CN103389403B - A kind of high-voltage alternating system harmonics voltage measurement method based on wave filter - Google Patents

Abstract

The invention provides a kind of high-voltage alternating system harmonics voltage measurement method based on wave filter, be specially: in each branch road of the alternating current filter of high-voltage alternating system, seal in current transformer, utilize the electric current measured and obtain, in conjunction with each device parameter values of alternating current filter or the frequency versus impedance characteristic of known wave filter on AC side, calculate the harmonic voltage of high-voltage alternating system.The present invention is simple to operate, and only need carry out simple transformation on the basis of conventional AC wave filter can realize, and the precision measuring harmonic voltage is high, extends the function of alternating current filter, has comparatively high performance-price ratio; The present invention has very high using value and marketing prospect in the occasion of high-voltage alternating system harmonics voltage measurement.

Description

A kind of high-voltage alternating system harmonics voltage measurement method based on wave filter

Technical field

The present invention relates to a kind of high-voltage alternating system harmonics voltage measurement method based on wave filter.

Technical background

The increasing voltage distortion problem of high-voltage alternating electric system that causes of the application of nonlinear-load in electric system is more and more serious.Power supply department and scientific research institution, in the urgent need to measuring the voltage harmonic of high-voltage alternating electric system, to understand the voltage harmonic situation of high-pressure system, make harness of harmonic wave targetedly, the design correctness of checking alternating current filter and validity.

But in currently used high pressure harmonic measuring method and equipment, adopt the scheme of resistor divider and capacitor dividing potential drop to need to adopt special equipment, and these equipment volume are large, expensive.Capacitance type potential transformer is adopted to carry out the method that high pressure harmonic measure is most convenient economy, but because the internal resonance condition of capacitance type potential transformer under harmonic condition will be destroyed, measuring harmonic wave by there is larger error, directly cannot apply conventional capacitive-type voltage transformer (VT) and carrying out high pressure harmonic measure.

Also there is the frequency response characteristic having researched and analysed capacitance type potential transformer at present, after utilizing this frequency response characteristic to revise capacitance type potential transformer double measurement voltage, derive on high-tension side voltage harmonic.But this scheme needs the frequency response characteristic of the various dissimilar capacitance type potential transformer of off-line analysis, need detailed construction and the element parameter of knowing capacitance type potential transformer, and frequency response characteristic under different loading conditions is also different.Therefore this method realizes comparatively complicated, limits its application.

Currently used all alternating current filters all can be divided into two parts, and namely (impedance of fundamental frequency is Z to first branch road _{h (1)}, China's fundamental frequency is 50Hz) and second branch road.Wherein second branch road is made up of multiple branch circuit parallel connection again that (impedance of fundamental frequency is respectively Z _{l1 (1)}, Z _{l2 (1)}..., Z _{ln (1)}).Therefore, if simply can transform widely used alternating current filter in current high-voltage alternating system, design the alternating current filter simultaneously taking into account regular alternating current harmonic function and high-voltage alternating harmonic measurement function, namely can provide high-precision high pressure harmonic measure while carrying out harmonic filtration.Thus provide the scheme that a kind of cost performance is very high for the harmonic voltage measurement realizing high-voltage alternating system, have great practical value and marketing prospect.

Summary of the invention

For background technology Problems existing, the invention provides a kind of high-voltage alternating system harmonics voltage measurement method based on wave filter.

Currently used all alternating current filters all can be divided into two parts, and namely (impedance of fundamental frequency is Z to first branch road _{h (1)}, China's fundamental frequency is 50Hz) and second branch road.Wherein second branch road is made up of multiple branch circuit parallel connection again that (impedance of fundamental frequency is respectively Z _{l1 (1)}, Z _{l2 (1)}..., Z _{ln (1)}).The present invention seals in current transformer in each parallel branch in second branch road of conventional AC wave filter, Fourier decomposition is carried out to measuring the electric current obtained, obtain individual harmonic current, according to composition and the component parameters of alternating current filter, calculate each harmonic voltage of high-voltage alternating system.Also can utilize the impedance frequency characteristics measuring electric current and the known alternating current filter obtained, calculate each harmonic voltage of high-voltage alternating system.The invention provides the high-voltage alternating harmonic voltage measurement means that a kind of cost performance is higher, to provide the necessary technical means for analyzing high-voltage alternating system harmonics situation.

Technical scheme of the present invention is as follows:

Based on a high-voltage alternating system harmonics voltage measurement method for wave filter, in each parallel branch in second branch road of alternating current filter, seal in current transformer S respectively ₁, S ₂..., S _n, and each current transformer seals in the earth terminal of each parallel branch; Measure the electric current flowing through current transformer, and utilize each harmonic voltage of the Current calculation high-voltage alternating system recorded.

