A method and system for parameter measurement

Abstract

The application provides a parameter measurement method suitable for measurement of a grid-to-ground parameter, characterized in that an output device is connected to a grid through a grounding transformer, and the output device is preset with an output power, step S1, the output device outputs a variable frequency waveform to the grid through the grounding transformer according to the output power; step S2, a measurement device collects grid data of multiple different frequency points in the variable frequency waveform, and processes to obtain the grid-to-ground parameter. Advantage: the technical scheme of the application can effectively eliminate the interference of public frequency signals, reduce the influence of the injected signal on the grid, and increase the power and current and voltage to make the measurement more accurate.

Description

Technical Field

[0001] This invention relates to a parameter measurement method and system, and more particularly to a method for measuring ground parameters using cascaded module frequency conversion signals. Background Technology

[0002] In the power grid sector, ground parameters play a crucial role. They are indispensable for the proper tuning of arc suppression coils, improving the success rate of operation, preventing overvoltage accidents, and ensuring the safe operation of the power system. They also significantly influence the effectiveness of power electronic compensation devices. Parameters that need to be measured in a resonant grounding system include capacitive current and damping rate.

[0003] Traditional power distribution network parameter measurement methods are diverse, including direct methods, indirect methods, and estimation methods. Direct methods primarily include the single-phase metallic grounding method. Indirect methods encompass various types, such as the applied voltage method, tuning method, applied capacitor method, frequency conversion method, and capacitance increment method. Currently, worldwide, methods for measuring the capacitance of ungrounded neutral power grids from the secondary side of voltage transformers have been proposed. These methods include resonant measurement and voltage transformer secondary side signal injection methods. We know that voltage transformer secondary side injection methods include phasor methods, two-frequency methods, and three-frequency methods. However, when using transformers for injection, problems arise such as varying impedances among voltage transformers, excessive system impedance leading to low output power, and inaccurate sampling due to small sample sizes. Summary of the Invention

[0004] To address the shortcomings of the prior art, the present invention provides a parameter measurement method applicable to the measurement of power grid-to-ground parameters. The method is characterized by employing an output device connected to the power grid via a grounding transformer, and pre-setting the output power of the output device.

[0005] Step S1: Using the output device, a frequency conversion waveform is output to the power grid through the grounding transformer according to the output power;

[0006] Step S2: A measuring device is used to collect power grid data at multiple different frequency points in the frequency conversion waveform, and the power grid's ground parameters are obtained through processing.

[0007] Preferably, in step S1, the output device is formed by sequentially cascading multiple output modules;

[0008] The output terminal of the first output module is connected to an injection inductor, the input of the first output module is connected to the output terminal of the next output module, and the input terminal of the last output module is grounded.

[0009] Preferably, the output terminal of the output device is connected to a first node through the injection inductor, and the first node is connected to the grounding transformer;

[0010] In step S2, the power grid data includes voltage data acquired using a voltage transformer.

[0011] The voltage transformer is connected in series between the injected inductor and the first node.

[0012] Preferably, in step S2, the power grid data further includes first current data acquired using a current transformer;

[0013] The current transformer is connected in series between a resonant inductor and the ground terminal;

[0014] The other end of the resonant inductor is connected to the first node.

[0015] Preferably, in step S2, the power grid data further includes second current data acquired using a Hall sensor;

[0016] The Hall sensor is connected in series between the input terminal and the ground terminal of the last output module.

[0017] Preferably, in step S2, the ground parameters are obtained using the following formula:

[0018] Uph=2500*IL*(I1 / f1-I2 / f2) / (f1*I1-f2*I2);

[0019] Ic=50*Uph*(U1 / f1-U2 / f2) / ( U1- U2);

[0020] in,

[0021] Uph is the rated voltage of the output device;

[0022] Ic is the ground parameter;

[0023] U1 is the voltage data acquired at a first frequency;

[0024] U2 is the voltage data acquired at a second frequency;

[0025] I1 is the second current data acquired at the first frequency;

[0026] I2 is the second current data acquired at the second frequency;

[0027] IL represents the first current data;

[0028] f1 is the first frequency;

[0029] f2 is the second frequency.

[0030] The technical solution of the present invention also provides a parameter measurement system, applied to any of the parameter measurement methods described above, comprising,

[0031] The output device is connected to the power grid via a grounding transformer, and is used to output a frequency-converted waveform to the power grid through the grounding transformer according to the output power.

[0032] The measuring device, connected to the output device, is used to collect power grid data at multiple different frequency points in the frequency conversion waveform and calculate the power grid's parameters relative to ground.

