Motor Current Control With Field Delay Compensation

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Solution Overview

Problem

Existing motor control technologies face efficiency reduction due to changes in motor characteristics, such as temperature changes, which affect the current command maps and optimal current ratios in salient-type synchronous motors, leading to suboptimal torque response and increased copper loss.

Innovation Solution

A motor control device that acquires regular motor state data to update motor parameters and calculates current commands for windings based on these parameters, incorporating a response delay reproduction unit to simulate the field winding current delay, ensuring accurate current command generation and minimizing copper loss.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If a current command map prepared through measurement in advance is used to compensate torque loss due to field current response delay, then torque response is improved, but device complexity increases and efficiency reduces when motor characteristics change due to temperature variations

Engineering Contradiction:
Improvetorque response speedVSAvoidcontrol system complexity
Core Design Contradiction:
SpeedVSDevice complexity

Solution Approach 1:

The patent applies preliminary action by calculating and applying current correction values in advance based on the torque command, rather than relying on pre-measured maps. The correction value calculation unit computes the necessary compensation before the actual torque generation, allowing the system to adapt to changing motor characteristics dynamically while maintaining fast torque response.

Inventive Principle:
Principle #10Preliminary action

Solution Approach 2:

The patent implements dynamics by making the current correction values dynamic and adaptive to changing motor conditions. Instead of using fixed pre-measured maps, the system continuously calculates correction values based on real-time torque commands and motor state, allowing the control parameters to adjust automatically when motor characteristics change due to temperature variations or other factors.

Inventive Principle:
Principle #15Dynamics

2Ease of manufacture

If pre-measured current command maps are used for control, then initial setup is simplified, but the system cannot adapt to motor characteristic changes, reducing efficiency

Engineering Contradiction:
Improveinitial system setupVSAvoidadaptation to motor characteristic changes
Core Design Contradiction:
Ease of manufactureVSAdaptability or versatility

Solution Approach 1:

The patent applies self-service by enabling the control system to automatically calculate and adjust current correction values without requiring external re-calibration or re-measurement when motor characteristics change. The correction value calculation unit continuously adapts the control parameters based on real-time operating conditions, allowing the system to self-adjust to temperature variations and other environmental factors.

Inventive Principle:
Principle #25Self-service

Solution Approach 2:

The patent implements parameter changes by dynamically modifying the current command parameters based on real-time torque commands and motor state. The system changes the correction values applied to the field current and stator current commands according to actual operating conditions, allowing optimal performance across varying motor characteristics without requiring fixed pre-measured maps.

Inventive Principle:
Principle #35Parameter changes

3Loss of energy

If optimal current ratio is set for salient-type synchronous motor, then efficiency is maximized, but efficiency reduces when motor characteristics change due to temperature

Engineering Contradiction:
Improvecopper lossVSAvoidmotor temperature variation
Core Design Contradiction:
Loss of energyVSTemperature

Solution Approach 1:

The patent applies feedback by using the actual torque command and motor state information to continuously adjust the current correction values. The correction value calculation unit receives feedback about the current operating conditions and modifies the field current and stator current commands accordingly, ensuring that the optimal current ratio is maintained even when motor characteristics change due to temperature variations.

Inventive Principle:
Principle #23Feedback

Data Source

PatentEP3961909B1Motor control device
Publication Date: 2024.01.10 MITSUBISHI ELECTRIC CORP
  • EP3961909B1 patent drawingFigure 1
  • EP3961909B1 patent drawingFigure 2
  • EP3961909B1 patent drawingFigure 3~5

AI summary

An object is to obtain a motor control device that can prevent reduction in efficiency even when motor characteristics are changed. This motor control device controls a motor having a first stator winding, a second stator winding, and a field winding whose response to a current command is slower than those of the first stator winding and the second stator winding, and includes: a parameter acquisition unit (61) which regularly acquires motor state data (62) indicating the state of the motor, and acquires a motor parameter (63) corresponding to the motor state data (62); and a current command calculation unit (60) which calculates current commands for the windings on the basis of a torque command for the motor and the motor parameter (63). The current command calculation unit (60) includes a response delay reproduction unit which reproduces response delay of field winding current in a field winding current command, and calculates a first stator winding current command and a second stator winding current command, using the field winding current command in which the response delay is reproduced.