Method and system for quickly turning off bidirectional thyristor

Abstract

The invention relates to the technical field of power electronics, and provides a method and system for quickly turning off a bidirectional thyristor. The system comprises a three-phase power grid, a bidirectional thyristor, a resistance-inductance load, a three-level converter, a capacitor energy storage unit, an LC filtering unit, a voltage and current sampling unit, and a CPU control unit. The positive input end of the three-phase power grid voltage is connected to one end of each of the three groups of bidirectional thyristors abc, and the other end of each of the three groups of bidirectional thyristors abc is connected with a load and the output end of the three-level inverter; power grid voltage, thyristor current and inverter output voltage samples are input into the CPU through the voltage transformer, the current transformer and the sampling conditioning circuit, the phase of the thyristor current is determined through calculation, and natural turn-off or reverse voltage turn-off is determined according to the phase. According to the invention, a method of combining natural turn-off and reverse voltage turn-off is adopted, the problem of overcurrent caused by voltage inversion due to positive and negative judgment errors of current in a conventional method is solved, and rapid and accurate turn-off of the bidirectional thyristor can be realized.

Description

technical field [0001] The invention relates to the technical field of power electronics, in particular to a method and system for quickly turning off a bidirectional thyristor. Background technique [0002] With the popularization of power electronic equipment, various interference and pollution sources are also increasing, and power quality problems will become more and more complicated. The power provided by the power supply company to users has problems such as voltage amplitude, frequency deviation, voltage unbalance, transient, fluctuation, interruption, undervoltage and overvoltage, harmonics, etc., which will cause interference and damage to power user loads. The decline of power quality not only affects the normal and safe power supply of the power supply system, but also causes damage to electrical equipment, and even endangers personal safety and leads to major economic losses in severe cases. Correspondingly, many power quality control devices have appeared, suc...

AI Technical Summary

Problems solved by technology

The existing method is to turn off the thyristor by judging the current direction of the thyristor and controlling the voltage of the inverter to be applied to the other end of the thyristor to make it withstand back pressure. However, when the current is near the zero crossing point, it is difficult to detect the actual current direction. , at the same time, because of the delay of the inverter action, the voltage direction is easily reversed, which produces the opposite effect, so that a current spike appears on the thyristor

While damaging the thyristor, the effect of fast shutdown cannot be achieved

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