RL load protection and control system with fast cut-off function

Abstract

This invention discloses an RL load protection and control system with rapid disconnection function, relating to the field of electronic equipment testing technology. It includes: a resistive load module: performing rapid disconnection of inductive loads through multiple parallel resistive branches; an inductive load module connected to the resistive load module: performing switching of inductive loads through multiple parallel inductive branches; and a control module electrically connected to the resistive and inductive load modules: regulating the operating status of the resistive and inductive load modules according to the operating mode. When the rapid disconnection mode is triggered, this invention immediately stops sending trigger pulses, and the solid-state electronic switch, based on the characteristics of AC current, automatically turns off when the current first crosses zero. This priority turn-off of the solid-state electronic switch reduces the impact of fault current on power devices within the system and the risk of thermal damage.

Description

Technical Field

[0001] This invention relates to the field of electronic equipment testing technology, specifically to an RL load protection and control system with a rapid disconnection function. Background Technology

[0002] Inductive loads (RL loads) are widely used in modern industrial automation, power electronics systems, motor drives, rail transportation, and new energy power generation. Typical RL loads include AC / DC motors, solenoid valves, relay coils, transformers, and reactors. These loads not only have a resistive component during operation but also exhibit significant inductive characteristics. Their current changes lag behind voltage changes, resulting in complex dynamic response behavior.

[0003] In actual operation, RL loads are susceptible to external short circuits, overloads, power fluctuations, or abnormal control signals, leading to a sharp rise in current and causing overcurrent or even short-circuit current. Because inductors impede changes in current, the current cannot change abruptly at the moment of a fault, but it will subsequently increase rapidly and may exceed the rated capacity of the equipment. If the circuit is not disconnected in time, it will lead to overheating and damage to power devices (such as IGBTs and MOSFETs), aging of insulation materials, system malfunction, and may even cause safety accidents such as fires.

[0004] Chinese invention patent CN114172129A discloses a hybrid device solid-state circuit breaker and control method capable of bidirectional interruption and soft starting. The method includes: both the semi-controlled device group and the fully controlled device in the main current-carrying branch are conducting, ensuring steady-state current flow in the system; in the event of a fault, the corresponding fully controlled device is shut down, and after reaching the surge arrester's operating voltage, the surge arrester is connected to the system, the converter branch is turned on, the fault current is transferred to the converter branch, the semi-controlled device group is turned off, and then the converter branch is turned off again, the fault current is transferred to the energy-absorbing branch for energy absorption until the DC circuit breaker safely disconnects; when a capacitive load is connected, after the semi-controlled device group is turned off, the corresponding switch in the converter branch is switched on and off at high frequency, and the inrush current switches between the converter branch and the energy-absorbing branch until soft starting is successful. This invention features low loss, fast interruption, simple structure, multiple integrated functions, and high safety.

[0005] However, the above and similar technical solutions still have the following shortcomings: In traditional RL load control systems, contactors are mostly used as the core switching elements. Their inherent mechanical action characteristics will cause significant delays in the disconnection and engagement processes. This slow response problem makes it difficult to meet the application scenarios with strict requirements for rapid disconnection, thus limiting the performance improvement of the system in terms of high efficiency and high reliability control. Summary of the Invention

[0006] The purpose of this invention is to provide an RL load protection and control system with a rapid disconnection function to solve the problems mentioned in the background art.

[0007] To achieve the above objectives, the present invention provides the following technical solution: an RL load protection and control system with rapid disconnection function, comprising: Resistive load module: It quickly disconnects inductive loads through multiple parallel resistor branches; The inductive load module, in conjunction with the resistive load module, switches the inductive load through multiple parallel inductive branches. The control module, which is electrically connected to the resistive load module and the inductive load module, regulates the operating state of the resistive load module and the inductive load module according to the operating mode.

[0008] Furthermore, the resistive load module includes multiple resistive branches, which are connected in parallel with each other. Each resistive branch includes a power resistor, a solid-state electronic switch, and a current transformer, and the power resistor, solid-state electronic switch, and current transformer are electrically connected to each other.

