CN102832970A - Power line state monitoring method and device - Google Patents

Abstract

The invention provides a monitoring method of a power transmission line state in a power line communication system, wherein the monitoring method comprises the following steps: S1. a node A performs framing on the known training sequence and to-be-sent data modulated by an OFDM (orthogonal frequency division multiplexing) technology, and sends signals into a power line through a coupler for transmission; S2. a node B receives sent signals through the coupler, modulates the received signals by utilizing the known training sequence, and extracts transmission data; S3. the node B obtains transmission channel frequency response or impact response by utilizing the known training sequence; S4. the node B analyzes the channel frequency response, extracts relevant information of the transmission line, and obtains the variation information of basic parameters of the transmission line through analyzing the relevant information so as to calculate the channel parameters; and S5. the node B estimates and forecasts the channel state of the power transmission line according to channel parameter variation. According to the method provided by the invention, the state information of the power line can be monitored in real time, and a data collecting device and a communication system are not required to be arranged out of the power transmission line, and the monitoring method of the power transmission line state in the power line communication system has the advantages of good stability, low cost, and the like.

Description

A kind of method of power line status monitoring and device thereof

Technical field

The invention belongs to power line Condition Monitoring Technology field, particularly a kind of method and device thereof based on the technological electric line communication system transmission line status monitoring of OFDM.

Background technology

In the electrical power transmission system,, receive boisterous influences such as wind and frost sleet, can cause the aging of circuit because the middle and long distance power transmission line is exposed on the ground.The aging meeting of circuit causes the transmission usefulness of power line to reduce, and produces more energy dissipation, causes mains supply unstable, even can produce potential safety hazard.For this reason, be crucial in electrical power transmission system for the monitoring of power line, technology that various antagonism power lines are aging and the method that detects the power line state all are suggested and use.

Present detection to the power line ageing state; Under the situation of high pressure and ultra high voltage; Mainly be configuration various characteristics transducer at the transmission node place, be used for transmission line even external environment state are monitored in real time, perhaps line status is analyzed through impedance variations to transfer wire.Be utilized in and overlay the Optical Fiber Transmission nodal information of establishing in the power line and be used for wireline inspection to Central Control Room.For the mesolow circuit,, often can only adopt the mode of artificial line walking to detect and safeguard because circuit is more and complicated.Yet; Being on a grand scale or being in high-risk danger zone when the monitoring electrical network; All can increase greatly for the laying of sensor network and fiber optic network and the cost of maintenance, can cause the great expense incurred of electrical network, and mesolow circuit itself just is difficult to lay auxiliary optical fiber of communication and transducer; The method real-time of impedance analysis is also lower simultaneously, also needs extra professional instrument, and flexibility is not enough.

Along with development of Communication Technique, power line communication has obtained significant progress, has received extensive attention, compares with other various Control Network communication plans, and its advantage is: cost is low, extension is wide, easy construction, a line are dual-purpose.

Summary of the invention

The technical problem that (one) will solve

The technical problem that the present invention will solve is: how to utilize the power line transmission channel that a kind of method and device of transmission line status monitoring are provided.

(2) technical scheme

In order to address the above problem; The invention provides the monitoring method of electric power transfer line states in a kind of electric line communication system; May further comprise the steps: S1, node A are with known training sequence and utilize the data framing to be sent of OFDM technology modulation, and through coupler signal are sent into power line and transmit; S2, Node B receive through coupler and send signal, utilize the known training sequence demodulated received signal, extract the transmission data; S3, Node B utilize known training sequence to obtain transmission channel frequency response or impulse response; S4, Node B analyze channel frequency response, extract the relevant information of transmission line, draw the change information of transmission line basic parameter through the variation of analyzing relevant information, with the calculating channel parameter; S5, Node B change according to channel parameter the power transmission line channel status are estimated and predicted.

Preferably, said training sequence comprises time-domain training sequence, frequency domain training sequence.

Preferably, said OFDM framing mode comprises ZP-OFDM, CP-OFDM and TDS-OFDM.

Preferably, among the step S4, said relevant information comprises that the frequency plot between poor, the adjacent extreme value of the frequency interval between the amplitude of the maximum of channel frequency response, minimizing amplitude, phase place, position, the adjacent extreme value is poor, the cycle of phase response.

Preferably, among the step S4, said transmission line basic parameter comprises the relative dielectric constant ε of dielectric between conductor _r, relative permeability μ _r, angle of loss, electrical length l.

Preferably; Among the step S5; The said variation according to channel parameter estimated and predicts to comprise following corresponding relation to the power transmission line channel status: the aging or residing ambient temperature rising of transmission line of electricity that the relative dielectric constant of dielectric diminishes and representes transmission line between conductor; The diminish magnetic ageing of expression transmission line or because the variation of pressure causes medium that deformation heterogeneous has taken place, the increase of angle of loss representes that transmission line has produced electric aging or because the loss that the external environment variation causes of relative permeability.

Preferably,, then represent the impulse response estimation of channel, pass through DFT (DFT) conversion then and obtain channel frequency response with the convolution of training sequence and receiving sequence if adopt time-domain training sequence; If adopt frequency domain training sequence, then represent the frequency response estimation of channel with receiving sequence and the merchant of the DFT (DFT) that sends sequence.

