Active resonant magnetic reset method for unipolar pulse transformer

Abstract

The application discloses an active resonant magnetic reset method of a unipolar pulse transformer, and belongs to the technical field of pulse power. The unipolar pulse transformer is used for driving each minimum working unit of a unipolar pulse power supply. The method comprises the following steps: measuring equivalent leakage inductance, equivalent excitation inductance and equivalent turn ratio of the unipolar pulse transformer; establishing an approximate magnetic hysteresis loop of a magnetic core of the unipolar pulse transformer and evaluating coercive force; installing controllable RC damping circuits in parallel at each primary side port of the unipolar pulse transformer and connecting power diodes in series on secondary side windings; calculating optimal conduction time of a reset MOSFET switch; and controlling the conduction time of the reset MOSFET switch rapidly after a main MOSFET switch is turned off, so that magnetic reset of the unipolar pulse transformer is realized. The method solves the problems of safety hazards, energy efficiency loss and system complexity of a traditional scheme by introducing a small amount of low-cost additional circuits and a cooperative control strategy.

Description

Technical Field

[0001] The present invention relates to the technical field of pulse power, and in particular to an active resonant magnetic resetting method for a unipolar pulse transformer. Background Art

[0002] Pulse generators based on unipolar pulse transformers can generate high-power pulses at specific frequencies and have found widespread application in industries such as biomedicine and semiconductor manufacturing. Compared to traditional MARX-type pulse generators and direct chopping-type pulse generators, solutions based on unipolar pulse transformers offer higher power density and energy transfer efficiency.

[0003] This type of pulse generator is typically composed of a cascade of multiple minimum working units, each of which is centered around a unipolar pulse transformer. Under periodic unipolar pulse excitation, the unipolar pulse transformer's magnetic core faces a critical challenge: magnetic resetting. Due to the inherent nonlinear hysteresis characteristics of soft magnetic materials, the residual magnetic flux generated during the excitation process accumulates within the core, ultimately leading to magnetic saturation. Magnetic saturation not only causes output pulse amplitude attenuation and severe waveform distortion, but also significantly reduces the system's energy transmission efficiency and limits the device's ability to sustain repeated operation.

[0004] Therefore, developing an efficient magnetic reset method to solve the problem of residual magnetism accumulation in the pulse transformer core has become a key demand to promote the technological development of related industries. Summary of the Invention

[0005] In order to solve the problems in the prior art, the present invention provides an active resonant magnetic reset method for a unipolar pulse transformer.

[0006] The technical solutions of the present invention are as follows:

[0007] The present invention discloses an active resonant magnetic reset method for a unipolar pulse transformer. The unipolar pulse transformer is used to drive the minimum working unit of a unipolar pulse power supply. The unipolar pulse power supply is composed of a plurality of identical minimum working units connected in cascade, each minimum working unit including a unipolar pulse transformer. The active resonant magnetic reset method comprises the following steps:

[0008] S1. Establish the anti-corrosion of the existing unipolar pulse transformer Type model, the model parameters include equivalent leakage inductance, equivalent excitation inductance and equivalent turns ratio;

[0009] S2. Build a dynamic test circuit, test and synchronously record the primary-side input current and primary-side input voltage, fit the approximate hysteresis loop curve of the unipolar pulse transformer core, and evaluate the coercive force;

[0010] S3, parallel controllable RC damping circuit at each unipolar pulse transformer primary side port, power diode is installed in series on secondary side winding; the controllable RC damping circuit includes resonance capacitor , reset resistor and reset MOSFET switch ;

[0011] S4, based on the improved topology, an equivalent circuit model is established, corresponding mathematical expression is constructed, and the optimal conduction time of reset MOSFET switch is calculated ; after the main MOSFET switch is turned off, the conduction time of reset MOSFET switch is controlled quickly , so that the magnetic reset of unipolar pulse transformer is realized.

