Direct current combination switch and control method of direct current combination switch

Abstract

The application relates to a direct-current combined switch and a control method thereof, and belongs to the technical field of direct-current power systems.The direct-current combined switch comprises a comprehensive control unit, a current detection unit, a fast breaking unit and a load switch; the fast breaking unit comprises a parallelly-connected voltage-limiting energy-dissipating branch, a current transfer branch, a main switch branch and a forced commutation branch; the forced commutation branch comprises an inductor, a capacitor, a third thyristor, a fourth thyristor, a fifth thyristor and a sixth thyristor; the current detection unit is used for collecting a current value and a current change rate of a power system; and the comprehensive control unit is used for controlling breaking states of the load switch and the main switch branch based on the current value and the current change rate.The direct-current combined switch provided by the application has the advantages of fast short-circuit protection breaking speed, high reliability, strong current-limiting capability and high breaking life, and is suitable for occasions, such as a direct-current power system bus connection, which need fast breaking protection.

Description

Technical Field

[0001] This invention relates to the field of DC power system technology, and in particular to a DC combined switch and a control method for the DC combined switch. Background Technology

[0002] Parallel operation of busbars is an important measure to improve the reliability of power supply in a power system. When a short-circuit fault occurs in the equipment on one of the busbars, the system current rises rapidly. At this time, it is necessary to immediately disconnect the busbar connecting circuit breaker to break the circuits of both busbars, so as to prevent the upstream circuit breaker on the non-faulty side from tripping erroneously and causing a large-scale power outage. Therefore, the bus tie circuit breaker requires a very high breaking speed and should also have current limiting functions.

[0003] In DC power systems, transmission lines are short, loop impedance is low, and short-circuit time constants are small. Once a short-circuit fault occurs, the current rises to its peak value within milliseconds. However, existing air circuit breakers typically have an inherent tripping delay of over 10 milliseconds. Firstly, they cannot meet the speed requirements in terms of breaking speed. Secondly, when an air circuit breaker opens, the short-circuit current is often close to its peak value, lacking current-limiting functionality, making it difficult for upstream and downstream circuit breakers to provide matched protection. When a short-circuit fault occurs in equipment on one busbar, it may cause the upstream circuit breakers of two bus couplers to trip simultaneously, resulting in a large-scale power outage. Furthermore, air circuit breakers rely on arc burning to break short circuits, generally having a short high-current breaking life and requiring frequent replacement of the arc chamber and contacts.

[0004] Both hybrid circuit breakers and solid-state circuit breakers have fast breaking speeds and good current-limiting capabilities. However, solid-state circuit breakers have an inherent drawback of severe rated current-carrying losses, making them unsuitable for high-current systems. Hybrid circuit breakers, on the other hand, have extremely high fast mechanical switching speeds, resulting in severe wear and making it difficult to match the mechanical lifespan of air circuit breakers. Furthermore, hybrid circuit breakers lack mechanical breaks, posing safety hazards during maintenance of faulty branches. Additionally, the mechanical switches of existing hybrid circuit breakers are generally based on the principle of electromagnetic repulsion, requiring tens of milliseconds after closing to restore their tripping latching capability, making it difficult to independently meet the fault protection requirements under the "CO" condition of the system. Summary of the Invention

[0005] In view of this, it is necessary to provide a DC combined switch and a control method for the DC combined switch, so as to achieve the goal of quickly disconnecting two parallel-operating busbars during short-circuit breaking, thereby improving the stability and reliability of power supply in the power system.

[0006] To achieve the above objectives, in a first aspect, the present invention provides a DC combination switch, comprising: Integrated control unit, current detection unit, fast disconnection unit, and load switch; The integrated control unit, the current detection unit, the fast disconnection unit, and the load switch are connected in sequence; The rapid disconnection unit includes a voltage limiting and energy dissipation branch, a current transfer branch, a main switch branch, and a forced commutation branch connected in parallel. The current transfer branch includes: a first thyristor and a second thyristor connected in reverse parallel. The forced commutation branch includes: an inductor, a capacitor, a third thyristor, a fourth thyristor, a fifth thyristor, and a sixth thyristor; The inductor and the capacitor are connected in series to form the first branch; The anodes of the third thyristor and the fourth thyristor are connected to form a second branch; The cathodes of the fifth thyristor and the sixth thyristor are connected to form a third branch; The second branch and the third branch are connected in parallel; The connection nodes of the third thyristor and the fourth thyristor, and the connection nodes of the fifth thyristor and the sixth thyristor are respectively connected to the two ends of the first branch. The first end of the main switch branch is connected to the current detection unit, and the second end of the main switch branch is connected to the load switch; The current detection unit is used to collect the current value and current change rate of the power system; The integrated control unit is used to control the opening and closing states of the load switch and the main switch branch based on the current value and the current change rate.

