Adjustable manual zero-crossing loop topology for assisting on-off of direct-current circuit breaker

Abstract

The invention relates to an adjustable manual zero-crossing loop topology for assisting on-off of a direct-current circuit breaker. The pulse current can be flexibly adjusted under the working condition that the current amplitude of a main loop changes greatly, so that the on-off operation of the circuit breaker is assisted. The topological structure comprises a thyristor H bridge for controlling the current direction, and a discharge branch circuit connected in parallel at two ends of a direct current circuit breaker, wherein the branch circuit is formed by connecting a plurality of groups of capacitors and reactors in parallel. In the on-off process of the direct-current circuit breaker, the corresponding thyristors and the discharge switches are controlled to be switched on according to the amplitude of current in a main loop, the capacitor releases charges, and pulse current opposite to the current in the main circuit is generated through the electric reactor, so that the direct-current circuit breaker is assisted to complete on-off operation. According to the topological structure, the number of the input capacitors can be selected according to the amplitude of the main loop current, so that the reverse current matched with the main loop current is generated, and the switching-on and switching-off success rate of the circuit breaker is improved.

Description

Technical Field

[0001] The invention belongs to the field of direct current circuit breakers, and in particular relates to an adjustable artificial zero-crossing circuit topology for assisting the breaking of a direct current circuit breaker. Background Art

[0002] The breaking process of direct current is relatively complicated due to the lack of a natural zero-crossing point. At present, DC circuit breakers usually use artificial zero-crossing technology to generate zero current in the main circuit to assist the circuit breaker in completing the breaking operation. However, the existing artificial zero-crossing technology generally uses a single capacitor discharge to generate pulse current. When the circuit breaker is broken, the generated pulse current is a fixed value due to the fixed parameters of the discharge branch. Since the current value in the power system changes in real time, if the main circuit current does not match the current generated by the artificial zero-crossing circuit when the circuit breaker is broken, a large amplitude reverse current may appear. This situation may cause the arc to reignite, thereby shortening the life of the equipment and even causing breaking failure. Therefore, an artificial zero-crossing circuit that can be flexibly adjusted according to the operating conditions is of great significance to improving the reliable breaking performance of DC circuit breakers. Summary of the invention

[0003] The present invention aims to provide an adjustable artificial zero-crossing circuit topology structure for assisting the breaking of a DC circuit breaker, so as to solve the problem that the pulse current generated by the artificial zero-crossing circuit does not match the main circuit current in the prior art. The present invention configures multiple groups of capacitors in parallel, selects to turn on the corresponding capacitor group according to the amplitude of the main circuit current, thereby generating a reverse pulse current matching the amplitude of the main circuit current, so as to assist the DC circuit breaker in completing the breaking, and effectively avoid the reignition of the arc.

[0004] To achieve the above object, the present invention adopts the following technical solutions:

[0005] The invention discloses an adjustable artificial zero-crossing circuit topology for assisting the opening of a DC circuit breaker. When the DC circuit breaker is opened, the corresponding thyristor is turned on according to the direction of the main circuit current, and the corresponding capacitor is turned on according to the amplitude of the main circuit current to generate a matching reverse pulse current, thereby performing artificial zero-crossing to assist the opening of the DC circuit breaker.

[0006] The artificial zero crossing refers to generating a reverse pulse current through a pulse capacitor when the DC circuit is disconnected, so that the current amplitude in the main circuit is reduced to zero to assist the disconnection operation of the DC circuit breaker.

[0007] Furthermore, the capacitor bank includes a pulse capacitor to be precharged, a pulse reactor and a switching switch. In the present invention, a plurality of capacitor banks connected in parallel are provided.

[0008] Furthermore, the pulse current generated by the present invention is jointly determined by the parameters of the capacitor, the reactor and the capacitor bank put in. By controlling the discharge switch, the capacitor can be selectively put in, thereby flexibly adjusting the reverse pulse current.

[0009] Furthermore, in order to reduce system cost, the discharge switch involved in the present invention is usually a non-semiconductor switch such as a vacuum gap switch or a mechanical switch.

