interleave DC-DC converter ensures the charging-discharging mode of supercapacitors suitable for train

running characteristics Proposing PMP to determine the optimal speed profile for train operation

Conclusion of chapter 1

By synthesizing and analyzing a number of domestic and foreign research works on energy saving solutions, the author has analyzed and selected the research object as an urban electric train integrated on-board SCESS and proposed independent control strategies for each train; proposed to control regenerative braking energy recuperation

by managing the charging / discharging mode of supercapacitors; using Pontryagin's maximum principle to optimize train operation energy with hybrid power systems These suggestions will be verified by MATLAB simulation software

The summary content of Chapter 1 has been published by the author in the work [3]

CHAPTER 2 MODELING ELECTRIC TRAIN AND SUPERCAPACITOR

ENERGY STORAGE SYSTEM

The accuracy and characteristics of the mathematical model is the core factor determining the quality of the system So in Chapter 2 centralized modeling system including:

 Modeling lectric train

 Modeling supercapacitor enregy storage system

Substation

Overhead contact line

Pantograph

DC-DC converter

Fig 2.1 Electrical drive configuration equipped with SCESS

2.1 Modeling electric train and SCESS

2.1.1 Modeling electric train

Modeling the train needs to calculate the forces affecting train motion, the traction motor drive system to make the wheel movement

2.1.1.1 The forces act on the train

The forces acting on the train include: The main resistance force including wind

resistance (F wind ), rolling friction resistance (F roll ); slope resistance (F grad)

IM Train

Feeder

Gear

The third rail, 750 VDC Air resistance force

Wheel

Traction force

railway Friction

force

Motor torque

𝛂 Gravity

Fig 2.9 Diagram of forces acting on electric train [1]

Traction / braking force:

Fig 2.11 Traction force /01 motor Fig 2.13 Traction force regression/ 01

Fig 2.16 Forces acting on train

a The main force W0: The main resistance force (also known as basic resistance force) includes wind resistance and friction force

Where: r is the air density; C d is the air drag coefficient, determined by train shape;

Af is the largest section of the train; v is train speed; v wind is wind speed; b is the sharp

angle created by the direction of the wind velocity with the movement of the train

 Rolling resistance force F roll

For simplicity, consider rolling frictional force only on hard track and consider

the ideal case that all wheels have the same conditions At this time, rolling friction

force can be calculated as follows [93]: F roll = f mg r cosa (1.3)

where f ris rolling resistance coefficient

b Gradient resistance force F grad : When the train operates on the slope, the gradient

resistance force is calculated according to the formula [93]: F grad =mgsin( )a (1.4)

where: sin( ) a = sin(arctan(i ))k

k

i (‰)is the ratio of slope height to slope, a is the slope of the track

2.1.1.2 Dynamic equation of the train

The motion equation of the train is often transformed into its own form of impact force

converted into the mass unit of the train as follows:

The unit main resistance force (also called the unit basic resistance force) is represented

by the David equation: 2

0

The a,b,c coefficients are supplied by the Manufacturer

2.1.1.3 Motion equation of tractive electrical motor

wh eq

D m J

W or2

h m

m mech

D K

2.2 Supercapacitor energy storage device modeling

Modeling energy storage device includes supercapacitor modeling and Interleave

DC-DC converter modeling

2.2.4 Supercapacitor modeling

Supercapacitors replaced by equivalent electrical circuit model include many parallel

branches [32] Two RC branches provide two time constants to describe the fast and

(a) (b) Fig 2.22 Simple equivalent supercapacitor circuit

As the above analysis, supercapacitor dymamic is considered for a short period of time,

ignore the R C d, d branch (with a minute time constant) and the branch containing R P

(characteristic for long-term leakage current in self-discharge) as shown in Figure 2.22b

See the two capacitors with equivalent capacitance C i depending on the voltage u i in

Given C i =C sc, u i =u sc, R i =R sc

The mathematical model of supercapacitor is shown as follows:

( ) ( ) ( )

(0) ,max( ) ( ) ( )

2.2.5 Interleaved DC-DC converter modeling

Non-isolated bidirectional DC-DC converter consists of parallel branches (also called

Interleave DC-DC converter) suitable for high-power, high-voltage drives

2.2.5.1 Power circuit structure of Interleaved DC-DC converter with three

switch branches

Supercapacitor performs the process of energy charging / discharging through the

Interleaved DC-DC converter with three switch branches as shown in Figure 2.24

S BK1

S BS1

S BK2

S BS2 DBS2

DBK2

S BK3

S BS3 DBS3

Fig 2.24 Power circuit structure of Interleaved DC-DC converter

The configuration of Interleaved DC-DC converter includes half-bridges (HBs) in parallel, as shown in Figure 2.24 with three parallel H-bridge halves: HB1, HB2, HB3

In order to SCESS charges/discharges according to the train characteristics, the Interleaved DC-DC converter needs to work in two modes: Boost mode, Buck mode

