CN111308222A - Capacitor bank inductance estimation method based on parameter correction - Google Patents

Abstract

In order to solve the technical problem that an existing capacitor bank inductance estimation method is large in error, the invention provides a capacitor bank inductance estimation method based on parameter correction.

Description

A method for estimating capacitor bank inductance based on parameter correction

technical field

The invention relates to an inductance estimation method, in particular to an inductance estimation method suitable for a circuit capacitor bank of a pulse power device unit, which is a parameter correction method based on a stripline inductance calculation formula.

Background technique

The circuit of the pulse power device unit refers to the basic charging and discharging circuit composed of two capacitors of the same specification placed side by side, and the conductor plates and trigger switches that connect them. When designing the Marx generator and the LTD drive source, it is necessary to estimate the key parameters such as the capacitance and inductance of the unit loop to determine the electrical pulse output waveform parameters of the basic unit and the whole device. Most of the capacitors currently used in pulsed power devices have a cuboid structure, which is often equivalent to a stripline when estimating the loop inductance, and the equivalent conductor layer is considered to be in the middle of the capacitor, that is, the "intermediate layer assumption". However, in engineering practice, it is found that such a simple equivalence has different degrees of error for different capacitor models and different spacings, up to more than 20%, which is not conducive to the accurate estimation of device operating parameters.

SUMMARY OF THE INVENTION

In order to solve the technical problem of large error in the existing capacitor bank inductance estimation method, the present invention provides a capacitor bank inductance estimation method based on parameter correction.

The inventive concept of the present invention is:

On the basis of the formula based on the calculation of stripline inductance, the invention obtains the measured data of the inductance of the capacitor bank by constructing the charging and discharging experimental device of the unit loop, and simultaneously uses the Maxwell electromagnetic field simulation method to obtain the measured data of the inductance of the capacitor bank, and then compare and fit with the calculation result of the original formula. , get the correction factor suitable for the capacitor of this specification.

The technical scheme of the present invention is:

The special feature of the capacitor bank inductance estimation method based on parameter correction is that it includes the following steps:

Step 1: Build a unit circuit charging and discharging experimental device

The equivalent circuit of the unit loop charging and discharging experimental device includes a first capacitor, a second capacitor, a positive charging power source, a negative charging power source, a trigger electrode switch, a measuring end connecting plate, a charging end connecting plate and a Rogowski coil;

One end of the first capacitor is connected to the output of the positive charging power supply through the protection resistor of the positive charging branch, the other end of the first capacitor is connected to one end of the second capacitor through the measuring terminal connecting plate and the equivalent resistance of the discharge loop, and the other end of the second capacitor is connected to the output of the positive charging power supply. One end is connected to the output of the negative charging power supply through the protection resistor of the negative charging branch; the trigger electrode switch is set between the positive charging power supply and the negative charging power supply through the connecting plate of the charging end; the Rogowski coil is surrounded by the connecting plate of the measuring end;

The first capacitor and the second capacitor are arranged side by side to form a capacitor bank, and a plurality of separators made of insulating materials are arranged between the first capacitor and the second capacitor. By changing the number of the separators, the first capacitor and the second capacitor can be controlled. The spacing between the second capacitors varies from 5mm to 30mm;

Step 2: Charge the Capacitor Bank

Apply a charging voltage to the first capacitor and the second capacitor, and gradually increase the charging voltage from 0 until the gap of the trigger electrode switch is discharged and turned on;

Step 3: Obtain the measured inductance L _C of the capacitor bank

Adjust the distance between the first capacitor and the second capacitor from 5mm to 30mm step by step, and carry out at least four sets of experiments with different distances. Each set of experiments tests N current waveforms as data samples, and calculates the capacitor bank of each set of experiments. The average value of inductance is taken as the measured inductance _LC of this group of experiments; N≥10; the method of obtaining the measured inductance _LC of the capacitor bank of a single group of experiments is:

3.1) Use Maxwell simulation to calculate the loop inductance LA of the connecting board at the charging end and the loop inductance _{LB of the connecting board at the measuring end, and estimate the spark channel inductance L D ≈ 14x} at the trigger electrode switch, unit nH; x is the distance of the spark channel, unit cm;

3.2) Use Rogowski coil and oscilloscope to measure N times, measure N current waveforms of the unit circuit, read the current oscillation period and the first two peaks and time points respectively, so as to calculate the total circuit of the unit circuit obtained by N times of testing The inductances are L _m1 , L _m2 ,..., L _mN ;

