CN113438253B - Adaptive firewall system for power line carrier communication - Google Patents
Adaptive firewall system for power line carrier communication Download PDFInfo
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Abstract
A self-adaptive firewall system for power line carrier communication belongs to the technical field of power line carrier communication. The invention solves the problems of poor confidentiality, no protective measures in the signal demodulation process and easy eavesdropping existing in the existing power line carrier communication, and comprises a branch adjusting structure, a fuzzy controller and an intelligent controller; the branch adjusting structure comprises a plurality of branch wires, one ends of the branch wires are respectively connected with the power cable through relays, the other ends of the branch wires are suspended, and the branch wires are arranged close to a signal receiving end of the power cable; the fuzzy controller acquires a current channel communication frequency band and a fixed point elimination frequency band through a receiving end modem to acquire a self-adaptive regulation rate; the intelligent controller adaptively adjusts a branch control switch function for controlling the branch adjusting structure, and controls the switching-off or switching-on of the relay in the branch adjusting structure. The invention is suitable for power carrier communication anti-eavesdropping.
Description
Technical Field
The invention belongs to the technical field of power line carrier communication.
Background
Nowadays, power line carrier communication has become the most widely applied communication means of power systems, and provides powerful support for various service technologies such as automatic meter reading, intelligent interaction, automatic query and the like. The power line carrier communication technology uses a power line as a medium for information transmission, and achieves the purpose of signal transmission through a modulation and demodulation technology. The method has the advantages of simple and convenient networking, low cost, wide application range and extremely high application value. However, the power line carrier communication has many disadvantages:
noise components in the power line carrier communication process are complex, and noise is generated when various electric equipment in a power network is disconnected or connected, various long-short wave signal crosstalk and the like, so that the power line communication quality is seriously affected.
Secondly, the physical layer of the low-voltage power line carrier communication is the existing 220V power line and is generally fixed, so that the flexibility of a safety mechanism at the bottom layer of the power line is reduced, and confidential communication is not facilitated.
And thirdly, in practical application, a high-level protocol of power line carrier communication is not set to be too complicated. Eavesdropping of the currently transmitted data on the power network is therefore easily achieved.
And fourthly, during signal demodulation, if energy storage elements such as capacitors or inductors are adopted, the problems such as resonance and the like are easily caused, and only signals with specific frequencies can be screened fixedly, so that the self-adaption of signal conditioning cannot be realized.
Disclosure of Invention
The invention aims to solve the problems that the existing power line carrier communication has poor confidentiality, no protective measures are taken in the signal demodulation process, and the existing power line carrier communication is easy to eavesdrop.
The invention relates to a self-adaptive firewall system for power line carrier communication, which comprises a branch adjusting structure, a fuzzy controller and an intelligent controller;
the branch adjusting structure comprises a plurality of branch wires, one ends of the branch wires are respectively connected with the power cable through relays, the other ends of the branch wires are suspended, and the branch wires are arranged close to a signal receiving end of the power cable;
the fuzzy controller obtains the communication frequency band f of the current channel through the receiving end modemsSum fixed point cancellation band fmCalculating the reward deviation and the change rate of the channel, establishing a discourse domain according to the reward deviation and the change rate of the channel, and obtaining a self-adaptive adjustment rate;
the intelligent controller utilizes the adaptive adjustment rate and the current channel communication frequency band fsSum fixed point cancellation band fmThe branch control switch function Q used for controlling the branch adjusting structure is adjusted in a self-adaptive mode, the relay of the branch adjusting structure is controlled to be switched on or off, stuffing waves are added to the power line channel, signal self-adaptive adjustment of power line carrier communication is achieved, and protection of the power line channel is completed.
Further, in the present invention, the fuzzy controller is also used to calculate | H (f)s)-H(fm) I is used as the reward deviation and is established according to the reward deviation and the change rate thereofAnd the domain of discourse obtains the fuzzy language of the reward deviation and the change rate thereof through membership function operation, searches the fuzzy language of the self-adaptive adjustment rate control quantity corresponding to the reward deviation and the change rate thereof in the condition statement of the fuzzy control rule, and finally clarifies the control quantity fuzzy language to obtain the self-adaptive adjustment rate.
