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

A passive flexible DC grid fault current limiter

technical field

The utility model belongs to the field of electric power, in particular to a novel passive flexible direct current grid fault current limiter based on power electronic controllable magnetic coupling.

Background technique

With the transition from traditional energy structure to clean and efficient energy structure, the rapid development of renewable energy. At the same time, the energy system has new functions and performance requirements for the power grid, an important medium for energy collection, grid connection, transmission and distribution. Among them, the flexible DC (flexible DC) power grid is important for the future power grid due to its advantages. One of the development directions, further fault current limiting is related to the reliable and safe operation of the flexible DC power grid, while the development of DC current limiters is relatively lagging behind. reliability requirements. How to provide a current limiter with low impedance in normal state, small loss, and rapid current limiting in power grid fault state has increasingly become a technical problem to be solved urgently.

Utility model content

In view of the above problems, the present invention provides a passive flexible DC power grid fault current limiter, which has low impedance in normal state, small loss, and rapid current limiting in power grid fault state.

The purpose of the utility model is to provide a passive flexible DC power grid fault current limiter, which includes a primary side circuit and a secondary side circuit, wherein,

the primary side circuit includes a primary winding;

The secondary side circuit includes a secondary winding and one or more control circuits connected in series with it;

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, each of the one or more control circuits includes at least a switch branch, a buffer branch and an energy absorption branch; wherein,

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

further,

The switch branch includes two reversely connected solid-state switches, the solid-state switches include a semiconductor device and a diode, and the semiconductor device and the diode are in antiparallel;

The energy absorption branch includes a lightning arrester.

Further, the semiconductor device includes IGCT and IGBT.

Further, the control circuit further includes a load module, and 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 RL circuit, pure inductance circuit, pure resistance circuit, LC circuit, RCL circuit and RC circuit.

Further, the buffer branch is an RC buffer circuit.

The novel passive flexible DC power grid fault current limiter of the utility model has the following beneficial effects:

1. The primary side circuit only includes a primary winding, no other additional electrical components are set, and a large amount of losses in the working state of the current limiter will not be added, and it is beneficial to reduce the complexity of the current limiter and improve the current limiter. reliability and improve the technical economy and feasibility of the equipment.

2. One or more control circuits are provided. Loads are set in the control circuits. Different equivalent impedances can be generated by switching the semiconductor devices in the control circuit to different loads, so as to limit the fault current and protect the circuit. effect.

3. The primary side winding and the secondary side winding are coupled through the magnetic field, and based on the switching of the semiconductor device of the control circuit, the rapid change of the secondary side impedance can be realized, and the rapid change of the secondary side impedance can be coupled to the primary side, so as to realize The rapid change of the primary side impedance achieves the purpose of quickly limiting the fault current.

Other features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention may be realized and attained by the structure pointed out in the description, claims and drawings.

Description of drawings

In order to more clearly illustrate the embodiments of the present utility model or the technical solutions in the prior art, the following briefly introduces the accompanying drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description These are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can also be obtained from these drawings without creative efforts.

1 shows a schematic structural diagram of a passive flexible DC grid fault current limiter in an embodiment of the present invention;

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

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

Detailed ways

In order to make the purposes, technical solutions and advantages of the embodiments of the present utility model clearer, the technical solutions in the embodiments of the present utility model will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present utility model. The embodiments described above are a part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the protection scope of the present invention.

As shown in FIG. 1, an embodiment of the present utility model introduces a novel passive flexible DC power grid fault current limiter based on power electronic controllable magnetic coupling, which includes 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 it, and the one or more control circuits are connected in parallel; the primary winding and the secondary winding coupled through a magnetic field. Wherein, the primary side circuit adopts pure metal material, that is, no semiconductor device or superconducting material is introduced into the primary side circuit, and the original circuit structure is not damaged. Further, the primary winding in the primary side circuit includes a resistance R ₁ and an inductance L ₁ , the secondary winding in the secondary side circuit includes a resistance R ₂ and an inductance L ₂ , M is the mutual inductance between the primary and the secondary winding, The turns ratio of the primary winding to the secondary winding is n:1, where n is an integer. The primary side circuit adopts pure metal material, no additional electrical components such as semiconductor components are introduced, and a large amount of losses in the working state of the current limiter will not be added, and it is beneficial to reduce the complexity of the current limiter and improve the reliability of the current limiter. and improve the technical economy and feasibility of the equipment. By setting the control circuit in the secondary side circuit, when limiting the fault current, the control circuit set in the secondary side circuit realizes the rapid change of the secondary side impedance, and the magnetic field is coupled to the primary side to limit the current.

