Cyclo-Converter Transformer Winding Configuration
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Solution Overview
Problem
Resonant power converter circuits face complexity and cost issues due to the lack of commercially available bidirectional switches, requiring high-speed midpoint drive and complex isolation in existing DC-AC conversion systems.
Innovation Solution
The implementation of a transformer with multiple secondary windings and switch pairs in a cyclo-converter configuration, where each switch pair is coupled between different AC lines, eliminating the need for high dV/dt isolation and simplifying the drive circuit by connecting switches to a 'quiet' signal like a neutral line.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If bidirectional switches are used in the resonant converter circuit, then the power conversion function is achieved, but the device complexity and cost increase due to high dV/dt isolation requirements and drive circuit complexity
Solution Approach 1:
The bidirectional switch is segmented into two unidirectional switches connected in antiparallel configuration. Each unidirectional switch handles one direction of current flow, eliminating the need for complex bidirectional switch isolation. The drive circuits are also segmented and referenced to different potential points (midpoint and neutral point), allowing independent design without high dV/dt isolation requirements between them.
Solution Approach 2:
A midpoint potential is introduced as an intermediary reference point between the primary and secondary sides of the transformer. The drive circuits reference their switching signals to this midpoint rather than requiring direct isolation from opposite sides. This intermediary reference simplifies the isolation requirements and reduces drive circuit complexity.
2Reliability
If bidirectional switches are implemented with back-to-back unidirectional switches, then the power conversion function is achieved, but the drive circuit requires high isolation voltage supplies and fiber optic connections
Solution Approach 1:
The isolation requirement is segmented into two separate, lower-voltage isolation paths. One drive circuit references the midpoint potential and the other references the neutral point. Each isolation transformer only needs to handle the voltage difference to its respective reference point, which is significantly lower than the full dV/dt across the transformer. This segmentation eliminates the need for high-voltage fiber optic connections.
Solution Approach 2:
The reference potential for the drive circuits is changed from a fixed high-voltage reference to dynamic references (midpoint and neutral point) that move with the operating conditions. This parameter change allows the isolation requirements to adapt to the actual voltage stresses, reducing the peak isolation voltage requirements and eliminating the need for oversized isolation components.
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 drive circuit complexity and cost by eliminating high dV/dt issues, enabling efficient DC-AC or AC-DC conversion with commercially available unidirectional switches.
Implementation Method 1
A transformer 106 couples the two sides to one another—a primary winding 106-P is connected to the DC side and a secondary winding 106-S is connected to the AC side
Implementation Method 2
DC-AC resonant power converter 100 comprises a bridge circuit 102 and resonant circuit 104 on the 'DC side' 120
Data Source
AI summary
An apparatus and system for power conversion. In one embodiment, the apparatus comprises a transformer having a primary winding and a plurality of secondary windings; and a cyclo-converter comprising a plurality of switch pairs for converting an alternating current to an AC current, wherein each switch pair in the plurality of switch pairs (i) is coupled between two lines of an AC output and (ii) has a different secondary winding of the plurality of secondary windings coupled between its switches.