Capacitor voltage clamping type direct-current circuit breaker with energy consumption function and control method of capacitor voltage clamping type direct-current circuit breaker

Abstract

The invention discloses a capacitor voltage clamping type direct-current circuit breaker with an energy consumption function and a control method thereof, the direct-current circuit breaker is connected between direct-current polar lines of a flexible direct-current sending-out system, and the direct-current circuit breaker comprises a conduction branch which comprises a first switch and a first thyristor which are connected in series; the variable clamp voltage module and the energy consumption module which are connected in series are jointly used for controlling energy consumption power according to energy consumption requirements and controlling the variable clamp voltage to enable the first switch to be switched off to clear a fault after the current of the conduction branch passes zero when the fault occurs; and the auxiliary branch comprises a second switch, is connected between the direct-current polar lines and is used for assisting each module in resetting after the fault is cleared. The control method comprises a pre-charging stage, an energy consumption control mode and a direct current open circuit mode. According to the invention, through common utilization of devices, reliable breaking of the mechanical switch can be realized, and fault current can be effectively limited.

Description

Technical Field

[0001] This invention relates to the field of DC transmission protection technology, and in particular to a capacitor voltage clamping DC circuit breaker with energy dissipation function and its control method. Background Technology

[0002] When a DC power grid fault occurs, the instantaneous drop in potential at the fault point creates a large instantaneous positive voltage difference between the line bus and the fault point, causing a sharp increase in line current. Furthermore, the absence of a natural zero-crossing point poses a significant challenge to the interruption of DC circuit breakers. Achieving mechanical switching at low line currents or zero-crossing points is crucial in DC circuit breaker design. Capacitor-clamped DC circuit breakers utilize pre-charged clamping capacitors to raise the fault point voltage during a fault, thereby forcing the line current to rapidly drop to zero, achieving fast and reliable current interruption.

[0003] However, the clamping voltage level of existing capacitor voltage clamping DC circuit breakers is fixed and cannot be dynamically adjusted. Furthermore, the circuit breaker's breaking function and energy consumption function are separated, requiring an additional independent energy consumption device in parallel. This results in large equipment size, high cost, complex installation, and a lack of precise energy consumption control, leading to poor current limiting performance. Summary of the Invention

[0004] To address the above technical problems, this invention provides a capacitor voltage clamping DC circuit breaker with energy dissipation function and its control method. By utilizing the components together, it can achieve reliable disconnection of the mechanical switch and effectively limit the fault current.

[0005] This invention provides a capacitor voltage clamping DC circuit breaker with energy dissipation function. The capacitor voltage clamping DC circuit breaker is connected between the DC poles of a flexible DC transmission system and includes: The conducting branch includes a first switch and a first thyristor connected in series; The series-connected variable clamping voltage module and at least one energy-consuming module are used together to control the energy consumption power according to the energy consumption demand, and to control the variable clamping voltage to make the current of the conducting branch cross zero in the event of a fault, and then disconnect the first switch to clear the fault. An auxiliary branch, including a second switch, is connected between the DC poles to assist in resetting each module after the fault is cleared.

[0006] Furthermore, the variable clamping voltage module includes: a current-limiting inductor, a fourth thyristor, a first resistor, a main clamping capacitor, and a second and third thyristors connected in reverse parallel. Wherein, one end of the current-limiting inductor is connected to the anode of the second thyristor, the cathode of the third thyristor, the anode of the fourth thyristor, and the first end of the first resistor; the first end of the main clamping capacitor is connected to the cathode of the second thyristor and the anode of the third thyristor; and the second end of the main clamping capacitor is connected to the cathode of the fourth thyristor and the second end of the first resistor.

[0007] Furthermore, the energy-consuming module includes: an energy-consuming module capacitor, a second resistor, a first power switch with a reverse parallel diode, a second power switch with a reverse parallel diode, and a fifth and a sixth thyristor connected in reverse parallel. In this configuration, both the first power switch and the second power switch are insulated-gate bipolar transistors (IGBTs). The collector of the first power switch is connected to the anode of the fifth thyristor and the cathode of the sixth thyristor. The collector of the second power switch is connected to the first terminal of the energy-consuming module capacitor, the cathode of the fifth thyristor, and the anode of the sixth thyristor. The emitter of the second power switch is connected to the first terminal of the second resistor. The emitter of the first power switch is connected to the second terminal of the energy-consuming module capacitor and the second terminal of the second resistor.

[0008] Furthermore, the operating modes of the capacitor voltage clamping DC circuit breaker include an energy consumption control mode; The energy consumption control mode adjusts the voltage of the energy consumption module capacitor by controlling the on / off state of the fifth thyristor, the first power switch, and the second power switch, thereby adjusting the voltage of the first resistor to control energy consumption power; wherein, the first resistor is used for centralized energy consumption.

