This project entitled "DEVELOPMENT OF ENERGY RECOVERY SYSTEM FOR THE THIRD RAILWAY DC SYSTEM" was prepared by SITI FARHANA BINTI FARIDUDIN and submitted as partial fulfillment of the requirements for the degree of Master of Engineering (Electrical) at Universiti Tunku Abdul Rah. Department of Electrical and Electronic Engineering Lee Kong Chian Faculty of Engineering and Science Universiti Tunku Abdul Rahman. Chua Kein Huat (Supervisor) from the Department of Electrical and Electronics Engineering, Lee Kong Chian Faculty of Engineering and Science, Lee Kong Chian Faculty of Engineering and Science.
Research objectives
By referring to the amount of regenerative braking, we will determine the suitable recovery system available in the market to ensure that some of the regenerative braking will be fed back into the system. Design of the regenerative system will not be discussed in depth in this research, as the development of simulation will be more focused on studying the amount of regenerative braking produced in the DC railway system. One of the earliest solutions was that the energy would be dissipated as heat through an on-board resistor or side resistor unit to avoid damage to the electrical train equipment.
Train Time Table Optimization
By optimizing the operating schedule, peak power consumption will be reduced and the use of regenerative braking can be increased. The storage system must absorb and store regenerative braking energy and discharge it when required. However, the size of the super capacitor depends on the amount of braking regenerative energy absorbed.
Reversible Substation
The TCI is an anti-parallel thyristor controlled rectifier (TCR) connected in reverse to provide a path for transferring energy from the DC side to the AC side. The inverter acts as an active filter when the RTCR works in the forward direction (AC/DC), while the rectifier works only in pull mode. The Enviline TCR is the Traction Control Rectifier that uses four (4) quadrant converters to provide a reverse path for energy flow in the substation.
The Enviline ERS is a roadside energy recovery system consisting of an IGBT-based inverter connected in parallel with the existing substation rectifier to return excess energy to the main grid. 3 summarize the differences between the inverter technologies available on the market and the proven results installed in various railway projects. In the paper (Cascetta et al., 2021), line 10B of the Metro de Madrid introduced a 2MVA anti-parallel DC/AC converter in one of the existing 3MVA rectifier stations to create a bidirectional power flow.
With the new reversible substation design, redundant regenerative braking control will prioritize traction feedback for nearby train use before excess power is fed back into the internal AC network. Another study in (Krim et al., undated) done on the Massena C substation line of the Paris suburban railway, the inverter is installed in parallel with the 12-phase diode rectifier as in Figure 2. The inverter will operate mostly during the conditions of low traffic, where it will return maximum regenerative energy to the AC grid.
In this case, the inverter will help to maintain the DC supply voltage in the acceptable limit that the electric train can handle.
Introduction
The Ampang Line LRT, Kelana Jaya Line LRT and MRT Kajang Line use AARU and a resistor bank system to maintain the voltage of the 3rd track system by converting excess energy into thermal energy that is released into the air. Compared to a traction system that uses an energy recovery system, the excess energy will be feedback to the system and can be used for domestic supply as well as traction. Thus, this will reduce the energy consumption of the electricity provider such as Tenaga Nasional Berhad (TNB).
Since most power equipment will undergo an upgrade process after about 15 years of operation, this is a good opportunity to investigate the improvement of the traction substation. Some traction substations can be upgraded with an inverter system or an energy storage system to restore the regenerative braking of the electric train, as was done in the Bangkok Metro (Ratniyomchai and Kulworawanichpong, 2017).
Circuit Modelling
DC Power Supply
The DC power supply for the electric train will be 750V DC, which is rectified from the 33kV AC supply through the three winding rectifier transformer and a rectifier. There will be two (2) sets of rectifiers and rectifier transformers connected to the same bus bar to create 24 pulse firing angle as shown in figure 3. Total length of trace is approx. 4300m, each track bound with bend radius and elevation is omitted in this simulation to reduce complexity.
However, there are civil speed limit numbers placed along the track that represent the location of the radius of the bend in the track area as shown in Appendix A. The distance between stations is more or less similar to the MRT Kajang track distance listed in Table 3. In this simulation, we will used the rolling stock for direct current, as the track is designed with the direct current system of the 3rd rail.
In the ETAP software, the required DC drive specifications, including traction force and regenerative braking characteristic, must be filled in the library data for our simulation purposes. In this case, the parameters of the DC motor vehicles used for this simulation are listed in Table 3. 4 is a plot of the tractive effort data entry in relation to the speed in Table 3.
5 is the plot of regenerative braking power with respect to the speed data as in Table 3.