3.3) Calculate the inductance of the capacitor bank of the current group of experiments:

L _C1 =L _m1 -(L _A +L _B +L _D ),

L _C2 =L _m2 -(L _A +L _B +L _D ),

…

L _CN =L _mN -(L _A +L _B +L _D );

3.4) Calculate the measured inductance L _C of the current group of experiments:

Step 4: Calculate the equivalent calculated value L _f of the capacitor bank inductance

并令

According to the theoretical calculation formula of strip transmission line inductance:

and order

Where: l is the length of the stripline, w is the width of the stripline, d is the inner spacing of the stripline, and μ ₀ is the vacuum permeability;

In the above formula, it is assumed that the capacitor bank is equivalent to a flat plate located in the middle layer, then d=h+j, where h is the height of a single capacitor, and j is the distance between two capacitors; Step 3 is calculated according to the above formula The equivalent calculated value of the capacitor bank inductance under at least four groups of different spacings is L _f ;

Step 5: Obtain the correction factor α for the thickness of the capacitor

Comparing and fitting the measured inductance L _C obtained by at least four sets of experiments described in step 3 and the equivalent calculated value L _f of the corresponding capacitor bank inductance obtained in step 4, after trial and error, the first capacitor and the second capacitor are obtained. When the absolute value of the inductance estimation error is within the design accuracy requirements, the correction coefficient α of the capacitor thickness;

Step 6: Calculate the corrected capacitor bank inductance L' _f

Bring d=αh+j into the theoretical calculation formula of the strip transmission line inductance, and solve the modified capacitor bank inductance L′ _f .

Further, the trigger electrode switch described in step 1 includes two M3 screws installed at opposite intervals. After grinding the nail head of each M3 screw, it is fixed on the charging end connecting plate with a nut at a relative interval to form a trigger electrode switch.

Further, in step 2, the output of one of the charging power sources is set to be constant, and then the output of the other charging power source is slowly increased until the trigger electrode switch is discharged and turned on.

Further, in step 3, a total of 6 groups of experiments are carried out, and the distances between the two capacitors corresponding to the 6 groups of experiments are respectively 5mm, 10mm, 15mm, 20mm, 25mm and 30mm.

Further, in step 3, N=20.

Further, the materials of the measuring end connecting plate and the charging end connecting plate described in step 1 are all 304 stainless steel, and the thicknesses are both 1mm.

Further, the measuring end connecting plate and the charging end connecting plate described in step 1 are provided with elongated waist-shaped holes.

Beneficial effects of the present invention:

The invention designs and builds a charging and discharging experimental device for a unit loop, uses a Rogowski coil and an oscilloscope to obtain the current waveform of the loop discharge, and calculates the total loop inductance of the capacitor of this specification under a specific spacing condition according to the waveform. On the other hand, in the Maxwell environment, the inductance of the connecting conductor plate is obtained through the electromagnetic field simulation, and the spark channel inductance at the electrode is calculated according to the empirical formula, and the conductor plate inductance and the spark channel inductance are deducted from the total loop inductance to obtain the measured value of the capacitor bank inductance. . By comparing and fitting the measured values of capacitors of the same specification under different spacing conditions with the calculated values based on the stripline inductance calculation formula, the correction coefficient of the original calculation formula is obtained. Using this method, for several capacitors with typical capacity specifications, the specific correction parameter values are given, and the estimation accuracy of the revised calculation formula is significantly improved.

Description of drawings

FIG. 1 is an equivalent circuit diagram of the unit loop charging and discharging experimental device of the present invention.

Fig. 2 is the accuracy comparison (60nF) of the inductance estimation method provided by the present invention and the original method.

In Figure 1, 1. Positive charging power supply, 2. Negative charging power supply, 3. Trigger electrode switch, 4. First capacitor (positively charged), 5. Second capacitor (negatively charged), 6. Equivalent resistance of discharge circuit , 7. Rogowski coil, 8. Measuring terminal connection board, 9. Charging terminal connection board, 10. Positive charging branch protection resistance, 11-negative charging branch protection resistance.

Detailed ways

The present invention will be further described below with reference to the accompanying drawings and embodiments.

In this embodiment, the basic structure is a rectangular insulating material shell, and the inside of the shell is in the form of laminated winding of metal films, sealed with insulating oil, the nominal capacitance value is 60nF, and the size parameters are l(length)=255mm, w (width)=154mm, h (height)=62mm The capacitor bank constituted by two capacitors (respectively denoted as the first capacitor 4 and the second capacitor 5) is taken as the estimated object to illustrate the implementation process of the present invention.

