Step-Down DC-DC Converter for Public Transport Battery Systems
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Solution Overview
Problem
Existing public transport vehicles require a step-up converter to discharge batteries to the DC bus, limiting energy transfer capacity and battery lifespan due to nominal voltage settings that result in voltages below 33% of the maximum voltage.
Innovation Solution
A public transport vehicle with a controllable step-down DC-DC converter connected to the battery and DC bus, operating at a voltage lower than 33% of the maximum battery voltage, allowing only step-down converters to transfer energy, thereby increasing energy transfer capacity and prolonging battery life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a step-up converter is used to discharge the battery to the DC bus, then the battery can be discharged at nominal voltage settings, but the energy transfer capacity is limited
Solution Approach 1:
Instead of using a step-up converter to increase battery voltage to match DC bus voltage, the invention inverts the approach by using a step-down converter to reduce battery voltage to DC bus voltage level. This allows the battery to operate at higher voltage throughout its discharge cycle, significantly increasing energy transfer capacity while simplifying the converter requirements.
Solution Approach 2:
The invention changes the voltage parameter relationship between battery and DC bus. By setting the DC bus nominal voltage to be lower than one-third of the battery's maximum voltage, the system enables the battery to discharge across a wider voltage range using only step-down conversion, thereby increasing overall energy transfer capacity.
2Duration of action of moving object
If the nominal voltage is set equal to 70-80% of maximum battery voltage, then the battery can operate at nominal voltage, but the battery lifespan is reduced due to early voltage cutoff
Solution Approach 1:
The invention changes the DC bus nominal voltage parameter to be lower than one-third of the battery maximum voltage. This parameter change allows the battery to discharge to much lower voltage levels (close to minimum voltage) before cutoff, extending battery lifespan and increasing total energy utilization without requiring voltage boosting.
3Power
If the DC bus nominal voltage is kept above one-third of maximum battery voltage, then the system maintains higher voltage operation, but the battery cannot be fully discharged
Solution Approach 1:
The invention inverts the conventional voltage relationship by setting DC bus voltage lower than battery voltage. This enables the battery to discharge to very low voltage levels (below one-third of maximum voltage) while maintaining efficient energy transfer through step-down conversion, thereby extracting nearly all available energy from the battery.
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 configuration enables higher energy transfer rates and extends battery lifespan by utilizing step-down converters for energy delivery, ensuring efficient energy use even at low voltages, and includes features like a removable battery pack, voltage regulation, and safety mechanisms to protect components.
Implementation Method 1
Battery as used here refers to an accumulator which delivers continuous current by converting chemical energy into electrical energy.
Data Source
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AI summary
This public transport vehicle includes: - a DC bus (8) devised to function under a nominal direct voltage VDCnom, and - a battery (30) connected to the DC bus The voltage VDCnom is systematically lower than 33% of a voltage VBmax at the terminals of the battery when it is fully charged The vehicle also includes a step-down DC-DC converter (40) connected on one side to the terminals of the battery (30) and on the other side to the DC bus.