[0007] In one possible implementation, the main switch branch includes a fast mechanical switch.

[0008] In one possible implementation, the load switch is a two-pole air switch.

[0009] In one possible implementation, the voltage-limiting energy-dissipating branch includes a varistor.

[0010] In one possible implementation, the current detection unit includes a current change rate sensor and a Hall current sensor.

[0011] Secondly, the present invention also provides a control method for a DC combined switch, applied to the DC combined switch described in any of the above implementations, comprising: When the power system is under short-circuit protection, the integrated control unit detects that the current value or current change rate has reached the protection setting value. Based on the current direction, it controls the fast disconnection unit to cut off the system current and controls the load switch to disconnect, forming a mechanical break.

[0012] In one possible implementation, the step of controlling the rapid disconnection unit to turn off the system current according to the current direction and controlling the load switch to disconnect, forming a mechanical break, includes: When the current flows from the main switch branch to the load switch, the integrated control unit sends a trip command to the main switch branch and a conduction command to the first thyristor, so that the fault current is transferred from the main switch branch to the first thyristor of the current transfer branch. After the current transfer is completed, the integrated control unit sends a turn-on command to the fourth and fifth thyristors to enable the fault current to be applied to the forced commutation branch. When the current in the first thyristor crosses zero and is turned off under the action of a negative voltage, the capacitor is charged. When the voltage across the capacitor rises to the voltage across the varistor, the varistor turns on, causing the current to transfer to the voltage-limiting and energy-dissipating branch and then drop to zero.

[0013] In one possible implementation, the step of controlling the rapid disconnection unit to turn off the system current according to the current direction and controlling the load switch to disconnect, forming a mechanical break, includes: When the current flows from the load switch to the main switch branch, the integrated control unit sends a trip command to the main switch branch and a conduction command to the second thyristor, so that the fault current is transferred from the main switch branch to the second thyristor of the current transfer branch. After the current transfer is completed, the integrated control unit sends a turn-on command to the third and sixth thyristors to enable the fault current to be applied to the forced commutation branch. When the current in the second thyristor crosses zero and is turned off under the action of a negative voltage, the capacitor is charged. When the voltage across the capacitor rises to the voltage across the varistor, the varistor turns on, causing the current to transfer to the voltage-limiting and energy-dissipating branch and then drop to zero.

[0014] One possible implementation also includes: When the integrated control unit receives the closing command from the power system, it controls the main switch branch to close, and after a preset time, controls the load switch to close. When the power system is operating at or below its rated value, the main switch branch and load switch are used to carry the system current. When a disconnection operation is required, the integrated control unit sends a disconnection command to the load switch to cut off the main circuit current and form a mechanical break.

[0015] One possible implementation also includes: When the power system is under overload conditions, the integrated control unit sends a disconnection command to the load switch to complete the overload protection and form a mechanical disconnection.

[0016] The beneficial effects of this invention are as follows: The DC combined switch and its control method provided by this invention can achieve current interruption under different operating conditions by controlling different components. It fully integrates the advantages of load switches (long breaking life under low current) and hybrid circuit breakers (fast breaking speed, high breaking capacity, strong current limiting capability, and long life under high current), resulting in extremely low conduction losses under rated current conditions. Under short-circuit conditions, it exhibits fast breaking speed and high current limiting level, facilitating matching protection with upstream circuit breakers and improving the stability and reliability of power supply. This invention possesses significant advantages such as fast short-circuit protection breaking speed, high reliability, strong current limiting capability, and long breaking life, making it suitable for applications requiring rapid breaking protection, such as busbar connections in DC power systems. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 A schematic diagram of an embodiment of the DC combination switch provided by the present invention; Figure 2 A schematic diagram of the current waveform of the circuit breaker provided by the present invention during the breaking process under rated and overload conditions; Figure 3 This is a schematic diagram of the current waveform of the circuit breaker during short-circuit protection provided by the present invention. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0020] In the description of the embodiments of the present invention, unless otherwise stated, "multiple" means two or more. "And / or" describes the relationship between related objects, indicating that there can be three relationships. For example, A and / or B can represent three situations: A exists alone, A and B exist simultaneously, and B exists alone.

