Torque control method of pulse commutation stage of static frequency converter

Abstract

The invention discloses a torque control method of the pulse commutation stage of a static frequency converter. The static frequency converter comprises a rectifier bridge and an inverter bridge, wherein the inverter bridge comprises 6 thyristors; a number 1 thyristor and a number 4 thyristor are in one way; the cathode of the number 4 thyristor is connected with the anode of the number 1 thyristor; a number 3 thyristor and a number 6 thyristor are in one way; the cathode of the number 6 thyristor is connected with the anode of the number 3 thyristor; a number 2 thyristor and a number 5 thyristor are in one way; the cathode of the number 2 thyristor is connected with the anode of the number 5 thyristor. The control method comprises the following steps: firstly, detecting the real-time position angle Theta of a rotor, computing the commutation time Delta t in a thyristor pulse commutation stage, then computing the inverter bridge advance conduction angle Gamma in the thyristor pulse commutation stage, and finally triggering the inverter bridge thyristors with a range of 0 to Gamma before the position of the rotor reaches a stator line voltage cross-zero point. The control method can adjust the triggering time of the thyristors, effectively reduce the average value of zero output torque, reduce the fluctuation of the output torque of the static frequency converter, and improve the output torque of the static frequency converter.

Description

technical field [0001] The invention belongs to the technical fields of electromechanical and power electronics, and in particular relates to a torque control method in the pulse commutation stage of a static frequency converter. Background technique [0002] At the initial stage of starting the synchronous motor of the static frequency converter, due to the low machine terminal voltage, the thyristors of the inverter bridge cannot complete the natural commutation, such as figure 1 As shown, at this time, pulse commutation technology needs to be used to complete the commutation, that is, the rectifier bridge is inverted, and the inverter bridge blocks the pulse, forcing the loop current to drop to zero, thereby completing the shutdown and commutation of the thyristors of the inverter bridge. The previous pulse commutation technology mainly completed the triggering of the next pair of thyristors by detecting the zero crossing of the line voltage, such as figure 2 As shown, ...

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Problems solved by technology

[0010] Aiming at the current static frequency converter in the pulse commutation stage, the loop current will appear at a zero current moment with a time of Δt. At this time, the torque output is 0, the motor relies on inertial rotation, and the torque output capacity is small. This case explores and improves

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