Parallel Partial Inverter Topology for Isolated Star-Point Output
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Solution Overview
Problem
Existing converters lack the ability to efficiently generate both direct and alternating voltages of any frequency without a common DC link voltage and struggle with galvanic isolation between three-phase connections and star point connections.
Innovation Solution
A converter design featuring multiple sub-converters connected in parallel, each with three-phase feed and output connections and a star point connection, utilizing transformers for galvanic isolation and allowing for the generation of direct or alternating voltages by controlling the star point connections, eliminating the need for a common DC link voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple partial converters are connected in parallel without a common DC link voltage, then operational flexibility and efficiency are enhanced, but galvanic isolation between three-phase connections and star point connections becomes problematic
Solution Approach 1:
The converter system is divided into multiple independent partial converters, each with its own DC link voltage and control system. This segmentation allows each partial converter to operate independently with different DC link voltages, enhancing operational flexibility while maintaining galvanic isolation through separate transformer circuits for each partial converter.
Solution Approach 2:
Transformers are introduced as intermediary elements between the three-phase connections and star point connections of each partial converter. These transformers provide galvanic isolation, allowing different reference potentials to be established for three-phase connections while maintaining electrical isolation, thus solving the isolation problem in parallel-connected partial converters.
2Reliability
If transformers are added to each submodule for galvanic isolation, then isolation between three-phase connections and star point connections is achieved, but device complexity increases
Solution Approach 1:
The transformer is divided into separate primary and secondary windings, with the primary winding connected to three-phase connections and the secondary winding connected to star point connections. This segmentation provides galvanic isolation while keeping the transformer structure manageable and modular, reducing overall system complexity.
Solution Approach 2:
The transformer serves multiple functions: providing galvanic isolation, enabling different reference potentials, and facilitating power transfer between three-phase and star point connections. This multi-functionality reduces the need for additional isolation components, thereby managing device complexity while achieving reliable isolation.
3Adaptability or versatility
If partial converters operate without a common DC link voltage, then operational flexibility is improved, but control complexity increases
Solution Approach 1:
Each partial converter is equipped with independent control systems that monitor their own DC link voltages and operating conditions. Feedback mechanisms allow each partial converter to autonomously adjust its operation, simplifying control despite the absence of a common DC link voltage, while maintaining overall system coordination.
Solution Approach 2:
The control system is designed to pre-coordinate the operation of multiple partial converters with different DC link voltages. By establishing control strategies in advance, the system manages the complexity of operating without a common DC link, allowing flexible voltage and frequency output while maintaining stable parallel operation.
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
Enables the generation of direct or alternating currents and voltages with any desired frequency, providing galvanic isolation and allowing for three-phase current output without a common DC link, enhancing operational flexibility and efficiency.
Implementation Method 1
The transformer can be used, among other things, to achieve galvanic isolation between the sub-converter's own three-phase connections and the sub-converter's own star-point connections
Data Source
Figure 1
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AI summary
The invention relates, amongst other things, to a converter (2) comprising a partial converter (9) which has: partial converter-specific feed three-phase connections (L1', L2', L3') for connection to a feeding electrical three-phase system and also partial converter-specific output three-phase connections (A', B', C') which form a partial converter-specific output three-phase system, and a partial converter-specific star point connection (X) for making contact with a star point of the partial converter-specific output three-phase system. It is provided according to the invention that the converter (2) comprises at least one further partial converter (9) which has partial converter-specific feed three-phase connections (L1', L2', L3'), partial converter-specific output three-phase connections (A', B', C') which form a partial converter-specific output three-phase system, and a partial converter-specific star point connection (Y) for making contact with a star point of the partial converter-specific output three-phase system, the partial converters (9) are connected in parallel with respect to their partial converter-specific feed three-phase connections (L1', L2', L3') and the partial converter-specific feed three-phase connections (L1', L2', L3') which are connected in parallel form converter-specific feed three-phase connections (L1', L2', L3') for connection to the same feeding three-phase system, and the partial converters (9) are connected in parallel with respect to their partial converter-specific output three-phase connections (A', B', C'), wherein the partial converters (9) each have a converter module (10) for each partial converter-specific feed three-phase connection and the converter modules (10) each have two or more submodules (13) which are connected in series at the output end, and a transformer (17).