A kind of method of testing of low-voltage power line narrowband carrier termination and proving installation
Technical field
The invention belongs to field of power, be specifically related to a kind of method of testing and proving installation of low-voltage power line narrowband carrier termination.
Background technology
Power line carrier communication refers to a kind of communication mode utilizing the signals such as power line transmission data, speech.Utilize existing line of electric force resource to communicate, can communication requirement be met, can difficult wiring be solved again, and infrastructure investment and daily servicing low cost, therefore power-line carrier communication has very high economy, convenience and practicality.But the original intention of power circuit design is the transmission in order to complete electrical power distribution and non-data, and thus for data communication, its characteristic of channel is very undesirable.The principal element affecting line of electric force reliable communication is exactly the termination characteristic of power circuit.The termination of power line carrier communication channel refers to the equiva lent impedance at sender unit and signal receiving device drive point place low-voltage power line.The impedance operator of power line carrier communication passage along with the on-position of time, frequency and signal change and change, especially 30-500kHz narrowband carrier frequency range, change is violent, affect obviously by electric network composition, circuit, consumer electronics etc., it is an instability parameter, it directly has influence on the transmission performance of carrier signal coupling efficiency and signal, is an important parameter of power line communication channel.Therefore research and Practical on-site test power line carrier termination have great importance to raising and improvement power-line carrier communication system performance.On the other hand, relative to the light current communications cable, power circuit belongs to Asymmetric Links and High Voltage electric network, the impedance of actual test power circuit has certain difficulty, and the method for testing of domestic and international existing termination mainly contains double-current probe method, ratioing technigue, resonance method, voltammetry is several.Ratioing technigue can only measure the modulus value of impedance, can not obtain the phase information of impedance; Resonance method can only measure the value of the impedance of single frequency point, can not obtain the impedance operator of continuous frequency spectrum; The circuit structure of voltammetry is complicated, and the testing tool of needs is more, and it is large that actual field measures difficulty, and required expensive equipment, is suitable for laboratory measurement; Although double-current probe method can measure modulus value and the phase information of low-voltage power line impedence, because the frequency resolution of network analyzer used is low, measured result accuracy is not very high, and on-the-spot test is also inconvenient.
Summary of the invention
For the deficiencies in the prior art, the invention provides a kind of method of testing and proving installation of low-voltage power line narrowband carrier termination, the modulus value of power line narrow band carrier termination can either be tested out, the phase information of impedance can be obtained again, measurement result is relatively more accurate simultaneously, and the method that easily can be applied to again the Impedance measurement of in-site measurement further develops research for power line communication and has great importance.
The method of testing of a kind of low-voltage power line narrowband carrier termination provided by the invention, its improvements are, described method of testing comprises the steps:
(1) proving installation is set on line of electric force;
(2) described proving installation and wire are calibrated;
(3) described proving installation sends a signal on line of electric force;
(4) described proving installation receives the data of the termination of returning that to be coupled from line of electric force, becomes the frequency curve of termination, and show according to described data fitting.
Wherein, described in step (2), wire refers to the wire be connected between proving installation and line of electric force;
Calibrate described proving installation and wire, its step comprises;
1. described proving installation is connected to the two ends on line of electric force or wire two terminal shortcircuit, obtains impedance Z
_{1}the voltage U at two ends
_{m1}, impedance Z
_{2}the voltage U at two ends
_{n1}, can impedance Z be obtained by Ohm law
_{2}with the impedance Z be made up of electric capacity and fixed value resistance
_{1}expression formula:
$\frac{{U}_{m1}}{{U}_{n1}}{Z}_{2}={Z}_{1};$
2. a fixed resistance Z is accessed at the two ends be connected on line of electric force at described proving installation
_{d}, obtain impedance Z
_{1}the voltage U at two ends
_{m2}and impedance Z
_{2}the voltage U at two ends
_{n2}, and obtain:
$\frac{{U}_{m2}}{{U}_{n2}}{Z}_{2}={Z}_{1}+{Z}_{D};$
3. 1. 2. obtained with step by step:
${Z}_{2}=\frac{{Z}_{D}}{(\frac{{U}_{m2}}{{U}_{n2}}-\frac{{U}_{m1}}{{U}_{n1}})};$
${Z}_{1}=\frac{{U}_{m1}}{{U}_{n1}}{Z}_{2};$
4. according to the impedance Z that 3. step obtains
_{1}and Z
_{2}value, determine the value of the resistance of the sender unit of described proving installation and the parameter of capacitance component.
