CN107681663A - Switching device and the Distributed Power Flow coordinated with fault current limiter control transmission line of electricity - Google Patents

Abstract

The invention discloses a switch device and a distributed power flow control transmission line matched with a fault current limiter. The current is transferred to N split wires, N≥2. The switch device can transfer the current delivered by the N-split conductor to the N+1-split conductor, or transfer the current delivered by the N+1-split conductor to the N-split conductor, so as to expand the adjustment range of the line impedance, thereby changing the direction of the line flow. To the role of power flow control, the structure is simple. The distributed power flow control transmission line has the function of controlling the power flow, and works with the fault current limiter to better control the problem of excessive fault current.

Description

Switchgear and Distributed Power Flow Control Transmission Line Cooperating with Fault Current Limiter

technical field

The invention relates to a switch device and a distributed power flow control transmission line matched with a fault current limiter, belonging to the field of electrical engineering.

Background technique

Since the concept of Unified Power Flow Controller (UPFC) was put forward, it immediately attracted people's attention, and various power flow control devices have been developed successively at home and abroad. The early projects put into operation abroad continued the multiple topology of three-phase voltage source converter units that were phase-shifted and stacked through transformers commonly used in the field of flexible AC transmission (FACTS) in the early days. Flat converter technology. The combination of series connection, three-level, multiplexing and modular technology of switching devices further improves the waveform quality, which is very suitable for slow and large-capacity fully-controlled switching devices using fundamental frequency modulation, and circuit breakers and mechanical switches are also used. A current flow control device designed with full control devices is not used, such as a current flow controller designed with a domestic patent application number of 200480044679.9.

However, with the continuous increase of the capacity of the power flow controller, more and more full-control devices are applied, which makes the overall structure of the device redundant, the control difficulty is increased, and the reliability is greatly reduced.

In addition, with the dramatic increase in the transmission capacity of the power system, the network structure of the grid interconnection is becoming more and more complex, and the short-circuit current levels in the power grids at all levels, especially in the three major load centers in my country, Jingjintang, Yangtze River Delta, and Pearl River Delta, continue to increase. The short-circuit current in some areas of the system has reached 70kA, exceeding the breaking capacity of the circuit breaker, and the rising trend is getting faster and faster, which has seriously threatened the safe operation of the system. Once a short-circuit fault occurs, it may cause burnout of related equipment in the faulty line, and the consequences are unimaginable. Exceeding the standard of short-circuit current poses a major threat to the safety and stability of power grid operation, and has become one of the main issues concerned in the planning and operation of large power grids. The measures to solve the fault current exceeding the standard mainly include two levels of methods. The first level is based on the system structure, such as busbar operation in parallel; the other level is based on the device point of view, developing fault current limiters, such as patent application number 201420592857.2 Designed magnetically confined fault current limiter.

Contents of the invention

In order to solve the above problems of power flow control and fault current exceeding the standard, the present invention provides a switchgear and a distributed power flow control transmission line coordinated with a fault current limiter.

In order to achieve the above object, the technical scheme adopted in the present invention is:

The switch device is characterized in that it transfers the current delivered by the N split wire to the N+1 split wire, or transfers the current delivered by the N+1 split wire to the N split wire, where N≥2.

The specific structure of the switching device that transfers the current delivered by the N split wire to the N+1 split wire is as follows:

It includes a confluence device and N+1 switching units, the input end of the converging device is connected to N sub-wires of N split wires, the output end of the converging device is connected to the input end of N+1 switching units, and the N+1 switching units The output terminals of the N+1 split wires are connected to the N+1 sub wires of the N+1 split wires.

The specific structure of the switching device that transfers the current delivered by the N+1 split wire to the N split wire is as follows:

It includes a confluence device and N switching units, the input end of the converging device is connected to the N+1 sub-wires of the N+1 split wires, the output end of the converging device is connected to the input ends of N switching units, and the output of the N switching units Connect the N sub-wires of the N-split wires.

The switching unit includes parallel bidirectional thyristors, RC loops and switches.

The switch is a mechanical switch.

The distributed power flow control transmission line coordinated with the fault current limiter includes T transmission towers, T≥2, and the first switching device is installed on the first transmission tower, and the first switching device transfers the current transmitted by the N split wires to On the N+1 split wire, the input end of the first switch device is connected to the N split wire, the output end of the first switch device is connected to the N+1 split wire, and the second switch device is installed on the Tth transmission tower, and the second switch device The current delivered by the N+1 split wire is transferred to the N split wire, the input end of the second switch device is connected to the N+1 split wire, the output end of the second switch device is connected to the N split wire, and the tth power transmission tower is connected to the tth N+1 split conductors are connected between +1 transmission towers, T-1≥t≥1.

The beneficial effects achieved by the present invention: 1. The switching device in the present invention can transfer the current delivered by the N split wire to the N+1 split wire, or transfer the current delivered by the N+1 split wire to the N split wire, expanding The adjustment range of the line impedance can change the direction of the line flow and play the role of flow control, with a simple structure; 2. The switch device for the flow control is installed on the transmission tower. Compared with the conventional flow controller, there is no large footprint. Problem; 3. The switchgear uses bidirectional thyristors and mechanical switches instead of full-control switching devices, so the reliability is high; 4. The distributed power flow control transmission line has the function of controlling the power flow. Better control the problem of excessive fault current.

Description of drawings

Fig. 1 is the structural representation of switchgear;

Figure 2 is a schematic diagram of the transmission line principle;

Figure 3 is a schematic diagram of the installation position of the switch device;

Fig. 4 is the structural representation of three-phase four-split conductor;

FIG. 5 is a schematic diagram of a five-split wire.

detailed description

The present invention will be further described below in conjunction with the accompanying drawings. The following examples are only used to illustrate the technical solution of the present invention more clearly, but not to limit the protection scope of the present invention.

