WO2019241924A1

WO2019241924A1 - Direct-current soft switching-off module

Info

Publication number: WO2019241924A1
Application number: PCT/CN2018/091942
Authority: WO
Inventors: 何曙光; 许健生
Original assignee: 何曙光; 许健生
Priority date: 2018-06-20
Filing date: 2018-06-20
Publication date: 2019-12-26
Also published as: CN109416994A

Abstract

A direct-current soft switching-off module, relating to the technical field of high-voltage direct-current circuit breakers, and capable of serving as a switch contact and a high-power direct-current contactor contact of a high-voltage direct-current system so as to achieve soft switching-off in current switching-off to eliminate electric arcs. According to the direct-current soft switching-off module, a metal contact (K1) of a switch is connected in parallel to three branch circuits, including a thermistor (RT1) and thyristor (VT11) series branch circuit, a capacitor (C1) and resistor (R11) series branch circuit, and a varistor (RV1), wherein the thyristor (VT11) can be replaced by a temperature control switch (S1); the metal contact (K1) and each parallel branch circuit are taken as one piece so as to form the direct-current soft switching-off module, and a housing and a mechanical shifting device are additionally provided, so that a switch product can be manufactured. The direct-current soft switching-off module has simple circuits, low costs of used components, a simple manufacturing process, excellent actual measurement arc extinguishing performance, and high switching-off performance.

Description

DC soft shutdown module

Technical field

The invention relates to a DC soft-shutdown module, which is used for a switch of a high-voltage DC power system, and can be used as a switch contact or a high-power DC contactor contact of a high-voltage DC power system. When the current is interrupted, a soft shutdown is performed to eliminate an arc.

Background technique

The invention belongs to the technical field of high-voltage DC circuit breakers. There are many capacitors and inductive elements in the DC power system line, such as reactors and filtering devices. The transmission line also has distributed parameter inductance and distributed parameter capacitance. When the high-current DC circuit is broken, a large amount of energy is generated and released in the form of an arc. Although the switch contacts are made of high-melting metal materials, if no measures are taken, they will still be ablated and damage the switch. DC current does not have zero crossings like AC current. The arc can be automatically extinguished at the zero crossing of the current, so it is much more difficult to eliminate the arc when breaking the DC current.

In the prior art, a measure for breaking a high-current DC circuit is to use an energy-consuming method to absorb the energy released by breaking the high-current DC circuit in a short time, such as setting an arc extinguishing grid and extending the arc; or using multiple metals The contacts are connected in series, and each metal contact is merged into a resistor and then disconnected in sequence; or a varistor is connected in parallel at the metal contact of the switch, etc .; the other is to use a forced zero crossing method and connect the switches in parallel. Capacitors and inductors in series generate self-excited oscillation when breaking a large current, and artificially create a zero crossing of the current to extinguish the arc.

Although the industry has developed and produced a variety of high-voltage DC circuit breakers using the above methods, their structures are relatively complex and costly. Some products have a difficult manufacturing process, and some have troublesome operating procedures, which need to be improved.

Summary of the Invention

The invention relates to a DC soft-off module, which is used for a switch of a high-voltage DC power system. The switch includes a switch contact K1 and a DC soft-off circuit connected in parallel to both ends (1) (2) of the switch contact K1. One end (1) of K1 is connected to the anode X1 of a high-voltage DC power supply, the other end (2) is connected to one end of the electric load RL, and the other end of the load RL is connected to the negative electrode X2 of the high-voltage DC power supply.

