Multiphase Rotary Machine Control System for Current Accuracy

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Solution Overview

Problem

Existing control systems for multiphase rotary machines reduce the duration of zero vector mode operation at low RPM, leading to increased switching frequency and harmonic waves, which compromises control accuracy and extends periods of current deviation from command values.

Innovation Solution

A control system that utilizes a plurality of voltage vectors to control the difference between actual and command currents, including zero and non-zero vectors, with a calculating unit to determine the direction of change and a zero-vector setting unit to set the switching mode to zero vector based on positional conditions, thereby increasing zero vector mode durations.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If the control system drives switching elements in non-zero vector mode to reduce current difference, then current control accuracy is improved, but zero vector mode duration is reduced and switching frequency increases

Engineering Contradiction:

Improvecurrent control accuracyVSAvoidzero vector mode duration

Core Design Contradiction:

Measurement precisionVSDuration of action of moving object

Solution Approach 1:

The control system dynamically adjusts the switching mode selection based on real-time current difference magnitude. When current difference is large, non-zero vector mode is used for rapid correction; when current difference is small, zero vector mode is used to reduce switching frequency. This dynamic adaptation resolves the contradiction by optimizing the operating mode according to actual control needs.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The system changes the control parameter (switching mode) based on the magnitude of current difference. By setting different switching modes corresponding to different current difference ranges, the system achieves both accurate current control and reduced switching frequency, resolving the technical contradiction between control accuracy and zero vector mode duration.

Inventive Principle:

Principle #35Parameter changes

2Speed

If the control system increases zero vector mode duration to reduce switching frequency, then switching frequency is reduced, but current control accuracy deteriorates

Engineering Contradiction:

Improveswitching frequencyVSAvoidcurrent control accuracy

Core Design Contradiction:

SpeedVSMeasurement precision

Solution Approach 1:

The control system dynamically adjusts the switching mode based on real-time current difference magnitude. When current difference is large, non-zero vector mode is used for rapid correction; when current difference is small, zero vector mode is used to reduce switching frequency. This dynamic adaptation resolves the contradiction by optimizing the operating mode according to actual control needs.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

Inventive Principle:

Principle #35Parameter changes

3Speed

If the control system uses fixed switching mode to reduce current difference, then current control response is improved, but harmonic waves increase

Engineering Contradiction:

Improvecurrent control responseVSAvoidharmonic waves

Core Design Contradiction:

SpeedVSObject-generated harmful factors

Solution Approach 1:

The control system dynamically switches between non-zero vector mode and zero vector mode based on the magnitude of current difference. This dynamic switching strategy enables rapid current control response when needed while reducing harmonic waves by utilizing zero vector mode during appropriate periods, thus resolving the contradiction between control response speed and harmonic wave generation.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The control system employs periodic switching between different vector modes based on current difference magnitude. This periodic action pattern allows the system to achieve rapid control response during critical periods while reducing harmonic content during other periods, effectively resolving the contradiction between response speed and harmonic wave generation.

Inventive Principle:

Principle #19Periodic action

Data Source

PatentUS8154229B2Control system for multiphase rotary machines

Publication Date: 2012.04.10 DENSO CORP

AI summary

In a control system designed to use a plurality of voltage vectors expressing a switching mode for a switching circuit to thereby control a difference between a current actually flowing through a multiphase rotary machine and a command current value therefore within an allowable range, a calculating unit calculates a direction of change in the difference during the switching mode for the switching circuit being set to a zero vector. A zero-vector setting unit sets the switching mode for the switching circuit to the zero vector when a preset positional condition between the difference and the direction of change in the difference is met in a space.