Hybrid direct-current circuit breaker based on magnetic integration and efficient switching-on and switching-off method of hybrid direct-current circuit breaker

Abstract

The invention discloses a hybrid direct-current circuit breaker based on magnetic integration and an efficient breaking method thereof, and relates to the technical field of circuit breakers, the hybrid direct-current circuit breaker is arranged on a main branch of a direct-current system, the direct-current circuit breaker comprises a through-current branch, a transfer branch and a dissipation branch which are arranged in parallel, and a coil L1 is arranged on the main branch in series; a coil L2 and a mechanical switch S1 are arranged on the through-current branch in series, a coil L3 and a power electronic device IGBT are arranged on the transfer branch in series, and a lightning arrester MOV is arranged on the dissipation branch. Wherein the coil L1 and the coil L2 form a dotted terminal coupling inductor, and the coil L1 and the coil L3 form a synonym terminal coupling inductor. According to the hybrid direct-current circuit breaker based on magnetic integration and the efficient breaking method thereof, the fault current value in the breaking process can be effectively reduced, the voltage borne by the mechanical switch is reduced, and the breaking duration is shortened.

Description

Technical Field

[0001] The present invention relates to the technical field of circuit breakers, and in particular to a hybrid direct current circuit breaker based on magnetic integration and a high-efficiency breaking method thereof. Background Art

[0002] With the increasing demand for renewable energy, the installed capacity of photovoltaic power generation has continued to grow, resulting in a continuous increase in system voltage levels. Traditional molded case DC circuit breakers cannot extinguish arcs at higher voltages, and the DC short-circuit failures of photovoltaic power generation expansion need to be solved in a timely manner. Hybrid DC circuit breakers show excellent performance in high-voltage scenarios, but when the photovoltaic voltage level rises, it is difficult to extinguish arcs with circuit breakers for DC 1500V-3000V photovoltaic and energy storage systems, and there are few mature products. Summary of the invention

[0003] The purpose of the present invention is to provide a hybrid DC circuit breaker based on magnetic integration and a breaking method thereof, which can effectively reduce the fault current value during the breaking process, reduce the voltage borne by the mechanical switch, and shorten the breaking time.

[0004] To achieve the above object, the present invention provides a hybrid DC circuit breaker based on magnetic integration, which is arranged on the main branch of the DC system, including a current-carrying branch, a transfer branch and a dissipation branch arranged in parallel, and a coil L is arranged in series on the main branch. 1 , a coil L is arranged in series on the current branch 2 , Mechanical switch S 1 , a coil L is arranged in series on the transfer branch 3 , power electronic device IGBT, a lightning arrester MOV is set on the dissipation branch; among them, the coil L 1 With coil L 2 Composed of the same-name end coupled inductor, coil L 1 With coil L 3 Form a coupled inductor with opposite ends.

[0005] Preferably, the DC system is a DC1500V-DC3000V system, and the rated voltage of the hybrid DC circuit breaker is DC1500V-DC3000V.

[0006] Preferably, coil L 1 、Coil L 2 With coil L 3 Wound on the Japanese-shaped core, the coil L 1 Wrapped around one of the side columns of the Japanese-shaped core, the coil L 1 The starting end A is connected to the power supply end of the main branch; Coil L 2 The coil L is divided into two parts and wound on the two side columns of the Japanese-shaped iron core. 2The starting end C is wound around the other side column of the Japanese-shaped core, and the number of winding turns is N. 21 , coil L 2 The end D is wound around the coil L 1 The number of winding turns on the winding side column is N 22 , N 21 =N 22 , coil L 2 The end D and the mechanical switch S 1 connect; Coil L 3 Wrapped around the middle column of the Japanese-shaped iron core, the coil L 3 The starting end E is connected to the power electronic device IGBT, and the coil L 1 The end B, coil L 2 The starting point C, coil L 3 The ends F are connected.