According to an embodiment of the present invention, the DC soft-off circuit includes two branches:

The first branch includes a thermistor RT1 and a thyristor VT11 connected in series. One end of the thermistor RT1 is connected to one end (1) of the switch contact K1, the other end of the thermistor RT1 is connected to the anode of the thyristor VT11, and the cathode of the thyristor VT11. Connect the other end (2) of switch contact K1;

The second branch includes a capacitor C1 and a resistor R11 connected in series, and a thyristor VT21 and resistors R21 and R31. One end of the capacitor C1 is connected to one end (1) of the switch contact K1, and the other end of the capacitor C1 is connected to one end of the resistor R11. The other end of the resistor R11 is connected to the other end of the switch contact K1 (2). The anode of the thyristor VT21 is connected to the series node (3) of the capacitor C1 and the resistor R11. The resistor R31 and the thyristor VT21 are connected between the anode and the control electrode of the thyristor VT21. The cathode of the thyristor is connected to one end of the resistor R21, the other end of the resistor R21 is connected to the other end of the switch contact K1 (2), and the serial node (4) of the cathode of the thyristor VT21 and the resistor R21 is connected to the control electrode of the thyristor VT11;

Among them, the thyristor VT1 maintains a current greater than 10 mA;

Among them, the thermistor RT1 selects a positive temperature coefficient PTC element.

According to another embodiment of the present invention, the DC soft-off circuit further includes a varistor RV1 connected in parallel to both ends (1) (2) of the switch contact K1.

According to another embodiment of the present invention, the DC soft-off module includes a switch contact K1, and a plurality of DC soft switches as described above connected in series at both ends (1) (2) of the switch contact K1. Shut down the circuit.

According to another embodiment of the present invention, the DC soft-off circuit includes two branches:

The first branch includes a thermistor RT1 and a temperature control switch S1 connected in series, one end of the thermistor RT1 is connected to one end (1) of the switch contact K1, and the other end of the thermistor RT1 is connected to one end of the temperature control switch S1. The other end of the temperature control switch S1 is connected to the other end (2) of the switch contact K1;

The second branch includes a capacitor C1 and a resistor R11 connected in series. One end of the capacitor C1 is connected to one end (1) of the switch contact K1, the other end of the capacitor C1 is connected to one end of the resistor R11, and the other end of the resistor R11 is connected to the switch contact K1. The other end (2).

The DC soft-off module designed by the invention has simple circuit, low cost of components and components, simple manufacturing process, rapid and effective arc-extinguishing, and excellent performance.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a circuit diagram of a first embodiment of a DC soft-off module of the present invention.

FIG. 2 is a circuit diagram of a second embodiment of the DC soft-off module of the present invention.

FIG. 3 is a circuit diagram of a third embodiment of the DC soft-off module of the present invention.

FIG. 4 is a circuit diagram of a fourth embodiment of the DC soft-off module of the present invention.

detailed description

The embodiments are used to explain the accompanying drawings and illustrate the invention of the present invention.

Referring to FIG. 1, a DC soft-off module of the present invention includes a metal contact K1 of a switch and a DC soft-off circuit connected in parallel to both ends (1) (2) of the switch contact K1. In Figure 1, X1 and X2 are high-voltage DC power supplies, in which X1 terminal is a positive electrode and X2 terminal is a negative electrode. One end (1) of the switch contact K1 is connected to the anode X1 of the high-voltage DC power supply, the other end (2) of the switch contact K1 is connected to one end of the electric load RL, and the other end of the load RL is connected to the negative electrode X2 of the high-voltage DC power supply to contact The head K1 is opened or closed to control the power consumption of the load RL.

The DC soft-off circuit in parallel at (1) and (2) of switch contact K1 includes three branches:

The first branch is composed of the thermistor RT1 and the thyristor VT11 in series, that is, one end of the thermistor RT1 is connected to one end (1) of the switch contact K1, and the other end of the thermistor RT1 is connected to the anode a11 of the thyristor VT11 and the thyristor VT11. The cathode b11 is connected to the other end (2) of the switch contact K1. The thermistor RT1 selects a PTC element with a positive temperature coefficient. The "maintenance current" Ih of the thyristor VT11 must be greater than 10mA.

