An electronic auxiliary circuit breaker control strategy design method and device

Abstract

The application discloses an electronic auxiliary circuit breaker control strategy design method and device, wherein the method comprises the following steps: S1, when detecting that the line current is increased to exceed the maximum load current, the mechanical arm is controlled by the mechanical switch to start moving; S2, the mechanical arm activates the electronic auxiliary circuit breaker by pulling the arc and using the arc voltage to open the power electronic converter branch after waiting for a set time; S3, after the fault current is converted to the power electronic converter branch and the arc stress on the main contact is relieved, the power electronic converter branch is closed after waiting for a set time, and the residual electromagnetic energy is released by the varistor branch; S4, with the movement of the mechanical arm, the mechanical switch on the mechanical arm is closed along with the opening of the main contact, and the electronic circuit is provided with electrical isolation under the zero-current condition. The application is promoted based on the movement of the mechanical arm, the electronic auxiliary circuit breaker does not need a complex control circuit to control the switching element, and the cost in the early design and prototype production is reduced.

Description

Technical Field

[0001] This invention relates to the field of power system technology, and specifically to a design method and device for electronic auxiliary circuit breaker control strategy. Background Technology

[0002] With the implementation of national energy conservation and emission reduction policies, photovoltaic, energy storage, and electric vehicles are being widely connected to the power distribution network. Compared to AC systems, the development of DC power grids reduces the loss of renewable energy and can provide users with safe, flexible, and efficient power supply services.

[0003] Currently, typical loads in municipal and housing construction scenarios are showing a trend towards DC conversion, with pilot applications already underway for items such as streetlights, traffic lights, and DC inverter air conditioners. The large-scale application of DC power grids is inseparable from the development of DC circuit breakers. Unlike traditional AC interruption, DC lines are more difficult to interrupt due to their lack of natural zero-crossing points, low line impedance, and rapid fault current rise.

[0004] Over the past decade, DC circuit breakers have experienced rapid development in my country, mainly falling into three categories: pure solid-state, hybrid, and mechanical. Mechanical circuit breakers primarily interrupt fault currents by lengthening the arc, adding arc-extinguishing grids, changing the arc-extinguishing medium, using magnetic blowout arc extinguishing, air blowout arc extinguishing, and multi-stage breaking. However, prolonged use inevitably leads to severe erosion between metal contacts, causing performance degradation. Furthermore, with the development of new power systems, the millisecond-level breaking time of traditional mechanical circuit breakers is no longer sufficient to meet protection requirements. Solid-state circuit breakers offer microsecond-level breaking speeds and, due to the use of semiconductor devices, avoid arc generation. However, their high cost is a major limiting factor for their widespread adoption. They also suffer from significant conduction losses, complex circuit designs, and a lack of reliable electrical isolation. Hybrid circuit breakers, combining the advantages of both, offer lower prices, faster breaking speeds, and lower conduction losses. However, their more complex structural design and commutation process present challenges, and their price is significantly higher than that of traditional mechanical circuit breakers. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a method and device for designing control strategies for electronic auxiliary circuit breakers, so as to accurately simulate the opening and closing process of electronic auxiliary circuit breakers when low-voltage DC system faults occur, and to provide a reference for the construction of related systems and the research and development and configuration of related protection devices.

[0006] To solve the above-mentioned technical problems, the present invention provides a method for designing an electronic auxiliary circuit breaker control strategy, comprising:

[0007] Step S1: When the line current is detected to rise above the maximum load current, the robotic arm starts to move under the control of a mechanical switch.

[0008] In step S2, the robotic arm activates the electronic auxiliary circuit breaker by pulling an arc and using the arc voltage after waiting for a set time, thus opening the power electronic converter branch.

[0009] Step S3: After the fault current is switched to the power electronic converter branch and the arc stress on the main contact is relieved, wait for a set time to shut down the power electronic converter branch and release the residual electromagnetic energy through the varistor branch.

