Method and device for protecting alternating-current line of alternating-current and direct-current hybrid system

Abstract

The invention relates to a protection method and device for an alternating current line of an alternating current-direct current hybrid system, belongs to the technical field of relay protection of a power system, and solves the problem of incorrect action of alternating current line protection caused by commutation failure in the alternating current-direct current hybrid system in the prior art. The method comprises the following steps that when it is monitored that the alternating current and direct current hybrid system breaks down, voltage and current at buses at the two ends of an alternating current line on the inverter side, current flowing through an alternating current filter and a reactive compensation device, direct current of a direct current power transmission line and the conduction state of a converter valve in a converter are collected; based on the collected information, obtaining a compound mode power difference of back side systems at the two ends of the alternating current line; according to the compound mode power difference and a protection action criterion, determining whether an internal fault of the alternating current line occurs or not; and if so, starting pilot protection of the AC line. According to the invention, the problem of incorrect action of AC line protection possibly caused by commutation failure is solved.

Description

Technical field

[0001] The present invention relates to the technical field of power system relay protection, and in particular to a protection method and device for AC lines in an AC-DC hybrid system. Background technique

[0002] With the development of the power system, high-voltage direct current transmission is increasingly used in practical projects, and the application of power electronic equipment also makes the operation of the power grid more complex. In an AC-DC hybrid system, commutation failure is very easy to occur, causing the traditional AC line protection to refuse to operate or malfunction. Therefore, considering the occurrence of commutation failure, it is important to quickly and accurately isolate the AC line fault to ensure the safety of the power grid. Stable operation is of great significance.

[0003] At present, AC line longitudinal protection is mainly divided into two categories according to the physical quantities based on the measuring componen...

Examples

Embodiment 1

[0071] A specific embodiment 1 of the present invention discloses a protection method for an AC line of an AC / DC hybrid system, such as figure 1 shown, including the following steps:

[0072] S1. When monitoring the failure of the AC / DC hybrid system, collect the voltage and current at the busbars at both ends of the AC line on the inverter side, the current flowing through the AC filter and the reactive power compensation device, and the DC current and the DC transmission line. The conduction state of the converter valve in the converter;

[0073] Specifically, based on the differential current transformer monitoring, the on and off state signals of each converter valve of the converter are obtained when a fault occurs.

[0074] S2. Based on the collected information, obtain the composite mode power difference of the backside systems at both ends of the AC line;

[0075] S3. According to the power difference of the composite mode and the protection action criterion, determi...

Embodiment 2

[0246] A specific embodiment 2 of the present invention provides a protection device for an AC line of an AC / DC hybrid system. The schematic structural diagram is as follows: Figure 5 shown, including:

[0247] The data acquisition module is used to collect the voltage and current at the busbars at both ends of the AC line on the inverter side, the current flowing through the AC filter and the reactive power compensation device, and the DC transmission line when a fault is detected in the AC / DC hybrid system. The DC current of the converter and the conduction state of the converter valve in the converter;

[0248] a composite mode power difference calculation module, used for obtaining the composite mode power difference of the backside systems at both ends of the AC line based on the collected information;

[0249] an intra-area fault judging module, used for determining whether an intra-area fault of the AC line occurs according to the composite mode power difference and t...

Embodiment 3

[0265] In order to verify the correctness of Embodiments 1 and 2 of the present invention, in this embodiment, the solutions in the above-mentioned embodiments are tested and verified on the RT-LAB platform. Table 1 shows the main parameters of the AC-DC hybrid system.

[0266] Table 1 Main parameters of AC / DC hybrid system

[0267]

[0268] Scenario 1 is set in this embodiment: A phase-to-ground fault, AB two-phase ground fault, and BC two-phase-to-phase fault occur at the fault points of the AC line M-N, respectively, and the transition resistance varies from 0 to 300Ω. E in the above three fault conditions m and E n like Image 6 shown.

[0269] Depend on Image 6 (a), Image 6 (b), Image 6 (c), Image 6 (d), Image 6 (e) and Image 6 (f) It can be seen that under different fault types, E m , E n are less than the threshold value. As the transition resistance increases, E m Decrease first and then increase, E n It gradually increases in single-phase fault...

Technical field

[0001] The present invention relates to the technical field of power system relay protection, and in particular to a protection method and device for AC lines in an AC-DC hybrid system. Background technique

[0002] With the development of the power system, high-voltage direct current transmission is increasingly used in practical projects, and the application of power electronic equipment also makes the operation of the power grid more complex. In an AC-DC hybrid system, commutation failure is very easy to occur, causing the traditional AC line protection to refuse to operate or malfunction. Therefore, considering the occurrence of commutation failure, it is important to quickly and accurately isolate the AC line fault to ensure the safety of the power grid. Stable operation is of great significance.

[0003] At present, AC line longitudinal protection is mainly divided into two categories according to the physical quantities based on the measuring componen...

Examples

Embodiment 1

[0071] A specific embodiment 1 of the present invention discloses a protection method for an AC line of an AC / DC hybrid system, such as figure 1 shown, including the following steps:

[0072] S1. When monitoring the failure of the AC / DC hybrid system, collect the voltage and current at the busbars at both ends of the AC line on the inverter side, the current flowing through the AC filter and the reactive power compensation device, and the DC current and the DC transmission line. The conduction state of the converter valve in the converter;

[0073] Specifically, based on the differential current transformer monitoring, the on and off state signals of each converter valve of the converter are obtained when a fault occurs.

[0074] S2. Based on the collected information, obtain the composite mode power difference of the backside systems at both ends of the AC line;

[0075] S3. According to the power difference of the composite mode and the protection action criterion, determi...

Embodiment 2

[0246] A specific embodiment 2 of the present invention provides a protection device for an AC line of an AC / DC hybrid system. The schematic structural diagram is as follows: Figure 5 shown, including:

[0247] The data acquisition module is used to collect the voltage and current at the busbars at both ends of the AC line on the inverter side, the current flowing through the AC filter and the reactive power compensation device, and the DC transmission line when a fault is detected in the AC / DC hybrid system. The DC current of the converter and the conduction state of the converter valve in the converter;

[0248] a composite mode power difference calculation module, used for obtaining the composite mode power difference of the backside systems at both ends of the AC line based on the collected information;

[0249] an intra-area fault judging module, used for determining whether an intra-area fault of the AC line occurs according to the composite mode power difference and t...

Embodiment 3

[0265] In order to verify the correctness of Embodiments 1 and 2 of the present invention, in this embodiment, the solutions in the above-mentioned embodiments are tested and verified on the RT-LAB platform. Table 1 shows the main parameters of the AC-DC hybrid system.

[0266] Table 1 Main parameters of AC / DC hybrid system

[0267]

[0268] Scenario 1 is set in this embodiment: A phase-to-ground fault, AB two-phase ground fault, and BC two-phase-to-phase fault occur at the fault points of the AC line M-N, respectively, and the transition resistance varies from 0 to 300Ω. E in the above three fault conditions m and E n like Image 6 shown.

[0269] Depend on Image 6 (a), Image 6 (b), Image 6 (c), Image 6 (d), Image 6 (e) and Image 6 (f) It can be seen that under different fault types, E m , E n are less than the threshold value. As the transition resistance increases, E m Decrease first and then increase, E n It gradually increases in single-phase fault...

Images