The present invention also provides the device of transmission line status monitoring in a kind of power communication system, and this device comprises: the data generation unit is used to produce the data of required transmission; The signal modulating unit is used for according to the demand of system the data that produce being carried out the OFDM modulation, and with known training pilot tone and OFDM symbol make up, framing, output to coupler unit; Coupler unit is used for signal with signal modulating unit output and is coupled on the power line and transmits, or is used for that the coupling of the signal on the power line is received and be transferred to signal demodulation unit and handles; Signal demodulation unit is used for the signal that receives from coupling unit is carried out synchronously and demodulates the training sequence that carries; The channel frequency response estimation unit, the frequency response that utilizes that receive and known pilot frequency sequence to carry out channel is estimated, obtains the frequency response parameter; The linear electrical parameter computing unit through the variation of relevant information in analysis frequency response parameter and the analysis frequency response curve, obtains the variation of transmission line basic parameter is estimated; Transmission line status predication unit carries out Macro or mass analysis to the basic parameter variation of transmission line, draws prediction and monitoring to line status.

(3) beneficial effect

The present invention utilizes power line communication technology; Proposed a kind of electric line communication system transmission line status monitoring, the method and the device of maintenance, utilized power transmission line collection, transmission and analysis circuit ageing state, monitored the power line state information in real time based on the OFDM technology; Need not beyond the transmission line layout data harvester and communication system again; Reduce cost, effectively utilized abundant existing power line network resource, met the requirement of creating conservation-minded society.

Description of drawings

With reference to the accompanying drawings and combine instance to further describe the present invention.Wherein:

Fig. 1 is the monitoring method flow chart according to the embodiment of the invention.

Fig. 2 is based on system's transmission of the embodiment of the invention one and receives block diagram.

Fig. 3 is the frame structure according to the TDS-OFDM of the embodiment of the invention one.

Fig. 4 is the topology diagram according to the node of the embodiment of the invention.

Fig. 5 is the equivalent lumped parameter circuit diagram according to the transmission line of the embodiment of the invention.

Fig. 6 is according to the power line cross section of the embodiment of the invention and equivalent capacity sketch map.

Fig. 7 is the power line capacitive coupling sketch map according to the embodiment of the invention.

Fig. 8 is the variation diagram according to power line transmission channel magnitude response curve in the embodiment of the invention one.

Fig. 9 is the frame structure according to the CP-OFDM of the embodiment of the invention two.

Figure 10 is the variation diagram according to power line transmission channel magnitude response curve in the embodiment of the invention two.

Figure 11 is the frame structure according to the ZP-OFDM of the embodiment of the invention three.

Figure 12 is the variation diagram according to power line transmission channel magnitude response curve in the embodiment of the invention three.

Figure 13 is the variation diagram according to power line transmission channel magnitude response curve in the embodiment of the invention four.

Figure 14 is the variation diagram according to power line transmission channel phase response curve in the embodiment of the invention four.

Figure 15 is the power line transmission system carries out the monitoring method of system transmissions line states based on the OFDM technology the installation drawing that is used for according to the embodiment of the invention.

Embodiment

Below in conjunction with accompanying drawing and embodiment, specific embodiments of the invention describes in further detail.Following examples are used to explain the present invention, but are not used for limiting scope of the present invention.

Embodiment one

The scheme that embodiment one has provided the present invention's proposition is used for the power line transmission system carries out system communications line status monitoring and maintenance based on the TDS-OFDM technology a kind of embodiment.

This execution mode is to a kind of typical multicarrier mode of operation of PLC system, and concrete parameter is following: carrier mode Z=3780, and transmitting terminal planisphere mapping mode is 16QAM, frame head mode PN945, FEC code check are 0.4.

As shown in Figure 2, according to the method that the described systematic electricity line states of present embodiment was monitored and safeguarded to embodiment of the present invention, the topological structure of node is as shown in Figure 3, and its concrete steps are following:

S1, node A are with known training sequence and utilize the data framing to be sent of TDS-OFDM technology modulation, and through coupler signal are sent into power line transmission;

In the present embodiment, data to be sent at first through the FEC coding, are carried out the symbol X that the 16QAM constellation mapping obtains frequency domain then _k, per 3780 frequency domain symbol X _kConstituting an OFDM symbol, is that 3780 IDFT (IFFT) is with each frequency domain symbol X through length _kTransform on corresponding subcarrier of time domain; In time domain; Symbol lengths is that the front end that 420 PN sequence is placed in the OFDM symbol carries out framing as frame head; Frame structure is as shown in Figure 4 to be utilized the root-raised cosine pulse to carry out the time domain molding filtration bandwidth of signal is limited then, the signal of handling is carried out carrying out after up-conversion and the power amplification transmission of signal.

S2, Node B receive through coupler and send signal, utilize the known training sequence demodulated received signal, extract the transmission data;

In the present embodiment, Node B receives signal through coupler from power line, and the signal that receives is by down-conversion, through root-raised cosine pulse bandwidth filtering and sampling; Data after the sampling are corresponding carries out synchronously, channel estimating and FFT.

