Series Thyristor Switching with Sequential Gate Triggering
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Solution Overview
Problem
Existing semiconductor switch arrangements face challenges in voltage distribution, control complexity, and overvoltage protection, particularly in high-voltage applications, with existing solutions requiring high-voltage presence for testing and synchronization, and lacking effective overvoltage protection during lightning strikes.
Innovation Solution
A switching device with a thyristor string connected in series, using overvoltage protection devices and driver thyristors with transformers to enable control without high-voltage presence, allowing sequential firing and diagnosis, and incorporating additional components for improved detection and protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If triggering energy is provided by voltage across each semiconductor switch, then the switch can be triggered when voltage is present, but the device cannot be tested and diagnosed without high voltage presence
Solution Approach 1:
The patent introduces a mediator circuit that couples the control electrode of one semiconductor switch to the control electrode of the next switch through a blocking capacitor and diode network. This intermediary mechanism allows triggering signals to propagate through the series-connected switches without requiring high voltage presence, enabling testing and diagnosis while maintaining reliable triggering functionality through the capacitor's ability to block DC voltage while passing AC trigger signals.
2Reliability
If transformers are used for each stage to provide triggering energy from the control circuit, then galvanic insulation is achieved, but the insulation requirement of transformers increases at each level
Solution Approach 1:
The patent merges the triggering functions of multiple semiconductor switches into a single integrated control circuit. Instead of using separate transformers for each stage, the control electrodes of series-connected switches are coupled together through a shared capacitor-diode network, allowing a single control signal to trigger all switches simultaneously while maintaining galvanic insulation through the blocking capacitor, thereby reducing overall device complexity and transformer insulation requirements.
3Reliability
If light-triggered thyristors controlled by optical fibres are used, then galvanic insulation and perfect synchronisation are achieved, but cost increases and availability is limited
Solution Approach 1:
The patent creates a simplified copy of the optical fibre triggering mechanism using electrical components. Instead of using expensive light-triggered thyristors and optical fibres, the invention replicates the galvanic insulation and synchronization effects using blocking capacitors and diodes that couple control electrodes electrically, achieving the same functional outcomes at lower cost and with broader component availability.
4Reliability
If thyristors are arranged in series with parallel resistors and snubbers for voltage balancing, then static and dynamic voltage balancing is achieved, but the topology requires synchronous firing of all stages
Solution Approach 1:
The patent applies preliminary action by pre-charging blocking capacitors connected in parallel with each semiconductor switch before the switching operation. This preliminary charging of capacitors establishes the voltage balancing conditions in advance, eliminating the need for complex synchronous firing mechanisms and allowing the switches to be triggered sequentially or simultaneously without overvoltage stress on any specific stage.
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
Enables simple control and testing of the switching device without high voltage, provides effective overvoltage protection, and allows diagnosis of thyristor string operation, including during lightning strikes, with reduced insulation requirements and compact design options.
Implementation Method 1
a blocking capacitor (41, 42, 43, 44) coupled between the control electrode of one semiconductor switch and the control electrode of the next semiconductor switch
Implementation Method 2
a diode (45, 46, 47, 48) connected in series with the blocking capacitor
Data Source
Figure 1
Figure 2a~2c
Figure 3a~3c
AI summary
The switching device (1) according to the invention comprises (i) a controller (8), (ii) a string (2) of main semiconductor switches (21 to 2N) connected in series, extending from a first main semiconductor switch (21) to a last main semiconductor switch (2N), each main semiconductor switch comprising a control terminal (G), and (iii) driver semiconductor switches (4), each of which is connected between the control terminals (G) of two successive main semiconductor switches of the string (2) so that a control signal coming from the controller (8) and provided at the control terminal (G) of only the first main semiconductor switch (21) puts the first main semiconductor switch (21) into a conducting state and then sequentially puts the other main semiconductor switches (22 to 2N) into a conducting state by sequentially putting the driver semiconductor switches (41 to 4N-1) into a conducting state, independently of whether a voltage is present across the string (2).