Wherein, step (3) described proving installation sends a signal to the step on line of electric force and is;
1) sender unit of proving installation produces signal to power amplifier;
2) described power amplifier passes to described coupling mechanism after being amplified by signal;
3) described coupling mechanism couples a signal on line of electric force.
Wherein, step (4) comprises the steps:
A, described signal pickup assembly gather the data on line of electric force by spacer assembly, and data are passed to signal processing apparatus;
B, described signal processing apparatus draw the real part of termination, imaginary part and frequency according to described data, fit to the frequency curve of termination, and show.
The present invention is based on the proving installation of a kind of low-voltage power line narrowband carrier termination that another object provides, its improvements are, described proving installation comprises sender unit, signal receiving device and signal processing apparatus; Described signal processing apparatus is connected with described signal receiving device;
Described sender unit and described signal receiving device are arranged on line of electric force respectively.
Wherein, described sender unit and described signal receiving device are integrated on one piece of circuit board.
Wherein, described sender unit comprises the sender unit, power amplifier and the coupling mechanism that connect successively; The output terminal of described coupling mechanism is connected with line of electric force.
Wherein, described signal receiving device comprises spacer assembly and the signal pickup assembly of connection;
The input end of described spacer assembly is connected with described line of electric force;
The output terminal of described signal pickup assembly is connected with described signal processing apparatus.
Wherein, described signal pickup assembly comprises high-speed data acquisition card.
Wherein, described signal processing apparatus comprises computing machine; Described computing machine has signal processing function, adopts U/I algorithm to draw the modulus value of impedance, real part and imaginary part, determines the relation of real part, imaginary part and frequency, and fit to curve.
Compared with the prior art, beneficial effect of the present invention is:
(1) signal pickup assembly of the present invention utilizes high-speed collection card that the simulating signal gathered is carried out to discretize thus is convenient to calculate mass data, solve the acquisition problems of AC signal, this method safety, and counting yield is high, high-speed collection card used improves the resolution of collection signal device, measured frequency band range wider (30KHZ ~ 500KHZ), and the frequency resolution of common double-current probe method network analyzer used is lower, measured narrow band bandwidth scope is (300KHZ ~ 500KHZ), measured result can more accurately be reflected reality situation.
(2) U/I algorithm of the present invention not only can measure the modulus value of impedance, can also Impedance measurement, the relation of real part and imaginary part and frequency, and they and the relation of frequency are fitted to curve, can according to data calculate the relation of phase place and frequency, and data measured has continuity relative to frequency, overcome the inferior position that Dissipative Resistance by Harmonic Resonance Method impedance can only measure single frequency point, there is ubiquity.
(3) impedance that the calibrating principle that the present invention takes can produce proving installation internal component and the impedance that external connection line produces are eliminated the impact of power line impedance, make test result more accurate.
(4) the present invention makes carrier signal emitter, power amplifier, arrowband coupling mechanism, high-speed collection card, spacer assembly the form of circuit board, and five devices are integrated into one, and unified power supply, is easy to carry like this, is conducive to carrying out on-the-spot test.
(5) the present invention utilizes short circuit method and fixed value resistance access method to calibrate test circuit internal component and external connection, reduces test error.
(6) the present invention proposes a kind of method of testing of new low-voltage power line impedence, method is based on voltammetry (U/I) principle, adopt advanced high-speed signal acquisition technology, controlled to gather the narrowband carrier voltage signal in power circuit by computing machine, termination modulus value and phase place, imaginary part, the real part information of measured point is calculated by computing machine special software algorithm, and fit to termination-frequency curve, both improve the frequency resolution of proving installation, make measured data accuracy higher, make easy being easy to of measurement mechanism carry out on-the-spot test simultaneously.A kind of calibration steps for low-voltage power line testing impedance is also proposed in addition, impact power line access impedance produced in order to calibration testing inside circuit and external line.
Accompanying drawing explanation
Fig. 1 is the circuit diagram of proving installation provided by the invention access low-voltage power line.
Fig. 2 is signal acquisition process figure provided by the invention.
Fig. 3 is calibrating principle figure provided by the invention.
Fig. 4 is the structural drawing of proving installation provided by the invention access line of electric force.
Fig. 5 is the test result figure of the real part of low-voltage power line termination provided by the invention, imaginary part and modulus value.
Fig. 6 is the phase angle-frequency test result figure of low-voltage power line termination provided by the invention.
Embodiment
Below in conjunction with accompanying drawing, the specific embodiment of the present invention is described in further detail.