S3, Node B utilize known training sequence to obtain the transmission channel frequency response;

In the present embodiment, after carrying out signal Synchronization, just can carry out channel frequency response and estimate.Because one section known PN sequence (time-domain training sequence) with good autocorrelation is inserted in step S1 as frame head, we utilize the PN sequence as the channel monitoring signal.For each signal frame, the PN sequence that receives is carried out the relevant impulse response h (t) that just can obtain channel with local PN sequence.Again the impulse response sequence is carried out DFT, obtain the frequency response H (f) of channel.

Concrete principle is following:

Power line channel can come modeling with a multipath function, and impulse response is following:

$h\left(t\right)=\underset{i=1}{\overset{N}{\mathrm{\Σ}}}{g}_i\·\mathrm{\δ}(t-{\mathrm{\τ}}_i)---\left(1\right)$

Wherein, g _iBe the attenuation parameter in each footpath, its expression formula and connotation will make an explanation from transmission line theory hereinafter.

S (n) when supposing primary signal waiting for transmission, the noise of additivity is n (n), receives signals sampling so and can be expressed as:

$y\left(n\right)=s\left(n\right)\⊗h\left(n\right)+n\left(n\right)=\underset{i=1}{\overset{N}{\mathrm{\Σ}}}{g}_{i}s(n-{\mathrm{\τ}}_i)+n\left(n\right)---\left(2\right)$

Because the PN sequence has good autocorrelation, the impulse response of channel is estimated to be expressed as and is received the relevant of signal and known PN sequence:

h(n)=R _py(n) （3）

And then do Fourier transform, can obtain the frequency response function of channel.

S4, the response of Node B analysis frequency are extracted key message with the calculating channel parameter;

Concrete; Channel to power line carries out modeling, and the general multipath model of describing time domain specification that adopts is analyzed according to transmission line theory; The mesolow power line is during as data transmission channel; Can adopt traditional two wires uniform transmission line model (bilinear model) Approximate Equivalent, i.e. signal of communication transmission between two phases, but not single-phase-center line mode.

The lumped parameter power circuit of regarding distributed parameter line by many infinitely small length Δ x as is composed in series, and is as shown in Figure 5.

Wherein, and u (t, x), u (t, t+ Δ x) representes x and x+ Δ x place instantaneous voltage respectively; I (t, x), i (t, x+ Δ x) representes x and x+ Δ x place current instantaneous value respectively; R ₀, G ₀, L ₀, C ₀Resistance, leakage conductance, inductance, the line capacitance of difference representation unit length.

The transfer function that can be known power line channel multipath model by formula (1) is:

$H\left(f\right)=\underset{i=1}{\overset{N}{\mathrm{\&Sigma;}}}{g}_i\&CenterDot;e^{-\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="HDA00001980116300042.png,HDA00001980116300052.png"\; state="\{\{state\}\}">j</figure-callout>}2\mathrm{\&pi;}{\mathrm{f\&tau;}}_i}---\left(4\right)$

Attenuation parameter wherein

α (f) is the Line Attenuation constant, l _iBe the transmission signals path of passing through, a _iReflected network topology structure, be called weight coefficient, it is comprehensive at the catadioptric Overlay of each node in the path that it is that signal transmission is passed through, relevant with line parameter circuit value, number of nodes, branch road connected mode or the like.

Provide the computational methods of mesolow power line basic parameter below, the sectional view of power line such as Fig. 6.In the formula, c ₀Be the light velocity in the vacuum; μ ₀=4 π 10 ^-7H/m is a permeability of vacuum, ε ₀=10 ^-9/ 36 π F/m are permittivity of vacuum; σ _c, μ ₀Be respectively conductor conductivity and relative permeability; μ _r, ε _r, σ _rBe respectively relative permeability, relative dielectric constant and the conductivity of dielectric between conductor; Tan δ is the angle of loss of dielectric between conductor.

${\mathrm{<figure-callout\; id="0"\; label="R"\; filenames="HDA00001980116300042.png,HDA00001980116300051.png"\; state="\{\{state\}\}">R</figure-callout>}}_0=\sqrt{\frac{{\mathrm{\&mu;}}_0{\mathrm{\&mu;}}_{0}f}{\mathrm{\&pi;}{\mathrm{\&sigma;}}_c{r}^2}}\left[\frac{(D/2r)}{\sqrt{{(D/2r)}^2-1}}\right](\mathrm{\&Omega;}/m)---\left(5\right)$

${\mathrm{<figure-callout\; id="0"\; label="L"\; filenames="HDA00001980116300042.png,HDA00001980116300051.png"\; state="\{\{state\}\}">L</figure-callout>}}_0=\frac{{\mathrm{\&mu;}}_r{\mathrm{\&mu;}}_0}{\mathrm{\&pi;}}{\mathrm{Cosh}}^{-1}\left(\frac{\mathrm{<figure-callout\; id="2r"\; label="D"\; filenames="HDA00001980116300031.png"\; state="\{\{state\}\}">D</figure-callout>}}{2r}\right)+\frac{{\mathrm{<figure-callout\; id="0"\; label="R"\; filenames="HDA00001980116300042.png,HDA00001980116300051.png"\; state="\{\{state\}\}">R</figure-callout>}}_0}{2\mathrm{\&pi;f}}(H/m)---\left(6\right)$

${\mathrm{<figure-callout\; id="0"\; label="C"\; filenames="HDA00001980116300042.png,HDA00001980116300051.png"\; state="\{\{state\}\}">C</figure-callout>}}_0=\frac{{\mathrm{\&pi;\&epsiv;}}_r{\mathrm{\&epsiv;}}_0}{{\mathrm{Cosh}}^{-1}(D/2r)}(F/m)---\left(7\right)$

G ₀=2πfC ₀tanδ(S/m) （8）

$\mathrm{\&gamma;}=\mathrm{\&alpha;}+\mathrm{j\&beta;}=\sqrt{(R+\mathrm{j\&omega;L})(G+\mathrm{j\&omega;C})}---\left(9\right)$

Generally speaking, owing to have decay and coupling, need revise resistance per unit length, electric capacity and inductance:

The total resistance value of unit length is:

R _tot=X _R·R ₀ （10）

X wherein _RIt is correction factor.

