Bridge type discharge circuit, repetitive pulse magnetic field generation device and method

Abstract

The invention discloses a bridge type discharge circuit and a repetitive pulse magnetic field generation device and method, and belongs to the technical field of power electronics. A combination switch module on a discharge bridge arm comprises a first switch unit and a second switch unit; the first switch unit comprises one or more thyristors connected in series and first resistors connected to the two ends of each thyristor in parallel. The second switch unit comprises a full-control switch device group and a second resistor connected in parallel to the two ends of the full-control switch device group; the full-control switching device group comprises one or more full-control switching devices which are connected in parallel; since the voltage resistance and the through-current capability of the thyristors are stronger than those of full-control switching devices, compared with a conventional discharge bridge arm which can meet the requirements of high voltage resistance and large current only by connecting a large number of full-control switching devices in series and parallel, the discharge bridge arm disclosed by the invention can meet the same requirements of high voltage resistance and large current by adopting fewer full-control switching devices, and is simple in structure and low in cost. The control difficulty is reduced, the reliability is improved, and the economic cost is also reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of power electronics, and more specifically, relates to a bridge discharge circuit, a repeated pulse magnetic field generating device and a method. Background Art

[0002] As a type of pulsed strong magnetic field, repetitive pulsed strong magnetic field has important applications in scientific research fields such as neutron diffraction, terahertz radiation, guided magnetic field, and civil fields such as transcranial magnetic stimulation, electromagnetic welding, and electromagnetic forming, and has important research significance. Unidirectional repetitive pulsed strong magnetic field is a pulsed strong magnetic field with only one magnetic field direction. The basic principle of the unidirectional repetitive pulsed strong magnetic field generating device is: first, the energy storage capacitor is charged to the required voltage value through a charger, and then the inductive load is discharged by timely switching on and off the bridge discharge circuit to generate a unidirectional pulse current. The pulse current generates a unidirectional pulse magnetic field through the inductive load, and repeating this process will generate a unidirectional repetitive pulsed strong magnetic field. It can be seen that the bridge discharge circuit is an important part of the unidirectional repetitive pulsed strong magnetic field generating device. Therefore, it is of great significance to study a bridge discharge circuit.

[0003] In actual application, the switch tube of the bridge discharge circuit needs to withstand thousands to tens of kilovolts of high voltage from the energy storage capacitor. The peak current flowing through the switch tube during discharge can reach thousands to tens of kiloamperes, and the switch tube is required to be a high-voltage fully controlled switch device to achieve timely opening and closing. The existing bridge discharge circuit generally includes a diode and a fully controlled switch device. When the voltage of the energy storage capacitor is higher, it is necessary to use the fully controlled switch devices in the bridge arm of the discharge circuit in series to improve the withstand voltage level. At the same time, when the discharge current is large, it is also necessary to use multiple fully controlled switch devices in parallel to improve the current carrying capacity of the bridge arm. Since the switching speed of the fully controlled switch device is relatively fast, the use of the fully controlled switch device in series requires that each fully controlled switch device has a high consistency of opening and closing to prevent uneven voltage distribution, which increases the difficulty of controlling the discharge circuit and reduces reliability. On the other hand, a large number of fully controlled switch devices used in series and parallel also increase the number of switch devices. Since the cost of large-capacity fully controlled switch devices is relatively high, this leads to a low economic efficiency of the discharge circuit composed of a large number of high-voltage and large-capacity fully controlled switch devices to form a bridge arm. Summary of the invention

[0004] In view of the above defects or improvement needs of the prior art, the present invention provides a bridge discharge circuit, a repetitive pulse magnetic field generating device and a method, which are used to solve the problem that the existing bridge discharge circuit cannot achieve high voltage and high current resistance requirements with lower cost and higher reliability.

[0005] In order to achieve the above-mentioned object, in a first aspect, the present invention provides a bridge discharge circuit, comprising: an inductive load, and a first discharge bridge arm and a second discharge bridge arm connected in parallel; the first discharge bridge arm and the second discharge bridge arm both comprise a composite switch module and a diode connected in series;

[0006] The composite switch module comprises: a first switch unit and a second switch unit connected in series; the first switch unit comprises one or more thyristors connected in series, and a first resistor connected in parallel at both ends of each thyristor; the second switch unit comprises: a fully controlled switch device group, and a second resistor connected in parallel at both ends of the fully controlled switch device group; the fully controlled switch device group comprises: one or more fully controlled switch devices connected in parallel;

[0007] The negative end of the fully controlled switch device serves as the A end of the composite switch module, the positive end is connected to the cathode of the first switch unit, and the anode of the first switch unit serves as the B end of the composite switch module;

[0008] The cathode of the diode in the first discharge bridge arm is connected to the A end of the composite switch module in the first discharge bridge arm, and the anode is connected to the A end of the composite switch module in the second discharge bridge arm; the anode of the diode in the second discharge bridge arm is connected to the B end of the composite switch module in the second discharge bridge arm, and the cathode is connected to the B end of the composite switch module in the first discharge bridge arm; the two ends of the inductive load are respectively connected to the cathode of the diode in the first discharge bridge arm and the anode of the diode in the second discharge bridge arm.

[0009] Further preferably, the fully-controlled switching device is an IGBT; the negative terminal of the fully-controlled switching device is the emitter of the IGBT, and the positive terminal is the collector of the IGBT.

[0010] Further preferably, the fully-controlled switching device is an NMOS tube or a PMOS tube; when the fully-controlled switching device is an NMOS tube, the negative end of the fully-controlled switching device is the source of the NMOS tube, and the positive end is the drain of the NMOS tube; when the fully-controlled switching device is a PMOS tube, the negative end of the fully-controlled switching device is the drain of the PMOS tube, and the positive end is the source of the PMOS tube.

[0011] Further preferably, the inductive load is a magnetic coil.

[0012] Further preferably, the thyristor is an electrically controlled unidirectional thyristor or a light controlled unidirectional thyristor.