The second branch is composed of a capacitor C1 and a resistor R11 in series, that is, one end of the capacitor C1 is connected to one end of the switch contact K1 (1), the other end of the capacitor C1 is connected to one end of the resistor R11, and the other end of the resistor R11 is connected to the switch contact K1. At the other end (2), the thyristor VT21 and the resistors R21 and R31 are used to trigger the thyristor VT11. The anode a21 of the thyristor VT21 is connected to the series node (3) of the capacitor C1 and the resistor R11, and the control electrode c21 of the thyristor VT21 and the resistor R31 is connected to node (3) in series, the cathode b21 of thyristor VT21 is connected to one end of resistor R21, the other end of resistor R21 is connected to the other end of switch contact K1 (2), and the series connection node of cathode of thyristor VT21 and resistor R21 (4) The control electrode c11 of the thyristor VT11 is connected.

Thyristors VT11 and VT21 are Silicon Controlled Rectifiers (SDRs). They are high-power semiconductor devices with a four-layer structure with three PN junctions. They are also called thyristors. The thyristors VT11 and VT21 have two turn-off conditions: one is to remove the trigger signal of the control electrode, and the other is that the current flowing through the thyristor is less than its sustain current Ih.

The third branch is composed of a separate varistor RV1, that is, one end of the varistor RV1 is connected to one end (1) of the switch contact K1, and the other end of the varistor RV1 is connected to the other end (2) of the switch contact K1. The varistor is preferably a zinc oxide arrester. If the current cut off by contact K1 is not too large and the voltage of the DC power supply is not very high, this branch can be omitted.

The principle of arc elimination is as follows:

1) When the switch contact K1 is closed, the load RL is energized and operates normally, the voltage on the capacitor C1 is zero, and no power is stored.

2) If the switch contact K1 is opened by pulling the brake, there will be zero voltage across the contact at the moment of disconnection, because the voltage of C1 cannot be abruptly changed. Due to the transient process of the circuit, the large current on the load RL will not disappear instantly but will last for a period of time. At this time, the high-voltage DC power supply charges the capacitor C1 through the load RL and the resistor R11 to limit the current, which also limits the rate of voltage rise across the switch contact K1.

3) At the moment when the switch contact K1 is turned off, a pulse voltage is generated on the resistor R11, which is added to the thyristor VT11 control electrode through the thyristor VT21, and the thyristor VT11 is quickly turned on.

4) After capacitor C1 is fully charged, the voltage on C1 can reach the voltage of the high-voltage DC power supply, the divided voltage on resistor R11 drops to zero, the current flowing through VT21 is less than its sustaining current Ih21, and the voltage of its control pole c21 is It also drops to zero, causing VT21 to shut down. Because the VT21 is turned off, the voltage of the control pole c11 of the VT11 is zero, the trigger signal of the VT11 control pole c11 is removed, and one of the VT11 shutdown conditions is satisfied.

5) After the thyristor VT11 is turned on, the large current on the load RL is directed to the series branch of the thermistor RT1 and the thyristor VT11. Initially, the thermistor RT1 is cold, and its resistance value is low, so the current flowing through the series branch of the thermistor RT1 and the thyristor VT11 is large, and the energy released by the circuit breaker is quickly consumed by the thermistor RT1. It is beneficial for the metal contact to be disconnected. The thermistor RT1 is energized and the temperature rises. Because the PTC material has a positive temperature coefficient, its resistance value continues to rise, and the current flowing through it decreases. Therefore, it is called "soft shutdown". No arc or only a small arc is generated, ensuring the safe breaking of metal contacts. When more than the switching temperature of the PTC material (known as Curie temperature) exhibits a step increase its resistance, the resistance value theoretically up to 10 ¹⁰ ohms, the actual resistance of up to ¹⁰⁶ ohms, so that the flow through the heat-sensitive The current of the series branch of the resistor RT1 and the thyristor VT11 will eventually drop below 10mA. Because the "sustain current" Ih11 of the thyristor VT11 is selected to be greater than 10mA, the current flowing through the thyristor VT11 is less than the "sustain current" 10mA value, which In view of the second condition that the thyristor is turned off, the thyristor VT11 cannot maintain conduction and turns itself off, and the pull-off turn-off is completed. After the thermistor RT1 is powered off, it cools down and returns to its original state.

6) After closing again, the switch contact K1 is closed, the capacitor C1 is discharged to the resistor R11 through the contact, and the voltage on the capacitor C1 drops to zero, preparing for the next opening.

