Parallel Device Control Using Averaged Integral Terms
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Solution Overview
Problem
Control systems for parallel operating devices, such as mechanically coupled motors or electric machines, face challenges in maintaining stability due to infinite gain at zero frequency, leading to excessive control force usage and inaccuracies when trying to synchronize rotational speeds or voltages, and existing solutions like master-slave configurations or drooping introduce complexity and inaccuracies.
Innovation Solution
Implementing a control system where each controller maintains a device-specific integral term and computes an arithmetic average with other controllers' terms to correct its integral term, allowing for dynamic redundancy and avoiding unwanted drifts, enabling seamless addition or removal of devices without human intervention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a standard PI controller is used to control parallel operating devices, then the operating quantity can be driven towards a target value, but the integral action causes infinitely large gain at zero frequency leading to excessive control force and instability
Solution Approach 1:
The patent implements a feedback mechanism where each controller receives the integral terms from other controllers and adjusts its own integral term accordingly. This feedback loop allows the system to detect and correct imbalances in control forces, preventing the excessive control force buildup that would otherwise occur with standard PI controllers. The feedback ensures that when one controller detects an error, it doesn't unilaterally apply maximum correction force, thereby maintaining stability while still achieving accurate target tracking.
Solution Approach 2:
The patent merges the integral terms of multiple controllers by having each controller maintain not only its own device-specific integral term but also receive and utilize integral terms from other controllers. This merging approach allows the controllers to collectively manage the integral action, distributing the correction effort evenly across all parallel devices. By combining the integral terms, the system achieves coordinated control that prevents any single controller from dominating the correction process, thus resolving the stability issue while maintaining accuracy.
2Stability of the object's composition
If a master-slave configuration is used to control parallel operating devices, then control stability is improved, but device complexity and commissioning burden increase
Solution Approach 1:
The patent makes all controllers universal by giving each controller the same capabilities to maintain integral terms, receive other controllers' integral terms, and adjust its own integral term based on received data. No controller is designated as master or slave; instead, all controllers perform identical functions and follow the same control algorithm. This universality eliminates the need for different configuration modes, reduces commissioning complexity, and allows dynamic addition or removal of devices without reconfiguring the system architecture.
Solution Approach 2:
The patent implements a dynamic control architecture where controllers can be added or removed from the parallel system without requiring manual reconfiguration or intervention. The system dynamically adapts to changes in the number of operating devices, with each controller automatically adjusting its behavior based on the current set of active controllers. This dynamic approach eliminates the static master-slave roles and simplifies system maintenance and expansion.
3Stability of the object's composition
If drooping is applied to parallel operating devices, then control stability is improved, but manufacturing precision and operating accuracy deteriorate
Solution Approach 1:
The patent uses feedback to maintain high synchronization accuracy by having each controller continuously monitor and adjust its integral term based on received integral terms from other controllers. This feedback mechanism allows the system to detect and correct any drift or deviation in real-time, maintaining precise synchronization without the need for drooping. The feedback ensures that the operating accuracy is preserved while achieving stability, unlike drooping which intentionally introduces error.
Solution Approach 2:
The patent dynamically adjusts the integral terms of controllers based on the integral terms of other controllers in the system. By changing the parameter values of integral terms through coordinated adjustment rather than fixed drooping, the system maintains both stability and precision. The integral terms are modified in response to system conditions and peer controller states, allowing accurate synchronization to be maintained while achieving stable parallel operation.
Data Source
AI summary
A device-system comprises parallel operating devices (105-107) for driving an operating quantity towards a target value, and a control system for controlling each device at least partly based on a device-specific integral term relating to a time integral of a device-specific error signal that is indicative of a deviation of the operating quantity from the target value. The control system comprises a stabilizing system that computes an arithmetic average of the device-specific integral terms and corrects the device-specific integral terms towards the computed arithmetic average. The correction of the device-specific integral terms makes it possible to avoid unwanted drifts in the device-specific integral terms in a situation where there are differences between the device-specific error signals. The devices can be peers to each other and thus redundancy is achieved because one device can be removed from or added to the device-system without actions from the other devices.