[0009] Furthermore, the resistive load module includes a first main circuit and a switching control unit, with the first main circuit electrically connected to the switching control unit. The first main circuit includes a first input terminal, a main switch, a current transformer, and a power resistor. The first input terminal is electrically connected to the current transformer through the main switch, the current transformer is electrically connected to the switching control unit, and the switching control unit is electrically connected to the power resistor.

[0010] Furthermore, the resistance value of the power resistor is set by binary weights, and the power resistor is provided with heat dissipation fins. In addition, there are multiple power resistors, and each power resistor is electrically connected to a thyristor.

[0011] Furthermore, the solid-state electronic switch includes a control rectifier and a drive component. The drive component interacts with the control module through a communication module, and is electrically connected to the control rectifier.

[0012] Furthermore, the inductive load module includes multiple inductive branches, which are connected in parallel with each other. Each inductive branch includes an energy storage element and a mechanical contactor, and the energy storage element is electrically connected to the mechanical contactor.

[0013] Furthermore, the inductive load module includes a second main circuit, a switching control unit, and a reactor load. The second main circuit includes a second input terminal and a controller. The second input terminal is electrically connected to the first input terminal through the switching control unit and the reactor load.

[0014] Furthermore, the mechanical contactor includes an electromagnetic coil and a DC relay, the electromagnetic coil being electrically connected to the DC relay, and the DC relay interacting with the control module via a communication module.

[0015] Furthermore, the operating modes include a normal operating mode and a rapid cut-off mode. In the normal operating mode, load adjustment is performed according to the set target power value, including: SA1: Determine the target current: Based on the set target power value and the current system line voltage, determine the corresponding total current; SA2: Determine branch combination: Combine the total current with the power-branch combination mapping table to determine the corresponding branch combination; SA3: Switching Operation: Based on the address mapping table in the control module, the corresponding turn-on command is determined, and a pulse signal is sent to the resistive load module and the inductive load module through the drive unit of the control module to turn on the resistive branch and the inductive branch.

[0016] Furthermore, based on the comparison result between the sensor data signal acquired by the signal acquisition unit in the control module and the preset safety threshold, a rapid cutoff mode is triggered to perform rapid cutoff, including: SB1: Rapid cut-off: The control module stops sending trigger pulse commands to the resistive load module, and at the same time, when the current crosses zero for the first time, the solid-state electronic switch that is conducting is automatically turned off; SB2: Load cut-off: After one countdown of the timer in the control module, the electromagnetic coil is de-energized and the mechanical contactor is turned off; SB3: Final Isolation: The main contactor in the resistive load module is disconnected by the second timing of the timer in the control module, and the second timing is longer than the first timing.

[0017] Compared with the prior art, the beneficial effects of the present invention are: Firstly, when the fast cut-off mode is triggered, the present invention will immediately stop sending trigger pulses. At the same time, the solid-state electronic switch will automatically turn off when the current crosses zero for the first time, based on the characteristics of AC current. Thus, by prioritizing the turn-off of the solid-state electronic switch, the impact of fault current on power devices in the system and the risk of thermal damage can be reduced. Secondly, this invention sets the current or reactive power values ​​of the resistive and inductive branches according to binary weights, thereby enabling precise control of the load power. At the same time, a large number of closely spaced equivalent load values ​​can be generated through a limited number of branch combinations. Thirdly, when the rapid disconnection mode is triggered, the present invention prioritizes shutting down the solid-state electronic switch, then shuts down the mechanical contactor, and finally shuts down the main contactor. This phased and coordinated shutdown protection mechanism not only ensures the speed of disconnection, but also achieves complete physical isolation between the load and the front-end power supply by finally disconnecting the main contactor, eliminating the risk of residual current and improving the safety level of the entire system. Attached Figure Description

[0018] Figure 1 This is a system block diagram of the RL load protection and control system in this invention; Figure 2 This is a system block diagram of the resistor branch in this invention; Figure 3 This is a system block diagram of the inductive load module in this invention; Figure 4 This is a system block diagram of the resistive load module in this invention; Figure 5 This is a circuit diagram of the resistive load module in this invention; Figure 6 This is another system block diagram of the inductive load module in this invention; Figure 7 This is a circuit diagram of the inductive load module in this invention. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only 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.

