CN111030060A

CN111030060A - Clamp-on circuit breaker topology suitable for direct current fault removal

Info

Publication number: CN111030060A
Application number: CN201911241014.1A
Authority: CN
Inventors: 许建中; 武董一; 李嘉龙
Original assignee: North China Electric Power University
Current assignee: North China Electric Power University
Priority date: 2019-12-06
Filing date: 2019-12-06
Publication date: 2020-04-17

Abstract

The invention relates to a clamp pressing type circuit breaker topology suitable for clearing direct current faults, belonging to the technical field of a multi-terminal direct current and direct current power grid; the faults are cleared by utilizing the clamping and current limiting capacity of the pre-charging capacitor after the pre-charging capacitor is connected into a fault loop, wherein the pre-charging capacitor adopts a breaking input method, so that the impact on the clamp voltage type circuit breaker can be effectively reduced; the method realizes fault isolation and fault energy dissipation decoupling, performs quick isolation and then slowly dissipates energy, and has certain engineering value.

Description

Clamp-on circuit breaker topology suitable for direct current fault removal

Technical Field

The invention relates to a clamp pressing type circuit breaker topology suitable for clearing direct current faults, and belongs to the field of multi-terminal direct current and direct current power grids.

Background

With the increasing exhaustion of fossil resources in the world, the development of renewable energy sources is out of gear, and the flexible direct-current power grid is rapidly developed. The flexible direct current transmission is a new generation of power transmission technology based on a fully-controlled power electronic device, and a direct current power grid based on the flexible direct current transmission can better realize wide-area complementary transmission of large-scale renewable energy sources, so that the flexible direct current transmission is one of important directions for development and revolution of the power grid in the future. At present, the Zhang Bei engineering and the Wudongde engineering under construction in China are symbolic engineering of direct current transmission, and future direct current power grid engineering is developed towards more terminals, larger capacity and higher reliability by taking the Zhang Bei engineering and the Wudongde engineering as starting points.

The modular multilevel converter topological structure is suitable for high-voltage high-power direct-current transmission occasions. In a high-voltage long-distance high-power direct-current transmission project, an overhead line has obvious economy, but the direct-current side fault rate is high, and a half-bridge sub-module does not have direct-current fault clearing capacity. If short-circuit fault occurs, the fault current can be rapidly increased to dozens of times of rated current, and a direct-current circuit breaker needs to be adopted to rapidly act to isolate a fault line, remove the fault current and improve the reliability of the system. There are many schemes for clearing dc faults at present, and the schemes can be divided into the following according to the difference of main switching elements in the dc circuit breaker: mechanical dc circuit breakers, all-solid-state dc circuit breakers and hybrid dc circuit breakers. Under a higher direct-current voltage level, the direct-current circuit breaker only has a single direct-current fault removal function, cannot meet specific requirements such as dynamic current limiting and the like, and needs to be matched with a direct-current limiter for use. In the future, a plurality of problems still exist in the development of direct-current circuit breakers in multi-terminal direct-current and direct-current power grids, and the direct-current circuit breakers which have the current-limiting effect and are suitable for various fault situations are urgently needed to be researched.

Disclosure of Invention

In order to overcome the defects of the prior art, the invention provides a clamp type circuit breaker topology.

The technical scheme adopted by the invention is as follows: the low-capacitance pre-charging capacitor is connected to the fault loop, the voltage of a line on the network side is reduced to zero under the action of clamping voltage generated by charging of the low-capacitance pre-charging capacitor, and the energy consumption process is carried out after the fault is isolated, so that the coupling of fault isolation and fault energy consumption is removed.

Compared with the prior art, the invention has the advantages that:

1. when a fault occurs, a pre-charging capacitor is connected into a fault loop, the capacitor with high bearing capacity and small capacity value is used for absorbing fault energy at the converter station side and clamping voltage quickly, short-circuit energy at the line side is consumed through an energy consumption branch after the fault is isolated, the decoupling of fault isolation and fault energy consumption is realized, the energy consumption is carried out after the isolation, and the isolation and the clearing of direct-current faults can be carried out quickly and effectively;

2. the capacitor is designed by stages, so that the capacitor has a complete fault protection system and can meet the fault clearing requirement under the conditions of complex faults and systems;

3. and each branch is switched into for current limiting of fault current in breaking, so that the requirement on the circuit breaker is reduced, and the cost is reduced.

4. In a two-end converter station, a method for installing four bipolar circuit breakers is designed, fault current flowing out of a high potential point can be blocked, and wiring and installation methods of the circuit breakers and polarities of devices are designed in a distinguishing mode.

Drawings

The invention is further described below with reference to the accompanying drawings.

Fig. 1 is a schematic structural diagram of a clamp type dc circuit breaker topology;

FIG. 2 is a schematic circuit diagram during charging;

FIG. 3 is a schematic current diagram without a fault;

FIG. 4 is a schematic view of a clamping stage;

FIG. 5 is a schematic diagram of the energy consumption phase;

FIG. 6 is a schematic diagram of capacitor not being applied;

FIG. 7 is a schematic diagram of the first stage capacitive input;

FIG. 8 is a schematic diagram of the second stage capacitive input;

FIG. 9 is a third stage capacitive throw-in schematic;

FIG. 10 is a schematic diagram of the fourth stage capacitive input;

fig. 11 is a schematic view of a bidirectional breaking structure.

Detailed Description

The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application.

The topology of the step-down clamp type dc circuit breaker is shown in fig. 1. The energy-saving circuit comprises a clamping capacitor C, IGBT switch T2, a voltage division capacitor Cc, a charging resistor Rc, a charging inductor Lc, an IGBT switch T3, an energy consumption capacitor Ce, an energy consumption resistor Re and an energy consumption inductor Le.

