Calculation method of impulse overvoltage of voltage regulator based on broadband equivalent circuit model

Abstract

The invention discloses a method for calculating impulse overvoltage of a voltage regulator based on a broadband equivalent circuit model, and the purpose is to provide a broadband equivalent circuit model of an active voltage regulator and an impulse overvoltage calculation method, which can quickly and accurately calculate the overvoltage distribution of a converter transformer and an active voltage regulator under lightning and operating impulse voltage, so as to overcome the defects of the prior art. The calculation method includes the topological structure of the active voltage regulator, generating an equivalent wiring schematic diagram of the active voltage regulator, establishing broadband equivalent circuit models of the energy extraction transformer and the power module in the converter transformer and the active voltage regulator, and calculating the various parameter values ​​in the broadband equivalent circuit model of the converter transformer and the energy extraction transformer and the broadband equivalent circuit model of the power module. Compared with the DC system simulation, the present invention adopts an active voltage regulator impulse overvoltage calculation method, which has a small amount of calculation and a short time consumption, and reveals the equivalent characteristics of the converter transformer and the active voltage regulator under lightning and operating impulse voltage.

Description

Technical Field

[0001] The invention relates to the field of active voltage regulator impulse overvoltage calculation, and in particular to a voltage regulator impulse overvoltage calculation method based on a broadband equivalent circuit model. Background Art

[0002] In order to meet the rapid voltage regulation requirements of the high-voltage direct current transmission system, a technical solution for voltage regulation of converter transformer power electronic technology is proposed to replace the original mechanical on-load tap-changing switch, that is, an active voltage regulator with flexible amplitude and phase adjustment is connected in series between the grid-side winding and the ground of the converter transformer, and the voltage of the valve-side winding of the converter transformer is adjusted in coordination with the AC system voltage. It has the advantages of unlimited number of actions and fast response speed. Compared with the traditional converter transformer regulated by mechanical on-load tap-changing switch, the introduction of active voltage regulator makes the structure of converter transformer more complicated. At present, there is no national standard for the design of active voltage regulator and supporting converter transformer insulation structure. It is necessary to analyze the influence of lightning impulse voltage and operating impulse voltage, and leave a certain margin to ensure the safety and reliability of product insulation structure. Lightning impulse voltage and operating impulse voltage are both high-frequency impulses, which will generate oscillating overvoltage in converter transformer and active voltage regulator. Once the dielectric strength of product insulation is exceeded, insulation damage failure will be caused. Therefore, calculating the overvoltage distribution of converter transformers and active voltage regulators under lightning impulse voltage and switching impulse voltage is of great significance for the design of product insulation structure and protection scheme.

[0003] At present, the calculation of the impulse overvoltage of the active voltage regulator can only be realized through DC system simulation. Due to the complex impulse overvoltage transmission process between the converter transformer and the active voltage regulator, the system simulation calculation is large and very time-consuming. Therefore, studying a new calculation method for the impulse overvoltage of the active voltage regulator and obtaining accurate overvoltage distribution results of the converter transformer and active voltage regulator under lightning and switching impulses is of great significance for improving the design and manufacturing level of converter transformers and active voltage regulators. Summary of the invention

[0004] The object of the present invention is to provide a voltage regulator impulse overvoltage calculation method based on a broadband equivalent circuit model, which can quickly and accurately calculate the overvoltage distribution of a converter transformer and an active voltage regulator under lightning and operating impulse voltages to overcome the defects of the prior art.

