Parallel multi-fracture electromagnetic switch cooperative control method

Abstract

The invention relates to a cooperative control method for parallel multi-break electromagnetic switches. The method comprises the following steps: designing a single-pole electromagnetic switch intelligent control module, and realizing signal transmission when each pole switch is switched on and switched off through an associated control module. Through a fixed-phase switching-on control strategy, load properties are detected in real time, and corresponding control strategies are formulated for switching-on inrush currents with different characteristics caused by different load properties so as to reduce contact ablation caused by bouncing arcs during switching-on. In order to improve the breaking capacity of the parallel multi-break electromagnetic switch, a cooperative breaking control strategy is adopted to improve the consistency of the opening moment.

Description

Technical Field

[0001] The invention relates to the technical field of low-voltage electrical appliances, and in particular to a coordinated control method of parallel-type multi-break electromagnetic switches. Background Art

[0002] Low-voltage electrical appliances are widely used in power control systems, rail transit, new energy vehicles, aerospace and other fields due to their low cost, high cost performance and strong overload capacity. However, single-break electromagnetic switches are restricted by multiple factors such as materials, processes, volume, structure and arc extinguishing conditions. Their current carrying capacity and breaking capacity are difficult to meet the increasing capacity of the power grid. Therefore, expanding the capacity of electromagnetic switches is a common method to increase the capacity of electromagnetic switches.

[0003] Parallel operation is a common expansion solution for electromagnetic switches. Parallel operation of multiple breaks can effectively improve the current carrying capacity of electromagnetic switches, but the electromagnetic switches currently using parallel expansion operation do not perform synchronous control operations on the on-off process, and only rely on the parallel contact structure. After long-term operation, due to contact wear and dispersion, it will inevitably lead to deviations in the opening and closing time of each pole contact system. If the synchronization of opening and closing of electromagnetic switches operating in parallel cannot be guaranteed, one of the switches will bear a rated current that is multiple of the number of expanded poles at the moment of closing, especially when the load is resistive-capacitive or resistive-inductive. A closing surge current that is several times the rated current will be generated when closing. If all these surge currents are concentrated on the same switch, the contact bounce arc under overcurrent will seriously affect the life of the electromagnetic switch, and even cause malfunction of the switch due to excessive electromagnetic repulsion of the contacts. At the moment of opening, since the impedance of each branch is extremely low, when the contact of a branch is disconnected, the arc of that branch is equivalent to a series arc, which triggers a circulating current in the parallel circuit, causing the current of that branch to be immediately transferred to the remaining branches. The current transfer process takes a very short time, which is much shorter than the time difference between the disconnection of each pole switch. The last electromagnetic switch to be disconnected will directly bear the main circuit current, resulting in the same breaking capacity of multi-break parallel operation as that of a single break. Although the current transfer time can be slowed down by connecting the compensation inductance in series with each branch, if the asynchronous time of each pole switch is too long, the main circuit current will still be completely borne by a single break. Therefore, achieving coordinated control of the electromagnetic switch is the key issue to improve the on-off capacity of parallel multi-break electromagnetic switches. Summary of the invention

[0004] In view of this, the purpose of the present invention is to provide a parallel multi-break electromagnetic switch coordinated control method, which designs an intelligent control module to perform associated control on each pole switch. A multivariable closed-loop control system with contact displacement feedback is established to improve the consistency of the opening and closing of each pole switch in parallel operation, and combined with phase-fixed closing on the basis of synchronous closing to reduce the impact of closing surge current on electrical life.

[0005] To achieve the above object, the present invention adopts the following technical solution: a parallel multi-break electromagnetic switch coordinated control method, comprising the following steps:

[0006] Step 1: Design a multi-break electromagnetic switch hardware control module;

[0007] Step 2: Design a synchronous closing control strategy for multi-break electromagnetic switches;

[0008] Step 3: Design a closing inrush current suppression strategy for parallel multi-break electromagnetic switches;

[0009] Step 4: Design a coordinated breaking control strategy for parallel multi-break electromagnetic switches.

