CN105762800A - Reactor skin effect equivalent thermocurrnet calculation method and apparatus - Google Patents

Abstract

The invention relates to a reactor skin effect equivalent thermocurrnet calculation method and apparatus. According to the method, an obtained relative impedance coefficient of a feature harmonic wave point of a reactor is substituted into an established polynomial model, curve fitting is carried out by use of least squares, and accordingly, a continuous relative coefficient of the reactor in a whole frequency scope is obtained; then, a skin effect filter is constructed; and finally, acquired currents on the reactor are substituted into the skin effect filter so as to solve equivalent thermocurrents of the reactor. The invention also discloses a reactor skin effect equivalent thermocurrnet calculation apparatus designed according to the method. The apparatus comprises a continuous relative impedance coefficient module, a skin effect filter module and an equivalent thermocurrent module. The reactor skin effect equivalent thermocurrnet calculation method and apparatus brought forward by the invention can simulate a skin effect in a whole frequency scope, greatly reduce the computation amount, at the same time, also maintain quite high calculation accuracy and are easy to realize in a protection apparatus.

Description

Calculation method and device for reactor skin effect equivalent thermal current

technical field

The invention relates to a calculation method and a device for the skin effect equivalent thermal current of a reactor, and belongs to the technical field of direct current transmission systems.

Background technique

In HVDC power transmission projects, AC filters are essential primary equipment. Its function is to provide reactive power compensation and filter out the harmonic current generated by the AC system during the operation of the DC system. Reactors are essential components in various types of filters. During the operation of the AC filter, the fundamental current and large harmonic current will pass through, and these currents will cause heat in the equivalent resistance of the reactor winding.

Under the action of the electromagnetic field, the current distribution inside the reactor conductor is uneven, and the closer to the conductor surface, the greater the current density. This phenomenon is called the skin effect. The higher the frequency, the more obvious the skin effect, and the corresponding electrical impedance related to heating is also greater. The degree of increase in the resistance of each harmonic is different, and the higher the harmonic order, the greater the resistance. In the design of reactor protection, it is necessary to calculate an equivalent heating current

The methods for calculating the equivalent heating current in the prior art are as follows: (1) Considering the heating caused by the high-order harmonic current, and only considering the heating caused by the fundamental current. (2) Use DFT to extract the effective values of a limited number of harmonic points, then multiply them by their respective skin effect coefficients, and then undergo multiple square operations, then sum them up, and finally take the square root. (3) The third method is similar to the second one, except that the FFT method is used instead of the DFT method. However, the (1) method completely ignores the skin effect, which is far from the actual operation of the reactor; the (2) method has a huge amount of calculation; the (3) method has a reduced amount of calculation. And the latter two methods can only reflect the skin effect of several frequency points, and completely ignore other points.

Contents of the invention

The purpose of the present invention is to overcome the deficiencies in the prior art, and proposes a calculation method for the equivalent thermal current of the reactor skin effect, which solves the problem of a large amount of computation when calculating the equivalent thermal current of the reactor in the entire frequency range. A calculation device for the equivalent thermal current of the skin effect of the reactor is proposed.

The present invention is achieved by the following scheme:

1. The calculation method of the reactor skin effect equivalent thermal current is characterized in that the steps are as follows:

Step 1, obtain the relative impedance coefficient of the characteristic harmonic point of the reactor, substitute the relative impedance coefficient into the established polynomial model, and use the least square method for curve fitting, so as to obtain the continuous relative coefficient of the reactor in the entire frequency range ;

Step 2, constructing a digital filter, decomposing the digital filter into not less than one sub-filter cascade, and then forming a skin effect filter;

Step 3, the current on the collection reactor is preliminarily processed and then substituted into the skin effect filter for filtering, and the filtered current is further processed to obtain the equivalent thermal current of the reactor.