Further, in the present invention, the process of adaptively adjusting the signal of the power line carrier communication is as follows:
step one, initializing a branch control switch function Q ═ Q1,q2,…qn]；
Step two, obtaining the communication frequency band f of the current channelsSum fixed point cancellation band fm；
Step three, controlling a switching function Q to be [ Q ] according to the current branch1,q2,…qn]Obtaining a path network topological graph of the signal close to a receiving end;
step four, obtaining the total number of paths of multipath tracks of the signals transmitted in the power line by utilizing a path network topological graph of the signals close to the receiving end and combining the reflection and refraction of the signals at the branch points of the power line;
step five, calculating the amplitude-frequency characteristic of the fixed point eliminating frequency band and the amplitude-frequency characteristic of the current communication frequency band according to the total number of paths of the multipath track, and further obtaining the reward deviation of the current channel;
step six, judging whether the reward deviation of the current channel reaches the maximum value, if so, finishing the signal self-adaptive adjustment of the power line carrier communication, otherwise, adjusting the branch control switch function Q to [ Q ]1,q2,…qn]And controlling a switching function Q ═ Q according to the branch1,q2,…qn]And adjusting the number of branch conductors connected into the power cable, and returning to the step II, wherein n is the maximum branch number.
Further, in the present invention, in the first step, the branch control switching function Q is [ Q ═ Q1,q2,…qn]In (1),
further, in the present invention, when Q is [0,0, …,0], it indicates that no branch conductor of the current power line channel is connected, and when Q is [1,1, …,1], it indicates that all branches of the branch regulation structure are connected on the current power line channel.
Further, in the present invention, in step two, the weighting factor | g of each path of the channeli|≤1。
Further, in step four, the specific obtaining method for obtaining the multipath trajectory of the signal propagating in the power line in the present invention is as follows:
let the number of branch conductor connection points be npoint：
npoint＝∑Q
N ispointEach branch conductor connecting point divides the main path into npoint+1 segment, the propagation direction of the signal is defined as one-dimensional vector x ═ x0,x1,…,xmax]Wherein x isiIs one value of { -1,1}, i is 0 to max, and max is 3 × npoint-1，xiWhen the value is-1, the signal is back to the sending end by one step, xiWhen the signal is 1, the signal is shown to advance to a receiving end by one step;
obtaining a value matrix X of all X according to the number of the branch lead connection points;
obtaining a signal reflection propagation diagram and a signal refraction propagation diagram according to the matrix X;
and obtaining the total number of paths of the multipath track of the signal transmitted in the power line by using the signal reflection propagation diagram and the signal refraction propagation diagram.
Further, in the present invention, in step five, the specific method for calculating the amplitude-frequency characteristic of the fixed-point cancellation frequency band and the amplitude-frequency characteristic of the current communication frequency band according to the total number of paths of the multipath trajectory includes:
by the formula:
calculating to obtain amplitude-frequency characteristic H (f) of fixed-point elimination frequency bands) And amplitude-frequency characteristic H (f) of current communication frequency bandm)，
Wherein f is the communication frequency band f of the current channelsOr fixed point cancellation band fm；giIs the weighting coefficient of the ith branch, τiIs the time delay of branch i, N is the total number of paths of the multipath trajectory, diIs the length of the path, vpThe propagation speed of a signal in a power line, k is an attenuation exponent, a0、a1The attenuation coefficients of signals in the power cable are normal numbers.
Further, in the present invention, the delay τ of branch iiThe acquisition method comprises the following steps:
by the formula:
calculating the delay of the signal in each branch of the branch regulation structureτiWherein: diIs the path length, εrIs the dielectric constant of the electric field lines, c0Is the speed of light, vpIs the speed at which a signal travels through a power line.
Further, in the present invention, in the fifth step, a specific method for obtaining the reward bias of the current channel is as follows:
amplitude-frequency characteristic H (f) of the previous communication bandm) And amplitude-frequency characteristic H (f) of fixed-point cancellation bands) Is used as the reward bias | H (f) of the current channels)-H(fm)|。
The firewall device and the method artificially set and eliminate frequency points in the self-adaptive signal firewall device based on the power line carrier communication, inhibit noise of a specific frequency band, improve communication quality, fully utilize physical characteristics of a power line, realize communication with higher confidentiality through frequency selection characteristics, effectively improve the safety of signal transmission, realize safe connection without additional communication protocols, reduce the cost of power line network resources, and are beneficial to use and popularization in a low-voltage power line carrier system.
