Motor Drive Power Sharing for Electric Vehicles
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Solution Overview
Problem
Existing power distribution systems for electric and hybrid-electric vehicles face inefficiencies due to the lack of cost-effective DC to DC converters and additional power conversion losses, which affect the longevity of batteries and the effectiveness of energy recapture during regeneration.
Innovation Solution
The system employs multiple motor drives to share power between multiple energy sources, such as batteries and ultra-capacitors, without the need for a DC to DC converter, using a controller to match torque demands and utilizing off-the-shelf, cost-optimized motor drives to directly connect DC buses at different voltages to an electric motor, with an optional encoder emulator to interface with AC mains.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a DC to DC converter is used to couple ultra-capacitor to battery, then voltage range adaptation is achieved, but system cost and complexity increase significantly
Solution Approach 1:
The motor drive inverter is designed to perform multiple functions: it serves as both the motor controller and the DC-DC converter for power sharing between battery and ultra-capacitor. The same inverter switches and control circuitry are used to manage power flow from either energy source to the motor, eliminating the need for separate DC-DC conversion hardware and reducing overall system complexity.
Solution Approach 2:
The patent combines the DC-DC conversion function with the motor drive inverter function into a single integrated system. The inverter that normally converts DC to AC for the motor is also used to convert DC from the ultra-capacitor to match the battery voltage level, merging two separate power electronic functions into one device.
2Adaptability or versatility
If a DC to DC converter is used for power sharing, then voltage matching is achieved, but additional power conversion losses occur
Solution Approach 1:
The patent extracts the DC-DC conversion function from the power sharing system and eliminates it entirely. Instead of adding a separate conversion stage, the system uses the motor drive inverter to directly manage power flow from either the battery or ultra-capacitor to the motor, removing the intermediate conversion step that causes energy losses.
Solution Approach 2:
The motor drive inverter acts as an intermediary device that can accept DC power from either the battery or ultra-capacitor and deliver it to the motor. The inverter's switching circuitry enables direct power transfer without requiring a separate DC-DC conversion stage, thereby eliminating the associated energy losses while still achieving voltage matching through the inverter's control capabilities.
3Device complexity
If battery only system is used, then system simplicity is maintained, but battery longevity is drastically affected by transient loads
Solution Approach 1:
The patent segments the energy storage function into two separate systems: the battery provides steady-state energy storage while the ultra-capacitor handles transient power demands. This segmentation allows each system to operate in its optimal performance range, with the ultra-capacitor absorbing high-current transient loads that would otherwise stress and reduce battery longevity.
Solution Approach 2:
The patent applies local quality by assigning different functional characteristics to different energy storage devices based on their inherent properties. The ultra-capacitor is positioned to handle high-power transient events where it excels, while the battery maintains its role for sustained energy delivery where it is more efficient, optimizing overall system performance and battery life.
4Device complexity
If battery only system is used, then system simplicity is maintained, but energy recapture during regeneration becomes inefficient
Solution Approach 1:
The patent segments the energy recapture function by directing regenerative braking energy primarily to the ultra-capacitor during deceleration events. The ultra-capacitor's ability to rapidly accept high-current charging from the motor during regeneration is utilized, while the battery handles steady-state charging, optimizing overall energy recapture efficiency.
Solution Approach 2:
The patent applies local quality by matching the energy recapture strategy to the characteristics of each energy storage device. During regenerative braking, the system prioritizes charging the ultra-capacitor which can rapidly accept energy, thereby maximizing the amount of kinetic energy that can be recaptured and stored for future use.
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 approach increases efficiency by eliminating a second power conversion process, reduces the need for expensive DC to DC converters, and allows for effective power sharing between energy sources, enhancing the vehicle's range and performance.
Implementation Method 1
A first motor drive inverter delivers a first AC current to an electric motor... A second motor drive inverter delivers a second AC current to the electric motor
Implementation Method 2
An example of such a secondary energy storage system is an ultra-capacitor. Ultra-capacitors are a new type of capacitor, which has significantly greater energy storage capability over a traditional capacitor.
Data Source
AI summary
A power sharing system for electric motors and drives shares power between multiple power sources. Multiple motor drives share power between multiple energy sources, without the need for a DC to DC converter. A motor drive adapts the DC voltage range of the power source to either AC voltage or a different DC voltage range to operate one or more electric motors. Either a capacitor bank or a battery is directly connected to a motor drive's DC input. Two separate DC inputs exist, each able to operate at its own voltage and both feeding the same motor through separate motor drives, to allow batteries to be operated at one voltage level while capacitors are operated at another. The motor drives inherently cause power to flow between the motor and either power source, regardless of the relative voltages of the two sources, provided that each source is at a sufficient voltage to power the motor independently.