[0021] The terms "first," "second," etc., used in the embodiments of this invention are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a technical feature defined with "first" or "second" may explicitly or implicitly include at least one of that feature.

[0022] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of the invention. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0023] This invention provides a DC combination switch and a control method for the DC combination switch, which will be described below.

[0024] Figure 1 A schematic diagram of an embodiment of the DC combined switch provided by the present invention is shown below. Figure 1 As shown, the DC combination switch includes: Integrated control unit, current detection unit, fast disconnection unit, and load switch; The integrated control unit, the current detection unit, the fast disconnection unit, and the load switch are connected in sequence; The rapid disconnection unit includes a voltage limiting and energy dissipation branch, a current transfer branch, a main switch branch, and a forced commutation branch connected in parallel. The current transfer branch includes: a first thyristor and a second thyristor connected in reverse parallel. The forced commutation branch includes: an inductor, a capacitor, a third thyristor, a fourth thyristor, a fifth thyristor, and a sixth thyristor; The inductor and the capacitor are connected in series to form the first branch; The anodes of the third thyristor and the fourth thyristor are connected to form a second branch; The cathodes of the fifth thyristor and the sixth thyristor are connected to form a third branch; The second branch and the third branch are connected in parallel; The connection nodes of the third thyristor and the fourth thyristor, and the connection nodes of the fifth thyristor and the sixth thyristor are respectively connected to the two ends of the first branch. The first end of the main switch branch is connected to the current detection unit, and the second end of the main switch branch is connected to the load switch; The current detection unit is used to collect the current value and current change rate of the power system; The integrated control unit is used to control the opening and closing states of the load switch and the main switch branch based on the current value and the current change rate.

[0025] like Figure 1 As shown, the DC combined switch includes a comprehensive control unit, a current detection unit, a fast disconnection unit, and a load switch.

[0026] The fast-breaking unit is a hybrid circuit breaker, which includes a parallel voltage-limiting and energy-dissipating branch, a current transfer branch, a main switch branch, and a forced commutation branch.

[0027] The current transfer branch includes: a first thyristor T1 and a second thyristor T2 connected in reverse parallel.

[0028] The forced commutation branch includes: inductor L, capacitor C, third thyristor T3, fourth thyristor T4, fifth thyristor T5, and sixth thyristor T6.

[0029] The integrated control unit is based on a high-speed real-time data acquisition and processing system, used to comprehensively analyze the status of the bus tie switch and send protection tripping commands according to system requirements.

[0030] For example, after receiving the closing command from the system, the integrated control unit first closes the main switch branch S1. After a delay of about 0.1 seconds, once the main switch branch has completed closing and the locking mechanism has completed resetting and is capable of opening, the load switch S2 is then closed, and the main circuit is connected.

[0031] Under rated and below operating conditions, the system current is carried by the main switch branch S1 and the load switch S2. When a disconnection operation is required, the integrated control unit sends a disconnection command to the load switch S2 to cut off the main circuit current and form a mechanical break.

[0032] After an overload occurs and the system protection requirements are met, the integrated control unit sends a load switch S2 disconnect command to complete the overload protection and form a mechanical break.

[0033] During short-circuit protection operation, current setting value protection and d are adopted. i / d t The settings work together for protection. When any setting reaches the protection setting value, the integrated control unit controls the fast disconnect unit to quickly cut off the system current. Then, a disconnect command is sent to the load switch S2 to open it in a zero-current state, forming a mechanical break.

[0034] In summary, the DC combined switch provided by this invention can achieve current interruption under different operating conditions by controlling different components. It fully integrates the advantages of load switches (long breaking life under low current) and hybrid circuit breakers (fast breaking speed, high breaking capacity, strong current limiting capability, and long life under high current), exhibiting extremely low conduction losses under rated current conditions. Under short-circuit conditions, it offers fast breaking speed and high current limiting level, facilitating matching protection with upstream circuit breakers and improving the stability and reliability of power supply. This invention possesses significant advantages such as fast short-circuit protection breaking speed, high reliability, strong current limiting capability, and long breaking life, making it suitable for applications requiring rapid breaking protection, such as busbar connections in DC power systems.

