Inverter Control Device Stabilizing DC Voltage During Power Failures

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Solution Overview

Problem

Conventional inverters with diode-based rectification units struggle to maintain stable DC terminal voltage during voltage drops or power failures, leading to discontinuous operation and prolonged restart times.

Innovation Solution

An inverter control device and method that estimates motor rotation speed, determines slip frequency, and adjusts frequency references to maintain DC terminal voltage by converting mechanical energy into electrical energy during power failures, using a control unit, speed estimation unit, and slip frequency generation unit to ensure continuous operation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a diode-based rectification unit is used in the inverter, then the structure is simple and cost-effective, but the DC terminal voltage cannot be stably maintained during voltage drops or power failures

Engineering Contradiction:

ImproveDC terminal voltage stabilityVSAvoidrectification unit structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent applies active rectification instead of passive diode rectification, inverting the conventional approach by using controllable switches (IGBTs) that can be actively controlled to achieve bidirectional power flow and stable DC terminal voltage maintenance during voltage drops or power failures

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The patent changes the operational parameters of the rectification unit by implementing active control of switching elements, enabling dynamic adjustment of rectification characteristics to maintain DC terminal voltage stability under varying grid conditions

Inventive Principle:

Principle #35Parameter changes

2Duration of action of moving object

If passive diode rectification is used, then the device complexity is low, but the inverter cannot operate continuously during power failures requiring considerable restart time

Engineering Contradiction:

Improvecontinuous operation timeVSAvoidcontrol system complexity

Core Design Contradiction:

Duration of action of moving objectVSDevice complexity

Solution Approach 1:

The patent enables continuous operation during grid failures by implementing active rectification with controlled switching elements that can maintain power flow and DC terminal voltage even when grid power is unavailable, eliminating the need for restart periods

Inventive Principle:

Principle #20Continuity of useful action

Solution Approach 2:

The inverter system uses its own controlled switching elements to maintain operation during grid failures, making the system self-sufficient by utilizing stored energy in the DC link capacitor and actively managing power flow without external intervention

Inventive Principle:

Principle #25Self-service

3Reliability

If active rectification with controlled switching elements is used, then the DC terminal voltage can be stably maintained, but the device complexity and control difficulty increase

Engineering Contradiction:

Improveinverter operation reliabilityVSAvoidcontrol difficulty

Core Design Contradiction:

ReliabilityVSEase of operation

Solution Approach 1:

The patent implements feedback control mechanisms where the control unit continuously monitors DC terminal voltage and adjusts the switching elements accordingly, using voltage detection signals to maintain stable operation during grid failures

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent replaces passive mechanical diode rectification with active electronic control using switching elements and control circuits, substituting simple passive components with controllable electronic systems that provide superior voltage stabilization

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

Enables continuous inverter operation by stabilizing DC terminal voltage through kinetic energy conversion during power failures, reducing downtime and maintaining power supply stability.

Implementation Method 1

converts mechanical energy into electrical energy during power failures

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Data Source

PatentUS11711028B2Inverter control device and method

Publication Date: 2023.07.25 LS ELECTRIC CO LTD

AI summary

Disclosed are an inverter control device and method. The method according to an embodiment of the present includes estimating a rotation speed of a motor, determining a slip frequency reference using an energy of a direct current terminal capacitor of an inverter, which provides an output voltage to the motor, and a direct current terminal energy reference when a direct current terminal voltage of the inverter is a certain level or less, and providing a frequency reference determined by adding the rotation speed of the motor and the slip frequency reference to the inverter.