Matrix Converter Control for Harmonic Ripple Reduction

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Solution Overview

Problem

Direct-type AC power converters with a DC link but without a smoothing capacitor face challenges in handling harmonic components in the current flowing to inductive loads like motors, leading to ripple in active power and unsuppressed power-source harmonics.

Innovation Solution

A power converter control method that adjusts the voltage control rate of a voltage-source inverter to include both DC and AC components, specifically targeting the ratio of AC to DC components to match the harmonic components in the current, thereby reducing the ripple caused by odd-number-order harmonic components in the load current.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If concentrated winding is employed in motor armature to reduce copper loss, then efficiency is improved and copper amount is reduced, but harmonic components (fifth-order and seventh-order) are generated in armature current

Engineering Contradiction:

Improvecopper lossVSAvoidharmonic components in current

Core Design Contradiction:

Loss of energyVSObject-generated harmful factors

Solution Approach 1:

The patent converts the harmful harmonic components generated by concentrated winding into beneficial effects by intentionally introducing compensation harmonics through the inverter. The control method generates specific harmonic components in the inverter output voltage that counteract the harmful harmonics in the motor back-EMF, thereby eliminating the harmful current harmonics while maintaining the efficiency benefits of concentrated winding

Inventive Principle:

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

2Volume of stationary object

If direct-type AC power converter is used without smoothing capacitor, then converter size is reduced, but ripple in active power occurs and power-source harmonics are not suppressed

Engineering Contradiction:

Improveconverter sizeVSAvoidripple in active power and power-source harmonics

Core Design Contradiction:

Volume of stationary objectVSObject-generated harmful factors

Solution Approach 1:

The patent converts the ripple energy in active power, which would normally be harmful, into a useful control signal. By detecting the ripple component and using it to generate compensation voltage commands, the system eliminates power-source harmonics and active power ripple simultaneously, maintaining the compact size advantage of direct-type converters without suffering from their typical drawbacks

Inventive Principle:

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

Solution Approach 2:

The patent implements a feedback mechanism where the ripple component of active power is detected and used to adjust the inverter output voltage. The control method calculates the ripple component from the instantaneous active power, generates compensation voltage commands based on this feedback, and applies them to eliminate the harmful effects, creating a closed-loop control system

Inventive Principle:

Principle #23Feedback

Data Source

PatentUS8964424B2Power converter, control method thereof, and direct matrix converter

Publication Date: 2015.02.24 DAIKIN INDUSTRIES LTD

AI summary

A voltage control rate of an inverter has a DC component and an AC component. This AC component has a frequency which is six times a fundamental frequency of an AC voltage outputted by the inverter. Even when there are not only a fifth-order harmonic component but also a seventh-order harmonic component of a load current, a ratio between the magnitude of the AC component and the DC component can be appropriately set.