Hybrid compensation system for negative-sequence current in high speed railway

Abstract

The invention discloses a hybrid compensation system for negative-sequence current in a high speed railway. The hybrid compensation system comprises a railway power regulator, two single-phase three-winding step-down transformers, m groups of thyristor switched capacitors of the same parameter, and a group of thyristor controlled reactors. The railway power regulator is connected with low-voltage sides of the two single-phase three-winding step-down transformers by virtue of joint inductance; high-voltage sides of the two single-phase three-winding step-down transformers are connected with two single-phase power supply arms of a secondary side of a three-phase Vv traction transformer; the m groups of thyristor switched capacitors of the same parameter are arranged on the low-voltage sides of the single-phase three-winding step-down transformers connected with a voltage phase advance power supply arm; and the group of thyristor controlled reactors are arranged on the low-voltage sides of the single-phase three-winding step-down transformers connected with a voltage phase lag power supply arm. According to the hybrid compensation system, the negative-sequence current can be effectively compensated, the power of an active compensation device can be reduced, and the cost is reduced. Therefore, the hybrid compensation system has good development prospects in the field of negative-sequence compensation of the high speed railway.

Description

technical field [0001] The invention relates to a negative-sequence current compensation system, in particular to a mixed compensation system for negative-sequence current in high-speed railways. Background technique [0002] High-speed railway has the characteristics of large transportation capacity, low energy consumption, and small environmental impact, and has been widely valued and applied worldwide. The Hexie high-speed railway currently in operation in my country uses AC-DC-AC electric locomotives and a four-quadrant PWM rectification method. The power factor of the locomotives is close to 1, and the content of low-order harmonics is small. However, since the high-speed railway adopts single-phase power frequency AC power supply, its asymmetry leads to the existence of negative sequence current in the three-phase grid current. The negative sequence current will cause problems such as generator vibration, insufficient transformer output, and large network loss. Therefo...

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Problems solved by technology

Among them, when using SVC, there are two access methods, one is to connect SVC to the three-phase grid side, and the required SVC capacity is large when connected to the three-phase grid side; the other is to connect SVC to single-phase power supply On the arm side, the negative sequence compensation effect is not ideal when connected to the single-phase power supply arm side; when using STATCOM, since the STATCOM needs to be connected to the three-phase high-voltage side, and the voltage on the high-voltage side is as high as 110KV or 220KV, the STATCOM needs to be designed as a series multiple structure , leading to complex structure and high cost of STATCOM; while RPC is in the leading position in negative sequence compensation technology and is a typical compensation device. RPC is composed of two back-to-back converters, and the DC side of the two converters shares a capacitor. However, since the RPC is an active device, when the RPC is used alone to compensate the negative sequence current, it will cause the problem of large capacity and high cost of the RPC.

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