Electric Motor Controller Carrier Frequency Switching

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Solution Overview

Problem

Electric motor controllers face misestimation of disturbance components when switching carrier frequencies, leading to deteriorated current response characteristics.

Innovation Solution

A control unit with a current control part that calculates voltage command values through feedback control and includes a disturbance estimation part to update control constants dependent on the control operation cycle after carrier frequency switching, ensuring accurate disturbance estimation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the carrier frequency is switched to prevent heat and switching means damage, then the reliability of the switching means is improved, but the disturbance component may be misestimated leading to deterioration in current response characteristics

Engineering Contradiction:

Improvereliability of switching meansVSAvoiddisturbance component estimation accuracy

Core Design Contradiction:

ReliabilityVSMeasurement precision

Solution Approach 1:

The control constant update is performed in advance in the control operation immediately after carrier frequency switching, so that when disturbance estimation is needed, the control constant has already been updated to reflect the new carrier frequency. This preliminary update action prevents misestimation while maintaining the reliability benefits of carrier frequency switching.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system uses feedback control where the disturbance component is continuously estimated and fed back to adjust the voltage command value. By updating the control constant based on the new carrier frequency and using this updated constant in the feedback loop, the system maintains accurate disturbance estimation despite carrier frequency changes.

Inventive Principle:

Principle #23Feedback

2Adaptability or versatility

If the control operation cycle is switched simultaneously with carrier frequency switching, then the control adapts to the new frequency, but the control constant becomes inappropriate causing disturbance misestimation

Engineering Contradiction:

Improvecontrol adaptation to carrier frequencyVSAvoiddisturbance component estimation accuracy

Core Design Contradiction:

Adaptability or versatilityVSMeasurement precision

Solution Approach 1:

The control constant is updated in the control operation immediately after carrier frequency switching, preparing the system in advance so that subsequent disturbance estimations use the correct control constant corresponding to the new carrier frequency, preventing misestimation while maintaining adaptability.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system cushions against potential misestimation by proactively updating the control constant before disturbance estimation becomes critical. This beforehand preparation ensures that even if the control operation cycle changes simultaneously with carrier frequency, the disturbance estimation remains accurate.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

Data Source

PatentEP2577863B1Electric motor controller and electric motor control system

Publication Date: 2019.08.21 NISSAN MOTOR CO LTD

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AI summary

A controller 40 performs a control operation in a cycle based on a carrier frequency fc of a carrier, specifically, at timings corresponding to the peaks and troughs of the carrier signal. Moreover, in the case where the carrier frequency fc is switched, a disturbance estimation part forming the controller 40 updates control constants that are used for disturbance estimation and are dependent on the control operation cycle, in a control operation performed one cycle after a control operation immediately after the switching of the carrier frequency fc.