[0035] In some embodiments of the present invention, the main switch branch includes a fast mechanical switch.

[0036] In some embodiments of the present invention, the load switch is a two-pole air switch.

[0037] The load switch S2 is a double-pole air switch, and the main switch branch consists of a fast mechanical switch S1, which is based on the principle of electromagnetic repulsion.

[0038] The fast mechanical switch S1 is connected to one pole of the load switch S2.

[0039] The integrated control unit receives switch status signals and performs opening / closing operations according to system protection requirements. The status signals include the opening / closing status of fast mechanical switch S1 and load switch S2, the current value and current change rate value of the current detection unit.

[0040] In some embodiments of the present invention, the voltage limiting and energy dissipation branch includes a varistor MOV.

[0041] The voltage-limiting and energy-consuming branch is composed of a varistor MOV.

[0042] In some embodiments of the present invention, the current detection unit includes a current change rate sensor and a Hall current sensor.

[0043] The current detection unit includes a current sensor and a current change rate sensor, which constantly monitor the changes in system current and transmit the collected data to the integrated control unit.

[0044] The present invention also provides a control method for a DC combination switch, applied to the DC combination switch described in any of the above embodiments, comprising: When the power system is under short-circuit protection, the integrated control unit detects that the current value or current change rate has reached the protection setting value. Based on the current direction, it controls the fast disconnection unit to cut off the system current and controls the load switch to disconnect, forming a mechanical break.

[0045] In short-circuit protection conditions, current setting value protection and d are adopted. i / d t The settings are used together for protection. When any setting reaches the protection setting value, the integrated control unit controls the fast disconnection unit to quickly cut off the system current.

[0046] Then, a disconnection command is sent to load switch S2 to open it in a zero-current state, forming a mechanical break.

[0047] The control method for DC combined switches provided in this invention can achieve current interruption under different operating conditions by controlling different components. It fully integrates the advantages of load switches (long breaking life under low current) and hybrid circuit breakers (fast breaking speed, high breaking capacity, strong current limiting capability, and long life under high current), resulting in extremely low conduction losses under rated current conditions. Under short-circuit conditions, it exhibits fast breaking speed and high current limiting level, facilitating matching protection with upstream circuit breakers and improving the stability and reliability of power supply. This invention possesses significant advantages such as fast short-circuit protection breaking speed, high reliability, strong current limiting capability, and long breaking life, making it suitable for applications requiring rapid breaking protection, such as busbar connections in DC power systems.

[0048] In some embodiments of the present invention, the step of controlling the rapid disconnection unit to turn off the system current according to the current direction and controlling the load switch to disconnect, forming a mechanical break, includes: When the current flows from the main switch branch to the load switch, the integrated control unit sends a trip command to the main switch branch and a conduction command to the first thyristor, so that the fault current is transferred from the main switch branch to the first thyristor of the current transfer branch. After the current transfer is completed, the integrated control unit sends a turn-on command to the fourth and fifth thyristors to enable the fault current to be applied to the forced commutation branch. When the current in the first thyristor crosses zero and is turned off under the action of a negative voltage, the capacitor is charged. When the voltage across the capacitor rises to the voltage across the varistor, the varistor turns on, causing the current to transfer to the voltage-limiting and energy-dissipating branch and then drop to zero.

[0049] If the current flows from the fast mechanical switch S1 to the load switch S2.

[0050] When the integrated control unit detects that the current signal (including the current value and the rate of change of current) transmitted by the current detection unit has reached the set value, the integrated control unit first sends the fast mechanical switch S1 trip command and the thyristor T1 turn-on command simultaneously.

[0051] The fault current is transferred from the fast mechanical switch S1 in the main switch branch to the thyristor T1 in the current transfer branch.

[0052] After the current transfer is completed, the thyristor T4 and T5 are turned on, and the forced commutation branch is activated.

[0053] The current in thyristor T1 crosses zero and is turned off under the action of a negative voltage.

[0054] Subsequently, the system charges capacitor C, causing the voltage to rise. When the voltage reaches the varistor's turn-on voltage, the varistor turns on. The current is then transferred to the voltage-limiting and energy-dissipating branch and quickly drops to zero.

