WO2016197973A1

WO2016197973A1 - Pre-charged high-speed direct-current breaker and control method therefor, and storage medium

Info

Publication number: WO2016197973A1
Application number: PCT/CN2016/085449
Authority: WO
Inventors: 吴金龙; 张军; 王先为; 何青连
Original assignee: 许继集团有限公司; 许继电气股份有限公司; 西安许继电力电子技术有限公司
Priority date: 2015-06-10
Filing date: 2016-06-12
Publication date: 2016-12-15
Also published as: CN104979796A; CN104979796B

Abstract

Disclosed are a pre-charged high-speed direct-current breaker and a control method therefor, and a computer storage medium. The pre-charged high-speed direct-current breaker comprises a cutout branch and a main electronic switch branch which are connected in parallel, wherein the main electronic switch branch is used for conducting a current in normal operation; the cutout branch comprises a cutout switch and a capacitor (C) which are connected in series, and both ends of the capacitor (C) are used for being connected to a charging power supply (UC); and the main electronic switch branch comprises at least one electronic switch unit, a plurality of electronic switch units are connected in series, and the electronic switch unit is composed of high-power switch devices. The pre-charged high-speed direct-current breaker is short in breaking time and little in loss, and also can decrease a fault current and release an overvoltage.

Description

Precharge type high speed DC circuit breaker, control method thereof and storage medium

Technical field

Embodiments of the present invention relate to the field of electronic technologies, and in particular, to a precharge type high speed DC circuit breaker, a control method thereof, and a storage medium.

Background technique

In recent years, with the continuous development of China's economy and technology, the demand for energy has also increased. In order to effectively solve the problem of uneven energy distribution in China, HVDC technology is now becoming an effective means. In particular, the gradual maturity of flexible DC transmission technology has promoted the development of distributed new energy. Since the straight-line system has the characteristics of rapid fault development, especially for the flexible DC transmission system based on the IGBT device, due to the existence of the anti-parallel diode, when the DC side fails, the short-circuit current cannot be quickly limited. Therefore, the research of DC circuit breaker has important significance for the stability of DC transmission system.

At present, high voltage DC circuit breakers mainly include mechanical DC circuit breakers, solid state DC circuit breakers and hybrid DC circuit breakers. The mechanical DC circuit breaker is based on the structure of the conventional mechanical AC circuit breaker, and increases the oscillating commutating circuit capable of automatically forming the zero-crossing point of the high-frequency oscillating current during the process of breaking the DC current. The utility model has the advantages of stable operation, strong carrying capacity and pass. The state loss is small, etc., but the contact is easily damaged by the breaking arc, the breaking capacity is limited, and the fault current cutting time is long.

Hybrid high-voltage DC circuit breaker combines mechanical DC circuit breaker and solid-state DC circuit breaker to combine their advantages. It has the advantages of low on-state loss, fast and controllable breaking, no arc, no sound, no need for special cooling equipment. Hybrid high-voltage DC circuit breakers generally use a power electronic switch to shunt the mechanical switch, and the discharge using the capacitor clamp capacitor cannot be accurately controlled. For example, the Chinese patent document "Hybrid DC Circuit Breaker" (CN 103021739 A) proposes a hybrid DC circuit breaker that is connected by a parallel high-speed vacuum switch, an LC forced transfer circuit, and an overvoltage limit. Circuit composition, LC forced transfer circuit includes series LC and power electronic gate turn-off devices.

Under normal conditions, the current flows from the high-speed vacuum switch. The pre-capacitor C in the LC forced-transfer circuit is charged with a certain voltage, and the power electronic gate can be turned off. The device is turned off. When the system is faulty, the circuit breaker needs to be disconnected. The control power electronic gate can be turned off, and the pre-capacitor in the LC forced transfer circuit can form a loop discharge through the power electronic gate to turn off the device, the inductor L and the high-speed vacuum switch, and finally achieve the DC shutdown purpose.

Then, the hybrid DC circuit breaker is very demanding on the breaking speed of the mechanical switch. Generally, the breaking is completed within 3ms and the insulation blocking characteristic is restored. At present, the development of such a fast high-voltage mechanical switch is very difficult, and thus extremely large. The engineering application of the solution is limited.

Summary of the invention

Embodiments of the present invention are intended to provide a precharge type high speed DC circuit breaker, a control method thereof and a storage medium for solving the defects of the hybrid DC circuit breaker in the prior art.

The solution of the embodiment of the present invention is as follows:

In a first aspect of the embodiments of the present invention, there are provided a precharging type high speed DC circuit breaker comprising a parallel interrupting branch and a main electronic switching branch, wherein the main electronic switching branch is used for circulating current during normal operation; The interrupted flow branch includes a series-connected current interrupt switch and a capacitor, and both ends of the capacitor are used for connecting a charging power source; the main electronic switch branch includes at least one electronic switch unit, and when the main electronic switch branch includes at least two In the case of the electronic switching unit, at least two of the electronic switching units are connected in series.