[0012] Further, the step S3 is based on the data pretreated by step S1 and step S2 to design controllable RC damping circuit; the step S3 is specifically:

[0013] S31, the maximum value of resonance capacitor is determined by the following formula:

[0014] ;

[0015] Wherein, is the operating frequency of existing unipolar pulse power supply, is the design scaling factor of resonance capacitor, is the equivalent leakage inductance, is the equivalent excitation inductance;

[0016] S32, the maximum value of reset resistor is determined by the following formula:

[0017] ;

[0018] Wherein, is the design scaling factor of reset resistor;

[0019] S33, the controllable RC damping circuit is assembled into a module and installed at each unipolar pulse transformer primary side port;

[0020] S34, the power diode is installed on the secondary side winding of each unipolar pulse transformer.

[0021] Further, the step S4 specifically includes:

[0022] ​​S41, based on the main MOSFET switch and reset MOSFET switches The switching state and current waveform of the unipolar pulse generation cycle are divided into 5 working stages;

[0023] S42, construct leakage inductance current of the first, second, third and fourth working stages respectively and the magnetizing inductor current Mathematical expressions and calculation of the end times of the second, third and fourth working stages;

[0024] S43, subtracting the end time of the fourth working stage from the end time of the first working stage to obtain the reset MOSFET switch Optimal on-time ;

[0025] S44, will As a theoretical guide, the controller is written in the main MOSFET switch Quickly control the reset MOSFET switch after shutdown Activate time to achieve magnetic reset of the unipolar pulse transformer.

[0026] Furthermore, in step S42, calculating the end time of the fourth working stage includes:

[0027] First, the excitation inductance current and the leakage inductance current at the end of the first working stage are calculated based on the mathematical expressions of the leakage inductance current and the excitation inductance current in the first working stage, that is, the initial values ​​of the excitation inductance current and the leakage inductance current at the initial moment of the second working stage are obtained;

[0028] Then, based on the initial values ​​of the excitation inductance current and the leakage inductance current in the second working stage, mathematical expressions of the leakage inductance current and the excitation inductance current in the second working stage are constructed. Then, using the constraint condition that the excitation inductance current and the leakage inductance current are equal at the end of the second working stage, the end time of the second working stage is calculated, and the excitation inductance current and the leakage inductance current at the end of the second working stage are calculated, that is, the initial values ​​of the excitation inductance current and the leakage inductance current in the third working stage are obtained.

[0029] Finally, based on the initial values ​​of the excitation inductance current and leakage inductance current in the third working stage, the mathematical expressions of the leakage inductance current and excitation inductance current in the third and fourth working stages are constructed. Then, the series resonant current of the resonant capacitor, leakage inductance and excitation inductance at the end of the fourth working stage is This constraint condition calculates the end time of the fourth working stage; where, is the coercive force, is the effective magnetic path length of the core of the unipolar pulse transformer, is the equivalent turns ratio; since the third and fourth working stages are the same resonant process, the mathematical expressions of the leakage inductance current and the excitation inductance current in the third working stage are the same as those in the fourth working stage.

[0030] Compared with the traditional unipolar pulse transformer magnetic reset method, the present invention has the following core advantages:

[0031] 1. Low-cost, highly integrated, non-invasive hardware solution: This invention designs a non-invasive magnetic reset hardware device. By connecting a controllable RC damping circuit module in parallel with the primary port and a power diode in series with the secondary winding, this device effectively eliminates the problem of residual magnetism accumulation in the magnetic core caused by unipolar pulse excitation without modifying the existing circuit and transformer structure. Compared to traditional magnetic reset methods that rely on an external DC power supply, this solution significantly reduces hardware modification costs, improves system integration, and achieves higher reset efficiency.

[0032] 2. Innovative Resonant Energy Transfer Reset Mechanism: Based on the aforementioned non-invasive magnetic reset hardware device, this invention proposes a resonant reset technology. This technology utilizes the leakage inductance and magnetizing inductance of a unipolar pulse transformer, along with an introduced resonant capacitor, to form an energy exchange loop. Through a complex LC resonance process, the reactive energy accumulated during the magnetization period is transferred to the resonant capacitor for storage. This energy is then fed back into the transformer as a reverse current, achieving a magnetic core reset.