Non-Regenerative Braking Train
- Simulation Result
- Simulation Result
- Tractive Effort and Speed
- Power, Energy and Speed
12 is a good representation of a train without a regenerative braking system, since the energy is constant during the deceleration of the train before stopping at the next platform. Another simulation was done by enabling the regenerative braking capability of the rolling stock to observe the result based on the regenerative braking of the electric train. Regenerative braking means that the train will use electrical braking before coming to a complete stop using mechanical braking.
In addition, the brake management in the regenerative train ensures that the tension of the 3rd rail remains within the permitted tolerance and that the passengers can ride comfortably. Based on Figure 4.14, the train consumes 2800A while the train is running and produces approximately 2000A to 2500A of regenerative braking before sustaining approximately 220A during the complete stop of the train at the platform. Either regenerative braking or non-regenerative braking, the behavior of tractive effort and speed while the train is running is the same.
In this section, we can see that the current is in a negative region, proving regenerative braking by the electric train. In this section there is a significant difference in power and energy compared to non-regenerative braking simulation. On December 23, when the train starts to brake, the regenerative braking energy drops from 60 kWh to 35 kWh, resulting in a total of 25 kWh of regenerative braking energy from the electric train.
With the amount of energy produced, these regenerative brakes can be used back into the power supply system using an inverter to convert from DC to AC supply or stored in a battery energy storage system at the voltage supply level DC.
Conclusion
Based on the result and the discussion in Chapter 4, we can roughly estimate the capacity of the battery packs to include in the system for future upgrades. Based on the result in Chapter 4, the amount of about 2000A to 2500A instantaneous current and 25kWh energy from the regenerative braking is significant to use a better recuperative energy storage system for reuse in the traction power supply system. Not to mention that an inverter system is much cheaper than the battery energy storage system.
However, due to the possibility of harmonic effects in the AC supply system and the current limitation of traction substation space, we can study the adoption of battery energy storage system which can be used at the DC power supply level. for train acceleration and during an emergency supply. event. To properly size the capacity required for the energy recovery system, the train and track information must be available and the software must be able to successfully run the simulation. However, since the information based on MRT Kajang line is limited, so the simulation is only performed on the power supply ring of four (4) stations with track information is limited to civil speed limit information only.
Based on this research, the simulation can be improved by obtaining all the required information about the electric train used on this MRT Kajang Line track, as well as the complete information of the track system to determine the actual regenerative braking from the actual train. operation. In addition to using a software simulation method, the researcher can also install an oscilloscope recorder such as HIOKI at the traction substation to obtain the real-time reading of the voltage and current during regenerative braking of the train. This method will be more accurate in determining the appropriate regenerative braking management method suitable for train operation as well as regenerative system sizing. 2019) 'Energy Efficient Operation of Light Rail Transit (LRT).
A Single Line Case over Istanbul Metro Network', IEEE Conference on Intelligent Transportation Systems, Proceedings, ITSC, 2018-November, pp. 2017) "A Strategy for the Utilization of Regenerative Energy in Urban Railway Systems by Application of Smart Train Scheduling and Wayside Energy Storage System", Energy Procedia, 138, pp. 2019) 'Modeling and simulation of a reversible substation for the recovery of regenerative braking energy in rail transport systems'. 2019) 'Recovery of regenerative braking energy in electric rail transport systems', IEEE Transactions on Intelligent Transportation Systems, 20(8), pp. no date) 'Comparative study of two control techniques of regenerative braking power recovery of inverter-based DC railway substation Keywords', pp. 2008) 'A Study for Improving Performance of Electric Braking for Electric Train', 2008 International Conference on Control, Automation and Systems, ICCAS 2008, pp. 2021) 'A little flexibility on progress distribution is enough: Data-driven optimization of subway regenerative energy', Information Sciences, 554, pp. 2017) 'Study on control strategy of urban rail train with on-board regenerative braking energy storage system', Proceedings IECON 2017 - 43rd Annual Conference of the IEEE Industrial Electronics Society , 2017-Janua, pp. 2017) 'A Comprehensive Review of Flywheel Energy Storage System technology', Renewable and Sustainable Energy Reviews, 67, pp. 2021) 'Traction Energy Storage Systems Supporting Energy-Saving, Safe, and Resilient Railway Infrastructure', 76(4), pp. 2017) 'A Demonstration Project for Installation of Battery Energy Storage System in Mass Rapid Transit', Energy Procedia, 138, pp. 2018) 'A Survey on Energy-Efficient Timetable Optimization Model Based on the Utilization of Regenerative Braking', ISMSIT 2018 - 2nd International Symposium on Multidisciplinary Studies and Innovative Technologies, Proceedings, pp.