[0010] Furthermore, the pulse current generated by the present invention can obtain more amplitudes through the free combination of capacitors, and theoretically can generate up to The current waveform is shown in Figure 1, where n is the number of capacitors in parallel in the discharge circuit. Based on the superposition theorem, large currents can be provided by multiple capacitors with small capacitance values, which facilitates site layout and helps reduce capacitor costs.

[0011] Furthermore, when performing static configuration, the capacitance of the capacitor is related to the current amplitude in the main circuit, and the reverse current generated by the capacitor needs to cover the current value of the main circuit when it needs to be disconnected, ensuring that the main circuit can be disconnected at any time.

[0012] Furthermore, the capacitor in the discharge branch can generate a variety of reverse pulse currents with different amplitudes by reducing the pre-charge voltage value, thereby expanding the current output range of the artificial zero-crossing circuit.

[0013] Furthermore, in order to ensure that the artificial zero-crossing circuit quickly generates a reverse current that matches the main circuit operating conditions, the reverse current value generated by each capacitor is calculated in advance, and then combined according to the superposition theorem, sorted according to the amplitude, and the sorting results are written into the memory. When the main circuit needs to be disconnected, a reasonable capacitor combination is screened out in the memory according to the current value in the main circuit at this time, and then a trigger signal is sent to the discharge switch.

[0014] Compared with the prior art, the beneficial effects of the present invention include:

[0015] The present invention provides an adjustable artificial zero-crossing circuit topology structure for assisting the opening of a DC circuit breaker. By connecting multiple capacitor banks in parallel and selectively inputting them according to the amplitude of the main circuit current, the problem of mismatch between the main circuit current amplitude and the reverse pulse current generated by the artificial zero-crossing circuit when the DC circuit breaker is opened is effectively solved. The present invention has a simple structure and high efficiency, and significantly reduces the risk of arc reignition caused by excessive reverse pulse current in traditional artificial zero-crossing technology, thereby improving the reliability of the DC circuit breaker. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 A circuit diagram of the present invention;

[0017] Figure 2 It is a circuit diagram of the pulse capacitor group in the present invention. DETAILED DESCRIPTION

[0018] Embodiments of the present invention will be described below with reference to the accompanying drawings, but it should be understood that these descriptions are only exemplary and are not intended to limit the scope of the present invention.

[0019] The present invention provides an adjustable artificial zero-crossing circuit topology for assisting the opening of a DC circuit breaker, which is intended to generate reverse pulse currents with different parameters to assist the opening and closing operation of the DC circuit breaker. The artificial zero-crossing is to generate pulse currents by using energy storage elements such as capacitors to offset the current in the main circuit, thereby providing an effective zero-crossing point for the opening and closing of the DC circuit breaker.

[0020] The artificial zero-crossing topology includes a thyristor H-bridge and multiple capacitor groups that can generate pulse currents. The thyristor H-bridge is used to adjust the direction of the pulse current in the main circuit, while the multiple capacitor groups generate pulse currents with different parameters according to their switching conditions. By adjusting the different parameters and number of capacitor groups, a reverse pulse current that adapts to the main circuit current can be generated, thereby improving the matching degree.

[0021] The topological circuit structure of the artificial zero-crossing circuit for auxiliary DC circuit breaker opening and closing of the adjustable circuit of the present invention is as follows: Figure 1 As shown in the figure, the thyristor VT 1 To VT 4 The H-bridge formed determines the current direction of the discharge branch in the main circuit. Each separate discharge branch is composed of a discharge switch, a capacitor and a reactor in series. The capacitor needs to be precharged before discharging to generate a predictable pulse current. When the DC circuit breaker is disconnected, according to the amplitude of the main circuit current, the corresponding switches S1 to Sn are controlled to close to generate a reverse pulse current matching the main circuit current to achieve artificial zero crossing.

[0022] In order to reduce system cost, the discharge switch involved in the present invention is usually a non-semiconductor switch such as a vacuum gap switch or a mechanical switch.

[0023] The circuit structure of the discharge branch is as follows: Figure 2 As shown. Each discharge branch is composed of a pulse reactor L, an energy storage capacitor C and an auxiliary discharge switch element S in series, and multiple branches are connected in parallel to the two ends of the DC circuit breaker through a thyristor H bridge. Before the circuit breaker is disconnected, the capacitor C needs to be pre-charged to a predetermined voltage to prepare for the operation of the discharge branch.