[0009] Furthermore, the operating mode of the capacitor voltage clamping DC circuit breaker includes a DC circuit breaking mode; In the DC circuit breaking mode, by controlling the switching on and off of each thyristor in the variable clamping voltage module and the energy consumption module, the main clamping capacitor and the energy consumption module capacitor are connected in series to raise the voltage at the fault point. After the current in the conducting branch crosses zero, the first switch is disconnected to clear the fault. After clearing the fault, the first switch is reset by controlling the auxiliary branch, and the energy of the main clamping capacitor and the energy consumption module capacitor is dissipated by turning on the second thyristor and the second power switch.

[0010] The present invention also provides a control method for a capacitor voltage clamping DC circuit breaker with energy dissipation function, applied to the aforementioned capacitor voltage clamping DC circuit breaker with energy dissipation function, the control method comprising: When the capacitor voltage clamping DC circuit breaker is first put into operation, it enters the pre-charging stage to charge the main clamping capacitor and the energy dissipation module capacitor. When an energy consumption demand command is received, the system enters the energy consumption control mode to control the energy consumption power according to the energy consumption demand. When a command to disconnect a line fault is received, the system enters DC circuit breaking mode. After raising the voltage at the fault point to make the current in the conducting branch cross zero, the first switch is disconnected to clear the fault.

[0011] As an improvement to the above solution, the pre-charging stage specifically includes: First pre-charging stage: The conducting branch, the second thyristor, and the first power switch are turned on to charge the main clamping capacitor; when the main clamping capacitor is charged to the system voltage, the current in the branch where the main clamping capacitor is located crosses zero, the second thyristor turns off automatically, and the stage ends. Second pre-charging stage: The conducting branch, the fourth thyristor, and the fifth thyristor are turned on to charge the energy-consuming module capacitor; when the energy-consuming module capacitor is charged to the system voltage, the current in the branch where the energy-consuming module capacitor is located crosses zero, and the fourth thyristor and the fifth thyristor turn off automatically, and the stage ends.

[0012] As an improvement to the above solution, the step of controlling energy consumption based on energy demand includes: The conduction branch is turned on, and the second thyristor, third thyristor, and fourth thyristor in the variable clamping voltage module are turned off; Based on the energy consumption demand, the number of energy consumption modules in operation is adjusted by controlling the on / off state of the fifth thyristor in each energy consumption module, and the voltage of the energy consumption module capacitor in the corresponding energy consumption module is adjusted by the second power switch in the energy consumption module, thereby adjusting the voltage of the first resistor and realizing energy consumption power control.

[0013] As an improvement to the above scheme, in the DC circuit breaker mode, the control method includes: During fault detection, the conduction branch is activated, and the variable clamping voltage module and the energy consumption module are disconnected. Upon receiving a trip command, the third thyristor in the variable clamp voltage module and the sixth thyristor in each of the energy-consuming modules are turned on, so that the main clamp capacitor and the energy-consuming module capacitor are connected in series to raise the voltage until the current in the conducting branch is zero, and the first switch is turned off to clear the fault.

[0014] As an improvement to the above solution, in the DC circuit breaker mode, the control method further includes: After clearing the fault, close the second switch to make the auxiliary branch conduct, so as to form a resonant circuit; When the current in the resonant circuit crosses zero, the third thyristor and the sixth thyristor turn off automatically. After the third thyristor and the sixth thyristor are turned off, the first switch and the second switch are reset to disconnect the auxiliary branch and connect the conducting branch. The second thyristor and the second power switch are turned on, so that the main clamping capacitor dissipates energy through the circuit formed with the first resistor, and the energy dissipation module capacitor dissipates energy through the circuit formed with the second resistor.

