Natural commutation type hybrid DC circuit breaker control and protection device and method

Abstract

The invention relates to a natural commutation type hybrid DC circuit breaker control and protection device and method, a main branch in a topological structure is provided with a rapid mechanical switch, and a transfer branch is a power electronic valve group of a diode bridge type multi-parallel structure and is used for realizing rapid current transfer when a fault occurs; the energy consumption branch is provided with a metal oxide lightning arrester and is used for dissipating fault energy; the control protection device is provided with an input control interface, an output control interface and a core processing unit; the input control interface comprises an opening input node, a closing input node and a locking input node, and is used for receiving opening, closing and locking instructions. According to the device and the method, based on mechanical and solid-state circuit breaking technologies, large-current and low-loss through-flow operation of the circuit breaker is realized through a mechanical switch, high-response and rapid arc-free breaking of the circuit breaker is realized through a solid-state switch, and the purpose of rapid breaking of large-capacity short-circuit current is realized through sequential response control of each component through a control and protection strategy; and the overall performance and reliability of the ship power system are improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of ship power system automation, in particular to a natural commutation type hybrid DC circuit breaker control and protection method, which is suitable for fault isolation and operation control of a ship medium-voltage DC distribution network, and is especially suitable for a high-dynamic and high-load ship power system environment. BACKGROUND

[0002] The protection and control of the DC distribution network in the current ship integrated power system mainly rely on traditional air-type DC circuit breakers. With the increase of voltage levels and capacity of future ship power systems, and the development of ship operating environments towards high dynamics and high loads, air-type DC circuit breakers will face problems such as limited current-limiting breaking performance, insufficient breaking speed, and increased volume and weight. The existing performance parameters and control and protection strategies of air-type circuit breakers cannot adapt to the development of the system, and may cause protection misoperation or failure, which is difficult to meet the protection requirements of high coordination, speed, reliability and stability.

[0003] The existing hybrid DC circuit breaker technology (such as patent document CN110391646A and patent document CN110932245B) mainly faces the land DC transmission system, and has the following adaptability problems:

[0004] Both patent document CN110391646A and patent document CN110932245B are aimed at modular multilevel converter (MMC) flexible DC power grid, and do not consider the high-dynamic load, complex electromagnetic interference and space limitation of ship power systems. For example, although the two-out-of-three logic module of patent document CN110932245B improves reliability, the redundant structure is complex and the volume is large, which is not suitable for ship installation. Both patent document CN110391646A and patent document CN110932245B use forced commutation (by turning off the main branch semiconductor device string to force commutation), which requires additional energy consumption, and the commutation speed is greatly affected by circuit parameters. Natural commutation topology is not used, and the ability to adapt to ship energy saving requirements is weak. The interface of patent document CN110391646A uses conventional electrical connection, and patent document CN110932245B does not explicitly specify the interface protocol, and neither of them considers the complex electromagnetic environment of the ship (such as electromagnetic radiation of the propulsion system and radar equipment), which is prone to cause command transmission errors. Patent document CN110932245B adds a lightning arrester non-uniform current judgment, but neither of them covers the grounding protection, differential protection and switch quantity protection commonly used in ship power systems, and cannot cope with ship cable damage, load short circuit and other specific faults.

[0005] Therefore, there is an urgent need for a hybrid DC circuit breaker control and protection device and method that adapts to ship power systems to solve the response speed, adaptability and reliability problems of the existing technology. SUMMARY

[0006] To address the limitations of air-cooled DC circuit breakers in ship integrated power systems, such as limited breaking performance, insufficient breaking speed, and ineffective control strategies for short-circuit protection in future high-capacity systems, this invention proposes a natural commutation type hybrid DC circuit breaker control and protection device and method. This device and method are based on mechanical and solid-state circuit breaking technologies. Mechanical switches enable high-current, low-loss current-carrying operation of the circuit breaker, while solid-state switches enable high-response, fast, arc-free breaking. Through control and protection strategies, the timing response of each component is controlled, achieving rapid breaking of high-capacity short-circuit currents. This improves the overall performance and reliability of ship power systems and can be applied to research and engineering applications in the protection and control of ship medium-voltage power systems.