As shown in fig. 2, when no fault occurs, normal operating current flows through the steady-state low-loss branch; it is composed of ultra fast mechanical switch (UFD) UFD1, UFD2 and IGBT switch T1.

As shown in fig. 3, a fault occurs and the fault current is diverted. The system detects the fault and sends out a command to latch T1, and the fault current is transferred to a branch consisting of T2 and a diode. UFD1 is turned off when the current through UFD1 drops to 0.

As shown in fig. 4, UFD1 is completely turned off, T2 is locked, charging starts, switch RCB is closed to connect voltage dividing capacitor Cc, charging resistor Rc and charging inductor Lc to the charging loop, and at this time, the dc line starts to charge clamping capacitor C, so that it is further charged based on the initial voltage, and the generated reverse voltage clamps the dc voltage of the converter station. While turning on T3 provides a freewheeling loop for the fault current. When the current of the clamp branch is reduced to zero, UFD2 is turned off to isolate the fault line, and the operation also needs 2-3ms of delay.

As shown in fig. 5, the process of dissipating the remaining energy of the grid-side line and the clamping stage together constitute the complete process of fault clearing. And the UFD2 is completely turned off, the T3 is locked, and an energy consumption branch consisting of an energy consumption capacitor Ce, an energy consumption resistor Re and an energy consumption inductor Le is connected, so that the process of line energy consumption is accelerated.

As shown in fig. 6, the charging capacitor C and the IGBT switch T2 are actually composed of a plurality of sets of capacitors and a plurality of sets of IGBT switches, and the current before charging the clamping capacitor C, i.e., when no capacitor is put in, flows through all the IGBTs, taking 4 sets as an example.

As shown in fig. 7, the charging process begins, latching IGBT switch Ta, and charging of the first set of capacitors into the circuit begins.

As shown in fig. 8, the charging process begins, IGBT switch Tb continues to be closed, and the second group of capacitors continues to be put into the circuit to begin charging.

As shown in fig. 9, the charging process begins, the IGBT switch Tc continues to be closed, and the third group of capacitors continues to be put into the circuit to begin charging.

As shown in fig. 10, the charging process starts, the IGBT switch Td is continuously turned off, the fourth group of capacitors is charged in the circuit, and at this time, all the clamp capacitors are charged in the circuit.

As shown in fig. 11, the wiring and installation method of the circuit breaker and the polarity of the device need to be designed differently according to the outlet position of the current converter and the directions of the positive and negative electrode lines, and the installation method of four bipolar circuit breakers between the two end converter stations is designed. When in fault, the high potential point on the positive electrode line is at the commutation side, the high potential point on the negative electrode line is at the short-circuit point, and the capacitance of the clamp voltage branch circuit is set to be in the opposite direction. The charging branch circuit and the energy consumption branch circuit are provided with grounding electrodes, the grounding electrodes can be removed by the charging branch circuit, and the positive and negative branch circuits are directly connected. The energy consumption branch can also connect the positive and negative branches, but the grounding electrode must be reserved, otherwise, an energy consumption loop cannot be formed when a single-pole grounding fault occurs. The two poles of the circuit breaker are connected, and the effect of the circuit breaker is equal to that of a circuit breaker which is independently installed on the two poles under the condition that the parameters of the two poles of the circuit breaker are strictly consistent.

As can be seen from the above detailed description, the proposed clamp-on dc circuit breaker can achieve fault isolation and decoupling of fault energy consumption in the field of high-voltage dc power transmission, and quickly and effectively isolate and remove dc faults by first isolating and then consuming energy; the fractional investment of capacitance is achieved such that the stress on the device is reduced.

Finally, it should be noted that: the described embodiments are only some embodiments of the present application and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.

Claims

1. The utility model provides a clamp voltage formula circuit breaker topology suitable for direct current fault clearance which characterized in that: the charging device comprises four branches, namely a clamping branch, a charging branch, a steady-state branch and an energy consumption branch.

2. The clamped-in dc circuit breaker topology of claim 1, wherein: the clamping branch is the most main working branch and consists of a clamping capacitor C and an IGBT switch T2. The clamping capacitors can be grouped and put into the circuit in stages, so that the surge of overvoltage and overcurrent is reduced.

The steady-state branch route is composed of an ultra fast mechanical switch (UFD) UFD1, UFD2 and an IGBT switch T1. In a steady state, normal working current flows through the branch circuit; and in case of fault, UFD1 and T1 cooperate to transfer fault current to the clamp branch, and UFD2 isolates the fault line after the fault current crosses zero.

The charging branch circuit is used for pre-charging the clamping capacitor, so that the clamping capacitor has certain initial voltage, and the fault clearing speed is further improved. The branch consists of a voltage-dividing capacitor Cc, a charging resistor Rc and a charging inductor Lc. A residual current switch (RCB) in the branch is used to switch the branch off after charging so as not to affect subsequent fault clearing operations.

The energy consumption branch circuit consists of an IGBT switch T3, an energy consumption capacitor Ce, an energy consumption resistor Re and an energy consumption inductor Le, and is responsible for providing a follow current loop for fault current in the voltage clamping process and consuming residual energy on a line after fault isolation.

3. The buck-clamp dc circuit breaker topology of claim 1, wherein: the circuits in all stages are sequentially switched into a fault circuit to meet the fault clearing requirement.

4. The buck-clamp dc circuit breaker topology of claim 1, wherein: the staged investment of the capacitor in the clamping stage greatly reduces the stress on the device, thereby reducing the impact and lowering the cost.