[0013] In a second aspect, the present invention provides a repetitive pulse magnetic field generating device, comprising: a controller, a charger, an energy storage capacitor C1, a switch K1 and the bridge discharge circuit provided in the first aspect of the present invention;

[0014] After the energy storage capacitor C1 is connected in parallel with the bridge discharge circuit, it is connected to both ends of the charger through the switch K1;

[0015] The controller is used to repeatedly perform the operation of generating a unidirectional pulsed magnetic field, thereby generating a repetitive pulsed magnetic field;

[0016] The operation of generating a unidirectional pulsed magnetic field includes:

[0017] When all the fully controlled switch devices and thyristors in the bridge discharge circuit are in the off state, the switch K1 is closed until the charger charges the energy storage capacitor C1 to the required voltage, and then the switch K1 is opened; at the same time, a drive signal for controlling the conduction of the fully controlled switch devices and thyristors is sent to the fully controlled switch devices and thyristors, and the energy storage capacitor C1 starts to discharge; during the discharge process of the energy storage capacitor C1, current begins to be generated on the inductive load in the bridge discharge circuit; when the current on the inductive load reaches the current peak, all the fully controlled switch devices are turned off at the same time, and then all the thyristors are automatically turned off due to the loss of the holding current, and the current on the inductive load is continued through the diodes of the two discharge bridge arms in the bridge discharge circuit, and continues to decrease until it reaches zero; in this process, a unidirectional pulse current is generated on the inductive load, and a unidirectional pulse magnetic field is generated accordingly.

[0018] Further preferably, the above-mentioned repetitive pulse magnetic field generating device also includes: a discharge current sensor; the discharge current sensor is used to detect the current on the inductive load and transmit it to the controller.

[0019] In a third aspect, the present invention provides a method for generating a repetitive pulsed magnetic field, comprising: repeatedly performing an operation of generating a unidirectional pulsed magnetic field, thereby generating a repetitive pulsed magnetic field;

[0020] The operation of generating a unidirectional pulsed magnetic field includes:

[0021] When all the fully controlled switch devices and thyristors in the bridge discharge circuit are in the off state, the switch K1 is closed until the charger charges the energy storage capacitor C1 to the required voltage, and then the switch K1 is opened; at the same time, a driving signal for controlling the conduction of the fully controlled switch devices and thyristors is sent to the fully controlled switch devices and thyristors, and the energy storage capacitor C1 starts to discharge; during the discharge process of the energy storage capacitor C1, current begins to be generated on the inductive load in the bridge discharge circuit; when the current on the inductive load reaches the current peak, all the fully controlled switch devices are turned off at the same time, and then all the thyristors are automatically turned off due to the loss of the holding current, and the current on the inductive load is continued through the diodes of the two discharge bridge arms in the bridge discharge circuit, and continues to decrease until it reaches zero; in this process, a unidirectional pulse current is generated on the inductive load, and a unidirectional pulse magnetic field is generated accordingly;

[0022] The energy storage capacitor C1 is connected in parallel with the bridge discharge circuit and then connected to both ends of the charger through the switch K1; the bridge discharge circuit is the bridge discharge circuit provided in the first aspect of the present invention.

[0023] In a fourth aspect, the present invention provides an electronic device, comprising: a memory and a processor, wherein the memory stores a computer program, and when the processor executes the computer program, the method for generating a repetitive pulsed magnetic field provided in the third aspect of the present invention is executed.

[0024] In a fifth aspect, the present invention further provides a computer-readable storage medium, which includes a stored computer program, wherein when the computer program is executed by a processor, the device where the storage medium is located is controlled to execute the repetitive pulse magnetic field generation method provided in the third aspect of the present invention.

[0025] In general, the above technical solutions conceived by the present invention can achieve the following beneficial effects:

[0026] 1. The present invention provides a bridge discharge circuit, wherein the composite switch module on the discharge bridge arm comprises a first switch unit and a second switch unit connected in series; the first switch unit comprises one or more thyristors connected in series, and a first resistor connected in parallel at both ends of each thyristor; the second switch unit comprises: a fully-controlled switch device group, and a second resistor connected in parallel at both ends of the fully-controlled switch device group; the fully-controlled switch device group comprises: one or more fully-controlled switch devices connected in parallel; since the withstand voltage and current carrying capacity of the thyristor are stronger than those of the fully-controlled switch device, by connecting the thyristor and the fully-controlled switch device in series, and connecting a resistor in parallel at both ends of each thyristor and the fully-controlled switch device group, the difference in the turn-on speed between the thyristor and the fully-controlled switch device can be reasonably utilized, so that the voltage borne by the fully-controlled switch device during the entire discharge process is relatively small, and most of the high voltage is borne by the thyristor. Compared with the traditional discharge bridge arm which needs to use a large number of fully-controlled switching devices in series and parallel to achieve the high voltage and high current requirements, the present invention uses fewer fully-controlled switching devices and thyristors to achieve the same high voltage and high current requirements. The overall structure is simple, which avoids the requirement for high consistency of turning on and off when the fully-controlled switching devices are used in series, reduces the control difficulty of the discharge circuit, improves reliability, and also reduces economic costs. Therefore, the present invention can achieve high voltage and high current requirements at a lower cost and higher reliability.

[0027] 2. The present invention provides a repetitive pulse magnetic field generating device, which detects the peak value of the current flowing through the inductive load and controls the fully controlled switch devices and thyristors in the bridge discharge circuit to turn on and off at the appropriate time; thereby generating a unidirectional pulse current on the inductive load, thereby generating a unidirectional pulse magnetic field by the magnetic coil, and repeating the above process to generate a repetitive pulse magnetic field. The bridge discharge circuit used is the bridge discharge circuit provided by the first aspect of the present invention, which can achieve high voltage and high current resistance requirements at a lower cost and higher reliability, and has better overall performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 A schematic diagram of a bridge discharge circuit provided by an embodiment of the present invention;

[0029] Figure 2 A schematic diagram of a repetitive pulse magnetic field generating device provided in an embodiment of the present invention;

[0030] Figure 3 A schematic diagram of a conventional repetitive pulse magnetic field generating device provided by an embodiment of the present invention;

[0031] Figure 4 The voltage and current waveforms of the main components of the conventional repetitive pulse magnetic field generating device provided by the embodiment of the present invention during operation;