[0007] To achieve the above objectives, the technical solution of the present invention is: a natural commutation type hybrid DC circuit breaker control and protection device, comprising a natural commutation type bridge topology and a control and protection device. The natural commutation type bridge topology includes a main branch, a transfer branch, and an energy dissipation branch. The main branch is equipped with a fast mechanical switch for conducting rated current during normal operation. The transfer branch is a power electronic valve group with a diode bridge multi-parallel structure for rapid current transfer during faults. The energy dissipation branch is equipped with a metal oxide surge arrester for dissipating fault energy. The control and protection device includes an input control interface, an output control interface, and a core processing unit. The input control interface includes a tripping input node, a closing input node, and a blocking input node for receiving tripping, closing, and blocking commands.

[0008] Furthermore, the output control interface adopts a fiber optic ST interface to send control commands in accordance with the IEC60044-8 FT3 protocol, including commands for opening and closing of fast mechanical switches and commands for opening and closing of power electronic valve groups in transfer branches.

[0009] Furthermore, the core processing unit includes an FPGA and a CPU. The FPGA is used to implement instantaneous overcurrent protection, and the CPU is used to implement overvoltage protection, undervoltage protection, differential protection, grounding protection, and switching quantity protection.

[0010] A control and protection method for a natural commutation type hybrid DC circuit breaker is disclosed. Based on a natural commutation type hybrid DC circuit breaker control and protection device, the hybrid DC circuit breaker achieves rapid commutation and arc extinguishing of load current or fault current during opening and closing by coordinating the mechanical circuit and power electronic circuit during the opening and closing processes. This enables the hybrid DC circuit breaker to achieve rapid establishment and transfer of load current during opening and closing, thereby realizing the control and protection functions of the hybrid DC circuit breaker.

[0011] Furthermore, the method specifically includes:

[0012] Closing sequence control: Upon receiving a closing command and without an alarm signal, the control and protection device sends an IEC60044-8 FT3 protocol message via the fiber optic ST interface to activate the transfer branch power electronic valve group; the load current is then conducted through the transfer branch. If the closing overcurrent protection fails to operate, a delay of t is applied. hz Subsequently, the fiber optic ST transmits a command to close the main branch fast circuit breaker according to the IEC60044-8 FT3 protocol. hz This is the main branch closing delay time setting value (ms). When the load current is switched on through the main branch, the fast circuit breaker is read and judged to be closed in place by the optical fiber according to the IEC60044-8 FT3 protocol. Then, the ST optical fiber sends a disconnection transfer branch command and the closing is successful. If the closing overcurrent protection is activated or the fast circuit breaker is not closed, the ST optical fiber sends a disconnection transfer branch command and the closing fails.

[0013] Tripping sequence control: Before tripping, the current flows through the main branch. Upon receiving the tripping command, the control and protection device sends an IEC60044-8 FT3 protocol message via ST fiber optic cable to open the power electronic valve group of the transfer branch. It then sends a command to trip the fast circuit breaker via fiber optic cable according to the IEC60044-8 protocol. At this time, the current in the main branch gradually switches to the transfer branch, with a delay of t. fz Alternatively, after the ST fiber optic cable reads and determines that the fast circuit breaker has been tripped according to the IEC60044-8 FT3 protocol message, it sends tripping and transfer branch commands step by step via the ST fiber optic cable. At this time, the load current is consumed through the energy-consuming branch. If any judgment node has an error during this process, the tripping is considered to have failed.

[0014] Opening and closing control and protection: During closing, if the control and protection device receives an external closing command and no alarm occurs in the mechanical switch or power electronic branch, the transfer branch IGBT is activated with a 10ms delay. Provided the overcurrent protection does not trip, the main branch of the mechanical switch is closed, and after a 20ms delay, the position of the main branch mechanical switch is determined. If it is in the closed position, the transfer branch IGBT is locked, and closing is successful. Any other abnormal situation will be considered a closing failure, and the transfer branch IGBT will be locked, triggering an alarm and outputting a lockout signal. During opening, if the control and protection device receives an external opening command and no alarm occurs in the mechanical switch or power electronic branch,… If the IGBT of the transfer branch is activated, the mechanical switch of the main branch will be tripped simultaneously. The current transfer delay is 3.8ms. After continuously judging 3 signal acquisition points, it is determined whether the difference between the total branch current and the power electronic branch current is less than 1.5% of the rated current. After a delay of 0.2ms to ensure the post-arc insulation is restored, the contact distance of the mechanical switch is detected and the IGBT of the transfer branch is locked. After another delay of 3 seconds for current dissipation, it is again determined whether the total branch current is less than 30% of the rated current. If it is less, the tripping is successful. Otherwise, the tripping is considered a failure, the IGBT of the transfer branch is locked, and an alarm is triggered.

