CN117129798B - Fault power module positioning method and system based on time domain reflection method - Google Patents
Fault power module positioning method and system based on time domain reflection method Download PDFInfo
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Abstract
The invention provides a fault power module positioning method and a system based on a time domain reflection method, wherein the method comprises the following steps: generating a detection signal through a signal generation module, and transmitting the detection signal to a communication line to be detected through a detection communication line; calculating based on the cable impedance to obtain an initial transmission signal generated when the detection signal passes through the line connection position for the first time; receiving an aliasing reflection fitting signal generated by the initial transmission signal passing through the fault power module through the signal receiving module; if the transmission time delay is smaller than the signal period, extracting a first reflection fitting signal from the aliased reflection fitting signal by combining the cable impedance and the initial transmission signal; performing cross-correlation operation based on the transmission time delay and combining the reflection fitting signal and the initial transmission signal to obtain a second correlation operation result; and calculating the signal transmission distance according to the second correlation operation result. The invention has the effect of improving the positioning accuracy of the fault power module.
Description
Technical Field
The invention belongs to the technical field of signal identification, and particularly relates to a fault power module positioning method and system based on a time domain reflection method.
Background
In a transmission line system such as a railway communication system, an aviation communication system, or the like, a plurality of power module devices such as IGBT modules are provided. When the power module device runs for a long time, a module fault possibly occurs, if the module fault is not found and maintained in time, the long transmission line system is caused to have faults such as communication interruption, signal distortion, circuit short circuit, circuit disconnection and the like, and then the whole system is caused to stop running and damage, so that huge economic loss is caused, and meanwhile, huge safety risks are accompanied. Therefore, faults of the power module devices need to be found and accurately positioned in time so that workers can repair the fault modules in time.
In the prior art, a time domain reflectometry is generally used for locating a fault power module in a long transmission line system, and the time domain reflectometry comprises a sequence time domain reflectometry (Sequence time domain reflectometry, STDR) based on transmission line theory and an extended frequency spectrum time domain reflectometry (Spread spectrum time domain reflectometry, SSTDR). The time domain reflection method does not influence the normal working signal of the system where the device to be tested is located, and is a non-invasive fault detection method.
The fault detection principle of the time domain reflection method is that when a power module breaks down, internal impedance changes, at the moment, a detection signal can be modulated by adopting the time domain reflection method in a pseudo-random sequence or through a binary phase shift keying method, and is injected into a transmission line where the power module is located, and as the internal impedance of the fault power module is different from the line impedance of the transmission line, reflection and transmission phenomena can occur when the detection signal reaches the fault power module, the transmission distance of the detection signal in the transmission line can be calculated by collecting the reflection signal of the detection signal at the fault power module, and the location of the fault power module can be deduced by the injection location of the detection signal.
However, in a practical application scenario, the long transmission line system is usually in a complex state of multi-branch topology, the phenomena of multi-point reflection and cyclic reciprocating reflection between points generally exist in the transmission path of the detection signal, and as the detection signal does not have a 'time allowance' caused by long transmission delay, the problem of identification blind areas caused by aliasing of the reflection signal generally exists, which leads to the problem of failure identification failure caused by submerged effective information of failure points or failure positioning error caused by offset of characteristic points. Although the range of the aliasing dead zone can be reduced to a certain extent by greatly prolonging the length of the transmission line or greatly improving the signal sampling rate of the signal generating module for generating the detection signal, the measures can increase the cost of the scheme and cause the problem of high-frequency attenuation of the detection signal, and are not suitable for practical application and popularization.
Disclosure of Invention
The invention provides a fault power module positioning method and system based on a time domain reflection method, which are used for solving the problem that a fault positioning error of a fault power module is large due to a recognition blind area generated by aliasing of reflected signals.
In a first aspect, the present invention provides a fault power module positioning method based on a time domain reflection method, the method comprising the steps of:
generating a detection signal through a signal generation module, transmitting the detection signal to a communication line to be detected through a detection communication line, wherein the line connection part of the detection communication line and the communication line to be detected is of a T-shaped topology with three-terminal symmetry, one end of the communication line to be detected, which is positioned at the line connection part, is connected with a fault power module, the other end of the communication line to be detected, which is positioned at the line connection part, is connected with a signal receiving module, the internal impedance of the signal generation module is matched with the cable impedance of the communication line to be detected, the internal impedance of the signal receiving module is matched with the cable impedance, and the internal impedance of the fault power module is not matched with the cable impedance;
calculating based on the cable impedance to obtain an initial transmission signal generated when the detection signal passes through the line connection position for the first time;
receiving an aliasing reflection fitting signal generated by the initial transmission signal passing through the fault power module through the signal receiving module, wherein the aliasing reflection fitting signal is generated by aliasing of a plurality of reflection fitting signals;
judging whether the transmission time delay of the detection signal between the signal receiving module and the fault power module is smaller than the signal period of the detection signal or not;
if the transmission time delay is greater than or equal to the signal period, performing cross-correlation operation based on the transmission time delay and combining the aliasing reflection fitting signal and the detection signal to obtain a first correlation operation result;
calculating to obtain a signal transmission distance between the signal generating module and the fault power module according to the first correlation operation result;
if the transmission delay is smaller than the signal period, the cable impedance and the initial transmission signal are combined to extract the first reflection fitting signal from the aliasing reflection fitting signal;
based on the transmission time delay, carrying out the cross-correlation operation by combining the reflection fitting signal and the initial transmission signal to obtain a second correlation operation result;
and calculating the signal transmission distance according to the second correlation operation result.