Further, the processing of the relative impedance coefficient described in step 1 refers to: setting the relative coefficient of the fundamental wave in the harmonic circuit to 1; then, setting a relative coefficient of the highest harmonic point, and The coefficient is processed by the square root;

The established polynomial model expression is as follows:

p(x)＝p ₁ x ⁿ +p ₂ x ^n-1 +...+p _n x+p _n+1

Among them, p(x) is the continuous impedance coefficient in the whole frequency range; p ₁ , p ₂ …p _n , p _n+1 are coefficients of polynomials, using the obtained relative impedance system, using the least squares method for curve fitting, The parameters p ₁ , p ₂ ...p _n , p _n+1 of the polynomial are obtained; x is the order of the harmonic; n is the order of the polynomial.

Further, the parameters in the digital filter described in step 2 are obtained by substituting the continuous relative coefficients obtained in step 1 into the established Yule-Walker equation for solution.

Further, in the step 2, the root operation is performed on the numerator and denominator polynomial in the digital filter, and two roots are selected as a group, so as to realize decomposing the digital filter into no less than one second-order filter stage connected, the second-order filter is the sub-filter.

Further, the preliminary processing in step 3 is to perform high-pass filtering on the current on the collection reactor;

The expression for obtaining the equivalent current is:

Among them, R ₁ , R ₂ ... R _k is the harmonic impedance of the reactor under each harmonic current; A _k is the peak value of each harmonic current component in the collected reactor current instantaneous value I(t) ; is the phase of each harmonic current component; k is the harmonic order of each harmonic component, k=1,2...n; ω is the angular frequency of the fundamental wave;

The further processing of the current filtered by the skin effect filter refers to: the square operation, high-pass filter and square root operation are performed on the current obtained after the skin effect filter, and then the equivalent thermal current of the reactor is obtained. .

2. A device for calculating the skin effect equivalent thermal current of a reactor, characterized in that the device includes: a continuous relative impedance coefficient module, a skin effect filter module and an equivalent thermal current module, specifically as follows:

1) Continuous relative impedance coefficient module: obtain the relative impedance coefficient of the characteristic harmonic point of the reactor, substitute the relative impedance coefficient into the established polynomial model, and use the least square method for curve fitting, so as to obtain the reactor at the entire frequency Range continuous relative coefficients;

2) Skin effect filter module: construct a digital filter, decompose the digital filter into not less than one sub-filter cascade, and then form a skin effect filter;

3) Equivalent thermal current module: After preliminary processing, the current on the collection reactor is substituted into the skin effect filter for filtering, and the filtered current is further processed to obtain the equivalent thermal current of the reactor .

Further, the processing of the relative impedance coefficient described in the continuous relative impedance coefficient module refers to: setting the relative coefficient of the fundamental wave in the harmonic circuit to 1; then, setting a relative coefficient of the highest harmonic point , and perform square root processing on the coefficient;

The established polynomial model expression is as follows:

p(x)＝p ₁ x ⁿ +p ₂ x ^n-1 +...+p _n x+p _n+1

Among them, p(x) is the continuous impedance coefficient in the whole frequency range; p ₁ , p ₂ …p _n , p _n+1 are polynomial coefficients, using the obtained relative impedance system, using the least squares method for curve fitting, The parameters p ₁ , p ₂ ...p _n , p _n+1 of the polynomial are obtained; x is the order of the harmonic; n is the order of the polynomial.

Further, the parameters in the digital filter described in the skin effect filter module are obtained by substituting the continuous relative coefficients obtained in step 1 into the established Yule-Walker equation for solution.

Further, in the skin effect filter module, the root-finding operation is performed on the numerator and denominator polynomial in the digital filter, and two roots are selected as a group, so as to decompose the digital filter into no less than a second-order The cascading of filters, the second-order filter is the sub-filter.

Further, the preliminary processing in the equivalent thermal current module is to perform high-pass filtering on the current on the collection reactor;

The expression for obtaining the equivalent current is:

Among them, R ₁ , R ₂ ... R _k is the harmonic impedance of the reactor under each harmonic current; A _k is the peak value of each harmonic current component in the collected reactor current instantaneous value I(t) ; is the phase of each harmonic current component; k is the harmonic order of each harmonic component, k=1,2...n; ω is the angular frequency of the fundamental wave;

The further processing of the current filtered by the skin effect filter refers to: the square operation, high-pass filter and square root operation are performed on the current obtained after the skin effect filter, and then the equivalent thermal current of the reactor is obtained. .

