Marine Electrical System Phase-Shifting Transformer
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Solution Overview
Problem
Existing electrical systems for marine vessels with medium voltage propulsion face challenges in reducing size and weight while maintaining capacity, particularly due to complex circuitry and voltage balance issues in high voltage operations, and inefficiencies in harmonic cancellation and zero sequence current suppression.
Innovation Solution
The system splits the AC supply into two phases and uses a phase-shifting transformer between the supplies and rectifier circuits, along with a resonant controller and specific inductor and capacitor configurations, to achieve sinusoidal input current waveforms and suppress zero sequence circulation currents, allowing for a lower capacity transformer and reduced switching frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If conventional front-end AC/DC rectifier and rear-end DC/AC inverter are used, then high voltage operation is achieved, but the overall size and weight of the electrical system increases
Solution Approach 1:
The patent combines the front-end AC/DC rectifier and rear-end DC/AC inverter into a single integrated converter unit. The converter simultaneously performs both rectification and inversion functions, eliminating the need for separate transformer and capacitor banks that would otherwise be required, thereby reducing overall system size and weight while maintaining high voltage operation capability
Solution Approach 2:
The converter circuit is designed to perform multiple functions: it acts as both a rectifier (converting AC to DC) and an inverter (converting DC to AC), and can operate in both generating and motoring modes. This multi-functionality eliminates the need for separate dedicated circuits for each function, reducing the overall system footprint and weight
2Power
If multilevel inverters are used for medium voltage propulsion systems, then voltage balance control becomes more challenging, but high voltage operation is enabled
Solution Approach 1:
The patent divides the single complex multilevel inverter into multiple independent H-bridge converter units. Each H-bridge operates independently with its own DC capacitor, eliminating the need for complex voltage balance control across shared capacitors. The segmented architecture maintains high voltage capability while significantly reducing control complexity
Solution Approach 2:
The patent introduces a common DC bus as an intermediary between multiple independent H-bridge converters. This common bus allows each converter to operate independently while still achieving coordinated high voltage output, simplifying the control architecture compared to direct multilevel inverter approaches
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 enhances front-end efficiency, reduces the size and weight of the electrical system, and maintains high voltage operation capabilities, while minimizing stator current ripples and harmonic currents, thus optimizing the electrical drive for marine propulsion.
Implementation Method 1
uses a phase-shifting transformer between the supplies and rectifier circuits, to achieve sinusoidal input current waveforms through harmonic cancellation
Implementation Method 2
along with a resonant controller and specific inductor and capacitor configurations, to achieve sinusoidal input current waveforms and suppress zero sequence circulation currents
Data Source
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AI summary
An electrical system including a first three-phase AC supply and a second three-phase AC supply; a phase-shifting transformer, connected to and receivable of AC power from each of the first three-phase AC supply and the second three-phase AC supply, said phase-shifting transformer applying a 30° phase shift to each of the received AC powers to thereby generate a first transformed AC current and a second transformed AC current; a first rectifier circuit and a second rectifier circuit, each connected to the phase-shifting transformer and receivable of the first transformed AC current and the second transformed AC current respectively, said rectifier circuits generating a first DC voltage and a second DC voltage; a first inverter circuit and a second inverter circuit, respectively connected to the first rectifier circuit and the second rectifier circuit, said inverter circuits generating a first AC output voltage and a second AC output voltage from the first DC voltage and second DC voltage respectively; and a load, connected to and receivable of the first AC output voltage and the second AC output voltage.