Power Converter Pre-Compensation for Dead-Time Waveform Distortion

Solution Overview

Problem

The insertion of dead-time intervals in power converters for electric drive systems of electrified vehicles introduces distortion in the output waveform and control delays, which can lead to shoot-through and damage to switching devices.

Innovation Solution

Pre-compensating gate drive signals by shifting turn-on and turn-off times of upper and lower switching devices based on current direction, using a predetermined offset to avoid distortion and ensure simultaneous non-conduction without dead-time insertion.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If dead-time intervals are inserted to prevent shoot-through, then switching device safety is improved, but output waveform distortion and control delays occur

Engineering Contradiction:

Improveswitching device safetyVSAvoidoutput waveform accuracy

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The patent applies preliminary action by pre-compensating the PWM gate drive signals before dead-time insertion. The turn-on and turn-off times of switching devices are shifted by a predetermined offset in advance, so that when dead-time is inserted, the output waveform distortion is eliminated while maintaining switching device safety.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent changes the timing parameters of the gate drive signals by applying a predetermined offset to the turn-on and turn-off times. This parameter adjustment compensates for the dead-time effect, allowing the system to maintain waveform accuracy while inserting necessary dead-time intervals for safety.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If dead-time intervals are inserted to prevent shoot-through, then switching device safety is improved, but control delays are introduced

Engineering Contradiction:

Improveswitching device safetyVSAvoidcontrol delay

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The patent applies preliminary action by pre-compensating the PWM gate drive signals before dead-time insertion. The turn-on and turn-off times of switching devices are shifted by a predetermined offset in advance, so that when dead-time is inserted, the output waveform distortion is eliminated while maintaining switching device safety.

Inventive Principle:

Principle #10Preliminary action

3Manufacturing precision

If pre-compensation with predetermined offset is applied, then output waveform distortion is eliminated, but gate signal timing complexity increases

Engineering Contradiction:

Improveoutput waveform accuracyVSAvoidgate signal timing control

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent changes the timing parameters of the gate drive signals by applying a predetermined offset to the turn-on and turn-off times. This parameter adjustment compensates for the dead-time effect, allowing the system to maintain waveform accuracy while inserting necessary dead-time intervals for safety.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS9553540B2Power converter with pre-compensation for dead-time insertion

Publication Date: 2017.01.24 FORD GLOBAL TECH LLC

AI summary

A power converter has a phase leg with upper and lower switching devices coupled across a DC link. A junction between the devices is coupled to a load. A current sensor detects direction of current flow from the junction to the load. A gate driver activates the devices according to upper and lower gate signals in response to pulse-width modulation (PWM) to generate nominal gate signals from a variable duty cycle. When the positive current direction is detected then the upper gate signal has turn-on and turn-off times shifted by a predetermined offset with respect to the nominal signals, and dead-times are added to the lower gate signals. When the negative direction is detected then the lower gate signal has turn-on and turn-off times shifted by the predetermined offset with respect to the nominal signals, and dead-times are added to the upper gate signals.