Optionally, a calculation formula of the first correlation operation result is as follows:
R 1 (t)＝∫ 0 T S i (t-t 0 )·S f (t-τ)dt
wherein: r is R 1 (T) represents the first correlation result, T represents the signal period, S i Representing the detection signal S f Representing the aliased fitted signal, S i (t-t 0 ) Indicating that an arbitrary time delay t has elapsed 0 Post detection signal S f (t- τ) represents the aliased reflection fit signal after the propagation delay τ.
Optionally, the calculating the signal transmission distance between the signal generating module and the fault power module according to the first correlation operation result includes the following steps:
calculating a target transmission delay when the first correlation operation result takes the maximum value based on a calculation formula of the first correlation operation result;
and calculating according to the target transmission time delay to obtain a signal transmission distance between the signal generating module and the fault power module, wherein the calculation formula of the signal transmission distance is as follows:
wherein: l represents the signal transmission distance, v represents the signal transmission speed, τ 0 Representing the target transmission timeAnd (5) extending.
Optionally, the calculating based on the cable impedance to obtain the initial transmission signal generated when the detection signal first passes through the line connection part includes the following steps:
calculating to obtain equivalent characteristic impedance according to the cable impedance, wherein the equivalent characteristic impedance is the line impedance of a front communication line after any signal passes through the line connection part from any port in the T-shaped topology;
calculating to obtain a transmission coefficient of any signal passing through the line connection part by combining the cable impedance and the equivalent characteristic impedance;
and calculating according to the transmission coefficient to obtain an initial transmission signal generated when the detection signal passes through the line connection position for the first time.
Optionally, said extracting the first of said reflection fit signals from said aliased reflection fit signal in combination with said cable impedance and said initial transmission signal comprises the steps of:
calculating to obtain equivalent characteristic impedance according to the cable impedance, wherein the equivalent characteristic impedance is the line impedance of a front communication line after any signal passes through the line connection part from any port in the T-shaped topology;
calculating to obtain a theoretical reflection fitting signal generated by the initial transmission signal passing through the fault power module by combining the cable impedance and the equivalent characteristic impedance;
extracting a first reflection fitting signal from the aliasing reflection fitting signal through the initial transmission signal and the theoretical reflection fitting signal, wherein the calculation formula of the first reflection fitting signal is as follows:
wherein: f (f) 0 (1) Representing the first of said reflection fit signals, S f Representing the aliased fitted signal, x 0 Representing the initial transmission signal ρ A Representing any signal passing through the lineTransmission coefficient at the connection point of the line, n represents the round trip transmission frequency of the initial transmission signal between the connection point of the line and the fault power module, m represents the upper limit of the round trip transmission frequency, f ref Representing the theoretical reflection fit signal, f ref (n) represents the theoretical reflection fit signal for the initial transmission signal at the nth round trip transmission between the line connection and the faulty power module.
Optionally, the calculation formula of the equivalent characteristic impedance is as follows:
wherein: z is Z T Representing the equivalent characteristic impedance, Z 0 Representing the cable impedance;
the transmission coefficient is calculated as follows:
wherein: ρ A Representing the transmission coefficient;
the calculation formula of the initial transmission signal is as follows:
x 0 ＝ρ A S i
wherein: x is x 0 Representing the initial transmission signal S i Representing the detection signal.
Optionally, the calculating, by combining the cable impedance and the equivalent characteristic impedance, a theoretical reflection fitting signal generated by the initial transmission signal passing through the fault power module includes the following steps:
and calculating a first reflection coefficient by combining the cable impedance and the equivalent characteristic impedance, wherein the first reflection coefficient is the reflection coefficient of any signal at the connection part of the line, and the calculation formula of the first reflection coefficient is as follows:
wherein: Γ -shaped structure A Representing the first reflection coefficient;
and calculating a second reflection coefficient by combining the cable impedance and the module internal impedance of the fault power module, wherein the second reflection coefficient is the reflection coefficient of any signal at the fault power module, and the calculation formula of the second reflection coefficient is as follows:
wherein: Γ -shaped structure B Representing the second reflection coefficient, Z D Representing the module internal impedance;
the first reflection coefficient, the second reflection coefficient and the transmission coefficient are combined to calculate a fault point reflection signal, a connection point transmission signal and a connection point reflection signal, wherein the fault point reflection signal is a reflection signal of the initial transmission signal reflected by the fault power module, the connection point transmission signal is a transmission signal of the fault point reflection signal transmitted by the line connection point, the connection point reflection signal is a reflection signal of the fault point reflection signal reflected by the line connection point, and the calculation formulas of the fault point reflection signal, the connection point transmission signal and the connection point reflection signal are as follows:
f B ＝Γ B x 0
i A ＝ρ A Γ B x 0
f A ＝Γ A Γ Bx0
wherein: f (f) B Representing the fault point reflection signal, i A Representing the transmission signal of the connection point, f A Representing the reflected signal at the connection point;
and carrying out signal superposition on the fault point reflection signal, the connection point transmission signal and the connection point reflection signal to obtain a theoretical reflection fitting signal.