Drawings
Fig. 1 is a schematic diagram of an adaptive firewall system based on power line carrier communication according to the present invention;
FIG. 2 is a flow diagram of the firewall device system adaptive control;
fig. 3 is a schematic diagram of a path that may be formed by signal reflection when the switching function is Q ═ 1,1,1, 1;
FIG. 4 is npointWhen the signal is 4, the corresponding signal refracts a propagation diagram;
fig. 5 shows the amplitude-frequency response of a signal passing through the firewall device when the switching function Q is [1,1,1,1 ].
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
It should be noted that the embodiments and features of the embodiments may be combined with each other without conflict.
The first embodiment is as follows: the following describes the present embodiment with reference to fig. 1 and fig. 2, and the adaptive firewall system based on power line carrier communication according to the present embodiment includes a branch adjusting structure 1, a fuzzy controller 4, and an intelligent controller 3;
the branch adjusting structure 1 comprises a plurality of branch wires, one ends of the branch wires are respectively connected with the power cable 2 through relays, the other ends of the branch wires are suspended, and the branch wires are arranged close to a signal receiving end of the power cable 2;
the fuzzy controller 4 obtains the communication frequency band f of the current channel through the receiving end modem 3sSum fixed point cancellation band fmCalculating letterEstablishing a discourse domain according to the reward deviation and the change rate thereof to obtain a self-adaptive adjustment rate;
the intelligent controller 3 utilizes the adaptive adjustment rate and the current channel communication band fsSum fixed point cancellation band fmThe branch control switch function Q used for controlling the branch adjusting structure 1 is adjusted in a self-adaptive mode, the relay in the branch adjusting structure 1 is controlled to be switched on or off, stuffing waves are added to a power line channel, signal self-adaptive adjustment of power line carrier communication is achieved, and protection of the power line channel is completed.
Further, in the present embodiment, the fuzzy controller 4 is also used for calculating | H (f)s)-H(fm) And l, taking the number | as the reward deviation, establishing a domain according to the reward deviation and the change rate of the reward deviation, obtaining a fuzzy language of the reward deviation and the change rate of the reward deviation through membership function operation, searching a fuzzy language of the self-adaptive adjustment rate control quantity corresponding to the reward deviation and the change rate in a condition statement of a fuzzy control rule, and finally, carrying out clarification on the control quantity fuzzy language to obtain the self-adaptive adjustment rate.
In the invention, the branch adjusting structure 1 is installed in front of a communication receiving end, the core of the branch adjusting structure is the frequency selectivity of a power line channel, when a signal is transmitted on a power line, if the signal passes through a node with mismatched impedance, the signal can be reflected, theoretically, due to the multipath reflection, infinite transmission paths exist in the power line channel, and therefore, a trapped wave frequency point appears in the channel frequency response of the power line at a specific frequency. The invention utilizes the thought of graph theory to simulate the real propagation path of the signal by automatically increasing and decreasing the number of branches of the power line network and modeling the power line network, thereby obtaining the amplitude-frequency characteristic of the signal. Based on the method, reward and punishment information is introduced, so that the network topology is adaptively changed, the carrier frequency amplitude is optimal, the effect of worst noise and eavesdropping waveforms is achieved, and a power line firewall is formed.
In a second embodiment, the present embodiment is described with reference to fig. 2, and the present embodiment further defines the adaptive firewall system for power line carrier communication described in the first embodiment, and the process of adaptively adjusting the signal of power line carrier communication includes:
step one, initializing a branch control switch function Q ═ Q1,q2,…qn]；
Step two, obtaining the communication frequency band f of the current channelsSum fixed point cancellation band fm；
Step three, controlling a switching function Q to be [ Q ] according to the current branch1,q2,…qn]Obtaining a path network topological graph of the signal close to a receiving end;
step four, obtaining the total number of paths of multipath tracks of the signals transmitted in the power line by utilizing a path network topological graph of the signals close to the receiving end and combining the reflection and refraction of the signals at the branch points of the power line;
step five, calculating the amplitude-frequency characteristic of the fixed point eliminating frequency band and the amplitude-frequency characteristic of the current communication frequency band according to the total number of paths of the multipath track, and further obtaining the reward deviation of the current channel;
step six, judging whether the reward deviation of the current channel reaches the maximum value, if so, finishing the signal self-adaptive adjustment of the power line carrier communication, otherwise, adjusting the branch control switch function Q to [ Q ]1,q2,…qn]And controlling a switching function Q ═ Q according to the branch1,q2,…qn]And adjusting the number of branch conductors connected into the power cable 2, and returning to the step II, wherein n is the maximum branch number.
