Multi-Port PMSG Grid Interface With Hybrid Rectifiers for Lower Loss
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Solution Overview
Problem
Existing offshore wind energy systems face challenges in efficiently interfacing permanent magnet synchronous generators (PMSGs) with medium-voltage dc (MVDC) or high-voltage dc (HVDC) grids due to high conduction and switching losses, high VA ratings, and complex converter topologies that increase costs and complexity.
Innovation Solution
An integrated generator-rectifier system with passive and active rectifiers connected to a multi-port PMSG, using a fixed-duty ratio converter and an isolated dc-dc converter to minimize switch VA ratings and reduce losses, along with a control strategy for maximum power point tracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If additional dc-dc converters with inversely proportional relationship between converter gain and wind speed are used to regulate dc output, then dc voltage regulation is achieved, but switch volt-ampere ratings and conduction losses increase
Solution Approach 1:
The patent segments the rectification function into multiple independent single-phase rectifier bridges, each handling a portion of the total power. This allows each converter to operate at lower voltage and current ratings, reducing conduction losses and switch VA ratings while maintaining the ability to regulate DC output voltage through coordinated control of multiple modules.
Solution Approach 2:
The patent implements dynamic control where the converter gain is adjusted based on wind speed conditions. The control system dynamically modifies the firing angles and switching patterns of the rectifier bridges to optimize performance across varying operating conditions, achieving voltage regulation without requiring oversized converters designed for maximum power conditions.
2Loss of energy
If high voltage and current rated semiconductor devices are used to regulate dc output, then voltage regulation capability is improved, but switch volt-ampere ratings and conduction losses increase
Solution Approach 1:
The system divides the power conversion function across multiple lower-rated semiconductor devices rather than using a single high-rated device. Each rectifier bridge uses standard voltage and current rated switches, and the combined output of multiple bridges achieves the required voltage regulation capability without requiring oversized individual components.
Solution Approach 2:
The patent combines the outputs of multiple single-phase rectifier bridges in parallel to achieve the equivalent performance of a three-phase system. By merging the contributions of multiple lower-rated converters, the system achieves high voltage regulation capability and power handling capacity using standard-rated semiconductor devices.
3Loss of energy
If neutral-point-clamped and flying-capacitor-based converters are used for medium-voltage applications, then multilevel voltage output is achieved, but conduction and switching losses increase due to additional clamping diodes
Solution Approach 1:
The patent extracts the voltage multiplication function from complex multilevel converter topologies and implements it through series connection of multiple single-phase rectifier bridges. This eliminates the need for clamping diodes, flying capacitors, and neutral-point-clamping circuits, significantly reducing switching losses and topology complexity while achieving the same voltage level boosting effect.
Solution Approach 2:
Instead of using a single complex multilevel converter that requires numerous clamping elements, the patent inverts the approach by using multiple simple single-phase bridges connected in series. This alternative configuration achieves multilevel voltage output through a different architectural paradigm that inherently requires fewer loss-generating components.
4Loss of energy
If reduced-switch multilevel rectifiers are used for MV generators, then converter component count is reduced, but full power processing increases cost and conversion losses
Solution Approach 1:
The patent segments the power processing function across multiple independent single-phase rectifier bridges, each handling a fraction of the total power. This segmentation allows each module to operate more efficiently at lower power levels and enables modular scaling, reducing overall conversion losses while maintaining manageable complexity through standardized repeating units.
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 a 22.8% reduction in total switch VA rating and 28.3-71.7% reduction in conversion losses, enhancing efficiency, power density, and reliability while providing a cost-effective interface to dc grids.
Implementation Method 1
A preferred embodiment provides a generator-rectifier system and grid interface coupled to a wind turbine driven permanent magnet synchronous generator
Implementation Method 2
Passive rectifiers are connected to the others of the plurality of ac ports of the multi-port permanent magnet synchronous generator
Data Source
AI summary
A generator-rectifier system and grid interface includes an active rectifier that accepts an input from an ac port of a multi-port permanent magnet synchronous generator. Passive rectifiers are connected to the others of the plurality of ac ports. Connections provide outputs of the active and passive rectifiers. A first converter operates at a fixed duty ratio driven by the outputs to interface with a dc grid or at a low grid frequency switching waveform to create a grid frequency ac output to interface with an ac grid. A second converter is connected the output of the active rectifier, and is controlled at a variable duty ratio to interface with the dc grid or an above-grid frequency switching waveform to create an above-grid frequency ac waveform to interface with an ac grid. Connections provide a serial stack of outputs of the first and second converters.