[0032] Figure 5 A schematic diagram of the IGBT series-parallel combination switch structure used in a conventional repetitive pulse magnetic field generating device provided in an embodiment of the present invention;

[0033] Figure 6 The voltage and current waveforms of the main components of the repetitive pulse magnetic field generating device provided by the present invention during operation;

[0034] Figure 7 A schematic diagram of the structure of a composite switch module provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0036] In order to achieve the above-mentioned object, in a first aspect, the present invention provides a bridge discharge circuit, comprising: an inductive load, and a first discharge bridge arm and a second discharge bridge arm connected in parallel; the first discharge bridge arm and the second discharge bridge arm both comprise a composite switch module and a diode connected in series;

[0037] The composite switch module comprises: a first switch unit and a second switch unit connected in series; the first switch unit comprises one or more thyristors connected in series, and a first resistor connected in parallel at both ends of each thyristor; the second switch unit comprises: a fully controlled switch device group, and a second resistor connected in parallel at both ends of the fully controlled switch device group; the fully controlled switch device group comprises: one or more fully controlled switch devices connected in parallel;

[0038] The negative end of the fully controlled switch device serves as the A end of the composite switch module, the positive end is connected to the cathode of the first switch unit, and the anode of the first switch unit serves as the B end of the composite switch module;

[0039] The cathode of the diode in the first discharge bridge arm is connected to the A end of the composite switch module in the first discharge bridge arm, and the anode is connected to the A end of the composite switch module in the second discharge bridge arm; the anode of the diode in the second discharge bridge arm is connected to the B end of the composite switch module in the second discharge bridge arm, and the cathode is connected to the B end of the composite switch module in the first discharge bridge arm; the two ends of the inductive load are respectively connected to the cathode of the diode in the first discharge bridge arm and the anode of the diode in the second discharge bridge arm.

[0040] It should be noted that when the first switch unit includes a thyristor, the anode of the first switch unit is the anode of the thyristor, and the cathode of the first switch unit is the cathode of the thyristor. When the first switch unit includes multiple thyristors connected in series, the cathode of the i-th thyristor is connected to the anode of the i+1-th thyristor, i=1,2,…,M-1, M is the number of thyristors, the anode of the first switch unit is the anode of the first-stage thyristor, and the cathode of the first switch unit is the cathode of the last-stage thyristor.

[0041] In an optional embodiment, the fully-controlled switching device can be a switching device such as an IGBT, a MOSFET, or an IGCT. When the fully-controlled switching device is an IGBT, the negative terminal of the fully-controlled switching device is the emitter of the IGBT, and the positive terminal is the collector of the IGBT. MOSFET includes two types: NMOS tube and PMOS tube; when the fully-controlled switching device is an NMOS tube, the negative terminal of the fully-controlled switching device is the source of the NMOS tube, and the positive terminal is the drain of the NMOS tube; when the fully-controlled switching device is a PMOS tube, the negative terminal of the fully-controlled switching device is the drain of the PMOS tube, and the positive terminal is the source of the PMOS tube. When the fully-controlled switching device is an IGCT, the negative terminal of the fully-controlled switching device is the cathode of the IGCT, and the positive terminal is the anode of the IGCT.

[0042] It should be noted that the inductive load is used to generate a pulse magnetic field under the excitation of an electric current, and can be various types of magnetic coils, such as an air-core coil, a magnetic core coil, a motor winding coil, and the like.

[0043] It should be noted that the thyristor may be a commonly used half-controlled switching device, including a thyristor or a half-controlled device derived therefrom, such as an electrically controlled unidirectional thyristor, a light-controlled unidirectional thyristor, and the like.

[0044] In order to further illustrate the bridge discharge circuit provided by the present invention, the following is a detailed description taking IGBT as a fully controlled switching device as an example:

[0045] like Figure 1The figure shows a schematic diagram of a bridge discharge circuit provided in this embodiment, which specifically includes: a first discharge bridge arm, a second discharge bridge arm and a magnet (equivalent to L1 and R1). The two discharge bridge arms each include a composite switch module and a diode connected in series;

[0046] In this embodiment, in the first discharge bridge arm, the first switch unit includes: thyristor S1, and resistor R1 connected in parallel at both ends of thyristor S1; the second switch unit includes: a fully controlled switch device group, and a second resistor R2 connected in parallel at both ends of the fully controlled switch device group; the fully controlled switch device group includes: IGBT switch T1. In the second discharge bridge arm, the first switch unit includes: thyristor S2, and resistor R3 connected in parallel at both ends of thyristor S2; the second switch unit includes: a fully controlled switch device group, and a second resistor R4 connected in parallel at both ends of the fully controlled switch device group; the fully controlled switch device group includes: IGBT switch T2.

[0047] Since the withstand voltage and current carrying capacity of high-voltage thyristors are stronger than those of high-voltage IGBTs, under the same capacitor voltage and discharge current, the number of thyristors and IGBTs used in series and parallel in the bridge arm of the discharge circuit of the present invention is far less than the number of high-voltage IGBTs used in series and parallel in the bridge arm of the traditional discharge circuit. Fewer switches and avoiding the series use of IGBTs make the bridge arm more reliable than the traditional circuit. At the same time, the combined cost of thyristors and IGBTs is lower than that of high-voltage IGBTs, and the number of switches used is less, so the entire discharge circuit is more economical. In summary, the high-voltage and high-current repetitive pulse discharge circuit proposed by the present invention has more advantages.