[0033] Preferably, the output device includes multiple cascaded output modules connected in sequence, with the output terminal of the first output module connected to an injection inductor, the input terminal of the first output module connected to the output terminal of the next output module, and the input terminal of the last output module grounded.

[0034] The output device also includes an injection inductor and a resonant coil.

[0035] The injected inductor is connected to the output terminal of the first output module and, through the first node, to the secondary side of the grounding transformer.

[0036] One end of the resonant coil is grounded, and the other end is connected to the secondary side of the grounding transformer through the first node.

[0037] Preferably, the measuring device includes,

[0038] A controller calculates the ground parameters of the power grid using the power grid data;

[0039] A voltage transformer is connected to the controller and is used to collect voltage data from the power grid data. The voltage transformer is connected to the controller and is placed between the injected inductor and the first node.

[0040] A Hall sensor, connected to the controller, is used to collect the second current data and is placed between the input terminal of the last output module and a ground terminal;

[0041] A current transformer, connected to the controller, is used to collect the first current data and is placed between the resonant coil and the grounding terminal.

[0042] Preferably, the power grid is a three-phase circuit, and each phase of the circuit includes a grounding unit.

[0043] Each of the grounding units consists of a resistor and a capacitor connected in parallel, and the alternating current through the capacitor is the capacitance current to ground.

[0044] Beneficial effects: The technical solution of the present invention can effectively eliminate interference from public frequency signals, reduce the impact of injected signals on the power grid, and increase power to improve current and voltage, making the measurement more accurate. Attached Figure Description

[0045] Figure 1 A flowchart of a parameter measurement method is provided in a preferred embodiment of the present invention.

[0046] Figure 2 This is a schematic diagram of the structure of a parameter measurement system in a preferred embodiment of the present invention. Detailed Implementation

[0047] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0048] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0049] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but this is not intended to limit the scope of the invention.

[0050] This invention provides a parameter measurement method applicable to the measurement of power grid parameters to ground. Its key feature is the use of an output device connected to the power grid via a grounding transformer, with the output power of the output device pre-set.

[0051] Step S1: The output device outputs a frequency conversion waveform to the power grid through a grounding transformer according to the output power.

[0052] Step S2: Use a measuring device to collect power grid data at multiple different frequency points in the frequency conversion waveform, and calculate the power grid's ground parameters.

[0053] Specifically, in this embodiment, the measuring device includes multiple sensors, which are integrated into the controller within the measuring device and connected to the test point in the circuit under test via a port. It can be flexibly applied to different power grids. The measuring device also receives the signal of the measurement parameters through a controller, controls the cascaded output module, uses SPWM to control the measurement output, and injects the frequency conversion voltage and current signal into the power grid through the grounding transformer after the reactance.

[0054] In a preferred embodiment of the present invention, in step S1, an output device is formed by sequentially cascading multiple output modules;

[0055] The output of the first output module is connected to an injection inductor, the input of the first output module is connected to the output of the next output module, and the input of the last output module is grounded.

[0056] Specifically, in this embodiment, each of the above-mentioned output modules is composed of a single-phase full-bridge inverter circuit, which can realize a wide range of output power. They are connected in sequence, including four IGBT sub-modules. Starting from the second output module, the output terminal of the output module is connected between a first IGBT sub-module and a second IGBT sub-module, and the input module is connected between a third IGBT and a fourth IGBT sub-module.

[0057] In a preferred embodiment of the present invention, the output terminal of the output device is connected to a first node via an injection inductor, and the first node is connected to a grounding transformer.

[0058] In step S2, the power grid data includes voltage data acquired using a voltage transformer.

[0059] The voltage transformer is connected in series between the injection inductor and the first node.

[0060] Specifically, in this embodiment, the voltage data is generated based on preset data and is obtained by injecting an inductor.

[0061] In a preferred embodiment of the present invention, in step S2, the power grid data further includes first current data acquired using a current transformer.

[0062] A current transformer is connected in series between a resonant inductor and the ground terminal;

[0063] The other end of the resonant inductor is connected to the first node.

[0064] Specifically, in this embodiment, the second current data collected by the current transformer is the circuit current from the input terminal of the last output module to the ground terminal; the first current data collected by the current transformer is the circuit current from the first node through the resonant inductor grounding line.

[0065] In a preferred embodiment of the present invention, in step S2, the power grid data further includes second current data acquired using a Hall sensor;

[0066] The Hall sensor is connected in series between the input terminal and the ground terminal of the last output module.