[0010] In step S4, as the robotic arm moves, the mechanical switch on the robotic arm closes as the main contacts open, providing electrical isolation to the electronic circuit under zero current conditions.

[0011] Further, step S1 specifically includes:

[0012] When a short-circuit fault occurs at time t1, the fault current rises rapidly through the main contacts, and the mechanical switch begins to withstand the fault current.

[0013] As the fault current rapidly increases until time t2, when it reaches the threshold of the electromagnet or spring mechanism of the mechanical switch, the mechanical arm of the mechanical switch begins to move, the main contacts are opened, and an electric arc is generated in the contact gap.

[0014] Further, step S2 specifically includes:

[0015] The fault current reaches its peak at time t3 as the robotic arm moves, and then begins to decrease.

[0016] At time t4, the micro switch on the same robotic arm as the main contact closes and sends a signal to the control and drive circuit. The delay time from t2 to t4 is determined by the mechanical design and the moving speed of the robotic arm pulled by the spring mechanism.

[0017] When the MOSFET is turned on, the fault current is switched from the load DC to the power electronic commutator branch.

[0018] Furthermore, step S3 specifically includes: the control and timing circuit will send a shutdown signal after waiting for a set time, the MOSFET will turn off at time t5, and the power electronic commutation branch will turn off; the varistor will absorb the residual electromagnetic energy in the electrical system between t5 and t6.

[0019] Furthermore, the mechanical switching part of the electronically assisted DC circuit breaker adopts a mechanical switching model based on the Cassie arc model. The Cassie arc model is constructed using arc voltage, open-circuit voltage at both ends of the arc, arc time constant, and arc conductance.

[0020] Furthermore, the method also includes: building a Simulink model of an electronic auxiliary circuit breaker, wherein the Simulink model of the electronic auxiliary circuit breaker combines the mechanical switching part based on the Cassie arc model, the loop inductance and resistance, the system voltage and current, the varistor parameters, and the mechanical circuit breaker parameters.

[0021] Furthermore, the Simulink model of the electronic auxiliary circuit breaker uses a MOSFET device with a withstand voltage of 600V and a rated current of 140A. The MOSFET turn-on time is set to 1.0ms, the conduction time is set to 100μs, the buffer capacitor is 1μF, and the varistor clamping voltage is selected to be 1000V.

[0022] Furthermore, as the MOSFET is turned on, the fault current is transferred to the power electronic commutation branch, and the energy is released by the varistor branch during the period when the fault current begins to decrease to zero after the MOSFET is turned off.

[0023] The present invention also provides an electronic auxiliary circuit breaker control strategy design device, comprising:

[0024] The initial control module is used to initiate movement of the robotic arm under the control of a mechanical switch when the line current is detected to rise above the maximum load current.

[0025] The converter branch activation module is used by the robotic arm to activate the electronic auxiliary circuit breaker by pulling an arc and using the arc voltage after waiting for a set time, thereby opening the power electronic converter branch.

[0026] The commutator branch shutdown module is used to shut down the power electronic commutator branch after the arc stress on the main contacts is relieved when the fault current is switched to the power electronic commutator branch, and the residual electromagnetic energy is released by the varistor branch.

[0027] An isolation module is used to provide electrical isolation to electronic circuits under zero-current conditions when the mechanical switches on the robotic arm close as the main contacts open during the movement of the robotic arm.

[0028] Furthermore, the device also includes a model building module for building a Simulink model of an electronic auxiliary circuit breaker, wherein the Simulink model of the electronic auxiliary circuit breaker combines the mechanical switching part based on the Cassie arc model, the loop inductance and resistance, the system voltage and current, the varistor parameters, and the mechanical circuit breaker parameters.

