AC Instantaneous Feedback Control for Inverter Transient Performance

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Solution Overview

Problem

Existing power control systems for dynamically varying loads with resistance and inductance, such as aircraft starter-generators, suffer from poor transient performance and high Total Harmonic Distortion (THD) due to the use of DC feedback signals, leading to current oscillations, torque ripple, and power loss.

Innovation Solution

The implementation of an AC-based control system with nested control loops and feed-forward signaling, utilizing proportional controllers and phase-shift analysis to provide accurate control of alternating current without relying on DC representations, thereby minimizing THD and transient distortions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If DC feedback signal is used for current control, then the control system is simple to implement, but the transient performance is poor and THD is high

Engineering Contradiction:

Improvecontrol system complexityVSAvoidtransient performance

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The patent changes the fundamental parameter of the feedback signal from DC representation to AC instantaneous representation. This allows the control system to respond to rapid changes in load conditions while maintaining simplicity through direct AC signal processing rather than complex rectification and filtering stages

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent replaces the mechanical filtering process (large physical filters) with an electronic signal processing approach using instantaneous AC feedback. This substitution eliminates the need for bulky filter components while achieving superior transient response through electronic control

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Stability of the object's composition

If large filters are used to produce DC feedback signal, then the DC feedback signal is stable, but the transient performance of current control is poor

Engineering Contradiction:

ImproveDC feedback signal stabilityVSAvoidtransient performance

Core Design Contradiction:

Stability of the object's compositionVSReliability

Solution Approach 1:

The patent inverts the conventional approach by not converting AC to DC for feedback, but rather using the AC instantaneous signal directly. This inversion eliminates the need for filters while maintaining signal stability through direct AC measurement and control

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The patent extracts only the necessary information from the AC current waveform without requiring full rectification and filtering. By using instantaneous AC representation, the system extracts real-time current magnitude and phase information directly, eliminating the extraction bottleneck caused by filter limitations

Inventive Principle:

Principle #2Taking out (Extraction)

3Ease of operation

If DC representation of AC current is used, then the feedback signal is easy to process, but information related to AC current waveform is lost

Engineering Contradiction:

Improvefeedback signal processingVSAvoidAC current waveform information

Core Design Contradiction:

Ease of operationVSLoss of information

Solution Approach 1:

The patent introduces an intermediary AC signal processing stage that preserves waveform information while enabling control. The instantaneous AC feedback acts as an intermediary between the AC current and the control system, maintaining all waveform characteristics without requiring full rectification to DC

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent transitions from one-dimensional DC magnitude representation to two-dimensional AC instantaneous representation that captures both magnitude and phase information. This dimensional enhancement allows complete waveform information to be preserved while still providing processed feedback for control

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

4Device complexity

If proportional-integral controller is used with DC feedback, then the control system is straightforward, but current oscillations and torque ripple occur

Engineering Contradiction:

Improvecontroller structureVSAvoidcurrent oscillations and torque ripple

Core Design Contradiction:

Device complexityVSObject-generated harmful factors

Solution Approach 1:

The patent transitions from static DC feedback control to dynamic AC instantaneous feedback control. This allows the controller to adapt in real-time to changing load conditions, preventing oscillations and torque ripple through continuous dynamic adjustment rather than fixed DC-level control

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent enhances the feedback mechanism by using instantaneous AC current representation instead of averaged DC representation. This provides real-time feedback that captures rapid changes in load conditions, enabling the controller to correct deviations before they manifest as oscillations or torque ripple

Inventive Principle:

Principle #23Feedback

Data Source

PatentUS7852646B2Instantaneous load current control scheme for voltage fed DC to AC inverter supplying resistive-inductive load

Publication Date: 2010.12.14 HONEYWELL INTERNATIONAL INC

AI summary

A control system is provided for controlling varying alternating current (AC) to a load with varying resistance and inductance. A plurality of nested control loops may employ cascaded proportional controllers to provide desired control of a pulse width modulation (PWM) block to control an inverter that supplies AC power to the load. An AC feedback signal may be supplied to each proportional controller. An AC signal may be added to outputs of the proportional controllers.