[0015] Compared with the prior art, the beneficial effects of the capacitor voltage clamping DC circuit breaker with energy dissipation function and its control method provided by the present invention are as follows: By constructing a conducting branch, an auxiliary branch, a series-connected variable clamping voltage module, and several energy-consuming modules, the conducting branch includes a first switch and a first thyristor connected in series. The series-connected variable clamping voltage module and energy-consuming modules are used together to control the energy consumption power according to the energy consumption demand, and to control the variable clamping voltage to disconnect the first switch after the current of the conducting branch crosses zero in case of a fault, thereby clearing the fault. This achieves the functional reuse of DC circuit breaker and energy-consuming functions, reduces cost and size, and reduces the number of fully controlled devices by using semi-controlled devices such as thyristors. Furthermore, it reduces the requirements for mechanical switches during the circuit breaking process, achieving lower cost and better performance. By controlling the variable clamping voltage, the line current is forced to drop to zero during a fault, thereby achieving rapid fault clearing. The circuit breaker does not exacerbate the rise in line current during fault clearing, and has good current limiting capability. The selective activation of the pre-charge capacitor during a fault can achieve reliable disconnection of the mechanical switch, and also achieve energy dissipation function by controlling the activation of the energy dissipation module through the design of the switch state, effectively limiting the fault current. It can achieve functional reuse by controlling the opening and closing of the switching device without changing the topology, saving costs, and is highly practical. It is suitable for protection in large-scale long-distance transmission systems. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the circuit structure of a capacitor voltage clamping DC circuit breaker with energy dissipation function provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of the circuit structure of a capacitor voltage clamping DC circuit breaker with energy dissipation function in the first pre-charging stage, provided by an embodiment of the present invention. Figure 3 This is a schematic diagram of the circuit structure of a capacitor voltage clamping DC circuit breaker with energy dissipation function in the second pre-charging stage, provided by an embodiment of the present invention. Figure 4This is a schematic diagram of the circuit structure of a capacitor voltage clamping DC circuit breaker with energy dissipation function in energy dissipation control mode according to an embodiment of the present invention. Figure 5 This is a schematic diagram of the circuit structure of a capacitor voltage clamping DC circuit breaker with energy dissipation function under full energy dissipation load, provided by an embodiment of the present invention. Figure 6 This is a schematic diagram of the circuit structure of a capacitor voltage clamping DC circuit breaker with energy dissipation function during fault clearing, provided by an embodiment of the present invention. Figure 7 This is a schematic diagram of the circuit structure of a capacitor voltage clamping DC circuit breaker with energy dissipation function in the first reset stage, provided by an embodiment of the present invention. Figure 8 This is a schematic diagram of the circuit structure of a capacitor voltage clamping DC circuit breaker with energy dissipation function in the second reset stage, provided by an embodiment of the present invention. The accompanying diagrams are labeled as follows: S1, First switch; S2, Second switch; T1, First thyristor; T2, Second thyristor; T3, Third thyristor; T4, Fourth thyristor; T5, Fifth thyristor; T6, Sixth thyristor; Q1, First power switch; Q2, Second power switch; L dc Busbar current-limiting inductor; L m Current-limiting inductor; R d First resistor; r; Second resistor; C d Main clamping capacitor; C sm Energy-consuming module capacitor; SM, energy-consuming module. Detailed Implementation

[0017] 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 some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] Please see Figure 1 , Figure 1 This is a schematic diagram of the circuit structure of a capacitor voltage clamping DC circuit breaker with energy dissipation function provided in an embodiment of the present invention. The capacitor voltage clamping DC circuit breaker with energy dissipation function is connected between the DC poles of an offshore wind power flexible DC transmission system. The capacitor voltage clamping DC circuit breaker includes: The conducting branch includes a first switch S1 and a first thyristor T1 connected in series; The series-connected variable clamping voltage module and at least one energy-consuming module are used together to control the energy consumption power according to the energy consumption demand, and to control the variable clamping voltage to make the current of the conducting branch cross zero in the event of a fault, and then disconnect the first switch S1 to clear the fault. An auxiliary branch, including a second switch S2, is connected between the DC poles to assist in resetting each module after the fault is cleared.

[0019] Specifically, the capacitor voltage clamping DC circuit breaker includes a conducting branch, an auxiliary branch, a series-connected variable clamping voltage module, and several energy dissipation modules. The conducting branch controls the on / off state of the DC bus, and consists of a first switch S1, a first thyristor T1, and a bus current-limiting inductor L connected in series. dc The first switch S1 is configured such that one end is connected to the anode of the first thyristor T1, and the cathode of the first thyristor T1 is connected to the bus current-limiting inductor L. dc One end is connected. The conducting branch serves as the main conduction path, carrying DC current during normal operation; in fault detection and circuit breaking, it serves as the criterion path for determining whether the current has crossed zero, working in conjunction with the first switch to clear the fault.

[0020] In the auxiliary branch, the second switch S2 is connected between the positive and negative lines. During normal operation of the DC circuit breaker, the second switch S2 is in the open state. After the fault is cleared, the controllable device self-turn-off and energy transfer are achieved through the conduction and resonance of the auxiliary branch, which facilitates the subsequent dissipation of energy in each circuit along a predetermined path, thus achieving rapid reset.

[0021] Both the first switch S1 and the second switch S2 are fast mechanical switches.

[0022] The input terminal of the variable clamping voltage module is connected to the first thyristor T1 and the bus current-limiting inductor L. dc Between, the current-limiting inductor L in the variable clamping voltage module m The first end is connected to the cathode of the first thyristor T1; the output end of the variable clamping voltage module is connected to the input end of the energy dissipation module. When multiple energy dissipation modules are installed in the capacitor voltage clamping DC circuit breaker, the energy dissipation modules are connected in series. If the energy dissipation module connected to the variable clamping voltage module is taken as the first energy dissipation module, then the output end of the last energy dissipation module is connected to the negative line.

