Inverter Control Architecture for Subharmonic Oscillation Suppression

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Solution Overview

Problem

Conventional synchronous frame current regulators struggle to suppress subharmonic current errors at high frequencies in electric motor inverters, leading to motor speed oscillations and efficiency losses due to low frequency disturbances.

Innovation Solution

A control architecture combining a synchronous frame current regulator with a stationary frame current regulator, utilizing an adaptive filter module to extract and regulate subharmonic current components, effectively controlling both fundamental and subharmonic currents by generating adjustment voltage commands.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If synchronous frame current regulator is used for high frequency operation, then current control capability over wide frequency range is achieved, but subharmonic current error cannot be suppressed due to low frequency disturbances

Engineering Contradiction:

Improvecurrent control capability over wide frequency rangeVSAvoidsuppression of subharmonic current error

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The patent divides the current regulator into two separate parallel regulators: a synchronous frame current regulator for controlling fundamental frequency current, and a stationary frame current regulator for controlling low frequency subharmonic current components. This segmentation allows each regulator to specialize in its frequency range, resolving the contradiction between wide frequency adaptability and subharmonic suppression capability.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent introduces an adaptive filter as an intermediary component that extracts low frequency subharmonic current components from the total current before they enter the stationary frame current regulator. This intermediary filtering mechanism enables the stationary frame regulator to focus specifically on subharmonic components, improving its effectiveness in suppressing current errors while maintaining overall system adaptability.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Power

If output frequency is increased to 1.0 kHz for high voltage utilization, then torque efficiency is improved, but DC offset in current is interpreted as 1.0 kHz current error in synchronous reference frame

Engineering Contradiction:

Improvetorque efficiencyVSAvoidcurrent error interpretation accuracy

Core Design Contradiction:

PowerVSMeasurement precision

Solution Approach 1:

The adaptive filter acts as an intermediary that separates low frequency subharmonic components from the high frequency fundamental current before processing. This allows the synchronous frame current regulator to accurately process the 1.0 kHz fundamental current for torque control, while the stationary frame regulator handles the low frequency offset errors, preventing misinterpretation of DC offset as high frequency current error.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent segments the current processing into two parallel paths: one for fundamental frequency current control (synchronous frame) and one for low frequency error correction (stationary frame). This segmentation enables the system to maintain high output frequency for torque efficiency while simultaneously correcting frequency-dependent measurement errors through dedicated low frequency processing.

Inventive Principle:

Principle #1Segmentation

3Ease of operation

If synchronous frame current regulator operates alone, then fundamental frequency current is controlled, but low frequency subharmonic oscillations result in motor speed oscillations and efficiency losses

Engineering Contradiction:

Improvesimplicity of control architectureVSAvoidmotor efficiency

Core Design Contradiction:

Ease of operationVSLoss of energy

Solution Approach 1:

The patent segments the control architecture into two parallel current regulators with distinct functions: synchronous frame regulator for fundamental current control and stationary frame regulator for subharmonic suppression. This segmentation adds only one more regulator block to the architecture, maintaining relative simplicity while effectively eliminating low frequency oscillations that cause motor efficiency losses and speed variations.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent merges two current regulation approaches (synchronous frame and stationary frame) into a unified parallel control architecture. This combination allows the system to simultaneously achieve fundamental frequency current control and low frequency subharmonic suppression, improving motor efficiency without significantly complicating the overall control structure.

Inventive Principle:

Principle #5Merging (Combining)

Data Source

PatentUS7449859B2Reduction of subharmonic oscillation at high frequency operation of a power inverter

Publication Date: 2008.11.11 GM GLOBAL TECHNOLOGY OPERATIONS LLC

AI summary

A control architecture for an electrical inverter includes a synchronous frame current regulator and a stationary frame current regulator. The stationary frame current regulator receives input currents that represent filtered versions of stationary frame currents that correspond to the inverter output currents. The control architecture employs an adaptive filter module that filters the stationary frame currents to remove the fundamental motor frequency component (and its related harmonics), thus extracting any low frequency harmonic components. The stationary frame current regulator processes the low frequency components, while the synchronous frame current regulator processes the fundamental frequency component, resulting in suppression of low frequency oscillations in the inverter output.