CN211456682U - Passive flexible direct current power grid fault current limiter - Google Patents

Abstract

The utility model discloses a passive flexible DC power grid fault current limiter, which comprises a primary side circuit and a secondary side circuit, wherein the primary side circuit comprises a primary winding; the secondary side circuit comprises a secondary winding and one or more control circuits connected in series with the secondary winding; the primary winding and the secondary winding are coupled through a magnetic field. The current limiter has low impedance in a normal state, small loss and quick current limiting in a power grid fault state.

Description

Passive flexible direct current power grid fault current limiter

Technical Field

The utility model belongs to the electric power field, in particular to novel flexible direct current electric wire netting fault current limiter of passive form based on controllable magnetic coupling of power electronics.

Background

With the demand for conversion from traditional energy structures to clean, efficient energy structures, renewable energy is rapidly developing. Meanwhile, the energy system has new functions and performance requirements on an important medium, namely a power grid, for energy collection, grid connection, transmission and distribution, wherein the flexible direct current (flexible direct current) power grid has one of important development directions of the power grid in the future, further fault current limiting is related to reliable and safe operation of the flexible direct current power grid, the development of the direct current limiter is relatively lagged, and the existing direct current limiter cannot meet the requirements of rapid parameter change, rapid current limiting, low loss and high reliability at the same time. How to provide a current-limiting fast current limiter with low impedance in normal state, low loss and power grid fault state becomes a technical problem to be solved urgently.

SUMMERY OF THE UTILITY MODEL

To the problem, the utility model provides a flexible direct current electric wire netting fault current limiter of passive form, this current limiter normal state impedance is low, the loss is little, electric wire netting fault state current limiting is rapid.

The utility model aims to provide a passive flexible DC power grid fault current limiter, which comprises a primary side circuit and a secondary side circuit, wherein,

the primary side circuit includes a primary winding;

the secondary side circuit comprises a secondary winding and one or more control circuits connected in series with the secondary winding;

the primary winding and the secondary winding are coupled through a magnetic field.

Further, the one or more control circuits are connected in parallel.

Further, the one or more control circuits each include at least a switching branch, a buffering branch, and an energy absorption branch; wherein,

the switch branch, the buffer branch and the energy absorption branch are connected in parallel.

Further, the air conditioner is provided with a fan,

the switch branch comprises two reversely connected solid-state switches, each solid-state switch comprises a semiconductor device and a diode, and the semiconductor devices are connected with the diodes in an anti-parallel mode;

the energy absorption branch comprises a lightning arrester.

Further, the semiconductor device comprises an IGCT and an IGBT.

Further, the control circuit further comprises a load module, the load module is respectively connected in series with the switch branch, the buffer branch and the energy absorption branch, wherein,

the load module is one of an RL circuit, a pure inductor circuit, a pure resistor circuit, an LC circuit, an RCL circuit and an RC circuit.

Further, the buffering branch circuit is an RC buffering circuit.

The utility model discloses a novel flexible direct current electric wire netting fault current limiter of passive form has following beneficial effect:

1. the primary side circuit only comprises a primary winding, other additional electric elements are not arranged, the loss of the working state of a large number of current limiters cannot be increased additionally, the complexity of the current limiters is reduced, the reliability of the current limiters is improved, and the technical economy and the feasibility of equipment are improved.

2. The circuit is provided with one or more control circuits, loads are arranged in the control circuits, different loads are switched through semiconductor devices in the control circuits, different equivalent impedances can be generated, and therefore the functions of limiting fault current and protecting the circuit are achieved.

3. The primary side winding and the secondary side winding are coupled through a magnetic field, rapid change of secondary side impedance is achieved based on switching of a control circuit semiconductor device, and rapid change of the secondary side impedance can be coupled to the primary side, so that rapid change of the primary side impedance is achieved, and the purpose of rapidly limiting fault current is achieved.

Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by the practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed to be used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.

