Variable Voltage Converter Boost Control for Energy Loss Reduction
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Solution Overview
Problem
Existing variable voltage converter (VVC) control systems in electric vehicles experience energy transfer losses due to frequent changes in DC bus voltage, which lead to unnecessary energy shuffling between the battery and the inverter/electric-machine, compromising efficiency without adequately addressing stability and bandwidth requirements.
Innovation Solution
An optimized VVC boost strategy is implemented, where the rate of change of the DC bus voltage is adjusted based on the load current and capacitor current flow direction, minimizing energy transfer losses by selecting and adjusting the rate of change direction and magnitude, thereby reducing ripple in the inductor current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the DC bus voltage is frequently changed to respond to load variations, then the dynamic response is improved, but energy transfer losses increase due to unnecessary energy shuffling between battery and inverter
Solution Approach 1:
The patent applies dynamics by making the VVC boost strategy adaptive rather than fixed. The controller dynamically adjusts the boost activation and voltage ramp rate based on real-time operating conditions (load current, capacitor current direction, voltage error), allowing the system to optimize between fast response and energy efficiency for each specific condition.
Solution Approach 2:
The patent changes the parameter of voltage ramp rate from a fixed value to a variable parameter. The rate of change of output voltage is adjusted based on capacitor current direction and magnitude, enabling the system to use faster ramp rates when energy loss is less critical and slower ramp rates when minimizing energy shuffling is prioritized.
2Power
If the VVC boost is activated to increase DC bus voltage for improved load performance, then the load performance is improved, but energy shuffling between battery and inverter increases
Solution Approach 1:
The patent applies local quality by making different parts of the operating range have different boost strategies. Instead of a uniform boost approach, the controller applies boost selectively based on local conditions (capacitor current direction, load current magnitude, voltage error), optimizing energy efficiency for each specific operating point while maintaining load performance.
Solution Approach 2:
The patent uses partial action by not always applying full VVC boost when it would cause energy loss. The boost is applied partially (or not at all) when capacitor current indicates energy shuffling would occur, and fully when it provides net benefit, achieving load performance with minimized energy waste.
3Speed
If the rate of change of DC bus voltage is increased to improve dynamic response, then the response to load variations is faster, but ripple in inductor current increases
Solution Approach 1:
The patent applies dynamics by making the voltage ramp rate adaptive rather than fixed. The controller dynamically adjusts the rate of change based on real-time conditions, using higher rates when stability is less compromised and lower rates when ripple mitigation is prioritized, optimizing the trade-off between response speed and current stability.
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 strategy effectively minimizes energy transfer losses while maintaining system stability and bandwidth, improving the dynamic response to large load variations and reducing unnecessary energy shuffling, thus enhancing the overall efficiency of the electric vehicle powertrain.
Implementation Method 1
a variable voltage converter (VVC) configured to generate an output voltage for a load, and a controller configured to select a rate of change direction for the output voltage based on a current flow direction through a capacitor of the VVC
Data Source
AI summary
A controller is configured to select a rate of change direction of an output voltage of a variable voltage converter (VVC) based on a direction of current flow associated with a capacitor of the VVC, and to adjust a magnitude of the rate of change direction based on directions of current flow associated with the capacitor and an electric machine coupled to the VVC.