[0007] An efficient breaking method of a hybrid DC circuit breaker based on magnetic integration, comprising: When the circuit is flowing normally, the mechanical switch S 1 Closed, current only flows through the current branch; When a short circuit fault occurs, the total voltage flowing through the current branch rises to the forward conduction voltage of the power electronic device IGBT, triggering the power electronic device IGBT to turn on, and the fault current is commutated from the current branch to the transfer branch, and the coil L 2 When the power is turned on, a negative voltage opposite to the on-state voltage drop of the power electronic device IGBT is generated, thereby reducing the voltage of the transfer branch; When the current in the conducting branch drops to zero, the mechanical switch S 1 The transfer branch is opened and current is commutated to the dissipation branch; When the transfer branch current drops to zero, the arrester MOV performs voltage clamping and inductive energy dissipation.

[0008] According to the specific embodiments provided by the present invention, the present invention discloses the following technical effects: (1) The voltage at both ends of the current-carrying branch is increased to the IGBT conduction voltage to achieve current transfer and complete fault interruption; (2) Coils with coupled inductance are connected in series in the main branch, the flow branch, and the transfer branch. The inductance in the flow branch greatly advances the turn-on time of the IGBT. The coils in the main branch and the flow branch can limit the total short-circuit current, while reducing the current flowing through the mechanical switch of the flow branch and increasing the life of the mechanical switch. By coupling the opposite-terminal terminals of the coils in the main branch, the coils in the transfer branch generate a negative voltage opposite to the on-state voltage drop of the power electronic device, thereby reducing the voltage of the entire transfer branch and ensuring reliable current transfer.

[0009] (3) By using magnetic integrated decoupling technology, the coil is set on the Japanese-shaped iron core, which reduces the volume and weight of the circuit breaker and ensures that the two coupled inductors are not affected by each other during operation.

[0010] (4) According to calculations, during the fault interruption process of the DC system, the peak current of the flow branch was reduced by 58.47%, the peak current of the transfer branch was reduced by 41.2%, and the interruption time was shortened by 28.39%. This greatly reduces the peak fault current that the mechanical switch and IGBT need to withstand, increases the service life of the circuit breaker, and reduces the specifications and quantity of the IGBT.

[0011] (5) It can be used for efficient breaking of large currents, which improves the breaking capacity of the original hybrid DC circuit breaker and has better breaking characteristics in the DC system.

[0012] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0014] Figure 1 A schematic diagram of the topological structure of an embodiment of a hybrid DC circuit breaker based on magnetic integration according to the present invention; Figure 2 A schematic diagram of a coupled inductor magnetic integrated structure according to an embodiment of the present invention; Figure 3 A schematic diagram of the topological structure of a self-touch hybrid DC circuit breaker according to Comparative Example 1 of the present invention; Figure 4 The breaking characteristics of the self-contacting hybrid DC circuit breaker breaking a 50kA fault current in a DC1500V system in Comparative Example 1 of the present invention; Figure 5 A schematic diagram of the topological structure of a hybrid DC circuit breaker with integrated inductance according to Comparative Example 1 of the present invention; Figure 6 The breaking characteristics of the hybrid DC circuit breaker with integrated inductance of comparative example 1 of the present invention when breaking a 50kA fault current in a DC1500V system; Figure 7 Schematic diagram of the topological structure of a hybrid DC circuit breaker based on coupled inductance according to Comparative Example 2 of the present invention; Figure 8The breaking characteristics of the hybrid DC circuit breaker based on coupled inductance in comparative example 2 of the present invention when breaking a 50kA fault current in a DC1500V system; Fig. 9 The invention discloses a breaking characteristic of a hybrid DC circuit breaker based on magnetic integration for breaking a 50kA fault current in a DC1500V system. DETAILED DESCRIPTION

[0015] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0016] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments. Example