Fig. 1 shows a schematic structural diagram of a passive flexible dc power grid fault current limiter according to an embodiment of the present invention;

fig. 2 shows a schematic diagram of a control circuit structure in an embodiment of the present invention;

fig. 3 shows another schematic structural diagram of a control circuit in an embodiment of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the embodiments of the present invention are clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by a person skilled in the art without creative work belong to the protection scope of the present invention.

As shown in fig. 1, the utility modelThe novel passive flexible direct current power grid fault current limiter comprises a primary side circuit and a secondary side circuit, wherein the primary side circuit comprises a primary winding, the secondary side circuit comprises a secondary winding and one or more control circuits connected in series with the secondary winding, and the one or more control circuits are connected in parallel; the primary winding and the secondary winding are coupled through a magnetic field. The primary side circuit is made of pure metal materials, namely, a semiconductor device or a superconducting material is not added into the primary side circuit, and the original circuit structure is not damaged. Further, a primary winding in the primary side circuit includes a resistor R₁And an inductance L₁The secondary winding in the secondary side circuit comprises a resistor R₂And an inductance L₂M is mutual inductance between the primary winding and the secondary winding, and the turn ratio of the primary winding to the secondary winding is n:1, wherein n is an integer. The primary side circuit is made of pure metal materials, extra electric elements such as semiconductor components are not introduced, the loss of the working state of a large number of current limiters is not increased, the complexity of the current limiters is reduced, the reliability of the current limiters is improved, and the technical economy and the feasibility of equipment are improved. The secondary side circuit is provided with a control circuit, when the fault current is limited, the control circuit arranged in the secondary side circuit realizes the rapid change of the secondary side impedance, and the magnetic field is coupled to the primary side for current limiting.

Specifically, the one or more control circuits each include a switching branch, a buffering branch, and an energy absorption branch; as shown in fig. 1, the one or more control circuits are circuit 1 and circuit 2 … …, where m is an integer, and then in the process of current limiting of the current limiter, impedance can be dynamically changed by controlling switching of switches in different control circuits, for example, when the current limiter performs current limiting, only the switch branch of one of the control circuits is controlled to be disconnected and the switch branches of the two control circuits are controlled to be disconnected, so that impedances in the secondary side circuit are different. Similarly, different impedances can be changed by controlling the switching of different switch branches in a steady state so as to change the damping coefficient on the line.

The switch branch comprises two solid-state switches which are connected in reverse, each solid-state switch comprises a semiconductor device and a diode, the semiconductor devices are connected with the diodes in an anti-parallel mode, and each semiconductor device comprises an IGCT (integrated gate commutated thyristor) and an IGBT (insulated gate bipolar transistor). As shown in fig. 2, when the semiconductor devices in the two solid-state switches are IGCTs, the cathode of one of the IGCTs is connected to the cathode of the other IGCT. As shown in fig. 3, when the semiconductor devices in the two solid-state switches are IGBTs, the collector of one IGBT is connected to the collector of the other IGBT. The switch branch is a bidirectional switch branch, and further, the freewheeling diode can be used for protecting the semiconductor devices connected in parallel regardless of an IGCT or an IGBT and the freewheeling diode, and in addition, one semiconductor device and one diode are connected in series and conducted at the moment when the switch branch is switched on.

The energy absorption branch circuit comprises an MOV lightning arrester, and is used for showing clamping pressure characteristics on the secondary side when the solid-state switch is switched off under the conditions of reasonable parameter design and matching, namely the secondary side voltage is the clamping voltage of the MOV, the condition of overvoltage cannot occur, the secondary side current is reduced, negative voltage which is larger than power supply voltage is generated on the primary side through magnetic field coupling, the primary side fault current is limited to be rapidly increased, the process is finished until the current in a secondary side circuit becomes 0, and therefore the effect of limiting the fault current is achieved. More specifically, the reasonable parameter design includes setting of a resistance and an inductance of the secondary side winding.

