Motor Inverter Offset-Wave Control for Harmonic Suppression

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Solution Overview

Problem

Inverters that convert DC voltage to AC voltage produce non-smooth waveforms with non-differentiable points, leading to high-order harmonics and noise when driving motors.

Innovation Solution

An inverter circuit with three or more phases, utilizing series-connected semiconductor switching elements and offset waveforms to generate smooth AC output waveforms by varying switching frequencies and durations, suppressing high-order harmonics.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If waveforms containing non-smooth points are superimposed to generate output waveform, then the modulation waveform can be generated, but the output waveform contains many high-order harmonics causing noise or torque unevenness

Engineering Contradiction:

Improveoutput waveform generationVSAvoidnoise and torque unevenness

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The patent applies dynamics by making the switching elements operate with time-varying switching patterns rather than fixed patterns. The switching duration and frequency are dynamically adjusted to ensure smooth transitions, eliminating non-differentiable points in the output waveform while maintaining efficient power conversion.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent changes the waveform parameters by ensuring that the output voltage waveform is continuously differentiable. This is achieved by carefully controlling the switching timing and duration of the semiconductor elements, transforming the waveform characteristics to eliminate high-order harmonics while preserving the fundamental output function.

Inventive Principle:

Principle #35Parameter changes

2Loss of energy

If switching elements are switched at high frequency to generate AC output, then power conversion efficiency is improved, but non-smooth waveforms with non-differentiable points are generated

Engineering Contradiction:

Improvepower conversion efficiencyVSAvoidwaveform smoothness

Core Design Contradiction:

Loss of energyVSShape

Solution Approach 1:

The patent uses dynamic switching control where the switching elements are operated with time-varying patterns. The switching duration is adjusted dynamically within each cycle to ensure that voltage transitions are smooth and continuous, eliminating non-differentiable points while maintaining high-frequency switching for efficient power conversion.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent ensures continuous and smooth voltage output by carefully coordinating the switching actions of multiple semiconductor elements. The switching patterns are designed to maintain continuous conduction and smooth voltage transitions, ensuring that the useful power conversion action continues without creating discontinuities or non-differentiable points in the output waveform.

Inventive Principle:

Principle #20Continuity of useful action

Data Source

PatentUS12556122B2Inverter circuit and motor module

Publication Date: 2026.02.17 NIDEC CORP(JP)

AI summary

An inverter circuit includes at least three output terminals, a first input terminal, a second input terminal, and at least three series bodies. A total switching duration and a one-phase fixed duration are present within a single cycle of AC output. The waveform of each phase of an output voltage is such that a shared offset wave is deducted from a sinusoidal waveform. The waveform of the offset wave matches one phase of the sinusoidal waveform, or matches a waveform obtained by shifting the one phase of the sinusoidal waveform in the amplitude direction, during the one-phase fixed duration. During switching between the total switching duration and the one-phase fixed duration, the inclination of the waveform of the offset wave either continuously changes or remains fixed.