Power Conversion Device Switching Mode Control

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Solution Overview

Problem

Conventional inverters experience increased switching losses and unstable output power due to all arms switching during the zero crossing period, leading to waveform disturbances in AC current.

Innovation Solution

A power conversion device with a full-bridge circuit and a switching-mode changer that synchronously switches two arms and non-conducts the other two, reducing switching losses and stabilizing output power by adjusting the phase of the switching signal to minimize reactive power and distortion in AC voltage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If all arms switch during the period that contains a zero crossing, then the current waveform disturbance near the zero crossing is inhibited, but the switching losses increase

Engineering Contradiction:

Improveoutput power stabilityVSAvoidswitching losses

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The full-bridge circuit is divided into two independent legs, each leg containing an upper arm and a lower arm. The switching control is segmented such that only two arms (one from each leg) switch synchronously during the zero crossing period, while the other two arms remain non-conducting. This segmentation allows selective switching that reduces overall switching losses while maintaining output power stability.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Instead of switching all four arms during the zero crossing period as in conventional inverters, the invention applies partial action by switching only two arms (50% of total arms). This partial switching is sufficient to inhibit current waveform disturbance and stabilize output power, while significantly reducing switching losses compared to full-bridge switching of all arms.

Inventive Principle:

Principle #16Partial or excessive action

2Loss of energy

If the upper arm and lower arm of each leg are switched synchronously, then the reactive power is reduced, but the switching complexity increases

Engineering Contradiction:

Improvereactive powerVSAvoidswitching control complexity

Core Design Contradiction:

Loss of energyVSDevice complexity

Solution Approach 1:

The switching control of upper and lower arms within each leg is merged into a synchronous operation. The upper arm and lower arm of the same leg switch simultaneously, which simplifies the control logic by coordinating their operations. This merged synchronous switching reduces reactive power while the control complexity is managed through unified timing signals for each leg.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The switching-mode changer adjusts the phase of the switching signal based on feedback regarding reactive power output and AC voltage distortion rate. This feedback mechanism optimizes the switching phase to minimize reactive power while maintaining simple synchronous switching control, resolving the contradiction between reactive power reduction and control complexity.

Inventive Principle:

Principle #23Feedback

Data Source

PatentUS10992240B2Power conversion device

Publication Date: 2021.04.27 MITSUBISHI ELECTRIC CORP

AI summary

A power conversion device which reduces switching losses and stabilizes the output power. A switching-mode changer generates a reference signal for switching a mode of operation of the full-bridge circuit to a first switching mode or a second switching mode. In the first switching mode, an upper arm and a lower arm are switched synchronously, and a lower arm and an upper arm are non-conducting. In the second switching mode, the lower arm and the upper arm are switched synchronously, and the upper arm and the lower arm are non-conducting. The switching-mode changer adjusts the phase of the reference signal so that the reactive power is reduced.