[0055] In some embodiments of the present invention, the step of controlling the rapid disconnection unit to turn off the system current according to the current direction and controlling the load switch to disconnect, forming a mechanical break, includes: When the current flows from the load switch to the main switch branch, the integrated control unit sends a trip command to the main switch branch and a conduction command to the second thyristor, so that the fault current is transferred from the main switch branch to the second thyristor of the current transfer branch. After the current transfer is completed, the integrated control unit sends a turn-on command to the third and sixth thyristors to enable the fault current to be applied to the forced commutation branch. When the current in the second thyristor crosses zero and is turned off under the action of a negative voltage, the capacitor is charged. When the voltage across the capacitor rises to the voltage across the varistor, the varistor turns on, causing the current to transfer to the voltage-limiting and energy-dissipating branch and then drop to zero.

[0056] If the current flows from the fast mechanical switch S2 to the load switch S1.

[0057] When the integrated control unit detects that the current signal (including the current value and the rate of change of current) transmitted by the current detection unit has reached the set value, the integrated control unit first sends the fast mechanical switch S1 trip command and the thyristor T2 turn-on command simultaneously.

[0058] The fault current is transferred from the fast mechanical switch S1 in the main switch branch to the thyristor T2 in the current transfer branch.

[0059] After the current transfer is completed, the thyristor T3 and T6 are turned on, and the forced commutation branch is activated.

[0060] The current in thyristor T2 crosses zero and is turned off under the action of a negative voltage.

[0061] Subsequently, the system charges capacitor C, causing the voltage to rise. When the voltage reaches the varistor's turn-on voltage, the varistor turns on. The current is then transferred to the voltage-limiting and energy-dissipating branch and quickly drops to zero.

[0062] The control method for DC combined switch provided in this embodiment of the invention can quickly disconnect two parallel-running buses during short-circuit breaking and limit the peak value of the system fault current, thereby achieving matching protection with the upstream circuit breaker.

[0063] In some embodiments of the present invention, it further includes: When the integrated control unit receives the closing command from the power system, it controls the main switch branch to close, and after a preset time, controls the load switch to close. When the power system is operating at or below its rated value, the main switch branch and load switch are used to carry the system current. When a disconnection operation is required, the integrated control unit sends a disconnection command to the load switch to cut off the main circuit current and form a mechanical break.

[0064] After receiving the closing command from the system, the integrated control unit first closes the fast mechanical switch S1. After a delay of about 0.1 seconds, once the fast mechanical switch S1 has closed and the locking mechanism has reset and is ready to open, the load switch S2 is then closed, and the main circuit is connected.

[0065] In operating conditions at or below the rated value, the system current is carried by the fast mechanical switch S1 and the load switch S2.

[0066] When a disconnection operation is required, the integrated control unit sends a disconnection command to the load switch S2 to cut off the main circuit current and form a mechanical break.

[0067] In some embodiments of the present invention, it further includes: When the power system is under overload conditions, the integrated control unit sends a disconnection command to the load switch to complete the overload protection and form a mechanical disconnection.

[0068] After an overload occurs and the system protection requirements are met, the integrated control unit sends a load switch S2 disconnection command to complete the overload protection and form a mechanical break.

[0069] For example, Figure 2 This is a schematic diagram of the current waveform of the circuit breaker during rated and overload operation, provided by the present invention, in conjunction with... Figure 2 The present invention provides a method for breaking a fast DC combined switch under rated and overload conditions, comprising the following steps: t At moment 1, upon receiving the system operation command, the integrated control unit first closes the fast mechanical switch S1, and after a delay of a period of time (approximately 0.1s), closes the load switch S2, thus connecting the main circuit.

[0070] If a current overload is detected in the system, or if the upstream system requires the circuit current to be cut off,t At time 2, the system integrated control unit issues a command to open the load switch S2.

[0071] After a period of inherent delay, t At time 3, the load switch S2 actually tripped, and the circuit current decreased.

[0072] t At time 4, the loop current drops to zero, completing the disconnection.

[0073] Figure 3 This is a schematic diagram of the current waveform of the circuit breaker during short-circuit protection provided by the present invention, combined with... Figure 3 The fast DC combined switch short-circuit breaking method provided by the present invention includes the following steps: t At time 0, upon receiving the system operation command, the integrated control unit first closes the fast mechanical switch S1, and after a delay of about 0.1 seconds, closes the load switch S2, thus connecting the main circuit.

[0074] t 0~ t In Phase 1, the system operates normally, with the main switch branch's fast mechanical switch S1 and load switch S2 closed, carrying the system current. i 0.

