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

1 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 routes deployed in Hanoi city 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 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 Research objects: Urban electric trains have traction drive system integrated with supercapacitor energy storage device Research content: The thesis structure consists of 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 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 OVERVIEW OF SOLUTIONS FOR BRAKING ENERGY RECUPERATION 1.1 The announced researches on solutions for braking energy recuperation 1.1.1 Domestic research This is a very new field in Vietnam, so there are very few studies on optimizing the energy of urban electric train operation [60] 1.1.2 Overseas research Energy -efficient operation of electrified train Optimal speed profile 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, 72, 73, 75] b) Reversible substations Traction substations use active rectifiers for bidirectional energy flow to recuperate braking energy up to 18% [86], [22] c) Braking energy recuperation by timetable optimization: This solution does not require additional investment in infrastructure of the route, with the idea of using regenerative braking energy from a train operating in the braking mode to switch to trains operating in accelerating mode 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 dx With braking mode occuring in interval [tb, tc], 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 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 Traction substation DC Link ESS VSI Voltage source inverter IM Train Wheel 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 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 has been published by the author in the work [3] CHAPTER 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 centralized modeling system including:  Modeling lectric train  Modeling supercapacitor enregy storage system R day Substation R E tdk tdk 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 (Fwind), rolling friction resistance (Froll); slope resistance (Fgrad) The third rail, 750 VDC Feeder Air resistance force Train IM force Fig 2.9 Diagram of forces acting on electric train [1] Traction / braking force: Fig 2.11 Traction force /01 motor Fig 2.12 Electric braking force/01 motor Fig 2.14 Electric braking force regression/ 01 motor Resistance forces: FTr Faero mgsinα Froll α mg 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 W =F +F wind roll  The wind resistance force depends on train speed, size and shape, represented by the formula [93]: F = wind rC d Af Where: r is the air density; Cd is the air drag coefficient, determined by train shape; Af is the largest section of the train; v is train speed; vwind 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 Froll 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]: Froll = fr mg cos a where fr is rolling resistance coefficient b Gradient resistance force Fgra d : When the train operates on the slope, the gradient resistance force is calculated according to the formula [93]: Fgrad = mg sin( a) where: sin(a) = sin(arctan(ik )) ik (‰)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: ì ïdt ï ï ï ídx ï ïv ỵï ï In the (2.7): utr (2.7) - u br fbr (v ) - w (v ) - fgrad (x) ubr are control variables:u tr = utr Ỵ [0,1], ubr Ỵ[0,1]; The unit main resistance force (also called the unit basic resistance force) is represented by the David equation: w = a + bv + cv2 The a,b,c coefficients are supplied by the Manufacturer 2.1.1.3 Motion equation of tractive electrical motor Tel - TL The inertia torque of the train is calculated [59]: Jeq = Load torque when the motor operates in engine mode [59] =J (2.11) TL Load torque when the motor operates in generating mode [59]: (2.12) T= L 2.2 Supercapacitor energy storage device modeling Interleave DC- Modeling energy storage device includes supercapacitor modeling and 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 slow dynamics iL v sc Ii Ci Ri Ci0 Ci1 (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 Rd , Cd branch (with a minute time constant) and the branch containing RP (characteristic for long-term leakage current in self-discharge) as shown in Figure 2.22b See the two capacitors with equivalent capacitance Ci depending on the voltage ui in relation: C i (u i ) = C i + C i = C i + k v ui Given Ci=Csc, ui=usc, Ri=Rsc The mathematical model of supercapacitor is shown as follows: ì ï ï From the above analysis, five optimal control laws are designed: Full power (FP): utr = 1,ubr = Partial power (PP):utr Coasting (C): utr Ỵ [0,1], ubr = = 0,ubr = Full braking (FB): utr when p > when p = when < p < = 0,ubr = when p < 16 Partial braking (PB):utr =0 , ubr Ỵ [0,1] when p = Substitute Error! Reference source not found., (1.11) in (1.12) finding the differential equation for p = dp dx Full power mode: p > 1, distance xa , multiplier l Using equation Error! Reference source