The process of each harmonic voltage of the Current calculation high-voltage alternating system that described utilization records is: carry out Fourier decomposition to measuring the electric current obtained, obtain individual harmonic current, according to composition and the component parameters of alternating current filter, calculate each harmonic voltage of high-voltage alternating system, specifically comprise the following steps:

Step 1, solve the current i that first branch road of obtaining alternating current filter flows through _zH;

Step 2, the parallel branch k selected in second branch road, utilize Fourier transformation method to the current i of this parallel branch _zLkcarry out Harmonic Decomposition, and by current i _zLkin h subharmonic be written as phasor form;

Step 3, solve and obtain second branch voltage u _zLin h subharmonic;

Step 4, utilize Fourier transformation method, to current i _zHcarry out Harmonic Decomposition, and by current i _zHin h subharmonic be written as phasor form;

Step 5, solve and obtain first branch voltage u _zHin h subharmonic;

Step 6, by the results added in step 3 and step 5, try to achieve high-voltage alternating system voltage u _sh subharmonic voltage;

Step 7, repetition step 1-6, try to achieve high-voltage alternating system voltage u _seach harmonic voltage.

The process of each harmonic voltage of the Current calculation high-voltage alternating system that described utilization records is: according to the electric current recorded and in conjunction with the impedance frequency characteristics of known alternating current filter, calculate each harmonic voltage of high-voltage alternating system, specifically comprise the following steps:

Step 1, solve the current i that first branch road of obtaining alternating current filter flows through _zH;

Step 2, to i _zHcarry out Fourier decomposition, obtain current i _zHthe effective value I of h subharmonic _{zH (h)}with phasing degree θ _{zH (h)}, h=1,2 ..., m;

Step 3, the impedance frequency characteristics curve of alternating current filter is utilized to find the impedance magnitude Z of alternating current filter under h subharmonic _(h)and phasing degree the I of integrating step 2 gained _{zH (h)}and θ _{zH (h)}calculate high-voltage alternating system voltage u _sh subharmonic voltage;

Step 4, repetition step 1-3, try to achieve high-voltage alternating system voltage u _seach harmonic voltage.

Compared with prior art, the invention has the beneficial effects as follows:

The present invention only need seal in current transformer in conventional AC wave filter, utilizes the electric current of the current transformer recorded can calculate each harmonic voltage of high-voltage alternating system.The present invention is simple to operate, it is convenient to realize, and measuring voltage harmonic wave precision is high, makes alternating current filter while having traditional harmonic filtration function, there is high-voltage alternating harmonic voltage measurement function, in the occasion of high voltage harmonic voltage measurement, there is very high using value and marketing prospect.

Accompanying drawing explanation

Fig. 1 is schematic diagram of the present invention;

Fig. 2 is the schematic diagram of the embodiment of the present invention 2;

Fig. 3 is the impedance frequency characteristics figure of the double tunning alternating current filter of the embodiment of the present invention 2.

Embodiment

Below in conjunction with accompanying drawing, the present invention will be further described.

As shown in Figure 1, currently used all alternating current filters all can be divided into two parts, and namely (impedance of fundamental frequency is Z to first branch road _{h (1)}, China's fundamental frequency is 50Hz) and second branch road.Wherein second branch road is made up of multiple branch circuit parallel connection again that (impedance of fundamental frequency is respectively Z _{l1 (1)}, Z _{l2 (1)}..., Z _{ln (1)}).The present invention seals in current transformer S respectively in each parallel branch of second branch road ₁, S ₂..., S _n.Should be noted to reduce current transformer S simultaneously ₁, S ₂..., S _ninsulating requirements, each current transformer need seal in the part of each parallel branch near earth point.

The invention provides two embodiments to solve high-pressure side alternating voltage u _sharmonic content.

Embodiment 1

Step 1, solve the current i obtaining first branch road and flow through _zH:

$i_{\mathrm{ZH}}=\underset{k=1}{\overset{n}{\mathrm{\Σ}}}{i}_{\mathrm{ZLK}}---\left(1\right)$

Wherein, i _zLkfor the electric current of a kth parallel branch in second branch road of recording, k=1,2 ..., n;

Step 2, voltage u due to each parallel branch of second branch road _zLbe identical, the electric current of arbitrary branch road can be utilized to solve this voltage, with impedance of fundamental frequency in second branch road for Z _{l1 (1)}the current i of parallel branch _zL1for example is described: utilize ripe Fourier Transform Technique, can to the current i recorded _zL1carry out Harmonic Decomposition:

$i_{\mathrm{ZLl}}=\sqrt{2}\·\underset{h=1}{\overset{m}{\mathrm{\Σ}}}(I_{\mathrm{ZLl}\left(h\right)}\·\sin ({\mathrm{\ω}}_{h}t+{\mathrm{\θ}}_{\mathrm{ZLl}\left(h\right)}))---\left(2\right)$

Wherein: h is overtone order, m is paid close attention to most higher harmonics number of times (generally get 30 times enough); ω _h=2 π hf are h subharmonic angular frequency, and wherein f is work frequency, and China is 50Hz; T is the time; I _{zL1 (h)}and θ _{zL1 (h)}be respectively current i _zL1in the effective value of h subharmonic and phasing degree.

