Self-Tuning Digital Control Loop for Power Factor Correction

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Solution Overview

Problem

AC-to-DC rectifiers in electronic power systems introduce frequency harmonics, leading to issues like high neutral current, excessive heating, and reduced operating life of transformers and induction motors, necessitating improved performance of power converter circuits.

Innovation Solution

A power converter circuit with a digital control loop having an adjustable transfer function, including a tuning module that sets a zero variable and signal gain variable, iteratively updates the gain value to minimize control error, and sets the operating gain value for optimal performance, thereby self-tuning to reduce total harmonic distortion (THD).

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Power

If AC-to-DC rectifiers are used in power systems, then power conversion is achieved, but frequency harmonics are introduced causing high neutral current, excessive heating, and reduced component lifespan

Engineering Contradiction:

Improvepower conversion capabilityVSAvoidfrequency harmonics

Core Design Contradiction:

PowerVSObject-generated harmful factors

Solution Approach 1:

The patent applies this principle by using the detected harmonic frequencies and amplitudes (the harmful factors) to generate compensation signals that cancel out the harmonics. The harmful harmonic content is converted into useful information for creating corrective waveforms through adaptive filtering and signal synthesis

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The patent implements feedback by continuously monitoring the output waveform for harmonic content, analyzing the spectral composition, and adjusting the compensation signals in real-time. The system uses the detected harmonic characteristics to dynamically modify the compensation waveform, creating a closed-loop control system that adapts to changing load conditions

Inventive Principle:

Principle #23Feedback

2Device complexity

If fixed gain amplifier circuits are used, then circuit simplicity is maintained, but optimal performance across varying operating conditions cannot be achieved

Engineering Contradiction:

Improvecircuit simplicityVSAvoidperformance optimization

Core Design Contradiction:

Device complexityVSProductivity

Solution Approach 1:

The patent applies this principle by replacing fixed gain amplifier circuits with digitally controllable variable gain amplifiers whose gain parameters can be dynamically adjusted based on operating conditions. The system dynamically modifies compensation signal characteristics including gain, frequency, and phase to match real-time load requirements

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent implements parameter changes by using digital signal processing to continuously adjust the parameters of compensation signals (gain, frequency, phase) based on spectral analysis of the output waveform. The system changes these parameters adaptively to maintain optimal performance across varying load conditions while keeping the hardware architecture relatively simple

Inventive Principle:

Principle #35Parameter changes

3Ease of operation

If manual tuning of compensation parameters is performed, then initial setup is possible, but adaptation to changing load conditions and optimal harmonic reduction cannot be achieved

Engineering Contradiction:

Improvemanual setup capabilityVSAvoidload condition adaptation

Core Design Contradiction:

Ease of operationVSAdaptability or versatility

Solution Approach 1:

The patent applies this principle by implementing an automatic tuning system that performs spectral analysis of the output waveform, identifies harmonic frequencies and amplitudes, and autonomously generates appropriate compensation signals without requiring manual intervention. The system self-adjusts compensation parameters based on real-time measurements of the power system state

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

Inventive Principle:

Principle #23Feedback

Data Source

PatentUS9231469B2Auto-tuning current loop compensation for power factor correction controller

Publication Date: 2016.01.05 ANALOG DEVICES INC

AI summary

An apparatus comprises a power converter circuit and a controller. The power converter circuit includes an inductor, a switching circuit, and a digital control loop circuit having an adjustable transfer function, wherein the transfer function includes a zero variable and a signal gain variable. The controller includes a tuning module configured to set a value for the zero variable, set the signal gain variable to a first gain value, determine a control error for the first gain value setting, wherein the control error is a difference between a reference current and a load current at a circuit load, iteratively update the gain value of the signal gain variable and determine the control error for the updated gain value, and set an operating gain value of the signal gain variable to the gain value corresponding to a minimum control error.