not found dp (3.84) dx ì ïdx ï ï ïdv í ï ïdt ï ï ïdv ỵ ï With initial conditions: x(0)=0; t(0)=0 (3.85) Partial power multiplier l Using equation (3.83): w ¢(v) - v From (3.75), then l = v 2w 0¢ Therefore, l = v (b + 2cv) If l is chosen previously, solve (3.88) to find the hold -speed vh Coasting mode:utr = 0,ubr = 0,0 < p < 1, finding braking speed vb, coasting time tc, coasting distance xc Coasting speed vb vb Where: j = v ⋅ w (v ), y = v ⋅ w 0¢(v) From (3.54) finding xc,tc = j¢(v 17 ì ïdx ï ï = ïdv -w (v ) - f í ï ïdt ï ï =- ïdv ỵ ï With t (v = v h ) = ta ; Partial braking mode (PB):utr Using equation (3.83) v p (t ) sc Therefore, l = -psc (t ) - p1 Full braking distance xb Using equation (3.84) dp (3.93) dx From (3.54) finding tb, xb ì ïdx ï (3.94) ï ïdv í ï ïdt ï ï ïdv î ï with t (v = vb ) = tb , x (v = vb ) Conclusion chapter In Chapter 3, designing the control structure of the Interleaved DC-DC converter ensures the charge-discharge process of supercapacitors, applying the Pontryagin's maximum principle to find the optimal switch points; from there, finding the optimal speed profile The results of chapter are presented in [1,2,4,5, 6,7,8,9] in the list of published works of the author CHAPTER SIMULATION AND EXPERIMENT RESULTS The simulation results on MATLAB/Simulink software will be presented in this chapter to verify the theoretical research results:  Effectiveness of SCESS in energy recuperation in braking mode ;  Comparison energy efficiency of train operation with /without PMP ;  Experimental results verify the working capability of the Interleaved DC-DC converter 18 4.1 Off-line simulation The simulation results of the control design mentioned in chapters and have two problems 4.1.1 Simulation Program of the electric train system installed On-board SCESS on Cat Linh-Ha Dong line The simulation results of operation modes of T1 train and T2 train are conducted with scenarios that fully demonstrate train operation situations on the following areas: Scenario 1: T1 train operates in braking mode t = 48s; T2 train begins operating in accelerating mode (V) (m/s) Speed profile of T1,T2 (m/s) Time (s) Fig 4.5 Dynamic behavior of DC-link voltage when T1 braking and T2 accelerating Energy loss of braking resistor of T1 without SCESS(Wh) Energy loss of braking resistor of T2 without SCESS(Wh) 125 150 100 100 75 50 25 50 Energy consumption of line source supplied T1 without SCESS (Wh) 4000 3000 Energy consumption of line source supplied T2 without SCESS (Wh) 2500 2000 1500 1000 500 2000 1000 Time(s) Time(s) Fig.4.6 Energy behaviors of T1 without SCESS, when T1 braking and T2 accelerating Fig.4.5, fig.4.6, fig.4.7 show voltage behavior of DC-link fluctuating from 700 to 900VDC, and energy loss of braking resistors of T1 and T2 is 4,3% Scenario 2: Both T1 and T2 operate in accelerating mode Fig 4.8 shows that UDC-link fluctuates in the range of 490 VDC to 900 VDC compared to the scenario The loss on the braking resistor of T1 and T2 is: 450 (Wh) / 4700 (Wh) = 9.6% shown in Fig 4.9, Fig.4.10 19 20 15 10 00 1200 1000 Time [s] Fig.4.8 UDC-link behavior when T1 and T2 accelerating Energy loss of braking resistor of T1 without SCESS(Wh) 400 450 300 300 200 150 -200 Energy loss of braking resistor of T2 without SCESS(Wh) 500 600 100 20 40 60 80 100 120 140 160 0 Energy consumption of line source supplied T1 without SCESS (Wh) 6000 4500 Energy consumption of line source supplied T2 without SCESS (Wh) 6000 4500 3000 3000 1500 00 Time (s) Time (s) Fig 4.9 Energy behavior of T1 when T1 and T2 are in accelerating mode Fig 4.10 Energy behavior of T2 when T1 and T2 are in accelerating mode Scenario 3: T1, T2 operate together in accelerating mode, the tration drive system integrated SCESS Fig.4.11 to Fig.4.13 show that UDC -link fluctuates in the range of 730 VDC to 770VDC, the loss on the braking resistor 12 (Wh) / 2400 (Wh) = 0.05% Thus, the regenerative braking energy part during braking mode was recovered by supercapacitors up to 9.6% Speed profile T1,T2 (m/s) 20 15 10 00 900 850 800 750 600 550 500 00 Time [s] Fig 4.11 UDC-link behavior when T1 and T2 accelerate and the train installs SCESS 20 Energy loss of braking resistor of T2 with SCESS(Wh) Energy loss of braking resistor of T1 with SCESS(Wh) 3000Energy consumption of supply line supplied T2 with SCESS (Wh) 3000 Energy consumption of supply line supplied T1 with SCESS (Wh) 2000 2000 1000 1000 Time (s) Time (s) Fig 4.12 Energy behavior of T1 when T1 Fig 4.13 Energy behavior of T2 when and T2 are in accelerating mode and T1 and T2 are in accelerating mode and integrated with SCESS integrated with SCESS 4.1.2 The optimal speed profile simulation program for train operation on Cat Linh - Ha Dong line applied PMP with electric train system integrated SCESS onboard Cat Linh-Ha Dong urban electric train line has 12 stations (corresponding to 11 areas), total length is 12.662 km, the train runs from the first station: Cat Linh, to the last station: new Ha Dong bus station a) A survey the train operation energy when