[0033] 3. Model-based software and hardware collaborative optimization method: For the unipolar pulse power supply equipped with the above-mentioned non-invasive magnetic reset hardware device, the present invention establishes an equivalent circuit model covering the complete pulse generation cycle and its corresponding mathematical expression. Using this model, the theoretical optimal time for the reset MOSFET switch to turn on can be calculated. , directly guide the implementation of control strategies and greatly improve installation and configuration efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 Schematic diagram of the process of the present invention;

[0035] Figure 2 A topological diagram of an improved unipolar pulse power supply provided in an embodiment of the present invention;

[0036] Figure 3 It is a timing waveform diagram of key signals during the implementation of the present invention;

[0037] Figure 4 for Figure 2 Schematic diagram of the five stages of the minimum working unit in one pulse cycle, (a)-(e) are the first stage to the fifth stage respectively;

[0038] Figure 5 Schematic diagram of the prototype and test platform of the embodiment;

[0039] Figure 6 This is a reset process diagram of the unipolar pulse power supply of Example 1;

[0040] Figure 7 This is the continuous working performance diagram of the unipolar pulse power supply of Example 2. DETAILED DESCRIPTION

[0041] The present invention will be further described and illustrated below in conjunction with specific embodiments. The embodiments are merely illustrative of the present disclosure and do not limit its scope. The technical features of the various embodiments of the present invention may be combined accordingly, provided that there is no conflict between them.

[0042] The present invention aims to provide an active resonant magnetic reset method for a unipolar pulse transformer. The unipolar pulse transformer is used to drive the minimum working unit of a unipolar pulse power supply. The unipolar pulse power supply is composed of a cascade of several minimum working units with consistent performance, each of which contains a unipolar pulse transformer. This method introduces a small amount of low-cost additional circuitry and a coordinated control strategy to an existing unipolar pulse power supply. This method utilizes the reactive energy stored during the excitation process of the unipolar pulse transformer to autonomously achieve a magnetic reset function, thereby addressing the safety risks, energy efficiency losses, and system complexity associated with traditional solutions.

[0043] In an embodiment of the present invention, an active resonant magnetic reset method for a unipolar pulse transformer is provided. Figure 1 Shown, including:

[0044] S1, establish the reverse of the existing unipolar pulse transformer The model parameters include equivalent leakage inductance, equivalent magnetizing inductance and equivalent turns ratio.

[0045] Build an anti-corrosion model for the applied unipolar pulse transformer. The specific method of the model is as follows: First, short-circuit the secondary winding of the unipolar pulse transformer, use the LCR digital bridge to measure the inductance of the primary winding, and record the measured value as the equivalent leakage inductance Next, open the secondary winding of the unipolar pulse transformer and measure the primary winding inductance again with the LCR digital bridge. The measured value is recorded as the equivalent leakage inductance. and equivalent magnetizing inductance The sum of the two can be simply converted to the equivalent excitation inductance. Finally, considering the tight coupling characteristics of the unipolar pulse transformer, the equivalent turns ratio is approximately expressed by the known physical turns ratio of the unipolar pulse transformer. .

[0046] S2: Build a dynamic test circuit, test and synchronously record the primary side input current and primary side input voltage, fit the approximate hysteresis loop curve of the unipolar pulse transformer core and evaluate the coercive force. :

[0047] S21, a bipolar fast pulse excitation signal is periodically introduced into the primary port of the unipolar pulse transformer, and the Rogowski coil current probe measures the primary input current signal. , use an isolated voltage probe to measure the primary side input voltage signal ;

[0048] S22, using the measured primary side input current signal Derivation of transformer magnetic field strength .

[0049] Specifically, by measuring the core size of the unipolar pulse transformer and performing geometric analysis, the effective magnetic path length of the corresponding core can be obtained. According to the linear relationship shown in formula (1), the corresponding magnetic field strength can be obtained The time domain expression of is:

[0050] (1)

[0051] S23, using the measured primary side input voltage signal Derivation of transformer magnetic induction intensity .

[0052] Specifically, by measuring the core size of the unipolar pulse transformer and performing geometric analysis, the effective magnetic flux cross-sectional area of ​​the corresponding core can be obtained. According to the linear relationship shown in formula (2), the corresponding magnetic induction intensity can be obtained The time domain expression of is:

[0053] (2)

[0054] S24, fitting the approximate hysteresis curve of the core and determining the coercivity of the existing unipolar pulse transformer .