[0048] In a second aspect, the present invention provides a repetitive pulse magnetic field generating device, comprising: a controller, a charger, an energy storage capacitor C1, a switch K1 and the bridge discharge circuit provided in the first aspect of the present invention;

[0049] After the energy storage capacitor C1 is connected in parallel with the bridge discharge circuit, it is connected to both ends of the charger through the switch K1;

[0050] Among them, at the initial moment, all fully controlled switch devices and thyristors in the bridge discharge circuit are disconnected;

[0051] The controller is used to repeatedly perform the operation of generating a unidirectional pulsed magnetic field, thereby generating a repetitive pulsed magnetic field;

[0052] The operation of generating a unidirectional pulsed magnetic field includes:

[0053] When all the fully controlled switch devices and thyristors in the bridge discharge circuit are in the off state, the switch K1 is closed until the charger charges the energy storage capacitor C1 to the required voltage, and then the switch K1 is opened; at the same time, a drive signal for controlling the conduction of the fully controlled switch devices and thyristors is sent to the fully controlled switch devices and thyristors, and the energy storage capacitor C1 starts to discharge; during the discharge process of the energy storage capacitor C1, current begins to be generated on the inductive load in the bridge discharge circuit; when the current on the inductive load reaches the current peak, all the fully controlled switch devices are turned off at the same time, and then all the thyristors are automatically turned off due to the loss of the holding current, and the current on the inductive load is continued through the diodes of the two discharge bridge arms in the bridge discharge circuit, and continues to decrease until it reaches zero; in this process, a unidirectional pulse current is generated on the inductive load, and a unidirectional pulse magnetic field is generated accordingly.

[0054] In an optional implementation, the above-mentioned repetitive pulse magnetic field generating device also includes: a discharge current sensor; the discharge current sensor is used to detect the current on the inductive load and transmit it to the controller.

[0055] The related technical solution is the same as the bridge discharge circuit provided in the first aspect of the present invention, and will not be described in detail here.

[0056] In order to further illustrate the repetitive pulse magnetic field generating device provided by the present invention, the following is a detailed description taking IGBT as a fully controlled switching device as an example:

[0057] like Figure 2 The figure shows a schematic diagram of a repetitive pulse magnetic field generating device provided in this embodiment, which specifically includes: a front-stage high-voltage charger, a charging outlet switch K1, a high-voltage energy storage capacitor C1, a first discharge bridge arm, a second discharge bridge arm, a magnet (equivalent to L1 and R1), a discharge current sensor G1, and a controller (mainly including a current differentiator and a trigger and drive output controller). Among them, both discharge bridge arms include a composite switch module and a diode connected in series;

[0058] For the convenience of description, in this embodiment, the number of thyristors and IGBT switches in the composite switch module is 1 as an example. Specifically, in the first discharge bridge arm, the first switch unit includes: thyristor S1, and a resistor R1 connected in parallel at both ends of the thyristor S1; the second switch unit includes: a fully controlled switch device group, and a second resistor R2 connected in parallel at both ends of the fully controlled switch device group; the fully controlled switch device group includes: IGBT switch T1. In the second discharge bridge arm, the first switch unit includes: thyristor S2, and a resistor R3 connected in parallel at both ends of the thyristor S2; the second switch unit includes: a fully controlled switch device group, and a second resistor R4 connected in parallel at both ends of the fully controlled switch device group; the fully controlled switch device group includes: IGBT switch T2.

[0059] When it is necessary to generate repeated pulses through the discharge circuit, first close the charging outlet switch K1, use the charger to charge the energy storage capacitor C1 to the required rated voltage, then disconnect the switch K1, and then send the conduction drive signal to all IGBTs and all thyristors at the same time. Since the IGBT turns on faster, it turns on first, while the thyristor turns on slower after t d (t d The typical value is tens of microseconds) and then turns on after a time delay. After the thyristors S1 and S2 are turned on, the capacitor C1 starts to discharge the magnet, and the magnet current continues to rise to the maximum value. At this time, the magnet current i measured by the current sensor is L After the differentiator differentiates, the current passes through zero. The trigger and drive output controller is triggered by the current differential signal that passes through zero. Immediately, the two IGBT switch tubes T1 and T2 are turned off through the drive signal. After the IGBT switch tubes T1 and T2 are turned off, the thyristors lose the holding current through t q (t q is the turn-off time, which is the sum of the forward blocking recovery time and the reverse blocking recovery time, generally a few microseconds to tens of microseconds, depending on the thyristor model) and then it automatically turns off after a certain time. From the time S1 and S2 are turned on to the time T1 and T2 are turned off, the voltage of capacitor C1 continues to drop, and the magnet current continues to rise. After T1 and T2 are turned off, diodes D1 and D2 are naturally turned on, and the magnet current flows back to capacitor C1 through D1 and D2. The magnet current continues to drop until it is zero, and the voltage of capacitor C1 continues to rise and reaches the maximum value when the current is zero. The above is a single discharge process of a complete discharge circuit, which will generate a unidirectional pulse. If you want to generate repeated pulses, repeat the above discharge process after the above single discharge process ends.

[0060] Due to the existence of the resistor voltage-sharing circuit and the reasonable use of the difference in the turn-on speed of the thyristor and the IGBT switch to control the turn-on time sequence of the thyristor and the IGBT, the voltage borne by the IGBT switches T1 and T2 during the entire discharge process is relatively small, and most of the high voltage is borne by the thyristors S1 and S2.

[0061] The present invention improves the fully controlled switch device in the bridge arm of the traditional repetitive pulse discharge circuit into a series switch composed of a fully controlled switch device with a lower withstand voltage level and a high-voltage thyristor, and cooperates with the corresponding control logic, and utilizes the high voltage and large current resistance characteristics of the thyristor to achieve the improvement of the voltage and current level of the repetitive pulse discharge circuit, reduces the number of fully controlled switch devices in the circuit, and utilizes the fully controlled switch devices with a lower withstand voltage level to achieve full control of the bridge arm. In high discharge voltage and current situations, the discharge bridge arm composed of a smaller number of thyristors and a fully controlled switch device with a lower withstand voltage level in series in the present invention has better opening and closing consistency than the traditional discharge bridge arm composed of a large number of fully controlled switch devices in series and parallel, simpler structure, and thus higher reliability. While the number of switch devices is reduced, since thyristors with the same voltage and current level are usually lower in cost than fully controlled devices, the repetitive pulse magnetic field generating device proposed by the present invention is more economical than the traditional repetitive pulse magnetic field generating device.