[0017] like Figure 1 As shown in the figure, a hybrid DC circuit breaker based on magnetic integration is arranged on the main branch of the DC system, with a rated voltage of DC1500V-DC3000V, and is applied to the DC1500V-DC3000V system. The DC circuit breaker includes a current-carrying branch, a transfer branch and a dissipation branch arranged in parallel, and a coil L is arranged in series on the main branch. 1 , a coil L is arranged in series on the current branch 2 , Mechanical switch S 1 , a coil L is arranged in series on the transfer branch 3 , power electronic device IGBT, and a lightning arrester MOV is installed on the dissipation branch. Coil L 1 With coil L 2 Composed of the same-name end coupled inductor, coil L 1 With coil L 2 The mutual inductance coefficient is M 1 , coil L 1 With coil L 3 Composed of opposite-terminal coupled inductors, coil L 1 With coil L 3 The mutual inductance coefficient is M 2 .

[0018] Coupled inductor integrated structure such as Figure 2 As shown, coil L 1 、Coil L 2 With coil L 3 Wound on the Japanese-shaped core, the coil L 1 Wrapped around one of the side columns of the Japanese-shaped iron core, Figure 2 Middle coil L 1 The A end and Figure 1 The coil L 2 The coil L is divided into two parts and wound on the two side columns of the Japanese-shaped iron core. 2 The starting end C is wound around the other side column of the Japanese-shaped core, and the number of winding turns is N. 21 , coil L 2 The end D is wound around the coil L 1 The number of winding turns on the winding side column is N 22 , N 21 =N 22 , coil L 2 The end D and the mechanical switch S 1 Connected.

[0019] Coil L 3 Wrapped around the middle column of the Japanese-shaped iron core, the coil L 3 The E end and Figure 1 The IGBTs in the Figure 2 The coil L 1 The B end of the coil L 2 C end, coil L 3 The F end and Figure 1 The coil L 1 、Coil L 2 and coil L 3 The common node is connected. 2 With coil L 3 Decoupling is achieved by completely canceling out the magnetic flux between the windings. The integrated structure of the coupled inductor not only realizes the structural integration of the two coupled inductors, reducing the volume and weight of the entire hybrid circuit breaker, but also realizes functional decoupling, ensuring that the two coupled inductors are not affected by each other during operation.

[0020] The efficient breaking method based on the hybrid DC circuit breaker includes: When the circuit is flowing normally, the mechanical switch S 1 When closed, the current only flows through the current branch, and the loss caused by the mechanical switch is small.

[0021] When a short circuit fault occurs, the fault current begins to rise. When the mechanical switch receives the trip signal, the moving and static contacts begin to separate to generate an arc. As the distance between the moving and static contacts increases, the arc voltage increases. At the same time, the inductance on the current branch also generates a voltage, which together constitutes the total voltage of the current branch. When the total voltage of the current branch rises to the forward conduction voltage of the power electronic device IGBT, the IGBT is triggered to turn on, and the fault current is commutated from the current branch to the transfer branch. The coupled inductors of the same name installed on the main branch and the current branch can limit the total current, while greatly reducing the current flowing through the mechanical switch of the current branch, reducing the voltage borne by the mechanical switch, and increasing the life of the mechanical switch. During the current transfer process, the voltage of the transfer branch is required not to be higher than the arc voltage of the mechanical switch of the current branch, otherwise it will cause the current transfer speed to be slow, and the higher voltage will cause the arc gap of the mechanical switch to reignite, resulting in the failure of the current transfer. Coil L 2 When power is turned on, a negative voltage opposite to the on-state voltage drop of the power electronic device IGBT is generated, which reduces the voltage of the transfer branch, ensures the reliable transfer of current, and speeds up the transfer of fault current from the flow branch to the transfer branch.

[0022] When the current in the conducting branch drops to zero, the mechanical switch S 1 The transfer branch is opened and current is commutated to the dissipation branch.

[0023] When the transfer branch current drops to zero, the arrester MOV performs voltage clamping and inductive energy dissipation.

