KR20190052940A - DC power source cutoff control apparatus - Google Patents

Abstract

The present invention relates to a DC power cutoff control apparatus, comprising: a mechanical switch provided between a DC power and a load terminal to supply or cut off power from the DC power to the load terminal; a switch driving unit for turning on or off the mechanical switch in response to a control signal; a current sensor for measuring a current supplied from the DC power to the load terminal; a controller for determining whether the measured current detected by the current sensor is greater than a reference current and controlling the switch driving unit to turn off the mechanical switch if the measured current is greater than the reference current and corresponds to a set cutoff condition; a freewheel diode connected in parallel with the mechanical switch to allow a reverse current flow of the load terminal when the mechanical switch is turned off; and a surge observer connected in series with the freewheel diode and absorbing a surge voltage when the mechanical switch is turned off. According to the present invention, the DC power cutoff control device is capable of suppressing an occurrence of arc of the mechanical switch when the mechanical switch is turned off and determining whether the mechanical switch is turned off in consideration of strength and duration of a fault current, thereby providing an advantage in that operational efficiency can be improved.

Description

Technical Field [0001] The present invention relates to a DC power source cutoff control apparatus,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a DC power shut-off control device, and more particularly, to a DC power cut-off control device that treats a fault current flowing in a DC line when a fault occurs in the DC line,

Direct current circuit breaker is used to cut off the fault current in case of line fault, overcurrent, short circuit, ground fault or over current in DC transmission line.

Low voltage DC breakers are mainly used in low voltage transmission lines or distribution lines of less than 750V of low voltage direct current (LVDC) systems.

The DC circuit breaker is equipped with a relatively inexpensive mechanical switch to block the fault current in the event of a fault in the DC line. Mechanical switches are opened to prevent fault currents in low-voltage direct current transmission (LVDC) systems or DC distribution systems to prevent them from affecting normal systems.

However, in order to interrupt the fault current, the mechanical switch can generate an arc in the terminal due to the DC voltage at the time of opening. When the arc is generated, the fault current is continuously flowed through the arc, There is a problem that can not be done.

In order to solve such a problem, Korean Patent No. 1183508 discloses a DC circuit breaker which extinguishes an arc generated in a mechanical switch by using a resonant current.

In such a conventional DC circuit breaker, in order to interrupt the fault current by cutting off the arc generated when the mechanical switch is switched in the event of a fault, the resonance current in the opposite direction is superimposed on the fault current flowing through the arc in the mechanical switch, ) Current to create an arc.

In order to effectively block the DC breaker, a method of artificially blocking the fault current through the '0' point by using the LC resonance circuit is proposed, but the disconnection speed is slow.

In order to solve these problems, a large diode and a thyristor have been developed and a circuit configuration has been proposed in which the cutoff speed is improved by combining it with a high speed mechanical circuit breaker such as an LC resonance circuit. However, The performance is insufficient at the breaking capacity, the breakdown voltage and the breaking speed.

On the other hand, in Korean Patent Laid-Open No. 10-2005-0083067 (gate cut-off circuit of voltage-driven power switching device utilizing LC resonance), an inductor, a transistor and a capacitor are connected in series to a switching element, However, there is a disadvantage in that the conduction loss is too large in normal operation.

In addition, a semiconductor circuit breaker using a gate turn-off thyristor (GTO) for subway feeder lines has been developed at home and abroad, and has a merit that a breakdown current can reach a certain value, It has not been commercialized because of the drawbacks that the loss is too large.

Even if an IGBT (Insulated Gate Bipolar Transistor) or IGCT (Insulated Gate-Commutated Thyristor), which is a recently developed large-capacity semiconductor switching device, is used, there is no economical efficiency because the conduction loss is too large.

Meanwhile, since the conventional DC circuit breakers have to resonate several times in order to generate the resonance current, the cutoff speed is slowed. Also, since one resonant circuit is connected to one mechanical switch, There is a problem that only the fault current flowing in one direction is blocked.

In addition, the conventional DC circuit breakers have a problem that the transient recovery voltage (TRV) applied between two contacts of the circuit breaker is high immediately after the breakdown current is cut off. Especially, in the high voltage DC circuit breaker, a large transient recovery voltage (TRV) is applied between the two contacts immediately after the fault current is cut off according to the circuit conditions of the system. In order to completely break the fault current, the transient recovery voltage (TRV) Should not flow.

However, since the conventional DC circuit breakers have a high transient recovery voltage (TRV), insulation breakdown may occur between the two contacts. To prevent this, a separate device, such as injecting gas, must be provided.

On the other hand, when the mechanical switch is simply turned off every time an overcurrent is applied, the operating rate is lowered due to the operation stop due to the power-off. Therefore, it is determined whether the surge current has no influence on the operation system, It is required to minimize it.

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned problems, and it is an object of the present invention to provide a DC power supply which can determine the off state of a mechanical switch in consideration of the strength and duration of a fault current, And an object thereof is to provide a shut-off control device.