[0062] In order to further illustrate the performance of the repetitive pulse magnetic field generating device provided by the present invention, a comparative analysis is performed with a conventional current repetitive pulse magnetic field generating device as follows:

[0063] Figure 3 The schematic diagram of the conventional repetitive pulse magnetic field generating device includes: a front-stage high-voltage charger, a charging outlet switch K1, a high-voltage energy storage capacitor C1, a discharge bridge arm, an inductive magnet (L1 and R1), a discharge current sensor G1, a current differentiator, and a trigger and drive output controller. The discharge bridge arm is composed of high-voltage IGBT switch tubes T1 and T2 and diodes D1 and D2.

[0064] When it is necessary to generate repeated pulses through the discharge circuit, first close the charging outlet switch K1, use the high-voltage charger to charge the energy storage capacitor C1 to the required rated voltage, and then disconnect the switch K1. After charging is completed, the two IGBT switches T1 and T2 are turned on at the same time by the driving signal output by the trigger and drive output controller. After T1 and T2 are turned on, the capacitor C1 starts to discharge the magnet (the magnet is inductive, where L1 is its inductance, R L is the internal resistance of the magnet), the magnet current continues to rise until it reaches the maximum value, at which time the magnet current i measured by the current sensor is LAfter the differentiator differentiates, it passes through zero. After the trigger and drive output controller is triggered by the zero-crossing current differential signal, it immediately turns off the two IGBT switch tubes T1 and T2 through the drive signal. From the time T1 and T2 are turned on to the time they are turned off, the voltage of capacitor C1 continues to drop, and the magnet current continues to rise. After T1 and T2 are turned off, diodes D1 and D2 are naturally turned on, and the magnet current flows back to capacitor C1 through D1 and D2 and continues to drop until it reaches zero. The voltage of capacitor C1 continues to rise and reaches the maximum value when the current is zero. The above is a single discharge process of a complete discharge circuit, which will generate a unidirectional pulse. If you want to generate a repeated pulse, repeat the above discharge process after the above single discharge process ends.

[0065] Figure 4 The voltage and current waveforms of the main components of the traditional repetitive pulse magnetic field generator during operation are shown below. During the period 0 to t1, the energy storage capacitor C1 has been charged to the required rated voltage by the charger, and the voltages borne by the IGBT switches T1 and T2 are:

[0066]

[0067] Among them U C1 is the rated voltage required by the energy storage capacitor C1, u T1,T2 is the voltage borne by IGBT switches T1 and T2.

[0068] At t1, T1 and T2 are turned on at the same time. After T1 and T2 are turned on, u T1,T2 is zero, capacitor C1 starts to discharge the magnet, the voltage of capacitor C1 continues to drop until it reaches the minimum value at t2, and the magnet current continues to rise until it reaches the maximum value at t2. L satisfy:

[0069]

[0070] That is, the magnet current differential is zero at time t2, and the magnet current i measured by the current sensor is L After the differentiator differentiates, it passes through zero. The trigger and drive output controller is triggered by the zero-crossing current differential signal and turns off T1 and T2 at the same time at time t2. After T1 and T2 are turned off, diodes D1 and D2 are naturally turned on, and the magnet current flows back to capacitor C1 through D1 and D2. The magnet current continues to decrease until it reaches zero at time t3, and the capacitor C1 voltage continues to rise and reaches the maximum value at t3. Ignoring the voltage drop of diodes D1 and D2, the period from t2 to t3 u T1,T2 satisfy:

[0071]

[0072] where u C1 is the voltage of capacitor C1.

[0073] Due to the internal resistance of the magnet RL Due to the on-resistance of T1 and T2, part of the energy of capacitor C1 is dissipated, resulting in the capacitor voltage u at time t3. C1 (t3) is less than U C1 ,u C1 (t3) Generally meets the following requirements:

[0074]

[0075] Due to the internal resistance of the magnet R L The on-resistance of T1 and T2 is usually small, at tens of milliohms, so k generally satisfies 0.9. <k<1。

[0076] Due to the internal resistance of the magnet R L As the internal resistance of T1 and T2 is small, the discharge process during the period from t1 to t3 can be considered to be approximately undamped. Therefore, the magnet current during the period from t1 to t3 is approximately:

[0077]

[0078] Therefore, during the discharge process, the magnet current i at time t2 is L The maximum value is

[0079] During the period t3 to t4, T1 and T2 are turned off, D1 and D2 are cut off, and u T1,T2 Equal to 0.5u C1 (t3), during the period t4-t5, the energy storage capacitor C1 is recharged by the charger to the required rated voltage to prepare for the next discharge. A complete single discharge process of the discharge circuit ends here, and this process generates a unidirectional pulse. After the above single discharge process ends, the above discharge process can be repeated to generate a repeated pulse.

[0080] Depend on Figure 4 From the switch tube voltage curve and formulas (1.3) and (1.4), we can know that the maximum voltage u that T1 and T2 bear during the entire discharge process is T1,T2 (max) is:

[0081]

[0082] Figure 4 The capacitor C1 corresponding to the waveform in the middle is 680μF, and the rated voltage U C1 is 15kV, the magnet inductance is 200μH, and the magnet resistance R L Substitute into formula (1.6) and consider the most extreme case k value is 1, the withstand voltage value of IGBT switch tubes T1 and T2 is U T1,T2 Need to meet:

[0083]

[0084] From formula (1.5), we can get the instantaneous peak current I that the IGBT switches T1 and T2 are allowed to pass through: T1,T2 Need to meet:

[0085]

[0086] Therefore, if the capacitor C1 is 680μF, the rated voltage U C1 The voltage is 15kV, the magnetic inductance is 200μH, and the Figure 3 The traditional repetitive pulse magnetic field generating device shown in the figure needs to select a high-voltage and large-capacity IGBT series-parallel combination switch structure with a withstand voltage greater than 15kV and a maximum allowable current greater than 27.66kA. The typical maximum withstand voltage of a single tube of an existing IGBT switch is 6500V, and the typical maximum instantaneous current capacity corresponding to this voltage level is 1500A. If an IGBT switch with a withstand voltage of 6500V and an instantaneous current capacity of 1500A is selected, a certain voltage and current margin should be considered, such as Figure 5 As shown, 3 series and 22 parallels, totaling 66 high-voltage IGBT series-parallel combination switches are needed to replace Figure 3 The switch tubes T1 and T2 in the circuit are connected to meet the design requirements. The use of multiple IGBTs in series has the problem of consistency between on and off, which increases the control difficulty and structural complexity of the discharge circuit and reduces the circuit reliability. The cost of large-capacity high-voltage IGBT switches is high in itself, and the use of a large number of series and parallel connections also further increases the cost of the discharge circuit.