[0023] As one optional embodiment, the variable clamping voltage module includes: a current-limiting inductor L m Fourth thyristor T4, first resistor R d Main clamping capacitor C d The second thyristor T2 and the third thyristor T3 are connected in reverse parallel. Wherein, the current-limiting inductor L mOne end of the first resistor is connected to the anode of the second thyristor T2, the cathode of the third thyristor T3, the anode of the fourth thyristor T4, and the first resistor R. d The first end is connected; the main clamping capacitor C d The first end is connected to the cathode of the second thyristor T2 and the anode of the third thyristor T3; the main clamping capacitor C d The second end is connected to the cathode of the fourth thyristor T4 and the first resistor R. d The second end is connected.

[0024] Specifically, the variable clamping voltage module can achieve variable clamping voltage and centralized power consumption, including a centralized power consumption resistor branch, a clamping capacitor branch, and a current-limiting inductor L. m The centralized energy-dissipating resistor branch is connected in parallel with the clamping capacitor branch, and the current-limiting inductor L... m It is connected in series with two branches; the energy-dissipating resistor branch is connected to the first resistor R. d It is connected in parallel with the fourth thyristor T4, and the anode of the fourth thyristor T4 is connected to the current-limiting inductor L. m Connected; the clamping capacitor branch is connected to the first thyristor valve and the main clamping capacitor C. d The first thyristor valve is formed by connecting a second thyristor T2 and a third thyristor T3 in reverse parallel, wherein the anode of the second thyristor T2, the cathode of the third thyristor T3, and the current-limiting inductor L are connected in series. m Connected, main clamping capacitor C d One end is connected to the first thyristor valve, and the other end is connected to the output terminal of the variable clamping voltage module.

[0025] The variable clamping voltage module is used in DC circuit breaking operations to raise the voltage at the fault point by working with the energy dissipation module to connect the main clamping capacitor and the energy dissipation module capacitor in series, thereby causing the current in the conducting branch to cross zero. In addition, the module also provides current limiting, clamping and switching control capabilities to ensure the controllability and safety of the voltage raising process.

[0026] As one optional embodiment, the energy-consuming module includes: an energy-consuming module capacitor C. sm The second resistor r, the first power switch Q1 with a reverse parallel diode, the second power switch Q2 with a reverse parallel diode, and the fifth thyristor T5 and the sixth thyristor T6 connected in reverse parallel. Wherein, both the first power switch Q1 and the second power switch Q2 are insulated-gate bipolar transistors (IGBTs); the collector of the first power switch Q1 is connected to the anode of the fifth thyristor T5 and the cathode of the sixth thyristor T6; the collector of the second power switch Q2 is connected to the energy-consuming module capacitor C. smThe first terminal of the first power switch Q1 is connected to the cathode of the fifth thyristor T5 and the anode of the sixth thyristor T6; the emitter of the second power switch Q2 is connected to the first terminal of the second resistor r; the emitter of the first power switch Q1 is connected to the capacitor C of the energy-consuming module. sm The second end of the resistor is connected to the second end of the second resistor r.

[0027] Specifically, the power consumption module internally utilizes thyristors and power switches in tandem to achieve precise control over the voltage across the first resistor and the power consumption. Each power consumption module consists of a power consumption module capacitor C. sm The circuit consists of a second resistor r, a first power switch Q1 with a reverse-parallel diode, a second power switch Q2 with a reverse-parallel diode, and a fifth thyristor T5 and a sixth thyristor T6 connected in reverse parallel. The fifth thyristor T5 and the sixth thyristor T6 are connected in reverse parallel to form a second transistor valve. The anode of the fifth thyristor T5 is connected to the input terminal of the power consumption module, and the cathode of the sixth thyristor T6 is connected to the input terminal of the power consumption module. The collector of the first power switch Q1 is connected to the input terminal of the power consumption module, and the emitter of the first power switch Q1 is connected to the output terminal of the power consumption module. The branch formed by the second power switch Q2 and the second resistor r connected in series is connected to the capacitor C of the power consumption module. sm Parallel connection, energy-consuming module capacitor C sm Capacitor C, used to support module voltage and consume power in the module. sm One end is connected to the second transistor valve and the second power switch Q2, and the other end is connected to the first power switch Q1, the output terminal of the energy consumption module, and the second resistor r. When the first power switch Q1 is turned on, the corresponding energy consumption module is switched off. When the first power switch Q1 is turned off and the second transistor valve is turned on, the energy consumption module is put into use.

[0028] Furthermore, when a capacitor voltage clamping DC circuit breaker is initially put into operation, the main clamping capacitor C needs to be checked. d With energy-consuming module capacitor C sm Perform pre-charging.

