Variable Voltage Converter for Electrified Vehicles
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Solution Overview
Problem
Conventional DC-DC converters in electric drive systems for electrified vehicles face limitations in achieving high voltage gain while maintaining low power losses, with significant efficiency decrease and high power stress at higher duty cycles, and require large, lossy inductors to manage current ripple.
Innovation Solution
A variable voltage converter design that regulates PWM duty cycle to achieve high gain with low duty cycle values, using a configuration of inductors and capacitors that switch in parallel during the ON phase and in series during the OFF phase, allowing for reduced power losses and smaller inductor sizes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the duty cycle is increased to achieve higher voltage gain, then the voltage gain increases, but the power loss increases and efficiency decreases
Solution Approach 1:
The patent segments the single inductor into two inductors (L1 and L2) that can operate in parallel or series configurations. This segmentation allows the system to achieve high voltage gain through series connection without requiring a high duty cycle, thereby reducing power loss while maintaining the ability to provide high voltage gain when needed.
Solution Approach 2:
The patent implements dynamic reconfiguration of the inductor circuit, switching between parallel and series configurations based on operating conditions. The controller dynamically adjusts the connection topology to optimize performance, achieving high voltage gain with low duty cycle by using series configuration, and reducing power loss through parallel configuration during normal operation.
2Stability of the object's composition
If large inductors are used to limit current ripple, then current ripple is reduced, but the inductors become bulky, heavy, and lossy
Solution Approach 1:
The patent divides a single large inductor into two smaller inductors (L1 and L2). When connected in parallel, these smaller inductors provide equivalent or better current ripple filtering compared to a single large inductor, but with reduced weight and volume. The segmentation allows each inductor to be optimized for smaller size while maintaining overall system performance.
Solution Approach 2:
The patent combines two smaller inductors that can operate in parallel to achieve the current ripple reduction effect of a single large inductor. When parallel-connected, their combined inductance provides effective current ripple filtering, and they can be switched to series connection for high voltage gain, eliminating the need for a single bulky inductor.
3Force
If the duty cycle is increased to achieve higher voltage gain, then the voltage gain increases, but the voltage stress on switching devices increases
Solution Approach 1:
The patent segments the voltage gain function across two inductors and switches. By using two switching devices (S1 and S2) instead of one, the voltage stress on each individual switching device is reduced. The series configuration of L1 and L2 allows achieving high voltage gain while distributing the voltage stress across multiple components.
Solution Approach 2:
The patent uses dynamic switching between parallel and series configurations to manage voltage stress. During normal operation with parallel configuration, voltage stress is distributed across the parallel inductors. When high voltage gain is needed, the series configuration is activated, but this can be done with a lower duty cycle, thereby reducing the overall voltage stress on the switching devices compared to using a single inductor with high duty cycle.
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 solution enables higher voltage gain with reduced power losses and smaller, lighter inductors, improving efficiency and reducing costs while maintaining low current ripple, allowing for a wider output voltage range and lower component stress.
Implementation Method 1
A first inductor is coupled between a positive power storage node and a first switching node. A second inductor is coupled between a positive terminal of the first capacitor and a second switching node.
Implementation Method 2
A first capacitor having a negative terminal is coupled to the negative power storage node. A second capacitor has a positive terminal coupled to the first switching node.
Data Source
AI summary
A variable voltage converter transfers charge between a battery and a DC link. A first inductor couples a positive battery node and a first node. A first transistor selectably couples the first node to a negative battery node. A first capacitor has a negative terminal coupled to the negative battery node. A second inductor couples a positive terminal of the first capacitor to a second node. A second capacitor has a positive terminal coupled to the first node. A second transistor selectably couples the second node to a negative terminal of the second capacitor. When the transistors are non-conducting, the second inductor charges the DC link and the first inductor charges the first and second capacitors. When the transistors are conducting, the inductors are energized in parallel by the battery and the first and second capacitors. High voltage gain is obtained at relatively low values for the PWM duty cycle.