[0015] Furthermore, the input control interface includes opening control, closing control, and interlocking control; the output control interface includes mechanical switch opening and closing control, transfer branch opening control, and transfer branch disconnection control.

[0016] Furthermore, the tripping control: when the tripping input node is closed, the closing input node is open, and the interlocking input node is open, the control protection device performs the tripping operation;

[0017] Furthermore, the closing control: when the tripping input node is open, the closing input node is closed and the interlocking input node is open, the control protection device performs the closing operation;

[0018] Furthermore, the interlocking control: when the interlocking access node is closed, all opening and closing control commands are blocked, and the circuit breaker is prohibited from operating.

[0019] Furthermore, the fast mechanical switch adopts an external transverse magnetic field structure, which increases the arc voltage of the vacuum break through the transverse magnetic field and accelerates the transfer of the break current to the transfer branch.

[0020] The beneficial effects of this invention are:

[0021] (1) The input and output of system signals are realized based on the interface of the hybrid DC circuit breaker control and protection device. The input signal realizes the three important functions of the circuit breaker: opening control, closing control, and interlocking control through the input control interface. The output signal realizes the opening and closing control of the mechanical switch (i.e., the fast circuit breaker) and the opening and closing control of the transfer branch (i.e., the power electronic valve group) through the output control structure.

[0022] (2) Based on the fast protection function of the hybrid DC circuit breaker, the control protection device, together with the FPGA and CPU, jointly judges and collects signals such as current and voltage, and jointly realizes overcurrent protection, overvoltage protection, undervoltage protection, differential protection, grounding protection, grounding current protection, and switching quantity protection. Among them, the overcurrent protection includes instantaneous overcurrent, definite-time overcurrent, inverse-time overcurrent protection and overcurrent early warning functions, and the grounding protection includes grounding current and short-delay protection, grounding current alarm and other functions, which together complete the judgment and response under various abnormal operating conditions.

[0023] (3) When a hybrid DC circuit breaker achieves the function of quickly interrupting fault current, the time for the fault detection and the circuit breaker to be completely separated needs to be controlled within 6 to 7 ms. The tripping time of the primary circuit breaker is 3 to 4 ms, so the protection action time (including the opening action time) needs to be controlled within 2 ms. Attached Figure Description

[0024] Figure 1This is a diagram of the hybrid DC circuit breaker control and protection device of the present invention;

[0025] Figure 2 This is a topology diagram of the hybrid DC circuit breaker of the present invention;

[0026] Figure 3 This is a flowchart of the closing process of the hybrid DC circuit breaker of the present invention;

[0027] Figure 4 This is a flowchart of the tripping process of the hybrid DC circuit breaker of the present invention. Detailed Implementation

[0028] To realize the functional design of "a control and protection method for a natural commutation type hybrid DC circuit breaker" described above, this chapter further introduces the implementation scheme of important functions.

[0029] This invention proposes a control and protection method for a natural commutation hybrid DC circuit breaker. In terms of topology design, a natural commutation hybrid DC circuit breaker structure based on a bridge circuit is proposed. In terms of control and protection logic, the protection device implements the circuit's opening, closing, and blocking functions according to the coordination sequence of the circuit breaker components. Figure 1 As shown.

[0030] In terms of functional design, the method of this invention can suppress and trip fault current within 5ms. When the system is in normal operation, the rated current flows through the main branch of the fast mechanical switch. When the relay protection device detects and determines a system fault, it triggers a trip command, the fast mechanical switch trips, and the fault current is quickly transferred from the main branch to the power electronic branch. After the transfer is completed, the insulation of the fast mechanical switch in the main branch is established, further shutting off the power electronic devices and transferring the fault current to the MOV branch for dissipation. By transferring and limiting fault current through this method, rapid fault current interruption can be achieved, significantly enhancing the protection capability of electrical equipment under complex power system operating conditions.