[0055] Specifically, the calculation step is 1 / 20 of the bipolar fast pulse excitation signal period, and sampling is performed within a complete pulse period to obtain the corresponding magnetic field strength. and magnetic induction intensity sequence;

[0056] Furthermore, the magnetic field strength obtained The sequence data is the X-axis coordinate, magnetic induction intensity The sequence data is the Y-axis data. Draw discrete points on a plane;

[0057] Furthermore, MATLAB software is used to perform smooth curve fitting on the discrete coordinate points obtained above to obtain the approximate hysteresis loop of the unipolar pulse transformer core;

[0058] Furthermore, the magnetic induction intensity is determined on the smooth approximate hysteresis loop obtained by the above fitting. Magnetic field strength restored to 0T , defined as the coercive force .

[0059] S3, connect a controllable RC damping circuit in parallel to the primary port of each unipolar pulse transformer, install a power diode D in series on the secondary winding, and improve the circuit topology as follows Figure 2 As shown, Figure 2 The unipolar pulse power supply is composed of n minimum working units in cascade.

[0060] S31, resonant capacitor The choice of directly determines the LC resonance period, which in turn affects the effective time of magnetic reset. Its maximum value can be determined by formula (3), where: is the operating frequency of the existing unipolar pulse power supply, is the design scaling factor of the resonant capacitor, which is generally selected as 0.1%;

[0061] (3)

[0062] S32, reset resistor The choice of determines the resonant capacitor after the magnetic reset is completed. The maximum value of the remaining energy reset time can be determined by formula (4), where: is the design scaling factor of the reset resistor, which is generally selected as 0.1%.

[0063] (4)

[0064] S33, assembling the controllable RC damping circuit into modules and installing them on the primary side ports of each existing unipolar pulse transformer.

[0065] Specifically, non-inductive film capacitors that meet the preset withstand voltage requirements are selected, and a resonant capacitor matrix that meets the preset resonant capacitor capacitance requirements is constructed through series-parallel combination.

[0066] Furthermore, a non-inductive resistor that meets the preset reset resistor value requirement is selected and connected in parallel across the resonant capacitor matrix to obtain an RC parallel branch;

[0067] Furthermore, the above RC parallel branch is connected to the reset MOSFET switch The drain is directly connected and packaged into a controllable RC damping circuit module;

[0068] Furthermore, the dedicated module is directly connected in parallel to the primary side port of the unipolar pulse transformer corresponding to each minimum working unit, wherein the reset MOSFET switch The source of the main MOSFET switch is the smallest working unit The drain is directly connected.

[0069] S34, the power diode They are respectively installed on the secondary winding of each unipolar pulse transformer.

[0070] Specifically, the power diode The diode is connected in series to the secondary winding of the transformer of each minimum working unit, wherein the conduction direction of the diode is consistent with the output direction of the pulse current.

[0071] S4, based on the improved topology, establish an equivalent circuit model, construct the corresponding mathematical expression, and calculate the reset MOSFET switch Optimal on-time.

[0072] S41, based on the main MOSFET switch and reset MOSFET switches The switching state and current waveform are divided into 5 working stages;

[0073] Specifically, the key waveform timing waveform of a complete unipolar pulse generation cycle is as follows: Figure 3 As shown, Figure 3 in and Represent the driving waveforms of the main MOSFET switch and the reset MOSFET switch respectively, Indicates the voltage acting on the equivalent load of the minimum working unit, represents the magnetizing inductor current, Represents the leakage inductance current. The corresponding equivalent circuit diagram is as follows Figure 4 As shown in (a) in the figure, it is defined as the first working stage. 、 are the start and end times of the unipolar pulse respectively; The corresponding equivalent circuit diagram is as follows Figure 4 As shown in (b), it is defined as the second working stage, which represents the resonance stage of the leakage inductance and the resonant capacitor; The corresponding equivalent circuit diagram is as follows Figure 4 As shown in (c), it is defined as the third working stage, which represents the series resonance stage of leakage inductance, excitation inductance and resonant capacitor, and the resonant current is positive in this stage and Always cross the 0A working point; The corresponding equivalent circuit diagram is as follows Figure 4 As shown in (d), it is defined as the fourth working stage, which indicates the series resonance stage of leakage inductance, excitation inductance and resonant capacitor, and the resonant current is negative in this stage. Reset MOSFET switch required by the method of the present invention Closing moment; The corresponding equivalent circuit diagram is as follows Figure 4 As shown in (e) in the figure, it is defined as the fifth working stage, in which: is the starting time of the next unipolar pulse generation cycle; Figure 4 The black part in the diagram represents the operating circuit and effective components of the minimum working unit, and the blue part represents the non-operating circuit and bypass components of the minimum working unit.