7) With the third branch of the varistor RV1, it can absorb the overvoltage generated during the transition of the brake. If the current cut off by contact K1 is not too large, such as less than 20 amps, the voltage of the DC power supply is not very high, such as below 2000 volts, this branch can be omitted.

This solution adopts the "non-electrically isolated soft-off" method, the circuit structure is simple, and the arc generated when the switch is turned off can be effectively extinguished.

Referring to FIG. 2, in a second embodiment, the DC soft-off module of the present invention includes a switch contact K1 and a DC soft-off circuit connected in parallel to both ends (1) (2) of the switch contact K1. Different from the first solution, it replaces the thyristor VT11 with a temperature-controlled switch S1, and naturally does not need a trigger circuit including the thyristor VT21, and the entire circuit is simpler.

The temperature control switch S1 is a thermostat that uses a bimetal sheet as a temperature sensing component.When the bimetal sheet is in a normal state during normal operation, the switch contacts are closed or opened.When the temperature reaches the operating temperature, the bimetal When the film is heated, it generates internal stress and moves quickly, opening or closing the contacts, cutting or connecting the circuit, thereby controlling the temperature. When cooled to the reset temperature, the contacts are closed or opened automatically or manually to resume normal working conditions.

There are various types of temperature control switches. The switch contacts are normally closed (when the operating temperature is lower, the switch contact is closed, and when the operating temperature is reached, the switch contact is open,) and normally open (below At the operating temperature, the switch contact is in the open state. When the operating temperature is reached, the switch contact is in the closed state); there are automatic reset type (the switch contact state is restored automatically when cooled to the reset temperature) and manual reset type (cooled When the reset temperature is reached, the state of the switch contact must be restored manually). Due to the advancement of manufacturing process technology, the operating temperature of the temperature control switch can be selected by the customer, and the operating temperature accuracy is relatively high. The best absolute error can reach ± 2 ° C, and generally can reach ± 5 ° C, which meet the design requirements of this scheme. This scheme is designed to select the switch contact normally closed and manual reset type.

The DC soft-shutdown module described above is used for high-voltage DC power supply, where X1 terminal is positive and X2 terminal is negative. The DC soft-off circuit in parallel at (1) and (2) of switch contact K1 includes three branches:

The first branch is composed of the thermistor RT1 and the temperature control switch S1 in series, that is, one end of the thermistor RT1 is connected to one end (1) of the switch contact K1, and the other end of the thermistor RT1 is connected to one end of the temperature control switch S1. The other end of the temperature control switch S1 is connected to the other end (2) of the switch contact K1.

The second branch is composed of a capacitor C1 and a resistor R11 in series, that is, one end of the capacitor C1 is connected to one end of the switch contact K1 (1), the other end of the capacitor C1 is connected to one end of the resistor R11, and the other end of the resistor R11 is connected to the switch contact K1. At the other end (2), this branch acts as an absorption circuit, so that the switch contact K1 is basically opened at the zero voltage state.

The third branch is composed of a separate varistor RV1, that is, one end of the varistor RV1 is connected to one end (1) of the switch contact K1, and the other end of the varistor RV1 is connected to the other end (2) of the switch contact K1. The varistor is preferably a zinc oxide arrester. Similarly, if the current cut off by contact K1 is not too large and the voltage of the DC power supply is not very high, this branch can be omitted.

The principle of arc elimination is similar to the first solution described above, and it is briefly described as follows: After the brake is opened, because the temperature control switch S1 is closed at the initial state, the large current on the load RL is directed to the thermistor RT1 and the temperature control switch. S1 is connected in series. The thermistor RT1 is energized and the temperature rises. The heat emitted by the thermistor heats the temperature control switch S1. After reaching the operating temperature of the temperature control switch, the switch contact of the temperature control switch S1 changes from the closed state to the open state, and the branch is completely broken. Electricity, the brake is completed. After power failure, the temperature of the thermistor RT1 and the temperature control switch S1 decreases, the thermistor RT1 returns to a low resistance state, and the temperature control switch S1 is restored by the mechanical toggle device when the switch is closed, in preparation for the next trip. .

