Dynamic Slew Rate Control for Inverter Voltage Pulses
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Solution Overview
Problem
Modern electric vehicle powertrains face challenges in controlling the slew rate of voltage pulses generated by voltage source inverters, which can lead to harmful electromagnetic interference and damage to motor coils due to high slew rates and voltages.
Innovation Solution
A voltage pulse generator (VPG) with a controller and negative feedback circuit, known as an interruptor, dynamically controls the rise and fall times of voltage pulses by comparing output voltage to a reference voltage, turning ON and OFF the pulse generator to maintain a desired average slew rate, thereby limiting the slew rate and reducing electromagnetic interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If fast switching semiconductor power switches are used to generate voltage pulses, then power delivery efficiency is improved, but electromagnetic interference and coil damage occur due to high slew rates
Solution Approach 1:
A current transformer is introduced as an intermediary device between the voltage pulse generator and the motor load. The transformer couples the high-voltage pulse source to the motor through magnetic coupling, which naturally limits the rate of change of current (slew rate) while maintaining efficient power transfer. This intermediary device transforms the harmful high-slew-rate voltage pulses into controlled current waveforms.
Solution Approach 2:
The invention transforms the control parameter from voltage-based switching to current-based control. By monitoring the secondary current of the current transformer and using it to control the switching of power transistors, the system naturally limits the slew rate of current changes. This parameter transformation from voltage to current control fundamentally resolves the electromagnetic interference problem while maintaining power delivery efficiency.
2Power
If high voltage pulses with high slew rates are generated, then power delivery capability is improved, but motor coil damage occurs
Solution Approach 1:
A feedback control system is implemented where the secondary current of the current transformer is continuously monitored and fed back to control the switching of power transistors. This feedback mechanism ensures that the current through the motor coils never exceeds safe limits, protecting the coils from damage while maintaining high power delivery capability. The feedback loop dynamically adjusts the switching timing to prevent coil overcurrent conditions.
Solution Approach 2:
The current transformer and feedback control system provide beforehand cushioning by predicting and preventing harmful current conditions before they occur. The transformer's magnetic coupling inherently limits rate of change of current, and the feedback system anticipates potential overcurrent conditions by monitoring current trends, adjusting switching timing in advance to prevent coil damage before it can occur.
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 VPG effectively moderates the average slew rate of voltage pulses, reducing electromagnetic interference and protecting motor coils, while maintaining efficient power delivery to electric vehicle motors.
Implementation Method 1
the interruptor compares voltage at the VPG output to the rise time and/or fall time reference voltage respectively
Implementation Method 2
pulse circuitry operable to be turned ON and OFF respectively to provide and to terminate voltage at an output of the pulse circuitry to provide a pulse of voltage
Data Source
AI summary
A voltage pulse generator comprising: circuitry controllable to generate a voltage pulse at an output of the circuitry; and an interruptor that monitors voltage at the output during a transition edge of the voltage pulse and interrupts a voltage change associated with the transition edge if the monitored voltage differs from a predetermined reference voltage by a predetermined amount.