[0010] In a preferred embodiment, the multi-break electromagnetic switch hardware control module in step 1 sets a tri-stable control circuit, including an AC power supply u AC , rectifier diode D1, rectifier filter capacitor C, first field effect tube S1, second field effect tube S2, third field effect tube S3 and fourth field effect tube S4, equivalent resistance R of the coil coil and inductor L coil ; The voltage across the rectifier filter capacitor C is u C .

[0011] In a preferred embodiment, the tri-stable control circuit includes three working states:

[0012] In the excitation state, the first field effect tube S1 and the fourth field effect tube S4 are turned on, the second field effect tube S2 and the third field effect tube S3 are turned off, and the voltage across the rectifier filter capacitor C is u C After passing through the first field effect transistor S1 and the second field effect transistor S2, it is applied to both ends of the coil, so that the coil current i coil Rapid rise, this working state is defined as mode 1;

[0013] In the demagnetization state, the first field effect tube S1 and the fourth field effect tube S4 are turned off, the second field effect tube S2 and the third field effect tube S3 are turned on, and the voltage across the rectifier filter capacitor C is u C After passing through the third field effect transistor S3 and the fourth field effect transistor S4, the coil magnetic energy is quickly released, and the filter capacitor C is reversely charged, so that the coil current i coil Rapid decline, this working state is defined as mode 2;

[0014] In the freewheeling state, the first field effect tube S1 and the second field effect tube S2 are turned off, the third field effect tube S3 and the fourth field effect tube S4 are turned on, and the voltage drop of the switch tube is ignored. The coil voltage u coil Almost zero, coil Slowly descending, this working state is defined as mode 3.

[0015] In a preferred embodiment, in step 2, the switch K1 and the switch K2 are set to be synchronously controlled, and the currents of K1 and K2 are respectively i coil(1) with i coil(2) , the contact displacements of K1 and K2 are x contact(1) With x contact(2) , at the end of interval ①, through |Δx contact | is compared with the set deviation threshold e to determine whether the current reference value needs to be adjusted in the current interval; at this time |Δx contact | is greater than e, so the current reference value of K1 is adjusted and stored in EEPROM for the next pull-in process.

[0016] In a preferred embodiment, in step 3, when the control object of the multi-break electromagnetic switch is a resistive and inductive load, at the initial moment of closing, the main circuit current is zero;

[0017] When the load of the multi-break electromagnetic switch is resistive and capacitive, the corresponding circuit differential equation is as follows:

[0018]

[0019] Among them, u c is the capacitive load voltage, U m is the power supply voltage amplitude, α is the initial phase angle of contact closing, and solving the above differential equation, the contact current expression can be obtained as follows:

[0020]

[0021] In the formula, is the power factor angle of resistive and capacitive load;

[0022] From formula (2), its transient component is:

[0023]

[0024] Unlike resistive and inductive loads, the transient component of resistive and capacitive loads is most obvious at the initial moment of closing, causing the largest inrush current. As time goes by, the exponential part of the transient component in equation (3) gradually decays, and the transient component gradually approaches zero. In order to explore the inrush current value of the resistive and capacitive load at the moment of closing, let At t=0, the ratio of the current at closing time to the current under stable operation is:

[0025]

[0026] Where, α∈[0,180°],

[0027] Analyzing formula (4), we can get that the maximum value of k increases with the power factor angle. increases with the increase of When α=90°, k reaches its maximum value. That is, the inrush current at the time of closing is small, and the maximum value is the peak value during stable operation; When the k value increases rapidly, the closing inrush current can reach hundreds of times;

[0028] From formula (2), it can be obtained that by controlling the closing phase angle, the transient component formula (3) can be made zero, thereby achieving the purpose of suppressing the closing inrush current. The corresponding closing phase angle is:

[0029]

[0030] In a preferred embodiment, step 4 specifically includes first performing synchronous control of the moment when the moving and static iron cores are just separated, and then applying a constant duty cycle or current for excitation to generate electromagnetic attraction to adjust the force on the moving iron core; by controlling the electromagnetic switch with a faster displacement change of the moving iron core, the consistency of the displacement of multiple switches is achieved.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] 1. Design a tri-stable control circuit and synchronous control module. Controlling the coil current through the tri-stable circuit can improve the dynamic response capability of the multi-break electromagnetic switch to the coil current, and provide a basis for introducing the displacement outer loop; the synchronous control module can not only process the upper and lower electrical signals of each pole switch with logic, eliminate the noise interference during the upper and lower electrical detection of each pole switch, but also process the zero-point signal of the contact voltage with logic, and eliminate the contact voltage detection error.