[0029] The implementation of this invention has the following beneficial effects: This invention can accurately simulate the opening process of an electronic auxiliary circuit breaker during a low-voltage DC system fault, providing a reference for the construction of related systems and the research and configuration of related protection devices; compared with the complex structural design and commutation process of hybrid DC circuit breakers, this invention optimizes the timing control process, and compared with the relatively high conduction loss of solid-state circuit breakers, it reduces the conduction time of the switching elements throughout the entire operation process, thus reducing conduction losses; compared with the high cost of hybrid DC circuit breakers and solid-state circuit breakers, the entire control process of this invention is driven by the movement of a robotic arm, and the electronic auxiliary circuit breaker does not require complex control circuits to control the switching elements in the system, reducing the cost in the early design and prototype manufacturing stages; this invention combines an embedded Cassie arc model with appropriate parameters, and verifies the effectiveness of the designed control strategy by building an electronic auxiliary circuit breaker model. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the 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.

[0031] Figure 1 This is a flowchart illustrating a control strategy design method for an electronically assisted circuit breaker according to an embodiment of the present invention.

[0032] Figure 2 This is a schematic diagram illustrating the specific process of an electronic auxiliary circuit breaker control strategy design method according to an embodiment of the present invention.

[0033] Figure 3 This is a schematic diagram of the operation timing of the electronically assisted DC circuit breaker in an embodiment of the present invention.

[0034] Figure 4 This is a schematic diagram of a mechanical switch model based on the Cassie arc model in an embodiment of the present invention.

[0035] Figure 5 This is a simulated fault current and arc voltage waveform diagram based on the Cassie arc model in an embodiment of the present invention.

[0036] Figure 6 This is a schematic diagram of the MATLAB model of the electronic auxiliary circuit breaker in an embodiment of the present invention.

[0037] Figure 7 This is a current and voltage waveform diagram of an electronic auxiliary circuit breaker with an opening time of 1.0ms in an embodiment of the present invention. Detailed Implementation

[0038] The following description of the embodiments is taken with reference to the accompanying drawings, which illustrate specific embodiments in which the invention can be implemented.

[0039] Traditional hybrid DC circuit breakers require a fault current detection method, such as detecting the rate of change of current, which is a relatively complex system with high accuracy requirements; otherwise, the circuit breaker may fail to interrupt the fault.

[0040] Based on this, please refer to Figure 1 As shown, Embodiment 1 of the present invention provides a method for designing an electronic auxiliary circuit breaker control strategy, comprising:

[0041] Step S1: When the line current is detected to rise above the maximum load current, the robotic arm starts to move under the control of a mechanical switch.

[0042] In step S2, the robotic arm activates the electronic auxiliary circuit breaker by pulling an arc and using the arc voltage after waiting for a set time, thus opening the power electronic converter branch.

[0043] Step S3: After the fault current is switched to the power electronic converter branch and the arc stress on the main contact is relieved, wait for a set time to shut down the power electronic converter branch and release the residual electromagnetic energy through the varistor branch.

[0044] In step S4, as the robotic arm moves, the mechanical switch on the robotic arm closes as the main contacts open, providing electrical isolation to the electronic circuit under zero current conditions.

[0045] Specifically, please combine Figures 2-7 As shown in this embodiment, when the line current is detected to rise above the maximum load current, the robotic arm begins to move and simultaneously activates the entire electronic auxiliary circuit breaker system by arcing, utilizing the arc voltage after a set waiting time, thus opening the power electronic converter branch (i.e., the transfer branch). Therefore, the control process of the electronic auxiliary circuit breaker is simpler than that of a traditional hybrid DC circuit breaker. The entire control process is driven by the movement of the robotic arm, closing the transfer branch after a set waiting time, while the MOV branch releases energy. This is also a difference from traditional hybrid DC circuit breakers; the electronic auxiliary circuit breaker does not require complex control circuits to control the switching elements in the system. This reduces effort and cost in the early design and prototype manufacturing stages.

[0046] Figure 3 The operating timing sequence of the electronically assisted DC circuit breaker in response to fault conditions is shown:

[0047] The main contact switch initially conducts the load current, the micro switch opens to ensure that there is no signal in the control circuit, the isolating switch closes, and the electronic path is completely inactive.