Optionally, the calculation formula of the second correlation operation result is as follows:
wherein: r is R 2 (t) represents the result of the second correlation operation, f 0 Representing the reflection fit signal, S i (t-t 0 ) Indicating that an arbitrary time delay t has elapsed 0 Post detection signal f 0 (t- τ) represents the reflection fit signal after the transmission delay τ.
Optionally, the calculating the signal transmission distance according to the second correlation operation result includes the following steps:
calculating a target transmission delay when the second correlation operation result takes the maximum value based on a calculation formula of the second correlation operation result;
and calculating according to the target transmission time delay to obtain a signal transmission distance between the signal generating module and the fault power module, wherein the calculation formula of the signal transmission distance is as follows:
wherein: l represents the signal transmission distance, v represents the signal transmission speed, τ 0 Representing the target transmission delay.
In a second aspect, the present invention also provides a fault power module locating system based on time domain reflectometry, comprising a memory, a processor and a computer program stored on the memory and executable on the processor, the processor implementing the method as described in the first aspect when executing the computer program.
The beneficial effects of the invention are as follows:
the fault power module positioning method based on the time domain reflection method adopted by the invention comprises the following steps: generating a detection signal through a signal generation module, and transmitting the detection signal to a communication line to be detected through a detection communication line; calculating based on the cable impedance to obtain an initial transmission signal generated when the detection signal passes through the line connection position for the first time; receiving an aliasing reflection fitting signal generated by the initial transmission signal passing through the fault power module through the signal receiving module; judging whether the transmission time delay of the detection signal between the signal receiving module and the fault power module is smaller than the signal period of the detection signal; if the transmission delay is greater than or equal to the signal period, performing cross-correlation operation based on the transmission delay and combining the aliasing reflection fitting signal and the detection signal to obtain a first correlation operation result; calculating according to the first correlation operation result to obtain a signal transmission distance between the signal generating module and the fault power module; if the transmission time delay is smaller than the signal period, extracting a first reflection fitting signal from the aliased reflection fitting signal by combining the cable impedance and the initial transmission signal; performing cross-correlation operation based on the transmission time delay and combining the reflection fitting signal and the initial transmission signal to obtain a second correlation operation result; and calculating the signal transmission distance according to the second correlation operation result.
If the transmission delay is smaller than the signal period, an aliasing blind area exists in the received aliasing reflection fitting signal, and the first reflection fitting signal can be accurately separated from the aliasing reflection fitting signal through the steps, and the method is not influenced by the normal working state switching (on/off) of the fault power module, and can better reflect the impedance change characteristic and rule of the fault power module. Compared with the method that the aliasing fitting signals with aliasing dead zones are directly used for calculation, the method has the advantages that the separated reflection fitting signals are used for calculation, so that the signal transmission distance can be calculated more accurately, and the fault positioning accuracy of the fault power module is improved.
Drawings
Fig. 1 is a flow chart of a fault power module positioning method based on a time domain reflection method in the invention.
Fig. 2 is a system architecture diagram of a fault power module positioning method based on a time domain reflectometry in the present invention.
Fig. 3 is a schematic waveform diagram of aliasing of a detection signal and a multiple reflection signal under different transmission delay conditions in the present invention.
Fig. 4 is a waveform diagram of correlation waveform peaks under different transmission delays in the present invention.
Detailed Description
The invention discloses a fault power module positioning method based on a time domain reflection method.
Referring to fig. 1, the fault power module positioning method based on the time domain reflection method specifically includes the following steps:
s101, generating a detection signal through a signal generation module, and transmitting the detection signal to a communication line to be detected through a detection communication line.
The circuit connection part of the detection communication circuit and the communication circuit to be detected is in a T-shaped topology with three-terminal symmetry, one end of the communication circuit to be detected, which is positioned at the circuit connection part, is connected with a fault power module, the other end of the communication circuit to be detected, which is positioned at the circuit connection part, is connected with a signal receiving module, the internal impedance of the signal generating module is matched with the cable impedance of the communication circuit to be detected, the internal impedance of the signal receiving module is matched with the cable impedance, and the internal impedance of the fault power module is not matched with the cable impedance.
