Phase Current Amplitude Correction in Rotary Electric Machines

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Solution Overview

Problem

Current detection apparatuses for multiphase rotary electric machines face variations in phase current amplitudes due to temperature and individual differences in switches, leading to reduced controllability and fluctuations in controlled variables.

Innovation Solution

A current detection apparatus that includes an arm current detection unit, a bus current detection unit, and an amplitude correction unit to detect and correct phase currents, ensuring matched amplitudes and reducing variations, thereby maintaining higher controllability of the rotary electric machine.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If phase currents are detected based on potential difference across detection switches, then current detection is achieved, but variations in switch individual differences and temperatures cause amplitude variations in detected currents

Engineering Contradiction:

Improvephase current detection accuracyVSAvoidcontrollability of rotary electric machine

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The system detects actual phase currents using the arm current detection unit, compares them with commanded currents, and feeds back the difference to the control unit. This feedback mechanism allows the control unit to adjust control signals to compensate for amplitude variations caused by switch individual differences and temperature changes, thereby maintaining reliable controllability.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The system dynamically adjusts detection parameters by selecting different detection switches based on their on-state conditions. The control unit monitors the on-state of each switch and selects appropriate detection switches to minimize the impact of individual differences and temperature variations, thereby maintaining accurate current detection and reliable control.

Inventive Principle:

Principle #35Parameter changes

2Adaptability or versatility

If multiple detection switches are used for phase current detection, then current detection coverage is improved, but variations in switch characteristics cause amplitude variations in detected currents

Engineering Contradiction:

Improvecurrent detection coverageVSAvoidphase current amplitude consistency

Core Design Contradiction:

Adaptability or versatilityVSMeasurement precision

Solution Approach 1:

The system dynamically selects which detection switches to use based on real-time operating conditions. The control unit monitors the on-state of each switch and adaptively chooses the most suitable detection switches for current detection, ensuring both comprehensive detection coverage and consistent amplitude accuracy across different operating conditions.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The system applies different detection strategies to different phases based on their specific characteristics. Each phase current is detected using the most appropriate detection switch configuration, allowing the system to optimize for local conditions while maintaining overall measurement precision and amplitude consistency.

Inventive Principle:

Principle #3Local quality

3Duration of action of stationary object

If detection switches operate at varying temperatures, then system operation is maintained, but temperature variations cause potential difference variations and current amplitude variations

Engineering Contradiction:

Improvesystem operation continuityVSAvoidphase current amplitude accuracy

Core Design Contradiction:

Duration of action of stationary objectVSMeasurement precision

Solution Approach 1:

The feedback mechanism continuously monitors detected phase currents and compares them with expected values. When temperature variations cause amplitude deviations, the feedback loop enables the control unit to compensate for these variations, maintaining accurate current measurement and control precision throughout continuous system operation.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The system proactively manages temperature effects by selecting detection switches based on their current thermal state. The control unit anticipates temperature-related variations and adjusts detection switch selection accordingly, cushioning against the impact of temperature changes before they significantly affect measurement accuracy.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

Data Source

PatentUS10892698B2Current detection apparatus and control apparatus of rotary electric machine

Publication Date: 2021.01.12 DENSO CORP

AI summary

In a current detection apparatus, an arm current detection unit detects each of at least first and second phase currents having respective amplitudes and flowing in a multiphase rotary electric machine based on a potential difference between input and output terminals of the corresponding one of first and second detection switches during the corresponding one of the first and second detection switches being on. A bus current detection unit detects each of at least bus-based first and second phase currents corresponding to the first and second phases of the multiphase rotary electric machine based on a current flowing through one of first and second buses. An amplitude correction unit corrects the first and second phase currents based on the bus-based first and second phase currents such that the amplitudes of the respective first and second phase currents match with each other.