DC Railway Transformer Tap Control for Load Voltage Stability
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Solution Overview
Problem
Conventional DC railway power supply systems face voltage drops under load due to internal transformer resistance, necessitating expensive thyristor or IGBT rectifiers for voltage regulation, which are not economically viable for widespread use.
Innovation Solution
A DC railway transformation system utilizing an electronic tap changer that measures output voltage and current to regulate the switchable transformer's primary winding wires, controlling the tap changer to maintain optimal voltage levels without the need for thyristor or IGBT rectifiers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a thyristor rectifier or IGBT double-way rectifier is used to suppress voltage drop and maintain constant voltage, then voltage regulation performance is improved, but system cost increases significantly
Solution Approach 1:
The patent changes the operating parameters of the transformer by dynamically adjusting the tap position on the primary winding based on load conditions. The controller monitors output voltage and selectively connects different taps (e.g., 0.8, 0.9, 1.0, 1.1 per unit) to compensate for voltage drops under load without requiring expensive active rectifier devices. This parameter adjustment approach achieves voltage regulation through passive transformer configuration changes rather than active electronic control.
2Reliability
If the voltage for no load is set to 110% of rated voltage to suppress voltage drop under load, then voltage stability is improved, but the system becomes less efficient at no load conditions
Solution Approach 1:
The patent implements dynamic voltage adjustment by enabling the tap changer to respond to real-time load conditions. Instead of maintaining a fixed 110% no-load voltage, the system dynamically selects appropriate tap positions based on actual demand. The controller continuously monitors output voltage and adjusts the transformer tap position accordingly, allowing the system to operate at optimal voltage levels for each loading condition rather than maintaining a constant elevated voltage.
Solution Approach 2:
The system incorporates feedback control through voltage monitoring and automatic tap position adjustment. The controller receives voltage information from monitoring devices and automatically selects appropriate taps on the primary winding to maintain desired voltage levels. This closed-loop feedback mechanism eliminates the need for fixed over-voltage settings and enables adaptive voltage regulation that responds to actual system conditions.
3Object-affected harmful factors
If a 24-pulse rectifying circuit with two rectifier transformers is used to reduce current distortion, then power quality is improved, but device complexity and cost increase
Solution Approach 1:
The patent extracts and eliminates the complex multi-pulse rectifier configuration from the system. Instead of using 24-pulse or 12-pulse rectifying circuits with multiple transformers and phase-shifting windings, the invention uses a simple single-phase or three-phase diode rectifier combined with transformer tap changing. This extraction of the unnecessary complexity achieves voltage regulation through a much simpler configuration while maintaining acceptable power quality.
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 solution minimizes voltage drops under full load conditions while reducing costs by regulating primary winding wires, allowing for efficient voltage management without expensive rectifier technologies, thus enhancing economic viability and operational efficiency.
Implementation Method 1
a rectifier which rectifies the output voltage of the 3-phase switchable transformer
Implementation Method 2
a tap changer which is selectively in contact with the plurality of taps connected to each primary winding wire of the 3-phase switchable transformer and regulates an output voltage of the switchable transformer
Data Source
Figure 1
Figure 2(a)~2(c)
Figure 3(a)~3(c)
AI summary
A DC railway transformation system according to an embodiment of the present disclosure includes a 3-phase switchable transformer of which a plurality of taps is connected to each primary winding wire; a tap changer which is selectively in contact with the plurality of taps connected to each primary winding wire of the 3-phase switchable transformer and regulates an output voltage of the switchable transformer; a rectifier which rectifies the output voltage of the 3-phase switchable transformer; a meter which measures an output voltage or output current of the rectifier; and a controller which outputs a control signal to control an operation of the tap changer based on the output voltage or output current measured by the meter.