[0020] In traditional RL load control systems, contactors are mostly used as the core switching element. Their inherent mechanical characteristics result in significant delays in the opening and closing processes. This slow response makes it difficult to meet the requirements of applications demanding rapid disconnection, thus limiting the system's performance improvement in terms of high efficiency and high reliability control. The technical solution of this application achieves rapid disconnection of inductive loads through multiple parallel resistive branches and switches inductive loads through multiple parallel inductive branches. Furthermore, it adjusts the specific operating status of each module in real time according to the system's operating mode. This allows for load adjustment based on a set target power value during normal operation. Upon detecting faults such as overcurrent, it can immediately switch to a rapid disconnection mode. This not only improves the disconnection speed but also enhances the flexibility and accuracy of load adjustment through the design of binary weighted branches.

[0021] Example 1 refer to Figures 1-3 This embodiment provides an RL load protection and control system with rapid disconnection function. The RL load protection and control system includes a resistive load module, an inductive load module, and a control module. The resistive load module uses multiple parallel resistive branches to rapidly disconnect inductive loads. The inductive load module uses multiple parallel inductive branches to switch inductive loads. The control module is electrically connected to the resistive and inductive load modules. During operation, the control module has two operating modes: a normal operating mode and a rapid disconnection mode. Based on the current operating mode, the control module adjusts the operating status of the resistive and inductive load modules in real time.

[0022] In this embodiment, the resistive load module includes multiple resistive branches, all of which are connected in parallel. Each resistive branch includes a power resistor, a solid-state electronic switch, and a current transformer, all of which are electrically connected. Notably, in this embodiment, the current values ​​of the multiple resistive branches are set using binary weights. In practice, the current value of the first resistive branch is set to 5A, the current value of the second resistive branch to 10A, the current value of the third resistive branch to 20A, and so on, thus setting the current value of each resistive branch.

[0023] Furthermore, in this embodiment, the power resistor is set as a high-power wire-wound resistor or alloy resistor, which is equipped with heat dissipation fins and installed inside a cabinet equipped with a forced air cooling fan, so as to consume electrical energy and convert it into heat for safe heat dissipation.

[0024] Furthermore, in this embodiment, the solid-state electronic switch is configured as a controlled rectifier, i.e., a thyristor, which can specifically control its conduction state according to the control commands sent by the control module. Specifically, the solid-state electronic switch is mounted on a heat sink and is equipped with a corresponding drive component, which controls the operation of the solid-state electronic switch. Simultaneously, the drive component and the control module interact via a communication module; the drive component receives weak electrical signals sent by the control module and drives the solid-state electronic switch. In practice, after the control module sends a trigger pulse signal to the drive component, the drive component turns on the solid-state electronic switch. Simultaneously, when the AC current naturally drops to zero at the zero-crossing point, the drive component automatically turns off the solid-state electronic switch. It is worth noting that when forcibly and rapidly turning off the solid-state electronic switch at a non-zero-crossing point, the control module can send a turn-off signal to the drive component, which then turns off the solid-state electronic switch.

[0025] Furthermore, in this embodiment, the current transformer is used to monitor the total current of each resistive branch, and the current transformer and the control module exchange information through a communication module. That is, the current transformer sends the acquired total monitored current to the control module, and the control module compares the received total monitored current with a preset current threshold (which can be specifically set according to actual data requirements, so it is not specifically described in this embodiment), and determines the corresponding operating state based on the comparison result, thereby facilitating the control of the solid-state electronic switch's operating state according to the determined operating state.

[0026] In this embodiment, the inductive load module includes multiple inductive branches, all of which are connected in parallel. Each inductive branch includes an energy storage element and a mechanical contactor, and the energy storage element and the mechanical contactor are electrically connected. Specifically, in this embodiment, the energy storage element is a power inductor, and the power inductor has a heat dissipation channel to provide inductive reactance.