[0074] S42, constructing leakage inductance current from the first working stage to the fourth working stage respectively and the magnetizing inductor current Mathematical expressions.

[0075] Specifically, the steady-state magnetizing inductor current in the first working stage is and leakage current The mathematical expressions are formulas (5) and (6):

[0076] (5)

[0077] (6)

[0078] in, is the equivalent rated input voltage of the minimum working unit, is the equivalent rated output load of the minimum working unit, both of which can be obtained from the existing unipolar pulse power supply indicators.

[0079] Furthermore, the magnetizing inductor current in the second working stage and leakage current The constraint equation is formula (7):

[0080] (7)

[0081] in, 、 、 and are all intermediate parameters. , , , ; is the vector representation of the magnetizing inductance current and the leakage inductance current, To calculate the above constraint equations, the initial values ​​must be confirmed in advance. The necessary initial values ​​are summarized in equations (8), (9) and (10):

[0082] (8)

[0083] (9)

[0084] (10)

[0085] in, for The magnetizing inductor current at time for The leakage inductance current at the moment can be calculated by formulas (5) and (6). It indicates the rated current acting on the equivalent load of the minimum working unit. Its value can be obtained by looking up the existing unipolar pulse power supply indicators.

[0086] In this stage, the leakage inductance current decays rapidly and the magnetizing inductance current increases slowly. The moments completely coincide, and the constraint equation can be expressed as:

[0087] (11)

[0088] in, is the critical value of the second and third working stages. Substituting this constraint equation into formula (7) (8) (9) (10) we can calculate .

[0089] Furthermore, in the third working stage, the excitation inductance Loss of clamping, starts with magnetizing inductance and resonant capacitor participate in series resonance together, so the excitation inductor current and leakage current Completely coincident, its constraint equation is:

[0090] (12)

[0091] To calculate the above constraint equations, the initial values ​​must be confirmed in advance. The necessary initial values ​​are summarized in equations (13) and (14):

[0092] (13)

[0093] (14)

[0094] in, is the current flowing through the resonant capacitor. During this period, it is related to the leakage current Total overlap.

[0095] exist At this moment, the series resonant current of the resonant capacitor, leakage inductance and excitation inductance passes through Working point, its constraint equation can be expressed as:

[0096] (15)

[0097] Substituting the constraint equation into formula (12) (13) (14) yields .

[0098] Furthermore, in the fourth working stage, the resonant current of the resonant capacitor, leakage inductance and excitation inductance begins to increase in the reverse direction. At this time, the resonant current can only be conducted through the main channel of the reset MOSFET switch. The condition for magnetic reset of the unipolar pulse transformer is that the reverse current can completely offset the residual magnetic flux of the magnetic core, that is, the reverse current reaches:

[0099] (16)

[0100] Corresponding The constraints for time calculation are:

[0101] (17)

[0102] Substituting this constraint into formula (12), (13) and (14) yields .

[0103] S43, sum up the time used, and get Optimal on-time :

[0104] (18)

[0105] S44, will As a theoretical guide, write the controller so that it switches the main MOSFET Quickly control the reset MOSFET switch after shutdown Activate time, i.e. reset MOSFET switch It turns on from time t1 and lasts until Always closed.

[0106] In order to verify the effectiveness of the magnetic reset method proposed in the present invention, a unipolar pulse power supply prototype composed of two minimum working units in cascade was designed and manufactured. The rated DC input voltage of each minimum working unit is 100V, the rated output pulse voltage is 100V, the rated pulse output current is 50A, and the rated maximum output pulse width is 5μs. Correspondingly, the rated output pulse voltage of the unipolar pulse power supply prototype is 200A, the rated pulse output current is 50A, and the rated maximum output pulse width is 5μs. Example unipolar pulse power supply and its test equipment are as follows Figure 5 shown.