Referring to fig. 2, the internal impedance Z of the signal generating module out Impedance Z with cable 0 Is matched with the signal generating module to generate a detection signal S i And will detect the signal S i From point C to the communication line to be tested via the detection communication line, the signal generating module uses Pseudo-noise code (PN code) or binary phase shift keying (Binary phase shift keying, BPSK) modulated signal as detection signal S i The line connection part of the detection communication line and the communication line to be detected is the point A.
Two ends of the point A are respectively a point D and a point B, a signal receiving module is arranged at the point D, and the internal impedance Z of the signal receiving module input Impedance Z with cable 0 Matching. The point B is a fault power module, in fig. 2 the fault power module is an IGBT module, a trigger signal is generated for the fault power module by a driving module, and the internal impedance Z of the fault power module IGBT Impedance Z with cable 0 Mismatch ofMatch, thus detecting signal S i When the signal is transmitted from the point A to the point B, the signal is continuous and does not have abrupt change at the boundary as the impedance of the point B changes, so that the signal S is detected i Reflection and transmission phenomena must occur at the impedance mismatch point B, and a reflected signal S is generated f Simultaneously detecting signals S i Signal transmission also occurs past point a.
Let U be the voltage value of the signal, I be the current value of the signal, as can be seen from FIG. 2 and the above description:
U i +U f ＝U r
I i -I f ＝I r
U i /I i ＝U f /I f ＝Z 0
U r /I r ＝Z IGBT
wherein: the subscript i denotes the current voltage of the detection signal, the subscript f denotes the current voltage of the reflection signal, and the subscript r denotes the current voltage of the transmission signal.
The expressions of the reflection coefficient Γ and the transmission coefficient ρ can be further obtained according to the above expression, specifically as follows:
as can be seen from the above, when Z IGBT ＞＞Z 0 When Γ is approximately equal to 1, total reflection occurs in the signal (S i ＝S f ). When Z is IGBT ＝Z 0 When Γ=0, impedance matches, the signal is not reflected (S f =0). When Z is IGBT When=0, Γ= -1, total reflection of negative signal (S i ＝-S f )。
In the reflected signal detection scheme shown in fig. 2, the communication line is only used as a transmission channel between the signal generating/collecting module and the fault power module, so the following features exist:
(1) The signal transmission distance l and the signal round trip transmission delay tau of the communication line are both fixed values, and the following formulas are satisfied:
(2) In the signal bandwidth of the detection signal, the period of the pseudo-random code is usually far greater than τ, so that the problem of identification dead zone caused by aliasing of the reflected signal exists.
Referring to FIG. 3, the period is T BPSK7 Is a BPSK7 code (modulated by PN7 code generated by 3-level m-sequence) as a detection signal S i Injected into a uniform communication line (cable impedance Z 0 =50Ω, signal transmission speed v≡2×10 in line 8 m/s), reflected signal waveforms under different time delay conditions are obtained.
If open-circuit faults occur at 20m, 160m and 300m respectively, the first 3 reflection signals at the fault points are set to be f respectively τi (1)、f τi (2) And f τi (3) I=1, 2,3. The transmission delays of the reflected signals corresponding to the three fault points can be obtained according to the signal transmission distance calculation formula respectively as follows: τ 1 ＝200ns、τ 2 =1600 ns and τ 3 =3000 ns. As can be seen from fig. 3: τ 1 ＜T BPSK7 ＜τ 2 ＜τ 3 . Thus, when τ=τ 1 ＜T BPSK7 When the incident signal and the multi-reflection signal are aliased (S i +f τi (1)+f τi (2)+f τi (3))。
Referring to fig. 4, S acquired by the signal receiving module f And a detection signal S passing through the line propagation delay tau i Cross-correlation (Cross-correlation) operation is performed:
R(t)＝∫ 0 T S i (t-t 0 )·S f (t-τ)dt
wherein R (T) is the correlation result, T is the period of the incident signal, S f (t- τ) is the reflected signal acquired by the round trip delay τ, S i (t-t 0 ) Is passed through any one ofDelay t 0 When t is 0 When τ, R (t) takes the maximum value (correlation peak R pτ ). In the peak (R pτ ) A blind area is formed in the identification process, and identification errors are increased or even caused.
S102, calculating based on cable impedance to obtain an initial transmission signal generated when the detection signal passes through the line connection position for the first time.
The initial transmission signal can be calculated according to the transmission coefficient of the line connection.
S103, receiving an aliasing reflection fitting signal generated by the initial transmission signal passing through the fault power module through the signal receiving module.
The aliasing reflection fitting signals are signals generated by aliasing of a plurality of reflection fitting signals, the reflection fitting signals comprise fault point reflection signals, connection point transmission signals and connection point reflection signals, the fault point reflection signals are reflection signals of initial transmission signals reflected by the fault power module, the connection point transmission signals are transmission signals of the fault point reflection signals transmitted by the line connection points, and the connection point reflection signals are reflection signals of the fault point reflection signals reflected by the line connection points.
S104, judging whether the transmission time delay of the detection signal between the signal receiving module and the fault power module is smaller than the signal period of the detection signal, and if the transmission time delay is greater than or equal to the signal period, executing step S105; if the transmission delay is smaller than the signal period, step S107 is performed.