[0087] The present embodiment provides Figure 2 The voltage and current waveforms of the main components of the repetitive pulse magnetic field generating device during operation are shown in FIG. Figure 6 As shown. During the period 0 to t1, the energy storage capacitor C1 has been charged to the required rated voltage by the charger, and the voltages borne by the low-side IGBT switches T1 and T2 and the thyristors S1 and S2 are:

[0088]

[0089] R1 and R2 are voltage-equalizing circuits connected in parallel at both ends of S1 and T1, respectively, and satisfy R1=nR2, where n is the voltage-equalizing ratio of the voltage-equalizing circuit. In addition, R3 and R4 are voltage-equalizing circuits connected in parallel at both ends of S2 and T2, respectively, and satisfy R3=R1=nR4=nR2.

[0090] At time t1, the low-side IGBT and thyristor drive signals are sent simultaneously. Since the low-side IGBT turns on faster, it turns on first. After T1 and T2 are turned on, the voltage drop across them during the period t1 to t2 is zero. The voltage S1 and S2 bear is:

[0091]

[0092] Thyristors S1 and S2 are d (t d The typical value is tens of microseconds, here we take t d =50μs) is fully turned on at t2 after a time delay. After the thyristors S1 and S2 are turned on, the voltage across their two ends also drops to zero. At this time, capacitor C1 begins to discharge to the magnet. The voltage of capacitor C1 continues to drop to the minimum value at t3, and the magnet current continues to rise to the maximum value at t3.

[0093] The magnet current i at time t3 L Satisfies equation (1.2). That is, at time t3, the magnet current differential is zero, and the magnet current i measured by the current sensor is L After the differentiator differentiates, the current passes through zero. The trigger and drive output controller is triggered by the current differential signal that passes through zero, and T1 and T2 are turned off at the same time at time t3. After T1 and T2 are turned off, diodes D1 and D2 are naturally turned on, and the magnet current flows back to capacitor C1 through D1 and D2. At this time, although T1 and T2 have been turned off at time t3, resulting in the current flowing through thyristors S1 and S2 being zero, due to the thyristor's turn-off time t q , so S1 and S2 after t q After a time delay, it is completely turned off naturally at time t4. The voltage on thyristors S1 and S2 during the period t3 to t4 is approximately zero, and the voltage on IGBT switches T1 and T2 is:

[0094]

[0095] Substituting equation (1.5) into equation (1.12), we get:

[0096]

[0097] At t4, S1 and S2 are naturally turned off. After that, during the period from t4 to t5, T1 and T2 and S1 and S2 bear the corresponding voltage according to the voltage-equalizing circuit. Ignoring the voltage drop of diodes D1 and D2, during the period from t4 to t5, u T1,T2 with u S1,S2 satisfy:

[0098]

[0099] where u C1 is the voltage of capacitor C1.

[0100] Due to the internal resistance of the magnet R L Due to the on-resistance of T1 and T2, part of the energy of capacitor C1 is dissipated, resulting in the capacitor voltage u at time t5. C1 (t5) is less than U C1 ,u C1 (t5) Generally meets the following requirements:

[0101]

[0102] Where k generally satisfies 0.9 <k<1。

[0103] Depend on Figure 6 From the switch tube voltage curve and formulas (1.13), (1.14), (1.15) and (1.16), it can be seen that the maximum voltage U that T1 and T2 and S1 and S2 bear during the entire discharge process is T1,T2 (max) and U S1,S2 (max) are:

[0104]

[0105] where t q is the turn-off time of thyristors S1 and S2.

[0106] Since the magnetic current waveform of the repetitive pulse magnetic field generating device provided by the present invention is consistent with that of the conventional repetitive pulse magnetic field generating device during the discharge process, Figure 6 The waveform of the period t2 to t5 also satisfies the formula shown in equation (1.5). Therefore, during the discharge process, the magnet current i L The maximum value is

[0107] Figure 6 The waveform corresponds to a capacitor C1 of 680μF and a rated voltage U C1 is 15kV, the magnet inductance L1 is 200μH, and the magnet resistance R L The resistance ratio n of the voltage equalization circuit is 9, R3 = R1 = 9 × R4 = 9 × R2 = 1 MΩ. Considering the most extreme case, the k value is 1, t q Take 75μs. The withstand voltage value of IGBT switch tubes T1 and T2 and thyristors S1 and S2 is U T1,T2 with U S1,S2 Need to meet the following requirements:

[0108]

[0109]

[0110] At t3, the maximum magnet current flows through T1 and T2 and S1 and S2. From formula (1.8), we know that the maximum allowable current I of T1 and T2 and S1 and S2 is T1,T2 with I S1,S2 All need to be greater than 27.66kA.

[0111] Therefore, if we use Figure 6 Parameter conditions under the waveform, use Figure 2The repetitive pulse magnetic field generating device proposed by the present invention shown in FIG. 1 needs to select a low-side IGBT parallel combination structure switch with a withstand voltage greater than 3.31 kV and a maximum allowable current greater than 27.66 kA. Considering a certain voltage and current margin, a switch structure composed of 9 IGBT switch tubes with a voltage level of 4500 V and an instantaneous current capacity of 3600 A can be selected in parallel to replace Figure 2 At the same time, it is also necessary to select a high-voltage thyristor series combination structure switch with a withstand voltage greater than 15kV and a maximum allowable current greater than 27.66kA. Considering a certain voltage and current margin, a switch structure composed of two thyristors with a voltage level of 8500V and an instantaneous current capacity of 35kA can be selected to replace it. Figure 2 In addition, after connecting the two thyristors in series, the resistance of the voltage-equalizing resistor in parallel at both ends of each thyristor needs to be changed to (Right now ), thereby meeting the series voltage balancing requirement. Thus, the composite switch module is obtained as Figure 7 As shown, it specifically includes: a first switch unit and a second switch unit connected in series; the first switch unit includes: a thyristor S connected in series 1,1 and S 2,1 , and parallel connection to the thyristor S 1,1 The resistance R at both ends 1,1 And in parallel with the thyristor S 2,1 The resistance R at both ends 2,1 The second switch unit includes: a fully controlled switch device group, and a second resistor R connected in parallel at both ends of the fully controlled switch device group 3,1 ; The fully controlled switch device group includes: parallel IGBT switches T 3,1 , T 3,2 ,......,T 3,9 .