[0048] When a short-circuit fault occurs at time t1, the fault current rises rapidly through the main contacts. At this point, the mechanical switch begins to withstand the fault current. The mechanical arm of the mechanical switch remains stationary until the fault current reaches a certain level.

[0049] The fault current increases rapidly until time t2, reaching the threshold of the electromagnet or spring mechanism of the mechanical switch. The mechanical arm of the mechanical switch begins to move, opening the main contacts and generating an electric arc in the contact gap. At this time, the fault current still flows in the load branch. The arc voltage generated in the contact gap can provide power to the self-powered circuit, thereby activating the entire electronic path. However, the power electronic commutation branch is not open at this time, and the fault current reaches its peak at time t3 with the movement of the mechanical arm and then begins to decrease.

[0050] After the fault current begins to decrease, wait for the switching element to turn on.

[0051] At time t4, the microswitch on the same robotic arm as the main contact closes and sends a signal to the control and drive circuits.

[0052] The delay time from t2 to t4 is determined by the mechanical design and the movement speed of the robotic arm pulled by the spring mechanism. Although this time is not as precise as a timer made of electronic components, its stability and repeatability can be maintained at a good level due to the stability of the mechanical structure.

[0053] After the microswitch sends a signal to the control and drive circuit, there is a very short delay before the MOSFET turns on, the fault current is switched from the load DC to the power electronic commutation branch, and the arc stress on the main contacts is relieved.

[0054] Then, the control and timing circuitry will send a shutdown signal for a predetermined very short duration. The MOSFET turns off after t5, and the power electronic commutation branch shuts down.

[0055] The varistor MOV absorbs residual electromagnetic energy in the electrical system between t5 and t6.

[0056] Finally, as the robotic arm moves, the disconnect switch on the robotic arm closes along with the opening of the main contacts, providing electrical isolation to the electronic circuit under zero current conditions at t7.

[0057] The total fault current interruption time from t2 to t7 mainly includes contact separation time and MOV energy dissipation time. The conduction time of the switching elements accounts for only a very low proportion of the entire operation and can be basically ignored.

[0058] For example Figure 4 As shown, the mechanical switching part of the electronically assisted DC circuit breaker adopts a mechanical switching model based on the Cassie arc model.

[0059] The Cassie arc model constructs a model using arc voltage, open-circuit voltage across the arc, arc time constant, and arc conductance. The arc time constant is actually not a constant; this embodiment uses a typical value. The Cassie arc model is suitable for high-current, low-resistance arc scenarios, and is often used in AC systems to describe the current before it crosses zero. For DC systems, the Cassie arc model can more accurately describe the arc characteristics of DC circuits (DC systems have lower resistance). The Cassie arc model was used in the MATLAB Simulink simulation, and it is represented as follows:

[0060]

[0061] Where g is the conductivity of the electric arc, τ is the time constant of the electric arc (independent of the system's time constant), and U C It is the open-circuit voltage, and u is the arc voltage.

[0062] like Figure 5 As shown, the simulation results of the Cassie arc model are basically consistent with the actual waveforms of the fault current and arc voltage simulation results of the Cassie arc model.

[0063] like Figure 6 As shown, this embodiment further constructs a complete Simulink model of the electronic auxiliary circuit breaker. This model combines an embedded Cassie arc model with appropriate parameters, namely the mechanical switch part, loop inductance and resistance, system voltage and current, MOV parameters, and mechanical circuit breaker parameters. A MOSFET device with a withstand voltage of 600V and a rated current of 140A is used. The MOSFET turn-on time is set to 1.0ms, the conduction time to 100μs, the buffer capacitor to 1μF, and the MOV clamping voltage to 1000V, which is set to approximately 1.5 times the system voltage.

[0064] Figure 7 The current and voltage waveforms of the electronic auxiliary circuit breaker are shown when the MOSFET is turned on at 1.0ms. As the MOSFET turns on, the fault current is transferred to the power electronic branch. After the MOSFET turns off, the fault current begins to decrease to zero. During this period, the MOV branch releases energy.