This solution adopts the "electrically isolated soft-off" method, the circuit structure is simple, and the arc generated when the switch is turned off can be effectively extinguished.

To sum up, the common features of the above two embodiments of the DC soft-shut-off module of the present invention are: a plurality of branches are connected in parallel to the metal contacts of the switch, and the metal contacts and each parallel branch as a whole become a DC soft-shutdown module .

1. In the first embodiment: three branches are connected in parallel to the switch contact K1, the first branch is composed of a thermistor RT1 and a thyristor VT11 in series; the second branch is composed of a capacitor C1 and a resistor R11 connected in series, and then Thyristor VT21 and resistors R21 and R31 form a branch, which is connected in parallel with resistor R11, and connects the thyristor VT21 and resistor R21 in series with the control pole of thyristor VT11; the third branch is composed of a separate varistor RV1.

The specific circuit connection method is: one end of the thermistor RT1 is connected to one end of the switch contact K1 (1), the other end of the thermistor RT1 is connected to the anode of the thyristor VT11, and the cathode of the thyristor VT11 is connected to the other end of the switch contact K1 ( 2). One end of capacitor C1 is connected to one end of switch contact K1 (1), the other end of capacitor C1 is connected to one end of resistor R11, the other end of resistor R11 is connected to the other end of switch contact K1 (2), and the anode of thyristor VT21 is connected to The series node (3) of capacitor C1 and resistor R11, the resistor R31 is connected between the anode and control electrode of thyristor VT21, the cathode of thyristor VT21 is connected to one end of resistor R21, and the other end of resistor R21 is connected to the other end of switch contact K1 (2 ), The serial node (4) of the cathode of thyristor VT21 and resistor R21 is connected to the control pole of thyristor VT11; one end of varistor RV1 is connected to one end (1) of switch contact K1, and the other end of varistor RV1 is connected to switch contact The other end of K1 (2).

If the current cut off by contact K1 is not too large and the voltage of the DC power supply is not very high, the varistor RV1 can be omitted. The thermistor RT1 selects a PTC element with a positive temperature coefficient. The maintenance current of the thyristor VT11 must be greater than 10mA.

2. In the second embodiment: three branches are connected in parallel to the switch contact K1 of the switch, the first branch is composed of a thermistor RT1 and a temperature control switch S1 in series; the second branch is composed of a capacitor C1 and a resistor R11 The third branch is composed of a separate varistor RV1. Of course, if the current cut off by the contact K1 is not too large, the voltage of the DC power supply is not very high, and the varistor RV1 can be omitted.

The specific circuit connection method is: one end of the thermistor RT1 is connected to one end of the switch contact K1 (1), the other end of the thermistor RT1 is connected to one end of the temperature control switch S1, and the other end of the temperature control switch S1 is connected to the switch contact The other end of K1 (2). One end of capacitor C1 is connected to one end of switch contact K1 (1), the other end of capacitor C1 is connected to one end of resistor R11, the other end of resistor R11 is connected to the other end of switch contact K1 (2), and one end of varistor RV1 is connected One end (1) of the switch contact K1, and the other end of the varistor RV1 is connected to the other end (2) of the switch contact K1.

If the current cut off by contact K1 is not too large and the voltage of the DC power supply is not very high, the varistor RV1 can be omitted. The temperature control switch S1 selects the switch contacts as a normally closed and manual reset type.

FIG. 3 and FIG. 4 show embodiments of the DC soft-off module of the present invention, which are based on the first and second embodiments, respectively. Referring to FIG. 3 and FIG. 4, the DC soft-off module in this embodiment is connected in series to a plurality of switching contacts K1 by a plurality of DC soft-off branches in series. Can work in higher voltage circuits. Current components, such as the varistor RV, thyristor VT, capacitor C, and resistor used in the present invention, usually have an operating voltage of about 1000V. If it is greater than 1000V, it is difficult to purchase and the price is high. If multiple branches are used in series, the voltage required for each branch will be reduced, and the withstand voltage of the components used will also be reduced. For example, if K1 needs to be divided into 10KV voltages, then using 10 DC soft-shut-down branches with a working voltage of 1KV in series can apply the working conditions of K1, and so on.

