Dual-Voltage DC Bus Control for Variable Hybrid Vehicle Loads
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Solution Overview
Problem
Hybrid off-road vehicles with fixed DC bus voltage face limitations in providing alternating current energy to variable electrical loads, as the fixed voltage cannot dynamically adjust to changing load demands.
Innovation Solution
A dual voltage direct current bus system with a first and second inverter, coupled to a primary and secondary electric machine, respectively, allowing operation at a lower or higher voltage level based on load requirements, controlled by a vehicle controller or electronic data processor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a fixed DC bus voltage is used, then system simplicity is maintained, but the ability to meet variable load demands is limited
Solution Approach 1:
The DC bus voltage is made dynamic by enabling transitions between two voltage levels (first voltage level and second voltage level). The system can switch from a fixed voltage to a variable voltage system that adapts to load conditions, resolving the contradiction between simplicity and adaptability.
Solution Approach 2:
The system changes the voltage parameter of the DC bus dynamically. By switching between two discrete voltage levels based on load conditions, the system achieves adaptability to variable loads while maintaining a relatively simple dual-level architecture rather than a continuously variable complex system.
2Power
If a fixed DC bus voltage is used, then system complexity is reduced, but power capacity for high-demand tasks is insufficient
Solution Approach 1:
The inverter system dynamically adjusts its operating voltage level based on power demand. During high-demand tasks, the system switches to the second (higher) voltage level to provide sufficient power capacity, while operating at the first (lower) voltage level during normal conditions to maintain simplicity.
Solution Approach 2:
The system changes the voltage parameter of the DC bus to match power demands. By implementing a dual-voltage architecture with switchable levels, the system achieves high power capacity when needed without the continuous complexity of a fully variable voltage system.
3Use of energy by moving object
If DC bus voltage operates at higher level continuously, then power capacity is sufficient, but energy efficiency is reduced
Solution Approach 1:
The system dynamically selects the appropriate voltage level based on real-time load conditions. During normal operation with lower power demands, the system operates at the first (lower) voltage level to maximize energy efficiency. When high power capacity is required, it switches to the second (higher) voltage level, thus achieving both efficiency and sufficient power capacity at different times.
Solution Approach 2:
The voltage parameter is changed dynamically rather than maintained at a fixed high level. This allows the system to optimize energy efficiency during normal operation by operating at lower voltage, while still providing the capability to switch to higher voltage when power capacity is needed, resolving the contradiction between continuous high power availability and energy efficiency.
Data Source
Figure 1A
Figure 1B
Figure 2
AI summary
During a normal DC bus mode, the first DC node and the second DC node are configured to operate a lower voltage level on the primary direct current bus (38). In contrast, during a boost DC mode, the first DC node and the second DC node configured to operate a higher voltage level, which is higher than the lower voltage level, on the primary direct current bus (38).