Cycloconverter Branch Energy Equalization Control

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Solution Overview

Problem

Existing cycloconverters, particularly those in hexverter designs, face challenges in efficient long-term operation due to uneven energy distribution across converter branches, leading to potential overvoltages and component damage, and require additional hardware for energy balancing.

Innovation Solution

A method for controlling a cycloconverter with six series-connected converter branches, including energy storage elements, that regulates energy transfer between three-line networks based on demand, equalizes energy content across branches, and controls reactive power to prevent overvoltages and ensure continuous operation without additional hardware.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional cycloconverter control methods are used, then the converter can operate, but energy distribution becomes uneven across converter branches leading to overvoltages and component damage

Engineering Contradiction:
Improvelong-term operation reliabilityVSAvoidenergy imbalance and overvoltages
Core Design Contradiction:
ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The control method continuously monitors the energy content in each converter branch and uses feedback signals to adjust the switching states of bridge modules. This closed-loop control equalizes energy distribution across branches, preventing overvoltages and ensuring reliable long-term operation without additional hardware components.

Inventive Principle:
Principle #23Feedback

2Object-affected harmful factors

If additional hardware is added to balance energy distribution, then energy equalization can be achieved, but hardware complexity and costs increase

Engineering Contradiction:
Improveenergy distribution uniformityVSAvoidhardware requirements
Core Design Contradiction:
Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The cycloconverter uses its existing bridge modules and control circuitry to automatically equalize energy distribution among converter branches. The system serves itself by redistributing energy through controlled switching operations, eliminating the need for external balancing hardware or additional components.

Inventive Principle:
Principle #25Self-service

3Adaptability or versatility

If energy stores are allowed to deplete or overfill, then operational flexibility is maintained, but component safety is compromised

Engineering Contradiction:
Improveoperational flexibilityVSAvoidcomponent safety
Core Design Contradiction:
Adaptability or versatilityVSObject-affected harmful factors

Solution Approach 1:

The control method proactively monitors and adjusts energy content in converter branches before depletion or overfilling can occur. By taking preliminary corrective action through coordinated switching of bridge modules, the system maintains energy levels within safe operating ranges, preventing component damage while preserving operational flexibility.

Inventive Principle:
Principle #10Preliminary action

Data Source

PatentEP2710722B1Method for controlling a ac-ac converter, control device and computer program
Publication Date: 2017.09.13 SIEMENS AG
  • EP2710722B1 patent drawingFigure 1
  • EP2710722B1 patent drawingFigure 2
  • EP2710722B1 patent drawingFigure 3

AI summary

The invention relates to a method for controlling a cycloconverter (20), which is designed to a connect a first three-line network (30) to a second three-line network (31), wherein the cycloconverter (20) has six converter branches (32, 33, 34, 35, 36, 37) connected in series, in which converter branches electrical energy stores (9, 11) are provided, wherein the method comprises a method for converter operation control (41), by means of which the energy transfer from the first three-line network (30) into the second three-line network (31) or vice versa is controlled according to energy demand criteria, energy supply criteria, and/or reactive power criteria, wherein the method comprises a method for energy content control (42), by means of which the amount of electrical energy stored in each converter branch (32, 33, 34, 35, 36, 37) or an electrical variable that characterizes the amount of electrical energy is controlled to a specified target range. The cycloconverter has six converter branches connected in series, and said converter branches have energy stores. The invention further relates to an electronic control device for such a cycloconverter, to a cycloconverter, and to computer programs.