Anti-windup Module Minimizing Supply Current in Voltage Saturated Motor Drives
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Solution Overview
Problem
Motor control systems face challenges in managing supply current under voltage saturation conditions, leading to controller windup and instability, particularly in electric power steering systems, where existing anti-windup techniques prioritize motor torque or current maximization over supply current minimization.
Innovation Solution
A motor control system incorporating a voltage limiting module and an anti-windup module that computes an anti-windup feedback current using a gain matrix to minimize supply current by moving the motor current trajectory towards a null motor current vector, preventing controller windup and reducing supply current draw during voltage saturation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If voltage limiting is applied to prevent saturation, then controller stability is improved, but supply current increases due to lack of anti-windup compensation
Solution Approach 1:
The patent implements feedback by computing the difference between pre-limit and post-limit voltage commands and feeding this difference back through compensation gains to adjust the current command. This feedback mechanism prevents controller windup while actively managing supply current, resolving the contradiction between stability and energy consumption.
Solution Approach 2:
The patent dynamically changes control parameters by adjusting current commands based on voltage difference and compensation gains. This parameter adaptation allows the system to maintain stability under voltage limiting while optimizing supply current consumption, rather than using fixed control parameters.
2Reliability
If existing anti-windup techniques are used to prevent controller windup, then controller stability is improved, but supply current is not minimized as torque maximization is prioritized
Solution Approach 1:
The patent changes the control objective parameter from torque maximization to supply current minimization by using compensation gains that actively reduce supply current. This parameter change allows the system to maintain anti-windup functionality while optimizing for energy consumption rather than torque output.
Solution Approach 2:
The patent applies local quality by implementing supply current minimization specifically under voltage saturation conditions rather than uniformly across all operating conditions. The compensation gains are activated selectively when voltage limiting occurs, providing targeted current management where needed.
3Reliability
If voltage limiting threshold is set low to prevent saturation, then controller windup is reduced, but motor torque capability is reduced
Solution Approach 1:
The patent dynamically adjusts current command parameters based on the voltage difference and compensation gains, allowing the system to maintain higher voltage limits for torque capability while actively managing current to prevent windup. This parameter adaptation resolves the trade-off between voltage limit setting and torque output.
Data Source
AI summary
A system and method for improved anti-windup that minimizes supply current draw under voltage saturated current control operation of synchronous motor drives are provided. The system and method use a voltage limiting module configured to receive a pre-limit voltage command and generate a post-limit voltage command when the motor control system reaches configured threshold; and an anti-windup module configured to determine a voltage difference between the post-limit and pre-limit voltage commands, and compute an anti-windup feedback current using the voltage difference and compensation gains selected to minimize supply current. The compensation gains comprise a gain matrix of values selected to move a motor current trajectory toward a null motor current vector, and the anti-windup module multiplies the gain matrix values by the voltage difference. The anti-windup feedback current and an input current command are then added and provided as an input to the controller.