WO2016043508A1

WO2016043508A1 - Apparatus and method for cutting off direct current

Info

Publication number: WO2016043508A1
Application number: PCT/KR2015/009685
Authority: WO
Inventors: 이우영; 박상훈; 송기동; 장현재; 정진교
Original assignee: 한국전기연구원
Priority date: 2014-09-18
Filing date: 2015-09-15
Publication date: 2016-03-24
Also published as: KR20160033438A; KR101641511B1

Abstract

The present invention relates to an apparatus and a method for cutting off direct current, and more preferably, to an apparatus and a method for cutting off direct current which can cut off high-voltage direct current quickly, without system operation difficulties, in a direct current transmission system using a voltage source converter which requires a far faster cut-off time compared to a conventional current source converter system, wherein the arc of a high-speed mechanical switch during contact parting is suppressed by applying reverse current to the high-speed mechanical switch when a current cut-off condition of a high-voltage transmission system occurs.

Description

Apparatus and Method for Blocking DC Current

The present invention relates to a DC current blocking device and method, and more preferably, it is difficult to operate a high voltage DC current in a DC transmission system using a voltage converter that requires a significantly faster breaking time than a conventional current converter. The present invention relates to a DC current blocking device and method that can be quickly cut off.

DC current system using voltage converters has been attracting much attention in the future. In case of an accident in such a system, the magnitude of the accident current increases rapidly. Is a serious problem.

The use of semiconductor switching device may be a good alternative to perform the fast disconnection, but due to the high power loss and the economical difficulty according to the system configuration, the hybrid type blocking which uses a mechanical switch and a semiconductor switch together in recent years There are a lot of ways. The development trend of DC blocking technology for HVDC can be classified into two types. Firstly, DC current blocking is the responsibility of the semiconductor switch, and transient voltage applied after the blocking is the DC switch. There is a method that separates the required current and voltage characteristics from each other, and secondly, a mechanical circuit breaker is used. The manner in which the device is applied is suggested.

The present invention relates to the latter manner, which is known in the prior art relating to this manner, which is published in WO2013 / 045238 (Document 1). In the blocking scheme proposed in Document 1, a capacitor installed as a circuit breaker auxiliary device is always charged to artificially generate a current zero for DC current blocking. In addition, the circuit breaker main elements connected to this capacitor also maintain the same voltage at all times, which is disadvantageous to the reliability of the lifetime due to voltage stress.

In the first method described above, the main elements of the DC circuit breaker are installed at the point where high voltage is applied, but the voltage is not applied to the component itself. It is a method that should be used in a charged state, and it is required to solve the above problem.

In order to minimize the withstand voltage stress caused by the application of voltage to the components of the DC circuit breaker, the DC current interruption device and method are operated in a state in which the voltage is not applied at all times and the voltage is applied only when the circuit breaker operation is required. It is.

A DC current interruption device, comprising: a main interrupter (10) configured in a form in which current limiting inductances (102, 104) are connected in series to a high speed mechanical switch (101, 103); A series connection part of an auxiliary interrupter 20 part and a reverse current

conduction line part

30 and 60 installed on the circuit connected in parallel with the main interrupter part to be connected in parallel with the high speed

mechanical switches

101 and 103; Auxiliary breaker 20 and the main breaker 20 is installed to be connected in parallel to the series connection of the high-speed mechanical switches (101, 103) and the current limiting inductance (102, 104) in parallel with the main breaker (10) A series connection part of the

charging line parts

40 and 70; It characterized in that it comprises an auxiliary charging line unit 50 for connecting the connection point of the reverse current conducting

line unit

30, 60 and the main

charging line unit

40, 70 of the auxiliary blocking unit 20 with the ground side. Provide DC blocking device.

In addition, the auxiliary blocking unit 20 is characterized in that the charge voltage polarity inversion circuit in which the inductance 204 and the thyristor 205 is connected in series to the voltage charging capacitor 201 for generating a reverse current is connected in parallel It provides a DC circuit breaker.

