Rail Vehicle Multisystem Transformer Midpoint Connection
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Solution Overview
Problem
Existing electric multisystems for rail vehicles face challenges in efficiently switching between AC and DC power sources, leading to varying DC link voltages that affect the transferable power and harmonic content, limiting the optimization of system components and increasing costs.
Innovation Solution
The system divides the transformer's secondary winding into halves and connects the DC voltage to the midpoint, allowing the line converter to act as a DC to DC-chopper, utilizing the inductance of each half to adjust voltage levels, enabling higher transferable power and reduced harmonics, and optimizing the system for a narrower DC link voltage range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If DC voltage is connected to one end of the secondary winding, then the system can operate with DC power source, but the transferable power is limited and harmonic content increases
Solution Approach 1:
The secondary winding is divided into two equal halves with a midpoint connection. This segmentation allows the DC voltage to be connected to the midpoint rather than one end, enabling both phase-legs of the line converter to be utilized simultaneously. This doubles the transferable power compared to connecting DC to one end, and the symmetric configuration reduces harmonic content by balancing the current distribution.
2Adaptability or versatility
If DC link voltage is allowed to vary over wide range, then the system can adapt to different contact line voltages, but component design and dimensioning cannot be optimized
Solution Approach 1:
The line converter is controlled dynamically to regulate the DC link voltage within a narrow range despite variations in contact line voltage. The control system adjusts the switching of current valves to maintain optimal voltage levels, allowing the system to adapt to different contact line voltages (500-1950 V DC) while keeping the DC link voltage stable for optimized component design.
3Adaptability or versatility
If connector means switches between AC and DC connection points, then the system can operate on different rail sections, but the DC link voltage varies affecting system performance
Solution Approach 1:
The midpoint connection of the secondary winding acts as an intermediary for DC voltage input. This configuration, combined with the line converter control, serves as a mediator that stabilizes the DC link voltage regardless of whether the system is connected to AC or DC contact lines, ensuring reliable operation across different rail sections.
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
This design doubles the transferable power and halves the harmonic content, allowing the system to regulate DC link voltage within a narrower range, reducing component costs and enabling operation across multiple voltage ranges, such as 500-1950 V DC, while maintaining efficiency and reducing harmonic pollution.
Implementation Method 1
The vehicle has a transformer 3 for transforming the voltage from the contact line 2 to a suitable level. The transformer has here a primary winding 4 and two secondary windings 5, 6
Implementation Method 2
the line converter may be controlled to, together with the inductance of each half of the secondary winding used as a step-up chopper inductor, act as a DC to DC-chopper for adjusting the level of the DC voltage delivered to the DC intermediate link
Data Source
AI summary
An electric multisystem on board a rail vehicle comprises a first connector means (22, 23) configured to connect either a first connection point (a) of the electric system to an AC-contact line or a second connection point (b) of the electric system to a DC-contact line. A transformer (3) has a primary winding (4) to which the first connection point (a) is connected. A line converter (13, 7) is connected to the secondary winding of the transformer and has the output connected to a DC-intermediate link (14, 18). The secondary winding of the transformer is divided into two halves (51, 52) connected in series and a second connector means (70, 71) connects the second connection point (b) to the secondary winding of the transformer by connecting the DC voltage to a midpoint (55) between the two halves (51, 52). A control unit (19) controls the line converter (13, 7) to together with the inductor of each half of the secondary winding used as a step-up chopper inductor acts as a DC to DC-chopper for adjusting the level of the DC voltage delivered to the DC intermediate link (14, 18).