[0033] 2. A synchronous closing control strategy for parallel multi-break electromagnetic switches is proposed. Based on the step-down of the excitation current, this strategy adds the feedback of the contact displacement difference, adjusts the current reference value in stages, and adjusts the electromagnetic suction force by adjusting the coil current to achieve the adjustment of the contact displacement, which can improve the consistency of the contact displacement of the parallel multi-break electromagnetic switch.

[0034] 3. A parallel multi-break electromagnetic switch coordinated closing control strategy is proposed. This strategy can detect the load properties and power factor angle in real time. For resistive and capacitive loads that will generate large inrush current, a phase-fixed closing control strategy is introduced on the basis of the synchronous closing control strategy to suppress the closing inrush current; for other load types, a synchronous closing control strategy is used.

[0035] 4. A collaborative control strategy for the breaking process is proposed. This strategy realizes the synchronous control of the moment when the moving and static iron cores are just breaking through the logic communication module. On this basis, a collaborative control strategy for the moving stage of the breaking process is proposed. By applying a constant current or a constant duty cycle to the switch with a faster displacement change of the moving iron core, the consistency between the breaking moment and the displacement of the contact is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is a schematic diagram of coordinated control of electromagnetic switches in a preferred embodiment of the present invention;

[0037] Figure 2 A block diagram of the design of a parallel type multi-break electromagnetic switch control module according to a preferred embodiment of the present invention;

[0038] Figure 3 This is a waveform diagram illustrating the three-stable-state control principle of the preferred embodiment of the present invention;

[0039] Figure 4 This is a schematic diagram of the synchronous closing control principle of a preferred embodiment of the present invention;

[0040] Figure 5 This is a schematic diagram of the load detection principle of a preferred embodiment of the present invention;

[0041] Figure 6 This is a flow chart of the coordinated pull-in control strategy of the parallel multi-break electromagnetic switch according to the preferred embodiment of the present invention;

[0042] Figure 7 It is a schematic diagram of the synchronization control strategy of the rigid division moment of the dynamic and static cores in the preferred embodiment of the present invention;

[0043] Figure 8 It is a schematic diagram of the collaborative control strategy of the motion phase of the disconnection process of the preferred embodiment of the present invention. DETAILED DESCRIPTION

[0044] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0045] It should be noted that the following detailed descriptions are illustrative and are intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present application belongs.

[0046] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application; as used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or their combinations.

[0047] The present invention proposes a parallel multi-break electromagnetic switch coordinated control method, referring to Figure 1-8 The method designs an intelligent control module to control the switches of each pole in a linked manner. A multivariable closed-loop control system with contact displacement feedback is established to improve the consistency of the opening and closing of the switches of each pole in parallel operation, and combines phase-fixed closing with synchronous closing to reduce the impact of closing inrush current on electrical life.

[0048] The following are the specific implementation steps of the present invention:

[0049] (1) Design a hardware control module for multi-break electromagnetic switches. This control module sets up a three-stable control circuit for the single-pole electromagnetic switch to improve the dynamic response rate of the coil current to adapt to the control accuracy of the coordinated control, and eliminates the power-on and power-off errors of each pole switch caused by sampling noise through the synchronous control module. Figure 2 As shown, u AC is the AC power supply; D1 is the rectifier diode; u C is the voltage across the rectifier filter capacitor C; S1, S2, S3, S4 are field effect transistors (MOSFET); R coil and L coil is the equivalent resistance and inductance of the coil; u coil is the coil voltage; i coil is the coil current. Since the current flow direction in the tristable circuit is variable, the current direction shown in the figure is defined for the convenience of subsequent analysis. The main circuit in the figure has three working states: ① Excitation state, S1, S4 are turned on, S2, S3 are turned off, u C After passing through S1 and S2, it is applied to both ends of the coil, so that i coil Rapid rise, this working state is defined as mode 1; ② Demagnetization state, S1, S4 are cut off, S2, S3 are turned on, u C After passing through S3 and S4, it is applied to both ends of the coil, and the magnetic energy of the coil is quickly released, and at the same time, the filter capacitor C is reversely charged, so that i coil Rapid decline, this working state is defined as mode 2; ③Continuous current state, S1, S2 are cut off, S3, S4 are turned on, ignoring the switch tube voltage drop, u coil Almost zero, coil Slowly decrease, this working state is defined as mode 3. The main circuit adjusts the duration of the three working modes through complementary PWM technology, thereby modulating the voltage mean at both ends of the coil to achieve precise regulation of the coil current. The upper and lower power signals of the switches of each pole running in parallel are input to the synchronous control module together for AND logic processing to eliminate the comprehensive errors caused by software and hardware during upper and lower power detection.

[0050] Figure 3This is a waveform showing the tri-stable control principle: the time period from 0 to t1 is the excitation state, and the coil voltage is u C , the current rises rapidly, in mode 1, the coil current rises rapidly to i ref1 ; The time period from t1 to t2 is the freewheeling stage, the coil voltage is 0, the current slowly decreases, and it is in mode 2; in the time period from t3 to t4, the circuit is in a fast demagnetization state, and the coil voltage is a negative voltage -u C , the current drops rapidly and is in mode 3. The tristable circuit provides reverse voltage stably through the DC power supply to achieve a fast demagnetization process, while the traditional bistable circuit relies on TVS to provide negative voltage to achieve demagnetization. Since the electromagnetic switch needs to work frequently, the TVS is easily damaged in the frequent transient voltage environment. Once the TVS is damaged, the dynamic response rate of the coil current is greatly reduced, especially when disconnected, it is affected by the motion back electromotive force, and the disconnection time will be greatly extended, resulting in the failure of zero current disconnection. Therefore, the tristable circuit not only provides a faster dynamic response rate for the coil current, but also has higher reliability.

[0051] (2) Design a synchronous closing control strategy for multi-break electromagnetic switches. Figure 2 Although the synchronous control module shown solves the error of the control module detection time, the difference in parameters such as the reaction spring, the mass of the action component and the coil resistance will affect the action characteristics of the electromagnetic switch.

[0052] The present invention takes into account the design error of the electromagnetic switch body and designs the following Figure 4 The synchronous closing control strategy shown. Figure 4 (a) shows the current and contact displacement changes of switches K1 and K2 before synchronous control. The currents of K1 and K2 are i coil(1) with i coil(2) , the contact displacements of K1 and K2 are x contact(1) With x contact(2) , at the end of interval ①, through |Δx contact | is compared with the set deviation threshold e to determine whether the current reference value needs to be adjusted in the current interval; at this time |Δx contact | is greater than e, so the current reference value of K1 is adjusted and stored in EEPROM for the next pull-in process. Figure 4 (b) is the current and contact displacement after adjustment in interval ①. After adjustment, at the end of interval ①, |Δx contact | is less than e, entering the adjustment phase of interval ②; at the end of interval ②, repeat the adjustment process. Figure 4 (c) and Figure 4 (d) The current and contact displacement after adjustment in intervals ② and ③, respectively. It can be seen from the figure that after adjustment, the consistency of contact displacement of K1 and K2 is improved.