[0107] Apply the method proposed in step S1 to construct the minimum working unit of the embodiment, the single-polarity pulse transformer. Model, where the equivalent leakage inductance The equivalent magnetizing inductance is 0.35μH 63.20μH, equivalent turns It is 4:4.

[0108] Apply the method proposed in step S2 to measure the approximate hysteresis curve of the minimum working unit unipolar pulse transformer of the embodiment and analyze its coercive force Corresponding reset current is 2.0A.

[0109] Applying the method proposed in step S3, based on the obtained model parameters and the minimum reset current, this embodiment sets the resonant capacitor The capacitance is set to 6μF, which is obtained by assembling six 1μF multilayer ceramic capacitors in parallel. The resistance value is set to 1kΩ, which is directly assembled from a thick film resistor. With the main MOSFET switch Same model. Power diode Choose a general-purpose product with a withstand voltage of 300V and a current capacity of 100A.

[0110] Apply the method proposed in step S4 to calculate the reset MOSFET switch Optimal on-time The on-time is 43.7μs, a certain control margin is set, and the final on-time is set to 45μs.

[0111] Experiment 1: Detailed description of the unipolar pulse power supply reset process

[0112] set up Resistive output load, 5μs pulse width experimental conditions, the test results are as follows Figure 6 As shown. Among them, Figure 6 (a) in the figure introduces the five operation stages mentioned in step S4 analysis. Figure 6(b) shows the reset MOSFET switch during the magnetic reset process of the unipolar pulse transformer. The driving signal and leakage current signal waveforms are shown in Figure 2. After the preset 45μs reset MOSFET switch After the on-time, the leakage current The current decays from 6.3 A to -2.2 A in a quasi-sinusoidal trend, at which point the reverse current fully meets the magnetic reset condition. The above experimental results demonstrate the effectiveness of the present invention and the correctness of the theoretical analysis.

[0113] Experiment 2: Analysis of the continuous working state of the unipolar pulse power supply in the embodiment

[0114] Based on Experiment 1, the unipolar pulse power supply prototype of the embodiment was adjusted to run continuously at a repetition frequency of 10 Hz for 100 times, and the key waveform of the first pulse generation process was recorded. Figure 7 (a) in the figure records the key waveform of the 100th pulse generation process. Figure 7 (b) in the figure. By comparison, after 100 unipolar pulse excitations, the operating state of the unipolar pulse power supply in the embodiment does not shift significantly, and the pulse voltage acting on the load is Both are close to the ideal 200V, pulse current Both are 50A, leakage current The maximum value is 56 A. The experimental results show that under the condition of 10 Hz repetition frequency, the unipolar pulse transformer of the minimum working unit of the embodiment does not suffer from magnetic saturation failure, which indirectly shows that the unipolar pulse transformer is well magnetically reset after each pulse action, further proving the effectiveness of the present invention.

[0115] Without changing the existing circuit and transformer structure, the present invention effectively eliminates the problem of residual magnetism accumulation in the magnetic core caused by unipolar pulse excitation. Compared with the traditional magnetic reset method that relies on an external DC power supply, this solution significantly reduces the hardware modification cost, improves the system integration, and achieves higher reset efficiency. In addition, the leakage inductance, excitation inductance and introduced resonant capacitor of the unipolar pulse transformer are used to form an energy exchange circuit to realize the magnetic core magnetic reset function. The present invention also establishes an equivalent circuit model covering the complete pulse generation cycle and its corresponding mathematical expression. Using this model, the theoretical optimal time for the reset MOSFET switch to turn on can be calculated. , directly guide the implementation of control strategies and greatly improve installation and configuration efficiency.

[0116] The accompanying drawings illustrating the embodiments of the present invention serve to more clearly illustrate the objectives, technical solutions, and advantages of the present invention. It should be noted that the specific embodiments described herein are intended only to illustrate the present invention and are not intended to limit the present invention. Any equivalent substitutions, modifications, and the like made within the methodologies and principles provided by the present invention are intended to be included within the scope of protection of the present invention.