2.2.5.2 Modeling bidirectional DC-DC converter with one switch branch

The Interleaved DC-DC converter operates with assumptions: IGBTs are ideal, converter operates in continuous current mode; conventionally, current positve direction flowing through the inductance coil regards as charge state of SC, and vice versa regards as discharge state, the current mode of Interleaved DC-DC converter is equivalent with the current mode of DC-DC converter with one switch branch as shown in Figure 2.30a and apply the small - signal averaged method to model Interleaved DC-DC converter

The averaged representation of the bi-directional switching power-pole in fig.2.30a is

an ideal transformer shown in fig.2.30b with a turns -ratio 1:d(t), where d(t) represents the duty-ratio of IGBT

DC-BS

S L

i

BK

D

Buck Boost

SC R

DC link

u

-inv i

1 ( )

i t L

1 ( )

u t u t2 ( )

Fig.2.30a Average dynamic model of the

switching power-pole with bi-directional

power flow

Fig 2.31 Equivalent electrical circuit of one switch branch bidirectional DC-DC converter averaged model

In fig.2.31, applying the Kirchhoff's fisrt, second law; the state equation of converter is describled as follow:

In SCESS modeling, performing supercapacitor and Interleaved DC-DC converter modeling with 3 switch branches The content of chapter 2 presented in the work [6] under the list of published works of the author

CHAPTER 3 OPTIMAL CONTROL OF ENERGY CONSUMPTION OF

ELECTRIFIED TRAIN INSTALLED SUPERCAPACITOR

In chapter 3, the control structure of train operation energy is proposed with the goal

of saving energy: Designing Interleaved DC-DC converter control enables SCESS to recuperate regenerative braking energy Using optimal algorithm determines train speed profile when train has integrated SCESS

traction substation A substation B Traction

Traction motor drive

DC DC

Traction, resistance,braking forces

Fig 3.1 The overall control structure of train operation energy

3.1 Control DC-DC Interleaved DC-DC converter

240 deg phase delay

Fig 3.6 Two -loop cascaded control structure for Interleaved DC-DC converter

Designing control law for Interleaved DC-DC converter structure according to average

current mode, with PI controllers both inner-loop and outer-loop

3.1.1 Design of current - loop controllers

The goal is to design the controllers so that the average current flowing through the

inductance coil i Ltracks a certain reference *

L

i Designing the inner-loop is in three steps

Step 1: Determine the state equation of the bi-directional DC-DC converter in the

average model rewritten as follows:

Step 2: Determine the operating points by giving the left derivative of equation (3.1)

equal to zero and the quantities are in the steady state

10

10

Solving equation (3.2) finds operating points (I U Le, DC link e- ) corresponding to measured

voltage of supercapacitor U SCand duty-ratio D

Step 3: Linearize the first equation of equations (3.1)

Since the model (3.1) is nonlinear, it is recommended to design the controllers according

to linearization method around the operating point

The transfer function between the inductor current and the duty-ratio considered on

the small-signal domain is calculated as follows:

G s

s R

++



Where: DC linke

C

L

U k

R

=

Beacause the transfer function (3.6) has a first-order, the PI controller may be

effectively used to ensure both zero steady-state error and controlled bandwidth With

the PI set, the controller is described as follows:

R L k

ïïïí

3.1.2 Design voltage-loop - control U DC-link

Designing the voltage-loop is to control the voltage u DC link- sticking value *

DC link

u - with

*

DC link

u - being constant by the nominal working voltage according to the traction power

standard EN 50163 and IEC 60850 Designing control is the same current loop; the

transfer function between DC-link voltage and inductor current is:

( )( )

DC linke IV

inve

DC linke pV

SC

CU T

I CU k

U

-ìïï = ïï

-ïïí

-ïïïïî =

3.1.3 Verifyting the design of the Interleaved DC-DC converter

Through simulation results figures 3.7, 3.8, and 3.9 having validated the design

of the two control loops of charge-discharge modes of supercapacitors according

to the operating characteristics of train The train's trip time from Cat Linh to

La Thanh station is 68s, when the train operates in accelerating mode from 0 to 28s, the current on supercapacitors is positive, it shows that the supercapacitors are discharging to support the train in traction mode; from 28 to 48s supercapacitor current is equal to zero, respectively, the train operates in coasting mode; from 48 to 68s train operates in the braking mode, the current

300 400 500 600 700

-1000 -500 0 500 1000

Fig.3.7 Values of current i L in each

branch and total current

Fig.3.8 State of charge, voltage, current

of a SC module in a process of running train

Fig 3.9 Charge-discharge of supercapacitor when train integrates SCESS

With different train operation speeds, p tsc( )obtained in charge-discharge mode also has different values

3.4 Designing a problem of optimal control of train motion according to Pontryagin' maximum principle

Using Pontryagin's maximum principle determines optimal speed profile, thereby determining the saving energy compared to the speed control profile without control