The beneficial effect of the present invention compared with prior art is:

Aiming at the above existing problems, the present invention proposes a calculation method and device for the skin effect equivalent thermal current of a reactor. By establishing a reference model and performing curve fitting with the least square method, the continuous relative coefficient of the reactor in the entire frequency range is calculated, and then the parameters of the established digital filter are obtained according to the continuous relative coefficient, and then the digital filter The skin effect filter is obtained by decomposing and cascading. After processing the current passing through the collection reactor, it is substituted into the skin effect filter, and then calculated to obtain the equivalent thermal current of the reactor. The method for calculating the equivalent thermal current proposed by the invention can simulate the skin effect in the whole frequency range, which greatly reduces the amount of computation. At the same time, the invention also maintains a high degree of calculation accuracy and is easy to implement in the protection device.

Description of drawings

Fig. 1 is a schematic flowchart of an equivalent thermal current calculation method according to an embodiment of the present invention.

detailed description

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

The calculation method of the equivalent thermal current of the skin effect of the reactor, respectively, the current collected from the reactor is sequentially performed: high-pass filtering, skin effect filtering, square operation, low-pass filtering, and square root operation to calculate the value of the reactor, etc. Effective thermal current, as shown in Figure 1, the specific steps are as follows:

Step (1), high-pass filtering:

In the process of high-voltage direct current transmission, the current I(t) on the reactor is collected and processed by a second-order Butterworth high-pass filter (cutoff frequency is 15Hz) to obtain the current I'(t), reaching The purpose of filtering out the DC component.

The expression of the collected instantaneous current value I(t) on the reactor is as follows:

$\mathrm{<span\; class="notranslate">\; I</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\underset{\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{\mathrm{<span\; class="notranslate">\; no</span>}}{<span\; class="notranslate">\; \&Sigma;</span>}}{\mathrm{<span\; class="notranslate">\; A</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}}<span\; class="notranslate">\; \&CenterDot;</span>\mathrm{<span\; class="notranslate">\; the\; s</span>}\mathrm{<span\; class="notranslate">\; i</span>}\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}\mathrm{<span\; class="notranslate">\; \&omega;</span>}\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&phi;</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; A</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

Among them, R ₁ , R ₂ ... R _k are the harmonic impedance of the reactor under each harmonic current. A ₁ , A ₂ ... A _n is the peak value of each harmonic current component in the collected reactor current instantaneous value I(t); is the phase of each harmonic current component; k is the harmonic order of each harmonic component, k=1,2...n; ω is the angular frequency of the fundamental wave.

The expression of current I'(t) is as follows:

Among them, R ₁ , R ₂ ... R _k are the harmonic impedance of the reactor under each harmonic current. A ₁ , A ₂ ... A _n is the peak value of each harmonic current component in the collected reactor current instantaneous value I(t); is the phase of each harmonic current component; k is the harmonic order of each harmonic component, k=1,2...n; ω is the angular frequency of the fundamental wave.

Step (2), skin effect filtering:

The current I'(t) obtained after step (1) is processed through the established skin effect filter, as follows:

1) Perform preliminary processing according to the relative impedance coefficient at the characteristic harmonic point provided by the reactor manufacturer, that is, set the relative coefficient of the fundamental wave at the harmonic point to 1, and set a relative coefficient of the highest harmonic and compare these coefficients Carry out root number processing.

2) A polynomial model is established as a reference model, and the relative impedance coefficient after the above processing is substituted into the reference model, and the least square method is used for curve fitting to obtain the continuous relative coefficient of the reactor in the entire frequency range.