The capacitive coupling sketch map is as shown in Figure 7, in order to simplify calculating, can use circuit shown in Figure 8 to calculate its equivalent capacitance value:

$C_{\mathrm{tot}}=\frac{{3\mathrm{<figure-callout\; id="2"\; label="C\; cab"\; filenames="HDA00001980116300042.png,HDA00001980116300052.png"\; state="\{\{state\}\}">C</figure-callout>}}_{\mathrm{cab}}}{2}+\frac{C_{\mathrm{con}}}{2}---\left(11\right)$

C _CabC above being exactly ₀, Be capacitance between unit length conductor and screen, ε _CcDielectric constant for dielectric between conductor and screen.

The equivalent leakage conductance of unit length is:

$G_{\mathrm{tot}}={\mathrm{<figure-callout\; id="0"\; label="G"\; filenames="HDA00001980116300042.png,HDA00001980116300051.png"\; state="\{\{state\}\}">G</figure-callout>}}_0\&CenterDot;\frac{C_{\mathrm{tot}}}{C_0}---\left(12\right)$

Can find through analyzing; When circuit receives external force, variations in temperature or because the aging variation that causes dielectric constant, magnetic permeability, decay factor and the electrical length of the insulator of transmission line of self; Thereby cause that corresponding change can take place the frequency response curve of circuit when distributed constant changed.

In the present embodiment, extracting key message is the DIELECTRIC CONSTANTS of insulator medium in the transmission line with the channel parameter that calculates _r

For the multipath effect of power transmission line, the mesohigh of employing, the classical mode of middle and long distance, parameter such as following table:

The multipath numbering	1	2	3	4	5	6
							Equivalent length/m	200	221	242	259	266	530
Weight coefficient	0.54	0.275	-0.15	0.08	-0.03	-0.02

Basic parameter that adopts in the emulation such as following table:

The basic parameter title	Symbol	Numerical value or interval
			The heart yearn radius	r	1.22mm
The heart yearn spacing	D	4.04mm
			The light velocity in the vacuum	c		3×10 8m/s
The relative dielectric constant of medium	ε r	[3.5,4]
			Dielectric constant in the vacuum	ε 0	8.85×10 -12F/m
The relative permeability of medium	μ r	[0.7,1.3]

Magnetic permeability in the vacuum	?μ 0	4π×10 -7H/m
			The conductivity of conductor	?σ	5.76×10 7S/m
The current displacement angle of medium	?tanδ	[10 -3,10 -2]

In this application implementation example, numerical value and the difference on the frequency between the minimum of maximum that we choose the amplitude-response curve of transmission channel is used for predicting the variation of the dielectric constant of transmission line insulator medium as key message.

The difference on the frequency that becomes between big and the minimum when the numerical value of the maximum of the amplitude-response curve of transmission channel becomes big, and we can analyze the DIELECTRIC CONSTANTS of insulator medium in the transmission line _rReduce, aging that the residing ambient temperature of transmission line raises or transmission line occurs just is described.

Shown identical transmission line amplitude-response curve from 1 ~ 100MHz under different condition like Fig. 9, can see that the difference on the frequency that the numerical value of solid line maximum on the amplitude-response curve of dotted line channel increases between (△ A), the minimum also becomes big (d2 > simultaneously; D1), thus we judge the DIELECTRIC CONSTANTS of insulator medium in the transmission line according to the variation of key message _rReduce, thereby estimate that the residing ambient temperature of transmission line raises or transmission line has taken place aging.

S5, Node B change according to channel parameter the power transmission line channel status are estimated and predict, it is sent to power line network as data to be transmitted through coupler, and pass to control station through other node forwarding or other modes.

Therefore when we through the amplitude-response curve of analyzing channel on size variation and the variation of the difference on the frequency between the minimum of maximum, just can analyze the variation of dielectric constant of the insulator medium of transmission line.And the reducing of dielectric constant often just reflected the rising of the aging or ambient temperature of transmission line, comparatively in time and accurately judges and monitors thereby just can have the state of transmission line.

Embodiment two

The scheme that embodiment two has provided the present invention's proposition is used for the power line transmission system carries out the monitoring and the maintenance of system transmissions line states based on the CP-OFDM technology a kind of embodiment.

This execution mode is to a kind of typical multicarrier mode of operation of PLC system, and concrete parameter is following: carrier mode Z=3780, and transmitting terminal planisphere mapping mode is 64QAM, the FEC code check is 0.4.