[0005] The technical solution of the present invention is: a method for calculating the impulse overvoltage of a voltage regulator based on a broadband equivalent circuit model, comprising the following steps:

[0006] Step 1: Generate an equivalent wiring schematic diagram of the active voltage regulator according to the topological structure of the active voltage regulator;

[0007] Step 2: Establish a broadband equivalent circuit model of the converter transformer and the energy extraction transformer in the active voltage regulator;

[0008] Step 3: Calculate the resistance, inductance and capacitance values ​​in the broadband equivalent circuit model of the converter transformer and the energy extraction transformer according to the electromagnetic field finite element calculation method;

[0009] Step 4: Establish a broadband equivalent circuit model of the power module in the active voltage regulator;

[0010] Step 5: Calculate the values ​​of each resistor, inductor, and capacitor in the broadband equivalent circuit model of the power module according to the impedance rational function approximation method;

[0011] Step 6: Determine the final broadband equivalent circuit model of the converter transformer and active voltage regulator;

[0012] Step 7: Apply corresponding lightning and switching impulse voltages to the AC bus in the final broadband equivalent circuit model;

[0013] Step 8: Use the circuit simulation analysis software PSCAD / EMTDC to build the final broadband equivalent circuit model of the converter transformer and active voltage regulator obtained in step (6), apply lightning and switching impulse voltages according to the position, amplitude and waveform determined in step (7), and obtain the instantaneous voltage value at each position of the converter transformer and the active voltage regulator by solving the circuit model. The overvoltage distribution results of the converter transformer and the active voltage regulator can be obtained based on the voltage values ​​at different positions that change with time.

[0014] Beneficial Effects

[0015] Compared with the DC system simulation, the active voltage regulator impulse overvoltage calculation method has small calculation amount and short time consumption, and reveals the equivalent characteristics of the converter transformer and active voltage regulator under lightning and switching impulse voltage. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is the equivalent wiring schematic diagram of the active voltage regulator;

[0017] Figure 2 The equivalent wiring schematic diagram of the active voltage regulator based on the H-bridge converter;

[0018] Figure 3 It is a schematic diagram of the broadband equivalent circuit model of the converter transformer and the active voltage regulator based on the H-bridge converter;

[0019] Figure 4 It is the RLC equivalent circuit diagram corresponding to each term of the rational function of impedance of power electronic devices. DETAILED DESCRIPTION

[0020] The broadband equivalent circuit model of the active voltage regulator and the impulse overvoltage calculation method in the present invention, the converter transformer is a single-phase three-winding converter transformer, the power module in the active voltage regulator is an H-bridge converter, and the active voltage regulator impulse overvoltage calculation method is implemented according to the following steps:

[0021] (1) Generate an equivalent wiring schematic diagram of the active voltage regulator according to the topological structure of the active voltage regulator: The power module in the active voltage regulator is an H-bridge converter. According to the connection method of the converter transformer winding, the connection method between the converter transformer and the active voltage regulator, and the topological structure of the active voltage regulator, generate an equivalent wiring schematic diagram of the active voltage regulator based on the H-bridge converter, such as Figure 2 As shown. In this embodiment, the converter transformer is connected between the AC system and the DC system; the converter transformer is a single-phase three-winding transformer, which is a grid-side winding, a valve-side winding and a voltage regulating winding, respectively, wherein A and N are the beginning and end of the grid-side winding, respectively, and G is the ground terminal; the topology of the active voltage regulator is composed of an energy-taking transformer, a capacitor and a plurality of back-to-back H-bridge converters, and the H-bridge converter is divided into a rectifier H-bridge converter and an inverter H-bridge converter; the high-voltage winding of the energy-taking transformer is connected to the voltage regulating winding of the converter transformer, and the low-voltage winding is connected to the rectifier H-bridge converter to supply energy to the active voltage regulator; the capacitor is connected between the rectifier H-bridge converter and the inverter H-bridge converter; the outputs of the plurality of H-bridge converters are connected in series with each other, and then connected to the N terminal and the G terminal respectively.