The established polynomial model expression is as follows:

p(x)＝p ₁ x ⁿ +p ₂ x ^n-1 +...+p _n x+p _n+1

Among them, p ₁ , p ₂ …p _n , p _n+1 are the coefficients of the polynomial, using the obtained relative impedance system, use the least square method to perform curve fitting, and obtain the polynomial parameters p ₁ , p ₂ …p _n ,p _n+1 ; x is the harmonic order; p(x) is the relative impedance coefficient under a certain harmonic order; p(x) is the continuous impedance coefficient in the entire frequency range to be obtained, and n is the order of the polynomial.

3) Establish a digital filter with a non-recursive filter as a reference, and use the continuous relative impedance coefficient obtained in 2) as the expected frequency response of the digital filter, and substitute it into the constructed Yule-Walker equation, and the solution value of the equation is is the parameter of the established digital filter.

4) Perform a root-finding operation on the numerator and denominator polynomials of the digital filter constructed above, and then select two roots as a group to decompose the high-order polynomials into multiple second-order polynomials. This decomposes a high-order digital filter into a cascade of multiple second-order filters. Multiple cascaded second-order digital filters are skin effect filters.

5) The current I'(t) obtained above is processed by the skin effect filter to obtain the current I″(t), the expression is as follows:

Among them, R ₁ , R ₂ ... R _k are the harmonic impedance of the reactor under each harmonic current. A ₁ , A ₂ ... A _n is the peak value of each harmonic current component in the collected reactor current instantaneous value I(t); is the phase of each harmonic current component; k is the harmonic order of each harmonic component, k=1,2...n; ω is the angular frequency of the fundamental wave.

Step (3), square operation:

The current I″(t) obtained above is processed by open operation to obtain I″’(t), the expression is as follows:

Formula (4) can be transformed into:

Among them, R ₁ , R ₂ ... R _k are the harmonic impedance of the reactor under each harmonic current. A ₁ , A ₂ ... A _n is the peak value of each harmonic current component in the collected reactor current instantaneous value I(t); is the phase of each harmonic current component; k is the harmonic order of each harmonic component, k=1,2...n; ω is the angular frequency of the fundamental wave.

From formula (5), it can be concluded that I″'(t) contains DC component and AC component, and the DC component is the square sum of the effective value of each harmonic current.

Step (4), in order to extract the DC component in the above-mentioned current I"'(t), carry out first-order low-pass filtering to the current I"'(t), and filter to obtain the current I""(t), the expression is as follows:

${\mathrm{<span\; class="notranslate">\; I</span>}}^{<span\; class="notranslate">\; \&prime;</span><span\; class="notranslate">\; \&prime;</span><span\; class="notranslate">\; \&prime;</span><span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\underset{\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{\mathrm{<span\; class="notranslate">\; no</span>}}{<span\; class="notranslate">\; \&Sigma;</span>}}<span\; class="notranslate">\; (</span>\frac{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}}}{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}<span\; class="notranslate">\; \&CenterDot;</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}{{\mathrm{<span\; class="notranslate">\; A</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; \&CenterDot;</span><span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 6</span>}<span\; class="notranslate">\; )</span>$

Among them, R ₁ , R ₂ ... R _k are the harmonic impedance of the reactor under each harmonic current. A ₁ , A ₂ ... A _n is the peak value of each harmonic current component in the collected reactor current instantaneous value I(t); k is the harmonic order of each harmonic component, k=1,2. ..n.

Step (5), finally, square the obtained current I""(t), and calculate the equivalent thermal current I _{eq_RMS} of the reactor, the expression is as follows:

${\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; e</span>}\mathrm{<span\; class="notranslate">\; q</span>}<span\; class="notranslate">\; \_</span>\mathrm{<span\; class="notranslate">\; R</span>}\mathrm{<span\; class="notranslate">\; m</span>}\mathrm{<span\; class="notranslate">\; S</span>}}<span\; class="notranslate">\; =</span>\sqrt{\underset{\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{\mathrm{<span\; class="notranslate">\; no</span>}}{<span\; class="notranslate">\; \&Sigma;</span>}}<span\; class="notranslate">\; (</span>\frac{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}}}{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}<span\; class="notranslate">\; \&Center\; Dot;</span>\frac{{{\mathrm{<span\; class="notranslate">\; A</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 7</span>}<span\; class="notranslate">\; )</span>$

Among them, R ₁ , R ₂ ... R _k are the harmonic impedance of the reactor under each harmonic current. A ₁ , A ₂ ... A _n is the peak value of each harmonic current component in the collected reactor current instantaneous value I(t); k is the harmonic order of each harmonic component, k=1,2. ..n.