The invention utilizes the attenuation characteristic of the power line channel to attenuate certain specific frequency noise, and can ensure the communication quality. The frequency selection device is arranged at a power line receiving end, changes the topology of a physical layer of the power line, better utilizes the frequency selection characteristic of a power line channel, has the advantages of high confidentiality and good reliability, and can meet the high confidentiality requirements in the fields of military industry, aerospace and the like. The communication high-level protocol is not required to be changed, and the burden of a communication network can be reduced on the basis of safe communication. And (3) introducing reward and punishment information to enable the network topology to change in a self-adaptive manner, so that frequency selection is realized, and a more intelligent communication network is constructed.
In the present invention, the switching function Q is controlled according to the current branch as Q1,q2,…qn]Obtaining a path network topological graph of the signal close to a receiving end, and obtaining a plurality of propagation paths of the signal in the power line by the path network topological graph in consideration of reflection and refraction phenomena of the signal at a branch point of the power line;
the plurality of propagation paths include:
(1) due to reflection, the signal may propagate back to the transmitting end at the branch point, the signal may propagate back at any branch point (except the first and last), and only the case that the signal propagates back is considered (because the signal is attenuated too much after multiple propagation and is negligible).
Let the number of branch points be npoint：
npoint＝∑Q
N ispointEach branch point divides the main path into npoint+1 segment, the propagation direction of the signal is defined as one-dimensional vector x ═ x0,x1，…,xmax]Wherein x isiExpressed as the value in { -1,1}, max ═ 3 × n point1, indicating a step forward to the sender (back) and receiver (forward), respectively. All possible values of X are listed by matlab programming and connected into matrix X. E.g. npointWhen being 4, X is:
the corresponding signal reflection propagation diagram is shown in fig. 3.
(2) Due to refraction, the signal may propagate to the current branch at the branch point, considering the case where the signal propagates to any branch only once (because the signal attenuation is too large and negligible after multiple refractions). E.g. npointWhen the signal is 4, the corresponding signal refraction propagation diagram is shown in fig. 4.
Further, in the present embodiment, in the first step, the branch control switching function Q is [ Q ═ Q1,q2,…qn]In (1),
n is the maximum number of branches.
Further, in this embodiment, when Q is [0,0, …,0], it indicates that the current power line channel has no branch conductor access, and when Q is [1,1, …,1], it indicates that all branches of the branch regulation structure 1 are accessed on the current power line channel.
At present, in the channel modeling based on the graph theory, most of the channels are obtained by finding out several main paths by using a method for solving the previous K shortest paths, and then summing the main paths to approximate a real channel transmission function. The invention provides a modeling algorithm which is more practical in practice by comprehensively considering two conditions of echo formation due to reflection and bounce formation due to refraction of signals at branch points. For example, when Q is [1,1,1,1], the reflection of the signal in the firewall device is as shown in fig. 3.
Considering the problem of the bouncing of the signal at the branch point under different echo conditions, namely considering the branch point at which the signal bounces, the signal refraction occurrence probability is related to the inherent parameters of the cable adopted in the firewall device, so that the process can be simplified into a simple random process of weight change. By such a modeling algorithm, the amplitude-frequency characteristics of the signal in the device can be obtained, as shown in fig. 5. As can be seen from fig. 3 to 5, the amplitude-frequency characteristics of the signal show a certain notch, and the present apparatus utilizes the notch to implement the function of protecting the power line channel. First, let the current communication band be fsThe fixed point cancellation band is fmThe object of the present apparatus is to make H (f)s) Maximum and H (f)m) And minimum.
Further, in the present invention, in step two, the weighting factor | g of each path of the channeli|≤1。
In the present invention, since the signal propagation in the power line occurs not only on the direct path between transmission and reception but also reflection and refraction at the branch point must be considered, there is a multipath characteristic. Firstly, modeling is carried out on a single path, and a weight factor g of each path is definediIs the product of all reflection coefficients and transmission coefficients on the path, due to all reflection coefficients and transmission coefficients on the power lineThe conductivity is substantially less than or equal to 1. Thus, the weighting factor giIs also 1 or less, and g is more complicated as the path is longeriThe smaller.