The proving installation of a kind of low-voltage power line narrowband carrier termination that the present embodiment provides, comprises sender unit, signal receiving device and signal processing apparatus; Described signal processing apparatus is connected with described signal receiving device;
Be connected on line of electric force by described sender unit and signal receiving device respectively by wire, as shown in Figure 4, its circuit diagram as shown in Figure 1.
Sender unit and signal receiving device are integrated on one piece of circuit board.Sender unit comprises the sender unit, power amplifier and the coupling mechanism that connect successively; The output terminal of described coupling mechanism is connected with line of electric force.Signal receiving device comprises spacer assembly and the signal pickup assembly of connection, and the input end of spacer assembly is connected with described line of electric force, and the output terminal of signal pickup assembly is connected with described signal processing apparatus.
The signal pickup assembly of the present embodiment comprises high-speed data acquisition card.Due to surveyed be termination on line of electric force, measured signal is that AC signal direct A.C. voltmeter or alternating current ammeter can not survey electric current and voltage, the signal that they survey is effective value, the instantaneous value requirement needed for us can not be met, count often due to measured again, very inconvenient for computing impedance, the signal collected is simulating signal, we adopt high-speed collection card to keep collected simulating signal, sampling, the discrete signal of gained is imported into PC, computing machine special software is used to write calculation procedure, so both solve the demand of instantaneous value, also solve data excessive and be not easy to calculate difficulty.And, the present embodiment utilizes high-speed collection card (RBW ≈ 30HZ) to solve, and frequency resolution is low causes the inaccurate problem of test result, whether the size of resolution bandwidth (RBW) can determine can two adjacent signals separately, the resolution bandwidth of capture card its frequency resolution lower is higher, but frequency resolution is too high can cause again gathering and computing time very long, so select the RBW of suitable capture card, the accuracy of collected signal can be ensured, the speed of collection signal and calculating can be ensured again.Conventional method such as double-current probe method Impedance measurement is that the RBW of the device of collection signal used is higher;
The signal processing apparatus of the present embodiment comprises computing machine; Described computing machine has signal processing function, adopts U/I algorithm to draw the modulus value of impedance, real part and imaginary part, determines the relation of real part, imaginary part and frequency, and fit to curve.
Corresponding, the method for testing of a kind of low-voltage power line narrowband carrier termination that the present embodiment proposes, comprises the steps:
(1) proving installation is set on line of electric force;
Wherein, proving installation is connected with line of electric force by wire;
(2) described proving installation is calibrated;
Its calibration reason is divided into two aspects, (1) impedance of itself due to line of electric force is very little, especially low pressure stage connecing as a lot of household load causes the line of electric force channel impedance of power distribution network low-pressure side to only have several ohm to tens ohm, the components and parts in test circuit likely make test error larger; (2) because the inventive method is aimed at field testing, p-wire needs to connect longer electric wire or cable when accessing line of electric force sometimes, the signal injecting line of electric force due to us is high-frequency signal, and the induction reactance that high-frequency signal produces over electrical wiring or cabling is larger, this part induction reactance will produce considerable influence to the impedance of surveyed line of electric force, so connected external cord or cable must be calibrated before test, make test result more accurate.
Described proving installation is calibrated and refers to the internal component of described proving installation and sometimes need when accessing line of electric force to be connected longer electric wire with p-wire or cable is calibrated,
In order to reach the object of calibration, we need to determine the numerical value of some the circuit components parameters in proving installation, as shown in Figure 3, transformer primary side is connected with alternating message source, its secondary is connected with wire, the circuit that secondary connects is the circuit of coupling device and high-speed collection card center section in Fig. 1, determines that the numerical value of these parameters principle used is as follows:;
1. L, N two terminal shortcircuit obtain U
_{m1}and U
_{n1}, Z
_{2}be fixed value resistance, the impedance Z of the part be made up of an electric capacity and fixed value resistance can be obtained like this
_{1}:
$\frac{{U}_{m1}}{{U}_{n1}}{Z}_{2}={Z}_{1};$
In formula, U
_{m1}for Z
_{1}the voltage at two ends; U
_{n1}for Z
_{2}the voltage at two ends; Z
_{2}for unknown impedance; Z
_{1}for the impedance of electric capacity and fixed value resistance ingredient;
2. a fixed resistance Z is accessed at L, N two ends
_{d}, in like manner can obtain U with (1)
_{m2}and U
_{n2}, obtain:
$\frac{{U}_{m2}}{{U}_{n2}}{Z}_{2}={Z}_{1}+{Z}_{D};$
In formula, U
_{m2}for Z
_{1}the voltage at two ends; U
_{n2}for Z
_{2}the voltage at two ends; Z
_{2}for unknown impedance; Z
_{1}for the impedance of electric capacity and fixed value resistance ingredient; Z
_{d}for known fixed value resistance;
Can be obtained by above two steps:
${Z}_{2}=\frac{{Z}_{D}}{(\frac{{U}_{m2}}{{U}_{n2}}-\frac{{U}_{m1}}{{U}_{n1}})},$
${Z}_{1}=\frac{{U}_{m1}}{{U}_{n1}}{Z}_{2};$
So just obtain impedance Z required in test circuit
_{1}in fixed value resistance R
_{1}with value and the Z of electric capacity C
_{2}.When carrying out on-the-spot test, we must first carry out short circuit the signal wire of proving installation and access fixed value resistance Z again
_{d}calibrate, needing when needs external cord or cable is connected external cord (cable) with signal wire carries out aforesaid operations again, to eliminate impedance that inside circuit components and parts and external cord produce when high-frequency signal flows through to the impact of test result.