[0075] t At time 1, a short circuit fault occurs in the system, and the current value is... i and the rate of change of current d i / d t Both increase, and when either of the above two detection quantities reaches the system setting value, the integrated control unit controls the rapid disconnection unit to quickly shut off the system current.

[0076] (1) If the current flows from the fast mechanical switch S1 to the load switch S2.

[0077] t When the integrated control unit detects a short circuit fault at time 2, it first sends a fast mechanical switch S1 trip command and a thyristor T1 turn-on command simultaneously.

[0078] t At time 3, after a period of inherent time delay, the fast mechanical switch S1 begins to actually open and generates an arc voltage. Under the action of the arc voltage, the fault current is transferred from the fast mechanical switch S1 in the main switch branch to the thyristor T1 in the current transfer branch.

[0079] t 4. The current is completely transferred to the thyristor T1.

[0080] tAt time 5, the fast mechanical switch S1 restores its dielectric blocking characteristic, and the integrated control unit sends turn-on commands to thyristors T4 and T5, activating the forced commutation branch. The current in thyristor T1 crosses zero and is turned off under the action of a negative voltage.

[0081] t At time 6, the system charges capacitor C, and the voltage of capacitor C increases.

[0082] t At time 7, when the capacitor voltage rises to the varistor's turn-on voltage, the varistor turns on.

[0083] t At time 8, the current is transferred to the voltage-limiting energy-dissipating branch and quickly drops to zero.

[0084] t At 9 o'clock, the integrated control unit sends a command to open the load switch S2. The load switch S2 opens after the system current crosses zero, achieving arc-free disconnection and forming a physical break point.

[0085] (2) If the current flows from the load switch S2 to the fast mechanical switch S1.

[0086] t When the integrated control unit detects a short circuit fault at time 2, it first sends a fast mechanical switch S1 trip command and a thyristor T2 turn-on command simultaneously.

[0087] t At time 3, after a period of inherent time delay, the fast mechanical switch S1 begins to actually open and generates an arc voltage. Under the action of the arc voltage, the fault current is transferred from the fast mechanical switch S1 in the main switch branch to the thyristor T2 in the current transfer branch.

[0088] t 4. The current is completely transferred to the thyristor T2.

[0089] t At time 5, the fast mechanical switch S1 restores its dielectric blocking characteristic, and the integrated control unit sends turn-on commands to thyristors T3 and T6, activating the forced commutation branch. The current in thyristor T2 crosses zero and is turned off under the action of a negative voltage.

[0090] t At time 6, the system charges capacitor C, and the voltage of capacitor C increases.

[0091] t At time 7, when the capacitor voltage rises to the varistor's turn-on voltage, the varistor turns on.

[0092] t At time 8, the current is transferred to the voltage-limiting energy-dissipating branch and quickly drops to zero.

[0093] t At 9 o'clock, the integrated control unit sends a command to open the load switch S2. The load switch S2 opens after the system current crosses zero, achieving arc-free disconnection and forming a physical break point.

[0094] This invention proposes a fast DC combined switch that achieves current breaking under different operating conditions by controlling different components. It fully integrates the advantages of load switches (long breaking life under low current) and hybrid circuit breakers (fast breaking speed, high breaking capacity, strong current limiting capability, and long life). It exhibits extremely low conduction losses under rated current conditions. Under short-circuit conditions, it offers fast breaking speed, high current limiting level, and easy matching protection with upstream circuit breakers, thereby improving the stability and reliability of the power supply system.

[0095] This invention has significant advantages such as fast short-circuit protection breaking speed, high reliability, strong current limiting capability, and long breaking life. It is suitable for occasions requiring rapid breaking protection, such as bus connection points in DC power systems.

[0096] Those skilled in the art will understand that all or part of the processes of the methods described in the above embodiments can be implemented by a computer program instructing related hardware (such as a processor, controller, etc.), and the computer program can be stored in a computer-readable storage medium. The computer-readable storage medium may be a disk, optical disk, read-only memory, or random access memory, etc.

