KR101802509B1

KR101802509B1 - Cascaded Half Bridge Solid State Circuit Breaker

Info

Publication number: KR101802509B1
Application number: KR1020150177905A
Authority: KR
Inventors: 서용석; 셔모하마디 시아막
Original assignee: 전북대학교산학협력단
Priority date: 2015-12-14
Filing date: 2015-12-14
Publication date: 2017-11-28
Also published as: KR20170070427A

Abstract

CHB SSCB (Cascaded Half Bridge Solid State Circuit Breaker) is provided. The SSCB according to an embodiment of the present invention includes a first circuit breaker and a second circuit breaker that provide a path for current flow when an accident occurs using first and second half bridge converters that provide a path for current flow in normal operation using semiconductor switches . Thereby, loss can be reduced at a low cost and a quick shutdown operation can be performed.

Description

The Cascaded Half Bridge Solid State Circuit Breaker (SSCB)

The present invention relates to an electric switch, and more particularly, to a DC circuit breaker and an opening / closing device.

Conventional DC DC circuit breakers are widely used in train DC power systems, high voltage DC transmissions, and other industrial and commercial DC systems.

Generally, it is based on a mechanical switch with a movable contact. However, the current interruption using the circuit breaker of this type has a problem such as a relatively slow electrical interruption due to the structural limitation of eliminating the electric arc discharge which occurs during the interruption operation.

SSCB (Solid State Circuit Breaker), which is capable of fast current shutdown under high current and high voltage circuit operating conditions, has a relatively fast shutdown characteristic compared to conventional mechanical switch type DC circuit breaker, Providing a new horizon for voltage blocking.

In addition, the SSCB has much more flexibility in tripping functions than mechanical circuit breakers. This means that the SSCB can be programmed to perform various shutdown operations with minimal cost. However, the SSCB requires a large number of power semiconductor switches due to the structural limitations of shutting off high current and high voltage by connecting power semiconductor switches in series and parallel form. Therefore, the product price is relatively higher than that of mechanical switch based breakers, The electrical conduction loss increases.

Hybrid SSCB, which is a more advanced version than the electric SSCB, is a circuit breaker which is a mixture of conventional mechanical switch and electric SSCB. It adopts mechanical switch with smaller capacity than mechanical breaker and power semiconductor switch with smaller capacity than SSCB. It is possible to cut off the circuit relatively quickly without increasing the electrical conduction loss. However, the hybrid SSCB requires a sophisticated time-synchronized control in the switching operation of the mechanical switch and the power semiconductor switch due to the structure in which the mechanical switch and the power semiconductor switch are operated in a mixed manner. In addition, the electrical SSCB and the hybrid SSCB are equipped with a surge arrestor in common to suppress the transient voltage caused by the sudden interruption of the current due to the fault in the DC power line path unlike the mechanical switch type circuit breaker have. However, surge arresters have the problem of requiring periodic parts replacement due to additional cost increases and lifetime limitations.

SUMMARY OF THE INVENTION It is an object of the present invention to reduce the electrical conduction loss of a circuit breaker at a low cost in a hybrid SSCB, increase the reliability of time operation control and reduce surge arresters, And a SSCB including a cascaded half bridge converter.

According to an aspect of the present invention, there is provided a solid state circuit breaker (SSCB) comprising: a first breaker for providing a current path for a current during normal operation using semiconductor switches; And a second circuit breaker using half bridge converters to provide a path for current flow in the event of a line fault.

The SSCB according to an embodiment of the present invention further includes a mechanical switch connected between the DC voltage source and the first breaker,

The first circuit breaker further includes: an eleventh switch for switching a current from a source to a load; And a twelfth switch for switching the current from the load to the source

The eleventh switch and the twelfth switch may be turned on during the normal operation.

The second circuit breaker may include a first half bridge converter connected in parallel to the first capacitor and connected in the opposite direction to the twenty first switch and the twenty second switch; And a second half bridge converter connected in parallel to the second capacitor and connected in the opposite direction to the twenty-third switch and the twenty-fourth switch.

The twelfth switch, the twenty-third switch, the twenty-third switch, and the twenty-fourth switch are all turned on after an accident occurs in the load, and then the eleventh switch and the twelfth switch are turned off, A current path can be generated through the twenty-first switch and the twenty-third switch.

Further, after the eleventh switch and the twelfth switch are turned off, the mechanical switch may be turned off.

Then, after the mechanical switch is turned off, the twenty-first switch and the twenty-third switch are turned off so that current flows through the twenty-second switch, the first capacitor, the twenty-fourth switch, A flowing path can be generated.