[0024] The beneficial effects of the circuit structure of the present application are verified by two sets of comparative experiments. The experimental monitoring is carried out in the process of breaking a 50kA fault current in a DC1500V system, and the breaking characteristics of the circuit are measured. Comparative experiment 1

[0025] In such Figure 3 In the structure without series inductance shown in the figure, the measurement results are as follows Figure 4 As shown, the peak current of the flow branch is 27.57kA, the peak current of the transfer branch is 35.38kA, and the fault interruption is completed within 14.55ms.

[0026] In such Figure 5 In the hybrid DC circuit breaker structure with integrated inductor in the current branch shown in FIG, the self-inductance coefficient of the coil is L=50uH. The measurement results are shown in Figure 6As shown in the figure, the peak current of the flow branch is 18.31kA, the peak current of the transfer branch is 36.84kA, and the entire fault interruption process is 16.4ms. Compared with before and after the inductor is connected in series with the flow branch, the peak current of the flow branch is reduced by 33.59%, the peak current of the transfer branch is increased by 3.97%, and the interruption time is increased by 11.28%. When the integrated inductor is connected in series with the flow branch, when a fault occurs and the current is not large enough and the arc voltage is too small, the voltage generated on the inductor can be used to trigger the IGBT, advance the IGBT turn-on time, greatly advance the turn-on time of the transfer branch, and reduce the voltage borne by the mechanical switch. However, the decrease in the commutation rate leads to an increase in the commutation time, which prolongs the entire interruption time. Comparative experiment 2

[0027] From Comparative Example 1, it can be seen that connecting an inductor in series with the flow branch can reduce the fault current peak of the flow branch, but the current peak of the transfer branch increases, and the inductor on the flow branch is difficult to suppress the current rising rate in the transfer branch. Figure 7 The primary and secondary coils of the coupled inductor shown in the figure are connected in series in the structure of the main branch and the current branch respectively. The self-inductance coefficients of the primary and secondary coils are L 1 =150uH, L 2 =50uH, its mutual inductance coefficient M=52uH. The measurement results are as follows Figure 8 As shown in the figure, the peak current of the flow branch is 11.35kA, the peak current of the transfer branch is 22.22kA, and the fault is disconnected within 12.02ms. From the disconnection characteristics, it can be seen that this structure can reduce the current of each branch at the same time during the disconnection process, reducing the current peak borne by the mechanical switch. Compared with the structure with only the inductor in series in the flow branch, the peak current of the flow branch is reduced by 38%, the peak current of the transfer branch is reduced by 39.7%, and the disconnection time is shortened by 26.71%.

[0028] like Fig. 9 As shown, in the structure proposed in the embodiment of the present application, the primary and secondary coils of the first coupled inductor are connected in series in the main branch and the current branch respectively, and the primary and secondary coils of the second coupled inductor are connected in series in the main branch and the transfer branch respectively, and the self-inductance coefficients of the three coils are L 1 =150uH, L 2 =50uH, L 3 =5uH, coil L 1 With coil L 2 The mutual inductance coefficient is M 1 =52 uH, coil L 1 With coil L 3 The mutual inductance coefficient M 2 =22 uH. The measurement results are as follows Fig. 9As shown, the peak current of the flow branch is 11.45kA, and the peak current of the transfer branch is 20.8kA. The fault interruption is completed within 10.42ms. From the interruption characteristics, it can be obtained that the coil on the transfer branch generates a negative pressure opposite to the on-state voltage drop of the power electronic device by coupling the opposite ends with the coil on the main branch, thereby reducing the voltage of the entire transfer branch, accelerating the conversion of current to the transfer branch, and shortening the interruption time.

[0029] Therefore, compared with the structure in which the primary and secondary coils of the coupled inductor are connected in series with the main branch and the current branch respectively, the hybrid DC circuit breaker topology structure based on magnetic integration proposed in this application reduces the peak current of the transfer branch by 6.37% and shortens the breaking time by 13.31%; compared with the structure without series inductor, the peak current of the current branch is reduced by 58.47%, the peak current of the transfer branch is reduced by 41.2%, and the breaking time is shortened by 28.39%. The fault current peak that the mechanical switch and IGBT need to withstand is greatly reduced, the service life of the circuit breaker is increased, and the specifications and quantity of the IGBT are reduced.

