CN106209283A - A kind of power line communication channel for variable working condition environment analyzes method - Google Patents

Abstract

The invention discloses a kind of power line communication channel for variable working condition environment and analyze method, comprise the following steps: A. carries out power line channel test to variable working condition environment；B. use the noise of MATLAB emulation power line channel, obtain various simulator and noise；C. the synthesis of various simulator and noises is obtained composite noise, use wigner-ville distribution, certainly compose window function, the wigner-ville distribution of the cross interference that is inhibited by based on Short Time Fourier Transform；D. judge channel conditions by the wigner-ville distribution of analysis noise signal, provide foundation for power line communication channel carrier wave frequency range.The present invention is possible not only to find out the noise size of each frequency component, it is also possible to know the noise time variation size in this frequency range, the i.e. stationarity of noise.

Description

A kind of power line communication channel for variable working condition environment analyzes method

Technical field

The invention belongs to low voltage power line communication channel technical field of measurement and test, be specifically related to a kind of electric power for variable working condition environment Line Communication channel analysis method.

Background technology

Owing to need not set up special communication line, power line communication technology has low cost, simple feature of constructing, It is one of the basic communication mode of power system, is also the Primary communication mode of power system.Simultaneously because power line network rises Just being used only to transmit electric energy, be not to aim at communication scheme, its severe channel and complicated noise circumstance are the most serious, become Restrict the bottleneck of its technical progress.There is variable working condition load the most now in power system in a large number, variable working condition load is not to begin Run on declared working condition eventually, and be in the duty of variable working condition, be adapted to the Rapid Variable Design of load, the most large-scale work Ore deposit enterprise, the load of wherein most is to be dragged by sensing multiple-speed motor, and this equipment driven by heavy-duty motor exists In running, energy consumption is relatively big, and its residing power line channel feature may exist relative to conventional low power consumer platform district Some differences, power line noise also can be different on carrier module communication impact, it is therefore necessary to carry out the on-the-spot test being correlated with.Base In this, situation about being all widely varied for load and operating mode, the application is under the oil-field oil pumper motor running environment of North China Power line channel characteristic has carried out on-the-spot test, including impedance operator, noise characteristic and the test of plc communication success rate. OFDM (Orthogonal Frequency Division Multiplexig, OFDM) is a kind of multi-carrier transmission Technology, can effectively suppress intersymbol interference, is greatly reduced the complexity of channel equalization, and can selectively use frequency Spectrum, self-adaptive electric power line carrier communication technology based on OFDM is the key technology of following PLC system development and application, subcarrier Dynamic optimized combination is closely related with power line channel situation, by cognitive channel conditions can with intelligent management PLC signal spectrum, Avoid noise jamming.Time domain and traditional frequency-domain analysis owing to measuring noise can not reflect the time-frequency characteristic of signal, and Noise signal non-stationary, can accurately analyze the noise-like of channel by noise signal carries out time-frequency combination analysis Condition, the time domain and frequency domain combined analysis of wigner-ville distribution is to be analyzed signal on time-frequency joins plane, it is provided that each frequency spectrum The temporal properties of component.When low-voltage power line transmits, total channel characteristic is: carrier signal transmission decay is serious, simultaneously electricity Line of force road can produce during various load running strong interference noise, and the impedance operator of circuit dynamically changes so that carrier wave The receiving efficiency of signal reduces.The decay of carrier signal is relevant with carrier frequency, transmission range and path structure, due to variable working condition Load is not to run on declared working condition all the time, and load has time variation and a randomness, thus attenuation characteristic also will have time variation with Randomness.To drastically change with voltage x current the most in the same time at different nodes during variable working condition load running simultaneously, meeting Produce various interference noise, and impedance operator corresponding to different frequency also can be different.

Originally it is used only to due to power line network transmit electric energy, does not aim at communication scheme, the load in power network Varied, the noise of generation is the most different, and therefore the noise in low voltage power line communication channel is not common Gauss white noise Sound, complicated noise circumstance has become the bottleneck of restriction other technologies progress.Low-voltage power line to realize high-speed communication, must The noise characteristic of power line channel must be fully understood by.According to pertinent literature both domestic and external, noise can be divided into background noise (bag Include colored background noise, narrow-band noise and be asynchronous to the recurrent pulse noise of power frequency) and impulsive noise (include being synchronized with power frequency Recurrent pulse noise and random impulsive noise).Front 3 kinds of noises (respectively colored background noise, narrow-band noise and be asynchronous to power frequency Recurrent pulse noise) change over slowly, and noise amplitude is the least.Rear 2 kinds of noises (are synchronized with the recurrent pulse of power frequency Noise and random impulsive noise) time variation strong, noise amplitude is big, is to cause position or the sudden error code of string in data transmission, The main noise of the biggest error is caused to data transmission.

