A Modularized Multi-level AC-DC-AC Traction Power Supply System

A traction power supply system, modular multi-level technology, applied in the direction of AC power input conversion to AC power output, electrical components, circuit devices, etc., can solve problems such as nonlinearity, low power factor, excessive phase problems, etc. Controllable frequency amplitude, high reliability, and the effect of solving harmonics

Active Publication Date: 2019-03-12
BEIJING JIAOTONG UNIV +1
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0003] (1) Harmonic problem: AC-DC electric locomotive is a nonlinear, low power factor load
This kind of electric locomotive adopts diode or thyristor rectifier, which has large harmonic content and low power factor, and will inject various harmonic currents into the traction power supply system and power system, becoming a harmonic source
[0004] (2) Reactive power problem: the power factor of AC-DC electric locomotive is low. If no compensation device is added, it is usually only about 0.8 during traction; the locomotive is over-powered and phase-separated to generate an exciting inrush current, which can be regarded as a pure inductive current, and the phase angle is close to 90. Under normal working conditions, the large changes in the phase angle and the sharp fluctuations in the traction load current increase the difficulty of effectively compensating for reactive power
[0005] (3) Negative sequence problem: The reason for the negative sequence is load imbalance. On the one hand, the power grid is a three-phase power supply; on the other hand, the locomotive load is single-phase and has random and violent fluctuations
[0006] (4) Excessive phase problem
Due to the high voltage level and large capacity of the traction power supply system, the traditional power electronics-based power conversion device requires a transformer on the input and output sides, and the transformer is expensive, bulky, and occupies a large area

Method used

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  • A Modularized Multi-level AC-DC-AC Traction Power Supply System
  • A Modularized Multi-level AC-DC-AC Traction Power Supply System
  • A Modularized Multi-level AC-DC-AC Traction Power Supply System

Examples

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Effect test

Embodiment 1

[0030] Embodiment 1: A modular multi-level AC-DC AC traction power supply system, such as figure 1 Shown.

[0031] The three-phase step-down transformer absorbs three-phase electrical energy from the power grid, and outputs single-phase 27.5kV electrical energy through a modular multi-level AC-DC converter (MMC AC-DC converter). This scheme interconnects the traction network to form a power supply network independent of the public grid, which can realize the power supply through the whole line. The output of the substation is single-phase AC, and the output voltage amplitude, frequency and phase are controllable. The structure and wiring of each traction substation are exactly the same. The phase separation insulator can be eliminated, the automatic phase separation device can be omitted, and the hidden safety hazard in the phase separation of high-speed trains is eliminated, and it is suitable for high-speed train operation. Realize the 3AC-DC-1AC conversion of electric energy...

Embodiment 2

[0032] Example 2: Such as figure 1 , figure 2 , Figure 3(a) and Figure 3(b) show a modular multi-level AC-DC AC traction power supply system. The high-voltage side of the three-phase step-down transformer of the system is connected to the three-phase public grid, and the low-voltage side output is disconnected by the switch The converter is connected with a modular multi-level AC-DC AC converter (MMC AC-DC AC converter) as the input of the converter. The three-phase AC electric energy is converted into single-phase AC electric energy through the MMC converter through AC-DC-AC, and is connected to the traction network through the switch circuit breaker. On the other hand, the low-voltage output side of the step-down transformer is connected to the traction network in two phases through the switch circuit breaker, and there is a phase separation area between the two phases. The system can realize 3AC-DC-1AC two-way conversion of electric energy, and the phase frequency amplitud...

Embodiment 3

[0034] Example 3: Such as figure 1 , figure 2 , Figure 3 (a) and Figure 3 (b), a modular multi-level structure of AC-DC AC traction power supply system, the operation mode is divided into normal mode and failure standby mode, such as figure 1 Shown. In the normal mode, the first switch breaker S1, the second switch breaker S2, and the fourth switch breaker S4 are closed, and the third switch breaker S3 is opened. The three-phase step-down transformer absorbs three-phase high-voltage electric energy from the public grid and converts it into three-phase low-voltage electric energy and sends it to the MMC AC / DC converter. The rectifier station of the converter converts the three-phase electric energy into direct current, which is then reversed by the inverter station. A single-phase alternating current with controllable amplitude, phase and frequency is transformed and sent to the traction network for locomotives to fetch flow. Since the split phase area is bypassed by the fourt...

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PUM

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Abstract

The invention discloses an alternating current-direct current-alternating current (AC-DC-AC) tractive power supply system with a modularized multi-level structure, and belongs to the technical field of an electrified railway. The high voltage side of three-phase voltage-reduction transformer of the system is connected with a three-phase public power grid; the low voltage side output passes through a first switch circuit breaker and is connected with an MMC AC-DC-AC current converter to be used as the input of the current converter; three-phase alternating current electric energy is subjected to AC-DC-AC conversion by the MMC AC-DC-AC current converter to be converted into single-phase alternating current electric energy to be output, and is connected with a traction network through a second switch circuit breaker; furthermore, the low voltage output side of the three-phase voltage-reduction transformer of the system passes through a third switch circuit breaker and is divided into two phases that are connected with the traction network; a phase-separating section is arranged between the two phases; and a switch circuit breaker is connected with the phase-separating section in parallel. According to the AC-DC-AC tractive power supply system, the electric energy 3AC-DC-1AC bidirectional conversion can be realized; low-interference isolation or zero-interference isolation between an electric power system and the tractive power supply system is achieved; a boosting transformer is not required for the system output; and the problems of harmonics, reactive power and negative sequence in the tractive power supply system are solved, and bidirectional conversion with the power grid electric energy is realized.

Description

Technical field [0001] The invention relates to an AC-DC-AC traction power supply system with a modular multilevel structure, belonging to the technical field of electrified railways. Background technique [0002] At present, my country's traction power supply system adopts a three-phase-two-phase power supply mode, that is, a three-phase-two-phase step-down transformer is used to obtain electricity from a three-phase power grid, and the electrical energy is output from two power supply arms after stepping down. There are many power quality problems in this power supply mode: [0003] (1) Harmonic problem: AC-DC electric locomotive is a nonlinear, low power factor load. This kind of electric locomotive adopts diode or thyristor rectifier, which has high harmonic content and low power factor. It will inject various harmonic currents into the traction power supply system and power system, and become a harmonic source. [0004] (2) Reactive power problems: AC-DC electric locomotives h...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): H02J3/00H02M5/458
CPCH02J3/0073H02M5/4585
Inventor 吴命利刘秋降李静杨少兵张洪和
Owner BEIJING JIAOTONG UNIV
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