[0031] The specific design of the control and protection method for the natural commutation type hybrid DC circuit breaker is as follows:

[0032] 1) Interface of hybrid DC circuit breaker control and protection device

[0033] The control and protection device provides three nodes for receiving opening and closing control commands: opening input, closing input, and interlocking input. It also provides a fiber optic ST interface to control the opening and closing process using the IEC60044-8 FT3 protocol. The input control interface of the control and protection device includes: opening control, closing control, and interlocking control; the output control interface includes: mechanical switch (fast circuit breaker) opening and closing control, transfer branch (power electronic valve group) opening control, and transfer branch (power electronic valve group) disconnection control.

[0034] 2) Hybrid DC circuit breaker fast protection function

[0035] The control and protection device has overcurrent protection, overvoltage protection and undervoltage protection functions. The instantaneous overcurrent protection is implemented by FPGA, while other protections are implemented by CPU. In addition, other protection schemes include differential protection, grounding protection, grounding current protection and switching quantity protection, which together realize the response of the hybrid circuit breaker under various system fault conditions.

[0036] 3) Hybrid DC circuit breaker control and protection logic

[0037] During the opening and closing processes, the hybrid DC circuit breaker achieves rapid commutation and arc extinguishing of load current or fault current during opening and rapid establishment and transfer of load current during closing by coordinating the mechanical circuit and the power electronic circuit. Specific implementation examples:

[0039] (1) Hybrid DC circuit breaker structural design

[0040] 1) Topology design

[0041] Based on the theory of vacuum arc and the influence of factors such as opening distance and magnetic field on the arc voltage at the vacuum break point, an external transverse magnetic field is used to increase the vacuum arc voltage. The high arc voltage of a fast mechanical switch rapidly transfers the break current. Combined with a multi-parallel diode bridge scheme, natural commutation and breaking are achieved. Figure 2 As shown.

[0042] 2) Control Interface Design

[0043] Hybrid DC circuit breaker input control interface for control and protection devices:

[0044] ①Break-off control: When the break-off input node is closed, the closing input node is open, or the interlocking node is open, the control and protection device executes the break-off control of the hybrid DC circuit breaker.

[0045] ② Closing control: When the tripping input node is open, the closing input node is closed, or the interlocking node is open, the control and protection device executes the closing control of the hybrid DC circuit breaker.

[0046] ③ Blocking control: When the blocking node is closed, control commands to the hybrid DC circuit breaker are blocked.

[0047] The output control interface of the hybrid DC circuit breaker for control and protection devices:

[0048] ① Mechanical switch (fast circuit breaker) opening and closing control: Use fiber optic ST interface to send opening or closing commands according to IEC60044-8FT3 protocol.

[0049] ② Transfer branch (power electronic valve group) opening control: Use fiber optic ST interface to send closing command according to IEC60044-8FT3 protocol.

[0050] ③ Transfer branch (power electronic valve group) disconnection control: Use fiber optic ST interface to send IEC60044-8FT3 protocol disconnection command.

[0051] (2) Control and protection methods for hybrid DC circuit breakers

[0052] 1) Opening and closing timing control

[0053] The control and protection device implements the opening and closing logic of the hybrid DC circuit breaker using an FPGA. The control timing for the mechanical and power electronic circuits is as follows:

[0054] Upon receiving the closing command, an IEC60044-8 FT3 protocol message is sent via ST fiber optic cable to activate the power electronic valve group of the transfer branch, and the load current is turned on through the transfer branch. If the closing overcurrent protection does not operate, a delay of t is applied. hz Subsequently, the fiber optic ST transmits a command to close the main branch fast circuit breaker according to the IEC60044-8 FT3 protocol. hz This is the main branch closing delay time setting value (ms). When the load current is switched on through the main branch, the fast circuit breaker is read and judged to be closed in place by the optical fiber according to the IEC60044-8 FT3 protocol. Then, the ST optical fiber sends a disconnection transfer branch command and the closing is successful. If the closing overcurrent protection is activated or the fast circuit breaker is not closed, the ST optical fiber sends a disconnection transfer branch command and the closing fails.