[0022] Figure 2 In the embodiment, the bridge arm of the H-bridge converter is composed of IGBT and its snubber circuit, diode and its snubber circuit in parallel, V1, V2, V3 and V4 are IGBTs; the control method adopts unipolar sinusoidal pulse width modulation (SPWM), that is, a triangular wave with a frequency of 750HZ and an amplitude of 150kV is used as the carrier U r , using a sine wave as the modulation wave U C , the amplitude and phase of the modulation wave can be flexibly controlled. When the modulation wave output is a positive half-wave, V1 is turned on and V2 is turned off. When the modulation wave output is a negative half-wave, V2 is turned on and V1 is turned off. If U r >U C , V4 is on, V3 is off, if U r C , V4 is turned off, and V3 is turned on; the output voltage amplitude and phase of multiple H-bridge converters are the same, and they can be connected in series to be equivalent to an H-bridge converter; the output port of the H-bridge converter is connected between the grid-side winding of the converter transformer and the ground, and the output voltage of the H-bridge converter can be flexibly changed by changing the amplitude and phase of the modulation wave, thereby changing the voltage of the grid-side winding and the valve-side winding of the converter transformer.

[0023] ​(2) Establish the broadband equivalent circuit model of the converter transformer and the energy extraction transformer in the active voltage regulator:

[0024] The wavefront time of lightning and switching impulse voltage is very short and belongs to high-frequency impulse. Therefore, the influence of the inter-turn capacitance and winding-to-ground capacitance of the converter transformer and the energy-taking transformer must be considered. At the same time, the static electricity or electromagnetic induction between the windings will affect the inter-turn voltage and the winding-to-ground voltage. Therefore, the equivalent circuit of the converter transformer and the active voltage regulator must consider the inter-turn capacitance, winding-to-ground capacitance and the capacitance between the windings. Based on the wiring schematic diagram of step (1), establish the following Figure 3 The broadband equivalent circuit model of the converter transformer and the active voltage regulator shown in the figure includes: the leakage inductance L1 and the equivalent resistance R1 of the grid-side winding of the converter transformer, the leakage inductance L2 and the equivalent resistance R2 of the valve-side winding, the leakage inductance L3 and the equivalent resistance R3 of the voltage regulating winding, the capacitance C to ground of the grid-side winding, the valve-side winding and the voltage regulating winding of the converter transformer 1g , C 2g , C 3g , the inter-turn capacitances C1, C2, C3 of the grid-side winding, valve-side winding, and voltage regulating winding of the converter transformer, and the coupling capacitance C between the grid-side winding and the valve-side winding of the converter transformer 12 , the coupling capacitance C between the grid-side winding of the commutation transformer and the voltage regulating winding 13 , the coupling capacitance C between the converter transformer valve side winding and the voltage regulating winding 23 The converter transformer model uses an ideal single-phase three-winding transformer; the leakage inductance L of the high-voltage side winding of the energy transformer is taken q1 And the equivalent resistance R q2 , the leakage inductance L of the low voltage side winding q2 And the equivalent resistance R q2 , the capacitance C of the high and low voltage side windings to ground q1g , C q2g , the inter-turn capacitance C of the high and low voltage side windings q1 , C q2 , coupling capacitance C between high and low voltage windings q12 , C q21, the model of the energy extraction transformer adopts an ideal single-phase double-winding transformer. The grid-side winding end of the broadband equivalent circuit model of the converter transformer is connected to the AC bus, the valve-side winding end is connected to the DC system, and the voltage regulating winding end is connected to the broadband equivalent circuit model of the energy extraction transformer. This step not only takes into account the inter-turn inductance, inter-turn capacitance and ground capacitance of the converter transformer and the energy extraction transformer windings, but also takes into account the complex structures of the converter transformer and the energy extraction transformer, and the electromagnetic relationship is coupled with each other. Even if some windings are not directly connected to the AC system, when the AC system encounters lightning or operation shocks, very high overvoltages will be induced on these windings, resulting in overvoltage coupling transmission. Therefore, this calculation method also takes into account the coupling capacitance between different windings of the converter transformer and the energy extraction transformer, making the final overvoltage calculation result more accurate and reliable.

[0025] (3) According to the electromagnetic field finite element calculation method, the resistance, inductance and capacitance values ​​in the broadband equivalent circuit model of the converter transformer and the energy extraction transformer are calculated.