In addition, the auxiliary blocking unit 20 is connected to the surge arrester 207 in parallel with a series connection portion in which the voltage charging capacitor 201 and the reverse current adjusting resistor 202 for generating a reverse current is connected in series. It provides a DC circuit breaker.

In addition, the auxiliary blocking unit 20 provides a DC blocking device characterized in that the discharge resistor 209 for discharging the residual voltage of the capacitor 201 after the blocking operation is connected to the capacitor 201 in parallel.

In addition, the main

charging line unit

40, 70 is composed of the

diode

401, 701 and the charging resistors (402, 702) in series, through which the inductance (102, 104) and the high-speed mechanical switch (101, 103) It provides a DC blocking device, characterized in that the auxiliary breaker 20 is connected in parallel to the series connection of the).

In addition, the reverse current conducting

line unit

30, 60 is composed of a thyristor (301, 601) through which the auxiliary breaker 20 is connected to the mechanical switch (101, 103) in parallel Provide a blocking device.

In addition, the auxiliary charging line unit 50 is a mechanical switch 502 and the charging resistor 501 is connected in series, providing a DC current blocking device, characterized in that located between the auxiliary breaker 20 and the ground side. do.

In addition, it provides a DC circuit breaker characterized in that to connect the DC circuit breaker structure in a symmetrical form with respect to the auxiliary circuit breaker 20 for bidirectional current blocking.

In addition, in the DC current blocking method, the high speed mechanical switch (101, 103) and the current limiting inductance (102, 104) is formed in the form of a series connected in series; A series connection part of an auxiliary interrupter 20 part and a reverse current

conduction line part

mechanical switches

charging line parts

40 and 70; In a circuit including a secondary charging line portion 50 for connecting a connection point between the reverse current conducting

line portion

30, 60 of the auxiliary breaker 20 and the main

charging line portion

40, 70 with the ground side, a Determining the blocking condition according to the DC current; b) charging the capacitor according to the blocking condition of step a); c) when the capacitor is charged by the step b), operating the thyristor of the reverse current conducting line part while opening the high speed mechanical switch to generate a current zero in the high speed mechanical switch. A blocking condition of a provides a DC current blocking method comprising a1) a DC current blocking condition in a normal current state and a2) a current rising condition by an accident current.

Further, in the step of generating a current zero in the high speed switch of step c),

The charging voltage of the capacitor 201 is reversed by the turn-on operation of the thyristor 205, and the

thyristors

301 and 601 of the reverse current conducting

line units

30 and 60 are inverted. It provides a direct current blocking method comprising the step of applying a reverse current to the high-speed mechanical switch (101, 103) through a turn-on operation of.

In addition, in step b), when the current rise condition occurs due to the fault current, the capacitor 201 of the auxiliary breaker 20 is charged by the induced voltage generated in the current limiting

inductances

102 and 104, or the normal state. When the DC current blocking condition occurs in the current state provides a DC current blocking method characterized in that the capacitor 201 of the auxiliary blocking unit 20 is charged through the auxiliary charging line 50.

In addition, in the case of charging the capacitor 201 of the auxiliary breaker 20 through the auxiliary charging line 50, after the switch 502 is charged to the line voltage and the load current is cut off the switch ( 502) provides a direct current blocking method characterized by a method of reducing the open state.

In addition, when the reverse current is blocked, the voltage charging of the capacitor 201 is made by the voltage applied to the inductance 104 installed on the left side, and the main charging line part 70 installed in a symmetrical position with respect to the auxiliary breaker 20. ) And a direct current blocking method using a reverse current conducting line unit 60 to block direct current.

(Favorable effect)

According to the DC current blocking device and method of the present invention, the capacitor was required to maintain the state of charge at all times by applying a blocking method that can separately deal with each case by applying the characteristics of the target breaking current, that is, the fault current and the load current. It can be charged only when the breaker operation is required to perform the blocking operation.

The DC current blocking device of the present invention can minimize the stress due to voltage applied to the circuit breaker components, and may have advantages in terms of breaker life and maintenance, and is a hybrid DC circuit breaker having high speed breaking characteristics. It can be usefully applied to HVDC transmission system operated by type converter.

