Power Conversion Apparatus Pulsation Compensation Control

Solution Overview

Problem

Conventional power conversion apparatuses experience accelerated aging of smoothing capacitors due to large pulsating currents, leading to increased size and cost, as methods to reduce ripple changes in capacitor voltage are costly and inefficient.

Innovation Solution

A power conversion apparatus with a rectifying unit, capacitor, inverter, and control unit that performs pulsation compensation control to reduce the pulsatile component of the capacitor current, using detection values to manage capacitor charge and discharge currents, thereby minimizing capacitor deterioration without increasing apparatus size.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the capacitance of the smoothing capacitor is increased to reduce ripple change in capacitor voltage, then the capacitor deterioration is reduced, but the cost and size of the apparatus increase

Engineering Contradiction:

Improvecapacitor durabilityVSAvoidapparatus size

Core Design Contradiction:

ReliabilityVSWeight of stationary object

Solution Approach 1:

The invention changes the operating parameters of the inverter to reduce capacitor current pulsation. Specifically, it adjusts the switching timing of the inverter switches and controls the injection timing of reactive power to minimize the pulsating current component flowing through the smoothing capacitor, thereby reducing capacitor stress without increasing capacitance value

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The invention implements feedback control by detecting the capacitor current and using this information to adjust the inverter's switching pattern. The control unit monitors the capacitor current pulsation and dynamically modifies the inverter operation to maintain minimal pulsation, ensuring optimal capacitor protection under varying operating conditions

Inventive Principle:

Principle #23Feedback

2Reliability

If the capacitance of the smoothing capacitor is increased to reduce ripple change in capacitor voltage, then the capacitor deterioration is reduced, but the cost increases

Engineering Contradiction:

Improvecapacitor durabilityVSAvoidapparatus cost

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The invention changes the operating parameters of the inverter to reduce capacitor current pulsation. Specifically, it adjusts the switching timing of the inverter switches and controls the injection timing of reactive power to minimize the pulsating current component flowing through the smoothing capacitor, thereby reducing capacitor stress without increasing capacitance value

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The invention implements feedback control by detecting the capacitor current and using this information to adjust the inverter's switching pattern. The control unit monitors the capacitor current pulsation and dynamically modifies the inverter operation to maintain minimal pulsation, ensuring optimal capacitor protection under varying operating conditions

Inventive Principle:

Principle #23Feedback

3Ease of operation

If a large pulsating current flows through the smoothing capacitor, then the inverter can operate with standard switching patterns, but the capacitor aged deterioration is accelerated

Engineering Contradiction:

Improveinverter operation simplicityVSAvoidcapacitor durability

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The invention changes the operating parameters of the inverter to reduce capacitor current pulsation. Specifically, it adjusts the switching timing of the inverter switches and controls the injection timing of reactive power to minimize the pulsating current component flowing through the smoothing capacitor, thereby reducing capacitor stress without increasing capacitance value

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The invention implements feedback control by detecting the capacitor current and using this information to adjust the inverter's switching pattern. The control unit monitors the capacitor current pulsation and dynamically modifies the inverter operation to maintain minimal pulsation, ensuring optimal capacitor protection under varying operating conditions

Inventive Principle:

Principle #23Feedback

Data Source

PatentUS20250219560A1Power conversion apparatus, motor drive apparatus, and refrigeration cycle application device

Publication Date: 2025.07.03 MITSUBISHI ELECTRIC CORP

AI summary

A power conversion apparatus includes: a rectifying unit that rectifies a power-supply voltage applied from a commercial power supply; a capacitor connected to an output end of the rectifying unit; an inverter that converts DC power output from the capacitor into AC power and outputs the AC power to a device on which a motor is mounted; a voltage detecting unit that detects the power-supply voltage; and a control unit that performs pulsation compensation control of reducing a pulsatile component of a capacitor current that is a charge and discharge current of the capacitor on the basis of a detection value by the voltage detecting unit.