[0027] Furthermore, in this embodiment, the mechanical contactor is configured as a switching actuator, wherein each switching actuator contains an electromagnetic coil, and the electromagnetic coil is electrically connected to a DC relay. Simultaneously, the DC relay and the control module exchange information via a communication module. In other words, the DC relay, according to the operating instructions of the control module, regulates the energization and de-energization of the electromagnetic coil, thereby realizing the control of a high-voltage AC circuit by a low-voltage DC weak current signal.

[0028] In this embodiment, the control module is configured as a microprocessor control board, including a signal acquisition unit and a drive unit. The signal acquisition unit and the drive unit are electrically connected, and the signal acquisition unit is electrically connected to the drive assembly, current transformer, and DC relay. The drive unit is electrically connected to a solid-state electronic switch and a mechanical contactor.

[0029] Furthermore, in this embodiment, the control module's operating modes include a normal operating mode and a fast cut-off mode. The normal operating mode is used in non-fault mode to independently control the switching of resistive and inductive load modules for load regulation. The fast cut-off mode is used in fault mode to respond to fast cut-off commands by prioritizing the shutdown of solid-state electronic switches in all resistive load modules, achieving a rapid cut-off response.

[0030] Specifically, in normal operating mode, the load is adjusted according to the set target power value, as follows: Step SA1: Determine the target current. This involves the operator setting the target power value via the control panel and transmitting this value to the signal acquisition unit of the control module through the communication module. Simultaneously, based on the set target power value and the current system line voltage, the corresponding total current is determined, specifically as follows:

[0031] in: The total current on each phase bus. This refers to the total active power of the three phases. This represents the current system line voltage.

[0032] In the specific implementation process, the current system line voltage is 400V, and the total active power of the three phases, i.e. the target power value, is set to 150kW. Then, the total current on each phase bus is approximately 216.5A.

[0033] Step SA2: Determine the branch combination. That is, based on the total current on each phase bus determined in step SA1, it is combined with the preset "power-branch combination" mapping table to determine the corresponding branch combination from the "power-branch combination" mapping table.

[0034] Furthermore, in this embodiment, the branch combination is configured by setting the corresponding current value using binary weights. In other words, by combining a limited number of branches, different and closely spaced current values ​​can be generated, thereby achieving a "stepless" adjustment effect.

[0035] Step SA3: Switching Operation. This involves determining the corresponding turn-on command based on the address mapping table set in the control module. Simultaneously, based on the determined turn-on command, the drive unit sends pulse signals to the resistive load module and the inductive load module. The resistive and inductive load modules then turn on their corresponding resistive and inductive branches according to the received pulse signals, thereby ensuring three-phase load balance.

[0036] Furthermore, based on the sensor data signals acquired by the signal acquisition unit, such as current and voltage signals, the acquired sensor data signals are compared with a preset safety threshold (which can be specifically set according to actual data requirements, and therefore is not specifically described in this embodiment). When the acquired sensor data signal is greater than the preset safety threshold, a fast cut-off mode is triggered to perform a rapid cut-off. Specifically, as follows: Step SB1: Rapid Cut-off. This means the control module stops sending trigger pulse commands to the resistive load module. In other words, the solid-state electronic switch in the resistive branch will not receive trigger pulse signals from the control module. Specifically, without trigger pulse signals, the gate driver board of the solid-state electronic switch will not be able to drive it to conduct. Therefore, based on the characteristics of alternating current, the currently conducting solid-state electronic switch will automatically turn off when the current first crosses zero.

[0037] Step SB2: Load Disconnection. This involves disconnecting the mechanical contactor in the inductive load module according to the timer set within the control module. Specifically, when the trigger pulse signal cannot be sent, the timer set within the control module will start counting for one cycle. After the timer finishes counting, the control module will de-energize the electromagnetic coil, thereby turning off the mechanical contactor.