As shown in fig. 2 and 3, the control circuit further includes a load module, the load module is connected in series in the secondary winding and is connected in series with the switch branch, the buffer branch and the energy absorption branch, the load module is one of an RL circuit, a pure inductor circuit, a pure resistor circuit, an LC circuit, an RCL circuit and an RC circuit, however, the present invention is not limited thereto, as long as the present invention can be implemented with the principle that the load branch changes impedance, for example, the RCL may be connected in series, may also be connected in parallel, etc. It is to be noted that; the control circuit may be provided with a load module or not, and the control circuit shown in fig. 2 and 3 is a circuit structure diagram when the load module is provided, so that the reasonable parameter design may be to set an electrical parameter, such as the size of an inductor or a resistor, of the load module in one or more control circuits, so as to realize a low impedance state under the normal condition of the current limiter.

The buffering branch circuit is an RC buffering circuit. As shown in fig. 2 and 3, the snubber branch includes a capacitor Cs and an inductor Rs, wherein the snubber branch can play a role of current snubber when the solid-state switch in the control circuit is operated, so as to protect the freewheeling diode in the solid-state switch from being broken down due to overvoltage. When the voltage of the buffer branch circuit reaches the trigger voltage of the MOV lightning arrester, the MOV lightning arrester is triggered to work, and the current in the secondary side circuit is absorbed by the MOV lightning arrester until the current is 0.

The embodiment of the utility model provides an embodiment has still introduced the control method of above-mentioned flexible direct current electric wire netting fault current limiter of passive form, the port of the primary side circuit of current limiter with direct current transmission line is connected, and is established ties with the circuit breaker, when direct current transmission line takes place the short-circuit fault, with circuit breaker action time cooperation, utilize the current limiter to play the effect of limiting the fault current, thereby the control method includes at first, control one or more the switch branch road disconnection of control circuit; the current in the switch branch circuit is transferred to the buffer circuit and the energy absorption branch circuit, and the current in the secondary side circuit is changed; the lightning arrester in the energy absorption branch circuit has a clamping pressure characteristic on the secondary side, the secondary side current is reduced and is coupled on the primary side through a magnetic field to generate negative pressure larger than power supply voltage, and energy stored by an inductor in a secondary winding is continuously consumed, so that the current in a secondary side circuit is reduced, and the impedance in the secondary side circuit is changed; then, the primary-side fault current rising rate is decreased by the magnetic field coupling, thereby changing the impedance in the primary-side circuit. The semiconductor device can instantly complete on and off, and realize rapid change of impedance in a secondary side circuit, so that rapid impedance change is realized on a primary side (power grid transmission line side) through magnetic coupling, and the purpose of limiting fault current is achieved.

The energy absorption branch circuit continuously consumes energy in the secondary side circuit, when current in the secondary side circuit is reduced to 0, the secondary winding is open, and impedance in the primary side circuit is impedance of the primary winding. That is, the energy of the inductor in the secondary side circuit is released completely and is completely opened, and the secondary side winding does not influence the electrical characteristics of the primary side winding through magnetic field coupling. And because the primary side circuit is made of pure metal materials, the impedance of the primary side circuit is completely the impedance generated by the primary winding, and the current rises under the action of the port voltage of the primary side circuit.

Specifically, as an exemplary illustration, only one control circuit is connected in series in the secondary side circuit, and a load module is disposed in the control circuit, when the MOV arrester absorbs energy, the MOV arrester and the secondary winding form a loop, the MOV arrester exhibits a clamping voltage characteristic on the secondary side, a current in the secondary side circuit decreases, a negative voltage greater than a power supply voltage is generated on the primary side through magnetic field coupling, and a rising rate of the current in the primary side circuit is limited, so that the primary side circuit and the secondary side circuit satisfy:

i₁(0)＝I_{short2_1}

i₂(0)＝I_{short2_2}

wherein, U_clampingClamping voltage for lightning arrester, I_{short2_1}、I_{short2_2}Current i in the primary side circuit when the power electronic switch is closed₁(0) And the current i in the secondary side circuit₂(0) Taking the value of (A); r₁Is the primary winding resistance, R₂Is the resistance of the secondary winding, L₁Is a primary winding inductance, L₂Is the inductance of the secondary winding, M is the mutual inductance between the primary and secondary windings, i₁(t) and i₂(t) are the currents in the primary side circuit and the secondary side circuit, respectively.

