Three-Phase Converter Current Clamping With Zero-Vector Control

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Solution Overview

Problem

Existing three-phase power converters face challenges in controlling output current, leading to potential damage from overcurrent and limited operational flexibility due to sudden transient changes in motor loads, which results in increased motor vibration and energy recharging back to the DC side.

Innovation Solution

A method involving current clamping control using zero vectors to manage output current, where the power converter switches are controlled by first and second zero vectors based on the carrier signal's peak and valley values, preventing immediate overcurrent protection and reducing switching losses.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If traditional overcurrent protection mechanism is used, then component damage from overcurrent is prevented, but operational flexibility is limited due to sudden transient changes

Engineering Contradiction:

Improvecomponent protectionVSAvoidoperational flexibility

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The current protection mechanism is segmented into two distinct levels: a first current threshold for normal operational monitoring and a second current threshold for critical overcurrent protection. This segmentation allows the system to distinguish between transient current fluctuations and genuine overcurrent conditions, maintaining operational flexibility while ensuring component protection.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The control method dynamically adjusts the response to current variations by implementing a two-stage threshold system. When current exceeds the first threshold but remains below the second threshold, the system applies current clamping control rather than immediate protection shutdown, allowing dynamic adaptation to transient changes while maintaining reliability.

Inventive Principle:

Principle #15Dynamics

2Reliability

If immediate overcurrent protection is activated, then component safety is ensured, but motor vibration increases due to sudden control changes

Engineering Contradiction:

Improvecomponent safetyVSAvoidmotor vibration

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The system implements beforehand cushioning by establishing a buffer zone between the first current threshold and the second current threshold. When current exceeds the first threshold, the system applies gentle current clamping control rather than immediate protective shutdown, cushioning the transition and avoiding sudden control changes that would cause motor vibration.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

Solution Approach 2:

The method allows transient current fluctuations to skip through the first threshold without triggering immediate protection, rushing through the transient phase smoothly. Only when current persists above the second threshold does the system activate overcurrent protection, avoiding unnecessary interruptions and vibration.

Inventive Principle:

Principle #21Skipping (Rushing through)

3Power

If space vector pulse width modulation is used, then output voltage control is achieved, but output current ripples increase under overcurrent conditions

Engineering Contradiction:

Improveoutput voltage controlVSAvoidcurrent ripples

Core Design Contradiction:

PowerVSObject-generated harmful factors

Solution Approach 1:

The system changes the control parameters dynamically by switching between different modulation strategies. Under normal conditions, space vector pulse width modulation is used for precise output voltage control. When current exceeds the first threshold, the system transitions to current clamping control, adjusting the modulation parameters to reduce current ripples while maintaining necessary voltage control.

Inventive Principle:

Principle #35Parameter changes

4Adaptability or versatility

If current clamping control is implemented, then operational range is enhanced, but switching losses occur due to additional switch operations

Engineering Contradiction:

Improveoperational rangeVSAvoidswitching losses

Core Design Contradiction:

Adaptability or versatilityVSLoss of energy

Solution Approach 1:

The system applies partial action by implementing current clamping control only when current exceeds the first threshold but remains below the second threshold. This selective application extends the operational range for handling transient conditions without incurring continuous switching losses during normal operation.

Inventive Principle:

Principle #16Partial or excessive action

Data Source

PatentUS12051982B2Method of clamping output current of three-phase power converter

Publication Date: 2024.07.30 DELTA ELECTRONICS INC(CN)

AI summary

A method of clamping an output current of a three-phase power converter is provided. The three-phase power converter includes three switching bridge arms and provides a three-phase output voltage command, and each switching bridge arm has an upper switch and a lower switch connected in series. The method includes steps of: determining that the output current is greater than a first current threshold to activate a current clamping control procedure, comparing a carrier signal with the three-phase output voltage command to turn on the lower switches by a first zero vector when the carrier signal is rising and turn on the upper switches by a second zero vector when the carrier signal is falling, determining that the output current is greater than a second current threshold to activate an overcurrent protection procedure, wherein the second current threshold is greater than the first current threshold.