[0053] (3) Design a closing inrush current suppression strategy for parallel multi-break electromagnetic switches. When the control object of a multi-break electromagnetic switch is a resistive inductive load, at the initial moment of closing, the main circuit current is zero, and the transient component does not cause an inrush current at the moment of closing. Instead, an inrush current appears at the peak of the first half-wave. Therefore, a synchronous closing control strategy is adopted to close the switches of each pole before the inrush current appears, so as to avoid a certain pole switch from completely bearing the closing inrush current of the resistive inductive load. When the load is resistive and capacitive, its closing inrush current will be generated at the moment of closing. Due to the dispersion of the switch itself, it is difficult to avoid it. Even if a synchronous closing control strategy is adopted, it is impossible to fully achieve synchronous closing. Therefore, a closing inrush current suppression strategy is required.

[0054] When the load of the multi-break electromagnetic switch is resistive and capacitive, Figure 1 The corresponding circuit differential equation is as follows:

[0055]

[0056] Among them, u c is the capacitive load voltage, U m is the power supply voltage amplitude, α is the initial phase angle of contact closing, and solving the above differential equation, the contact current expression can be obtained as follows:

[0057]

[0058] In the formula, is the power factor angle of resistive and capacitive loads.

[0059] From formula (2), its transient component is:

[0060]

[0061] Unlike resistive and inductive loads, the transient component of resistive and capacitive loads is most obvious at the initial moment of closing, causing the largest inrush current. As time goes by, the exponential part of the transient component in equation (3) gradually decays, and the transient component gradually approaches zero. In order to explore the inrush current value at the moment of closing the resistive and capacitive load, let At t=0, the ratio of the current at closing time to the current under stable operation is:

[0062]

[0063] Where, α∈[0,180°],

[0064] Analyzing formula (4), we can get that the maximum value of k increases with the power factor angle. increases with the increase of When α=90°, k reaches its maximum value. That is, the inrush current at the time of closing is small, and the maximum value is the peak value during stable operation; When the k value increases rapidly, the closing surge current can reach hundreds of times.

[0065] Therefore, for resistive and capacitive loads with a power factor angle greater than 45°, even if a synchronous closing control strategy is adopted, the huge inrush current generated at the moment of closing is borne entirely by the electromagnetic switch that closes first. Therefore, it is necessary to combine a control strategy to suppress the closing inrush current. From formula (2), it can be obtained that by controlling the closing phase angle, the transient component formula (3) can be made zero, thereby achieving the purpose of suppressing the closing inrush current. The corresponding closing phase angle is:

[0066]

[0067] In order to detect the load properties and power factor angle in real time when the load is unknown, a phase-fixed closing control strategy is required to detect the load properties in real time. From formula (2), it can be obtained that the transient component will cause different first current zero-crossing times after closing under different load properties, such as Figure 5 As shown in (a), tc is the closing time, tz is the first zero-crossing time of the current after closing, and the first half-wave time is tb = tz-tc; with 45° as the closing phase angle, record the first current half-wave time of the resistive-inductive load and the resistive-capacitive load under different power factor angles, as shown in Figure 5 (b) As shown. For a pure resistive load, when the circuit breaker is closed at an initial phase angle of 45°, there is no phase difference between the voltage and current, and the first current half-wave time is 7.5ms; while the current of a resistive-inductive load lags behind the voltage, and its first current half-wave time is greater than 7.5ms, and the current of a resistive-capacitive load leads the voltage, and its first current half-wave time is less than 7.5ms, thereby detecting the nature of the load. The power factor angle corresponds to the first current half-wave time one by one, so it is only necessary to close the circuit breaker at 45° for the first time, and the load nature and load power factor angle can be detected based on the first current half-wave time.

[0068] The phase-fixed closing control of multi-break electromagnetic switches has extremely high requirements for the accuracy of voltage zero-point sampling. If there is a deviation in the voltage zero-point detection, the phase-fixed closing strategy will also become invalid. Therefore, there are high requirements for the accuracy of voltage zero-point detection. However, errors are inevitably present in the hardware sampling circuit and the software zero-detection algorithm. Therefore, for multi-break electromagnetic switches running in parallel at each pole, it is necessary to process the contact voltage zero-detection signal through the module logic OR gate circuit. When any pole electromagnetic switch detects the zero point, the logic OR gate circuit immediately issues a zero-point detection completion instruction, and the other pole electromagnetic switches no longer perform zero-point detection and enter the program delay stage at the same time. After the delay stage ends, the switches at each pole enter synchronous closing control.