As shown in Figure 2, according to the method that the described systematic electricity line states of present embodiment was monitored and safeguarded to embodiment of the present invention, its concrete steps are following:

S1, node A are with known training sequence and utilize the data framing to be sent of OFDM technology modulation, and through coupler signal are sent into power line transmission;

In the present embodiment, data to be sent at first through the FEC coding, are carried out the symbol X that the 64QAM constellation mapping obtains frequency domain then _k, specific frequency-domain pilot sequence is inserted into original frequency domain symbol X _kIn as the means of channel estimating, the position of wherein inserting is through well-designed and fixing.

Wherein the inserted mode of frequency-domain pilot sequence is common has two kinds of piece (Block) pilot tone and dressing (Comb) pilot tones; Wherein the Block mode is periodically all subcarriers in the OFDM symbol to be used for transmitting pilot tone, and the Comb mode is to use a sub-set of sub-clutter to transmit pilot tone.

Per then 3780 new frequency domain symbols

Constituting an OFDM symbol, is that 3780 IDFT (IFFT) is with each frequency domain symbol X through length _kTransform on corresponding subcarrier of time domain, then frequency-domain pilot sequence just has been fixed on the specific subcarrier; In time domain; Back 420 symbol sebolic addressings of getting IDFT place the front end formation Cyclic Prefix (CP) of OFDM symbol to carry out framing as frame head; Utilize the root-raised cosine pulse to carry out the time domain molding filtration then the bandwidth of signal is limited, the signal of handling is carried out carrying out after up-conversion and the power amplification transmission of signal.

S2, Node B receive through coupler and send signal, and demodulated received signal extracts the transmission data;

S3, Node B utilize known training sequence to obtain transmission channel frequency response (or channel impulse response);

The ofdm system receiving terminal removes Cyclic Prefix through A/D and low pass filter, carries out DFT to received signal, if there is not ISI, then

Y(k)=X(k)H(k)+I(k)+W(k) （13）

This instance is intended to during the OFDM information symbol channel estimating of ofdm system discussed to the certainty Channel Modeling of quasistatic, so save the subscript index of OFDM information symbol sequence n in the following formula.In the formula, the reception signal value at Y (k) expression receiving terminal k number of sub-carrier place, the channel frequency characteristic value at H (k) expression k number of sub-carrier place, W (k) expression frequency domain Jiaxing white Gaussian noise, the ICI component that k carrier wave place of I (k) expression ofdm system participates in.After receiving terminal carried out the FFT processing to received signal, the pilot tone that system utilizes frequency domain to insert was carried out channel estimating.

LS criterion lower channel estimated result:

$H_{\mathrm{LS}}=X_p^{-1}{Y}_p---\left(14\right)$

Carry out interpolation according to the pilot sub-carrier estimated value then, just can obtain the channel estimation value that all subcarriers go out.Common interpolating method has two-dimentional MMSE interpolation, piecewise linear interpolation, piecewise polynomial fitting, based on the interpolation of DFT and low pass interpolation etc.

S4, the response of Node B analysis frequency are extracted key message with the calculating channel parameter;

In the present embodiment, extracting key message is the magnetic permeability μ of insulator medium in the transmission line with the channel parameter that calculates _r

Concrete theoretical derivation sees application implementation example one for details, and classical multipath model used herein is different with application implementation example one, parameter such as following table:

The multipath numbering	1	2	3	4	5
						Equivalent length/m	300	350	370	450	510
Weight coefficient	0.26	0.05	-0.03	0.25	-0.35

In this application implementation example, numerical value and the difference on the frequency between the minimum of maximum that we choose the amplitude-response curve of transmission channel is used for predicting the variation of the magnetic permeability of transmission line insulator medium as key message.

When the numerical value of the maximum of the amplitude-response curve of transmission channel diminish and minimum between difference on the frequency become big, we can analyze the magnetic permeability μ of insulator medium in the transmission line _rReduce, explain that just transmission line has received the interference of intense electromagnetic field or produced magnetic ageing.

Shown identical transmission line amplitude-response curve from 1 ~ 100MHz under different condition like Figure 11, can see that the solid line difference on the frequency that the numerical value of maximum reduces between (△ A), the minimum on the amplitude-response curve of dotted line channel but becomes (d2 > greatly; D1), thus we judge the magnetic permeability μ of insulator medium in the transmission line according to the variation of key message _rReduce, thereby estimate that transmission line environment of living in has the stronger interference of electromagnetic field or transmission line that magnetic ageing has taken place.

S5, Node B change according to channel parameter the power transmission line channel status are estimated and predict, it is sent to power line network as data to be transmitted through coupler, and pass to control station through other node forwarding or other modes.

Therefore when we through the amplitude-response curve of analyzing channel on numerical value change and the variation of the difference on the frequency between the minimum of maximum, just can analyze the variation of magnetic permeability of the insulator medium of transmission line.And the reducing of magnetic permeability often just reflected the aging of transmission line, comparatively in time and accurately judges and monitors thereby just can have the state of transmission line.

Embodiment three

The scheme that embodiment three has provided the present invention's proposition is used for the power line transmission system carries out the monitoring and the maintenance of system transmissions line states based on the ZP-OFDM technology a kind of embodiment.

This execution mode is to a kind of typical multicarrier mode of operation of PLC system, and concrete parameter is following: carrier mode Z=3780, and transmitting terminal planisphere mapping mode is 256QAM, the FEC code check is 0.6.