Further, in the fourth embodiment, a specific method for obtaining a multipath trajectory of a signal propagating through a power line in step four is as follows:
let the number of branch conductor connection points be npoint：
npoint＝∑Q
N ispointEach branch conductor connecting point divides the main path into npoint+1 segment, the propagation direction of the signal is defined as one-dimensional vector x ═ x0,x1,…,xmax]Wherein x isiIs one value of { -1,1}, i is 0 to max, and max is 3 × npoint-1，xiWhen the value is-1, the signal is back to the sending end by one step, xiWhen the signal is 1, the signal is shown to advance to a receiving end by one step;
obtaining a value matrix X of all X through matlab according to the number of the branch lead connection points;
obtaining a signal reflection propagation diagram and a signal refraction propagation diagram according to the matrix X;
and obtaining the total number of paths of the multipath track of the signal transmitted in the power line by using the signal reflection propagation diagram and the signal refraction propagation diagram.
Further, in the present embodiment, in step five, a specific method for calculating the amplitude-frequency characteristic of the fixed-point cancellation frequency band and the amplitude-frequency characteristic of the current communication frequency band according to the total number of paths of the multipath trajectory includes:
by the formula:
calculating to obtain amplitude-frequency characteristic H (f) of fixed-point elimination frequency bands) And amplitude-frequency characteristic H (f) of current communication frequency bandm)，
Wherein f is the communication frequency band f of the current channelsOr fixed point cancellation band fm；giAs an addition to the ith branchWeight coefficient, τiIs the time delay of branch i, N is the total number of paths of the multipath trajectory, diIs the length of the path, vpThe propagation speed of the signal in the power line, k is the attenuation exponent, a0 and a1 are the attenuation coefficients of the signal in the power cable 2, which are normal numbers, and j is an imaginary number unit.
The attenuation coefficient of the signal in the cable adopts the formula:
α(f)＝a0+a1·fk
and calculating implementation, wherein k is an attenuation exponent, a0 and a1 are attenuation coefficients of signals in the power cable 2 and are normal numbers, and f is the transmission frequency of the current power cable 2 channel.
In this embodiment, the propagation of the signal along the path is described by the delay part and the low-pass characteristic is described by the attenuation part, i.e. the attenuation increases with length and frequency. Weight factor giThe reflection coefficient and transmission coefficient along the propagation path are summarized. The reflection points are typically complex and frequency dependent in that they may exhibit complex and frequency dependent values.
Further, in the present embodiment, the time delay τ of the branch iiThe acquisition method comprises the following steps:
by the formula:
calculating the delay tau of the signal in each branch of the branch regulation architecture 1iWherein: diIs the path length, εrIs the dielectric constant of the electric field lines, c0Is the speed of light, vpIs the speed at which a signal travels through a power line.
Further, in this embodiment, in the fifth step, a specific method for obtaining the reward bias of the current channel is as follows:
amplitude-frequency characteristic H (f) of the previous communication bandm) And amplitude-frequency characteristic H (f) of fixed-point cancellation bands) Is used as the reward bias | H (f) of the current channels)-H(fm)|。
The inventionIn (2), different switching functions Q may cause changes in channel topology, for example, when Q is [0,0, …,0 ═ b]When the current power line channel is connected without branch conductor, and when Q is [1,1, …,1 ═ 1]Time, indicates that all branch conductors are currently connected to the main power line channel. In the calculation, different Q will cause di、N、f、τiThe parameters change, so that H (f) also changes.
So in principle Q changes → H (f)s)H(fm) Change, | H (f)s)-H(fm) Naturally, | also varies as a reward bias.
The specific algorithm is as follows: firstly, initializing a switch function, setting the initial switch function to be Q0, setting a fixed iteration number n, and inputting a communication frequency band f of a current channelsSum fixed point cancellation band fmThe amplitude-frequency characteristic H (f) is calculated by using the initial switching function Q0s) And H (f)m) The reward bias is recorded, the switching function is changed from Q0 to Q1 according to an adaptive algorithm, and the amplitude-frequency characteristic H (f) is calculated agains) And H (f)m) The reward bias is then recorded and the switching function is changed from Q1 to Q2 according to an adaptive algorithm, … is updated repeatedly until the number of iterations n is reached. Then comparing the recorded reward deviation in each step, finding out the maximum reward deviation and outputting the corresponding switch function.
In the invention, the change process of the switching function in the self-adaptive algorithm is as follows: if the total number of branches is small, the traversal can be directly performed. If the total branch number is larger, a transfer learning algorithm is used, and the condition similar to the current Q result is found in historical data to change.