[0097] The above provides a detailed description of the DC combination switch and its control method provided by the present invention. Specific examples have been used to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. At the same time, those skilled in the art will recognize that there will be changes in the specific implementation methods and application scope based on the ideas of the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A direct current combination switch, characterized in that, include: Integrated control unit, current detection unit, fast disconnection unit, and load switch; The integrated control unit, the current detection unit, the fast disconnection unit, and the load switch are connected in sequence; The rapid disconnection unit includes a voltage limiting and energy dissipation branch, a current transfer branch, a main switch branch, and a forced commutation branch connected in parallel. The current transfer branch includes: a first thyristor and a second thyristor connected in reverse parallel. The forced commutation branch includes: an inductor, a capacitor, a third thyristor, a fourth thyristor, a fifth thyristor, and a sixth thyristor; The inductor and the capacitor are connected in series to form the first branch; The anodes of the third thyristor and the fourth thyristor are connected to form a second branch; The cathodes of the fifth thyristor and the sixth thyristor are connected to form a third branch; The second branch and the third branch are connected in parallel; The connection nodes of the third thyristor and the fourth thyristor, and the connection nodes of the fifth thyristor and the sixth thyristor are respectively connected to the two ends of the first branch. The first end of the main switch branch is connected to the current detection unit, and the second end of the main switch branch is connected to the load switch; The current detection unit is used to collect the current value and current change rate of the power system; The integrated control unit is used to control the opening and closing states of the load switch and the main switch branch based on the current value and the current change rate. The load switch is a double-pole air switch; When the integrated control unit receives the closing command from the power system, it controls the main switch branch to close, and after a preset time, controls the load switch to close. When the power system is operating at or below its rated value, the main switch branch and load switch are used to carry the system current. When a disconnection operation is required, the integrated control unit sends a disconnection command to the load switch to cut off the main circuit current and form a mechanical break. When the power system is under overload conditions, the integrated control unit sends a disconnection command to the load switch to complete the overload protection and form a mechanical disconnection.

2. The DC combination switch of claim 1, wherein The main switch branch includes a fast mechanical switch.

3. The DC combination switch of claim 1, wherein, The voltage-limiting and energy-dissipating branch includes a varistor.

4. The DC combination switch of claim 1, wherein, The current detection unit includes a current change rate sensor and a Hall current sensor.

5. A control method for a DC combined switch, characterized in that, The DC combination switch applied to any one of claims 1 to 4 comprises: When the power system is in short-circuit protection mode, when the integrated control unit detects that the current value or current change rate has reached the protection setting value, it controls the fast disconnection unit to cut off the system current according to the current direction and controls the load switch to disconnect, forming a mechanical break. Also includes: When the integrated control unit receives the closing command from the power system, it controls the main switch branch to close, and after a preset time, controls the load switch to close. When the power system is operating at or below its rated value, the main switch branch and load switch are used to carry the system current. When a disconnection operation is required, the integrated control unit sends a disconnection command to the load switch to cut off the main circuit current and form a mechanical break. When the power system is under overload conditions, the integrated control unit sends a disconnection command to the load switch to complete the overload protection and form a mechanical disconnection.

6. The control method for a DC combined switch according to claim 5, characterized in that, The method of controlling the rapid disconnection unit to cut off the system current according to the current direction and controlling the load switch to disconnect, forming a mechanical break, includes: When the current flows from the main switch branch to the load switch, the integrated control unit sends a trip command to the main switch branch and a conduction command to the first thyristor, so that the fault current is transferred from the main switch branch to the first thyristor of the current transfer branch. After the current transfer is completed, the integrated control unit sends a turn-on command to the fourth and fifth thyristors to enable the fault current to be applied to the forced commutation branch. When the current in the first thyristor crosses zero and is turned off under the action of a negative voltage, the capacitor is charged. When the voltage across the capacitor rises to the voltage across the varistor, the varistor turns on, causing the current to transfer to the voltage-limiting and energy-dissipating branch and then drop to zero.

7. The control method for a DC combined switch according to claim 5, characterized in that, The method of controlling the rapid disconnection unit to cut off the system current according to the current direction and controlling the load switch to disconnect, forming a mechanical break, includes: When the current flows from the load switch to the main switch branch, the integrated control unit sends a trip command to the main switch branch and a conduction command to the second thyristor, so that the fault current is transferred from the main switch branch to the second thyristor of the current transfer branch. After the current transfer is completed, the integrated control unit sends a turn-on command to the third and sixth thyristors to enable the fault current to be applied to the forced commutation branch. When the current in the second thyristor crosses zero and is turned off under the action of a negative voltage, the capacitor is charged. When the voltage across the capacitor rises to the voltage across the varistor, the varistor turns on, causing the current to transfer to the voltage-limiting and energy-dissipating branch and then drop to zero.

Images