In order to verify the superiority of time frequency analysis, it is possible to use under MATLAB/SIMULINK emulation Complex Channel environment Noise, this noise synthesizes according to feature and the type of the generation data of above five kinds of noise models, containing abundant impulsive noise, It appeared that the time variation of composite noise is very big, but the frequency characteristic of noise can not be known from this time-domain diagram.And traditional frequency Analysis of spectrum, such as Fourier transformation, although it is known that the frequency characteristic of signal, but cannot provide each spectrum component of signal Time domain is distributed.In other words, if the noise amplitude of a certain frequency is the least, use traditional spectrum analysis that this can be caused to be optimal The illusion of transmission PLC signal frequency, if but this frequency noise time variation is very big, then can affect PLC signal detection, data are passed Defeated cause the biggest error.And Wigner time frequency analysis figure can clearly show the time dependent characteristic of signal intermediate frequency rate, no Only can be seen that the noise size of each frequency component, it is also possible to know the noise time variation size in this frequency range, i.e. noise Stationarity.Being known that by test the noise of power line channel is sufficiently complex, be not additive white Gaussian noise, it is a kind of time-varying Noise.Non-stationary due to noise signal, can accurately analyze letter by noise signal carries out time-frequency combination analysis The noise condition in road.

Due to variable working condition load running complicated mechanism, operating mode and load are in the state of being continually changing, at different nodes Voltage x current can drastically change, and the power line noise produced during operation is difficult to pass through the Realization of Simulation.The application is by North China oil Power line channel characteristic under the pumping-unit motor running environment of field carries out on-the-spot test and believes electric lines of force to analyze variable working condition load The impact of road characteristic.

Summary of the invention

It is an object of the invention to provide a kind of power line communication channel for variable working condition environment and analyze method.

To achieve these goals, the present invention uses following technical scheme.

A kind of power line communication channel for variable working condition environment analyzes method, it is characterised in that comprise the following steps:

A. variable working condition environment is carried out power line channel test；

B. use the noise of MATLAB emulation power line channel, obtain various simulator and noise；

C. the synthesis of various simulator and noises is obtained composite noise, use wigner-ville distribution, by becoming based on Fourier in short-term That changes composes window function certainly, the wigner-ville distribution of the cross interference that is inhibited；

D. channel conditions is judged, for power line communication channel carrier wave frequency range by the wigner-ville distribution of analysis noise signal Foundation is provided.

Further, test described in step A includes testing impedance, noise testing and the test of plc communication success rate.

Further, wigner-ville distribution described in step C is

$W_s(t,f)={\∫}_{-\mathrm{\∞}}^{\mathrm{\∞}}s(t+\frac{\mathrm{\τ}}{2})s^{*}(t-\frac{\mathrm{\τ}}{2})e^{-j2\mathrm{\π}f\mathrm{\τ}}d\mathrm{\τ}---\left(1\right)$

Wherein s (t) is composite noise signal, and t is the time, and τ is integrating factor, and f is by the frequency analyzed, and " * " represents Take complex conjugate, i.e. real part is equal, imaginary part opposite number each other；

The wigner-ville distribution of described suppression cross interference is

W_F(t, f)=W_s(t,f)F(t,w) (2)

Wherein, (t is w) that expression formula is from composing window function to F

$F(t,w)={\left|{\∫}_{-\mathrm{\∞}}^{\mathrm{\∞}}s\left(t\right)h(\mathrm{\τ}-t)e^{-j2\mathrm{\π}f\mathrm{\τ}}d\mathrm{\τ}\right|}^2---\left(3\right)$

Wherein, h is that (t, w) at the impulse response function of time domain for F.

Advantages of the present invention: based on wigner-ville distribution, power line channel noise is carried out time-frequency combination analysis, it is possible to calibrated Really analyze the noise condition of channel, the time dependent characteristic of signal intermediate frequency rate can be clearly illustrated, be possible not only to find out The noise size of each frequency component, it is also possible to know the noise time variation size in this frequency range, the i.e. stationarity of noise.

Accompanying drawing explanation

Fig. 1 is oil pumper electric power system schematic diagram.

Fig. 2 is noise testing block diagram.