[0065] This embodiment designs and analyzes the control strategy of an electronically auxiliary circuit breaker, combining mechanical switches and power electronic circuits. A basic scheme for the electronically auxiliary circuit breaker is presented, and a simulation model is implemented based on SIMULINK. The simulation model successfully simulates the opening and closing of the mechanical switch. Based on this, a model of the electronically auxiliary circuit breaker is designed, thus verifying the feasibility of the circuit topology and control.

[0066] Corresponding to the electronic auxiliary circuit breaker control strategy design method provided in Embodiment 1 of the present invention, Embodiment 2 of the present invention provides an electronic auxiliary circuit breaker control strategy design device, comprising:

[0067] The initial control module is used to initiate movement of the robotic arm under the control of a mechanical switch when the line current is detected to rise above the maximum load current.

[0068] The converter branch activation module is used by the robotic arm to activate the electronic auxiliary circuit breaker by pulling an arc and using the arc voltage after waiting for a set time, thereby opening the power electronic converter branch.

[0069] The commutator branch shutdown module is used to shut down the power electronic commutator branch after the arc stress on the main contacts is relieved when the fault current is switched to the power electronic commutator branch, and the residual electromagnetic energy is released by the varistor branch.

[0070] An isolation module is used to provide electrical isolation to electronic circuits under zero-current conditions when the mechanical switches on the robotic arm close as the main contacts open during the movement of the robotic arm.

[0071] Furthermore, the device also includes a model building module for building a Simulink model of an electronic auxiliary circuit breaker, wherein the Simulink model of the electronic auxiliary circuit breaker combines the mechanical switching part based on the Cassie arc model, the loop inductance and resistance, the system voltage and current, the varistor parameters, and the mechanical circuit breaker parameters.

[0072] For the working principle and process of this embodiment, please refer to the description of the aforementioned Embodiment 1 of the present invention, which will not be repeated here.

[0073] As can be seen from the above description, compared with the prior art, the beneficial effects of the present invention are as follows: The present invention can accurately simulate the breaking process of the electronic auxiliary circuit breaker when a low-voltage DC system fault occurs, providing a reference for the construction of related systems and the research and development and configuration of related protection devices; compared with the complex structural design and commutation process of hybrid DC circuit breakers, the present invention optimizes the timing control process, and compared with the relatively high conduction loss of solid-state circuit breakers, it reduces the conduction time of the switching elements in the entire operation process, thus reducing conduction loss; compared with the high cost of hybrid DC circuit breakers and solid-state circuit breakers, the entire control process of the present invention is based on the movement of the robotic arm, and the electronic auxiliary circuit breaker does not require complex control circuits to control the switching elements in the system, reducing the cost in the early design and prototype manufacturing; the present invention combines an embedded Cassie arc model with appropriate parameters, and verifies the effectiveness of the designed control strategy by building an electronic auxiliary circuit breaker model.

[0074] The above description is merely a preferred embodiment of the present invention and should not be construed as limiting the scope of the invention. Therefore, any equivalent variations made in accordance with the claims of the present invention are still within the scope of the present invention.

Claims

1. A design method for an electronic auxiliary circuit breaker control strategy, characterized in that... ,include: Step S1: When the line current is detected to rise above the maximum load current, the robotic arm begins to move under the control of a mechanical switch; wherein, when a short circuit fault occurs... t At moment 1, the fault current rises rapidly through the main contacts, and the mechanical switch begins to withstand the fault current; the fault current increases rapidly until... t At time 2, when the current threshold that triggers the electromagnet or spring mechanism of the mechanical switch is reached, the mechanical arm of the mechanical switch begins to move, the main contacts are opened, and an electric arc is generated in the contact gap. In step S2, the robotic arm activates the electronic auxiliary circuit breaker by pulling an arc and using the arc voltage after waiting for a set time, thus opening the power electronic converter branch. Step S3: After the fault current is switched to the power electronic converter branch and the arc stress on the main contact is relieved, wait for a set time to shut down the power electronic converter branch and release the residual electromagnetic energy through the varistor branch. In step S4, as the robotic arm moves, the disconnect switch on the robotic arm closes as the main contacts open, providing electrical isolation for the electronic circuit under zero current conditions.