S105, performing cross-correlation operation based on transmission delay and combining the aliasing reflection fitting signal and the detection signal to obtain a first correlation operation result.
The calculation formula of the first correlation operation result is as follows:
R 1 (t)＝∫ 0 T S i (t-t 0 )·S f (t-τ)dt
wherein: r is R 1 (T) represents the first correlation result, T represents the signal period, S i Representing the detection signal S f Representing aliased reflection fit signal, S i (t-t 0 ) Indicating that an arbitrary time delay t has elapsed 0 Post detection signal S f (t- τ) represents the aliased reflection fit signal after a transmission delay τ.
S106, calculating to obtain the signal transmission distance between the signal generating module and the fault power module according to the first correlation operation result.
S107, extracting a first reflection fitting signal from the aliasing reflection fitting signal by combining the cable impedance and the initial transmission signal.
S108, performing cross-correlation operation on the transmission delay and combining the reflection fitting signal and the initial transmission signal to obtain a second correlation operation result.
S109, calculating the signal transmission distance according to the second correlation operation result.
The implementation principle of the embodiment is as follows:
if the transmission delay is smaller than the signal period, an aliasing blind area exists in the received aliasing reflection fitting signal, and the first reflection fitting signal can be accurately separated from the aliasing reflection fitting signal through the steps, and the method is not influenced by the normal working state switching (on/off) of the fault power module, and can better reflect the impedance change characteristic and rule of the fault power module. Compared with the method that the aliasing fitting signals with aliasing dead zones are directly used for calculation, the method has the advantages that the separated reflection fitting signals are used for calculation, so that the signal transmission distance can be calculated more accurately, and the fault positioning accuracy of the fault power module is improved.
In one embodiment, the step S106, namely, calculating the signal transmission distance between the signal generating module and the fault power module according to the first correlation operation result, specifically includes the following steps:
calculating a target transmission delay when the first correlation operation result takes the maximum value based on a calculation formula of the first correlation operation result;
and calculating according to the target transmission delay to obtain a signal transmission distance between the signal generating module and the fault power module, wherein the calculation formula of the signal transmission distance is as follows:
wherein: l represents the signal transmission distance, v represents the signal transmission speed, τ 0 Representing the target transmission delay.
In the present embodiment, R is calculated according to the calculation formula of the first correlation operation result in step S105 1 (t) target propagation delay τ at maximum 0 。
In one embodiment, the step S102, that is, the initial transmission signal generated when the detection signal first passes through the line connection based on the cable impedance calculation, specifically includes the following steps:
calculating according to the cable impedance to obtain equivalent characteristic impedance, wherein the equivalent characteristic impedance is the line impedance of a front communication line after any signal passes through a line connection part from any port in the T-shaped topology;
calculating to obtain a transmission coefficient of any signal passing through the line connection part by combining the cable impedance and the equivalent characteristic impedance;
and calculating according to the transmission coefficient to obtain an initial transmission signal generated when the detection signal passes through the line connection position for the first time.
In the present embodiment, the calculation formula of the equivalent characteristic impedance is as follows:
wherein: z is Z T Representing equivalent characteristic impedance, Z 0 Representing the cable impedance;
the transmission coefficient is calculated as follows:
wherein: ρ A Representing the transmission coefficient;
the calculation formula of the initial transmission signal is as follows:
x 0 ＝ρ A S i
wherein: x is x 0 Representing the initial transmission signal S i Representing the detection signal.
In one embodiment, the step S107 of extracting the first reflection fit signal from the aliased reflection fit signal by combining the cable impedance and the initial transmission signal specifically includes the steps of:
calculating according to the cable impedance to obtain equivalent characteristic impedance, wherein the equivalent characteristic impedance is the line impedance of a front communication line after any signal passes through a line connection part from any port in the T-shaped topology;
calculating by combining the cable impedance and the equivalent characteristic impedance to obtain a theoretical reflection fitting signal generated by the initial transmission signal passing through the fault power module;
extracting a first reflection fitting signal from the aliased reflection fitting signal through the initial transmission signal and the theoretical reflection fitting signal, wherein the calculation formula of the first reflection fitting signal is as follows:
wherein: f (f) 0 (1) Representing the first reflection fit signal, S f Representing aliased reflection fit signal, x 0 Representing the initial transmission signal ρ A Representing the transmission coefficient of any signal passing through the line connection, n represents the round trip transmission frequency between the line connection and the fault power module of the initial transmission signal, m represents the upper limit of the round trip transmission frequency, and f ref Represents the theoretical reflection fit signal, f ref (n) represents a theoretical reflection fit signal for the n-th round trip transmission between the line connection and the failed power module for the initial transmission signal.