Fig. 3 is communication success rate testing scheme figure.

Detailed description of the invention

The present invention will be further described with specific embodiment below in conjunction with the accompanying drawings.

A kind of power line communication channel for variable working condition environment analyzes method, it is characterised in that comprise the following steps:

A. variable working condition environment is carried out power line channel test；

B. use the noise of MATLAB emulation power line channel, obtain various simulator and noise；

C. the synthesis of various simulator and noises is obtained composite noise, use wigner-ville distribution, by becoming based on Fourier in short-term That changes composes window function certainly, the wigner-ville distribution of the cross interference that is inhibited；

D. channel conditions is judged, for power line communication channel carrier wave frequency range by the wigner-ville distribution of analysis noise signal Foundation is provided.

Wherein, test described in step A includes testing impedance, noise testing and the test of plc communication success rate.

Wherein, wigner-ville distribution described in step C is

$W_s(t,f)={\∫}_{-\mathrm{\∞}}^{\mathrm{\∞}}s(t+\frac{\mathrm{\τ}}{2})s^{*}(t-\frac{\mathrm{\τ}}{2})e^{-j2\mathrm{\π}f\mathrm{\τ}}d\mathrm{\τ}---\left(1\right)$

Wherein s (t) is composite noise signal, and t is the time, and τ is integrating factor, and f is by the frequency analyzed, and " * " represents Take complex conjugate, i.e. real part is equal, imaginary part opposite number each other；

The wigner-ville distribution of described suppression cross interference is

W_F(t, f)=W_s(t,f)F(t,w) (2)

Wherein, (t is w) that expression formula is from composing window function to F

$F(t,w)={\left|{\∫}_{-\mathrm{\∞}}^{\mathrm{\∞}}s\left(t\right)h(\mathrm{\τ}-t)e^{-j2\mathrm{\π}f\mathrm{\τ}}d\mathrm{\τ}\right|}^2---\left(3\right)$

Wherein, h is that (t, w) at the impulse response function of time domain for F.

Illustrate as a example by North China Oilfield oil pumper below.North China Oilfield oil pumper is by dragging its sucker rod up and down reciprocatingly The three phase alternating current motor of motion is by neighbouring built on stilts transformer-supplied.Oil pumper electric power system is as shown in Figure 1.Test point selects At the distribution control box on oil pumper side, owing to oil pumper actual power system structure and environment are fairly simple, path structure list One, there is no branched structure, therefore less on attenuation characteristic impact.It addition, North China Oilfield electric company sets in terms of equipment O&M Put some to limit.Test content includes testing impedance, noise testing and the test of plc communication success rate.

The input impedance of low-voltage powerline carrier communication channel refers to drive at sender unit and signal receiving device The equiva lent impedance of power distribution network at Dian, during carrier communication circuit impedance matching, it is possible to increase carrier signal sends, receives the effect of circuit Rate.Test voltage Power Line Carrier Channel tester measurement oilfield electric net pumping-unit motor normally works and two kinds of feelings out of service respectively Power line channel termination at threephase motor under condition, observes impedance situation of change under 30-500kHz low frequency, obtains Impedance operator in the case of electric lines of force variable working condition.

When working oil pumper, the block diagram of distribution box phase noise test is as shown in Figure 2.Power line noise passes through coupling network Coupleding to oscillograph, oscillograph transmits after obtaining noise data storage to PC again and carries out analysis of spectrum.Coupling network mainly has Two effects: one is the forceful electric power isolation making test instrunment with 220v, it is ensured that the peace umbrella of test equipment；Filter in two foot coupling networks The noise tested outside frequency range is filtered by ripple device, reduces interference.Normally work/stop fortune by testing pumping-unit motor respectively Noise during row, can obtain the oil pumper impact on power line channel noise.

During in order to illustrate that pumping-unit motor runs, carrier module communication is affected by power line noise, and the application is respectively in oil pumping Machine work with measure copy controller unidirectional transparent transmission when stopping and communicating success rate, testing scheme figure is as shown in Figure 3.Due to test environment Limit, simulate the decay of actual power line with attenuator, to contrast the antidamping ability of PLC.Add between two copy controller The narrowband carrier attenuator of 45dB, receives copy controller and connects motor distribution box A phase, and amendment sends the transmission gain of copy controller, Testing time is 2 minutes, sends a secondary data every 0.5s, and i.e. sending frame number is 240 frames, then to received signal level with logical Letter success rate carries out record.