Based on the above solution, a current limiting inductor is further disposed in the current interrupting branch, and the current limiting inductor is connected in series with the capacitor.

Based on the above solution, the current interrupt switch is composed of at least one pair of anti-parallel thyristors, and when the current interrupt switch includes at least two pairs of the anti-parallel thyristors, at least two pairs of the anti-parallel thyristors are connected in series.

Based on the above scheme, the electronic switch unit is a pair of anti-parallel thyristors.

Based on the above solution, the pre-charging type high-speed DC circuit breaker further includes at least one arrester, and the arrester is connected in parallel with the corresponding branch or element of the current-breaking branch and the main electronic switch branch.

Based on the above scheme, the electronic switch unit is constituted by a switching device whose rated current is greater than a predetermined current threshold.

Based on the above solution, the predetermined current threshold is not lower than the short circuit current of the current system of the precharge type high speed DC circuit breaker application.

Based on the above solution, the current interrupt switch and the switch included in the electronic switch unit are all solid state switches.

The second aspect of the embodiments of the present invention further provides a method for controlling a precharge type high speed DC circuit breaker, including:

Under normal conditions, the charging power supply is controlled to charge the capacitor; when the circuit breaker needs to be disconnected, the charging circuit of the capacitor is turned off, and the off-current branch is turned on, so that the main electronic switch branch is turned off after the current is zero.

A third aspect of the embodiments of the present invention provides a computer storage medium, where the computer storage medium stores computer executable instructions, and the computer executable instructions are used in the foregoing control method.

The topology structure and control process of the circuit breaker in the embodiment of the invention are simple, and are easy to implement in actual engineering.

Capacitor pre-charging is used to provide the reverse voltage required for turn-off of the thyristor in the main electronic switch. During the disconnection process of the pre-charging circuit, there is no current operation, which can realize rapid rectification of the charging circuit; the off time of the main electronic switch is very small, which ensures the disconnection time of the circuit breaker; the thyristor is used as the main electronic switch, and the DC circuit breaker operates normally. The loss during the process is very small; the charging circuit formed by the capacitor in the interrupted branch can quickly reduce the fault current in the circuit breaker. During the shutdown process, an overvoltage is formed on the circuit breaker. Due to the protection of the arrester, the voltage across the circuit breaker is limited to the full range of insulation requirements, and the energy is discharged by the arrester during the circuit breaker shutdown.

DRAWINGS

1 is a schematic diagram of a DC circuit breaker topology structure according to an embodiment of the present invention;

2 is a control logic in a process of turning off a DC circuit breaker according to an embodiment of the present invention;

3 is a working state of a DC circuit breaker in a normal operation of a precharge type high speed DC circuit breaker according to an embodiment of the present invention;

4 is a schematic flow chart of a DC circuit breaker commutation according to an embodiment of the present invention;

FIG. 5 is a schematic diagram of an operating state of a circuit breaker in a process of turning off a main electronic switch branch according to an embodiment of the present invention; FIG.

6 is a schematic diagram of current waveforms of a main electronic switch branch during a disconnection process according to an embodiment of the present invention;

FIG. 7 is a schematic diagram of current waveforms of a disconnecting process interrupt flow branch according to an embodiment of the present invention.

detailed description

The preferred embodiments of the present invention are described in detail below with reference to the accompanying drawings.

The pre-charged all-solid-state high-speed DC circuit breaker shown in FIG. 1 includes a parallel interrupting branch, a main electronic switch branch, and a lightning arrester branch. The main electronic switch branch is used for circulating current during normal operation; the cut-off branch includes a series-connected cut-off switch C, a capacitor and a current-limiting inductor L, and the two ends of the capacitor are connected to the charging power source Uc through a charging switch; the main electronic switch branch includes At least one electronic switch unit, a plurality of electronic switch units connected in series, and the electronic switch unit is composed of a high power switch device. The arrester is connected in parallel with the branch circuit and the main electronic switch branch. The high power switching device is a switching device with a rated current greater than a predetermined current threshold. Typically, the predetermined current threshold is not lower than the short circuit current of the current system of the pre-charged high speed DC circuit breaker application.

The pre-charged all-solid-state high-speed DC circuit breaker in this embodiment does not use a mechanical switch. The use of solid-state switches, power electronic devices in solid-state switches can all use thyristors. That is, the smallest unit of the current interrupt switch and the smallest unit of the main electronic switch are a pair of anti-parallel thyristors. Thyristors are semi-controlled devices, and only the trigger turn-on process is controllable, but the turn-off process can only rely on circuit characteristics.

