A broadband impedance spectrum online test signal maximum power tracking injection method

Abstract

The present application belongs to the technical field of power system, especially relates to a kind of wideband impedance spectrum online test signal maximum power tracking injection method, the cable to be measured is connected with switch capacitor matrix, isolation capacitor and isolation inductor, the isolation inductor is connected with isolation capacitor, and the test circuit is formed, and wideband impedance spectrum is used to send test signal to test circuit;Maximum power tracking equation is used to calculate preliminary power, and the initial switch capacitor matrix value when the test signal power of the injected cable is maximum is found;The voltage and current of test signal are extracted, and the switch capacitor matrix value is adjusted;Real-time power is calculated, and the switch capacitor matrix value when the test signal power of the injected cable is maximum is found.The present application can realize cable monitoring based on wideband impedance spectrum, which can be detected online, unnecessary power-off detection, and isolation power frequency high voltage, protection wideband impedance instrument, while ensuring that frequency-variable test signal is efficiently injected into cable.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of power systems, and particularly relates to a wide-frequency impedance spectrum online test signal maximum power tracking injection method. BACKGROUND

[0002] With the rapid development of urbanization, cross-linked polyethylene power cables with excellent electrical insulation performance and mechanical properties are widely used in power system transmission and distribution networks. However, as the operation time increases, the power cables begin to show different degrees of insulation aging problems due to the influence of multiple stresses such as electricity, heat, and machinery, and the operation environment. Some cables reach or even exceed the original design service life, and their insulation problems begin to gradually appear. Therefore, in order to improve the power supply reliability of power cables and ensure the safety of the power grid, it is necessary to regularly detect the insulation state of power cables to assess the insulation state of power cables and realize the positioning of local defects of power cables.

[0003] Wide-frequency impedance spectrum is widely used in cable state monitoring. However, the existing cable monitoring method based on wide-frequency impedance spectrum is only an offline monitoring method, which cannot realize online monitoring of the cable state, and causes unnecessary power outage during testing. The root cause of the existing wide-frequency impedance meter not being able to realize online detection is that the power frequency high voltage will cause damage to it. The use of a high-voltage isolation circuit can effectively isolate the power frequency high voltage of the power grid and avoid damage to the wide-frequency impedance meter. However, the isolation circuit will introduce an additional frequency-dependent impedance, which will cause the test signal to be unable to be effectively injected into the cable, resulting in test failure.

[0004] To this end, a wide-frequency impedance spectrum online test signal maximum power tracking injection method is proposed. SUMMARY

[0005] In order to solve or improve the problem of protecting the wide-frequency impedance meter while isolating the power frequency high voltage and ensuring efficient injection of the frequency-dependent test signal into the cable, the application provides a wide-frequency impedance spectrum online test signal maximum power tracking injection method, and the specific technical solutions are as follows:

[0006] The application provides a wide-frequency impedance spectrum online test signal maximum power tracking injection method, which connects the measured cable with a switch capacitor matrix, an isolation capacitor and an isolation inductor, connects the isolation inductor with the isolation capacitor, and forms a test circuit. The test circuit is sent a test signal by using a wide-frequency impedance spectrum;

[0007] The maximum power tracking equation is used to calculate the initial power and find the initial switch capacitor matrix value when the test signal power injected into the cable is maximum;

[0008] The voltage and current of the test signal are extracted, and the switch capacitor matrix value is adjusted;

[0009] According to the maximum power tracking equation, the real-time power is calculated, and then the real-time power and the initial power are compared to find the switch capacitor matrix value when the power of the test signal injected into the cable is maximum.

[0010] Preferably, the maximum power tracking equation is as follows:

[0011]

[0012] where ω is the angular frequency of the test signal, Z L is the characteristic impedance of the cable, C T,apro is the approximate value of the optimal CT; C P is the capacitance value of the isolation capacitor, and L is the isolation inductance value.