In the present embodiment, the calculation formula of the equivalent characteristic impedance is as follows:
wherein: z is Z T Representation ofEquivalent characteristic impedance, Z 0 Representing the cable impedance;
the transmission coefficient is calculated as follows:
wherein: ρ A Representing the transmission coefficient;
the calculation formula of the initial transmission signal is as follows:
x 0 ＝ρ A S i
wherein: x is x 0 Representing the initial transmission signal S i Representing the detection signal.
In one embodiment, the theoretical reflection fitting signal generated by the initial transmission signal passing through the fault power module by combining the cable impedance and the equivalent characteristic impedance comprises the following steps:
the first reflection coefficient is calculated by combining the cable impedance and the equivalent characteristic impedance, and is the reflection coefficient of any signal at the connecting position of the line, and the calculation formula of the first reflection coefficient is as follows:
wherein: Γ -shaped structure A Representing a first reflection coefficient;
and calculating a second reflection coefficient by combining the cable impedance and the module internal impedance of the fault power module, wherein the second reflection coefficient is the reflection coefficient of any signal at the fault power module, and the calculation formula of the second reflection coefficient is as follows:
wherein: Γ -shaped structure B Representing a second reflection coefficient, Z D Representing the internal impedance of the module;
the first reflection coefficient, the second reflection coefficient and the transmission coefficient are combined to calculate a fault point reflection signal, a connection point transmission signal and a connection point reflection signal, wherein the fault point reflection signal is a reflection signal of an initial transmission signal reflected by the fault power module, the connection point transmission signal is a transmission signal of the fault point reflection signal transmitted by the line connection point, the connection point reflection signal is a reflection signal of the fault point reflection signal reflected by the line connection point, and the calculation formulas of the fault point reflection signal, the connection point transmission signal and the connection point reflection signal are as follows:
f B ＝Γ B x 0
i A ＝ρ A Γ B x 0
f A ＝Γ A Γ B x 0
wherein: f (f) B Representing a fault point reflected signal, i A Representing the transmission signal at the junction, f A Representing the connection point reflected signal;
and carrying out signal superposition on the fault point reflection signal, the connection point transmission signal and the connection point reflection signal to obtain a theoretical reflection fitting signal.
In this embodiment, the fault point reflection signal, the connection point transmission signal and the connection point reflection signal are transmitted back and forth between the line connection point and the fault power module, so that a back and forth transmission rule between the line connection point and the fault power module can be deduced through calculation formulas of the fault point reflection signal, the connection point transmission signal and the connection point reflection signal, and the specific formulas are as follows:
f B (n)＝Γ B f A (n-1)
i A (n)＝ρ A f B (n-1)
f A (n)＝Γ A f B (n-1)
where n is the number of round-trip transmissions of signals between the line connection and the faulty power module.
In this embodiment, the calculation formula for obtaining the second correlation calculation result based on the transmission delay and combining the reflection fitting signal and the initial transmission signal is as follows:
wherein: r is R 2 (t) represents the result of the second correlation operation, f 0 Representing the reflection fit signal S i (t-t 0 ) Indicating that an arbitrary time delay t has elapsed 0 Post detection signal f 0 (t- τ) represents the reflection fit signal after the transmission delay τ.
In one embodiment, the step S109, that is, calculating the signal transmission distance according to the second correlation operation result, specifically includes the following steps:
calculating a target transmission delay when the second correlation operation result takes the maximum value based on a calculation formula of the second correlation operation result;
and calculating according to the target transmission delay to obtain a signal transmission distance between the signal generating module and the fault power module, wherein the calculation formula of the signal transmission distance is as follows:
wherein: l represents the signal transmission distance, v represents the signal transmission speed, τ 0 Representing the target transmission delay.
In the present embodiment, the target transmission delay τ 0 Corresponding correlation peak valueThe expression of (2) is as follows:
the invention also discloses a fault power module positioning system based on the time domain reflection method, which comprises a memory, a processor and a computer program stored on the memory and capable of running on the processor, wherein the processor realizes the fault power module positioning method based on the time domain reflection method disclosed in any one of the embodiments when executing the computer program.
The implementation principle of the embodiment is as follows:
by calling the program, the following steps are executed: generating a detection signal through a signal generation module, and transmitting the detection signal to a communication line to be detected through a detection communication line; calculating based on the cable impedance to obtain an initial transmission signal generated when the detection signal passes through the line connection position for the first time; receiving an aliasing reflection fitting signal generated by the initial transmission signal passing through the fault power module through the signal receiving module; judging whether the transmission time delay of the detection signal between the signal receiving module and the fault power module is smaller than the signal period of the detection signal; if the transmission delay is greater than or equal to the signal period, performing cross-correlation operation based on the transmission delay and combining the aliasing reflection fitting signal and the detection signal to obtain a first correlation operation result; calculating according to the first correlation operation result to obtain a signal transmission distance between the signal generating module and the fault power module; if the transmission time delay is smaller than the signal period, extracting a first reflection fitting signal from the aliased reflection fitting signal by combining the cable impedance and the initial transmission signal; performing cross-correlation operation based on the transmission time delay and combining the reflection fitting signal and the initial transmission signal to obtain a second correlation operation result; and calculating the signal transmission distance according to the second correlation operation result.