[0026] According to the broadband equivalent circuit model of the converter transformer and the energy extraction transformer established in step (2), a simulation model of the converter transformer and the energy extraction transformer is established in the electromagnetic field simulation software, and the corresponding electrical performance parameters of the transformer winding, iron core, transformer insulating oil and insulating paper are input (provided by the transformer manufacturer). Although lightning and switching shocks are high-frequency shocks, the inductance and capacitance parameters of the converter transformer and the energy extraction transformer change little from industrial frequency to high frequency, so they can be replaced by the inductance and capacitance values ​​under industrial frequency. In the broadband equivalent circuit model of the converter transformer and the energy extraction transformer established in step (2), an industrial frequency voltage source excitation is applied, and the equivalent resistance of the transformer winding can be calculated through the active power loss of the winding, that is, Figure 3 R1, R2, R3, R q1 and R q2 The leakage inductance of the winding can be calculated through the magnetic field energy storage between the winding turns, that is, Figure 3 L1, L2, L3, L q1 and L q2 ; The capacitance of the winding to the ground can be calculated through the electric field energy storage between the winding and the ground, that is, Figure 3 C 1g , C 2g , C 3g , C q1g and C q2g , the electric field energy storage between the winding turns can be used to calculate the inter-turn capacitance of the winding, that is, Figure 3 C1, C2, C3, C q1 and C q2 , the coupling capacitance between windings can be calculated through the electric field energy storage between windings, that is, Figure 3 C 12 , C13 , C 23 , C q12 and C q21 .

[0027] (4) Establish a broadband equivalent circuit model of the power module in the active voltage regulator:

[0028] The power module of the active voltage regulator in this embodiment is an H-bridge converter, and the control method adopts sinusoidal pulse width modulation (SPWM). At any time, one of the upper and lower bridge arms must be turned on to provide a path for the transmission of the impulse voltage. The off resistance of the IGBT and diode of the turned-off bridge arm is very large, and the impulse voltage passing through can be ignored. Therefore, the broadband equivalent circuit model of the H-bridge converter only needs to consider the influence of the turned-on bridge arm. At the same time, the carrier and modulation waves of multiple H-bridge converters are the same, and the amplitude and phase of the output voltage are the same, which can be equivalent to an H-bridge converter. The broadband equivalent circuit model of the active voltage regulator based on the H-bridge converter is established as follows: Figure 3 As shown, the model includes: the equivalent resistance R of the conducting bridge arm device on the rectifier H-bridge converter ruloss , equivalent junction capacitance C ruj , equivalent stray inductance L ru And the equivalent snubber resistor R rus , equivalent buffer capacitance C rus ; The equivalent resistance R of the lower conducting bridge arm device of the rectifier H-bridge converter rdloss , equivalent junction capacitance C rdj , equivalent stray inductance L rd And the equivalent snubber resistor R rds , equivalent buffer capacitance C rds ; Equivalent resistance R of the conducting bridge arm device on the inverter H-bridge converter iuloss , equivalent junction capacitance C iuj , equivalent stray inductance L iu And the equivalent snubber resistor R ius , equivalent buffer capacitance C ius ; The equivalent resistance R of the lower conducting bridge arm device of the inverter H-bridge converter idloss , equivalent junction capacitance C idj , equivalent stray inductance L id And the equivalent snubber resistor R ids , equivalent buffer capacitance C ids ; Equivalent capacitance C of multiple H-bridge converters in series eq This calculation method not only takes into account the equivalent resistance of the H-bridge converter components, but also takes into account that lightning and switching impulses are high-frequency impulses, the electromagnetic process is very complex, and the model of the component at the power frequency is inaccurate. Therefore, this calculation method also takes into account the stray inductance, junction capacitance, and snubber resistance and snubber capacitance of the component, making the final overvoltage calculation more accurate.

[0029] (5) Based on the impedance rational function approximation method, the values ​​of each resistor, inductor, and capacitor in the broadband equivalent circuit model of the power module are calculated.