Control methods can include:

In the normal state, the charging power source is controlled to charge the capacitor;

When the circuit breaker needs to be disconnected, the charging circuit of the capacitor is first turned off, and then the conduction cut-off branch is triggered, so that after a period of time, the main electronic switch branch is turned off after the current is zero.

Referring to the drawings, in the DC circuit breaker control logic of this embodiment, there are only two operation steps: cutting off the pre-charging circuit of the current-carrying capacitor; and triggering the conduction-breaking switch. In normal operation, the main electronic switch is in an on state, and the DC current in the circuit flows through the main electronic switch branch of the circuit breaker. In the current-breaking branch, the current-cut switch is in the off state, and the capacitor is charged through the pre-charging circuit.

When the fault occurs, that is, at time t0, the pre-charging circuit of the short-circuit capacitor is first turned off. At this time, the capacitor has been charged, and then the on-off switch is triggered, and a certain delay is left in the operation of the two sets of switches, as shown in FIG. 2 From t0 to t1.

After the current-breaking switch is triggered, the current-carrying capacitor and the current limiter form a discharge loop. The current in the current-breaking branch gradually rises, the voltage across the main electronic switch branch is reversed, and the current in the main electronic switch rapidly drops to zero. It is necessary to leave enough turn-off time (anti-arc angle) for the thyristor, and all the thyristors in the main electronic switch are in the off state. T1 to t2 as described in Fig. 2.

After the current drops to zero in the main electronic switch, the fault current flows through the cut-off branch and forms a capacitive reverse charging loop through the current limiter, etc., and the current gradually decreases, and the current in the interrupted branch decreases. After zero, the breaker completes the disconnect task.

Figure 3 shows the operating state of a pre-charged all-solid-state high-speed DC circuit breaker in normal operation.

During normal operation, the current-carrying branch interrupts the flow capacitor pre-charging circuit in a conducting state, the thyristor in the current-cutting switch is in an off state, and no current flows in the current-breaking branch.

During normal operation, all thyristors of the main electronic switch branch are in conduction, and the DC current of the circuit flows from the main electronic switch branch.

Figure 4 shows the shutdown process of the main electronic switch branch of the pre-charged all-solid-state high-speed DC circuit breaker.

When the DC circuit fails and the circuit breaker needs to be disconnected, firstly, the pre-charging circuit of the interrupting current interrupt circuit capacitor is turned off. At this time, the capacitor has been pre-charged, and then all the thyristors in the cut-off switch are triggered.

After the current interrupt switch is turned on, the current interrupting capacitor, the current limiter, and the current interrupt switch form a discharge loop, and the current Id1 in the current interrupting branch starts to increase.

After the current interrupt switch is turned on, the voltage across the thyristor is UT2<0, that is, the thyristor is reverse voltage at both ends, and the current Id2 on the main electronic switch branch starts to rapidly decrease to zero; after the Id2 decreases to zero, After leaving a sufficient turn-off time (extinguishing angle) for the thyristor in the main electronic switch branch, the main electronic switch branch is turned off.

Figure 5 shows the operating state of the pre-charged all-solid-state circuit breaker during the shutdown of the interrupted branch.

After the main electronic switch branch is turned off, the fault current flows through the cut-off branch. At this time, the current interrupting capacitor, the current limiter, the current interrupt switch, and the like form a charging circuit. The fault current reversely charges the capacitor through the charging circuit, and the current Id1 in the interrupting branch gradually decreases. When the current in the interrupting branch decreases to zero, the circuit breaker completes the task of disconnecting the DC circuit.

During the shutdown of the main electronic switch branch and the shutdown of the interrupted branch, an overvoltage is formed on the circuit breaker, and the current of the arrester in the circuit breaker rises, absorbing energy.

6 and FIG. 7 are diagrams showing current waveforms of a main electronic switch branch and a current interrupt branch during a disconnection process of a precharged all solid state high speed DC speed circuit breaker according to an embodiment of the present invention.

The circuit breaker starts to operate at 1ms, and the current-carrying capacitor pre-charging circuit is cut off. At this time, the capacitor pre-charging process has been completed. At 2ms, all the thyristors in the turn-off switch are triggered, and the capacitor, the current limiter and the current-cut switch form a discharge loop. A reverse voltage is formed across the main electronic switch branch, the current in the main electronic switch branch begins to decrease, and the current in the interrupted branch begins to increase. Main electronic opening The current in the off-branch circuit is zero at 2.05ms, and the fault current flows through the cut-off branch. At this point, the capacitor discharge process is not completed, and the main electronic switch is still in the reverse voltage state. The current-carrying capacitor, the current limiter, and the current-cutting switch form a capacitor charging circuit. The fault current charges the capacitor in reverse, and the voltage on the capacitor begins to decrease rapidly, and then begins to increase in the reverse direction. As the voltage of the current-carrying capacitor changes, the voltage on the main electronic switch branch gradually changes from the reverse direction to the forward direction, and the thyristor completes the recovery of the forward blocking capability before the voltage becomes positive. After the capacitor is reversely charged, the current on the interrupted branch begins to gradually decrease. Before the 5.5ms time, the current in the circuit breaker drops to zero and the DC breaker completes the shutdown. The entire working process of the circuit breaker lasts less than 5ms.

