Traction Power Converter Multi-Voltage Rail Vehicle
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Solution Overview
Problem
Rail vehicles face challenges in efficiently operating across multiple AC and DC electrified sections with different voltages, leading to reduced traction inverter output at low voltages and increased costs for auxiliary power supplies due to the use of high-voltage semiconductors, resulting in inefficient and costly apparatuses.
Innovation Solution
A traction power converter system utilizing high-voltage semiconductor devices, such as IGBTs capable of withstanding 6500 V, to simplify power conversion across multiple voltage systems, including DC 3000 V, by reusing components like the traction transformer and chopper reactors, and optimizing circuit switching to maintain high traction inverter output and reduce auxiliary power supply costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a high-voltage semiconductor is used in the auxiliary power supply to support high DC catenary voltage, then the auxiliary power supply can operate at high voltage, but the cost increases
Solution Approach 1:
The power conversion system is divided into two independent paths: a high-voltage path for the traction inverter and a low-voltage path for the auxiliary power supply. The voltage conversion means creates separate voltage levels, allowing each subsystem to use appropriately-rated semiconductors without requiring the auxiliary power supply to use expensive high-voltage devices.
Solution Approach 2:
Different voltage levels are provided to different subsystems according to their specific requirements. The traction inverter receives high voltage (3000V or 1500V) for high-power output, while the auxiliary power supply receives low voltage (600V or lower) for cost-effective operation. Each subsystem is optimized for its specific voltage level.
2Power
If the input voltage to the traction inverter is kept high to achieve high vehicle output, then the traction performance is improved, but the apparatus complexity increases when supporting multiple voltage systems
Solution Approach 1:
The voltage conversion means is designed to perform multiple functions: it can step up voltage from 1500V to 3000V, step down voltage from 3000V to 1500V, and provide both voltage levels simultaneously. This single multi-functional device replaces what would otherwise require multiple separate converters, reducing overall system complexity.
Solution Approach 2:
The voltage conversion means dynamically adjusts voltage levels based on the catenary voltage and the requirements of the traction inverter and auxiliary power supply. The system can adapt its operation mode (step-up, step-down, or direct pass-through) to match the input voltage conditions, maintaining optimal performance across different operating scenarios.
3Adaptability or versatility
If separate apparatuses are installed for different voltage systems, then the vehicle can pass along multiple electrified sections, but the apparatus size and cost increase significantly
Solution Approach 1:
The voltage conversion means combines multiple voltage conversion functions (3000V to 1500V, 1500V to 600V, and reverse conversions) into a single integrated apparatus. This consolidated design provides multi-voltage system compatibility while occupying less space than multiple separate voltage converters would require.
4Reliability
If DC voltage is stepped up and then converted again to low voltage for the auxiliary power supply, then the auxiliary power supply can operate at appropriate voltage, but the efficiency decreases due to multiple power conversion stages
Solution Approach 1:
The voltage conversion means performs the voltage conversion to the appropriate level (600V or lower) in advance, directly from the catenary voltage or from the 1500V DC link, before the power reaches the auxiliary power supply. This preliminary conversion eliminates the need for subsequent voltage conversion stages, preventing energy losses that would occur in multi-stage conversion processes.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution prevents output reduction at low DC voltages, eliminates the need for high-voltage semiconductors in auxiliary power supplies, and reduces apparatus size and cost, while improving system efficiency by enabling efficient power conversion across various voltage systems.
Implementation Method 1
a power converter to convert electric power, obtained from an overhead line, into a three phase alternating current in order to control the speed of a traction motor
Implementation Method 2
an auxiliary power supply capable of supplying electric power in a stable manner to on-board lighting and air conditioning
Implementation Method 3
allowing one arm of the converter to operate as a step-up chopper so as to obtain a voltage equal to or higher than a catenary voltage
Implementation Method 4
stepping down or stepping up the voltage with a voltage converter to 750 V
Data Source
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AI summary
In a rail vehicle passing along catenary voltage sections including an AC and a plurality of DCs, an arrangement is provided to solve a problem that the output of the vehicle is reduced under the lower voltage of the DC voltages and to achieve a reduction in voltage for an auxiliary power supply. The present invention includes a current collector capable of collecting two DCs under different voltages, an inverter configured to control an AC motor, an inverter configured to perform constant voltage constant frequency control under a voltage lower than that of the inverter configured to control the AC motor, a step-up/down chopper capable of stepping-up/down voltage; and circuit switching means capable of switching a current path selectively. Under a higher voltage, power stepped-down by the step-up/down chopper is supplied to the inverter configured to perform the constant voltage constant frequency control. Under a lower voltage, power stepped-up by the step-up/down chopper is supplied to the inverter configured to drive the AC motor.