Three-Phase to Single-Phase Converter with Merged DC Circuit
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing electrical circuits for converting between three-phase and single-phase power grids require significant effort and complexity, particularly on the single-phase power supply side, due to the need for multiple transformers and converters to manage pulsating power and harmonics.
Innovation Solution
The electrical circuit employs a configuration with first partial converters having three phase modules and second partial converters having two phase modules, each designed as a 3-level NPC converter, connected through a DC intermediate circuit and absorption circuit, reducing the number of components and complexity by using a star configuration of transformers and series connections of partial converters to manage power conversion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple transformers and converters are used to manage pulsating power and harmonics in the single-phase power supply side, then power conversion reliability is improved, but device complexity increases
Solution Approach 1:
The patent combines multiple partial converters (first and second partial converters) into a unified converter structure that shares a common DC intermediate circuit. This merging approach maintains the functional capability to manage pulsating power and harmonics while reducing the number of separate transformer and converter units needed, thereby decreasing overall device complexity while preserving power conversion reliability
Solution Approach 2:
The DC intermediate circuit serves multiple functions simultaneously: it acts as a voltage stabilization element, an energy storage element for managing pulsating power, and a common connection point for multiple partial converters. This multi-functionality eliminates the need for separate absorption circuits for each converter, reducing device complexity while maintaining reliable power conversion
2Stability of the object's composition
If an absorption circuit is added to the single-phase power supply side to absorb pulsating power, then power conversion stability is improved, but device complexity increases
Solution Approach 1:
The DC intermediate circuit is designed to perform both voltage stabilization and pulsating power absorption functions. By making the DC intermediate circuit multi-functional, the patent eliminates the need for a separate absorption circuit, thereby maintaining power conversion stability while avoiding the increase in device complexity that would result from adding another component
Solution Approach 2:
The absorption function is merged into the DC intermediate circuit rather than being implemented as a separate absorption circuit. This consolidation maintains the stability benefit of having pulsating power absorption capability while reducing the overall number of components in the system
3Power
If a full-bridge converter configuration is used for single-phase power conversion, then power conversion capability is improved, but device complexity and component count increase
Solution Approach 1:
The converter is segmented into multiple partial converters (first and second partial converters) with different numbers of phase modules. This segmentation allows the system to achieve the required power conversion capability through the combined output of multiple simpler converter units rather than using a single complex full-bridge converter, thereby reducing overall device complexity while maintaining power capability
Solution Approach 2:
Different partial converters are assigned different numbers of phase modules based on their specific functional requirements. The first partial converters have three phase modules while the second partial converters have two phase modules. This local differentiation optimizes the power conversion capability in each section while avoiding the uniform complexity of a complete full-bridge configuration throughout the entire 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
This configuration reduces the effort and complexity on the single-phase power supply side by efficiently managing power conversion between three-phase and single-phase grids, minimizing the need for additional absorption circuits and allowing for flexible transformer designs, thereby enhancing efficiency and adaptability.
Implementation Method 1
a three-phase power grid 11 is connected via a transformer 12 to a converter 13
Implementation Method 2
The absorption circuit 19 is usually tuned to twice the rated frequency of the single-phase power grid 15 and absorbs the pulsating power of the single-phase power grid 15
Data Source
Figure 1~2b
Figure 2a
Figure 3
AI summary
The circuit has a transformer (24) connected with a three-phase power network (21) i.e. three-phase public power grid. A set of partial converters (25) is assigned to the transformer, direct-current (DC) intermediate circuits (26) and associated a set of partial converters (28). The latter set of partial converters is connected at alternating current-side outputs over a series connection (29). Another transformer is assigned and connected to the latter set of partial converters through the series connection, and a single-phase power network (22) i.e. single-phase railroad grid.