Brushless Motor Current Control with Integral Wind-Up Limiting
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In motor control systems, voltage saturation leads to a wind-up phenomenon where current deviations persist, causing instability and prolonged convergence issues, especially during changes in current command values, due to excessive integral values accumulation.
Innovation Solution
Implementing a motor control device and method that limits the integrated values of the d and q axes within predetermined ranges to prevent excessive changes during voltage saturation, thereby stabilizing current control by curbing the accumulation of integral errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If integral control is continuously executed during voltage saturation, then the current deviation is driven toward zero through feedback control, but the integrated value excessively increases or decreases causing wind-up phenomenon and deteriorating current control stability
Solution Approach 1:
The patent applies preliminary action by detecting voltage saturation before it causes excessive integral accumulation. The controller monitors the relationship between voltage command values and actual output voltages, and when saturation is detected, it preemptively limits the integrated value of current deviations. This prevents the wind-up phenomenon from occurring in the first place, rather than correcting it after damage is done.
Solution Approach 2:
The patent changes the parameter of integrated value limits dynamically based on system state. During voltage saturation, the controller sets upper and lower limits for the integrated values of d-axis and q-axis current deviations. These limits are adjusted according to the saturation condition, allowing the integral control to remain effective within safe boundaries while preventing excessive accumulation that would cause wind-up.
2Adaptability or versatility
If the current command value is changed after voltage saturation occurs, then the control system needs to respond to the new command, but the excessively changed integrated value causes prolonged convergence and transient instability
Solution Approach 1:
The patent uses feedback by continuously monitoring current detection values against current command values to generate current deviations. This feedback loop drives the integral control to adjust the voltage commands. However, during voltage saturation, the feedback mechanism is modified by limiting the integrated values, preventing the feedback from causing excessive wind-up while still maintaining the ability to respond to command changes.
Solution Approach 2:
The patent applies dynamics by making the integral control behavior adaptive to system conditions. The limiting of integrated values is dynamically applied only during voltage saturation conditions, not during normal operation. This allows the system to maintain full integral control capability during normal states while preventing wind-up during saturation, enabling smooth transitions and stable transient response when current commands change.
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A controller in a motor control device includes an integral operation unit 606A (608A) that performs an arithmetic operation for a d(q)-axis integrated value Id∗∗ (Iq∗∗) through integral control performed on a d(q)-axis current deviation ΔId (ΔIq) and is configured to perform an arithmetic operation for a d(q)-axis voltage command value for controlling an output voltage of an inverter of a three-phase brushless motor. The controller further includes a limit value arithmetic operation unit 606C (608C) that performs an arithmetic operation for d(q)-axis integration upper and lower limit values Idmax (Iqmax) and Idmin (Iqmin) on the basis of a power source voltage of the inverter and the like and an integration limiting unit 606D (608E) that limits Id∗∗ (Iq∗∗) within a predetermined range defined by the d(q)-axis integration upper and lower limit values.