Three-Level Converter Switching Branch Control for Safe Shutdown
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Solution Overview
Problem
Existing methods for controlling a three-level converter to enter a stop state often result in delays due to phase-specific fault detection, which can cause damage to the converter equipment.
Innovation Solution
A method and apparatus for controlling a switching branch of a three-level converter to enter a stop state by determining the state of controllable semiconductor switches and implementing specific switching sequences based on their states, allowing for simultaneous or delayed turn-off operations to manage current transfer to diodes, thereby avoiding phase-specific fault detection and reducing response time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If phase-specific fault detection is performed to determine fault current path, then fault handling accuracy is improved, but response time deteriorates causing delay in converter shutdown
Solution Approach 1:
The invention extracts the fault detection function from the normal control system by implementing a dedicated monitoring mechanism that continuously tracks switch states and current paths. This separate detection system immediately identifies faults without waiting for phase-specific analysis, thereby improving response time while maintaining accurate fault path determination through dedicated monitoring circuitry.
Solution Approach 2:
The patent implements preliminary monitoring of switch states and current paths during normal operation. By continuously tracking the operational status of all switches and diodes before a fault occurs, the system is already prepared to immediately identify the fault current path when a fault happens, eliminating the need for post-fault analysis and reducing response time.
2Speed
If all semiconductor switches are turned OFF simultaneously to stop converter operation, then shutdown speed is improved, but risk of high voltage peaks and equipment damage worsens
Solution Approach 1:
Before turning off the semiconductor switches, the invention preliminarily activates the corresponding diodes by controlling their associated switches. This preliminary action ensures that the diodes are ready to immediately conduct the current when the semiconductor switches are turned off, providing a safe current path and preventing high voltage peaks while maintaining fast shutdown speed.
Solution Approach 2:
The patent implements a cushioning mechanism by pre-positioning the diodes in a state ready to conduct current. By controlling the switches associated with the diodes before the main shutdown event, the system creates a protective current path that cushions against the harmful effects of sudden current interruption, preventing voltage spikes and equipment damage during fast shutdown.
Data Source
AI summary
Exemplary embodiments are directed to a method for controlling a switching branch of a three-level converter to enter a stop state. The switching branch including a first semiconductor switch and a second semiconductor switch, a first diode and a second diode, a third semiconductor switch and a fourth semiconductor switch, a third diode, and a fourth diode, a fifth semiconductor switch and a sixth semiconductor switch, a fifth diode, and a sixth diode, and a manner of controlling the semiconductor switches. When the switching branch is set to enter a stop state, current flowing in a main circuit of the switching branch is transferred in a controlled manner to diodes that conduct the current, when all the semiconductor switches of the main circuit of the converter are turned OFF.