[0029] Please see Figure 2 When the DC line is normally energized, the conducting branch is conducting, and the current-limiting inductor L... m First thyristor valve (specifically, it connects the second thyristor T2), main clamping capacitor C d The first power switch Q1 is turned on in series, forming the first charging branch. At this time, the main clamping capacitor C d Charging begins. When the current in the first charging branch crosses zero, the first thyristor valve naturally closes, at which point the main clamping capacitor C... d Charging complete.

[0030] Please see Figure 3When the DC line is normally energized, the conducting branch is conducting, and thyristor T4, the second thyristor valve (specifically, the fifth thyristor T5) and the energy-consuming module capacitor C are connected. sm When the series circuit is activated, a second charging branch is formed, and at this time the energy-consuming module capacitor C... sm Charging begins. When the current in the second charging branch crosses zero, the second thyristor valve naturally shuts off, at which point the energy-consuming module capacitor C... sm Charging complete.

[0031] As one optional embodiment, the operating mode of the capacitor voltage clamping DC circuit breaker includes an energy consumption control mode; in the energy consumption control mode, the capacitor C of the energy consumption module is adjusted by controlling the switching of the fifth thyristor T5, the first power switch Q1, and the second power switch Q2. sm The voltage is adjusted to regulate the voltage of the first resistor R. d The voltage is used for power consumption control; wherein, the first resistor R d Used for centralized energy consumption.

[0032] Specifically, when a fault occurs requiring the activation of energy-consuming devices, the capacitor voltage clamping DC circuit breaker operates in energy-consuming control mode. Please refer to [link to relevant documentation]. Figure 4 In energy consumption control mode, the current-limiting inductor L m First resistor R d Fifth thyristor T5, energy-consuming module capacitor C sm The second power switch Q2 is connected to the second resistor r. By turning the second power switch Q2 on and off, the energy-consuming module capacitor C is adjusted. sm The voltage magnitude is used to adjust the first resistor R used for centralized energy dissipation. d The voltage level controls the power consumption of the capacitor voltage clamped DC circuit breaker. Specifically, the number of power consumption modules is selected based on energy demand, and unnecessary modules are switched off by turning on the first power switch Q1. When the power consumption is at its maximum, the power consumption is at full load, such as... Figure 5 As shown, the main clamping capacitor C d And all power-consuming module capacitors C sm Bypassing the circuit makes the voltage across the energy-consuming resistor equal to the line voltage, at which point the resistor's energy consumption is at its maximum.

[0033] As one optional embodiment, the operating mode of the capacitor voltage clamping DC circuit breaker includes a DC circuit breaking mode; in the DC circuit breaking mode, the main clamping capacitor C is controlled by switching the variable clamping voltage module and the thyristors in the energy dissipation module on and off. d With the energy-consuming module capacitor C smThe circuit is connected in series to raise the voltage at the fault point, and after the current in the conducting branch crosses zero, the first switch S1 is disconnected to clear the fault; after clearing the fault, the first switch S1 is reset by controlling the auxiliary branch, and the second thyristor T2 and the second power switch Q2 are turned on to activate the main clamping capacitor C. d With the energy-consuming module capacitor C sm Energy dissipation.

[0034] Specifically, when a fault occurs requiring the disconnection of the line, the capacitor voltage clamping DC circuit breaker operates in DC interruption mode. For example... Figure 6 As shown, when the capacitor voltage clamped DC circuit breaker receives a trip command, the current limiting inductor L... m Third thyristor T3, main clamping capacitor C d Sixth thyristor T6, energy-consuming module capacitor C sm The circuit is on. At this time, the main clamping capacitor C is turned on. d With energy-consuming module capacitor C sm In series, the voltage at point n rises, and the voltage across the first switch S1 of the conducting branch gradually rises to the same voltage. When the fault current of the conducting branch crosses zero, the first switch S1 and the first thyristor T1 of the conducting branch are disconnected, and the fault is cleared.

[0035] like Figure 7 As shown, after the fault is cleared, the second switch S2 of the auxiliary branch is turned on, at which time the main clamping capacitor C... d Energy-consuming module capacitor C sm Bus current limiting inductor L dc Current-limiting inductor L m This forms a resonant circuit. When the resonant current crosses zero, the first thyristor valve and the second thyristor valve automatically turn off. At this time, the main clamping capacitor C... d With energy-consuming module capacitor C sm The voltage polarity of the capacitor is opposite to that of the capacitor during the charging phase. For example... Figure 8 As shown, after the first thyristor valve and the second thyristor valve are closed, the second switch S2 of the auxiliary branch is opened, and the second thyristor T2 is turned on. At this time, the main clamping capacitor C... d With the first resistor R d A circuit is formed to dissipate energy. When the current in this circuit reaches zero, the second thyristor T2 automatically turns off; the energy dissipation module capacitor C... sm The energy is then dissipated by forming a circuit between the body diode of the second power switch Q2 and the second resistor r.