[0069] Comprehensive synchronous closing control strategy and closing inrush current suppression strategy, formulate Figure 6The coordinated closing control strategy of multi-break electromagnetic switches is shown in the figure. The initial closing phase angle of each pole switch is 45°, which can not only identify the load type according to the first current half-wave time, but also avoid the large closing inrush current that may occur due to random closing phase angles. Figure 5 (a), determine the load properties and power factor angle at this time. If the load will not generate a large closing inrush current, the synchronous closing control strategy can be adopted; if the load will generate a large closing inrush current, the closing phase angle that can suppress the inrush current is determined according to formula (5). The fixed-phase closing is combined with the synchronous closing control strategy to achieve the fixed-phase synchronous closing of the electromagnetic switches of each pole.

[0070] (4) Design a coordinated breaking control strategy for parallel multi-break electromagnetic switches. When a parallel multi-break electromagnetic switch is breaking, although the compensation inductance can suppress the circulating current and prolong the current transfer time, if the asynchronous breaking time of each pole switch is too long and exceeds the current transfer time, the breaking current will still be completed by one pole switch. Therefore, a coordinated breaking control strategy needs to be designed, which can be divided into two parts: synchronous control of the dynamic and static core rigid breaking moment and coordinated control of the breaking process movement stage.

[0071] During the power-off detection process, the control module needs to collect various electrical parameters in real time and perform corresponding processing and control based on the measurement results. However, this process may be affected by factors such as noise, interference and computing resources, resulting in certain differences in processing time. In order to ensure the synchronization of the moment when the current of each pole switch coil drops to zero, a synchronous power-off signal is issued through logical communication to improve the consistency of the power-off moment.

[0072] The control process of the synchronization of the dynamic and static core rigid separation is as follows Figure 7 As shown. First, the control power is disconnected, and switches K1 and K2 enter the power-off detection state. The influence of the difference in the control module processing time is avoided through the AND gate logic communication, and the consistency of the power-off time of the two switches is achieved. When K1 and K2 receive the synchronous power-off signal, they enter the negative pressure demagnetization state. The use of the synchronization control strategy at the moment of just-opening can make the current of the two electromagnetic switches drop to zero almost at the same time, realizing the synchronous control of the moment of just-opening of the iron core.

[0073] After the dynamic and static cores are synchronously controlled at the split moment, the coil current is synchronously reduced to zero, and the residual magnetism inside the core is ignored. The electromagnetic attraction generated by the electromagnetic mechanism approaches zero. At this time, the displacement of the dynamic core is mainly affected by the reaction force characteristics of the switch itself. However, due to the differences in the reaction force characteristics of different switches, the displacement curves of the dynamic cores of different switches are inconsistent. Therefore, the present invention further proposes a control strategy for changing the displacement of the dynamic core by adjusting the electromagnetic attraction.

[0074] The coordinated control strategy flow of the motion phase of the breaking process is as follows: first, synchronize the moment when the moving and static iron cores are just separated, and then apply a constant duty cycle or current for excitation to generate electromagnetic attraction to adjust the force on the moving iron core. By controlling the electromagnetic switch with a faster displacement change of the moving iron core, the consistency of the displacement of multiple switches can be achieved. This strategy can also be extended to parallel multi-break electromagnetic switches to improve the dynamic voltage balancing of the series breaks.

Claims

1. A parallel multi-break electromagnetic switch coordinated control method, characterized in that The following steps are involved: Step 1: Design a multi-break electromagnetic switch hardware control module; Step 2: Design a synchronous closing control strategy for multi-break electromagnetic switches; Step 3: Design a closing inrush current suppression strategy for parallel multi-break electromagnetic switches; Step 4: Design a coordinated breaking control strategy for parallel multi-break electromagnetic switches.