As shown in Figure 2, according to the method that the described systematic electricity line states of present embodiment was monitored and safeguarded to embodiment of the present invention, its concrete steps are following:

S1, node A are with known training sequence and utilize the data framing to be sent of OFDM technology modulation, and through coupler signal are sent into power line transmission;

In the present embodiment, data to be sent at first through the FEC coding, are carried out the symbol X that the 256QAM constellation mapping obtains frequency domain then _k, specific frequency-domain pilot sequence is inserted into original frequency domain symbol X _kIn as the means of channel estimating, the position of wherein inserting is through well-designed and fixing.

Likewise, the inserted mode of frequency-domain pilot sequence is common has two kinds of piece (Block) pilot tone and dressing (Comb) pilot tones.

Per then 3780 new frequency domain symbols Constituting an OFDM symbol, is that 3780 IDFT (IFFT) is with each frequency domain symbol X through length _kTransform on corresponding subcarrier of time domain, then frequency-domain pilot sequence just has been fixed on the specific subcarrier; In time domain; Place the front end of OFDM symbol to constitute prefix (ZP) 420 0 sequences and carry out framing as frame head; Utilize the root-raised cosine pulse to carry out the time domain molding filtration then the bandwidth of signal is limited, the signal of handling is carried out carrying out after up-conversion and the power amplification transmission of signal.

S2, Node B receive through coupler and send signal, and demodulated received signal extracts the transmission data;

S3, Node B utilize known training sequence to obtain transmission channel frequency response (or channel impulse response);

The ofdm system receiving terminal removes prefix through A/D and low pass filter, carries out DFT to received signal, if there is not ISI, then suc as formula (24).

After receiving terminal carried out the FFT processing to received signal, the pilot tone that system utilizes frequency domain to insert was carried out channel estimating.

Under the LMMSE criterion with H _pFor variable minimizes following formula:

min{(Y _p-X _pH _p) ^H(Y _p-X _pH _p)} （15）

Be multiple Gaussian distribution in CIR tap and additive noise, and under the two separate precondition, the channel estimation results of LMMSE criterion is:

${\hat{H}}_{\mathrm{LMMSE}}=R_{\mathrm{HH}}{(R_{\mathrm{HH}}+\frac{\mathrm{\&beta;}}{\mathrm{SNR}}I)}^{-1}{\hat{H}}_{\mathrm{LS}}---\left(16\right)$

Carry out interpolation according to the pilot sub-carrier estimated value then, just can obtain the channel estimation value that all subcarriers go out.Common interpolating method has two-dimentional MMSE interpolation, piecewise linear interpolation, piecewise polynomial fitting, based on the interpolation of DFT and low pass interpolation etc.

S4, the response of Node B analysis frequency are extracted key message with the calculating channel parameter;

In the present embodiment, extracting key message is the loss angle δ of insulator medium in the transmission line with the channel parameter that calculates;

Concrete theoretical derivation sees application implementation example one for details, and classical multipath model used herein is different with application implementation example one, parameter such as following table:

The multipath numbering	1	2	3	4
					Equivalent length/m	150	188	264	397
Weight coefficient	0.4	-0.4	-0.8	-1.5

In this application implementation example, the numerical value change of maximum that we choose the amplitude-response curve of transmission channel is used for predicting the variation of the loss angle δ of transmission line insulator medium as key message.

The difference on the frequency that becomes between big and the extreme value when the numerical value of the maximum of the amplitude-response curve of transmission channel is constant; The loss angle δ that we can analyze insulator medium in the transmission line increases, and explains that just transmission line has produced electric aging or because the loss that the external environment variation causes.

Shown identical transmission line amplitude-response curve from 1 ~ 100MHz under different condition like Figure 12; The numerical value that can see solid line maximum on the amplitude-response curve of dotted line channel increases difference on the frequency between (△ A), the minimum constant (d2>d1); Therefore we judge the loss angle δ increase of insulator medium in the transmission line according to the variation of key message, thereby estimate that transmission line has produced electric aging or because the loss that the external environment variation causes.

S5, Node B change according to channel parameter the power transmission line channel status are estimated and predict, it is sent to power line network as data to be transmitted through coupler, and pass to control station through other node forwarding or other modes.

Therefore the difference on the frequency between extreme value is constant simultaneously when the numerical value of the maximum of the amplitude-response curve of our transmission channel through analyzing channel increases; Just can analyze the increase of loss angle, judge comparatively accurately and monitor thereby just can have to the aging conditions of transmission line.

Embodiment four

The scheme that embodiment four has provided the present invention's proposition is used for the power line transmission system carries out the monitoring and the maintenance of system transmissions line states based on the TDS-OFDM technology a kind of embodiment.

This execution mode is to a kind of typical multicarrier mode of operation of PLC system, and concrete parameter is following: carrier mode Z=3780, and transmitting terminal planisphere mapping mode is 64APSK, the FEC code check is 0.4.