By current i _zL1in h subharmonic be written as phasor form:

${\stackrel{\·}{I}}_{\mathrm{ZLl}\left(h\right)}=I_{\mathrm{ZLl}}\∠{\mathrm{\θ}}_{\mathrm{ZLl}\left(h\right)}---\left(3\right)$

Step 3, solve and obtain u _zLin h subharmonic be:

Wherein Z _{l1 (h)}for impedance of fundamental frequency is Z _{l1 (1)}the impedance of parallel branch under h subharmonic.Because all parallel branches are all be made up of resistance, electric capacity and inductance element, when these component parameters known, be easy to solve and obtain Z _{l1 (h)}.

Step 4, utilize Fourier Transform Technique, solve to according to formula (1) current i obtained _zHcarry out Harmonic Decomposition:

$i_{\mathrm{ZH}}=\sqrt{2}\·\underset{h=1}{\overset{m}{\mathrm{\Σ}}}(I_{\mathrm{ZH}\left(h\right)}\·\sin ({\mathrm{\ω}}_{h}t+{\mathrm{\θ}}_{\mathrm{ZH}\left(h\right)}))---\left(5\right)$

Wherein: I _{zH (h)}and θ _{zH (h)}be respectively current i _zHin the effective value of h subharmonic and phasing degree.

By current i _zHin h subharmonic be written as phasor form:

${\stackrel{\·}{I}}_{\mathrm{ZH}\left(h\right)}=I_{\mathrm{ZH}\left(h\right)}\∠{\mathrm{\θ}}_{\mathrm{ZH}\left(h\right)}---\left(6\right)$

Step 5, solve and obtain first branch voltage u _zHin h subharmonic be:

${\stackrel{\·}{U}}_{\mathrm{ZH}\left(h\right)}={\stackrel{\·}{I}}_{\mathrm{ZH}\left(h\right)}\·Z_{H\left(h\right)}---\left(7\right)$

Wherein Z _{h (h)}for impedance of fundamental frequency is Z _{h (1)}the impedance of first branch road under h subharmonic.Because first all branch roads is all be made up of resistance, electric capacity and inductance element, when these component parameters known, be easy to solve and obtain Z _{h (h)}.

Step 6, by the results added in step 3 and step 5, try to achieve high-voltage AC transmission system AC voltage u _sh subharmonic voltage;

Then ac high-voltage side voltage u _sin h subharmonic voltage be:

${\stackrel{\·}{U}}_{S\left(h\right)}={\stackrel{\·}{U}}_{\mathrm{ZH}\left(h\right)}+{\stackrel{\·}{U}}_{\mathrm{ZL}\left(h\right)}---\left(8\right)$

Step 7, repeat step 1-6, to all subharmonic (h=1,2 ..., m) all carry out above-mentioned shown calculating, high-voltage system voltage u can be calculated _seach harmonic voltage, namely these voltages are carry out the value required for frequency analysis.

Embodiment 2

Step 1, solve the current i obtaining first branch road and flow through according to formula (1) _zH;

Step 2, to i _zHcarry out Fourier decomposition, solve and obtain current i _zHthe effective value I of h subharmonic _{zH (h)}with phasing degree θ _{zH (h)}, h=1,2 ..., m;

Step 3, the impedance frequency characteristics curve of wave filter on AC side is utilized to find the impedance magnitude Z of wave filter on AC side under h subharmonic _(h)and phasing degree the I of integrating step 2 gained _{zH (h)}and θ _{zH (h)}calculate high-voltage AC transmission system AC voltage u _sh subharmonic voltage;

For designed alternating current filter, its impedance frequency characteristics is very important characteristic, know when designing, impedance magnitude and the phasing degree value at different frequencies of what impedance frequency characteristics provided is whole alternating current filter, and be depicted as the form of curve.Therefore, the impedance magnitude Z of alternating current filter under h subharmonic can be found by this family curve _(h)and phasing degree following formula is utilized to calculate ac high-voltage side voltage u _sin h subharmonic voltage be:

Step 4, repeat step 1-3, to all subharmonic (h=1,2 ..., m) all carry out above-mentioned shown calculating, high-voltage system voltage u can be calculated _seach harmonic voltage, namely these voltages are carry out the value required for frequency analysis.