[0038] Step SB3: Final Isolation. This involves resetting the timing interval after the mechanical contactor is turned off, using a timer set within the control module. It's important to note that the timing interval set in Step SB3 (Final Isolation) is longer than the timing interval set in Step SB2 (Load Disconnection). Simultaneously, after the set timing interval expires, the main contactor in the resistive load module is disconnected, thus achieving complete physical isolation between the entire load cabinet (resistive and inductive load modules) and the front-end power supply.

[0039] Example 2 This embodiment provides an RL load protection and control system with rapid disconnection function. Its specific implementation method is the same as in Embodiment 1, except that, as referred to... Figure 4 and Figure 5In this embodiment, the resistive load module includes a first main circuit and a switching control unit, which are electrically connected. Specifically, the first main circuit includes a first input terminal, a main switch, current transformers, and a power resistor. The first input terminal includes input terminal A, input terminal B, input terminal C, and input terminal N, which is a three-phase four-wire power input, providing a three-phase 380V or single-phase 220V test voltage for the device. The main switch is set as switch KM0, and the current transformers include current transformers CT1, CT2, and CT3. Current transformer CT1 is electrically connected to input terminal A, current transformer CT2 is electrically connected to input terminal B, and current transformer CT3 is electrically connected to input terminal C. That is, the real-time current of the three phases at input terminals A, B, and C is detected by the current transformers CT1, CT2, and CT3, respectively.

[0040] Furthermore, in this embodiment, multiple power resistors are provided, and eight power resistors are electrically connected to each of input terminals A, B, and C, with the eight power resistors connected in parallel. Simultaneously, the switching control unit in this embodiment includes multiple thyristors, with each power resistor and thyristor corresponding to and electrically connected to the others.

[0041] Furthermore, in this embodiment, the three-phase currents at input terminals A, B, C, and N are transmitted to each phase load unit via the main switch KM0, current transformers CT1, CT2, and CT3, respectively. When the control module sends a trigger pulse signal, the thyristors in the corresponding load unit will be turned on, and the current of that phase load unit will be loaded into the corresponding power resistor through the current transformers and the turned-on thyristors, thereby allowing electrical energy to be consumed by the power resistor in the form of heat.

[0042] Example 3 This embodiment provides an RL load protection and control system with rapid disconnection function. Its specific implementation method is the same as in Embodiment 1, except that, as referred to... Figure 6 and Figure 7 In this embodiment, the inductive load module includes a second main circuit, a switching control unit, and a reactor load, wherein the second main circuit, the switching control unit, and the reactor load are electrically connected to each other. Specifically, in this embodiment, the second main circuit includes a second input terminal and a controller, the switching control unit includes multiple switching elements, and the reactor load includes multiple reactors.

[0043] In this embodiment, the second input terminal includes input terminal A1, input terminal B1, input terminal C1 and input terminal N1, which are three-phase four-wire control signals or power inputs, and are electrically connected to the first input terminals of the first main circuit, namely input terminal A, input terminal B, input terminal C and input terminal N, respectively. In other words, the inductive load module and the resistive load module are used together to provide a variable power factor load.

[0044] Furthermore, in this embodiment, the controller, switching elements, and reactors are arranged in a one-to-one correspondence and are electrically connected to each other. Specifically, the controller in this embodiment has multiple control contacts, including contacts K1, G1, K2, and G2. It is worth noting that this embodiment also includes a controller with contacts G1 and G2. Meanwhile, this embodiment has multiple reactors, and the reactive power values ​​between the reactors are set using binary weights. It is noteworthy that the reactive power values ​​between the reactors in this embodiment have an approximately binary weight relationship, so that fine-step adjustment of reactive power can be achieved through different combinations.

[0045] Furthermore, in this embodiment, the control module transmits signals to the coil of the switching element via the controller's control contacts. That is, after the operator sets the target power value through the control panel, the control module determines the corresponding reactor combination to be connected based on the set target power value. Thus, by closing the control contacts, the coil of the switching element is energized and attracted, connecting the corresponding switching element. Simultaneously, after the coil of the switching element is energized and attracted, its corresponding normally open main contact closes, allowing the current at the corresponding second input terminal to flow through the closed normally open main contact and be applied to the corresponding reactor. In other words, when the current flows through the corresponding reactor, a hysteresis magnetic field is generated, thereby consuming reactive power. Simultaneously, the current converges at the first input terminal.

