Switch Unit with Commutation Bypass for Arc Protection
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Solution Overview
Problem
In power generation systems, especially wind power systems, the existing contact switches face challenges in quickly disconnecting the electric connection between the wind turbine and the converter during system failures, leading to potential damage and reduced reliability due to high voltage and slow response times of dump loads, and the cost of arc extinction devices is high.
Innovation Solution
A switch unit with a bi-directional controllable switch structure connected in parallel to the contact switch, which receives separate control signals to provide a commutation bypass, allowing for safe and efficient disconnection of the electric connection between the power generator and the converter, thereby protecting the contact switch and enhancing system stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a controllable contact switch is used to disconnect the electric connection between the wind turbine and converter during system failures, then the response speed is improved, but the contact switch cannot operate normally or its usage life is reduced due to arc voltage generated by the large equivalent inductance of the wind turbine winding
Solution Approach 1:
A commutation circuit is introduced as an intermediary between the contact switch and the wind turbine winding. This commutation circuit provides a dedicated current path during switch off-state, allowing the inductive current to commutate smoothly without generating harmful arc voltage across the contact switch terminals, thus protecting the contact switch while maintaining fast response capability
Solution Approach 2:
The commutation circuit is pre-configured and ready before the contact switch needs to operate. By having the commutation path prepared in advance, the system can immediately redirect the inductive current when the contact switch opens, preventing arc formation and enabling reliable high-speed disconnection without compromising contact switch longevity
2Reliability
If a special arc extinction device is added to the contact switch to reliably cut off electric connection, then the contact switch reliability is improved, but the cost is significantly increased
Solution Approach 1:
Instead of using expensive arc extinction devices attached to the contact switch, the patent introduces a commutation circuit as an intermediary that fundamentally eliminates the arc problem by providing an alternative current path. This approach achieves reliable contact switch operation at a fraction of the cost of arc extinction equipment
Solution Approach 2:
The commutation circuit uses simple, inexpensive components (resistors, capacitors, diodes) that can be easily manufactured and replaced if needed, replacing the need for costly arc extinction devices. The low-cost commutation components provide the same protective function without the high manufacturing cost
3Object-affected harmful factors
If dump loads are added to reduce voltage at the converter input interface, then the voltage protection is improved, but the voltage limiting capacity and switching response rate are limited
Solution Approach 1:
A commutation circuit with controlled resistance is introduced as an intermediary to manage the inductive energy from the wind turbine winding. This circuit provides immediate voltage clamping protection during switch off-state, preventing overvoltage damage while enabling fast response times that dump loads cannot achieve due to their mechanical switching limitations
Data Source
AI summary
The present disclosure provides a switch unit and a power generation system thereof. The switch unit includes a contact switch having a main contact and a control terminal, where the control terminal receives a first drive signal to turn on the contact switch; and a bi-directional controllable switch structure, which is connected in parallel to two ends of the main contact of the contact switch and receives one or more second drive signals to turn on the switch structure. When the switch unit performs a turn-off operation, the bi-directional controllable switch structure provides a commutation bypass for the contact switch, so as to protect the contact switch.