1-2, the implementation process of this embodiment is as follows:

Step 1: Build a unit circuit charging and discharging experimental device

Assemble the unit loop charge and discharge experimental device, connect the charging cable and the current measurement cable; the equivalent circuit of the unit loop charge and discharge experimental device is shown in Figure 1, including the first capacitor 4, the second capacitor 5, the positive charging power supply 1, Negative charging power supply 2, trigger electrode switch 3, measuring end connecting plate 8, charging end connecting plate 9 (there are two sections, one of which is fixed, and the other section can be adjusted in length through the waist-shaped hole) and Rogowski coil 7; the first capacitor One end of 4 is connected to the output of the positive charging power supply 1 through the positive charging branch protection resistor 10, and the other end of the first capacitor 4 is connected to one end of the second capacitor 5 through the measuring terminal connecting plate 8 and the equivalent resistance 6 of the discharge circuit. The other end of the second capacitor 5 is connected to the output of the negative charging power source 2 through the negative charging branch protection resistor 11; the trigger electrode switch 3 is set between the positive charging power source 1 and the negative charging power source 2 through the charging terminal connecting plate 9; the Rogowski coil 7 It surrounds the connecting plate 8 of the measuring end (there are two sections, one of which is fixed and the other can be adjusted in length through the waist-shaped hole).

in:

The first capacitor 4 and the second capacitor 5 are arranged side by side to form a capacitor bank. In the experimental device, a bracket for fixing the first capacitor 4 and the second capacitor 5 and for adjusting the relationship between the first capacitor 4 and the second capacitor 5 are also designed. For a plurality of spacers spaced apart, the materials of the bracket and the spacer are all nylon (or other insulating materials), and the thickness of a single spacer is 5mm (the thickness can also be other values). The spacer is arranged between the first capacitor 4 and the second capacitor 5, and the distance between the first capacitor 4 and the second capacitor 5 is 5mm initially. By changing the number of spacers between the first capacitor 4 and the second capacitor 5 , the distance between the first capacitor 4 and the second capacitor 5 can be controlled to vary from 5mm to 30mm.

The positive charging power source 1 and the negative charging power source 2 are respectively ±100kV DC power sources, the positive charging power source 1 is used to charge the first capacitor 4 positively, and the negative charging power source 2 is used to negatively charge the second capacitor 5; The output of one charging power source is set to be constant, and then the output of the other charging power source is slowly increased until the trigger electrode switch 3 is discharged and turned on.

The trigger electrode switch 3 includes two M3 screws installed at opposite intervals. After grinding the nail head of each M3 screw, it is fixed on the two sections of the charging end connecting plate 9 by nuts to constitute the trigger electrode switch 3 . The electrode gap of the trigger electrode switch 3 is about 1 mm, so that the breakdown voltage of the electrode is less than 10 kV. In other embodiments, the trigger electrode switch 3 may also adopt other existing structural forms.

The Rogowski coil 7 is an electronic device that uses the principle of electromagnetic induction to measure transient current. The device surrounds the measuring end connecting plate 8. The oscilloscope collects the current waveform signal of the unit loop through the Rogowski coil 7; according to the waveform characteristics of the current waveform signal , the total inductance value of the unit loop can be calculated analytically.

The measuring end connecting plate 8 and the charging end connecting plate 9 are all made of 304 stainless steel with a thickness of 1 mm. The measuring end connecting plate 8 and the charging end connecting plate 9 are provided with long waist-shaped holes, so that they have a certain range of lengths. The adjustment capability enables the length of the connecting plate to be adjusted accordingly as the distance between the first capacitor 4 and the second capacitor 5 changes.

Step 2: Charge the Capacitor Bank

Apply charging voltage to the first capacitor 4 and the second capacitor 5, the voltage should not be too high, the discharge gap of the trigger electrode switch 3 is about 1mm, the breakdown voltage is about 3kV, and the charging voltage is gradually increased from 0 to the gap discharge of the trigger electrode switch 3 turn on;

Step 3: Obtain the measured inductance L _C of the capacitor bank

The distance between the first capacitor 4 and the second capacitor 5 is gradually adjusted from 5mm to 30mm, and at least 4 sets of experiments are carried out respectively. In this embodiment, 6 sets of experiments are carried out (the distance between the two capacitors corresponding to the 6 sets of experiments is 5mm, 10mm, 15mm, 20mm, 25mm and 30mm, in other embodiments, other spacing values can also be selected), 20 current waveforms are tested in each group of experiments as data samples, and the average value of capacitor bank inductance in this group of experiments is calculated as this group of experiments. The measured inductance _LC ; the acquisition method of each group of experimental measured inductance _LC is consistent, the following only takes the distance between the first capacitor 4 and the second capacitor 5 as 5mm as an example to illustrate the acquisition method of the measured inductance _LC :