If the transmission delay is smaller than the signal period, an aliasing blind area exists in the received aliasing reflection fitting signal, and the first reflection fitting signal can be accurately separated from the aliasing reflection fitting signal through the steps, and the method is not influenced by the normal working state switching (on/off) of the fault power module, and can better reflect the impedance change characteristic and rule of the fault power module. Compared with the method that the aliasing fitting signals with aliasing dead zones are directly used for calculation, the method has the advantages that the separated reflection fitting signals are used for calculation, so that the signal transmission distance can be calculated more accurately, and the fault positioning accuracy of the fault power module is improved.
Those of ordinary skill in the art will appreciate that: the discussion of any of the embodiments above is merely exemplary and is not intended to imply that the scope of the present application is limited to such examples; the technical features of the above embodiments or in the different embodiments may also be combined under the idea of the present application, the steps may be implemented in any order, and there are many other variations of the different aspects of one or more embodiments in the present application as above, which are not provided in details for the sake of brevity.
One or more embodiments herein are intended to embrace all such alternatives, modifications and variations that fall within the broad scope of the present application. Any omissions, modifications, equivalents, improvements, and the like, which are within the spirit and principles of the one or more embodiments in the present application, are therefore intended to be included within the scope of the present application.
Claims (10)
1. The fault power module positioning method based on the time domain reflection method is characterized by comprising the following steps of:
generating a detection signal through a signal generation module, transmitting the detection signal to a communication line to be detected through a detection communication line, wherein the line connection part of the detection communication line and the communication line to be detected is of a T-shaped topology with three-terminal symmetry, one end of the communication line to be detected, which is positioned at the line connection part, is connected with a fault power module, the other end of the communication line to be detected, which is positioned at the line connection part, is connected with a signal receiving module, the internal impedance of the signal generation module is matched with the cable impedance of the communication line to be detected, the internal impedance of the signal receiving module is matched with the cable impedance, and the internal impedance of the fault power module is not matched with the cable impedance;
calculating based on the cable impedance to obtain an initial transmission signal generated when the detection signal passes through the line connection position for the first time;
receiving an aliasing reflection fitting signal generated by the initial transmission signal passing through the fault power module through the signal receiving module, wherein the aliasing reflection fitting signal is generated by aliasing of a plurality of reflection fitting signals;
judging whether the transmission time delay of the detection signal between the signal receiving module and the fault power module is smaller than the signal period of the detection signal or not;
if the transmission time delay is greater than or equal to the signal period, performing cross-correlation operation based on the transmission time delay and combining the aliasing reflection fitting signal and the detection signal to obtain a first correlation operation result;
calculating to obtain a signal transmission distance between the signal generating module and the fault power module according to the first correlation operation result;
if the transmission delay is smaller than the signal period, the cable impedance and the initial transmission signal are combined to extract the first reflection fitting signal from the aliasing reflection fitting signal;
based on the transmission time delay, carrying out the cross-correlation operation by combining the reflection fitting signal and the initial transmission signal to obtain a second correlation operation result;
and calculating the signal transmission distance according to the second correlation operation result.
2. The fault power module positioning method based on the time domain reflectometry according to claim 1, wherein the calculation formula of the first correlation operation result is as follows:
wherein: r is R 1 (T) represents the first correlation result, T represents the signal period, S i Representing the detection signal S f Representing the aliased fitted signal, S i (t-t 0 ) Indicating that an arbitrary time delay t has elapsed 0 Post detection signal S f (t- τ) represents the aliased reflection fit signal after the propagation delay τ.
3. The fault power module positioning method based on the time domain reflectometry according to claim 2, wherein the calculating the signal transmission distance between the signal generating module and the fault power module according to the first correlation operation result includes the following steps:
calculating a target transmission delay when the first correlation operation result takes the maximum value based on a calculation formula of the first correlation operation result;
and calculating according to the target transmission time delay to obtain a signal transmission distance between the signal generating module and the fault power module, wherein the calculation formula of the signal transmission distance is as follows:
wherein: l represents the signal transmission distance, v represents the signal transmission speed, τ 0 Representing the target transmission delay.
4. The fault power module localization method based on time domain reflectometry according to claim 1, wherein the calculating based on the cable impedance results in an initial transmission signal generated when the detection signal first passes through the line connection comprises the steps of:
calculating to obtain equivalent characteristic impedance according to the cable impedance, wherein the equivalent characteristic impedance is the line impedance of a front communication line after any signal passes through the line connection part from any port in the T-shaped topology;
calculating to obtain a transmission coefficient of any signal passing through the line connection part by combining the cable impedance and the equivalent characteristic impedance;
and calculating according to the transmission coefficient to obtain an initial transmission signal generated when the detection signal passes through the line connection position for the first time.