In order to achieve the above object, a DC power shutdown control apparatus according to the present invention includes: a mechanical switch installed between a DC power source and a lower end to supply or cut off power from the DC power source to the lower end; A switch driver for turning on or off the mechanical switch according to a control signal; A current sensor for measuring a current supplied from the DC power supply to the negative terminal; A controller for determining whether the measured current detected by the current sensor is greater than a reference current and for controlling the switch driver to turn off the mechanical switch if the measured current is greater than a reference current and corresponds to a set break condition; A freewheeling diode connected in parallel with the mechanical switch to allow reverse current flow at the bottom of the mechanical switch when the mechanical switch is turned off; And a surge observer connected in series with the free wheel diode and absorbing a surge voltage when the mechanical switch is turned off.

And a zener diode connected in parallel with the mechanical switch.

If the measured current is greater than the reference current and less than twice the reference current, the controller waits for a first waiting time. If the measured current is greater than the reference current, the controller turns off the mechanical switch If the measuring current is less than the reference current after waiting for the first waiting time, the mechanical switch is maintained in the ON state.

Wherein the controller waits for a second waiting time set shorter than the first waiting time when the measured current is greater than twice the reference current and less than or equal to 10 times the reference current and if the measured current is greater than the reference current, And controls the switch driving unit to turn off the mechanical switch. If the measured current is less than the reference current after waiting for the second waiting time, the mechanical switch is maintained in the on state.

When the measured current is greater than 10 times the reference current and less than 100 times the reference current, the controller waits for a third waiting time set to be shorter than the second waiting time, And controls the switch driving unit to turn off the mechanical switch if the measured current is greater than the reference current, and maintains the on state of the mechanical switch when the measured current is less than the reference current after waiting for the third waiting time.

The controller may control the switch driver to turn off the mechanical switch within a preset instant if the measured current exceeds 100 times the reference current.

Preferably, the first waiting time is 500 milliseconds, the second waiting time is 100 milliseconds, the third waiting time is 10 milliseconds, and the instantaneous time is 1 millisecond.

According to the DC power shut-off control device of the present invention, it is possible to suppress the occurrence of an arc when the mechanical switch is turned off, determine the off state of the mechanical switch in consideration of the strength and duration of the fault current, .

FIG. 1 is a circuit diagram showing a direct current cutoff control apparatus according to the present invention,
FIG. 2 is a flowchart showing a mechanical switch-off determination process of the controller of FIG. 1;

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a DC power cut-off control apparatus according to a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

1 is a circuit diagram showing a direct-current power-off control apparatus according to the present invention.

1, a DC power shutdown control apparatus 100 according to the present invention includes a mechanical switch 110, a switch driving unit 120, a current sensor 130, a control unit 150, a freewheeling diode 161, A diode 162, and a zener diode 163.

Reference numeral 60 is equivalent to the effective impedance of the power supply path 120 leading from the DC power supply 10 to the lower stage 20 to which the load is connected.

The mechanical switch 110 is provided between the DC power supply 10 and the lower stage 20 so as to supply or cut off power from the DC power supply 10 to the lower stage 20. [

The mechanical switch 110 is installed in series on the power supply path 12 leading from the positive (+) terminal of the DC power supply 10 to the lower end 20 of the positive electrode part so as to be connected or disconnected from the contact 13 .

The switch driver 120 is capable of turning on or off the mechanical switch 110 so that the mechanical switch 110 is connected to or disconnected from the contact 13 according to a control signal of the controller 150. [

The switch driving unit 120 may be constructed to generate a magnetic force by a driving current applied to the controller 150 and to turn on or off a mechanical switch 110 responsive to a magnetic force.

The current sensor 130 measures a current supplied from the DC power supply 10 to the load terminal 20 and provides the measured current to the controller 150.

The current sensor 130 is connected between the DC power supply 10 and the mechanical switch 110 on the power supply path 12 leading from the positive (+) terminal of the DC power supply 10 to the lower end 20 of the positive electrode A shunt resistive element for current detection was applied.

Alternatively, the current sensor 130 may be implemented by a variety of known structures such as a method of detecting a current in a coil form on the power supply path 12 between the DC power supply 10 and the mechanical switch 110 Of course.

The freewheeling diode 161 is connected in parallel with respect to the power supply path 12 between the mechanical switch 110 and the terminal 20.

The free wheel diode 161 is also arranged such that the cathode is connected to the power supply path 12 to permit reverse current flow of the loading stage 20 together with the surge observer 162 to be described later when the mechanical switch 110 is turned off do.

In other words, the freewheeling diode 161 provides a freewheeling path along with the surge observer 162, in which the reactive impedance 60 existing on the power supply path 12 or the reactance component existing on the load 20 can be extinguished do.

The surge observer 162 is connected in series with the freewheeling diode 161 and absorbs and surges the surge voltage when the mechanical switch 110 is off.

The zener diode 163 is connected in parallel to the power supply path 12 between the mechanical switch 110 and the load terminal 20. [

This zener diode 163 absorbs the overvoltage and stabilizes the power supply circuit.

The controller 150 determines whether the measured current Id detected by the current sensor 130 is greater than the reference current Ir and if the measured current is greater than the reference current and corresponds to the set break condition, And controls the switch driver 120 to be turned off.