[0030] The power module of the active voltage regulator in this embodiment is an H-bridge converter. The impedance frequency characteristic data of the IGBT and diode devices in the H-bridge converter are measured by a network analyzer, which is a series of discrete points related to the frequency. The measured discrete points are then approximated by rational functions, and then circuit synthesis is performed to obtain the RLC equivalent series-parallel circuit of the final device. The present invention adopts a vector matching method to approximate the impedance rational function. Assume that the impedance rational function of the power electronic device in the H-bridge converter is: Among them, p k is the pole of the impedance rational function, res k is the residue corresponding to the pole, the linear term c and the constant term d are real numbers, and N is the total number of poles of the impedance rational function. Let the vector function be in is a set of known initial poles, is the residue corresponding to the initial pole, and is a set of unknown quantities. Multiply the vector function by the device impedance rational function to obtain Substituting a series of device impedance frequency characteristic data measured by the network analyzer, a set of linear equations can be obtained: Ax = b, and the unknown quantity in the linear equation is res in the impedance rational function expression. k , c, d, and vector functions By solving the linear equations, the device impedance rational function F(s) can be obtained, and then the poles of F(s) can be found. The RLC equivalent circuits corresponding to the first-order terms and constant terms in the device impedance rational function F(s), the RLC equivalent circuits corresponding to the real pole terms, and the RLC equivalent circuits corresponding to the conjugate complex pole terms are as follows: Figure 4 As shown, through circuit synthesis, the equivalent resistance of the H-bridge converter's conducting bridge arm device can be obtained, that is, Figure 3 R ruloss , R rdloss , R iuloss , R idloss ; The equivalent junction capacitance of the conducting bridge arm device of the H-bridge converter is Figure 3 C ruj , C rdj , C iuj , C idj ; The equivalent stray inductance of the conducting bridge arm device of the H-bridge converter is Figure 3 L ru , L rd , L iu , L id ; The equivalent buffer resistance of the H-bridge converter conducting bridge arm device, that is Figure 3R rus , R rds , R ius , R ids ; The equivalent buffer capacitance of the H-bridge converter conducting bridge arm device, that is Figure 3 C rus , C rds , C ius , C ids .

[0031] (6) Determine the final broadband equivalent circuit model of the converter transformer and active voltage regulator:

[0032] According to the calculation results of step 3, the sizes of the various capacitors in the broadband equivalent circuit models of the energy extraction transformer and the converter transformer are compared. If the coupling capacitance between the windings is much smaller than one twentieth of the winding-to-ground capacitance and the inter-turn capacitance, the coupling capacitance between the windings can be removed, and it is considered that the impulse overvoltage transmitted between the transformer windings can be ignored; according to the calculation results of step 5, the junction capacitance and the buffer capacitance in the broadband equivalent circuit model of the power module are compared. If the junction capacitance is much smaller than one twentieth of the buffer capacitance, the junction capacitance can be removed, and it is considered that the impulse voltage of the device at the moment of opening and closing is only transmitted through the buffer capacitance and the buffer resistance. Finally, the broadband equivalent circuit model of the converter transformer and the active voltage regulator is connected together according to the equivalent wiring schematic diagram of the active voltage regulator determined in step 1 to obtain the final broadband equivalent circuit model, as shown in FIG. Figure 3 shown.

[0033] (7) Apply the corresponding lightning and switching impulse voltages to the AC bus in the final broadband equivalent circuit model.

[0034] The waveform of the applied lightning impulse voltage adopts a standard waveform, with a wavefront and apparent half-peak time of 1.2μs and 50μs; the waveform of the switching impulse voltage adopts a standard waveform, with a wavefront and apparent half-peak time of 250μs and 2500μs; the amplitudes of the lightning and switching impulse voltages are determined according to the specific electrical parameters of the converter transformer and the active voltage regulator.

[0035] (8) Construct the final broadband equivalent circuit model of the converter transformer and active voltage regulator obtained in step 6 in the PSCAD / EMTDC simulation software, apply lightning and switching impulse voltages according to the position, amplitude and waveform determined in step 7, and obtain the instantaneous voltage values ​​at various positions of the converter transformer and active voltage regulator by solving the circuit model. The overvoltage distribution results of the converter transformer and active voltage regulator can be obtained based on the voltage values ​​at different positions that change with time.