As shown in Figure 2, according to the method that the described systematic electricity line states of present embodiment was monitored and safeguarded to embodiment of the present invention, the topological structure of node is as shown in Figure 3, and its concrete steps are following:

S1, node A are with known training sequence and utilize the data framing to be sent of TDS-OFDM technology modulation, and through coupler signal are sent into power line transmission;

In the present embodiment, data to be sent at first through the FEC coding, are carried out the symbol X that the 16QAM constellation mapping obtains frequency domain then _k, per 3780 frequency domain symbol X _kConstituting an OFDM symbol, is that 3780 IDFT (IFFT) is with each frequency domain symbol X through length _kTransform on corresponding subcarrier of time domain; In time domain; Symbol lengths is that the front end that 420 PN sequence is placed in the OFDM symbol carries out framing as frame head; Frame structure is as shown in Figure 4 to be utilized the root-raised cosine pulse to carry out the time domain molding filtration bandwidth of signal is limited then, the signal of handling is carried out carrying out after up-conversion and the power amplification transmission of signal.

S2, Node B receive through coupler and send signal, utilize the known training sequence demodulated received signal, extract the transmission data;

In the present embodiment, Node B receives signal through coupler from power line, and the signal that receives is by down-conversion, through root-raised cosine pulse bandwidth filtering and sampling; Data after the sampling are corresponding carries out synchronously, channel estimating and FFT.

S3, Node B utilize known training sequence to obtain the transmission channel frequency response;

In the present embodiment, after carrying out signal Synchronization, just can carry out channel frequency response and estimate.Because one section known PN sequence (time-domain training sequence) with good autocorrelation is inserted in step S1 as frame head, we utilize the PN sequence as the channel monitoring signal.For each signal frame, the PN sequence that receives is carried out the relevant impulse response h (t) that just can obtain channel with local PN sequence.Again the impulse response sequence is carried out DFT, obtain the frequency response H (f) of channel.

S4, the response of Node B analysis frequency are extracted key message with the calculating channel parameter;

In the present embodiment, extracting key message is the DIELECTRIC CONSTANTS of insulator medium in the transmission line with the channel parameter that calculates _rWith magnetic permeability μ _r

Concrete theoretical derivation sees application implementation example one for details, and classics two footpath model parameters used herein see the following form:

The multipath numbering	1	2
			Equivalent length/m	20	25
Weight coefficient	0.5	0.3

In this application implementation example, the periodicity that the numerical value, the difference on the frequency between the minimum of maximum that we choose the amplitude-response curve of transmission channel cooperates phase response curve special frequency scope changes or because the variation of the aging line electricity length that causes when being used for predicting dielectric constant and the magnetic permeability of transmission line insulator medium as key message.

Difference on the frequency between the minimum of the amplitude-response curve of transmission channel becomes, and numerical value big, maximum is constant basically, and we can analyze the DIELECTRIC CONSTANTS of insulator medium in the transmission line _rReduce magnetic permeability μ simultaneously _rReduce, cooperate the bigger variation of the phase response number of cycles in the certain frequency scope, can the above-mentioned analysis of aided verification, explain that just transmission line has produced electric aging and magnetic ageing and the increase of the line electricity length that possibly cause thus.

Shown identical transmission line amplitude-response curve from 1 ~ 100MHz under different condition like Figure 13; Can see solid line on the amplitude-response curve of dotted line channel greatly, the difference on the frequency between constant basically, the minimum of the numerical value of minimum value has bigger increase; Shown the phase response curve under the corresponding conditions like Figure 14; Can see that phase cycling becomes big, so we judge the DIELECTRIC CONSTANTS of insulator medium in the transmission line according to the variation of key message _rReduce magnetic permeability μ simultaneously _rReduce, thereby estimate that transmission line has produced electric aging and magnetic ageing, and the increase of the line electricity length that causes thus.

Embodiment five

The power line transmission system that is used for that present embodiment provides the present invention's proposition carries out the monitoring of system transmissions line states and the device of maintaining method based on the OFDM technology.

With reference to accompanying drawing 15; Based on background technology and above-mentioned relevant description based on the technological power line transmission system of OFDM; The present invention proposes to be used for the power line transmission system and carries out the monitoring of system transmissions line states and the device of maintaining method based on the OFDM technology; Comprise: node A (containing data generation unit, signal modulating unit, coupling unit), Node B (containing coupling unit, signal demodulation unit, channel frequency response estimation unit, linear electrical parameter computing unit, transmission line status predication unit).

Each Elementary Function and signal annexation are described below:

1) data generation unit is used to produce the data bit of the required transmission of power line monitoring system.

2) signal modulating unit is used for the demand of the data based system that produces is carried out the modulation of OFDM, more known training pilot tone and OFDM symbol is made up, and framing outputs to coupling unit, is used for transmission.

3) coupler unit, the signal to be sent that is used for signal modulating unit output is coupled on the power line and transmits, or is used for signal demodulation unit and the signal on the power line is received handles;

4) signal demodulation unit is used for the signal that receives from coupling unit is carried out synchronously and demodulates the training sequence that carries;

5) channel frequency response estimation unit, the frequency response that utilizes known pilot sequence to carry out channel is estimated, obtains the frequency response parameter.

6) linear electrical parameter computing unit; Through the variation of key messages such as the changes in spacing between the minimizing amplitude of maximum value, change in location and extreme value, phase information in the analysis frequency response curve, obtain the transmission line basic parameter is comprised the relative dielectric constant ε of dielectric between conductor _r, relative permeability μ _r, the variation of angle of loss δ is estimated.。

7) transmission line status predication unit carries out Macro or mass analysis to the basic parameter variation of transmission line, draws prediction and monitoring to line status.