The DC soft-off module of the present invention has simple circuit, low cost of components, simple manufacturing process, rapid and effective arc-extinguishing, and excellent performance. The DC soft-off module of the present invention can be made into a switch product by adding a casing and a mechanical toggle device.

Claims

A DC soft-shutdown module for a switch of a high-voltage DC power system. The switch includes a contactor K1 and a DC soft-off circuit connected in parallel to both ends (1) (2) of the switch contact K1, and one end of the switch contact K1. (1) Connect the anode X1 of a high-voltage DC power supply, and the other end (2) Connect one end of an electrical load RL, and the other end of the load RL is connected to the negative electrode X2 of the high-voltage DC power supply. The DC soft-off circuit includes two branches :

The first branch includes a thermistor RT1 and a thyristor VT11 connected in series. One end of the thermistor RT1 is connected to one end (1) of the switch contact K1, the other end of the thermistor RT1 is connected to the anode of the thyristor VT11, and the cathode of the thyristor VT11. Connect the other end (2) of switch contact K1;

The second branch includes a capacitor C1 and a resistor R11 connected in series, and a thyristor VT21 and resistors R21 and R31. One end of the capacitor C1 is connected to one end (1) of the switch contact K1, and the other end of the capacitor C1 is connected to one end of the resistor R11. The other end of the resistor R11 is connected to the other end of the switch contact K1 (2). The anode of the thyristor VT21 is connected to the series node (3) of the capacitor C1 and the resistor R11. The resistor R31 and the thyristor VT21 are connected between the anode and the control electrode of the thyristor VT21. The cathode of the thyristor is connected to one end of the resistor R21, the other end of the resistor R21 is connected to the other end of the switch contact K1 (2), and the serial node (4) of the cathode of the thyristor VT21 and the resistor R21 is connected to the control electrode of the thyristor VT11;

Among them, the thyristor VT1 maintains a current greater than 10 mA;

Among them, the thermistor RT1 selects a positive temperature coefficient PTC element.
The DC soft-shutdown module according to claim 1, wherein the DC soft-shutdown circuit further comprises a varistor RV1 connected in parallel at both ends (1) (2) of the switching contact K1.
A DC soft-off module for a switch of a high-voltage DC power system, comprising a switch contact K1, and a plurality of serially connected two ends (1) (2) of the switch contact K1 as claimed in claim 1 or 2. DC soft shutdown circuit described above.
A DC soft-shutdown module for a switch of a high-voltage DC power system, comprising a switch contact K1 and a DC soft-shutdown circuit connected in parallel to both ends (1) (2) of the switch contact K1, and one end of the switch contact K1 (1) Connect the anode X1 of a high-voltage DC power supply, and the other end (2) Connect one end of an electrical load RL, and the other end of the load RL is connected to the negative electrode X2 of the high-voltage DC power supply. The DC soft-off circuit includes two branches :

The first branch includes a thermistor RT1 and a temperature control switch S1 connected in series, one end of the thermistor RT1 is connected to one end (1) of the switch contact K1, and the other end of the thermistor RT1 is connected to one end of the temperature control switch S1. The other end of the temperature control switch S1 is connected to the other end (2) of the switch contact K1;

The second branch includes a capacitor C1 and a resistor R11 connected in series. One end of the capacitor C1 is connected to one end (1) of the switch contact K1, the other end of the capacitor C1 is connected to one end of the resistor R11, and the other end of the resistor R11 is connected to the switch contact K1. The other end (2).
The DC soft-off module according to claim 4, wherein the DC soft-off circuit further comprises a varistor RV1 connected in parallel to both ends (1) (2) of the switch contact K1.
A DC soft-off module for a switch of a high-voltage DC power system, comprising a switch contact K1 and a plurality of serially connected two ends (1) (2) of the switch contact K1 as claimed in claim 4 or 5. DC soft shutdown circuit described above.