[0024] Assume that the pulse current generated by each discharge branch is ,and Capacitors and inductors are both linear components, and the superposition theorem can be used to calculate the current value. According to the principle of permutation and combination, the discharge branch can generate By sorting the amplitudes of all combined pulse currents, it is possible to determine which discharge switches are closed based on the amplitude of the current in the main circuit when the switch is turned off.

[0025] In order to reduce investment costs, when configuring the installation capacity of the pulse capacitor, the amplitude distribution of the load current in the main circuit must be considered to ensure that the reverse pulse current generated by the artificial zero-crossing circuit can meet the breaking requirements of the main circuit under all working conditions. Without considering the nonlinearity of the components, the reverse pulse currents generated by different pulse capacitors can be linearly superimposed by the superposition theorem.

[0026] The capacitors in the discharge branch can be pre-charged with different voltages respectively, which can effectively expand the amplitude range of the reverse pulse current without changing the hardware.

[0027] In order to ensure that the main circuit is disconnected quickly, the artificial zero-crossing circuit needs to quickly generate a reverse current that matches the main circuit operating conditions. Therefore, it is necessary to calculate the reverse current value generated by each capacitor, and then combine them according to the superposition theorem, sort them according to the amplitude, and write the results into the memory. When the main circuit needs to be disconnected, according to the current value in the main circuit at this time, a reasonable capacitor combination is screened in the memory, and then a trigger signal is sent to the discharge switch.

[0028] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. These embodiments are only for the purpose of illustration, and are not intended to limit the scope of the present invention. The scope of the present invention is defined by the appended claims and their equivalents. Without departing from the scope of the present invention, those skilled in the art may make various substitutions and modifications, which should all fall within the scope of the present invention.

Claims

1. An adjustable artificial zero-crossing circuit topology for auxiliary DC circuit breaker disconnection, characterized in that: An adjustable discharge branch composed of multiple sets of discharge branches in parallel and an H-bridge composed of thyristors are connected in parallel to the two ends of the DC circuit breaker; under the condition that the amplitude of the main circuit current changes rapidly, the discharge branch is adjusted to output a reverse pulse current matching the main circuit current, thereby assisting the breaking of the DC circuit breaker.

2. The adjustable artificial zero-crossing circuit topology for auxiliary DC circuit breaker breaking according to claim 1 is characterized in that: The discharge branch is composed of a plurality of branches connected in parallel, wherein each branch includes a discharge switch, a reactor and a capacitor arranged in series.

3. The adjustable artificial zero-crossing circuit topology for auxiliary DC circuit breaker breaking according to claim 1, characterized in that: The discharge branch is controlled according to the current value of the main circuit, and the discharge switch in the branch is adjusted.

4. The adjustable artificial zero-crossing circuit topology for auxiliary DC circuit breaker breaking according to claim 1 is characterized in that: By superimposing the discharge currents of a single discharge branch, a corresponding pulse current waveform is formed to achieve artificial zero crossing.

5. The adjustable artificial zero-crossing circuit topology for auxiliary DC circuit breaker breaking according to claim 1, characterized in that: The H bridge includes four thyristors, namely VT1, VT2, VT3, and VT4; the discharge branch is connected between the midpoint of the line connecting VT1 and VT2 and the midpoint of the line connecting VT3 and VT4.

6. The adjustable artificial zero-crossing circuit topology for auxiliary DC circuit breaker breaking according to claim 4 is characterized in that: The pulse current generated by each discharge branch is ,and , the discharge branch generates Pulse current of this amplitude.

7. The adjustable artificial zero-crossing circuit topology for auxiliary DC circuit breaker breaking according to claim 2, characterized in that: The discharge switch is a non-semiconductor switch, and may be a vacuum gap switch or a mechanical switch.

8. The adjustable artificial zero-crossing circuit topology for auxiliary DC circuit breaker breaking according to claim 2 is characterized in that: The reverse current value generated by each capacitor is calculated, then combined, sorted according to the amplitude, and the sorting result is written into the memory. When the main circuit needs to be disconnected, a reasonable capacitor combination is screened out in the memory according to the current value in the main circuit at this time, and then a trigger signal is sent to the discharge switch.

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