the train does not have SCESS  A survey of energy consumption for running train from Cat Linh-La Thanh Fig 4.16 A comparison of optimal Fig 4.17 A comparison of speed profile with original speed distance versus time profile with/without PMP Fig 4.19 A comparison of energy consumption levels of train time with/without PMP operation with/without PMP The survey of energy consumption for the next station is similar to the first station Fig.4.18 A comparison of speed versus 21 Fig 4.60 A Comparison of optimal speed profile and original speed profile of 12 stations Fig 4.61 A Comparison of Optimal time profile and original time profile of 12 stations Table 4.3 Results of a comparison of energy consumption with / without energy optimization strategy PMP Inter-station length Cat Linh-La Thanh La Thanh -Thai Ha Thai Ha-Lang Lang-VNU VNU- Ring road Ring road 3Thanh Xuan Thanh Xuan-Ha Đong BS Ha Đong BS -BV Ha Đong BV Ha Đong -La Khe La Khe-Van Khe Van Khe-new Ha Dong BS Total: Total consumed energy when PMP is not applied: 176.24 kWh; 22 Total consumed energy when PMP is applied: 157.19kWh; energy saving: 10.8%; But the trip time lasts additionally seconds b) Conducting a survey of energy consumption when electric trains integrate SCESS, and ensure the fixed trip time by changing the Lagrange multiplier In this problem, consider a station, from Cat Linh - La Thanh station with a distance of 931m, trip time 68s Total consumed energy when PMP is not applied: 19.5kWh Total consumed energy when PMP is applied: 18.57kWh (saving 4.6%) Total consumed energy when applying PMP and having SCESS is 16.53 kWh (saving 15.2%), see Figure 4.66 Fig.4.62 Discharge/charge power of supercapacitor energy storage system Fig.4.63 optimal A comparison speed profile of with Fig 4.64 A comparison of speed versus time original speed profile Fig 4.65 A comparison of energy consumption levels of operation with/without PMP train Fig.4.66 A comparison of energy consumption levels of train operation with/without PMP and onboard supercapacitor energy storage system 23 Comment: Depending on modes of train operation, survey of train schedule, number of passengers, infrastructure of the route , which selects appropriate energy saving solutions 4.2 Designing experimental model of SCESS Designing the experimental model of electric train with SCESS is very expensive and complicated, so the author only designs the Interleaved DC-DC converter with switch branches in the working modes: Buck (charge) - Boost (discharge) in order to verify advantages of this converter Fig 4.69 SCESS experimental system Fig.4.71 PWM with d=0.625 Fig.7.42 Conductance coil currents cảm Fig.7.45 Conductance coil current with with d=0.625 d=0.33 Conclusion chapter Off-line simulations have demonstrated SCESS's role in saving energy for train operation by recovering regenerative braking energy, and contributing to voltage stability on the DC bus, the ability to apply optimal theory in saving energy Theses simulations create a premise for the application of solutions to use energy efficiency for Vietnam urban railway trains in the coming time The results of chapter are presented in the project [7,8,9] under the list of published works of the author 24 CONCLUSIONS AND RECOMMENDATIONS The thesis is the first research in Vietnam to address the issue of energy saving for urban electric train operation In this section, the author summarizes the new contributions of the thesis as well as points out the next development direction of the thesis Novelty contributions of the thesis  To propose the use of SCESS on-board integrated with traction motor drive via bidirectional DC-DC converter and design supercapacitor control according to train running characteristics  Applying the Pontryagin's maximum principle finds optimal transfer points of operating modes, determining the optimal speed profile of trains intergrated with SCESS on-board Recommendations and further research directions Some issues can be researched further to complete the thesis  Researching and combining supercapacitor energy storage device with high energy density storage systems such as batterry, flywheel, to expand the capacity of energy storage suitable for many different control strategies  Applying other control methods such as dynamic programing, weighting function method with the multi-objective problem to determine the optimal speed profile  Developing optimal control algorithm regulates many trains running on the route  Optimal control of energy operation when the train goes on the routes with slope changes  Optimal control of train operation when the speed profile vs time has S-curve shapes in both acceleration and braking processes ... 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:... solutions for braking energy recuperation 1.1.1 Domestic research This is a very new field in Vietnam, so there are very few studies on optimizing the energy of urban electric train operation [60]... sin(arctan(ik )) ik (‰)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