CN204179677U - A kind of extra-high voltage DC transmission system suppressing DC side first-harmonic resonance - Google Patents

Abstract

The utility model discloses a kind of extra-high voltage DC transmission system suppressing DC side first-harmonic resonance, object is, effectively can reduce the fundamental frequency harmonics electric current of DC transmission system DC side, prevent converter transformer core sataration, avoid false protection.The technical scheme adopted is: comprise the converter transformer (1), converter valve (2), smoothing reactor (3) and the neutral bus capacitor (5) that connect successively, and the DC filter be connected between polar curve and neutral bus, described neutral bus is in series with first-harmonic trap (4), described first-harmonic trap (4) adopts tuning circuit, comprises capacitor parallel with one another and reactor.

Description

A UHVDC transmission system that suppresses the fundamental resonance of the DC side

technical field

The utility model belongs to the field of high-voltage direct-current transmission, and in particular relates to an ultra-high-voltage direct-current transmission system for suppressing fundamental wave resonance on a direct-current side.

Background technique

With the vigorous development of UHV DC transmission projects in my country, the length of domestic UHV DC transmission projects has reached or exceeded 2000km. Studies have shown that 2000km is a sensitive length for fundamental resonance to occur, and UHVDC transmission projects near this length are prone to fundamental resonance.

For long-distance and large-capacity UHVDC power transmission projects, 50Hz harmonic currents will appear due to the coupling effect between the DC line and the parallel AC line. If the DC system presents low impedance near 50Hz, the fundamental frequency harmonic current will be too large. In steady-state operation, the large fundamental frequency harmonic current on the DC side will cause the DC bias magnetization of the converter transformer to saturate the iron core, resulting in a series of phenomena such as overheating and increased noise. The harmonic current under fault conditions often It will be larger, which may cause overvoltage on the DC side and protection malfunction. Therefore, it is necessary to suppress and study the fundamental resonance on the DC side of the UHVDC transmission system.

Contents of the invention

In order to solve the problems in the prior art, the utility model proposes a method that can effectively reduce the fundamental frequency harmonic current on the DC side of the DC power transmission system, prevent the saturation of the converter transformer core, and avoid protection malfunctions to suppress the fundamental resonance of the DC side. UHV DC transmission system.

In order to achieve the above purpose, the technical solution adopted by the utility model is: including a converter transformer, a converter valve, a smoothing reactor and a neutral bus capacitor, and a DC filter connected between the pole line and the neutral bus, A fundamental wave trap is also connected in series on the neutral bus, and the fundamental wave trap adopts a tuned circuit, including capacitors and reactors connected in parallel.

The fundamental wave trap is located between the smoothing reactor and the high voltage side of the neutral bus capacitor.

The resonant frequency of the fundamental wave trap is 50Hz.

The inductance value of the reactor is the same as that of a single smoothing reactor, and the values of the inductance of the reactor and the capacitance of the capacitor ensure that the resonant frequency is 50 Hz.

The number of said reactor and capacitor is 1.

The installation quantity of said fundamental wave trap is one per pole UHVDC power transmission system.

A lightning arrester is also provided in the UHV DC transmission system.

Compared with the prior art, the utility model combines the principle of the fundamental wave trap with UHV DC transmission technology, and the fundamental wave trap can prevent the passage of the fundamental frequency harmonic current in the DC circuit. For DC current and other frequency bands The harmonic current can pass through normally, which can effectively reduce the fundamental frequency harmonic current on the DC side of the DC transmission system, prevent the saturation of the converter transformer core, and avoid protection malfunctions.

Furthermore, the fundamental wave trap is located between the neutral bus smoothing reactor and the high voltage side of the neutral bus capacitor, which can effectively reduce the fundamental frequency harmonic current on the DC side of the system, and by choosing the installation position of the wave trap reasonably, The insulation cost of the fundamental wave trap equipment is reduced to the greatest extent.

Furthermore, for long-distance and large-capacity UHVDC power transmission projects, 50Hz harmonic currents will appear on the DC line and the parallel AC line due to the coupling effect, and the DC system will present low impedance near 50Hz, which will lead to excessive fundamental frequency harmonic current. In view of this phenomenon, the resonant frequency of the fundamental wave trap is set to 50Hz, which can prevent the passage of the fundamental frequency harmonic current in the DC circuit, and the DC current and harmonic currents in other frequency bands can pass normally, which can effectively Reduce the fundamental frequency harmonic current on the DC side of the DC transmission system.

Description of drawings

Fig. 1 is a schematic circuit diagram of the utility model;

Among them, 1 is a converter transformer, 2 is a converter valve, 3 is a smoothing reactor, 4 is a fundamental wave trap, and 5 is a neutral bus capacitor.

Detailed ways

Below in conjunction with embodiment the utility model will be described further.