In this embodiment, the second-order Butterworth high-pass filter is used to filter the current collected by the reactor, and the square operation, low-pass filter and square root operation are performed on the current obtained after passing through the skin effect filter. These methods and the calculation models established therein are all prior art, so they will not be repeated here.

Based on the idea of the above method, this embodiment also proposes a calculation device for the equivalent thermal current of the skin effect of the reactor. The device includes: continuous relative impedance coefficient module, skin effect filter module and equivalent thermal current module, as follows:

1) Continuous relative impedance coefficient module: obtain the relative impedance coefficient of the characteristic harmonic point of the reactor, substitute the relative impedance coefficient into the established polynomial model, and use the least square method for curve fitting, so as to obtain the reactor at the entire frequency Range continuous relative coefficients;

2) Skin effect filter module: construct a digital filter, decompose the digital filter into not less than one sub-filter cascade, and then form a skin effect filter;

3) Equivalent thermal current module: After preliminary processing, the current on the collection reactor is substituted into the skin effect filter for filtering, and the filtered current is further processed to obtain the equivalent thermal current of the reactor .

The specific implementation of each module in the above-mentioned device is the same as the specific implementation of the above-mentioned "Calculation Method of Reactor Skin Effect Equivalent Thermal Current", so it will not be repeated here.

Under the idea given by the present invention, the technical means in the above-mentioned embodiments are transformed, replaced, and modified in ways that are easy for those skilled in the art, and the functions played are basically the same as those of the corresponding technical means in the present invention. 1. The purpose of the invention realized is also basically the same, and the technical solution formed in this way is formed by fine-tuning the above-mentioned embodiments, and this technical solution still falls within the protection scope of the present invention.

Claims (10)

1. the computational methods of reactor kelvin effect equivalent heat electric current, it is characterised in that step is as follows:

Step 1, the relative impedances coefficient of the characteristic harmonics point of the reactor of acquisition, relative impedances coefficient is substituted into the multinomial model set up, and uses method of least square to carry out curve fitting, thus obtaining reactor at whole frequency range continuous print relative coefficient；

Step 2, constructs digital filter, will be decomposed in digital filter no less than a sub-wave filter cascade, and then forms kelvin effect wave filter；

Step 3, is updated to kelvin effect wave filter after preliminary treatment to the electric current gathered on reactor and is filtered, and the electric current that filtering is obtained is further processed again, can try to achieve the equivalent heat electric current of reactor.

2. the computational methods of reactor kelvin effect equivalent heat electric current according to claim 1, it is characterised in that relative impedances coefficient is carried out process refer to described in step 1: set in described harmonic wave electricity the relative coefficient of first-harmonic as 1；Then, set the relative coefficient of a most higher hamonic wave point, and this coefficient is opened radical sign process；

The multinomial model expression formula set up is as follows:

P (x)=p₁xⁿ+p₂x^n-1+...+p_nx+p_n+1

Wherein, p (x) is the continuous impedance factor in whole frequency range；p₁,p₂…p_n,p_n+1For polynomial coefficient, utilize the relative impedances system obtained, utilize method of least square to carry out curve fitting, obtain polynomial parameter p₁,p₂…p_n,p_n+1；X is overtone order；N is polynomial exponent number.

3. the computational methods of reactor kelvin effect equivalent heat electric current according to claim 1, it is characterized in that, the parameter in the digital filter described in step 2 is to obtain by the continuous print obtained in step 1 relative coefficient is updated to the Yule-Walker equation solution set up.

4. the computational methods of reactor kelvin effect equivalent heat electric current according to claim 1, it is characterized in that, in described step 2, molecule in digital filter and denominator polynomials are carried out rooting operation, choose 2 roots as one group, thus realizing the cascade being decomposed into by digital filter no less than a second order filter, this second order filter is described subfilter.

