Power Conversion System Voltage Stabilization
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Solution Overview
Problem
Existing power conversion systems for electric vehicles face instability in converting alternating current power from overhead wires to direct current power, leading to variations in voltage that affect the operation of loads and battery safety.
Innovation Solution
A power conversion system comprising an AC to DC conversion circuit, a step-down chopper circuit, and a load power control unit that stabilizes the DC link voltage by controlling the AC to DC conversion and step-down chopper circuits to maintain a reference voltage, ensuring stable power supply to loads and preventing overvoltage to the battery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the AC power supplied from overhead wires varies, then the converted DC power varies, but this causes instability in load operation and battery safety
Solution Approach 1:
The patent applies dynamics by making the switching elements adjustable in their switching timing based on the detected AC voltage level. The control unit dynamically changes the switching duty ratio according to input voltage variations, allowing the system to adapt to different input conditions while maintaining stable DC output. This resolves the contradiction by enabling the system to be both adaptable to input variations and reliable in output stability.
Solution Approach 2:
The patent changes the switching parameters (duty ratio, switching timing) of the switching elements based on the detected AC voltage level. By adjusting these parameters dynamically, the system can handle a wide range of input voltages while maintaining consistent DC output, thus resolving the contradiction between adaptability and stability.
2Strength
If switching elements are selected based on maximum AC voltage, then they can handle peak voltage, but they are oversized for normal operation
Solution Approach 1:
The patent makes the switching elements operate dynamically by adjusting their duty ratio based on the actual AC voltage level. During normal operation at lower voltage levels, the duty ratio is reduced, allowing the use of smaller, more efficient switching elements. When peak voltage occurs, the duty ratio is adjusted to handle the higher voltage. This resolves the contradiction by enabling voltage handling capability while improving utilization efficiency.
3Reliability
If the voltage of converted DC power is stabilized, then load operation becomes consistent, but this requires complex control mechanisms
Solution Approach 1:
The patent implements feedback control by detecting the AC voltage level and using this information to adjust the switching timing and duty ratio of the switching elements. This feedback mechanism stabilizes the DC link voltage while keeping the control system relatively simple, as it uses the already-detected voltage information for control adjustments rather than requiring separate complex stabilization circuits.
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 system provides stable power to both AC and DC loads, allowing them to operate consistently and protecting the battery from overvoltage, while enabling the use of standard switching elements across a range of input voltages without the need for high-capacity capacitors.
Implementation Method 1
The power conversion device converts alternating current power supplied from overhead wires into direct current power
Implementation Method 2
a step-down chopper circuit, and a load power control unit that stabilizes the DC link voltage by controlling the AC to DC conversion and step-down chopper circuits
Data Source
AI summary
A power conversion system includes an AC to DC conversion circuit, a voltage detector, a step-down chopper circuit, a power conversion device for auxiliary power sources, and a control unit. The AC to DC conversion circuit converts AC power supplied from overhead wires via a transformer into DC power. The voltage detector detects a voltage of AC power supplied from the transformer. The step-down chopper circuit steps down the voltage of DC power produced through conversion by the AC to DC conversion circuit. The power conversion device for auxiliary power sources converts the DC power stepped down by the step-down chopper circuit into power for driving loads mounted in an electric vehicle and supplies it to the loads. The control unit controls the AC to DC conversion circuit and the step-down chopper circuit such that the voltage of AC power detected by the voltage detector approaches a reference voltage.