FIG. 1 shows a circuit diagram constituting a one-way DC current breaker.

2 shows a circuit diagram constituting a bidirectional DC current interruption device.

3 shows the values of different fault currents and steady currents over time.

4 shows a flowchart of the DC current interruption method.

5A shows the voltage value in the section showing the discharge of the capacitor 201.

FIG. 5B shows a voltage value at which a high voltage is applied to the capacitor polarity inversion and the fast switch 101 by the voltage V102 applied to the inductance 102.

5C shows an enlarged view of section T _A 2 and section T _A 3 of FIG. 5B.

FIG. 5D is an enlarged view of FIG. 5B, which illustrates a current flowing through the thyristor 301 and a voltage generation time flowing through the high speed switch 101 according to sections t _A 3 and t _A 4.

FIG. 6A shows voltage and current values applied to respective components when the circuit in which the normal current is energized is cut off.

FIG. 6B shows the polarity inversion of the capacitor charged when the circuit in which the normal current is energized and the voltage value applied to the fast switch.

FIG. 6C shows an experimental value in which the transient voltage V101 is applied between the poles of the high speed mechanical switch after the arc arc extinguishes as a current zero is generated in the high speed mechanical switch by reverse current injection.

FIG. 6D shows a current flowing through the thyristor 301 and a voltage generation point flowing through the high speed switch 101.

Hereinafter, with reference to the accompanying drawings to be described in detail with reference to a preferred embodiment of the present invention.

The present invention relates to a DC current interruption device and method having a high-speed interruption function suitable for the protection of the HVDC transmission system employing a voltage converter system.

The present invention relates to a method of completing the blocking by generating a current zero in the blocking unit through reverse current injection, the conventional methods for this is to use the charging energy in the state that is always charged to the capacitor installed in the blocking unit The breaker components are operated under voltage stress at all times.

In the present invention, in order to minimize such voltage stress, a method of charging a capacitor only at the time of operation of the circuit breaker may be adopted, thereby reducing the existing voltage stress. In addition, by separating the fault current blocking and the load current blocking by introducing an independent capacitor charging method to provide a technology that can perform the fault current as well as the load current blocking.

1 shows a configuration of a DC current interruption device as a preferred embodiment of the present invention. The main breaker 10 which is responsible for energizing current in a steady state is configured in a form in which the current limiting inductance 102 and the high speed

mechanical switches

101 and 102 are connected in series. Then, the auxiliary breaker 20, the reverse current conduction line 30, and the main charging line 40 are connected to the main breaker 10 and the parallel circuit, and the auxiliary charge line 50 is connected in series with the main charger. Connect it to ground.

The auxiliary blocking unit 20 is a capacitor charging voltage polarity inversion circuit centering on the capacitor 201 and the inductance 204 and the thyristor 205 are connected in parallel with the capacitor 201 in series, and the capacitor 201 The surge arrester 207 is connected in parallel with the excitation capacitor 201 in order to limit the charging voltage of the voltage below a predetermined voltage. After the breaker operation ends, the remaining voltage of the capacitor 201 is discharged to initialize the breaker so that the discharge resistor 209 may be directly connected in parallel with the capacitor so that the discharge resistor 209 may be performed without an operation procedure for separate discharge.

When an accident current occurs on the DC line, a constant voltage is induced in the current limiting inductance 102, and the capacitor 201 is charged to the capacitor 201 through the main charging line part 40 using the induced voltage. . In this case, the time required for charging is mainly adjusted due to the charging resistance 402 of the main charging line part 40. As described above, the time required for charging the capacitor is illustrated in FIGS. 5 to 6.

However, in order to cut off the load current in the normal state, since there is almost no current change in the normal state, the induced voltage is not generated in the current limiting inductance 102, and thus, the line grid voltage is used through the auxiliary charging line unit 50. The capacitor 201 is charged. At this time, the switch 502 is turned on to be made through the charging resistor 501.

