Four-quadrant current source converter based on autotransformer

Abstract

The invention provides a four-quadrant current source converter based on an autotransformer. The four-quadrant current source converter comprises the autotransformer, an AC power source, an inductor, a first three-phase rectifier bridge, a second three-phase rectifier bridge and a DC harmonic injection circuit, wherein the first three-phase rectifier bridge is connected in parallel with the second three-phase rectifier bridge; and the input end of the autotransformer is connected with the output end of the AC power source via the inductor, the output end of the autotransformer is connected with the input end of the first three-phase rectifier bridge and the input end of the second three-phase rectifier bridge, and the output end of the first three-phase rectifier bridge and the output end of the second three-phase rectifier bridge are connected with the DC harmonic injection circuit. According to the invention, a main topology employs the autotransformer as a base, the DC injection circuit is connected through the two three-phase bridges, through controlling injection currents of a DC circuit, output currents of the autotransformer are modulated, and thus the purpose of inhibiting harmonic waves is realized.

Description

technical field [0001] The invention relates to a current source converter, in particular to a four-quadrant current source converter based on an autotransformer. Background technique [0002] Two three-phase full-bridge converters are connected in parallel or in series through a Δ-Y, Y-Y-connected isolation transformer. The traditional 12-pulse converter can reduce harmonics to a certain extent, but the rated capacity of the rectifier transformer is higher than the output The capacity is high, so the isolation transformer is replaced by an autotransformer to reduce the winding capacity of the transformer. In addition, a large number of PWM technology is used in the commutation circuit to effectively adjust the output voltage, so that the output current is close to a sine wave, but its disadvantages are high cost, large switching loss, and low efficiency. [0003] At present, autotransformers used as high-voltage transformers are generally used in high-voltage power transmi...

AI Technical Summary

Problems solved by technology

VSC converters are generally composed of IGBT switching elements and power capacitors. Due to the high switching losses of IGBTs, the efficiency is lower than 98%.

Therefore, VSC does not have the ability to control DC voltage in a large range, and it is difficult to meet people's requirements for high efficiency, large capacity, and long distance power transmission.

[0005] The existing thyristor LCC-type CSC with a maximum capacity of several GW and a voltage level of up to 800kV for power transmission has the ability to control active power bidirectionally. Since the thyristor is a semi-controlled device, the firing angle of the three-phase bridge The phase shift range is 0°-180°, and it can only be turned on by the trigger signal, but cannot be turned off. However, it does not have the ability to control reactive power, and needs to be equipped with a buffer capacitor to absorb reactive power, which makes the device smaller. Large, inconvenient to use in engineering applications

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