[0030] The remaining technical features in the above embodiments can be flexibly selected by those skilled in the art according to actual conditions to meet different specific practical needs. However, it is obvious to those skilled in the art that it is not necessary to adopt these specific details to implement the present invention. In other examples, in order to avoid confusing the present invention, the well-known components, structures or parts are not specifically described, which are all within the technical protection scope defined by the technical solution claimed for protection in the claims of the present invention.

[0031] Modifications and changes made by those skilled in the art that do not depart from the spirit and scope of the present invention should be within the scope of protection of the claims attached to the present invention. In the above description, a large number of specific details are set forth in order to provide a thorough understanding of the present invention. However, it is obvious to those of ordinary skill in the art that these specific details are not necessary to practice the present invention. In other examples, in order to avoid confusing the present invention, well-known technologies, such as specific construction details, operating conditions and other technical conditions, are not specifically described.

[0032] The principles and implementation methods of the present invention are described in this article using specific examples. The description of the above embodiments is only used to help understand the method and core idea of ​​the present invention. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A hybrid DC circuit breaker based on magnetic integration, arranged on the main branch of a DC system, characterized in that: It includes a current-passing branch, a transfer branch and a dissipation branch connected in parallel, a coil L1 is connected in series on the main branch, a coil L2 and a mechanical switch S1 are connected in series on the current-passing branch, a coil L3 and a power electronic device IGBT are connected in series on the transfer branch, and a lightning arrester MOV is connected on the dissipation branch; wherein the coil L1 and the coil L2 form a coupling inductor with the same name, and the coil L1 and the coil L3 form a coupling inductor with different name.

2. The hybrid DC circuit breaker based on magnetic integration according to claim 1, characterized in that: The DC system is a DC1500V-DC3000V system, and the rated voltage of the hybrid DC circuit breaker is DC1500V-DC3000V.

3. The hybrid DC circuit breaker based on magnetic integration according to claim 2, characterized in that: Coil L1, coil L2 and coil L3 are wound on the Japanese-shaped iron core, coil L1 is wound on one of the side pillars of the Japanese-shaped iron core, and the starting end A of coil L1 is connected to the power supply end of the main branch; The coil L2 is divided into two parts and wound on the two side legs of the Japanese-shaped core. The beginning C of the coil L2 is wound on the other side leg of the Japanese-shaped core. The number of winding turns is N. 21 The end D of coil L2 is wound around the side column around which coil L1 is wound, and the number of turns is N. 22 , N 21 =N 22 ; The coil L3 is wound on the middle column of the Japanese-shaped iron core, the starting end E of the coil L3 is connected to the power electronic device IGBT, and the end B of the coil L1, the end C of the coil L2, and the end F of the coil L3 are connected.

4. An efficient breaking method for a hybrid DC circuit breaker based on magnetic integration, applied to a hybrid DC circuit breaker based on magnetic integration as claimed in any one of claims 1 to 3, characterized in that: include: When the circuit is flowing normally, the mechanical switch S1 is closed and the current only flows through the current branch; When a short circuit fault occurs, the total voltage flowing through the current branch rises to the forward conduction voltage of the power electronic device IGBT, triggering the power electronic device IGBT to turn on, and the fault current is commutated from the current branch to the transfer branch. The coil L2 is energized to generate a negative voltage opposite to the on-state voltage drop of the power electronic device IGBT, reducing the voltage of the transfer branch; When the current in the conduction branch drops to zero, the mechanical switch S1 is opened, and the transfer branch commutates to the dissipation branch; When the transfer branch current drops to zero, the arrester MOV performs voltage clamping and inductive energy dissipation.

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