Specifically, the one or more control circuits include a switch branch, a buffer branch, and an energy absorption branch; wherein the switch branch, the buffer branch, and the energy absorption branch are connected in parallel, and the one or Multiple control circuits are connected in parallel, as shown in Figure 1, the one or more control circuits are circuit 1, circuit 2... The switching of switches in different control circuits can be controlled, and the impedance can be changed dynamically. Exemplarily, when the current limiter performs current limiting, only the switch branch of one of the control circuits is controlled to be disconnected and the two control circuits are controlled. The middle switch branch is disconnected, resulting in different impedances in the secondary side circuit. Similarly, it is also possible to change the damping coefficient on the line by controlling the switching of different switch branches in a steady state to change different impedances.

The switch branch includes two reversely connected solid-state switches, the solid-state switches include a semiconductor device and a diode, and the semiconductor device is antiparallel to the diode, and the semiconductor device includes an IGCT (Integrated Gate Commutated Thyristor). ), 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 IGCT 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. Therefore, the switching branch is a bidirectional switching branch. Further, whether it is an IGCT or an IGBT with a freewheeling diode, the freewheeling diode can be used to protect the semiconductor devices connected in parallel. The semiconductor device and a diode conduct in series.

The energy absorption branch includes an MOV arrester, which is used for when the solid-state switch is turned off, under the condition of reasonable parameter design and coordination, the MOV arrester exhibits a clamping voltage characteristic on the secondary side, that is, the secondary side voltage is MOV. Clamping voltage, there will be no overvoltage situation, the secondary side current is reduced and a negative voltage greater than the power supply voltage is generated on the primary side through magnetic field coupling, limiting the rapid increase of the primary side fault current. The current becomes 0 and ends, thus limiting the fault current. More specifically, the reasonable parameter design includes the setting of resistance and inductance values of the secondary winding, and the like.

As shown in FIGS. 2 and 3 , the control circuit further includes a load module, which is connected in series with the secondary winding and connected in series with the switch branch, the buffer branch and the energy absorption branch, respectively. The load module is one of RL circuit, pure inductance circuit, pure resistance circuit, LC circuit, RCL circuit, and RC circuit. However, the utility model is not limited to this, as long as the utility model can realize the change of impedance through the load branch. The principle is sufficient. For example, the RCL can be connected in series or in parallel. It should be noted that the control circuit may or may not be provided with a load module. The control circuits shown in Figures 2 and 3 are the circuit structure diagrams when the load module is provided, so that the reasonable parameter design can be achieved through Set the electrical parameters of the load module in one or more control circuits, such as the size of the inductance or resistance, to achieve a low impedance state under normal conditions of the current limiter.

The buffer branch is an RC buffer circuit. As shown in FIGS. 2 and 3 , the buffer branch includes a capacitor Cs and an inductance Rs, wherein the buffer branch can play a role of buffering current when the solid-state switch in the control circuit operates, thereby protecting the solid-state switch. The freewheeling diode will not break down due to overvoltage. When the voltage of the buffer branch reaches the trigger voltage of the MOV arrester, the MOV arrester is triggered to work, and the current in the secondary circuit is absorbed by the MOV arrester until it reaches zero.

The embodiment of the present utility model also introduces a control method for the above-mentioned passive flexible DC power grid fault current limiter, wherein the port of the primary side circuit of the current limiter is connected to the DC transmission line, and is connected to the open circuit When a short-circuit fault occurs in the DC transmission line, the current limiter is used to limit the fault current in coordination with the action time of the circuit breaker, so the control method includes: first, controlling one or more of the control The switch branch of the circuit is disconnected; the current in the switch branch is transferred to the buffer circuit and the energy absorption branch to change the current in the secondary side circuit; wherein, the arrester in the energy absorption branch is in the second circuit. The secondary side exhibits a clamping voltage characteristic, the secondary side current is reduced and a negative voltage greater than the power supply voltage is generated on the primary side through magnetic field coupling, and at the same time, the energy stored in the inductance in the secondary winding is continuously consumed, so that the current in the secondary side circuit is reduce, thus changing the impedance in the secondary side circuit; then, through the magnetic field coupling, the primary side fault current rising rate is decreased, thereby changing the impedance in the primary side circuit. The semiconductor device can be turned on and off instantaneously to realize the rapid change of impedance in the secondary side circuit, so as to realize the rapid impedance change on the primary side (power grid transmission line side) through magnetic coupling, so as to achieve the purpose of limiting the fault current.

