AC Rotary Machine Control Device Offset Voltage Harmonic Superposition

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Solution Overview

Problem

At high speeds, AC rotary machines require fast calculation processing to accurately apply high-order harmonic voltages, which is costly due to the need for expensive computing units with fast processing speeds, as slower units cannot handle the high calculation load effectively.

Innovation Solution

The AC rotary machine control device uses simple calculation processing to add or subtract an offset value from the middle voltage command based on its comparison to the vibration center voltage, allowing for the superimposition of 5th and 7th order harmonic voltages, reducing the calculation load and enabling the use of cheaper computing units.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If expensive computing processing units with fast calculation processing speed are used to accurately apply high-order harmonic voltages at high rotation speeds, then the calculation processing speed is improved, but the cost of the control device increases

Engineering Contradiction:

Improvecalculation processing speedVSAvoidcost of control device

Core Design Contradiction:

SpeedVSDevice complexity

Solution Approach 1:

The patent changes the calculation method parameters by using a simplified approach that adds or subtracts an offset value to the basic voltage commands instead of calculating high-order harmonic voltages through complex equations. This parameter change in the calculation methodology reduces the computational load significantly, enabling the use of cheaper computing units while maintaining adequate performance at high rotation speeds

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent replaces expensive computing processing units with cheaper alternatives by simplifying the calculation algorithm. The simplified method using offset addition/subtraction allows inexpensive computing units to handle the voltage command calculations adequately, eliminating the need for costly high-performance processors

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

2Device complexity

If simple calculation processing is used to reduce calculation load, then the cost of computing processing units is reduced, but the accuracy of high-order voltage application may be compromised

Engineering Contradiction:

Improvecost of control deviceVSAvoidaccuracy of voltage application

Core Design Contradiction:

Device complexityVSManufacturing precision

Solution Approach 1:

The patent introduces an offset value as an intermediary element that, when added to or subtracted from the basic voltage commands, produces the effect of high-order harmonic voltage superposition. This intermediary approach simplifies the calculation while maintaining the necessary voltage application accuracy, as the offset value compensates for the simplified methodology

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentEP3364538B1Ac rotating machine control device and electric power steering device equipped with same

Publication Date: 2021.06.02 MITSUBISHI ELECTRIC CORP

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AI summary

To provide an AC rotary machine control device which can superimpose the 5th order and the 7th order harmonic voltages on the AC voltage applied to the AC rotary machine by calculation processing of low processing load, and an electric power steering device provided with the same. An AC rotary machine control device performs middle voltage offset processing that adds offset value to middle voltage command when middle voltage command in three phase basic voltage commands (Vub, Vvb, Vwb) is larger than vibration center voltage, and subtracts offset value from middle voltage command when middle voltage command is smaller than vibration center voltage.