Modelling on Novel Cable Traction Power Supply System and Power Distribution Analysis
ABSTARCT :
Novel cable traction power supply system (NCTPSS) is a kind of long distance co-phase traction power supply system (TPSS), it can effectively solve problems caused by train's passing through electrical phase separation and improve utilization rate of regenerative energy in system, which is an ideal traction power supply mode. However, its structure is relatively complex due to cable power supply pattern, and internal power flow distribution mechanism still needs further study. In order to establish train-network coupling power flow calculation model, in this paper, two-port network model of each system component is established at first, then equivalent solid circuit model of the system is built by external cascade strategy and tearing nodal method. Then, power flow, the change of traction transformer power output and network voltage are analyzed under the condition that trains work in traction and regenerative braking condition, based on actual train operation schedule. The research shows that the proposed model can accurately calculate and detailed reflect electrical characteristics of NCTPSS, traction transformer capacity is effectively decreased compared with that needed in existing TPSS; Regenerative power can feed back to entire cable traction network and be reused by traction trains with high utilization rate inside NCTPSS.
EXISTING SYSTEM :
? This paper proposes a novel MMC-based advanced traction power supply system, which is expected to eliminate the neutral sections and solve power quality issues existing in the traditional traction power supply system.
? Due to the existence of the DC-bus, the high-density access and full utilization of distributed energies can be realized in the proposed system, which could bring surprising changes to the traction power supply system.
? On the one hand, the cost of power transmission can be reduced. On the other hand, due to the existence of DC-bus, abundant renewable energies such as wind energy and solar energy along the railway could access easily.
DISADVANTAGE :
? Their high power consumption has brought about a problem of insufficient power supply capacity (PSC) of the single-phase 25 kV or 2 × 25 kV alternating current (AC) traction power supply systems (TPSSs) that are widely adopted to feed trains.
? If a TPSS does not have enough PSC, locomotives and EMUs would not be able to operate normally.
? The high power requirements have brought about the problem of insufficient power supply capacity (PSC) of traction power supply systems (TPSSs).
? Thus, a convenient method of PSC assessment is meaningful and urgently needed. In this paper, a novel algorithm is proposed based on the Thévenin equivalent in order to calculate the PSC.
PROPOSED SYSTEM :
• A novel MMC-based advanced co-phase traction power supply system is proposed in this paper to solve power quality issues and eliminate the neutral sections in the traditional traction power supply system.
• In order to ensure the normal operation of the proposed system, nearest-level modulation considering voltage balancing is designed for MMCs.
• SMs of many other structures have also been proposed according to different application requirements such as high efficiency, dc-fault current blocking, and smaller capacitor voltage ripple.
• A combination of NLM and PWM is proposed in, which inherits the advantages of both NLM and PWM.
ADVANTAGE :
? Electric railways, as an environmentally friendly and efficient means of producing passenger and freight services, have been selected by many countries.
? Compared to conventional algorithms, the proposed one has the advantages of fast convergence and an easy approach to multiple solutions and PV curves, which show vivid and visual information to TPSS designers and operators.
? If a TPSS does not have enough PSC, locomotives and EMUs would not be able to operate normally.
? For the sake of the safe and efficient operation of electric railways, it is essential to calculate and assess the PSCs of TPSSs; hence, a technical scheme is urgently required.
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