[0036] The active voltage regulator impulse overvoltage calculation method proposed in the present invention is simple and easy to implement, and can calculate the overvoltage distribution of the converter transformer and the active voltage regulator under lightning and switching impulses. The calculation result is relatively accurate. Compared with the DC system simulation, the calculation amount and calculation time are greatly reduced, and the design of the converter transformer and the active voltage regulation insulation structure and protection scheme can be guided.

[0037] The present invention replaces the original mechanical on-load tap changer by inserting an active voltage regulator with flexible amplitude and phase adjustment in series between the end of the converter transformer grid-side winding and the ground, which changes the insulation structure of the converter transformer and requires a new insulation design. It is required to calculate the overvoltage distribution of the converter transformer winding and the active voltage regulator under lightning and switching impulses. At present, the calculation of the impulse overvoltage of the active voltage regulator can only be achieved through DC system simulation, which is computationally intensive and time-consuming. By analyzing the equivalent characteristics of the converter transformer and the active voltage regulator under lightning and switching impulses, a new impulse overvoltage calculation method is proposed, which can quickly calculate the overvoltages at various locations of the converter transformer and the active voltage regulator under lightning and switching impulses, and provide a theoretical basis for the design of the insulation structure and protection scheme of the active voltage regulator and the converter transformer.

[0038] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions only describe the principles of the present invention. The present invention may be subject to various changes and improvements without departing from the spirit and scope of the present invention. These changes and improvements fall within the scope of the present invention. The scope of protection claimed by the present invention is defined by the attached claims and their equivalents.

Claims

1. A method for calculating the impulse overvoltage of a voltage regulator based on a broadband equivalent circuit model comprises the following steps: Step 1: Generate an equivalent wiring schematic diagram of the active voltage regulator according to the topological structure of the active voltage regulator; Step 2: Establish a broadband equivalent circuit model of the converter transformer and the energy-taking transformer in the active voltage regulator: Establish a broadband equivalent circuit model of the converter transformer consisting of the inductance, resistance, turn-to-turn capacitance, winding-to-ground capacitance and coupling capacitance of each winding of the converter transformer; Establish a broadband equivalent circuit model of the energy-taking transformer consisting of the inductance, resistance, turn-to-turn capacitance, winding-to-ground capacitance and coupling capacitance of the high-voltage and low-voltage side windings of the energy-taking transformer; Step 3: Calculate the resistance, inductance and capacitance values ​​in the broadband equivalent circuit model of the converter transformer and the energy extraction transformer according to the electromagnetic field finite element calculation method; Step 4: Establish a broadband equivalent circuit model of the power module in the active voltage regulator; Step 5: Calculate the values ​​of each resistor, inductor, and capacitor in the broadband equivalent circuit model of the power module according to the impedance rational function approximation method; Step 6: Determine the final broadband equivalent circuit model of the converter transformer and active voltage regulator; Step 7: Apply corresponding lightning and switching impulse voltages to the AC bus in the final broadband equivalent circuit model; Step 8: Use the circuit simulation analysis software PSCAD / EMTDC to build the final broadband equivalent circuit model of the converter transformer and active voltage regulator obtained in step 6. Apply lightning and switching impulse voltages according to the position, amplitude and waveform determined in step 7. Obtain the instantaneous voltage value at each position of the converter transformer and active voltage regulator by solving the circuit model. The overvoltage distribution results of the converter transformer and active voltage regulator can be obtained based on the voltage values ​​at different positions that change with time.

2. According to the voltage regulator impulse overvoltage calculation method based on the broadband equivalent circuit model described in claim 1, it is characterized in that: the step 1 further includes the following content: according to the connection method of the converter transformer winding, the connection method between the converter transformer and the active voltage regulator, and the topological structure of the active voltage regulator, an equivalent wiring schematic diagram of the active voltage regulator is generated.