2. The method according to claim 1, characterized in that, Step S2 specifically includes: The fault current moves with the movement of the robotic arm. t It reaches its peak at time 3 and then begins to decline; exist t At time 4, the microswitch on the same robotic arm as the main contact closes and sends a signal to the control and drive circuits, whereby... t 2 to t The delay time of 4 is determined by the mechanical design and the moving speed of the robotic arm pulled by the spring mechanism; When the MOSFET is turned on, the fault current is switched from the load DC to the power electronic commutator branch.

3. The method according to claim 2, characterized in that, Step S3 specifically includes: the control and timing circuit will send a shutdown signal after waiting for a set time, and the MOSFET will... t At time 5, the power electronic converter branch is shut down; the varistor is... t 5 and t It absorbs residual electromagnetic energy in the electrical system between 6.

4. The method according to claim 1, characterized in that, The mechanical switching part of the electronically assisted DC circuit breaker adopts a mechanical switching model based on the Cassie arc model. The Cassie arc model is constructed by arc voltage, open circuit voltage at both ends of the arc, arc time constant, and arc conductance.

5. The method according to claim 4, characterized in that, Also includes: A Simulink model of an electronic auxiliary circuit breaker was constructed, which combined the mechanical switching part based on the Cassie arc model, loop inductance and resistance, system voltage and current, varistor parameters, and mechanical circuit breaker parameters.

6. The method according to claim 5, characterized in that, The Simulink model of the electronic auxiliary circuit breaker uses a MOSFET device with a withstand voltage of 600V and a rated current of 140A. The MOSFET turn-on time is set to 1.0ms, the conduction time is set to 100μs, the buffer capacitor is 1μF, and the varistor clamping voltage is selected to be 1000V.

7. The method according to claim 6, characterized in that, As the MOSFET turns on, the fault current is transferred to the power electronic commutation branch. After the MOSFET turns off, the period during which the fault current begins to decrease to zero is during which the energy is released by the varistor branch.

8. A device for designing control strategies for electronic auxiliary circuit breakers, characterized in that... ,include: The initial control module is used to initiate movement of the robotic arm under the control of a mechanical switch when a line current rises above the maximum load current; specifically, when a short-circuit fault occurs... t At moment 1, the fault current rises rapidly through the main contacts, and the mechanical switch begins to withstand the fault current; the fault current increases rapidly until... t At time 2, when the current threshold that triggers the electromagnet or spring mechanism of the mechanical switch is reached, the mechanical arm of the mechanical switch begins to move, the main contacts are opened, and an electric arc is generated in the contact gap. The converter branch activation module is used by the robotic arm to activate the electronic auxiliary circuit breaker by pulling an arc and using the arc voltage after waiting for a set time, thereby opening the power electronic converter branch. The commutator branch shutdown module is used to shut down the power electronic commutator branch after the arc stress on the main contacts is relieved when the fault current is switched to the power electronic commutator branch, and the residual electromagnetic energy is released by the varistor branch. An isolation module is used to provide electrical isolation to electronic circuits under zero-current conditions, as the isolating switch on the robotic arm closes along with the opening of the main contacts as the robotic arm moves.

9. The apparatus according to claim 8, characterized in that, Also includes: The model building module is used to build a Simulink model of an electronic auxiliary circuit breaker. The Simulink model of the electronic auxiliary circuit breaker combines the mechanical switch part based on the Cassie arc model, the loop inductance and resistance, the system voltage and current, the varistor parameters, and the mechanical circuit breaker parameters.

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