Claims

1. An active resonant magnetic reset method for a unipolar pulse transformer, wherein the unipolar pulse transformer is used to drive the minimum working unit of a unipolar pulse power supply, the unipolar pulse power supply being composed of a plurality of identical minimum working units connected in cascade, each minimum working unit comprising a unipolar pulse transformer; characterized in that: The active resonant magnetic reset method comprises the following steps: S1. Establish the anti-corrosion of the existing unipolar pulse transformer Type model, the model parameters include equivalent leakage inductance, equivalent excitation inductance and equivalent turns ratio; S2. Build a dynamic test circuit, test and synchronously record the primary-side input current and primary-side input voltage, fit the approximate hysteresis loop curve of the unipolar pulse transformer core, and evaluate the coercive force; S3, connect a controllable RC damping circuit in parallel to the primary port of each unipolar pulse transformer, and install a power diode in series on the secondary winding; the controllable RC damping circuit includes a resonant capacitor , reset resistor and reset MOSFET switches ; S4. Establish an equivalent circuit model based on the improved topology, construct the corresponding mathematical expression, and calculate the reset MOSFET switch Optimal on-time ; In the main MOSFET switch Quickly control the reset MOSFET switch after shutdown conduction time, thereby achieving magnetic reset of the unipolar pulse transformer; In step S1, the secondary winding of the unipolar pulse transformer is short-circuited, and the inductance of the primary winding is measured. The measured value is recorded as the equivalent leakage inductance. ; Open the secondary winding of the unipolar pulse transformer and measure the primary winding inductance again. The measured value is recorded as the equivalent leakage inductance. and equivalent magnetizing inductance The sum of the equivalent excitation inductance is obtained ;Equivalent turns ratio Expressed by the physical turns ratio of a unipolar pulse transformer; The specific sub-steps of step S2 are as follows: S21, periodically introduce a bipolar fast pulse excitation signal into the primary port of the unipolar pulse transformer and measure the primary input current signal , measure the primary side input voltage signal ; S22, using the measured primary side input current signal Derivation of transformer magnetic field strength ; S23, using the measured primary side input voltage signal Derivation of transformer magnetic induction intensity ; S24, fitting the approximate hysteresis curve of the core to analyze the coercivity of the existing unipolar pulse transformer ; The step S3 designs a controllable RC damping circuit based on the data pre-processed in the steps S1 and S2; the step S3 is specifically as follows: S31, resonant capacitor The maximum value Determined by the following formula: ； in, is the operating frequency of the existing unipolar pulse power supply, is the design scaling factor for the resonant capacitor, is the equivalent leakage inductance, is the equivalent excitation inductance; S32, reset resistor The maximum value Determined by the following formula: ； in, is the design scaling factor for the reset resistor; S33, assembling a controllable RC damping circuit into a module and installing it on the primary side port of each unipolar pulse transformer; S34, the power diode They are installed on the secondary windings of each unipolar pulse transformer respectively; In step S33, the specific method of assembling and installing the controllable RC damping circuit is: First, non-inductive film capacitors that meet the preset withstand voltage requirements are selected, and a resonant capacitor matrix that meets the preset resonant capacitor capacitance requirements is constructed through series-parallel combination. Next, a non-inductive resistor that meets the preset reset resistor value requirement is selected and connected in parallel across the resonant capacitor matrix to obtain an RC parallel branch. Then, connect the above RC parallel branch to the reset MOSFET switch The drain is directly connected and packaged into a dedicated module; Finally, the dedicated module is directly connected in parallel to the primary side port of the unipolar pulse transformer corresponding to each minimum working unit, where the reset MOSFET switch The source of the main MOSFET switch is the smallest working unit available. The drain is directly connected; In step S34, the specific method of assembling and installing the power diode is: installing the power diode D in series on the secondary winding of the unipolar pulse transformer of each minimum working unit, wherein the conduction direction of the diode is consistent with the pulse current output direction.