The energy absorption branch continuously consumes the energy in the secondary side circuit, when the current in the secondary side circuit drops to 0, the secondary winding is open circuit, and the impedance in the primary side circuit is the primary winding impedance. That is, the inductive energy in the secondary side circuit has been released and the circuit has been completely opened, and the secondary side winding will no longer affect the electrical characteristics of the primary side winding through magnetic field coupling. And because the primary side circuit is made of pure metal material, its impedance is completely the impedance generated by the primary winding, and the current rises under the action of the primary side circuit port voltage, but due to the increase of the equivalent inductance, the current rises slowly, and the to protect the DC grid.

Specifically, only one control circuit is connected in series in the secondary side circuit, and the control circuit is provided with a load module as an example. When the MOV arrester absorbs energy, the MOV arrester forms a loop with the secondary winding, and the MOV arrester forms a loop. On the secondary side, it exhibits a clamp voltage characteristic. The current in the secondary side circuit decreases, and a negative voltage greater than the power supply voltage is generated on the primary side through magnetic field coupling. The rate of rise of the current in the primary side circuit is limited, then The primary side circuit and the secondary side circuit satisfy:

i ₁ (0)=I _{short2_1}

i ₂ (0)=I _{short2_2}

Among them, U clamping is the clamping voltage of the arrester, I _{short2_1} and I _{short2_2} are the _values of the current i ₁ (0) in the primary side circuit and the current i ₂ (0) in the secondary side circuit when the power electronic switch is closed; R1 is the primary winding resistance, R2 is the secondary winding resistance, L1 is the primary winding inductance, _L2 is the secondary winding inductance, _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, that is, before a short-circuit fault occurs or during normal operation, the load module in the secondary winding forms a loop with the secondary winding, and the secondary side maintains a low load (if no load module is provided in the control circuit, The secondary side is shorted), resulting in a low impedance on the primary side of the current limiter. The primary side circuit and the secondary side circuit satisfy:

i ₁ (0)=I _{short1_1}

i ₂ (0)=0

where R1 is the primary winding resistance, _R2 is the secondary winding resistance, L1 is the primary winding inductance, _L2 is the secondary winding inductance, _M is the mutual inductance between the primary and secondary windings, and i1 _{( t} ) and i ₂ (t) is the current in the primary side circuit and the secondary side circuit, R _load is the load resistance, L _load is the load inductance; I _{short1_1} is the value of the current i ₁ (0) in the primary side circuit when a short circuit occurs , and the value of the current i ₂ (0) in the secondary side circuit is 0 at this time.

When the current in the secondary side circuit drops to 0 and the secondary winding is open circuit, the secondary side winding no longer affects the electrical characteristics of the primary side winding through magnetic field coupling, then the primary side circuit and the secondary side circuit satisfy :

i ₁ (0)=I _{short3_1}

i ₂ (0)=I _{short3_2}

Wherein, the I _{short3_1} and I _{short3_2} are respectively the values of the current i ₁ (0) in the primary side circuit and the current i ₂ (0) in the secondary side circuit after the power electronic switch is closed.

Therefore, by analyzing the circuit operating characteristics of the above-mentioned different control stages, it can be known that the switching of the semiconductor devices in the control circuit is different, the current changes are different, and different equivalent impedances can be generated, so as to limit the fault current and protect the circuit.

Although the present utility model has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: it is still possible to modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements to some of the technical features; and These modifications or substitutions do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims (7)

1. A passive flexible DC power grid fault current limiter, characterized in that it comprises a primary side circuit and a secondary side circuit, wherein, the primary side circuit includes a primary winding; The secondary side circuit includes a secondary winding and one or more control circuits connected in series with it; The primary winding and the secondary winding are coupled through a magnetic field. 2 . The passive flexible DC grid fault current limiter according to claim 1 , wherein the one or more control circuits are connected in parallel. 3 . 3 . The passive flexible DC power grid fault current limiter according to claim 2 , wherein the one or more control circuits include at least a switch branch, a buffer branch and an energy absorption branch; wherein, The switch branch, buffer branch and energy absorption branch are connected in parallel. 4. The passive flexible DC grid fault current limiter according to claim 3, characterized in that, The switch branch includes two reversely connected solid-state switches, the solid-state switches include a semiconductor device and a diode, and the semiconductor device and the diode are in antiparallel; The energy absorption branch includes a lightning arrester. 5 . The passive flexible DC grid fault current limiter according to claim 4 , wherein the semiconductor device comprises IGCT and IGBT. 6 . 6 . The passive flexible DC power grid fault current limiter according to claim 4 , wherein the control circuit further comprises a load module, and the load module is respectively connected with the switch branch and the buffer branch. 7 . and the energy absorption branch in series, where, The load module is one of RL circuit, pure inductance circuit, pure resistance circuit, LC circuit, RCL circuit and RC circuit. 7 . The passive flexible DC grid fault current limiter according to claim 3 , wherein the buffer branch is an RC buffer circuit. 8 .

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