[0013] Preferably, the calculation of the maximum value of the power of the test signal and the optimal value of the switch capacitor matrix includes the following steps:

[0014] S1, adjust the switch capacitor matrix to be equal to the calculated initial switch capacitor matrix value CT;

[0015] S2, inject the voltage and current of the test signal, calculate the power of the injected test signal, and set Flag to 1, where Flag is a single-bit flag used to record the state of the program in the computer program;

[0016] S3, judge the value of Flag, and select to increase or decrease the value of the switch capacitor matrix according to the judgment result;

[0017] S4, inject the voltage and current of the test signal again, and calculate the power of the injected test signal;

[0018] S5, compare the powers of the test signals injected twice, and adjust the value of Flag;

[0019] S6, according to the comparison result of S5, repeat the cycle of S3 to S5 until the optimal CT value of the switch capacitor matrix is obtained, at which time the power of the test signal is maximum.

[0020] Preferably, the extraction of the voltage and current of the test signal is performed by current and voltage sensors, respectively, and the current and voltage signals are adjusted and processed by a conditioning circuit, which is used to adjust and process the current signal, including amplification / reduction, bias, phase shift, and filtering. The processed current and voltage signals can be used to calculate the power of the test signal.

[0021] Preferably, after injecting the voltage and current of the test signal and calculating the power of the injected test signal, it is judged whether the value of Flag is equal to 1. If it is equal to 1, the value of the switch capacitor matrix is increased. If the value of Flag is not equal to 1, the value of the switch capacitor matrix is decreased.

[0022] Preferably, the program needs to preset the ΔP before running, the ΔP is the lowest threshold value of the power difference allowed by the two injection test signals, when running S5, it is needed to judge whether the two injection test signals are less than the ΔP, if less than the ΔP, the program ends, if not less than the ΔP, the program runs again from S3.

[0023] Preferably, the switched capacitor matrix includes N capacitor elements, denoted as C T1 to C Tn to C TN , and C Tn = 2 n-1 △C T .

[0024] The application also provides a computer readable storage medium, the computer readable storage medium includes a stored program, wherein, when the program runs, the device where the computer readable storage medium is located executes the broadband impedance spectrum online test signal maximum power tracking injection method described above.

[0025] The application also provides a processor for running a program, wherein, when the program runs, the broadband impedance spectrum online test signal maximum power tracking injection method described above is executed.

[0026] The beneficial effects of the application are: compared with the traditional scheme, the broadband impedance spectrum based cable monitoring method of the application adjusts the value of the switched capacitor matrix to obtain the maximum power of the online test signal, so that online detection is possible, and power-off detection is not necessary, and the high-voltage power frequency is isolated, the broadband impedance meter is protected, and the frequency-varying test signal is efficiently injected into the cable. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 is the circuit structure diagram of the application;

[0028] Figure 2 is the flowchart of the application. DETAILED DESCRIPTION

[0029] The technical solutions in the embodiments of the application will be clearly and completely described below with reference to the drawings in the embodiments of the application. Obviously, the described embodiments are some of the embodiments of the application, rather than all the embodiments of the application. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the application.

[0030] It should be understood that, when used in the specification, the terms "include" and "contain" indicate the existence of described features, whole, steps, operations, elements and / or components, but do not exclude the existence or addition of one or more other features, whole, steps, operations, elements, components and / or sets thereof.

[0031] It should also be understood that the terms used in the specification of the present application are used merely for the purpose of describing particular embodiments and are not intended to limit the present application. As used in the specification of the present application, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

[0032] It should be further understood that the term "and / or" used in the specification of the present application means any combination of one or more of the associated listed items and all possible combinations, and includes these combinations.

[0033] In order to solve the problem of isolating power frequency high voltage, protecting wide frequency impedance meter, and ensuring efficient injection of frequency-varying test signal into cable, a wide frequency impedance spectrum online test signal maximum power tracking injection method is proposed as shown in Figure 1 The measured cable is connected with a switch capacitor matrix, an isolation capacitor and an isolation inductor, the isolation inductor is connected with the isolation capacitor, and a test circuit is formed, and a wide frequency impedance spectrum is used to send a test signal to the test circuit.

[0034] The maximum power tracking equation is used to calculate the initial power, and the initial switch capacitor matrix value when the test signal power of the injected cable is maximum is found.