Meanwhile, according to another embodiment of the present invention, a switching control method includes: a first circuit breaker, using semiconductor switches, to provide a current path of a current during normal operation; And a second circuit breaker, using half bridge converters, to provide a path of current flow in the event of an accident.

As described above, according to embodiments of the present invention, in a normal operation mode, a current switch does not flow through the main breaker, a mechanical switch having little loss is used, and a low conduction resistance and a low conduction voltage drop So that the steady state loss can be reduced.

Further, according to embodiments of the present invention, there is no need for a cooling system because there is no loss of steady state.

In addition, according to the embodiments of the present invention, it is possible to prevent arcing at the time of opening the mechanical switch by using the switches of the auxiliary circuit breaker in shutting off the current to the main circuit breaker. This can create the advantage of using relatively low-cost, low-cost mechanical switches.

Further, according to embodiments of the present invention, since the main breaker includes a half bridge converter to which a capacitor is connected, the reliability of the breaking operation and the capacity of the surge arresters for prolonging the breaker life are reduced, Arrestors may not even be needed at all.

Further, according to embodiments of the present invention, the series connection module structure of the half bridge converter enables a flexible design of various voltage and current capacity DC blocking systems.

1 is a circuit diagram of a CHB SSCB according to an embodiment of the present invention,
2 is a diagram provided in the description of the operation of the CHB-SSCB in the normal operation mode,
3 is a diagram provided in the explanation of the operation of the CHB-SSCB in the accident management mode,
4 is a diagram provided in the description of the operation of the CHB-SSCB in the accident correction mode.

Hereinafter, the present invention will be described in detail with reference to the drawings.

Due to the relatively small inductance of the DC network, the fault / fault propagation rate is faster in the DC system than in the AC system. In addition, the DC system has a non-zero crossing voltage and current characteristics which are not periodically zeroed, unlike the AC system, in the event of a short circuit in the system. Therefore, the DC circuit breaker has a problem in that it is relatively difficult to short-circuit between the zero voltage and the zero current as compared with the AC circuit breaker. Electrical SSCBs that can block circuits using power semiconductors are a useful alternative to mechanical circuit breakers in DC systems. The SSCB is fundamentally less arcing than a mechanical circuit breaker and is lighter. In particular, the operating time required for interrupting is significantly reduced, allowing fast and safe circuit interception after an accident, thus safeguarding the electrical equipment of the DC circuit from accidents It has the advantage of being able to do.

In the embodiment of the present invention, the SSCB for interrupting the DC current of medium / low voltage (Medium / Low Voltage) is proposed. It can be used as a hybrid SSCB for a DC railway power system such as a subway system, as well as for other systems, high-voltage transmission lines, and other industrial and commercial DC systems.

1 is a circuit diagram of a CHB SSCB (Cascaded Half Bridge Solid State Circuit Breaker) according to an embodiment of the present invention. The CHB SSCB according to an embodiment of the present invention is connected between the source 1 and the load 6.

In other words, the CHB SSCB according to an embodiment of the present invention may be said to be connected in series with a current path, for example, a power transmission line (such as an HVDC power transmission line) or a distribution line.

1, a CHB SSCB according to an embodiment of the present invention includes an FDS 2, an auxiliary breaker 4, and a main breaker 5.

The FDS (Fast Disconnector Switch) 2 is a mechanical switch that operates at high speed. The high-speed operation of the FDS is enabled by the no-load (zero current) shutdown function. The FDS 2 is connected between the DC voltage source 1 and the auxiliary circuit breaker 4.

The auxiliary circuit breaker 4 comprises two switches 10, 11 connected in parallel. The switches 10 and 11 are implemented by a semiconductor switch.

Switch-1 10 switches the path connection from the source 1 to the load 6 and switch-2 11 switches the path connection from the load 6 to the source 1. [

The main breaker 5 can be constituted by a plurality of half bridge converters according to the total current voltage capacity of the circuit breaker. In an embodiment of the present invention, two half bridge converters are used for convenience of illustration. The half bridge converters are composed of the switches 12 and 13 and the capacitor 14. The switches 12 and 13 are implemented by a semiconductor switch.

The switches 12 and 13 are connected in parallel to the capacitor 14 and are connected in opposite directions.

Meanwhile, the CHB SSCB according to the embodiment of the present invention further includes a controller (not shown) for controlling the switching operation of the switches 10, 11, 12 and 13, The switching operation of the switches 10, 11, 12, 13 is controlled according to the mode.