2. A parallel multi-break electromagnetic switch coordinated control method according to claim 1, characterized in that: In the step 1, the multi-break electromagnetic switch hardware control module sets a tri-stable control circuit, including an AC power supply u AC , rectifier diode D1, rectifier filter capacitor C, first field effect tube S1, second field effect tube S2, third field effect tube S3 and fourth field effect tube S4, equivalent resistance R of the coil coil and inductor L coil ; The voltage across the rectifier filter capacitor C is u C .

3. A parallel multi-break electromagnetic switch coordinated control method according to claim 2, characterized in that: The tri-stable control circuit includes three working states: In the excitation state, the first field effect tube S1 and the fourth field effect tube S4 are turned on, the second field effect tube S2 and the third field effect tube S3 are turned off, and the voltage across the rectifier filter capacitor C is u C After passing through the first field effect transistor S1 and the second field effect transistor S2, it is applied to both ends of the coil, so that the coil current i coil Rapid rise, this working state is defined as mode 1; In the demagnetization state, the first field effect tube S1 and the fourth field effect tube S4 are turned off, the second field effect tube S2 and the third field effect tube S3 are turned on, and the voltage across the rectifier filter capacitor C is u C After passing through the third field effect transistor S3 and the fourth field effect transistor S4, the coil magnetic energy is quickly released, and the filter capacitor C is reversely charged, so that the coil current i coil Rapid decline, this working state is defined as mode 2; In the freewheeling state, the first field effect tube S1 and the second field effect tube S2 are turned off, the third field effect tube S3 and the fourth field effect tube S4 are turned on, and the voltage drop of the switch tube is ignored. The coil voltage u coil Almost zero, coil Slowly descending, this working state is defined as mode 3.

4. A parallel multi-break electromagnetic switch coordinated control method according to claim 1, characterized in that: In step 2, the switch K1 and the switch K2 are set to be synchronously controlled, and the currents of K1 and K2 are respectively i coil(1) with i coil(2) , the contact displacements of K1 and K2 are x contact(1) With x contact(2) , at the end of interval ①, through |Δx contact | is compared with the set deviation threshold e to determine whether the current reference value needs to be adjusted in the current interval; at this time |Δx contact | is greater than e, so the current reference value of K1 is adjusted and stored in EEPROM for the next pull-in process.

5. A parallel type multi-break electromagnetic switch coordinated control method according to claim 1, characterized in that: In step 3, when the control object of the multi-break electromagnetic switch is a resistive inductive load, at the initial moment of closing, the main circuit current is zero; When the load of the multi-break electromagnetic switch is resistive and capacitive, the corresponding circuit differential equation is as follows: Among them, u c is the capacitive load voltage, U m is the power supply voltage amplitude, α is the initial phase angle of contact closing, and solving the above differential equation, the contact current expression can be obtained as follows: In the formula, is the power factor angle of resistive and capacitive load; From formula (2), its transient component is: Unlike resistive and inductive loads, the transient component of resistive and capacitive loads is most obvious at the initial moment of closing, causing the largest inrush current. As time goes by, the exponential part of the transient component in equation (3) gradually decays, and the transient component gradually approaches zero. In order to explore the inrush current value of the resistive and capacitive load at the moment of closing, let At t=0, the ratio of the current at closing time to the current under stable operation is: Where, α∈[0,180°], Analyzing formula (4), we can get that the maximum value of k increases with the power factor angle. increases with the increase of When α=90°, k reaches its maximum value. That is, the inrush current at the time of closing is small, and the maximum value is the peak value during stable operation; When the k value increases rapidly, the closing inrush current can reach hundreds of times; From formula (2), it can be obtained that by controlling the closing phase angle, the transient component formula (3) can be made zero, thereby achieving the purpose of suppressing the closing inrush current. The corresponding closing phase angle is:

6. A parallel multi-break electromagnetic switch coordinated control method according to claim 1, characterized in that: The step 4 specifically includes firstly performing synchronous control of the moment when the moving and static iron cores are just separated, and then applying a constant duty cycle or current for excitation to generate electromagnetic attraction to adjust the force on the moving iron core; by controlling the electromagnetic switch with a faster displacement change of the moving iron core, the consistency of the displacement of multiple switches is achieved.

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