[0055] Before the circuit breaker trips, current flows through the main branch. Upon receiving the trip command, an IEC60044-8FT3 protocol message is sent via ST fiber optic cable to activate the power electronic valve group in the transfer branch. The command to trip the fast circuit breaker is then sent via fiber optic cable according to the IEC60044-8 protocol. At this time, the current in the main branch gradually commutates to the transfer branch, with a delay of t. fz Alternatively, after ST fiber optic communication reads and determines that the fast circuit breaker has tripped according to the IEC60044-8 FT3 protocol message, ST fiber optic communication sends tripping and transfer branch commands level by level. At this time, the load current is consumed through the energy-consuming branch. If any judgment node has an error during this process, the tripping is considered to have failed.

[0056] 2) Circuit breaker opening and closing control and protection process

[0057] In the actual control and protection process of the timing coordination between mechanical switches and power electronic switches, when closing, if the control and protection device receives an external closing command and no alarm occurs in the mechanical switch or power electronic branch, the IGBT of the transfer branch is turned on after a 10ms delay. Provided the overcurrent protection does not activate, the main branch of the mechanical switch is closed, and after a 20ms delay, the position of the main branch mechanical switch is determined. If it is in the closed position, the IGBT is locked, and the closing is successful. Any other abnormal situation will be considered a closing failure, and the IGBT will be locked, triggering an alarm and outputting a lockout signal. When opening, if the control and protection device receives an external opening command and no alarm occurs in the mechanical switch or power electronic branch, the IGBT is turned on after a 10ms delay. If no alarm occurs in the electronic branch, the IGBT branch is activated while the main branch mechanical switch is tripped. The current transfer delay is 3.8ms. After continuously checking three signal acquisition points, it is determined whether the difference between the total branch current and the power electronic branch current is less than 1.5% of the rated current. After a 0.2ms delay to ensure post-arc insulation recovery, the contact distance of the mechanical switch is checked and the IGBT is locked. After another 3-second delay for current dissipation, three more signal acquisition points are checked. The total branch current is then checked to see if it is less than 30% of the rated current. If it is, the tripping is successful; otherwise, the tripping fails, the IGBT is locked, and an alarm is triggered. The closing and tripping control protection procedures are as follows: Figure 3 , Figure 4 .

Claims

1. A natural commutation type hybrid DC circuit breaker control and protection device, characterized by, The natural commutation type bridge topology comprises a main branch, a transfer branch and an energy consumption branch; the main branch is provided with a fast mechanical switch for conducting rated current in normal operation; the transfer branch is a power electronic valve group in a diode bridge type multi-parallel structure for realizing fast current transfer in a fault; the energy consumption branch is provided with a metal oxide lightning arrester for dissipating fault energy; The control protection device is provided with an input control interface, an output control interface and a core processing unit; the input control interface comprises a tripping input node, a closing input node and a blocking input node for receiving tripping, closing and blocking instructions. 2.The natural commutation type hybrid DC circuit breaker control and protection device according to claim 1, characterized in that, The output control interface adopts a fiber ST interface and sends control instructions including fast mechanical switch tripping and closing instructions, transfer branch power electronic valve group opening and breaking instructions in IEC60044-8 FT3 protocol. 3.The natural commutation hybrid DC circuit breaker control and protection device according to claim 2, characterized in that, The core processing unit comprises an FPGA for realizing instantaneous overcurrent protection and a CPU for realizing overvoltage protection, undervoltage protection, differential protection, ground protection and switching value protection.