[0112] From the above analysis, it can be seen that the voltage borne by the IGBT switch during the entire discharge process of the repetitive pulse magnetic field generating device provided by the present invention is relatively small, most of the high voltage is borne by the thyristor, and the IGBT switch realizes the full control capability of the bridge arm. Therefore, it is feasible to replace the pulse discharge circuit of the high-voltage and large-capacity IGBT switch with a series switch composed of an IGBT switch tube and a thyristor. When the capacitor voltage and the discharge current are large, multiple high-voltage thyristors can be connected in series and in parallel to improve the withstand voltage and current capacity of the bridge arm, and multiple low-side IGBT switches can be connected in parallel to expand its current capacity to match the high current capacity of the high-voltage thyristor. Since the withstand voltage and current capacity of the thyristor are stronger than those of the IGBT, it can be seen from the above example analysis process that under the same capacitor voltage and discharge current, the number of thyristors and IGBTs used in series and parallel in the discharge bridge arm of the present invention is far less than the number of high-voltage IGBTs used in series and parallel in the bridge arm of the traditional discharge circuit. The fewer switches and the avoidance of the use of IGBTs in series make the discharge bridge arm circuit more reliable than the traditional circuit and the structure simpler. At the same time, the combined cost of the large-capacity high-voltage thyristor and the low-side IGBT is lower than that of the large-capacity high-voltage IGBT, and the number of switches used is less, so the entire repetitive pulse magnetic field generating device is more economical. In summary, the repetitive pulse magnetic field generating device proposed in the present invention has more advantages.

[0113] It is worth noting that due to the existence of the resistor voltage-equalizing circuit and the reasonable use of the difference in the turn-on speed of the thyristor and the IGBT switch to control the turn-on time sequence of the thyristor and the low-side IGBT, the voltage borne by the IGBT during the entire discharge process is relatively small, and most of the high voltage is borne by the high-voltage thyristor. Therefore, it is feasible to replace the pulse discharge circuit of the high-voltage and large-capacity IGBT switch with a series switch composed of a low-side IGBT switch tube and a high-voltage thyristor. When the capacitor voltage and discharge current are large, multiple high-voltage thyristors can be connected in series and in parallel to improve the bridge arm withstand voltage and current capacity (the thyristor switching speed is relatively slow, so its series and parallel use has low requirements for switch consistency and does not affect reliability), and at the same time, multiple low-side IGBT switches are connected in parallel to expand their current capacity to match the high current capacity of the high-voltage thyristor (the parallel use of IGBT switches has lower requirements for turn-on consistency than series connection, and the reliability is relatively high). The typical maximum withstand voltage of a single thyristor is 8500V, and the typical value of the instantaneous maximum current carrying capacity of a single thyristor of this withstand voltage level can reach 53.3kA. Since the withstand voltage and current carrying capacity of high-voltage thyristors are stronger than those of high-voltage IGBTs, under the same capacitor voltage and discharge current, the number of thyristors and low-side IGBTs used in series and parallel in the bridge arm of the discharge circuit of the present invention is far less than the number of high-voltage IGBTs used in series and parallel in the bridge arm of the traditional discharge circuit. Fewer switches and avoiding the use of IGBTs in series make the bridge arm more reliable than the traditional circuit. At the same time, the combined cost of high-voltage thyristors and low-side IGBTs is lower than that of high-voltage IGBTs, and the number of switches used is less, so the entire discharge circuit is more economical. In summary, the high-voltage and high-current repetitive pulse discharge circuit proposed in the present invention has more advantages.

[0114] In a third aspect, the present invention provides a method for generating a repetitive pulsed magnetic field, comprising: repeatedly performing an operation of generating a unidirectional pulsed magnetic field, thereby generating a repetitive pulsed magnetic field;

[0115] The operation of generating a unidirectional pulsed magnetic field includes:

[0116] When all the fully controlled switch devices and thyristors in the bridge discharge circuit are in the off state, the switch K1 is closed until the charger charges the energy storage capacitor C1 to the required voltage, and then the switch K1 is opened; at the same time, a driving signal for controlling the conduction of the fully controlled switch devices and thyristors is sent to the fully controlled switch devices and thyristors, and the energy storage capacitor C1 starts to discharge; during the discharge process of the energy storage capacitor C1, current begins to be generated on the inductive load in the bridge discharge circuit; when the current on the inductive load reaches the current peak, all the fully controlled switch devices are turned off at the same time, and then all the thyristors are automatically turned off due to the loss of the holding current, and the current on the inductive load is continued through the diodes of the two discharge bridge arms in the bridge discharge circuit, and continues to decrease until it reaches zero; in this process, a unidirectional pulse current is generated on the inductive load, and a unidirectional pulse magnetic field is generated accordingly;

[0117] Among them, after the energy storage capacitor C1 is connected in parallel with the bridge discharge circuit, it is connected to both ends of the charger through the switch K1; the bridge discharge circuit is the bridge discharge circuit provided by the first aspect of the present invention; at the initial moment, each fully controlled switch device and each thyristor are disconnected.

[0118] The related technical solution is the same as the bridge discharge circuit provided in the first aspect of the present invention, and will not be described in detail here.

[0119] In a fourth aspect, the present invention provides an electronic device, comprising: a memory and a processor, wherein the memory stores a computer program, and when the processor executes the computer program, the method for generating a repetitive pulsed magnetic field provided in the third aspect of the present invention is executed.

[0120] The related technical solution is the same as the repeated pulse magnetic field generation method provided in the third aspect of the present invention, and will not be described in detail here.