2. The active resonant magnetic reset method according to claim 1, characterized in that: In step S22, the transformer magnetic field strength The derivation method is: measure the core size of the unipolar pulse transformer and perform geometric analysis to obtain the effective magnetic path length of the corresponding core , the corresponding magnetic field strength is obtained through the linear relationship shown in the following formula The time domain expression of is: ； In step S23, the transformer magnetic induction intensity The derivation method is: measure the core size of the unipolar pulse transformer and perform geometric analysis to obtain the effective flux cross-sectional area of ​​the corresponding core , the corresponding magnetic induction intensity is obtained through the linear relationship shown in the following formula The time domain expression of is: 。 3. The active resonant magnetic reset method according to claim 1, wherein: The step S24 is specifically as follows: first, taking 1 / 20 of the bipolar fast pulse excitation signal cycle as the calculation step, sampling within a complete pulse cycle, and obtaining the corresponding magnetic field intensity H and magnetic induction intensity B sequences respectively; then, using the obtained magnetic field intensity H sequence data as the X-axis coordinate and the magnetic induction intensity B sequence data as the Y-axis data, discrete points are drawn on the HB plane; then, smooth curve fitting is performed on the above discrete coordinate points to obtain the approximate hysteresis loop of the unipolar pulse transformer core; finally, on the approximate hysteresis loop obtained by the above fitting, the magnetic field intensity H at the moment when the magnetic induction intensity B recovers to 0T is determined, and it is defined as the coercive force .

4. The active resonant magnetic reset method according to claim 1, wherein: The specific sub-steps of step S4 include: S41, based on the main MOSFET switch and reset MOSFET switches The switching state and current waveform of the unipolar pulse generation cycle are divided into 5 working stages; S42, constructing mathematical expressions of the leakage inductance current and the magnetizing inductance current of the first, second, third and fourth working stages respectively, and calculating the end time of the fourth working stage; S43, subtracting the end time of the fourth working stage from the end time of the first working stage to obtain the reset MOSFET switch Optimal on-time ; S44, will As a theoretical guide, the controller is written in the main MOSFET switch Quickly control the reset MOSFET switch after shutdown Activate time to achieve magnetic reset of the unipolar pulse transformer.

5. The active resonant magnetic reset method according to claim 4, characterized in that: In the step S41, the first working stage is from the start time to the end time of the unipolar pulse, the second working stage is the resonance stage of the leakage inductance and the resonant capacitor; the third working stage is the series resonance stage of the leakage inductance, the excitation inductance and the resonant capacitor, and the resonant current is positive in this stage, and the resonant current is 0 at the end of the third working stage; the fourth working stage is the series resonance stage of the leakage inductance, the excitation inductance and the resonant capacitor, and the resonant current is negative in this stage, and the end time of the fourth working stage is Reset MOSFET switch The fifth working stage is from the end of the fourth working stage to the beginning of the next unipolar pulse generation cycle.

6. The active resonant magnetic reset method according to claim 5, characterized in that: In step S42, calculating the end time of the fourth working stage includes: First, the excitation inductance current and the leakage inductance current at the end of the first working stage are calculated based on the mathematical expressions of the leakage inductance current and the excitation inductance current in the first working stage, that is, the initial values ​​of the excitation inductance current and the leakage inductance current at the initial moment of the second working stage are obtained; Then, based on the initial values ​​of the excitation inductance current and the leakage inductance current in the second working stage, mathematical expressions of the leakage inductance current and the excitation inductance current in the second working stage are constructed. Then, using the constraint condition that the excitation inductance current and the leakage inductance current are equal at the end of the second working stage, the end time of the second working stage is calculated, and the excitation inductance current and the leakage inductance current at the end of the second working stage are calculated, that is, the initial values ​​of the excitation inductance current and the leakage inductance current in the third working stage are obtained. Finally, based on the initial values ​​of the excitation inductance current and leakage inductance current in the third working stage, the mathematical expressions of the leakage inductance current and excitation inductance current in the third and fourth working stages are constructed. Then, the series resonant current of the resonant capacitor, leakage inductance and excitation inductance at the end of the fourth working stage is This constraint condition calculates the end time of the fourth working stage; where, is the coercive force, is the effective magnetic path length of the core of the unipolar pulse transformer, is the equivalent turns ratio.

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