Electric Machine Terminal Voltage Control for Freewheeling Transition
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Solution Overview
Problem
Existing methods for transitioning electrical machines from controlled operation to freewheeling mode often result in abrupt voltage changes, leading to harmful overvoltages and potential damage, particularly in sensitive components like traction batteries in vehicles.
Innovation Solution
A method and device that gradually adjust the voltage at the electrical machine's terminals to match freewheeling conditions by using a speed sensor to determine the appropriate freewheeling voltage, ensuring a smooth transition without voltage jumps, employing semiconductor switches and a controller to manage the inverter, and regulating voltage components independently of phase currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the electrical machine is abruptly switched from controlled operation to freewheeling mode, then the transition is fast and simple, but harmful voltage jumps and overvoltages occur that can damage the system
Solution Approach 1:
The patent applies preliminary action by adjusting the voltage at the machine terminals to match the expected freewheeling voltage before actually switching to freewheeling mode. This preparatory voltage adjustment ensures that when the transition occurs, there is no voltage difference to cause harmful jumps or overvoltages, thus preventing damage to the system while maintaining a relatively fast transition.
2Object-affected harmful factors
If the voltage is adjusted to match freewheeling conditions before switching, then voltage jumps are prevented, but the transition process becomes more complex and time-consuming
Solution Approach 1:
The patent applies parameter changes by adjusting the voltage parameter at the machine terminals to match the expected freewheeling voltage before switching modes. This controlled parameter adjustment prevents harmful voltage jumps while maintaining manageable system complexity, as the voltage adjustment follows a predetermined profile based on the freewheeling conditions.
3Loss of time
If abrupt switching is performed, then the transition is quick, but the energy supply (traction battery) experiences higher load and reduced service life
Solution Approach 1:
The patent applies preliminary action by pre-adjusting the voltage to match freewheeling conditions before switching modes. This prevents voltage jumps that would otherwise cause sudden high current draws from the traction battery, thereby reducing the load on the energy supply and extending battery service life while keeping the transition time relatively short.
Solution Approach 2:
The patent applies beforehand cushioning by preparing the voltage conditions in advance to cushion against the harmful effects of abrupt switching. By matching the voltage to expected freewheeling values before transition, the system cushions against voltage jumps and their damaging effects on the battery, protecting the energy supply without significantly delaying the transition.
Data Source
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AI summary
The present invention provides a device and a method for changing over an electric machine from the regular operating mode into the open-circuit mode. In order to avoid excessive increases in voltage and associated adverse effects on the electric machine and the other components, in particular batteries, a further control phase is introduced between the end of the regular operating mode and the freewheeling mode, during which further control phase the voltage at the terminals of the electric machine is continuously adjusted from the voltage previously set in the regular operating mode to the expected open-circuit voltage of the electric machine.