By North China oil-field oil pumper power line channel test data are collected and analyze.Test content includes impedance Test, noise testing and the test of plc communication success rate, in the case of can obtaining North China Oilfield oil pumper electric lines of force variable working condition The impact that the characteristic of channel is produced.

According to the characteristic of the various noise of power line channel, use the noise of MATLAB emulation power line channel, obtain various The emulation time-domain diagram of noise, obtains composite noise by the synthesis of various noises, and uses the Wigner time domain scattergram can be clearly Show the time dependent characteristic of signal intermediate frequency rate, be possible not only to find out the noise size of each frequency component, it is also possible to know Noise is in the time variation size of this frequency range, the i.e. stationarity of noise.

Wigner-ville distribution is more common Time-Frequency Analysis Method, has video resolution high, the feature that Energy distribution is concentrated, Owing to belonging to nonlinear transformation, wigner-ville distribution exists cross interference can affect its accuracy, by becoming based on Fourier in short-term Change from spectrum window function can suppress cross interference.The wigner-ville distribution of signal s (t) is

$W_s(t,f)={\∫}_{-\mathrm{\∞}}^{\mathrm{\∞}}s(t+\frac{\mathrm{\τ}}{2})s^{*}(t-\frac{\mathrm{\τ}}{2})e^{-j2\mathrm{\π}f\mathrm{\τ}}d\mathrm{\τ}---\left(1\right)$

Wherein s (t) is composite noise signal, and t is the time, and τ is integrating factor, and f is by the frequency analyzed, and " * " represents Take complex conjugate, i.e. real part is equal, imaginary part opposite number each other.

The wigner-ville distribution of described suppression cross interference is

W_F(t, f)=W_s(t,f)F(t,w) (2)

Wherein, (t is w) that expression formula is from composing window function to F

$F(t,w)={\left|{\∫}_{-\mathrm{\∞}}^{\mathrm{\∞}}s\left(t\right)h(\mathrm{\τ}-t)e^{-j2\mathrm{\π}f\mathrm{\τ}}d\mathrm{\τ}\right|}^2---\left(3\right)$

Wherein, h is that (t, w) at the impulse response function of time domain for F.

Channel conditions is judged, for dynamic optimized combination power line carrier frequency by analyzing the wigner-ville distribution of noise signal Section provides foundation.

It should be noted that, embodiment of above is only in order to illustrate that technical scheme is not intended to limit.Belonging to Field it is to be appreciated by one skilled in the art that the detailed description of the invention of the present invention can be modified or special to portion of techniques Levy and carry out equivalent；Without deviating from the spirit of technical solution of the present invention, it all should contain the technology being claimed in the present invention In the middle of aspects.

Claims (3)

1. the power line communication channel for variable working condition environment analyzes method, it is characterised in that comprise the following steps:

A. variable working condition environment is carried out power line channel test；

B. use the noise of MATLAB emulation power line channel, obtain various simulator and noise；

C. the synthesis of various simulator and noises is obtained composite noise, use wigner-ville distribution, by based on Short Time Fourier Transform From spectrum window function, the wigner-ville distribution of the cross interference that is inhibited；

D. judge channel conditions by the wigner-ville distribution of analysis noise signal, provide for power line communication channel carrier wave frequency range Foundation.

Method the most according to claim 1, it is characterised in that test described in step A includes testing impedance, noise testing And the test of plc communication success rate.

Method the most according to claim 1, it is characterised in that wigner-ville distribution described in step C is

$W_s(t,f)={\∫}_{-\mathrm{\∞}}^{\mathrm{\∞}}s(t+\frac{\mathrm{\τ}}{2})s^{*}(t-\frac{\mathrm{\τ}}{2})e^{-j2\mathrm{\π}f\mathrm{\τ}}d\mathrm{\τ}---\left(1\right)$

Wherein s (t) is composite noise signal, and t is the time, and τ is integrating factor, and f is by the frequency analyzed, and " * " expression takes multiple Conjugation, i.e. real part is equal, imaginary part opposite number each other；

The wigner-ville distribution of described suppression cross interference is

W_F(t, f)=W_s(t,f)F(t,w)(2)

Wherein, (t is w) that expression formula is from composing window function to F

$F(t,w)=|{\∫}_{-\mathrm{\∞}}^{\mathrm{\∞}}s\left(t\right)h(\mathrm{\τ}-t)e^{-j2\mathrm{\π}f\mathrm{\τ}}d\mathrm{\τ}{|}^2---\left(3\right)$

Wherein, h is that (t, w) at the impulse response function of time domain for F.