With reference to accompanying drawing 15, at start node A, the data generation unit at first produces data to be sent; Through the Channel Modulation unit data to be sent and training pilot tone are handled, produced ofdm signal and framing, send on the power transmission line through coupling unit; In Node B; Through coupling unit signal is received to the channel demodulation unit, after carrying out to the received signal synchronously and demodulating the training pilot tone of carrying, at the channel frequency response estimation unit; Utilize known training pilot tone that the frequency response of channel is estimated; The frequency response that the utilization of linear electrical parameter computing unit obtains estimates the variation of the basic parameter of transmission line is estimated that last transmission line status predication unit carries out Macro or mass analysis to the basic parameter variation of transmission line, draws prediction and monitoring to line status.

Can find out that node A and Node B are the differentiation on a kind of function, any node can have the function of these two nodes, in concrete application, can call status predication and signal transmission that units corresponding is used for transmission line as required.

Description of the invention provides for example with for the purpose of describing, and is not the disclosed form that exhaustively perhaps limit the invention to.Many modifications and variations are obvious for the ordinary skill in the art.Selecting and describing embodiment is for better explanation principle of the present invention and practical application, thereby and makes those of ordinary skill in the art can understand the various embodiment that have various modifications that the present invention's design is suitable for special-purpose.

Claims (10)

1. the method for a power transmission line status monitoring is characterized in that, may further comprise the steps:

S1, node A are with known training sequence and utilize the data framing to be sent of OFDM technology modulation, and through coupler signal are sent into power line and transmit;

S2, Node B receive through coupler and send signal, utilize the known training sequence demodulated received signal, extract the transmission data;

S3, Node B utilize known training sequence to obtain transmission channel frequency response or impulse response;

S4, Node B analyze channel frequency response, extract the relevant information of transmission line, draw the change information of transmission line basic parameter through the variation of analyzing relevant information, with the calculating channel parameter;

S5, Node B change based on channel parameter the power transmission line channel status are estimated and predicted.

2. the method for claim 1 is characterized in that:

Said training sequence comprises time-domain training sequence, frequency domain training sequence.

3. the method for claim 1 is characterized in that:

Said OFDM framing mode comprises ZP-OFDM, CP-OFDM and TDS-OFDM.

4. the method for claim 1 is characterized in that:

Among the step S4, said relevant information comprises that the frequency plot between poor, the adjacent extreme value of the frequency interval between the amplitude of the maximum of channel frequency response, minimizing amplitude, phase place, position, the adjacent extreme value is poor, the cycle of phase response.

5. the method for claim 1 is characterized in that:

Among the step S4, said transmission line basic parameter comprises the relative dielectric constant ε of dielectric between conductor _r, relative permeability μ _r, angle of loss, electrical length l.

6. the method for claim 1 is characterized in that:

Among the step S5; The said variation according to channel parameter estimated and predicts to comprise following corresponding relation to the power transmission line channel status: the aging or residing ambient temperature rising of transmission line of electricity that the relative dielectric constant of dielectric diminishes and representes transmission line between conductor; The diminish magnetic ageing of expression transmission line or because the variation of pressure causes medium that deformation heterogeneous has taken place, the increase of angle of loss representes that transmission line has produced electric aging or because the loss that the external environment variation causes of relative permeability.

7. method as claimed in claim 2 is characterized in that:

If adopt time-domain training sequence, then represent the impulse response estimation of channel with the convolution of training sequence and receiving sequence, pass through DFT (DFT) conversion then and obtain channel frequency response; If adopt frequency domain training sequence, then directly represent the frequency response estimation of channel with receiving sequence and the merchant of the DFT (DFT) that sends sequence.

8. the monitoring device of transmission line state in the power communication system is characterized in that this device comprises:

The data generation unit is used to produce data waiting for transmission;

The signal modulating unit is used for according to the demand of system the data that produce being carried out the OFDM modulation, and with known training pilot tone and OFDM symbol make up, framing, output to coupler unit;

Coupler unit is used for signal with signal modulating unit output and is coupled on the power line and transmits, or is used for that the coupling of the signal on the power line is received and be transferred to signal demodulation unit and handles;

Signal demodulation unit is used for the signal that receives from coupling unit is carried out synchronously and demodulates the training sequence that carries;

The channel frequency response estimation unit, the frequency response that utilizes that receive and known pilot frequency sequence to carry out channel is estimated, obtains the frequency response parameter;

The linear electrical parameter computing unit through the variation of relevant information in analysis frequency response parameter and the analysis frequency response curve, obtains the variation of transmission line basic parameter is estimated;

Transmission line status predication unit carries out Macro or mass analysis to the basic parameter variation of transmission line, draws prediction and monitoring to line status.

9. monitoring device as claimed in claim 8 is characterized in that:

Described in the linear electrical parameter computing unit in the frequency response curve relevant information comprise: the spacing between the maximum amplitude of frequency response curve, minimum amplitude, position, extreme value, phase place etc.

10. monitoring device as claimed in claim 8 is characterized in that:

The transmission line basic parameter comprises described in the linear electrical parameter computing unit: the relative dielectric constant ε of dielectric between conductor _r, relative permeability μ _r, angle of loss δ, electrical length l etc.

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