(3) described proving installation sends a signal on line of electric force, and its step comprises;
1) sender unit of proving installation produces signal to power amplifier;
2) described power amplifier passes to described coupling mechanism after being amplified by signal;
3) described coupling mechanism couples a signal on line of electric force.
(4) described proving installation receives the data of the termination of returning that to be coupled from line of electric force, and become the frequency curve of termination according to described data fitting, and show, its whole test process as shown in Figure 2.Wherein,
Step (4) specifically comprises the steps:
The line of electric force of signal pickup assembly and electrical network is isolated by A, spacer assembly;
B, described signal pickup assembly collection line of electric force is coupled the data of returning, and data are passed to signal processing apparatus;
C, described signal processing apparatus draw the real part of termination, imaginary part and frequency according to described data, fit to the frequency curve of termination, and show.
As shown in Figure 1, gathered the voltage signal of A point and B point, be sent to PC by USB interface by high-speed collection card, use the software programming calculation procedure in PC to calculate the value of impedance, principle used is as follows:
${U}_{A}=U+I({R}_{1}+\frac{1}{\mathrm{j\ωC}});$
In formula, U
_{a}for the voltage signal of A point; U is the voltage at L, N two ends; I is the electric current flowing through test circuit; R
_{1}for fixed value resistance; ω is the angular frequency of input signal; C is definite value electric capacity;
$Z=\frac{U}{I}=\frac{{U}_{A}}{I}-{R}_{1}+j\frac{1}{\mathrm{\ωC}};$
In formula, the impedance of line of electric force of Z for surveying;
$Z=\frac{{U}_{A}}{{U}_{B}}\·{R}_{2}-{R}_{1}+j\frac{1}{\mathrm{\ωC}}=-\left|\frac{{U}_{A}}{{U}_{B}}\right|\·{R}_{2}[\mathrm{cos}(\∠\{{U}_{A},{U}_{B}\left\}\right)+j\mathrm{sin}(\∠\{{U}_{A},{U}_{B}\left\}\right)]-{R}_{1}+j\frac{1}{\mathrm{\ωC}}$
In formula, R
_{2}for the fixed value resistance in sender unit; U
_{b}for the voltage signal of B point;
We can calculate the modulus value of impedance, imaginary part to use computing formula above, real part, the relation of phase place and frequency, and are continuous print, become curve for analyzing the Changing Pattern of impedance the data fitting calculated.
The present embodiment test result schematic diagram as shown in Figure 5 and Figure 6, Fig. 5 gives impedance magnitude, imaginary part, the real part of the termination of test, and according to the test result of gained, can use the data surveyed of real part and imaginary part, draw the relation of phase place and frequency, as shown in Figure 6.Whether the present invention goes out capacitive reactance and induction reactance on line of electric force by the impedance magnitude of termination, the data analysis such as imaginary part and real part, can monitor line of electric force and break down.
U/I software for calculation used can show modulus value, real part, the imaginary part information of impedance simultaneously.Because line of electric force is distributed inductance when high-frequency signal transmits, distributed capacitance can have an impact, also have line of electric force load itself and occur resonance phenomena between load and line of electric force within the scope of certain frequency, so, be necessary the change along with frequency of the understanding imaginary part of impedance and the phase place of impedance.
Finally should be noted that: above embodiment is only in order to illustrate that technical scheme of the present invention is not intended to limit, although with reference to above-described embodiment to invention has been detailed description, those of ordinary skill in the field are to be understood that: still can modify to the specific embodiment of the present invention or equivalent replacement, and not departing from any amendment of spirit and scope of the invention or equivalent replacement, it all should be encompassed in the middle of right of the present invention.