Matrix Convertor Power Factor Control via Exciting Current

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Solution Overview

Problem

Existing matrix convertors face difficulties in controlling the power factor on the system side, particularly at low rotation speeds of rotating electric machines, where regulating the input power factor angle is insufficient to achieve a lagging power factor due to leading reactive power, making it challenging to maintain optimal power factor control.

Innovation Solution

A matrix convertor system with bidirectional switches and a controller that controls the exciting current flowing to the rotating electric machine, generating power loss as reactive power to cancel leading reactive power, ensuring accurate regulation of the system-side power factor by supplying lagging reactive current, even at low rotation speeds.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If the input power factor angle is regulated in conventional matrix convertors, then the power factor control is simplified, but the control becomes insufficient at low rotation speeds where leading reactive power cannot be compensated

Engineering Contradiction:

Improvepower factor controlVSAvoidpower factor regulation accuracy

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The invention changes the control parameter from input power factor angle to exciting current magnitude. By controlling the magnitude of the exciting current flowing to the rotating electric machine, the system can regulate reactive power output and achieve lagging power factor even at low rotation speeds where angle-based control fails.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The invention introduces exciting current as an intermediary control variable between the power convertor and the rotating electric machine. This intermediary allows indirect control of reactive power flow, enabling the system to compensate for leading reactive power by adjusting exciting current magnitude rather than directly controlling input power factor angle.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Productivity

If conventional power factor control methods are used, then the system operates simply at high speeds, but fails to achieve lagging power factor at low rotation speeds

Engineering Contradiction:

Improvepower factor control effectivenessVSAvoidlow-speed operation capability

Core Design Contradiction:

ProductivityVSAdaptability or versatility

Solution Approach 1:

The invention implements dynamic control adaptation where the control strategy changes based on rotation speed. At high speeds, conventional angle-based control operates, while at low speeds, the system dynamically switches to exciting current magnitude control to maintain lagging power factor, ensuring continuous adaptability across the full operating range.

Inventive Principle:

Principle #15Dynamics

3Use of energy by moving object

If the matrix convertor operates at low rotation speeds, then wind power generation can be captured, but leading reactive power causes power factor degradation

Engineering Contradiction:

Improvewind energy utilizationVSAvoidleading reactive power

Core Design Contradiction:

Use of energy by moving objectVSObject-generated harmful factors

Solution Approach 1:

The invention converts the harmful leading reactive power generated at low rotation speeds into a controllable parameter. By introducing exciting current control, the system transforms the problematic leading reactive power condition into an opportunity to generate lagging reactive power, thereby canceling the leading component and achieving unity or lagging power factor even when capturing wind energy at low speeds.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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

The system effectively regulates the system-side power factor across various rotation speeds, ensuring accurate control and adherence to required power factors, especially in low-speed conditions such as those encountered in wind power generation systems.

Implementation Method 1

controlling a magnitude of the exciting current flowing from the power convertor to the rotating electric machine... generating power loss as reactive power

Methodology Applied

Scientific EffectJoule heating: Joule Heating

Data Source

PatentUS9923456B2Matrix convertor, power generation system, and method for controlling power factor

Publication Date: 2018.03.20 YASKAWA DENKI KK

AI summary

A matrix convertor includes a power convertor and a controller. The power convertor is disposed between a power system and a rotating electric machine, and includes a plurality of bidirectional switches. The controller is configured to control an exciting current flowing from the power convertor to the rotating electric machine so as to control a power factor on a side of the power system.