Homopolar Polyphase Supply for Auxiliary EV Power Networks
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Solution Overview
Problem
Current power supply systems for electric vehicles require complex conversion systems to supply auxiliary networks, often necessitating multiple converters and increasing complexity, especially when dealing with high voltage ratios between main and auxiliary networks.
Innovation Solution
A power supply system that generates polyphase voltage with a non-zero homopolar component, allowing for efficient supply of both electrical loads and auxiliary networks by connecting the auxiliary power terminals to a midpoint and reference point, thereby exploiting the homopolar component for simplified network supply.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a DC-DC converter is used to supply the auxiliary network from the main battery, then voltage conversion is achieved, but device complexity increases due to the need for independent conversion systems
Solution Approach 1:
The patent combines the auxiliary power supply function with the existing motor drive inverter by extracting the homopolar component from the polyphase voltage. This merging eliminates the need for separate DC-DC converters, as the inverter already generates the required voltage components during motor control operation. The homopolar component extraction circuit retrieves the zero-sequence voltage that would otherwise be wasted, providing auxiliary power without adding substantial complexity.
Solution Approach 2:
The motor drive inverter is made multi-functional by enabling it to simultaneously drive the motor and supply the auxiliary network. The same power electronic switches and DC link that serve the motor function are also utilized to generate the homopolar component for auxiliary power. This universal utilization of existing components avoids the need for dedicated auxiliary power conversion equipment.
2Reliability
If multiple converters are positioned between the voltage inverter and the electric motor, then balanced power drawing is achieved, but device complexity increases significantly
Solution Approach 1:
Instead of adding multiple converters to achieve balanced power distribution, the patent extracts the homopolar component directly from the polyphase voltage output of the inverter. This extraction approach isolates the zero-sequence voltage component that contains the auxiliary power, separating it from the three-phase motor supply without requiring additional conversion stages for each phase. The extraction circuit uses the inherent symmetry of the star-connected motor windings to obtain balanced power distribution naturally.
Solution Approach 2:
The patent transitions from a three-phase power distribution approach to utilizing the homopolar dimension (zero-sequence component) of the voltage system. By operating in this additional voltage dimension, the system can provide auxiliary power while maintaining balanced three-phase operation for the motor. This dimensional approach avoids the complexity of multiple phase-specific converters by using the inherent homopolar voltage present in the polyphase system.
3Reliability
If the auxiliary network is supplied via a separate DC-DC converter, then galvanic isolation is provided, but the system requires more components and increases complexity
Solution Approach 1:
The patent introduces a homopolar component extraction circuit as an intermediary between the inverter and the auxiliary network. This extraction circuit serves as a mediator that provides the necessary electrical isolation while transferring power. The circuit uses capacitive or inductive coupling to transfer the homopolar component voltage to the auxiliary network, providing galvanic isolation without requiring a full DC-DC converter stage. This intermediary approach maintains the isolation benefit while reducing overall system complexity.
Data Source
AI summary
A power supply system includes a main power supply system generating, from a main network, at least one polyphase voltage for supplying at least one load. Each load includes a winding for each phase. The windings are connected in star connection at a midpoint. An auxiliary power supply system of an auxiliary network includes a first power supply terminal and a second power supply terminal. The main power supply system is configured to generate the at least one polyphase voltage with at least one non-zero homopolar component. The auxiliary power supply system includes a module for connecting the first power supply terminal to the midpoint and the second power supply terminal to a reference point, for supplying the auxiliary network via at least one homopolar component coming from the midpoint.