The adaptive firewall system of the power line carrier communication can be realized by the following method.
When the device is powered on, the current communication frequency band f is obtained from the receiving end modem 3sInitializing the branch control switching function Q ═ Q1,q2,…qn]Initializing fixed point cancellation band fmInvoking a graph theory based channel modeling algorithm to calculate H (f), and converting | H (f)s)-H(fm) L is transmitted to the fuzzy controller 4 as reward and punishment information, and the learning rate of the algorithm is adaptively adjusted (self-adaption)Rate to be adjusted), the smart controller 3 changes the switching function Q ═ Q according to the adjusted learning rate1,q2,…qn]. When transmission of carrier information transmitted in a power line network changes, the current Q ═ Q1,q2,…qn]May not be the optimal topology, | H (f)s)-H(fm) The I is larger, the penalty coefficient in the reward and punishment information is larger than the reward coefficient, the output learning rate of the fuzzy controller 4 is increased, and Q is changed along with the increase of the penalty coefficient until the I is H (f)s)-H(fm) I is decreased, the winning incentive coefficient of the reward and punishment information is greater than the reward coefficient, the output learning rate of the fuzzy controller 4 is reduced, the Q variation is reduced, and at the moment, the fixed-point elimination frequency fmStrongly attenuated, and the communication band f is controlledsAnd maintaining a relatively low attenuation range to achieve the optimal control target.
The invention firstly initializes the branch control switch function, sets the initial value as Q0, sets a fixed iteration number n, inputs the communication frequency band f of the current channelsSum fixed point cancellation band fmH is calculated with initialized Q0, the reward bias is recorded, the branch control switching function is changed from Q0 to Q1 according to the adaptive algorithm, H is calculated again, then the reward bias is recorded, and the branch control switching function is changed from Q1 to Q2 according to the adaptive algorithm, … is repeated until the iteration number n is reached. Then comparing the recorded reward deviation of each step, finding out the maximum and outputting the corresponding Q.
In the invention, the change process of the branch control switch function Q in the self-adaptive algorithm is as follows: if the total number of branches is small, the traversal can be directly performed. If the total branch number is larger, a transfer learning algorithm is used, and the condition similar to the current branch control switch function result is found in historical data to change.
Although the invention herein has been described with reference to particular embodiments, it is to be understood that these embodiments are merely illustrative of the principles and applications of the present invention. It is therefore to be understood that numerous modifications may be made to the illustrative embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims. It should be understood that features described in different dependent claims and herein may be combined in ways different from those described in the original claims. It is also to be understood that features described in connection with individual embodiments may be used in other described embodiments.
Claims (8)
1. The adaptive firewall system for the power line carrier communication is characterized by comprising a branch adjusting structure (1), a fuzzy controller (4) and an intelligent controller (3);
the branch adjusting structure (1) comprises a plurality of branch conducting wires, one ends of the branch conducting wires are respectively connected with the power cable (2) through relays, the other ends of the branch conducting wires are suspended, and the branch conducting wires are arranged close to a signal receiving end of the power cable (2);
the fuzzy controller (4) acquires the communication frequency band f of the current channel through the receiving end modem (3)sSum fixed point cancellation band fmCalculating the reward deviation and the change rate of the channel, establishing a discourse domain according to the reward deviation and the change rate of the channel, and obtaining a self-adaptive adjustment rate;
the intelligent controller (3) utilizes the adaptive adjustment rate and the current channel communication frequency band fsSum fixed point cancellation band fmThe branch control switch function Q used for controlling the branch adjusting structure (1) is adjusted in a self-adaptive mode, the relay in the branch adjusting structure (1) is controlled to be switched on or off, stuffing waves are added to a power line channel, the signal self-adaptive adjustment of power line carrier communication is achieved, and the protection of the power line channel is completed;
the fuzzy controller (4) is also used for calculating | H (f)s)-H(fm) I, as the reward deviation, establishing a domain of discourse according to the reward deviation and the change rate thereof, obtaining a fuzzy language of the reward deviation and the change rate thereof through membership function operation, searching a fuzzy language of a self-adaptive adjustment rate control quantity corresponding to the reward deviation and the change rate thereof in a condition statement of a fuzzy control rule, and finally, carrying out clarification on the control quantity fuzzy language to obtain the self-adaptive adjustment rate;
the process of the signal self-adaptive adjustment of the power line carrier communication comprises the following steps:
step one, initializationBranch control switching function Q ═ Q1,q2,…qn]；
Step two, obtaining the communication frequency band f of the current channelsSum fixed point cancellation band fm；
Step three, controlling a switching function Q to be [ Q ] according to the current branch1,q2,…qn]Obtaining a path network topological graph of the signal close to a receiving end;
step four, obtaining the total number of paths of multipath tracks of the signals transmitted in the power line by utilizing a path network topological graph of the signals close to the receiving end and combining the reflection and refraction of the signals at the branch points of the power line;
step five, calculating the amplitude-frequency characteristic of the fixed point eliminating frequency band and the amplitude-frequency characteristic of the current communication frequency band according to the total number of paths of the multipath track, and further obtaining the reward deviation of the current channel;
step six, judging whether the reward deviation of the current channel reaches the maximum value, if so, finishing the signal self-adaptive adjustment of the power line carrier communication, otherwise, adjusting the branch control switch function Q to [ Q ]1,q2,…qn]And controlling a switching function Q ═ Q according to the branch1,q2,…qn]And adjusting the number of branch conductors connected into the power cable (2), and returning to the step II, wherein n is the maximum branch number.