[0035] The voltage and current of the test signal are extracted, and the switch capacitor matrix value is adjusted.

[0036] According to the maximum power tracking equation, the real-time power is calculated, and the switch capacitor matrix value when the test signal power of the injected cable is maximum is found according to the comparison between the real-time power and the initial power.

[0037] As a specific embodiment of the present application, the maximum power tracking equation is as follows:

[0038] (1)

[0039] In the formula, ω is the angular frequency of the test signal, Z L is the characteristic impedance of the cable, C T,apro is the approximate value of the optimal C T , C P is the capacitance value of the isolation capacitor, is the isolation inductance value.

[0040] In order to avoid the system falling into a local optimal solution trap, the approximate value of C C T that can make the test signal power of the injected cable maximum is calculated according to formula (1) C T,apro .

[0041] As a specific embodiment of the present application, the calculation of the maximum value of the power of the test signal and the optimal value of the switch capacitor matrix comprises the following steps:

[0042] S1, adjust the switch capacitor matrix to be equal to the initial calculated switch capacitor matrix value CT;

[0043] S2, inject the voltage and current of the test signal, calculate the power of the injected test signal, and Flag is 1, Flag is a single-bit size flag in the computer program for recording the state of the program;

[0044] S3, judge the value of Flag, and select to increase or decrease the value of the switch capacitor matrix according to the judgment result;

[0045] S4, inject the voltage and current of the test signal again, and calculate the power of the injected test signal;

[0046] S5, compare the power of the test signal injected twice, and adjust the value of Flag;

[0047] S6, according to the comparison result of S5, repeat the cycle of S3 to S5 until the optimal CT value of the switch capacitor matrix is obtained, at this time the power of the test signal is the maximum value. The extraction of the voltage and current of the test signal is extracted by the current sensor and the voltage sensor respectively, and the current and voltage signals are adjusted and processed by the conditioning circuit, the conditioning circuit is used to adjust and process the current signal, including amplification / reduction, bias, phase shift, filtering, and the processed current and voltage signals can be used to calculate the power of the test signal. After injecting the voltage and current of the test signal and calculating the power of the injected test signal, it is judged whether the variable value is equal to 1, if it is equal to 1, the value of the switch capacitor matrix is increased, if it is not equal to 1, the value of the switch capacitor matrix is decreased. Before the program runs, ΔP needs to be preset, ΔP is the lowest threshold value of the allowed power difference of the test signal injected twice, when running S5, it is needed to judge whether the test signal injected twice is less than ΔP, if it is less than ΔP, the program ends, if it is not less than ΔP, the program is run again from S3.

[0048] As Figure 2 , CT: switch capacitor matrix;

[0049] CT1~CTn~CTN: capacitor elements in CT, a total of N, and CTn=2n-1△CT;

[0050] S1~Sn~SN: control switch of CT;

[0051] CP: isolation capacitor, used for isolating high voltage of power frequency and protecting wideband impedance instrument;

[0052] LT: isolation inductance, used for providing low resistance grounding channel for power frequency leakage voltage and current, and further protecting the wideband impedance instrument;

[0053] Current sensor: for collecting the injected signal current signal;

[0054] Voltage sensor: for collecting the injected signal voltage signal;

[0055] Current conditioning circuit: for adjusting processing the current signal, including amplification / reduction, bias, phase shift, filtering, etc.

[0056] Voltage conditioning circuit: for adjusting processing the voltage signal, including amplification / reduction, bias, phase shift, filtering, etc.

[0057] The application also provides a computer readable storage medium, the computer readable storage medium comprising a stored program, wherein the computer readable storage medium controls the device where the computer readable storage medium is located to execute the broadband impedance spectrum online test signal maximum power tracking injection method described above when the program is running.

[0058] The application also provides a processor for running a program, wherein the processor executes the broadband impedance spectrum online test signal maximum power tracking injection method described above when the program is running.