[0121] In a fifth aspect, the present invention further provides a computer-readable storage medium, which includes a stored computer program, wherein when the computer program is executed by a processor, the device where the storage medium is located is controlled to execute the repetitive pulse magnetic field generation method provided in the third aspect of the present invention.

[0122] The related technical solution is the same as the repeated pulse magnetic field generation method provided in the third aspect of the present invention, and will not be described in detail here.

[0123] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A bridge discharge circuit, characterized in that: include: An inductive load, and a first discharge bridge arm and a second discharge bridge arm connected in parallel; the first discharge bridge arm and the second discharge bridge arm both include a composite switch module and a diode connected in series; The composite switch module comprises: a first switch unit and a second switch unit connected in series; the first switch unit comprises one or more thyristors connected in series, and a first resistor connected in parallel at both ends of each thyristor; the second switch unit comprises: a fully controlled switch device group, and a second resistor connected in parallel at both ends of the fully controlled switch device group; the fully controlled switch device group comprises: one or more fully controlled switch devices connected in parallel; The negative end of the fully controlled switch device serves as the A end of the composite switch module, the positive end is connected to the cathode of the first switch unit, and the anode of the first switch unit serves as the B end of the composite switch module; The cathode of the diode in the first discharge bridge arm is connected to the A end of the composite switch module in the first discharge bridge arm, and the anode is connected to the A end of the composite switch module in the second discharge bridge arm; the anode of the diode in the second discharge bridge arm is connected to the B end of the composite switch module in the second discharge bridge arm, and the cathode is connected to the B end of the composite switch module in the first discharge bridge arm; the two ends of the inductive load are respectively connected to the cathode of the diode in the first discharge bridge arm and the anode of the diode in the second discharge bridge arm.

2. The bridge discharge circuit according to claim 1, characterized in that: The fully-controlled switching device is an IGBT; the negative terminal of the fully-controlled switching device is the emitter of the IGBT, and the positive terminal is the collector of the IGBT.

3. The bridge discharge circuit according to claim 1, characterized in that: The fully-controlled switching device is an NMOS tube or a PMOS tube; when the fully-controlled switching device is an NMOS tube, the negative end of the fully-controlled switching device is the source of the NMOS tube, and the positive end is the drain of the NMOS tube; when the fully-controlled switching device is a PMOS tube, the negative end of the fully-controlled switching device is the drain of the PMOS tube, and the positive end is the source of the PMOS tube.

4. The bridge discharge circuit according to claim 1, characterized in that: The inductive load is a magnetic coil.

5. The bridge discharge circuit according to any one of claims 1 to 4, characterized in that: The thyristor is an electrically controlled unidirectional thyristor or a light-controlled unidirectional thyristor.

6. A repetitive pulse magnetic field generating device, characterized in that: include: A controller, a charger, an energy storage capacitor C1, a switch K1 and a bridge discharge circuit as described in any one of claims 1 to 5; After the energy storage capacitor C1 is connected in parallel with the bridge discharge circuit, it is connected to both ends of the charger through the switch K1; The controller is used to repeatedly perform the operation of generating a unidirectional pulsed magnetic field, thereby generating a repeated pulsed magnetic field; The operation of generating a unidirectional pulsed magnetic field comprises: When all the fully controlled switch devices and thyristors in the bridge discharge circuit are in the off state, the switch K1 is closed until the charger charges the energy storage capacitor C1 to the required voltage, and then the switch K1 is opened; at the same time, a drive signal for controlling the conduction of the fully controlled switch devices and the thyristors is sent to each of the fully controlled switch devices and the thyristors, and the energy storage capacitor C1 starts to discharge; during the discharge process of the energy storage capacitor C1, current begins to be generated on the inductive load in the bridge discharge circuit; when the current on the inductive load reaches the current peak, all the fully controlled switch devices are turned off at the same time, and then each of the thyristors is automatically turned off due to the loss of the holding current, and the current on the inductive load is continued through the diodes of the two discharge bridge arms in the bridge discharge circuit, and continues to decrease until it reaches zero; in this process, a unidirectional pulse current is generated on the inductive load, and a unidirectional pulse magnetic field is generated accordingly.

7. The repetitive pulse magnetic field generating device according to claim 6, characterized in that: Also includes: Discharge current sensor; The discharge current sensor is used to detect the current on the inductive load and transmit the current to the controller.

8. A method for generating a repetitive pulsed magnetic field, characterized in that: include: Repeating the operation of generating a unidirectional pulsed magnetic field to generate a repetitive pulsed magnetic field; The operation of generating a unidirectional pulsed magnetic field comprises: When all the fully controlled switch devices and thyristors in the bridge discharge circuit are in the off state, the switch K1 is closed until the charger charges the energy storage capacitor C1 to the required voltage, and then the switch K1 is opened; at the same time, a driving signal for controlling the conduction of the fully controlled switch devices and the thyristors is sent to each of the fully controlled switch devices and the thyristors, and the energy storage capacitor C1 starts to discharge; during the discharge process of the energy storage capacitor C1, a current starts to be generated on the inductive load in the bridge discharge circuit; when the current on the inductive load reaches the current peak, all the fully controlled switch devices are turned off at the same time, and then each of the thyristors is automatically turned off due to the loss of the holding current, and the current on the inductive load is continued through the diodes of the two discharge bridge arms in the bridge discharge circuit, and continues to decrease until it reaches zero; in this process, a unidirectional pulse current is generated on the inductive load, and a unidirectional pulse magnetic field is generated accordingly; Among them, after the energy storage capacitor C1 is connected in parallel with the bridge discharge circuit, it is connected to both ends of the charger through the switch K1; the bridge discharge circuit is the bridge discharge circuit according to any one of claims 1-5.

9. An electronic device, characterized in that: include: A memory and a processor, wherein the memory stores a computer program, and the processor executes the method for generating a repetitive pulsed magnetic field according to claim 8 when executing the computer program.

10. A computer-readable storage medium, the computer-readable storage medium comprising a stored computer program, wherein: When the computer program is executed by the processor, the device where the storage medium is located is controlled to execute the repetitive pulse magnetic field generating method according to claim 8.

Images