Multiport DC Link Protection Using Segmented Fault Switch Units
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Solution Overview
Problem
DC microgrids face challenges with bulky and expensive solid-state circuit breakers due to low short circuit current generation capability, leading to high power losses and bidirectional current flow requirements, which are inefficient and costly.
Innovation Solution
A multiport protection apparatus with a first DC link grid line, protection switch units, and a controller, utilizing half-controllable semiconductor switches and diodes to manage fault events, eliminating the need for full-controllable semiconductor circuit breakers, reducing semiconductor losses, cooling demand, and costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If solid-state circuit breakers are used for protection, then fault protection speed is improved, but device volume and cost increase significantly
Solution Approach 1:
The invention divides the protection function into multiple independent protection switch units, each handling a specific port. This segmentation allows the use of simpler, smaller switches rather than requiring a single large solid-state circuit breaker, thereby reducing overall device volume while maintaining fast protection capability through parallel operation of multiple units
Solution Approach 2:
The invention extracts the bidirectional current control requirement from the protection switches by using separate controllable switches for forward and reverse current paths. This allows the main protection switches to be simpler unidirectional devices, reducing their volume while still achieving comprehensive protection functionality
2Reliability
If solid-state circuit breakers are used for protection, then fault protection capability is improved, but power losses increase
Solution Approach 1:
The invention extracts the bidirectional current control function into separate controllable switches positioned outside the main protection path. This allows the main protection switches to operate in their optimal conduction mode with lower on-resistance, reducing power losses while maintaining full protection capability through the coordinated operation of all switch units
Solution Approach 2:
The invention applies different switch types and control strategies to different current paths based on their specific requirements. Controllable switches are placed where bidirectional control is needed, while simpler switches handle unidirectional protection paths, optimizing the balance between protection capability and power loss for each local function
3Adaptability or versatility
If full-controllable semiconductor switches are used, then bidirectional current control is achieved, but device cost increases
Solution Approach 1:
The invention segments the bidirectional control function into separate controllable switches for forward and reverse paths, allowing the use of less expensive unidirectional protection switches in the main protection circuit. This segmentation achieves the required adaptability while reducing overall device cost by using cheaper components where full controllability is not necessary
4Reliability
If solid-state circuit breakers are used, then protection reliability is improved, but cooling demand increases
Solution Approach 1:
The invention divides the power dissipation and heat generation into multiple separate protection switch units, each with its own thermal management requirements. This segmentation allows for more efficient heat distribution and dissipation across multiple smaller thermal zones, reducing the overall cooling demand compared to a single large solid-state circuit breaker while maintaining protection reliability
Data Source
AI summary
Some embodiments relate to a multiport protection apparatus comprises a first DC link grid line, a plurality of protection switch units, each protection switch unit having a control input, a plurality of ports and a controller which is coupled on its output side to the control inputs of the plurality of protection switch units. Each protection switch unit of the plurality of protection switch units couples a port of the plurality of ports to the first DC link grid line.