Before the semiconductor device is closed, namely before a short-circuit fault occurs or during normal operation, a load module and a secondary winding in the secondary winding form a loop, and a secondary side keeps low load (if the load module is not arranged in a control circuit, the secondary side is short-circuited), so that the primary side of the current limiter has low impedance. The primary side circuit and the secondary side circuit satisfy:

i₁(0)＝I_{short1_1}

i₂(0)＝0

wherein R is₁Is the primary winding resistance, R₂Is the resistance of the secondary winding, L₁Is a primary winding inductance, L₂Is the inductance of the secondary winding, M is the mutual inductance between the primary and secondary windings, i₁(t) and i₂(t) is the current in the primary side circuit and the secondary side circuit, R_loadIs a load resistance, L_loadIs a load inductance; i is_{short1_1}Current i in the primary side circuit when short circuit occurs₁(0) And at this time, the current i in the secondary side circuit₂(0) Is 0.

When the current in the secondary side circuit is reduced to 0 and the secondary winding is open-circuited, the secondary winding does not influence the electrical characteristics of the primary winding through magnetic field coupling any more, and the primary side circuit and the secondary side circuit meet the following requirements:

i₁(0)＝I_{short3_1}

i₂(0)＝I_{short3_2}

wherein, the I_{short3_1}、I_{short3_2}After the power electronic switch is closed, the current i in the primary side circuit₁(0) And the current i in the secondary side circuit₂(0) The value of (a).

Therefore, by analyzing the working characteristics of the circuits at different control stages, the switching of the semiconductor devices in the control circuit is different, the current change is different, and different equivalent impedances can be generated, so that the effects of limiting fault current and protecting the circuit are achieved.

Although the present invention has been described in detail with reference to the foregoing embodiments, it should be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; such modifications and substitutions do not depart from the spirit and scope of the present invention in its corresponding aspects.

Claims (7)

1. A passive flexible DC power grid fault current limiter is characterized in that the fault current limiter comprises a primary side circuit and a secondary side circuit, wherein,

the primary side circuit includes a primary winding;

the secondary side circuit comprises a secondary winding and one or more control circuits connected in series with the secondary winding;

the primary winding and the secondary winding are coupled through a magnetic field.

2. The passive, flexible dc grid fault current limiter of claim 1, wherein the one or more control circuits are connected in parallel.

3. The passive, flexible dc grid fault current limiter of claim 2, wherein the one or more control circuits each comprise at least a switching branch, a snubber branch, and an energy absorption branch; wherein,

the switch branch, the buffer branch and the energy absorption branch are connected in parallel.

4. A passive, flexible DC grid fault current limiter according to claim 3,

the switch branch comprises two reversely connected solid-state switches, each solid-state switch comprises a semiconductor device and a diode, and the semiconductor devices are connected with the diodes in an anti-parallel mode;

the energy absorption branch comprises a lightning arrester.

5. The passive flexible dc grid fault current limiter of claim 4, wherein the semiconductor device comprises an IGCT, an IGBT.

6. The passive, flexible dc grid fault current limiter according to claim 4 or 5, wherein the control circuit further comprises a load module, which is connected in series with the switching branch, the snubber branch and the energy absorption branch, respectively, wherein,

the load module is one of an RL circuit, a pure inductor circuit, a pure resistor circuit, an LC circuit, an RCL circuit and an RC circuit.

7. The passive flexible dc grid fault current limiter of claim 3, wherein the snubber branch is an RC snubber circuit.

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