5. The method of claim 1, wherein said combining said cable impedance and said initial transmission signal to extract a first of said reflection fit signals from said aliased reflection fit signal comprises the steps of:
calculating to obtain equivalent characteristic impedance according to the cable impedance, wherein the equivalent characteristic impedance is the line impedance of a front communication line after any signal passes through the line connection part from any port in the T-shaped topology;
calculating to obtain a theoretical reflection fitting signal generated by the initial transmission signal passing through the fault power module by combining the cable impedance and the equivalent characteristic impedance;
extracting a first reflection fitting signal from the aliasing reflection fitting signal through the initial transmission signal and the theoretical reflection fitting signal, wherein the calculation formula of the first reflection fitting signal is as follows:
wherein: f (f) 0 (1) Representing the first of said reflection fit signals, S f Representing the aliased fitted signal, x 0 Representing the initial transmission signal ρ A Representing the transmission coefficient of any signal passing through the line connection, n represents the round trip transmission frequency of the initial transmission signal between the line connection and the fault power module, m represents the upper limit of the round trip transmission frequency, f ref Representing the theoretical reflection fit signal, f ref (n) represents the theoretical reflection fit signal for the initial transmission signal at the nth round trip transmission between the line connection and the faulty power module.
6. The fault power module localization method based on time domain reflectometry according to claim 4 or 5, wherein the calculation formula of the equivalent characteristic impedance is as follows:
wherein: z is Z T Representing the equivalent characteristic impedance, Z 0 Representing the cable impedance;
the transmission coefficient is calculated as follows:
wherein: ρ A Representing the transmission coefficient;
the calculation formula of the initial transmission signal is as follows:
x 0 ＝ρ A S i
wherein: x is x 0 Representing the initial transmission signal S i Representing the detection signal.
7. The method for locating a fault power module based on time domain reflectometry according to claim 6, wherein said calculating a theoretical reflection fit signal generated by said initial transmission signal through said fault power module by combining said cable impedance and said equivalent characteristic impedance comprises the steps of:
and calculating a first reflection coefficient by combining the cable impedance and the equivalent characteristic impedance, wherein the first reflection coefficient is the reflection coefficient of any signal at the connection part of the line, and the calculation formula of the first reflection coefficient is as follows:
wherein: Γ -shaped structure A Representing the first reflection coefficient;
and calculating a second reflection coefficient by combining the cable impedance and the module internal impedance of the fault power module, wherein the second reflection coefficient is the reflection coefficient of any signal at the fault power module, and the calculation formula of the second reflection coefficient is as follows:
wherein: Γ -shaped structure B Representing the second reflection coefficient, Z D Representing the module internal impedance;
the first reflection coefficient, the second reflection coefficient and the transmission coefficient are combined to calculate a fault point reflection signal, a connection point transmission signal and a connection point reflection signal, wherein the fault point reflection signal is a reflection signal of the initial transmission signal reflected by the fault power module, the connection point transmission signal is a transmission signal of the fault point reflection signal transmitted by the line connection point, the connection point reflection signal is a reflection signal of the fault point reflection signal reflected by the line connection point, and the calculation formulas of the fault point reflection signal, the connection point transmission signal and the connection point reflection signal are as follows:
f B ＝Γ B x 0
i A ＝ρ A Γ B x 0
f A ＝Γ A Γ B x 0
wherein: f (f) B Representing the fault point reflection signal, i A Representing the transmission signal of the connection point, f A Representing the reflected signal at the connection point;
and carrying out signal superposition on the fault point reflection signal, the connection point transmission signal and the connection point reflection signal to obtain a theoretical reflection fitting signal.
8. The fault power module positioning method based on the time domain reflectometry of claim 7, wherein the calculation formula of the second correlation operation result is as follows:
wherein: r is R 2 (t) represents the second correlationCalculation result f 0 Representing the reflection fit signal, S i (t-t 0 ) Indicating that an arbitrary time delay t has elapsed 0 Post detection signal f 0 (t- τ) represents the reflection fit signal after the transmission delay τ.
9. The fault power module positioning method based on the time domain reflectometry according to claim 8, wherein the calculating the signal transmission distance according to the second correlation operation result includes the steps of:
calculating a target transmission delay when the second correlation operation result takes the maximum value based on a calculation formula of the second correlation operation result;
and calculating according to the target transmission time delay to obtain a signal transmission distance between the signal generating module and the fault power module, wherein the calculation formula of the signal transmission distance is as follows:
wherein: l represents the signal transmission distance, v represents the signal transmission speed, τ 0 Representing the target transmission delay.
10. A fault power module localization system based on time domain reflectometry comprising a memory, a processor and a computer program stored on the memory and executable on the processor, wherein the processor implements the method of any one of claims 1 to 9 when executing the computer program.
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| CN108333476A (en) * | 2018-02-09 | 2018-07-27 | 中国人民解放军海军航空大学 | A kind of cable fault TDR localization methods and system considering cable attenuation characteristic |
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| CN113138065A (en) * | 2021-04-14 | 2021-07-20 | 温州大学 | Device and method for analyzing few-mode fiber faults based on multi-mode transmission reflection |
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