3.1) Use Maxwell simulation to calculate the loop inductance LA of the connecting plate 9 at the charging end and the loop inductance LB of the connecting plate 8 at the measuring end, and estimate the spark channel inductance _{L D} ≈ 14x(nH) at the trigger electrode switch ₃ , where x is the spark Channel distance (unit cm);

3.2) Use Rogowski coil and oscilloscope to measure 20 current waveforms of the unit loop, read the current oscillation period and the first two peaks and time points respectively, so as to calculate the total loop inductance of the unit loop obtained by 20 tests is L respectively _m1 ,L _m2 ,...,L _m20 ;

3.3) Calculate the inductance of the capacitor bank of the current group of experiments:

L _C1 =L _m1 -(L _A +L _B +L _D ),

L _C2 =L _m2 -(L _A +L _B +L _D ),

…

L _C20 =L _m20 -(L _A +L _B +L _D );

3.4) Calculate the measured inductance L _C of the current group of experiments:

Step 4: Calculate the equivalent calculated value L _f of the capacitor bank inductance

并令

其中l为带状线长度，w为带状线宽度，d为带状线内侧间距，μ₀为真空磁导率。According to the theoretical calculation formula of strip transmission line inductance:

and order

Where l is the length of the stripline, w is the width of the stripline, d is the distance between the inner sides of the stripline, and μ ₀ is the vacuum permeability.

In the above formula, assuming that the capacitor bank is equivalent to a flat plate in the middle layer ("interlayer hypothesis"), then d=h+j, where h is the height of a single capacitor and j is the spacing between the two capacitors. According to the above formula, the equivalent calculated value of the capacitor bank inductance is L _f (in the distance between the two capacitors corresponding to the 6 groups of experiments, each distance is only calculated once).

Step 5: Obtain the correction factor α for the thickness of the capacitor

Considering that the internal structures of the first capacitor 4 and the second capacitor 5 are wound bodies of multi-layer metal thin strips, the size parameters and winding methods of capacitors with different specifications may be different, so the "intermediate layer assumption" for capacitor inductance estimation Not of general applicability. Therefore, the coefficient correction is performed on the capacitor thickness here, and the equivalent plate spacing is considered to be the sum of the spacing between the two capacitors and the corrected thickness of the capacitor, that is, d=αh+j, where α is the correction coefficient. According to the comparison and fitting of the L _C and the corresponding L _f value of the above 6 groups of experiments, after trial and error, it is known that for a 60nF capacitor, when α = 0.93, the absolute value of the inductance estimation error can be controlled within 2%, which is relatively correct. The calculation accuracy of the previous formula has been greatly improved, as shown in FIG. 2 , which proves that the method provided by the present invention can effectively improve the inductance estimation accuracy.

Step 6: Calculate the corrected capacitor bank inductance L' _f

Bring d=αh+j, α=0.93 into the theoretical calculation formula of the strip transmission line inductance, and solve the corrected inductance L′ _f of the capacitor bank.

Claims (7)