[0036] Accordingly, the present invention also provides a control method for a capacitor voltage clamping DC circuit breaker with energy dissipation function, applied to the aforementioned capacitor voltage clamping DC circuit breaker with energy dissipation function, the control method comprising: When the capacitor voltage clamping DC circuit breaker is first engaged, it enters a pre-charging phase to charge the main clamping capacitor C. d With energy-consuming module capacitor C sm Charge; When an energy consumption demand command is received, the system enters the energy consumption control mode to control the energy consumption power according to the energy consumption demand. When a command to disconnect a line fault is received, the system enters DC circuit breaking mode. After raising the voltage at the fault point to make the current in the conducting branch cross zero, the first switch S1 is disconnected to clear the fault.

[0037] As one optional embodiment, the pre-charging phase specifically includes: First pre-charging stage: The conducting branch, the second thyristor T2, and the first power switch Q1 are turned on to charge the main clamping capacitor C. d Charging is performed; when the main clamping capacitor C d When charged to the system voltage, the main clamping capacitor C d When the current in the branch reaches zero, the second thyristor T2 turns off automatically, and the phase ends. Second pre-charging stage: The conducting branch, the fourth thyristor T4, and the fifth thyristor T5 are turned on to charge the energy-consuming module capacitor C. sm Charging is performed; when the energy-consuming module capacitor C sm When charged to the system voltage, the energy-consuming module capacitor C sm When the current in the branch circuit crosses zero, the fourth thyristor T4 and the fifth thyristor T5 turn off automatically, and the phase ends.

[0038] Specifically, such as Figure 2 In the first pre-charge phase, the system begins to charge the main clamping capacitor C. d Uncontrolled charging is performed by turning on the first switch S1, the first thyristor T1, the second thyristor T2, and the first power switch Q1 until the main clamping capacitor C is activated. d When the current in this branch crosses zero after charging to the system voltage, the second thyristor T2 naturally turns off, and the main clamping capacitor C... d Charging complete; the first pre-charging phase is over.

[0039] like Figure 3 In the second pre-charging phase, the system begins to charge the energy-consuming module capacitor C. sm Uncontrolled charging is performed, turning on the fourth thyristor T4 and the fifth thyristor T5 until the energy-consuming module capacitor C is reached. sm When the circuit voltage is reached, the fourth thyristor T4 naturally turns off when the branch current crosses zero, and the energy-consuming module capacitor C... sm Charging complete; the second pre-charging phase ends.

[0040] As one optional embodiment, the energy consumption control based on energy demand includes: Turn on the conduction branch and disconnect the second thyristor T2, the third thyristor T3, and the fourth thyristor T4 in the variable clamping voltage module; Based on energy consumption requirements, the number of energy-consuming modules in operation is adjusted by controlling the on / off state of the fifth thyristor T5 in each energy-consuming module, and the energy-consuming module capacitor C in the corresponding energy-consuming module is adjusted by controlling the on / off state of the second power switch Q2 in the energy-consuming module. sm The voltage is adjusted to regulate the first resistor R. d The voltage is used to control energy consumption.

[0041] Specifically, when the fifth thyristor T5 in the energy-consuming module is turned on, the energy-consuming module is in the active state. At this time, the sixth thyristor T6 and the first power switch Q1 in the energy-consuming module are both turned off. The energy-consuming module capacitor C can be adjusted by controlling the on and off states of the second power switch Q2. sm The voltage magnitude is used to adjust the first resistor R. d The voltage magnitude determines the first resistor R. d The power consumption is controllable. When it is necessary to disconnect the power consumption module, the first power switch Q1 in the power consumption module is turned on, and the fifth thyristor T5 and the sixth thyristor T6 are turned off, so that the power consumption module capacitor C of the power consumption module is turned off. sm Bypassing allows for the removal of energy-consuming modules.

[0042] In energy consumption control mode, the number of energy consumption modules in operation is adjusted by controlling the fifth thyristor T5 within the energy consumption module, thereby adjusting the first resistor R. d (i.e., the voltage of the energy-consuming resistor) can be adjusted. Simultaneously, the capacitor voltage of a single energy-consuming module can be adjusted via the second power switch Q2 within the energy-consuming module, thereby achieving controllable power consumption of the energy-consuming resistor. Figure 4 As shown. Because the voltage of the energy-consuming resistor is clamped, the energy consumed by the resistor can be controlled by controlling the capacitor voltage.

[0043] As one optional embodiment, in the DC circuit breaker mode, the control method includes: During fault detection, the conduction branch is activated, and the variable clamping voltage module and the energy consumption module are disconnected. Upon receiving a trip command, the third thyristor T3 in the variable clamp voltage module and the sixth thyristor T6 in each of the energy-consuming modules are turned on, causing the main clamp capacitor C to... d With energy-consuming module capacitor C sm Connect them in series to raise the voltage until the current in the conducting branch is zero, then disconnect the first switch S1 to clear the fault.