FIG. 2 is a diagram provided in a description of the operation of the CHB-SSCB in a normal operating mode. FIG.

In the normal operating mode, as shown in FIG. 2, the FDS is closed and switches- ₁ , ₂ (S _A1 , S _A2 ) of the auxiliary breaker are turned on. On the other hand, the switches (S _M1 , S _M2 , S _M3 , and S _M4 ) of the main breaker are all turned off.

Accordingly, the current flows only through the switches (S _A1 , S _A2 ) of the FDS and the auxiliary circuit breaker, and this path through which the current flows is called an auxiliary path.

The conduction loss of the auxiliary path is lower than the conduction loss of the main path, the path through which the current flows through the main circuit breaker. The auxiliary path also has a bi-directional current flow from the DC voltage source source (DC) to the load (R _Load ) and from the load (R _Load ) to the source (DC).

3 is a diagram provided in the explanation of the operation of the CHB-SSCB in the Fault Management Mode.

When an accident such as a short circuit or a failure occurs in a transmission line or a distribution line between the CHB-SSCB and the load (R _Load ), the switches (S _M1 , S _M2 , S _M3 , and S _M4 ) All are turned on.

The switches S _M1 , S _M2 , S _M3 , and S _M4 of the main breaker are turned on before the switches S _A1 and S _A2 of the auxiliary breaker are turned off. And, until the switches (S _A1 , S _A2 ) of the auxiliary circuit breaker are turned off, the current still flows through the auxiliary path.

3, when the switches S _A1 and S _A2 of the auxiliary circuit breaker are all turned off, the current flows through the switch-1 (S _M1 ) and the switch-3 (S _M3 ) of the main breaker Flows through.

In this way, since current is drawn from the auxiliary path, this is called accident management. This provides a condition that allows the FDS to open at zero current without arcing. Then, in order to completely protect the switches S _A1 , S _A2 of the auxiliary breaker from the voltage spike, the FDS is opened.

4 is a diagram provided in the explanation of the operation of CHB-SSCB in Fault Clearance Mode.

The switch of the main circuit breaker (S _M1, S _M2, S _M3, _M4 S) are all turned in the on state, the switch immediately after the FDS of the auxiliary circuit-breaker open, the main breaker -1,3 (S _M1, S _M3 ). &Lt; / RTI >

Thus, the capacitors _-1 and ₂ (C ₁ and C ₂ ) are charged by the current flowing through the switches -2 and 4 (S _M2 and S _M4 ) of the main breaker.

When capacitors- ₁ , ₂ (C ₁ , C ₂ ) are charged, the main breaker reaches a zero-crossing condition necessary for complete shutdown.

Up to now, a preferred embodiment of the CHB SSCB has been described in detail.

The structure of the main breaker shown in Figs. 1 to 4 is merely an example. Although FIG. 1 assumes a main breaker having a structure in which two half bridge converters are connected in series, another structure can be changed. For example, it is possible to increase the number of half-bridge converters connected in series, and it is also possible to configure a main breaker by connecting a plurality of parallel-connected half bridge converters in series.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, It will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the present invention.

FDS
S _A1 , S _A2 : auxiliary breaker switch
S _M1 , S _M2 , S _M3 , S _M4 : Main breaker switch
C ₁ , C ₂ : Capacitor

Claims

A first circuit breaker using semiconductor switches to provide a current path of current during normal operation;
A second circuit breaker using half bridge converters to provide a path of current flow in the event of a fault; And
And a mechanical switch connected between the source and the first breaker for switching,
The first circuit breaker includes:
An eleventh switch for switching the current from the source to the load; And
And a twelfth switch for switching the current from the load to the source,
The second circuit breaker includes:
A first half bridge converter having a twenty-first switch and a twenty-second switch connected in parallel to the first capacitor and connected in opposite directions to each other;
And a second half bridge converter connected in parallel to the second capacitor and connected in opposite directions to each other,
The twelfth switch, the twenty-third switch, the twenty-third switch, and the twenty-fourth switch are all turned on after an accident occurs in the load, the eleventh switch and the twelfth switch are turned off, And a path through which a current flows is generated through the switch and the 23rd switch.

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The method according to claim 1,
And the eleventh switch and the twelfth switch,
And is turned on in the normal operation.

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The method according to claim 1,
And after the eleventh switch and the twelfth switch are turned off, the mechanical switch is turned off.

The method of claim 7,
After the mechanical switch is turned off, the twenty-first switch and the twenty-third switch are turned off, and a path through which the current flows through the twenty-second switch, the first capacitor, the twenty- Is generated.

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