1. A capacitor bank inductance estimation method based on parameter correction, characterized in that it comprises the following steps: Step 1: Build a unit circuit charging and discharging experimental device The equivalent circuit of the unit loop charge and discharge experiment device includes a first capacitor (4), a second capacitor (5), a positive charging power source (1), a negative charging power source (2), a trigger electrode switch (3), and a measurement terminal a connecting plate (8), a charging end connecting plate (9) and a Rogowski coil (7); One end of the first capacitor (4) is connected to the output of the positive charging power supply (1) through the positive charging branch protection resistor (10), and the other end of the first capacitor (4) is connected to the measuring end connecting plate (8), the discharge circuit, etc. The effective resistor (6) is connected to one end of the second capacitor (5), and the other end of the second capacitor (5) is connected to the output of the negative charging power supply (2) through the negative charging branch protection resistor (11); the trigger electrode switch ( 3) The charging end connecting plate (9) is arranged between the positive charging power source (1) and the negative charging power source (2); the Rogowski coil (7) surrounds the measuring end connecting plate (8); The first capacitor (4) and the second capacitor (5) are arranged side by side opposite to each other to form a capacitor bank, and a plurality of separators made of insulating materials are arranged between the first capacitor (4) and the second capacitor (5), and by changing the The number of the separators can be controlled to change the distance between the first capacitor (4) and the second capacitor (5) from 5mm to 30mm; Step 2: Charge the Capacitor Bank A charging voltage is applied to the first capacitor (4) and the second capacitor (5), and the charging voltage is gradually increased from 0 until the gap discharge of the trigger electrode switch (3) is turned on; Step 3: Obtain the measured inductance L _C of the capacitor bank Adjust the spacing between the first capacitor (4) and the second capacitor (5) from 5mm to 30mm step by step, and carry out at least four sets of experiments with different spacings. Each set of experiments tests N current waveforms as data samples to calculate The average value of the capacitor bank inductance of each group of experiments is used as the measured inductance _LC of this group of experiments; N≥10; the method of obtaining the measured inductance _LC of the capacitor bank of a single group of experiments is: 3.1) Use Maxwell simulation to calculate the loop inductance LA of the connecting board (9) at the charging end and the loop inductance LB of the connecting board (8) at the measuring end, and estimate the spark channel inductance _{L D} ≈ 14x at the trigger electrode switch (3 ₎ , in units of nH; x is the spark channel distance, in cm; 3.2) Use Rogowski coil and oscilloscope to measure N times, measure N current waveforms of the unit circuit, read the current oscillation period and the first two peaks and time points respectively, so as to calculate the total circuit of the unit circuit obtained by N times of testing The inductances are L _m1 , L _m2 ,..., L _mN ; 3.3) Calculate the inductance of the capacitor bank of the current group of experiments: L _C1 =L _m1 -(L _A +L _B +L _D ), L _C2 =L _m2 -(L _A +L _B +L _D ), … L _CN =L _mN -(L _A +L _B +L _D ); 3.4) Calculate the measured inductance L _C of the current group of experiments:

Step 4: Calculate the equivalent calculated value L _f of the capacitor bank inductance According to the theoretical calculation formula of strip transmission line inductance:

and order

Where: l is the length of the stripline, w is the width of the stripline, d is the inner spacing of the stripline, and μ ₀ is the vacuum permeability; In the above formula, it is assumed that the capacitor bank is equivalent to a flat plate located in the middle layer, then d=h+j, where h is the height of a single capacitor, and j is the distance between two capacitors; Step 3 is calculated according to the above formula The equivalent calculated value of the capacitor bank inductance under at least four groups of different spacings is L _f ; Step 5: Obtain the correction factor α for the thickness of the capacitor Comparing and fitting the measured inductance L _C obtained by at least four sets of experiments described in step 3 and the equivalent calculated value L _f of the corresponding capacitor bank inductance obtained in step 4, after trial and error, the first capacitor (4) and When the absolute value of the inductance estimation error of the second capacitor (5) is within the design accuracy requirement, the correction coefficient α of the capacitor thickness; Step 6: Calculate the corrected capacitor bank inductance L _f ′ Bring d=αh+j into the theoretical calculation formula of the strip transmission line inductance, and solve the modified capacitor bank inductance L′ _f . 2. The capacitor bank inductance estimation method based on parameter correction according to claim 1, characterized in that: the trigger electrode switch (3) described in step 1 comprises two M3 screws installed at relative intervals, and each M3 screw is After grinding, the nail head is fixed on the connecting plate (9) of the charging end by means of nuts at relative intervals to form a trigger electrode switch (3). 3. The capacitor bank inductance estimation method based on parameter correction according to claim 1 or 2, characterized in that: in step 2, the output of one of the charging power sources is set to be constant, and then the output of the other charging power source is slowly increased, Until the trigger electrode switch (3) is discharged and turned on. 4. The capacitor bank inductance estimation method based on parameter correction according to claim 3 is characterized in that: in step 3, 6 groups of experiments are carried out, and the distances between the two capacitors corresponding to the 6 groups of experiments are respectively 5mm, 10mm, 15mm, 20mm , 25mm and 30mm. 5 . The method for estimating capacitor bank inductance based on parameter correction according to claim 4 , wherein in step 3, N=20. 6 . 6. The method for estimating capacitor bank inductance based on parameter correction according to claim 5, wherein the material of the measuring end connecting plate (8) and the charging end connecting plate (9) described in step 1 are all 304 stainless steel , the thickness is 1mm. 7. The method for estimating capacitor bank inductance based on parameter correction according to claim 6, wherein the measuring end connecting plate (8) and the charging end connecting plate (9) described in step 1 are provided with long strips Waist hole.

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