The capacitor 201 charged according to each condition is then immediately reversed through the

polarity inversion circuits

204 and 205, and the voltage polarity of the capacitor 201 is reversed. By operating the thyristor 301, the high speed

mechanical switches

101 and 103 are applied to the high speed

mechanical switches

101 and 103 according to the current direction in the opposite direction to the current to be cut off. In the case of the capacitor 201 in which the polarity is inverted as described above, when the current is applied to the thyristor 204, the polarity of all capacitors is inverted. 5B and 6B, the polarities of the capacitor voltages of V _A 201 and V _B 201 are reversed after the application of I _A 204 and I _B 204. Further, FIGS. 5 to 6 show voltage values and current values applied to the components with time, respectively, when the current zero point is formed.

As described above, when the zero point is generated in the high-speed mechanical switch and the arc is extinguished, the time point at which the reverse current is adjusted should be adjusted to maintain the inter-pole distance sufficient to withstand the transient voltage generated by the current interruption. That is, when the current energization through the high-speed mechanical switches (101, 103) is finished, the electrical energy accumulated in the DC line charges the capacitor 201 and excessive charging voltage is generated. When the voltage rises, it is limited through the surge arrester 207. That is, the line energy generated above a certain voltage is absorbed through the surge arrester 207, and the current decreases, and the breaking action is finally completed by the high speed

mechanical switches

101 and 103 at the current zero point. When the current interruption is completed, the residual voltage present in the capacitor 201 is automatically discharged through the discharge resistor 209 and is ready for the next operation.

In addition, as shown in FIG. 2, the auxiliary blocking unit 20 is installed in a symmetrical structure with respect to the embodiment of FIG. 1, which is intended to include a blocking characteristic for bidirectional current. The inductance 104, reverse current conducting line portion 60, and main charging line portion 70 substitute for the functions of those having the same function, respectively, and the main interruption portion 10 also replaces the function of the symmetrical elements. do.

3 shows a comparison between the fault current (case 2) and the load current (case 1). The fault current has a characteristic that the current magnitude increases with time and the load current maintains a constant current magnitude regardless of time. Seems. This means that in the case of load current interruption, the interruption characteristics do not depend on the time taken for interruption, but in case of fault current, the interruption must be made within a limited time (TB) from the time of the accident. If the interruption time passes a certain time after the accident occurs, the fault current increases and the interruption cannot be performed. Therefore, the current interruption time becomes an important factor in the occurrence of an accident current which is the object of the present invention. Therefore, the blocking time of FIG. 6A has a relatively long time compared to the blocking time of FIG. 5A. This is because the blocking must be performed within a limited time from the occurrence of the fault current.

4 shows a flowchart of a DC current interruption method using the above-described interruption device. In operation S101, a blocking condition according to an initial DC current input may be determined. The DC current blocking condition may include an accident current generation condition and a DC current blocking signal input condition (S101).

When the DC current blocking condition is satisfied, the capacitor charging according to the blocking condition is performed. When the DC current is blocked by the accidental current, the capacitor is charged through the induced voltage by the inductance, and when the DC current is interrupted by the DC signal, the switch 502 is placed in the auxiliary charging line part 50 to inject the resistor 501. Charging is performed through the configuration of (S102)

Inverting the polarity of the charged capacitor (S103) and energizing the current in the reverse current direction of the high-speed mechanical switch, and through the reverse current to form a current zero point in the high-speed mechanical switch stage and performs the opening of the high-speed switch ( S104).

When the opening of the high speed switch is greater than or equal to a certain distance, the main interrupter through which the DC current is energized is opened. Therefore, the blocking of the current is completed through the DC current breaker (S105). After the blocking of the current is performed, the step of discharging the residual voltage of the capacitor is performed (S106), and preparation for charging according to the following operation is performed.

Figure 5 shows the main voltage and current signal when the fault current blocking of the present invention. t _A 1 and t _A 2 represent the charging section T _A 1 of the capacitor 201 to allow the capacitor to be sufficiently charged during this period. In each case, t _A 1 represents the time of occurrence of an accident current and the time of loading and closing command. Interval T _A 2 is the timing of the polarity of the terminal voltage of the capacitor inverted by the polarity inverting circuit, the interval T _A 3 is a section in which the transient voltage rises due to line stored energy in the capacitor T _A 5 is the residual voltage of the capacitor Indicates the section that is automatically discharged. Be the time t _A 3 and t _A 4 is a reverse current injected into the t _A 4 transient voltage (V101), since the point at which the arc extinguishing to be the current zero point generation for high-speed mechanical switch 101 is applied to the gap of the high-speed mechanical switch do.