4. A natural commutation type hybrid DC circuit breaker control and protection method based on the natural commutation type hybrid DC circuit breaker control and protection device of claim 3, characterized by, In the tripping and closing process of the hybrid DC circuit breaker, the mechanical circuit and the power electronic circuit are controlled in time sequence to realize fast commutation and arc extinction of load current or fault current in the tripping process, fast establishment and transfer of load current in the closing process, thereby realizing the control protection function of the hybrid DC circuit breaker. 5.The control and protection method of a natural commutation hybrid DC circuit breaker according to claim 4, characterized in that, The method specifically comprises: Closing sequence control: Upon receiving a closing command and without an alarm signal, the control and protection device sends an IEC60044-8 FT3 protocol message via the fiber optic ST interface to activate the transfer branch power electronic valve group; the load current is then conducted through the transfer branch. If the closing overcurrent protection fails to operate, a delay of t is applied. hz Subsequently, the fiber optic ST transmits a command to close the main branch fast circuit breaker according to the IEC60044-8 FT3 protocol. hz This is the main branch closing delay time setting value (ms). When the load current is switched on through the main branch, the fast circuit breaker is read and judged to be closed in place by the optical fiber according to the IEC60044-8 FT3 protocol. Then, the ST optical fiber sends a disconnection transfer branch command and the closing is successful. If the closing overcurrent protection is activated or the fast circuit breaker is not closed, the ST optical fiber sends a disconnection transfer branch command and the closing fails. Timing control of opening: before opening, the current is conducted through the main branch, when receiving the opening instruction, the control protection device sends the IEC60044-8 FT3 protocol message through the ST optical fiber, opens the transfer branch power electronic valve group instruction, and sends the fast circuit breaker opening instruction through the optical fiber according to the IEC60044-8 protocol, at this time, the current of the main branch is gradually transferred to the transfer branch, and the delay t fz or after reading and judging that the fast circuit breaker is opened through the ST optical fiber according to the IEC60044-8 FT3 protocol message, the opening instruction of the transfer branch is sent through the ST optical fiber, at this time, the load current is consumed through the energy consumption branch. In this process, if there is an error in any judgment node, it is considered that the opening fails. Tripping and closing control and protection: when closing, the control protection device receives an external closing instruction and the mechanical switch or the power electronic branch does not have an alarm, the transfer branch IGBT is turned on for 10 ms, the main branch mechanical switch is closed under the premise that the overcurrent protection does not act, and the position of the main branch mechanical switch is judged after a delay of 20 ms, if it is in the closing position, the transfer branch IGBT is blocked, the closing is successful, otherwise, the closing is failed, the transfer branch IGBT is blocked, an alarm is given and a blocking signal is output; when tripping, the control protection device receives an external tripping instruction and the mechanical switch or the power electronic branch does not have an alarm, the transfer branch IGBT is turned on and the main branch mechanical switch is tripped, the current transfer delay is 3.8 ms, after continuously judging three signal collection points, whether the difference between the total branch current and the power electronic branch current is less than 1.5% of the rated current is judged, after a delay of 0.2 ms to ensure the recovery of post-arc insulation, the contact distance of the mechanical switch is detected and the transfer branch IGBT is blocked, after a current dissipation delay of 3 seconds, three signal collection points are continuously judged, whether the total branch current is less than 30% of the rated current is judged, if yes, the tripping is successful, otherwise, the tripping is failed, the transfer branch IGBT is blocked and an alarm is given.

6. The control and protection method of a natural commutation hybrid DC circuit breaker according to claim 5, characterized in that, The control of the input control interface comprises tripping control, closing control and blocking control; The control of the output control interface comprises mechanical switch tripping and closing control, transfer branch opening control and transfer branch breaking control.

7. The control and protection method of a natural commutation hybrid DC circuit breaker according to claim 6, characterized in that, The tripping control: when the tripping input node is closed, the closing input node is disconnected and the blocking input node is disconnected, the control protection device performs tripping operation. 8.The control and protection method of a natural commutation hybrid DC circuit breaker according to claim 6, characterized in that, The closing control controls the protection device to perform a closing operation when the opening incoming node is disconnected, the closing incoming node is connected, and the locking incoming node is disconnected. 9.The control and protection method of a natural commutation hybrid DC circuit breaker according to claim 6, wherein, The locking control shields all closing and opening control instructions and prohibits the breaker from acting when the locking incoming node is connected.

10. The control and protection method of a natural commutation hybrid DC circuit breaker according to claim 6, characterized in that, The fast mechanical switch adopts an external transverse magnetic field structure, and the transverse magnetic field is used to increase the vacuum gap arc voltage and accelerate the gap current to shift to the shifting branch.

Images