Motor Controller Power Factor Correction via DC Link Voltage

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Solution Overview

Problem

Existing electric motor controllers face challenges in reducing size and cost while maintaining a high power factor, as they often rely on large and costly active power factor correction devices or require additional sensors to correct poor power factor, and the use of small-capacity capacitors leads to pulsating waveforms and poor sinusoidal input currents.

Innovation Solution

A motor controller system that includes an inverter and a rectifier, where the controller improves the power factor by controlling the AC input current based on a DC link voltage measurement, eliminating the need for large filter capacitors and additional sensors, using algorithms and sinusoidal waveform generation to modulate the AC input current and optimize power factor correction.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Stability of the object's composition

If large-capacity smoothing capacitors are used to smooth rectified input voltage, then voltage smoothing is improved, but device size and cost increase

Engineering Contradiction:

Improvevoltage smoothingVSAvoidcapacitor size

Core Design Contradiction:

Stability of the object's compositionVSVolume of stationary object

Solution Approach 1:

The patent extracts the voltage smoothing function from large-capacity capacitors by implementing active power factor correction control that shapes the input current to be sinusoidal and in-phase with the input voltage, thereby eliminating the need for large smoothing capacitors while maintaining voltage stability

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent changes the control parameters of the inverter to actively regulate the input current waveform, transforming the passive rectification process into an active power factor correction process that maintains voltage smoothing without requiring large capacitor components

Inventive Principle:

Principle #35Parameter changes

2Volume of stationary object

If small-capacity capacitors are used to reduce size, then device size is reduced, but voltage smoothing deteriorates and pulsating waveform is produced

Engineering Contradiction:

Improvecapacitor sizeVSAvoidvoltage smoothing

Core Design Contradiction:

Volume of stationary objectVSStability of the object's composition

Solution Approach 1:

The patent replaces the passive mechanical/electrical smoothing mechanism (large capacitors) with an active control system that uses feedback from DC link voltage measurement to dynamically adjust the inverter switching, thereby achieving voltage smoothing through control rather than component size

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent implements feedback control by measuring the DC link voltage and using this information to adjust the inverter's input current waveform, creating a closed-loop system that maintains voltage stability without requiring large capacitors

Inventive Principle:

Principle #23Feedback

3Adaptability or versatility

If active power factor correction devices are used to correct power factor, then power factor is improved, but device size and cost increase

Engineering Contradiction:

Improvepower factor correctionVSAvoidcorrection device size

Core Design Contradiction:

Adaptability or versatilityVSVolume of stationary object

Solution Approach 1:

The patent makes the inverter multi-functional by enabling it to perform both motor drive control and active power factor correction functions simultaneously, eliminating the need for separate power factor correction devices and reducing overall system size

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The patent merges the power factor correction function with the inverter control system, combining what would traditionally be separate devices into a single integrated system that achieves both motor control and power factor correction

Inventive Principle:

Principle #5Merging (Combining)

4Measurement precision

If additional isolated voltage sensors are added to measure line input voltage, then power factor measurement is enabled, but system cost increases

Engineering Contradiction:

Improvepower factor measurementVSAvoidsensor quantity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent enables the inverter to self-measure the necessary parameters for power factor correction by using its existing voltage sensing capability to measure DC link voltage, eliminating the need for additional external sensors and reducing system complexity

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The patent uses DC link voltage as an intermediary measurement that provides the necessary information for power factor control without requiring direct measurement of line input voltage, thereby avoiding the need for additional isolated sensors

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS9331614B2Systems and methods for controlling electric machines

Publication Date: 2016.05.03 REGAL BELOIT AMERICA INC

AI summary

A motor controller is provided that includes an inverter configured to drive an electric motor, a rectifier configured to rectify an alternating current (AC) input current and to output the rectified AC input current to the inverter, and a controller coupled to the inverter. The controller is configured to improve a power factor of the motor controller by controlling the AC input current based on a direct current (DC) link voltage measurement.