Variable Voltage Controller Using Low-Frequency Switches
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Solution Overview
Problem
Variable voltage controllers in electric machines and inverters face challenges with high switching losses and bulkiness due to high-speed switches, which are not necessary for all voltage adjustment needs, and require additional cooling or bulk inverter systems.
Innovation Solution
A controller operates a set of switches to arrange battery partitions in series or parallel configurations to adjust the inverter bus voltage based on the speed of an electric machine, using low-frequency switches like solenoids or relays to optimize voltage output without the need for high-frequency switches, allowing for a variable output voltage that matches the voltage requirement of the inverter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If high-speed switches (IGBTs) are used in boost converter structure, then voltage adjustment capability is improved, but switching losses increase substantially
Solution Approach 1:
The patent changes the switching frequency parameter from high-speed (IGBT range) to low-speed operation. The controller uses low-frequency switching to activate battery partitions sequentially, adjusting voltage without the substantial switching losses associated with high-speed IGBTs. This parameter change resolves the contradiction by operating in a frequency range where losses are minimal while still achieving voltage adjustment.
Solution Approach 2:
The patent extracts the high-speed switching function from the system by using low-frequency switches instead. The boost converter structure traditionally requires high-speed switches for rapid voltage adjustment, but this patent removes that requirement by using slower switches that activate battery partitions in sequence, eliminating the need for high-speed switching while maintaining voltage adjustment capability.
2Measurement precision
If high-speed switches are used, then voltage control precision is improved, but additional cooling requirements and system bulk increase
Solution Approach 1:
The patent changes the operational parameter from high-speed switching to low-frequency switching, which fundamentally alters the thermal and spatial characteristics of the system. Low-frequency operation generates less heat requiring minimal cooling infrastructure and reduces the physical space needed for heat dissipation components, thereby reducing overall system bulk while maintaining adequate voltage control precision through sequential battery partition activation.
3Adaptability or versatility
If boost converter structure with high-speed switches is used, then voltage adjustment range is improved, but device complexity increases
Solution Approach 1:
The patent segments the battery system into multiple partitions that can be activated independently through low-frequency switches. Instead of using a complex boost converter with high-speed switches for continuous voltage adjustment, the system divides the battery into discrete segments (partitions) and activates them in sequence, achieving voltage adjustment through a simpler segmented approach that reduces device complexity.
Data Source
AI summary
A vehicle includes an inverter connected to an energy store having a variable output voltage and including a first pair of battery partitions. The vehicle includes a controller configured to operate a first set of switches to arrange electrical connections between the first pair such that the variable output voltage is greater than battery voltage of a one of the battery partitions. The operation of switches is responsive to a parameter indicative of speed of an electric machine electrically coupled to the inverter exceeding a first predetermined threshold.