Torque Optimization in Synchronous Motor Drives

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Solution Overview

Problem

Existing electric machine control systems face challenges in efficiently managing multiple constraints such as supply voltage, inverter currents, and regenerative currents to achieve optimal torque, particularly in prioritizing torque maximization while adhering to regenerative current limits.

Innovation Solution

A method and control system that determine voltage-based and motor current-based torque limits, calculate a final torque limit, and adjust current commands to prioritize torque production, exceeding initial current commands to meet torque demands while managing regenerative current limits within the DC bus constraints.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If regenerative current limits are strictly enforced, then system safety and component protection are improved, but torque capability and performance are reduced

Engineering Contradiction:

Improvesystem safetyVSAvoidtorque capability

Core Design Contradiction:

ReliabilityVSPower

Solution Approach 1:

The control system dynamically adjusts the regenerative current limit based on real-time operating conditions. The processor monitors DC bus voltage, motor current, and torque demands, and temporarily exceeds the standard regenerative current limit when torque maximization is prioritized and voltage constraints permit, thereby resolving the contradiction between safety and performance

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The system changes the regenerative current parameter dynamically rather than maintaining a fixed limit. By calculating voltage-based torque limits and comparing them with current-based limits, the system adapts the regenerative current threshold to achieve optimal torque while managing safety constraints

Inventive Principle:

Principle #35Parameter changes

2Reliability

If multiple constraints (voltage, current, regenerative limit) are simultaneously enforced, then system protection is improved, but torque optimization and performance are worsened

Engineering Contradiction:

Improvesystem protectionVSAvoidtorque optimization

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The control system segments the constraint management into distinct evaluation stages. It separately calculates voltage-based torque limits, current-based torque limits, and regenerative current constraints, then integrates them through a prioritization framework that allows torque optimization while maintaining necessary protections

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The processor acts as an intermediary that reconciles multiple constraints. It introduces a voltage-based torque limit calculation as an intermediate step that bridges the gap between regenerative current limits and optimal torque delivery, allowing the system to navigate through constraint conflicts

Inventive Principle:

Principle #24Intermediary (Mediator)

3Power

If regenerative current limit is exceeded for peak torque demands, then torque capability is improved, but risk of damaging DC bus components increases

Engineering Contradiction:

Improvepeak torqueVSAvoidcomponent damage risk

Core Design Contradiction:

PowerVSObject-affected harmful factors

Solution Approach 1:

The system prepares for potential component stress by continuously monitoring DC bus voltage and establishing voltage-based torque limits beforehand. This cushioning approach allows temporary current exceedance while maintaining safety margins through pre-calculated voltage constraints

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

Solution Approach 2:

The control system employs continuous feedback by monitoring DC bus voltage, motor current, and torque demands in real-time. This feedback mechanism allows the processor to dynamically adjust regenerative current limits and immediately respond to conditions that could lead to component damage, enabling peak torque delivery with reduced risk

Inventive Principle:

Principle #23Feedback

Data Source

PatentUS11616457B2Torque capability optimization under active limiting of regenerative current in synchronous motor drives

Publication Date: 2023.03.28 STEERING SOLUTIONS IP HOLDING CORP

AI summary

A method of controlling operation of an electric machine includes: determining a voltage-based torque limit based on a voltage constraint of a direct current (DC) bus supplying power to an inverter for powering the electric machine; determining a motor current-based torque limit based on a motor current limit; determining a final torque limit based on the voltage-based torque limit and the motor current-based torque limit; determining a limited command torque based on a torque command and the final torque limit; determining an initial current command corresponding to the inverter satisfying a regenerative current limit of the DC bus; and calculating a final current command based on, at least, the limited command torque and the initial current command. The method includes the final current command exceeding the initial current command to cause the electric machine to produce a torque corresponding to the limited torque command.