5. the computational methods of reactor kelvin effect equivalent heat electric current according to claim 1, it is characterised in that the described preliminary treatment in step 3 is that the electric current gathered on reactor is carried out high-pass filtering；

The expression formula trying to achieve equivalent current is:

Wherein, R₁,R₂…R_kFor reactor harmonic impedance under individual harmonic current；A_kPeak value for the individual harmonic current component in reactor current instantaneous value I (t) that collects；Phase place for individual harmonic current component；K is the overtone order of each harmonic component, k=1,2...n；ω is the angular frequency of first-harmonic；

Electric current after kelvin effect filter filtering is further processed and refers to: the electric current obtained after kelvin effect wave filter is sequentially carried out square operation, high-pass filtering and extracting operation, and then tries to achieve the equivalent heat electric current of reactor.

6. the calculation element of reactor kelvin effect equivalent heat electric current, it is characterised in that this device includes: continuous phase is to impedance factor module, kelvin effect filter module and equivalent heat current module, specific as follows:

1) continuous phase is to impedance factor module: the relative impedances coefficient of the characteristic harmonics point of the reactor of acquisition, relative impedances coefficient is substituted into the multinomial model set up, and use method of least square to carry out curve fitting, thus obtain reactor at whole frequency range continuous print relative coefficient；

2) kelvin effect filter module: structure digital filter, will be decomposed in digital filter no less than a sub-wave filter cascade, and then forms kelvin effect wave filter；

3) equivalent heat current module: the electric current gathered on reactor is updated to kelvin effect wave filter after preliminary treatment and is filtered, the electric current that filtering is obtained is further processed again, can try to achieve the equivalent heat electric current of reactor.

7. the calculation element of reactor kelvin effect equivalent heat electric current according to claim 6, it is characterised in that continuous phase is to carrying out process to relative impedances coefficient and refer to described in impedance factor module: set in described harmonic wave electricity the relative coefficient of first-harmonic as 1；Then, set the relative coefficient of a most higher hamonic wave point, and this coefficient is opened radical sign process；

The multinomial model expression formula set up is as follows:

P (x)=p₁xⁿ+p₂x^n-1+...+p_nx+p_n+1

Wherein, p (x) is the continuous impedance factor in whole frequency range；p₁,p₂…p_n,p_n+1For polynomial coefficient, utilize the relative impedances system obtained, utilize method of least square to carry out curve fitting, obtain polynomial parameter p1, p2 ... p_n,p_n+1；X is overtone order；N is polynomial exponent number.

8. the calculation element of reactor kelvin effect equivalent heat electric current according to claim 6, it is characterized in that, the parameter in the digital filter described in kelvin effect filter module is to obtain by the continuous print obtained in step 1 relative coefficient is updated to the Yule-Walker equation solution set up.

9. the calculation element of reactor kelvin effect equivalent heat electric current according to claim 6, it is characterized in that, in described kelvin effect filter module, molecule in digital filter and denominator polynomials are carried out rooting operation, choose 2 roots as one group, thus realizing the cascade being decomposed into by digital filter no less than a second order filter, this second order filter is described subfilter.

10. the calculation element of reactor kelvin effect equivalent heat electric current according to claim 6, it is characterised in that the described preliminary treatment in equivalent heat current module is that the electric current gathered on reactor is carried out high-pass filtering；

The expression formula trying to achieve equivalent current is:

Wherein, R₁,R₂…R_kFor reactor harmonic impedance under individual harmonic current；A_kPeak value for the individual harmonic current component in reactor current instantaneous value I (t) that collects；Phase place for individual harmonic current component；K is the overtone order of each harmonic component, k=1,2...n；ω is the angular frequency of first-harmonic；

Electric current after kelvin effect filter filtering is further processed and refers to: the electric current obtained after kelvin effect wave filter is sequentially carried out square operation, high-pass filtering and extracting operation, and then tries to achieve the equivalent heat electric current of reactor.