Referring to Fig. 1, the technical solution adopted by the utility model is: comprising sequentially connected converter transformer 1, converter valve 2, smoothing reactor 3 and neutral bus capacitor 5, and connected between the pole line and the neutral bus There is a fundamental wave trap 4 connected in series on the neutral bus, and the fundamental wave trap 4 is located between the smoothing reactor 3 and the high voltage side of the neutral bus capacitor 5 . The fundamental wave trap 4 adopts a tuned circuit, including a capacitor and a reactor connected in parallel, the resonant frequency of the fundamental wave trap 3 is 50Hz, the inductance value of the reactor and the inductance value of a single smoothing reactor 3 Similarly, the values of the inductance of the reactor and the capacitance of the capacitor ensure that the resonant frequency is 50 Hz. Surge arresters are also installed in the UHV DC transmission system.

A group of fundamental wave traps 4 are connected in series on each pole of the neutral bus on the DC side of the sending end. The fundamental wave traps 4 are tuning circuits, and the tuning circuits are a reactor and a capacitor connected in parallel. The resonant frequency of the inductor and the capacitor is 50 Hz, and the fundamental wave trap 4 can prevent the passage of the fundamental frequency harmonic current in the DC circuit, and the direct current and harmonic currents of other frequency bands can pass normally.

The specific installation position of the fundamental wave trap 4 of the present utility model is between the neutral bus smoothing reactor 3 and the high-voltage side of the neutral bus capacitor 5. The fundamental wave trap is a tuning circuit with a tuning frequency of 50 Hz. The circuit consists of reactors and capacitors connected in parallel. It is to combine the principle of the fundamental wave trap with UHV DC transmission technology, which can effectively reduce the fundamental frequency harmonic current on the DC side of the DC transmission system, prevent the saturation of the converter transformer core, and avoid protection malfunctions.

The technical advantage of the utility model lies in: combining the principle of the fundamental wave trap with UHV DC transmission technology can effectively reduce the fundamental frequency harmonic current on the DC side of the system; rationally selecting the installation position of the wave trap to maximize Reduce the insulation cost of wave trap equipment.

The utility model combines the principle of the fundamental wave trap with the UHV DC transmission technology, the fundamental wave trap can prevent the passage of the fundamental frequency harmonic current in the DC circuit, and it can be normal for the DC current and the harmonic current of other frequency bands Through the method, the fundamental frequency harmonic current on the DC side of the DC transmission system can be effectively reduced, the saturation of the iron core of the converter transformer can be prevented, and the protection malfunction can be avoided.

The fundamental wave trap is located between the neutral bus smoothing reactor and the high voltage side of the neutral bus capacitor. It greatly reduces the insulation cost of the fundamental wave trap equipment.

For long-distance and large-capacity UHVDC power transmission projects, the DC line and the parallel AC line will generate 50Hz harmonic current due to coupling, and the DC system will present low impedance near 50Hz, which will lead to excessive fundamental frequency harmonic current. This phenomenon sets the resonant frequency of the fundamental wave trap to 50Hz, which can prevent the passage of the fundamental frequency harmonic current in the DC circuit, and can normally pass the DC current and harmonic currents in other frequency bands, which can effectively reduce the DC power transmission. Fundamental frequency harmonic current on the DC side of the system.

The above is only one embodiment of the utility model, not all or the only implementation. Any equivalent transformation adopted by those of ordinary skill in the art to the technical solution of the utility model by reading the specification of the utility model shall be considered as the present invention. covered by the claims of the utility model.

Claims (7)

1. A UHVDC power transmission system for suppressing the fundamental resonance of the DC side, characterized in that: it comprises a converter transformer (1), a converter valve (2), a smoothing reactor (3) and a neutral bus connected in sequence A capacitor (5), and a DC filter connected between the pole line and the neutral bus, the fundamental wave trap (4) is connected in series on the neutral bus, and the fundamental wave trap (4) A tuned circuit is used, including capacitors and reactors connected in parallel with each other. 2. An UHVDC power transmission system for suppressing the fundamental resonance of the DC side according to claim 1, characterized in that: the fundamental wave trap (4) is located between the smoothing reactor (3) and the neutral Between the high voltage side of the bus capacitor (5). 3. An UHVDC power transmission system for suppressing the fundamental resonance of the DC side according to claim 1 or 2, characterized in that: the resonance frequency of the fundamental wave trap (3) is 50 Hz. 4. An UHVDC power transmission system capable of suppressing fundamental resonance at the DC side according to claim 3, characterized in that: the inductance value of the reactor is the same as the inductance value of a single smoothing reactor (3), The values of the inductance of the reactor and the capacitance of the capacitor ensure that the resonant frequency is 50Hz. 5 . The UHVDC power transmission system for suppressing the fundamental resonance of the DC side according to claim 4 , wherein the number of the reactor and the capacitor is one. 5 . 6. An UHVDC power transmission system for suppressing fundamental wave resonance at the DC side according to claim 1, characterized in that: the number of installations of the fundamental wave trap (4) in each pole of the UHVDC power transmission system for 1 pc. 7. The UHV DC power transmission system for suppressing the fundamental resonance of the DC side according to claim 1, characterized in that: said UHV DC power transmission system is also provided with a lightning arrester.