In the case of FIG. 5A, voltage values in a section indicating charge and discharge of the capacitor 201 are shown. Figure 5b shows that the polarity is inverted in the charged capacitor to the voltage V _A 201 is generated, and t 2 _A time of the capacitor 201 by a voltage V 102 _A applied to the inductance 102. The Thereafter, a high voltage is applied to the high speed switch 101. In the case of FIG. 5C, the section T _A 2 and section T _A 3 of FIG. 5B are enlarged. FIG. 5D is an enlarged view of FIG. 5B, which illustrates a current flowing through the thyristor 301 and a voltage generation time flowing through the high speed switch 101 according to sections t _A 3 and t _A 4.

Figure 5b shows that the polarity is inverted in the charged capacitor to the voltage V _A 201 is generated, and t 2 _A time of the capacitor 201 by a voltage V 102 _A applied to the inductance 102. The Thereafter, a high voltage is applied to the high speed switch 101. In the case of FIG. 5C, the section T _A 2 and section T _A 3 of FIG. 5B are enlarged. FIG. 5D is an enlarged view of FIG. 5B, which illustrates a current flowing through the thyristor 301 and a voltage generation time flowing through the high speed switch 101 according to sections t _A 3 and t _A 4.

Figure 6 shows the main voltage and current signal at the time of blocking the load current. The voltage value in the section showing charge and discharge of the capacitor 201 is shown. Figure 6a shows that the polarity is inverted in the charged capacitor to the voltage V _B 201 is generated, and the time t _B 2 of the capacitor 201 by a voltage V _B 102 across the inductance (102). Thereafter, a high voltage is applied to the high speed switch 101. In the case of FIG. 6C, the 20ms to 21ms section of FIG. 6A is enlarged. FIG. 6D is an enlarged view of FIG. 6A and shows a current flowing through the thyristor 301 and a voltage generation point flowing through the high speed switch 101.

As an embodiment of the present invention, a DC current blocking device and a method are described, but the scope of the technical idea of the present invention is not limited by the embodiments disclosed in the present invention, and each of the components constituting the DC current blocking device. The form of the connection of these devices, or the way of constructing a circuit that performs the same function as each element or performs the same function should be interpreted as having a protection range for the same range and the equivalent range.

[Description of the code]

10: main breaker

101: high speed mechanical switch

102: Inductance for current limit

103: high speed mechanical switch

104: Inductance for current limit

20: auxiliary breaker

201: capacitor

202: impedance for reverse current adjustment

204: inductance for polarity

205: thyristor for polarity reverse

207: surge arrester

209: discharge impedance

30: reverse current conducting line portion

301: thyristor for reverse current

40: main charging line part

401: main charging line diode

402: main charging line resistance

50: auxiliary charging line

501: secondary charging resistance

502: auxiliary charging switch

60: reverse current conducting line portion

601: thyristor for reverse current

70: main charging line part

701: main charging line diode

702: main charging line resistance

Claims

In the DC current breaker,

A main interrupter 10 configured by connecting a pair of high speed mechanical switches 101 and 103 to a current limiting inductance 102 configured to generate an induced voltage when an accident current occurs;

Auxiliary breaker 20 is installed to be connected in parallel with the high speed mechanical switches (101, 103) on a circuit connected in parallel with the main breaker, and configured to generate a reverse current to the high speed mechanical switches (101, 103) ),

It is connected in series with the auxiliary blocking unit 20, and has a reverse current conducting line unit 30 configured to conduct a reverse current generated in the auxiliary blocking unit 20,

