Induction Generator Reactive Power Circuit for Lower Converter Capacity

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Solution Overview

Problem

The capacity of converters in two-winding squirrel-cage induction generators is high due to the requirement for high reactive power to supply excitation and leakage magnetic flux, which is more expensive than diode bridges.

Innovation Solution

Incorporating a capacitor connected in parallel to the diode bridge or converter to supply reactive power, reducing the need for a high-capacity converter.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a converter is used to supply reactive power for excitation and leakage magnetic flux in a two-winding squirrel-cage induction generator, then the excitation requirement is met, but the converter capacity becomes excessively high

Engineering Contradiction:
Improveexcitation capabilityVSAvoidconverter capacity
Core Design Contradiction:
ReliabilityVSPower

Solution Approach 1:

The reactive power supply function is segmented from the main converter and assigned to a dedicated capacitor connected to the main winding. This separates the excitation function from the power conversion function, allowing the converter to operate at lower capacity while the capacitor handles reactive power independently

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

A capacitor is introduced as an intermediary component between the power source and the induction generator. This capacitor acts as a reactive power reservoir that supplies excitation current and leakage flux requirements, mediating between the converter and the generator's magnetic field needs

Inventive Principle:
Principle #24Intermediary (Mediator)

2Ease of manufacture

If the converter is connected to the auxiliary winding with lower output power, then cost is reduced compared to connecting to the main winding, but the reactive power requirement relative to auxiliary winding power becomes excessively high

Engineering Contradiction:
Improvesystem costVSAvoidreactive power to active power ratio
Core Design Contradiction:
Ease of manufactureVSUse of energy by moving object

Solution Approach 1:

The capacitor serves multiple functions simultaneously: it provides reactive power for excitation, supplies leakage flux current, and operates independently of the converter's power rating. This multi-functionality allows the system to meet all reactive power needs without sizing the converter for peak reactive power demands

Inventive Principle:
Principle #6Universality (Multi-functionality)

Solution Approach 2:

The invention creates an alternative reactive power supply path through the capacitor that bypasses the converter. This 'copy' of the reactive power function eliminates the need for the converter to handle excessive reactive power, allowing cost-effective connection to the lower-power auxiliary winding

Inventive Principle:
Principle #26Copying

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 capacity of the converter can be made lower by supplying reactive power from the capacitor, thus optimizing the power generation system.

Implementation Method 1

a capacitor that is connected to the primary winding of the induction generator and supplies reactive power to the induction generator

Methodology Applied
Scientific EffectCapacitance: Capacitance

Implementation Method 2

an induction generator having a primary winding including a main winding and an auxiliary winding and a secondary conductor

Methodology Applied
Scientific EffectElectromagnetic induction: Electromagnetic Induction

Data Source

PatentEP4668569A1Power generation system using induction generator
Publication Date: 2025.12.24 HITACHI CONSTRUCTION MACHINERY CO LTD
  • EP4668569A1 patent drawingFigure 1
  • EP4668569A1 patent drawingFigure 2
  • EP4668569A1 patent drawingFigure 3

AI summary

An object of the present invention is to provide a power generation system that can decrease the capacity of a converter that supplies reactive power required for excitation and generation of leakage magnetic flux in a two-winding squirrel-cage induction generator. To this end, in a power generation system including an induction generator having a primary winding including a main winding and an auxiliary winding, and a secondary conductor, a diode bridge that is connected to the main winding and converts AC power generated in the main winding to DC power, and a converter that is connected to the auxiliary winding, excites the induction generator, and converts an AC voltage generated in the auxiliary winding to a DC voltage, a capacitor that is connected to the primary winding of the induction generator and supplies reactive power to the induction generator is included, and the capacitor is connected to the main winding in parallel to the diode bridge.