2. The adaptive firewall system for power line carrier communication according to claim 1, wherein in step one, the branch control switch function Q ═ Q1,q2,…qn]In (1),
3. the adaptive firewall system for power line carrier communication of claim 1, wherein when Q is [0,0, …,0], it indicates that no branch wire is connected to the current power line channel, and when Q is [1,1, …,1], it indicates that all branches of the branch regulation structure (1) are connected to the current power line channel.
4. The adaptive firewall system for power line carrier communication according to claim 1 or 2, wherein in step two, the weighting factor | g of each path of the channeli|≤1。
5. The adaptive firewall system for power line carrier communication of claim 4, wherein in step four, the specific obtaining method for obtaining the multipath trajectory of the signal propagating in the power line comprises:
let the number of branch conductor connection points be npoint：
npoint＝∑Q
N ispointEach branch conductor connecting point divides the main path into npoint+1 segment, the propagation direction of the signal is defined as one-dimensional vector x ═ x0,x1,...,xmax]Wherein x isiIs one value of { -1,1}, i is 0 to max, and max is 3 × npoint-1，xiWhen the value is-1, the signal is back to the sending end by one step, xiWhen the signal is 1, the signal is shown to advance to a receiving end by one step;
obtaining a value matrix X of all X according to the number of the branch lead connection points;
obtaining a signal reflection propagation diagram and a signal refraction propagation diagram according to the matrix X;
and obtaining the total number of paths of the multipath track of the signal transmitted in the power line by using the signal reflection propagation diagram and the signal refraction propagation diagram.
6. The adaptive firewall system for power line carrier communication according to claim 1, wherein in step five, the specific method for calculating the amplitude-frequency characteristic of the fixed-point cancellation frequency band and the amplitude-frequency characteristic of the current communication frequency band according to the total number of paths of the multipath trajectory comprises:
by the formula:
calculating to obtain amplitude-frequency characteristic H (f) of fixed-point elimination frequency bands) And amplitude-frequency characteristic H (f) of current communication frequency bandm)，
Wherein f is the communication frequency band f of the current channelsOr fixed point cancellation band fm；giIs the weighting coefficient of the ith branch, τiIs the time delay of branch i, N is the total number of paths of the multipath trajectory, diIs the length of the path, vpThe propagation speed of a signal in a power line, k is an attenuation exponent, a0、a1The attenuation coefficients of signals in the power cable (2) are normal numbers.
7. The adaptive firewall system for power line carrier communication of claim 6, wherein the delay τ of branch iiThe acquisition method comprises the following steps:
by the formula:
calculating the delay tau of the signal in each branch of the branch regulation structure (1)iWherein: diIs the path length, εrIs the dielectric constant of the electric field lines, c0Is the speed of light, vpIs the speed at which a signal travels through a power line.
8. The adaptive firewall system for power line carrier communication according to claim 6, wherein in step five, the specific method for obtaining the reward bias of the current channel comprises:
amplitude-frequency characteristic H (f) of the previous communication bandm) And amplitude-frequency characteristic H (f) of fixed-point cancellation bands) Is used as the reward bias | H (f) of the current channels)-H(fm)|。
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