The embodiment of the invention proposes that during the disconnection process of the pre-charged all-solid-state high-speed circuit breaker, only the pre-charging circuit is disconnected and the current-cutting switch is triggered to conduct two control steps. After the current-carrying switch is triggered to turn on, the capacitor forms a discharge loop, and a reverse voltage is formed across the main electronic switch, and the current on the main electronic switch branch rapidly drops to zero. After the main electronic switch is turned off, the fault current flows through the cut-off branch and reversely charges the capacitor through a current limiter or the like. The current in the current-breaking branch begins to drop rapidly to zero and the circuit breaker completes the disconnection. The mechanical switch is not used in the circuit breaker, and the current is transferred and turned off by controlling the power electronic device to ensure the operation time of the circuit breaker. The number of power electronic devices in the solid state switch and the commutation switch is small, which significantly reduces the loss in the operation of the circuit breaker and has good economy.

In the embodiment, the solid state switch uses a thyristor. As another embodiment, one or a combination of a half-controlled power electronic device or a full-controlled power electronic device, for example, an IGBT, a GTO, or the like, may also be used. It should be noted that if a fully controlled device is used, the control process of the control method will change accordingly.

As another embodiment, a lightning arrester may be selectively applied to the current interrupting branch and the corresponding component of the main electronic switch branch according to a specific situation.

The embodiment of the present invention further provides a computer storage medium, where the computer storage medium stores computer executable instructions, and the computer executable instructions are used to execute the foregoing control party. law. The computer storage medium can be any type of storage medium such as an optical disk, a hard disk, a flash drive, or a magnetic tape, and is optionally a non-transitory storage medium.

The above is only a preferred embodiment of the embodiments of the present invention, and is not intended to limit the scope of protection of the embodiments of the present invention. Modifications made in accordance with the principles of the invention are understood to fall within the scope of the invention.

Claims

A pre-charging type high-speed DC circuit breaker comprising a parallel interrupting branch and a main electronic switch branch, and the main electronic switch branch is used for circulating current during normal operation;

The current interrupting branch includes a series-connected current interrupting switch and a capacitor, and the two ends of the capacitor are used for connecting the charging power source;

The main electronic switch branch includes at least one electronic switch unit, and when the main electronic switch branch includes at least two of the electronic switch units, at least two of the electronic switch units are connected in series.
The pre-charging type high-speed DC circuit breaker according to claim 1, wherein a current limiting inductor is further disposed in the current interrupting branch, and the current limiting inductor is connected in series with the capacitor.
The precharge type high speed DC circuit breaker according to claim 2, wherein said current interrupt switch is constituted by at least one pair of antiparallel thyristors, and when said current interrupt switch comprises at least two pairs of said reverse parallel thyristors At least two pairs of the anti-parallel thyristors are connected in series.
The precharge type high speed DC circuit breaker according to claim 3, wherein said electronic switching unit comprises a pair of anti-parallel thyristors.
The precharge type high speed DC circuit breaker according to claim 1 or 2 or 3 or 4, wherein said precharge type high speed DC circuit breaker further comprises at least one arrester, said arrester and said current interrupting branch and said main electronic switch The corresponding branch or component of the branch is connected in parallel.
The precharge type high speed DC circuit breaker according to claim 1, wherein said electronic switch unit is constituted by a switching device having a rated current greater than a predetermined current threshold.
The precharge type high speed DC circuit breaker according to claim 6, wherein said predetermined current threshold is not lower than a short circuit current of said current system of said precharge type high speed DC circuit breaker application.
The precharge type high speed DC circuit breaker according to claim 1, wherein the cutoff switch and the switch included in the electronic switch unit are both solid state switches.
A control for precharging type high speed DC circuit breaker according to any one of claims 1 to Method, including:

Under normal conditions, the charging power source is controlled to charge the capacitor;

When the circuit breaker needs to be disconnected, the charging circuit of the capacitor is turned off, and the conduction cut-off branch is triggered, so that after a period of time, the main electronic switch branch is turned off after the current is zero.
A computer storage medium having stored therein computer executable instructions for executing the control method of claim 9.