[0059] Those skilled in the art can appreciate that the units of the examples described in conjunction with the embodiments disclosed herein can be realized in electronic hardware, computer software or a combination of both. In order to clearly illustrate the interchangeability of hardware and software, the components of the examples have been described in general terms in the above description. Whether the functions are realized in hardware or software depends on the specific application and design constraints of the technical solution. The skilled person can use different methods to realize the described functions for each specific application, but such implementation should not be considered beyond the scope of the application.

[0060] In the embodiments provided in the present application, it should be understood that the division of units is only a logical functional division, and actual implementation can have another division manner, for example, multiple units can be combined into one unit, one unit can be split into multiple units, or some features can be ignored, etc.

[0061] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application, and they should be covered in the scope of the description of the present application.

Claims

1. A method for maximum power tracking injection of broadband impedance spectroscopy online test signals, characterized by: Connecting the cable under test to the switch capacitor matrix, the isolation capacitor and the isolation inductor, and connecting the isolation inductor to the isolation capacitor to form a test circuit, and using a broadband impedance spectrum to send a test signal to the test circuit; The initial power is calculated using the maximum power tracking equation to find the initial switch capacitor matrix value when the test signal power injected into the cable is maximum; the maximum power tracking equation is as follows: ； Where, is the test signal angular frequency, is the cable characteristic impedance, is the optimal switch capacitor matrix value Approximate value of is the capacitance value of the isolation capacitor, is the isolation inductance value; Extract the voltage and current of the test signal and adjust the switch capacitor matrix value; the voltage and current of the test signal are extracted using a current sensor and a voltage sensor respectively, and the current and voltage signals are adjusted and processed by a conditioning circuit. The conditioning circuit is used to adjust and process the current signal, including amplification / reduction, biasing, phase shifting, and filtering. The processed current and voltage signals are used to calculate the power of the test signal; Calculate the real-time power according to the maximum power tracking equation, and then compare the real-time power with the preliminary power to find the switch capacitor matrix value that maximizes the power of the test signal injected into the cable. The calculation of the maximum value of the power of the test signal and the optimal value of the switch capacitor matrix includes the following steps: S1, adjust the switch capacitance matrix and the calculated initial switch capacitance matrix value C T equal; S2, the voltage and current of the injected test signal, calculate the power of the injected test signal, Flag is 1, Flag is a single-bit mark used to record the program status in the computer program; S3, judging the value of Flag, and choosing to increase or decrease the value of the switch capacitor matrix according to the judgment result; S4, injecting the voltage and current of the test signal again, and calculating the power of the injected test signal; S5: Compare the power of the two injected test signals and adjust the Flag value; S6, according to the comparison result of S5, repeat the cycle from S3 to S5 until the optimal C of the switch capacitor matrix is ​​obtained. T value, at which point the power of the test signal is at its maximum value.

2. The method for injecting a maximum power tracking signal for online broadband impedance spectroscopy testing according to claim 1, characterized in that: The voltage and current of the test signal are injected, and after calculating the power of the injected test signal, it is determined whether the Flag value is equal to 1. If it is equal to 1, the value of the switch capacitor matrix is ​​increased. If the Flag value is not equal to 1, the value of the switch capacitor matrix is ​​decreased.

3. The method for injecting a maximum power tracking signal for online broadband impedance spectroscopy testing according to claim 1, characterized in that: Before running the program, ΔP needs to be preset. ΔP is the threshold that allows the minimum power difference between two injected test signals. When running S5, it is necessary to determine whether the two injected test signals are less than ΔP. If so, the program ends. If not, the program runs again from S3.

4. The method for injecting a maximum power tracking signal for online broadband impedance spectroscopy testing according to claim 1, characterized in that: The switch capacitor matrix includes N capacitor elements, denoted as C T1 to C Tn to C TN , and C Tn =2 n-1 △C T .

5. A computer-readable storage medium, characterized in that The computer-readable storage medium includes a stored program, wherein when the program is executed, the device where the computer-readable storage medium is located is controlled to execute the broadband impedance spectrum online test signal maximum power tracking injection method according to any one of claims 1 to 4.

6. A processor, characterized in that: The processor is configured to run a program, wherein the program, when running, executes the broadband impedance spectrum online test signal maximum power tracking and injection method according to any one of claims 1 to 4.

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