[0046] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended embodiments and their equivalents.

Claims

1. An RL load protection and control system with rapid disconnection function, characterized in that, Including: Resistive load module: It quickly disconnects inductive loads through multiple parallel resistor branches; The inductive load module, in conjunction with the resistive load module, switches the inductive load through multiple parallel inductive branches. The control module, which is electrically connected to the resistive load module and the inductive load module, regulates the operating state of the resistive load module and the inductive load module according to the operating mode.

2. The RL load protection and control system with rapid disconnection function according to claim 1, characterized in that, The resistive load module includes multiple resistive branches, which are connected in parallel. Each resistive branch includes a power resistor, a solid-state electronic switch, and a current transformer, and the power resistor, solid-state electronic switch, and current transformer are electrically connected to each other.

3. The RL load protection and control system with rapid disconnection function according to claim 1, characterized in that, The resistive load module includes a first main circuit and a switching control unit. The first main circuit is electrically connected to the switching control unit. The first main circuit includes a first input terminal, a main switch, a current transformer, and a power resistor. The first input terminal is electrically connected to the current transformer through the main switch. The current transformer is electrically connected to the switching control unit. The switching control unit is electrically connected to the power resistor.

4. A load protection and control system with rapid disconnection function according to claim 2 or 3, characterized in that, The resistance value of the power resistor is set by binary weights, and the power resistor is provided with heat dissipation fins. There are multiple power resistors, and each power resistor is electrically connected to a thyristor.

5. The RL load protection and control system with rapid disconnection function according to claim 2, characterized in that, The solid-state electronic switch includes a control rectifier and a drive component. The drive component interacts with the control module through a communication module, and is also electrically connected to the control rectifier.

6. The RL load protection and control system with rapid disconnection function according to claim 1, characterized in that, The inductive load module includes multiple inductive branches, which are connected in parallel. Each inductive branch includes an energy storage element and a mechanical contactor, and the energy storage element is electrically connected to the mechanical contactor.

7. The RL load protection and control system with rapid disconnection function according to claim 1, characterized in that, The inductive load module includes a second main circuit, a switching control unit, and a reactor load. The second main circuit includes a second input terminal and a controller. The second input terminal is electrically connected to the first input terminal through the switching control unit and the reactor load.

8. The RL load protection and control system with rapid disconnection function according to claim 6, characterized in that, The mechanical contactor includes an electromagnetic coil and a DC relay. The electromagnetic coil is electrically connected to the DC relay, and the DC relay interacts with the control module through a communication module.

9. The RL load protection and control system with rapid disconnection function according to claim 1, characterized in that, The operating modes include a normal operating mode and a rapid cut-off mode. In the normal operating mode, load adjustment is performed according to the set target power value, including: SA1: Determine the target current: Based on the set target power value and the current system line voltage, determine the corresponding total current; SA2: Determine branch combination: Combine the total current with the power-branch combination mapping table to determine the corresponding branch combination; SA3: Switching Operation: Based on the address mapping table in the control module, the corresponding turn-on command is determined, and a pulse signal is sent to the resistive load module and the inductive load module through the drive unit of the control module to turn on the resistive branch and the inductive branch.

10. The RL load protection and control system with rapid disconnection function according to claim 9, characterized in that, Based on the comparison result between the sensor data signal acquired by the signal acquisition unit in the control module and the preset safety threshold, a fast cut-off mode is triggered to perform a fast cut-off, including: SB1: Rapid cut-off: The control module stops sending trigger pulse commands to the resistive load module, and at the same time, when the current crosses zero for the first time, the solid-state electronic switch that is conducting is automatically turned off; SB2: Load cut-off: After one countdown of the timer in the control module, the electromagnetic coil is de-energized and the mechanical contactor is turned off; SB3: Final Isolation: The main contactor in the resistive load module is disconnected by the second timing of the timer in the control module, and the second timing is longer than the first timing.

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