The control process of the controller 150 will be described with reference to FIG.

First, the controller 150 detects the measurement current Id supplied from the current sensor 130 through the power supply path 12 (step 210).

It is determined whether the measured current Id detected in step 210 is greater than the reference current Ir (step 220).

Here, the reference current Ir may be appropriately set as a reference value of the fault current for determining the protection of the load connected to the load terminal 20 and the power supply circuit.

If it is determined in step 220 that the measured current Id is larger than the reference current Ir, it is determined whether the measured current Id is twice or less than the reference current Ir (step 230).

If it is determined in step 230 that the measured current Id is equal to or less than twice the reference current Ir, after waiting for a decision on on / off of the mechanical switch 110 for a set first waiting time, (Step 240).

After step 240, it is determined whether the current measurement current Id is still greater than the reference current Ir (step 250), and if it is determined that the measured current Id is still greater than the reference current Ir, The switch driver 120 is controlled to turn off the power source.

Otherwise, if it is determined in step 250 that the measured current Id is less than or equal to the reference current Ir, the ON state of the mechanical switch 110 is maintained and the process returns to step 210.

Alternatively, if it is determined in step 230 that the measured current Id exceeds twice the reference current Ir, it is determined whether the measured current Id is less than or equal to 10 times the reference current Ir (step 270).

If it is determined in step 270 that the measured current Id is less than or equal to 10 times the reference current Ir, after waiting for a decision on on / off of the mechanical switch 110 for a set second waiting time, (Id), and returns to step 250 (step 280).

If it is determined in step 270 that the measured current Id exceeds 10 times the reference current Ir, it is determined whether the measured current Id is less than or equal to 100 times the reference current Ir (step 290).

If it is determined in step 290 that the measured current Id is less than or equal to 100 times the reference current Ir, after waiting for a decision on on / off of the mechanical switch 110 for a set third waiting time, (Id), and returns to step 250 (step 280).

Otherwise, if it is determined in step 290 that the measured current Id exceeds 100 times the reference current Ir, the process returns to step 260 to turn off the power.

Here, the third waiting time is set shorter than the second waiting time, and the second waiting time is set shorter than the first waiting time.

Preferably, the first wait time is 500 milliseconds, the second wait time is 100 milliseconds, and the third wait time is 10 milliseconds.

The power off of step 260 is processed to occur within the instantaneous time, and the instantaneous time is one millisecond.

According to the control process of the mechanical switch 110 for the fault current of the control unit 150, if the overcurrent is maintained for a short time only when the intensity of the current is large but may not substantially cause damage to the power supply circuit system By applying the cut-off condition to keep the mechanical switch 110 in the ON state, the operation maintenance efficiency can be improved.

110: Mechanical switch 120: Switch driving part
130: current sensor 150:
161: Freewheeling diode 162: Surge arrester
163: Zener diode

Claims (7)

A mechanical switch installed between the DC power source and the lower stage for supplying or blocking power from the DC power source to the lower stage;
A switch driver for turning on or off the mechanical switch according to a control signal;
A current sensor for measuring a current supplied from the DC power supply to the negative terminal;
A controller for determining whether the measured current detected by the current sensor is greater than a reference current and for controlling the switch driver to turn off the mechanical switch if the measured current is greater than a reference current and corresponds to a set break condition;
A freewheeling diode connected in parallel with the mechanical switch to allow reverse current flow at the bottom of the mechanical switch when the mechanical switch is turned off;
And a surge observer connected in series with the free wheel diode and absorbing a surge voltage when the mechanical switch is turned off. The apparatus of claim 1, further comprising a Zener diode connected in parallel with the mechanical switch. The apparatus of claim 1, wherein the control unit
Controls the switch driver to turn off the mechanical switch if the measured current is greater than the reference current and is less than twice the reference current and then the measured current is greater than the reference current after waiting for a first waiting time, When the measured current is less than the reference current after waiting for a waiting time, the controller keeps the mechanical switch on. 4. The apparatus of claim 3, wherein the control unit
When the measured current is greater than twice the reference current and less than or equal to 10 times the reference current, waiting for a second waiting time set shorter than the first waiting time, if the measured current is greater than the reference current, Off state of the mechanical switch when the measured current is less than the reference current after the standby state is maintained for the second waiting time. 5. The apparatus of claim 4, wherein the control unit
If the measured current is greater than 10 times the reference current and less than or equal to 100 times the reference current, waiting for a third waiting time set shorter than the second waiting time, if the measured current is greater than the reference current, Off state of the mechanical switch when the measured current is less than the reference current after waiting for the third waiting time. 6. The apparatus of claim 5, wherein the control unit
Wherein the control unit controls the switch driving unit such that the mechanical switch is turned off within a preset instant if the measured current exceeds 100 times the reference current. 7. The method of claim 6, wherein the first waiting time is 500 milliseconds, the second waiting time is 100 milliseconds, the third waiting time is 10 milliseconds, and the instantaneous time is 1 millisecond DC power shutdown control device.

Images