[0044] As one optional embodiment, in the DC circuit breaker mode, the control method further includes: After clearing the fault, close the second switch S2 to make the auxiliary branch conduct, so as to form a resonant circuit; When the current in the resonant circuit crosses zero, the third thyristor T3 and the sixth thyristor T6 turn off automatically. After the third thyristor T3 and the sixth thyristor T6 are turned off, the first switch S1 and the second switch S2 are reset to disconnect the auxiliary branch and connect the conducting branch. Turning on the second thyristor T2 and the second power switch Q2 enables the main clamping capacitor C to... d By connecting with the first resistor R d The formed loop dissipates energy, causing the energy-consuming module capacitor C to... sm Energy is dissipated through the loop formed with the second resistor r.

[0045] Specifically, the DC circuit breaking mode includes three stages: Fault detection phase: From the occurrence of a fault to the detection of the fault, the first switch S1 is turned on, the first thyristor T1 is turned on, the second thyristor T2, the third thyristor T3, and the fourth thyristor T4 in the variable clamping voltage module are turned off, and the first power switch Q1 in each energy consumption module is turned off. At this time, the circuit breaker is not engaged, and the power system operates normally.

[0046] Fault clearing phase: Upon receiving the trip command, the third thyristor T3 and the sixth thyristor T6 in each energy-consuming module are turned on. At this time, the capacitors C in each energy-consuming module... sm With the main clamping capacitor C d The series connection causes the potential at node n to rise. Once the voltage across the first switch S1 gradually rises to the same level, the line fault current is zero. Disconnecting the first switch S1 clears the fault. Figure 6 As shown.

[0047] Reset Phase: The reset phase is divided into two sub-phases. In reset phase one, after the fault is cleared, the second switch S2 is turned on, and capacitor C... d C sm With inductor L dc L m A resonant circuit is formed. When the resonant current crosses zero, the third thyristor T3 and the sixth thyristor T6 automatically turn off. After the thyristors turn off, the first switch S1 and the second switch S2 are reset. Figure 7 As shown. However, at this time, the capacitor direction is opposite to that during pre-charging, requiring the capacitor's energy to be consumed. Entering the second reset stage, the second thyristor T2 and the second power switch Q2 of each energy-consuming module are turned on, utilizing the second resistor in each energy-consuming module to dissipate energy, such as... Figure 8As shown, this enables rapid energy dissipation.

[0048] This invention provides a capacitor voltage clamping DC circuit breaker with energy dissipation function and its control method. The DC circuit breaker is connected between the DC poles of a flexible DC transmission system. Its structure adopts a series connection of main branches and modular cascading. Its modularity enables adjustable energy dissipation power, allowing energy dissipation modules to be enabled or disabled as needed. Furthermore, without changing the topology, the DC energy dissipation device and the DC circuit breaker function can be reused by controlling the opening and closing of switching devices. The structure is simple, highly reliable, cost-effective, and practical, making it suitable for protection in large-scale long-distance transmission systems.

[0049] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A capacitor voltage clamping DC circuit breaker with energy dissipation function, characterized in that, The capacitor voltage clamping DC circuit breaker is connected between the DC poles of the flexible DC transmission system, including: The conducting branch includes a first switch and a first thyristor connected in series; The series-connected variable clamping voltage module and at least one energy-consuming module are used together to control the energy consumption power according to the energy consumption demand, and to control the variable clamping voltage to make the current of the conducting branch cross zero in the event of a fault, and then disconnect the first switch to clear the fault. An auxiliary branch, including a second switch, is connected between the DC poles to assist in resetting each module after the fault is cleared.

2. The capacitor voltage clamping DC circuit breaker with energy dissipation function as described in claim 1, characterized in that, The variable clamping voltage module includes: a current-limiting inductor, a fourth thyristor, a first resistor, a main clamping capacitor, and a second and third thyristors connected in reverse parallel. Wherein, one end of the current-limiting inductor is connected to the anode of the second thyristor, the cathode of the third thyristor, the anode of the fourth thyristor, and the first end of the first resistor; the first end of the main clamping capacitor is connected to the cathode of the second thyristor and the anode of the third thyristor; and the second end of the main clamping capacitor is connected to the cathode of the fourth thyristor and the second end of the first resistor.

3. The capacitor voltage clamping DC circuit breaker with energy dissipation function as described in claim 2, characterized in that, The energy-consuming module includes: an energy-consuming module capacitor, a second resistor, a first power switch with a reverse parallel diode, a second power switch with a reverse parallel diode, and a fifth and sixth thyristors connected in reverse parallel. In this configuration, both the first power switch and the second power switch are insulated-gate bipolar transistors (IGBTs). The collector of the first power switch is connected to the anode of the fifth thyristor and the cathode of the sixth thyristor. The collector of the second power switch is connected to the first terminal of the energy-consuming module capacitor, the cathode of the fifth thyristor, and the anode of the sixth thyristor. The emitter of the second power switch is connected to the first terminal of the second resistor. The emitter of the first power switch is connected to the second terminal of the energy-consuming module capacitor and the second terminal of the second resistor.

