Modular Multi-Pulse Transformer Rectifier Harmonic Cancellation
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Solution Overview
Problem
Multi-level power converters, particularly series H-bridge inverters, require numerous isolated DC voltage sources, leading to harmonic current components in supply currents that cause electromagnetic interference and are difficult to optimize due to manufacturing limitations and limited phase shift angles in single-stage transformers.
Innovation Solution
A medium voltage drive system utilizing modular transformers with phase-shifted primary and secondary windings, allowing for optimized harmonics cancellation and scalability, where each transformer provides output to multiple power cells across different phase output lines, and optionally including non-phase-shifted transformers for partial regeneration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single-stage transformer with multiple phase-shifted secondary windings is used, then the number of isolated DC voltage sources is reduced, but harmonics cancellation cannot be optimized due to manufacturing limitations and limited phase shift angles
Solution Approach 1:
The patent divides a single-stage transformer into multiple modular transformers, each with fewer secondary windings. This segmentation allows each module to be manufactured with standard phase shift angles (e.g., 30 degrees) while achieving the same effective harmonics cancellation as a complex single-stage transformer would require. The modular approach trades structural complexity for manufacturing feasibility.
2Object-generated harmful factors
If multiple modular transformers with phase-shifted windings are used, then harmonics cancellation is optimized, but the device complexity and number of transformers increases
Solution Approach 1:
The patent systematically varies the phase shift angles of primary and secondary windings across multiple modular transformers to achieve optimized harmonics cancellation. By changing the phase shift parameters (e.g., 0°, 30°, 60°, 90°) in a structured manner, the system achieves superior harmonic filtering compared to conventional single-stage transformers, while keeping each individual transformer module relatively simple.
3Reliability
If series H-bridge inverters are used to achieve multi-level power conversion, then power quality and voltage capability are improved, but the number of isolated DC voltage sources and transformers required increases
Solution Approach 1:
Each modular transformer in the patent is designed with multiple secondary windings that can supply multiple power cells, making the transformer multi-functional. A single transformer module can serve several H-bridge inverters, reducing the total number of transformers needed while maintaining the multi-level power conversion capability and associated power quality benefits.
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 system achieves high power quality, reduced harmonic distortion, and improved reliability by eliminating troublesome harmonics and allowing for modular design and manufacturing, meeting IEEE 519 standards for harmonic levels and enabling continued operation even with transformer failures.
Implementation Method 1
Each transformer may have at least one primary winding and multiple secondary windings, where the primary winding of each transformer is phase shifted with respect to its neighboring transformers and the secondary windings are also phase shifted
Data Source
AI summary
In one embodiment, a system may include multiple transformers each to provide an output to one or more power cells, where the power cells provide AC power to a load. Each transformer may have at least one primary winding and multiple secondary windings, where the primary winding of each transformer is phase shifted with respect to its neighboring transformers and the secondary windings are also phase shifted. The phase shift of the primary winding can be based on the phase shift of the secondary windings and a number of the plurality of transformers.