The high speed mechanical switches 101 and 103 are configured to charge the voltage charging capacitor 201 of the auxiliary breaker 20 when the fault current is blocked, and is connected to the main breaker 10 in parallel. DC current cut-off device comprising a main charging line portion (40) connected in series with the auxiliary breaker 20 is installed in parallel with the series connection of the current limiting inductance (102).
The method of claim 1,

A connection point of the reverse current conducting line unit 30 and the main charging line unit 40 of the auxiliary interrupter 20 is connected to the ground side, and to charge the voltage charging capacitor 201 when the normal current conduction is interrupted. DC current blocking device further comprises a configured auxiliary charging line unit (50).
The method of claim 1,

The auxiliary blocking unit 20 is characterized in that the charge voltage polarity inverting circuit in which the inductance 204 and the thyristor 205 is connected in series to the voltage charging capacitor 201 for generating a reverse current is connected in parallel DC current breaker.
The method of claim 1,

The auxiliary blocking unit 20 is connected to the surge arrester 207 in parallel with a series connection portion in which the voltage charging capacitor 201 and the reverse current adjusting resistor 202 for generating a reverse current in series is connected in parallel. DC current breaker.
The method of claim 1,

The auxiliary current blocking unit 20 is a DC current breaker, characterized in that the discharge resistor 209 for discharging the residual voltage of the voltage charging capacitor 201 in parallel with the capacitor 201 after the blocking operation.
The method of claim 1,

The main charging line 40 has a diode 401 and a charging resistor 402 in series, through which the auxiliary breaker 20 is connected to the series connection of the inductance 102 and the high speed mechanical switches 101 and 103. DC current breaker, characterized in that connected in parallel.
The method of claim 1,

The reverse current conducting line unit 30 is composed of a thyristor 301 through which the secondary current blocking device 20, characterized in that the auxiliary switch unit 20 is connected in parallel to the mechanical switch (101, 103).
The method of claim 2,

The auxiliary charging line unit 50 is a mechanical switch 502 and the charging resistor 501 is connected in series, DC current breaker, characterized in that located between the auxiliary breaker 20 and the ground side.
The method of claim 1,

DC current circuit breaker, characterized in that for connecting the DC circuit breaker structure in a symmetrical form with respect to the auxiliary circuit breaker 20 for bidirectional current blocking.
a) determining whether one of the following blocking conditions is satisfied according to the DC current;

The blocking condition of step a) is

a1) includes the condition of performing DC current blocking in a normal current state,

a2) including current rise condition by accident current,

b) when the blocking condition of the al) or a2) is satisfied, the voltage charging capacitor 201 positioned in the auxiliary blocking unit 20 through the main charging line unit 40 or the auxiliary charging circuit 50, respectively. Charging;

c) when the voltage charging capacitor 201 is charged by the step b), a reverse voltage is applied to a charging voltage polarity inversion circuit connected to the auxiliary blocking unit 20 in parallel with the voltage charging capacitor 201. Energizing a thyristor 301 located in the line part 30 to generate a current zero in the high speed mechanical switch; And

d) extinguishing the arc of the high speed mechanical switch in the opening when a current zero is generated in the high speed mechanical switch; DC current blocking method comprising a.
The method of claim 10

In the step of generating a current zero in the high speed switch of step c),

The charging voltage of the capacitor 201 is inverted by the turn-on operation of the thyristor 205, and the turn-on of the thyristor 301 of the reverse current conducting line part 30 is turned on. DC current blocking method comprising the step of applying a reverse current to the high-speed mechanical switch 101 through the (on) operation.
The method of claim 10,

In step b),

The capacitor 201 of the auxiliary breaker 20 is charged by the induced voltage generated in the current limiting inductance 102 when the current rise condition occurs due to the fault current, and the auxiliary charging line when the DC current blocking condition occurs in the normal current state. DC current blocking method characterized in that the capacitor 201 of the auxiliary breaker 20 is charged through (50).
The method according to claim 12,

In the case of charging the capacitor 201 of the auxiliary blocking unit 20 through the auxiliary charging line 50,

DC current cut-off method, characterized in that the method for reducing the switch 502 to the open state after charging the line voltage after the switch 502 and the load current is cut off.