4. The capacitor voltage clamping DC circuit breaker with energy dissipation function as described in claim 3, characterized in that, The operating modes of the capacitor voltage clamping DC circuit breaker include energy consumption control mode. The energy consumption control mode adjusts the voltage of the energy consumption module capacitor by controlling the on / off state of the fifth thyristor, the first power switch, and the second power switch, thereby adjusting the voltage of the first resistor to control energy consumption power; wherein, the first resistor is used for centralized energy consumption.

5. The capacitor voltage clamping DC circuit breaker with energy dissipation function as described in claim 3, characterized in that, The operating modes of the capacitor voltage clamping DC circuit breaker include DC circuit breaking mode. In the DC circuit breaking mode, by controlling the switching on and off of each thyristor in the variable clamping voltage module and the energy consumption module, the main clamping capacitor and the energy consumption module capacitor are connected in series to raise the voltage at the fault point. After the current in the conducting branch crosses zero, the first switch is disconnected to clear the fault. After clearing the fault, the first switch is reset by controlling the auxiliary branch, and the energy of the main clamping capacitor and the energy consumption module capacitor is dissipated by turning on the second thyristor and the second power switch.

6. A control method for a capacitor voltage clamping DC circuit breaker with energy dissipation function, characterized in that, The control method is applied to a capacitor voltage clamping DC circuit breaker with energy dissipation function as described in any one of claims 1 to 5, and the control method includes: When the capacitor voltage clamping DC circuit breaker is first put into operation, it enters the pre-charging stage to charge the main clamping capacitor and the energy dissipation module capacitor. When an energy consumption demand command is received, the system enters the energy consumption control mode to control the energy consumption power according to the energy consumption demand. When a command to disconnect a line fault is received, the system enters DC circuit breaking mode. After raising the voltage at the fault point to make the current in the conducting branch cross zero, the first switch is disconnected to clear the fault.

7. The control method for a capacitor voltage clamping DC circuit breaker with energy dissipation function as described in claim 6, characterized in that, The pre-charging phase specifically includes: First pre-charging stage: The conducting branch, the second thyristor, and the first power switch are turned on to charge the main clamping capacitor; when the main clamping capacitor is charged to the system voltage, the current in the branch where the main clamping capacitor is located crosses zero, the second thyristor turns off automatically, and the stage ends. Second pre-charging stage: The conducting branch, the fourth thyristor, and the fifth thyristor are turned on to charge the energy-consuming module capacitor; when the energy-consuming module capacitor is charged to the system voltage, the current in the branch where the energy-consuming module capacitor is located crosses zero, and the fourth thyristor and the fifth thyristor turn off automatically, and the stage ends.

8. The control method for a capacitor voltage clamping DC circuit breaker with energy dissipation function as described in claim 6, characterized in that, The energy consumption control based on energy demand includes: The conduction branch is turned on, and the second thyristor, third thyristor, and fourth thyristor in the variable clamping voltage module are turned off; Based on the energy consumption demand, the number of energy consumption modules in operation is adjusted by controlling the on / off state of the fifth thyristor in each energy consumption module, and the voltage of the energy consumption module capacitor in the corresponding energy consumption module is adjusted by the second power switch in the energy consumption module, thereby adjusting the voltage of the first resistor and realizing energy consumption power control.

9. The control method for a capacitor voltage clamping DC circuit breaker with energy dissipation function as described in claim 6, characterized in that, In the DC circuit breaker mode, the control method includes: During fault detection, the conduction branch is activated, and the variable clamping voltage module and the energy consumption module are disconnected. Upon receiving a trip command, the third thyristor in the variable clamp voltage module and the sixth thyristor in each of the energy-consuming modules are turned on, so that the main clamp capacitor and the energy-consuming module capacitor are connected in series to raise the voltage until the current in the conducting branch is zero, and the first switch is turned off to clear the fault.

10. The control method for a capacitor voltage clamping DC circuit breaker with energy dissipation function as described in claim 9, characterized in that, In the DC circuit breaker mode, the control method further includes: After clearing the fault, close the second switch to make the auxiliary branch conduct, so as to form a resonant circuit; When the current in the resonant circuit crosses zero, the third thyristor and the sixth thyristor turn off automatically. After the third thyristor and the sixth thyristor are turned off, the first switch and the second switch are reset to disconnect the auxiliary branch and connect the conducting branch. The second thyristor and the second power switch are turned on, so that the main clamping capacitor dissipates energy through the circuit formed with the first resistor, and the energy dissipation module capacitor dissipates energy through the circuit formed with the second resistor.

Images