The specific implementation of second method is described below in conjunction with Fig. 2 and Fig. 3.C in Fig. 2 ₁, L ₁, C ₂, L ₂, R ₂the element of conventional double tunning alternating current filter, S ₁and S ₂for the current transformer sealed in.Fig. 3 is the impedance frequency characteristic of this alternating current filter, and the Z curve in figure is the amplitude versus frequency characte of impedance, and curve is the phase-frequency characteristic of impedance.Impedance magnitude and the phasing degree that such as can find this wave filter under 20 subharmonic are respectively 66 Ω and 92 °, in conjunction with the current i calculated _zHthe effective value I of the 20th subharmonic _{zH (20)}with phasing degree θ _{zH (20)}, according to formula (9), high-voltage system voltage u can be calculated _s20 subharmonic voltages be:

Can see, this method can carry out high-voltage system voltage u more quickly _seach harmonic voltage calculate.

The present invention seals in current transformer in regular alternating current filter branches, Fourier decomposition is carried out to measuring the electric current obtained, obtain individual harmonic current, according to composition and the component parameters of alternating current filter, the each harmonic voltage of high-pressure system can be calculated, also can utilize the impedance frequency characteristics of known alternating current filter, calculate each harmonic voltage of high-pressure system, thus the analysis of high-pressure system harmonic voltage can be carried out.High-voltage harmonic measurement scheme based on alternating current filter of the present invention only simply need be improved on the basis of regular alternating current wave filter, realize simple, for the accurate measurement realizing high-voltage alternating harmonic voltage provides important technological means, there is very high practical value and wide marketing application prospect.

Above embodiment is used for illustrative purposes only, but not limitation of the present invention, person skilled in the relevant technique, without departing from the spirit and scope of the present invention, can also make various conversion or modification, therefore all equivalent technical schemes also should belong within category of the present invention.

Claims (2)

1. based on a high-voltage alternating system harmonics voltage measurement method for wave filter, it is characterized in that: in each parallel branch in second branch road of alternating current filter, seal in current transformer S respectively ₁, S ₂..., S _n, and each current transformer seals in the earth terminal of each parallel branch; Measure the electric current flowing through current transformer, and utilize each harmonic voltage of the Current calculation high-voltage alternating system recorded;

The process of each harmonic voltage of the Current calculation high-voltage alternating system that described utilization records is: carry out Fourier decomposition to measuring the electric current obtained, obtain individual harmonic current, according to composition and the component parameters of alternating current filter, calculate each harmonic voltage of high-voltage alternating system, specifically comprise the following steps: step 1, solve the current i that first branch road of obtaining alternating current filter flows through _zH;

Step 2, the parallel branch k selected in second branch road, utilize Fourier transformation method to the current i of this parallel branch _zLkcarry out Harmonic Decomposition, and by current i _zLkin h subharmonic be written as phasor form;

Step 3, solve and obtain second branch voltage u _zLin h subharmonic;

Step 4, utilize Fourier transformation method, to current i _zHcarry out Harmonic Decomposition, and by current i _zHin h subharmonic be written as phasor form;

Step 5, solve and obtain first branch voltage u _zHin h subharmonic;

Step 6, by the results added in step 3 and step 5, try to achieve high-voltage alternating system voltage u _sh subharmonic voltage;

Step 7, repetition step 1-6, try to achieve high-voltage alternating system voltage u _seach harmonic voltage.

2. based on a high-voltage alternating system harmonics voltage measurement method for wave filter, it is characterized in that: in each parallel branch in second branch road of alternating current filter, seal in current transformer S respectively ₁, S ₂..., S _n, and each current transformer seals in the earth terminal of each parallel branch; Measure the electric current flowing through current transformer, and utilize each harmonic voltage of the Current calculation high-voltage alternating system recorded;

The process of each harmonic voltage of the Current calculation high-voltage alternating system that described utilization records is: according to the electric current recorded and in conjunction with the impedance frequency characteristics of known alternating current filter, calculate each harmonic voltage of high-voltage alternating system, specifically comprise the following steps:

Step 1, solve the current i that first branch road of obtaining alternating current filter flows through _zH;

Step 2, to i _zHcarry out Fourier decomposition, obtain current i _zHthe effective value I of h subharmonic _{zH (h)}with phasing degree θ _{zH (h)}, h=1,2 ..., m;

Step 3, the impedance frequency characteristics curve of alternating current filter is utilized to find the impedance magnitude Z of alternating current filter under h subharmonic _(h)and angle phi _(h), the I of integrating step 2 gained _{zH (h)}and θ _{zH (h)}calculate high-voltage alternating system voltage u _sh subharmonic voltage;

Step 4, repetition step 1-3, try to achieve high-voltage alternating system voltage u _seach harmonic voltage.