3. The voltage regulator impulse overvoltage calculation method based on the broadband equivalent circuit model according to claim 2 is characterized by: The step 1 further includes the following contents: when the converter transformer is a single-phase three-winding transformer, the converter transformer is respectively a grid-side winding, a valve-side winding and a voltage regulating winding, wherein A and N are respectively the beginning and the end of the grid-side winding, and G is the grounding terminal; the topology of the active voltage regulator includes an energy-taking transformer, a capacitor and a plurality of back-to-back power modules, and the power modules are further divided into a rectifier power module and an inverter power module; the high-voltage winding of the energy-taking transformer is connected to the voltage regulating winding of the converter transformer, and the low-voltage winding is connected to the rectifier power module; the topology of the active voltage regulator is composed of an energy-taking transformer, a capacitor and a plurality of back-to-back H-bridge converters, and the H-bridge converter is divided into a rectifier H-bridge converter and an inverter H-bridge converter; the outputs of the plurality of H-bridge converters are connected in series with each other, and then respectively connected to the N terminal and the G terminal.

4. The voltage regulator impulse overvoltage calculation method based on the broadband equivalent circuit model according to claim 1 is characterized by: The step 3 further includes the following contents: in the broadband equivalent circuit model of the converter transformer and the energy extraction transformer established in step 2, applying an industrial frequency voltage source excitation, calculating the equivalent resistance of the transformer winding through the active power loss of the winding, calculating the leakage inductance of the winding through the magnetic field energy storage between the winding turns, calculating the capacitance of the winding to the ground through the electric field energy storage between the winding and the ground, calculating the inter-turn capacitance of the winding through the electric field energy storage between the winding turns, and calculating the coupling capacitance between the windings through the electric field energy storage between the windings.

5. The method for calculating the impulse overvoltage of a voltage regulator based on a broadband equivalent circuit model according to claim 1 is characterized in that: the step 5 further comprises the following contents: the power module of the active voltage regulator is an H-bridge converter, and the impedance frequency characteristic data of the IGBT and diode devices in the H-bridge converter are measured by a network analyzer, which is a series of discrete points related to frequency, and then the measured discrete points are approximated by rational functions, and then circuit synthesis is performed to obtain the RLC equivalent series-parallel circuit of the final device.

6. The voltage regulator impulse overvoltage calculation method based on the broadband equivalent circuit model according to claim 1 is characterized by: The step 6 further includes the following contents: according to the result calculated in step 3, the sizes of the various capacitors in the broadband equivalent circuit models of the energy extraction transformer and the converter transformer are compared; if the coupling capacitance between the windings is less than one twentieth of the winding-to-ground capacitance and the inter-turn capacitance, the coupling capacitance between the windings is removed, and it is considered that the impulse overvoltage transmitted between the transformer windings is negligible; according to the result calculated in step 5, the junction capacitance and the buffer capacitance in the broadband equivalent circuit model of the power module are compared; if the junction capacitance is less than one twentieth of the buffer capacitance, the junction capacitance is removed, and it is considered that the impulse voltage of the device at the moment of turning on and off is only transmitted through the buffer capacitance and the buffer resistance; finally, the converter transformer and the broadband equivalent circuit model of the active voltage regulator are connected together according to the equivalent wiring schematic diagram of the active voltage regulator determined in step 1 to obtain the final broadband equivalent circuit model.

7. The voltage regulator impulse overvoltage calculation method based on the broadband equivalent circuit model according to claim 1 is characterized in that: the step 7 further includes the following contents: the waveform of the applied lightning impulse voltage adopts a standard waveform, and the wavefront and apparent half-peak time are 1.2μs and 50μs; the waveform of the operating impulse voltage adopts a standard waveform, and the wavefront and apparent half-peak time are 250μs and 2500μs; the amplitudes of the lightning and operating impulse voltages are determined according to the specific electrical parameters of the converter transformer and the active voltage regulator.

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