As shown in FIG. 1 , the function of the switch device is to transfer the current delivered by the N-split wire to the N+1 split wire, or to transfer the current delivered by the N+1 split wire to the N-split wire, where N≥2.

As shown in Figure 2, the specific structure of the switching device that transfers the current delivered by the N-split wire to the N+1 split wire is as follows: it includes a confluence device and N+1 switching units, and the input end of the confluence device is connected to the N-split wire. For N sub-wires, the output end of the confluence device is connected to the input ends of N+1 switching units, and the output ends of the N+1 switching units are connected to N+1 sub-wires of the N+1 split wires.

3. The specific structure of the switching device that transfers the current delivered by the N+1 split wire to the N split wire is as follows: it includes a confluence device and N switching units, and the input end of the confluence device is connected to the N+1 sub-conductors of the N+1 split wire , the output end of the confluence device is connected to the input ends of N switching units, and the output ends of the N switching units are connected to N sub-wires of the N split wires.

The converging device can be a bus bar, and the switching unit includes a parallel bidirectional thyristor, an RC loop and a switch; wherein, the RC loop includes a series resistance and a capacitor, and the switch is a mechanical switch.

As shown in Figure 2, the distributed power flow control transmission line coordinated with the fault current limiter includes T transmission towers, T≥2, and the first switching device is installed on the first transmission tower, and the specific installation position is shown in Figure 3 As shown, the first switch device transfers the current delivered by the N split wire to the N+1 split wire, the input end of the first switch device is connected to the N split wire, the output end of the first switch device is connected to the N+1 split wire, and the T A second switchgear is installed on each transmission tower, and the second switchgear transfers the current delivered by the N+1 split wires to the N split wires, the input end of the second switchgear is connected to the N+1 split wires, and the second switchgear The output terminal is connected to N split wires, and N+1 split wires are connected between the tth transmission tower and the t+1th transmission tower, T-1≥t≥1.

In order to verify the present invention, take the typical 750kV three-phase four-split wire in Fig. 4 as an example, A, B, and C three-phase, each phase all has four sub-conductors, and the axes of the sub-conductors are distributed on a circle with R as the radius, each The connecting line between the sub-conductor and the center of the circle divides the circular surface into four equal parts.

The distance between the three phases is: D _ab ＝D _bc ＝0.5D _ca ＝12.8m;

D _ab , D _bc , and D _ca are the distance between Phase A and Phase B, the distance between Phase B and Phase C, and the distance between Phase A and Phase C, respectively;

The radius of the circle passed by the axis of each sub-conductor of each phase and the radius of the cross-sectional circle of the sub-conductor are: R=323mm, r=17.8mm;

Under normal operating conditions, the equivalent inductance of each sub-wire of the four-split wire is 0.3367Ohm/Km, and the current conveyed by the four-split wire is transferred to the five-split wire as shown in Figure 5. The equivalent inductance of each sub-wire of the five-split wire 0.3061Ohm/Km

In summary, by switching the split sub-conductors of each phase on the high-voltage transmission line (multi-split conductor), the impedance of the transmission line can be changed, thereby changing the power flow distribution of the line. At the same time, the switchgear is installed on the transmission tower, which is different from the conventional power flow control Compared with the device, there is no problem of occupying a large area, and the switching device adopts a bidirectional thyristor and a mechanical switch instead of a fully-controlled switching device, which has high reliability.

The above is only a preferred embodiment of the present invention, it should be pointed out that for those of ordinary skill in the art, without departing from the technical principle of the present invention, some improvements and modifications can also be made. It should also be regarded as the protection scope of the present invention.

Claims (6)

1. A switch device, characterized in that: the current transported by the N split wire is transferred to the N+1 split wire, or the current conveyed by the N+1 split wire is transferred to the N split wire, N≥2. 2. The switch device according to claim 1, characterized in that: the specific structure of the switch device that transfers the current delivered by the N split wire to the N+1 split wire is as follows: It includes a confluence device and N+1 switching units, the input end of the converging device is connected to N sub-wires of N split wires, the output end of the converging device is connected to the input end of N+1 switching units, and the N+1 switching units The output terminals of the N+1 split wires are connected to the N+1 sub wires of the N+1 split wires. 3. The switch device according to claim 1, characterized in that: the specific structure of the switch device that transfers the current delivered by the N+1 split wire to the N split wire is as follows: It includes a confluence device and N switching units, the input end of the converging device is connected to the N+1 sub-wires of the N+1 split wires, the output end of the converging device is connected to the input ends of N switching units, and the output of the N switching units Connect the N sub-wires of the N-split wires. 4. The switching device according to claim 2 or 3, characterized in that the switching unit comprises a parallel-connected bidirectional thyristor, an RC circuit and a switch. 5. Switching device according to claim 4, characterized in that the switch is a mechanical switch. 6. A distributed power flow control transmission line coordinated with a fault current limiter, characterized in that it includes T transmission towers, T≥2, and a first switching device is installed on the first transmission tower, and the first switching device splits N The current carried by the wire is transferred to the N+1 split wire, the input end of the first switch device is connected to the N split wire, the output end of the first switch device is connected to the N+1 split wire, and the second switch is installed on the Tth transmission tower device, the second switch device transfers the current delivered by the N+1 split wire to the N split wire, the input end of the second switch device is connected to the N+1 split wire, the output end of the second switch device is connected to the N split wire, and the tth N+1 split wires are connected between the first transmission tower and the t+1th transmission tower, T-1≥t≥1.