Phase-Shift Autotransformer for Multi-Pulse Rectifier Harmonic Reduction
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Solution Overview
Problem
Conventional high power rectifier systems face inefficiencies and increased costs due to large magnetic part requirements, harmonic issues, and power factor degradation, necessitating improved power conversion and harmonic reduction.
Innovation Solution
A phase-shifting autotransformer with a specific magnetic core and wiring configuration that provides a six-phase voltage output, reducing the kVA rating to 9% of the output power, combined with a multi-pulse rectifier system and diode bridge rectifier for enhanced power factor correction and harmonic reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If conventional 12-pulse rectifier systems with star-delta phase shifting transformers are used, then power conversion capability is achieved, but the kVA rating and physical footprint of magnetic components become excessively large
Solution Approach 1:
The invention segments the traditional single large transformer into multiple smaller transformers (e.g., three single-phase transformers or three-legged core transformers) that can be independently configured and connected in parallel. This segmentation allows each transformer to handle a portion of the total power, reducing the volume and weight of individual magnetic components while maintaining the required power conversion capability through parallel operation
Solution Approach 2:
The invention transitions from a single large transformer design to a multi-transformer parallel configuration, adding the dimension of system architecture complexity. By connecting multiple smaller transformers in parallel with specific phase shifting arrangements (e.g., 30-degree phase shifts between transformers), the system achieves the same power conversion function with reduced individual component sizes and improved scalability
2Object-generated harmful factors
If high power Harmonic Blocking Reactors (HBR) are added to non-isolated multi-pulse rectifier systems, then harmonic reduction is achieved, but the total kVA rating and manufacturing complexity increase
Solution Approach 1:
The invention converts the harmful harmonics generated by the rectifier into beneficial phase-shifted current waveforms by strategically configuring the primary windings of multiple transformers. The 30-degree phase shifts between transformers cause the harmonic currents to cancel each other out through vector addition, transforming what would be harmful harmonic distortion into a balanced, low-harmonic output without requiring additional HBR components
Solution Approach 2:
The invention changes the electrical parameters of the transformer system by introducing specific phase shifts (30 degrees) between parallel-connected transformers and configuring the primary winding connections (e.g., wye-delta or delta-wye arrangements). These parameter changes fundamentally alter the harmonic spectrum of the input current, reducing total harmonic distortion to acceptable levels without adding complex harmonic filtering components
3Power
If conventional rectifier configurations are used, then basic power conversion is achieved, but power factor and efficiency are degraded
Solution Approach 1:
The invention performs preliminary phase-shifting of the transformer output voltages before they reach the rectifier stage. By pre-configuring the transformers to output voltages with specific phase relationships (e.g., 30-degree shifts), the system prepares the input waveforms for the rectifier in advance, enabling the rectifier to draw more sinusoidal input currents and achieve higher power factor without requiring complex active power factor correction circuits
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 solution achieves significant reductions in the volume and weight of magnetic components, improves power efficiency, and enhances power quality by minimizing harmonics, making it suitable for high-power applications like electric vehicle charging.
Implementation Method 1
The primary input windings of the wiring configuration and the first, second and third magnetic cores are configured to provide a first primary input inductance, a second primary input inductance, and a third primary input inductance. Phase angle of AC input voltage and current at each phase is shifted by the first primary input inductance, a second primary input inductance, and a third primary input inductance of the primary input windings of the wiring configuration.
Implementation Method 2
Phase-shift windings of the wiring configuration and the first, second and third magnetic cores are configured to provide a first and second inductance for phase-shift windings of the first magnetic core, a third and fourth inductance for phase-shift windings of the second magnetic core, and a fifth and sixth inductance for phase-shift windings of the third magnetic core.
Data Source
AI summary
The present disclosure relates to systems and configurations for phase-shift autotransformers and multi-pulse rectifiers. A phase-shift autotransformer includes a wiring configuration for first, second and third magnetic cores, the wiring configuration including primary input and phase-shift windings. The primary input windings are configured to provide a first and second primary input inductances, and phase-shift windings of the wiring configuration are configured to provide multiple inductances for each phase-shift winding. A multi-pulse rectifier is provided including a phase-shifting autotransformer, a diode bridge rectifier configuration coupled to output of the autotransformer and a filtering capacitor coupled to the diode bridge rectifier. Other embodiments are directed to use of the multi-use rectifier system with vehicle charging station, such as an Electric Vehicle Supply Equipment (EVSE).