[0067] Specifically, in this embodiment, the current phase of the resonant inductor lags behind its voltage phase by 90°. Therefore, when an impedance element with inductance is connected to the circuit, in addition to absorbing active power from the power source, it also needs to absorb reactive power. Therefore, a capacitor whose current phase leads its voltage phase by 90° also needs to be connected.

[0068] In a preferred embodiment of the present invention, the measuring device obtains the ground parameters using the following formula:

[0069] Uph=2500*IL*(I1 / f1-I2 / f2) / (f1*I1-f2*I2);

[0070] Ic=50*Uph*(U1 / f1-U2 / f2) / ( U1- U2);

[0071] in,

[0072] Uph is the rated voltage of the output device;

[0073] Ic is the ground parameter;

[0074] U1 is the voltage data acquired at a first frequency;

[0075] U2 is the voltage data acquired at a second frequency;

[0076] I1 is the second current data acquired at the first frequency;

[0077] I2 represents the second current data acquired at the second frequency.

[0078] IL represents the first current data;

[0079] f1 is the first frequency;

[0080] f2 is the second frequency.

[0081] Specifically, in this embodiment, Ic is the capacitor current in the filter circuit of the power grid. This device can smooth out fluctuations in the circuit and improve accuracy.

[0082] The present invention also provides a parameter measurement system, applied to any of the above-mentioned parameter measurement methods, characterized in that it comprises,

[0083] Output device 1 is connected to power grid 4 through a grounding transformer 3, and is used to output a frequency conversion waveform to power grid 4 through grounding transformer 3 according to the output power;

[0084] Measuring device 2, connected to output device 1, is used to collect data from the power grid 4 at multiple different frequency points in the frequency conversion waveform and calculate the ground parameters of the power grid 4.

[0085] Specifically, in this embodiment, the output device 1 is connected to the power grid 4 through a grounding transformer 3, and a frequency-converted signal is injected into the power grid 4 system through the center point of the grounding transformer 3. The measuring device 2 also includes a comparison submodule, which confirms whether the data to be collected is the required data by comparing different frequencies.

[0086] In a preferred embodiment of the present invention, the output device 1 includes a plurality of cascaded output modules 11, each output module 11 being composed of a single-phase full-bridge inverter circuit and connected in sequence. The output terminal of the first output module 11 is connected to an injection inductor 12, the input terminal of the first output module 11 is connected to the output terminal of the next output module 11, and the input terminal of the last output module 11 is grounded.

[0087] The output device 1 also includes an injection inductor 12 and a resonant coil 13.

[0088] The injection inductor 12 is connected to the output terminal of the first output module 11, and is connected to the grounding transformer 3 through the first node.

[0089] One end of the resonant coil 13 is grounded, and the other end is connected to the grounding transformer 3 through the first node.

[0090] Specifically, in this embodiment, the power grid 4 wire is grounded via resonant coil 13, i.e., the arc suppression coil. During normal operation, no current flows through the arc suppression coil. However, when power grid 4 is struck by lightning or experiences a single-phase arcing ground fault, the neutral point potential rises to the phase voltage. At this time, the inductive current flowing through the arc suppression coil cancels out the capacitive fault current of the single-phase ground fault, thus compensating for the fault current. The residual current after compensation becomes very small and insufficient to sustain the arc, causing it to extinguish itself. In this way, the ground fault can be quickly eliminated without causing overvoltage.

[0091] In a preferred embodiment of the present invention, the measuring device 2 includes,

[0092] A controller 21 calculates the ground parameters of power grid 4 using data from power grid 4;

[0093] A voltage transformer 22 is connected to the controller 21 and is used to collect voltage data from the collected power grid 4 data. The voltage transformer 22 is connected to the controller 21 and is placed between the injection inductor 12 and the first node.

[0094] A Hall sensor 23, connected to the controller 21, is used to collect second current data and is placed between the input terminal of the last output module 11 and a ground terminal.

[0095] A current transformer 24 is connected to a controller 21 and is used to collect the first current data. It is placed between the resonant coil 13 and the ground terminal.

[0096] Specifically, in this embodiment, since a magnetic field exists inside the circuit, and its magnitude is proportional to the current in the wire, the Hall sensor 23 can be used to measure the magnetic field, thereby determining the magnitude of the current in the wire. Based on this principle, a Hall current sensor can be designed and manufactured. The Hall sensor 23 does not make electrical contact with the circuit under test, does not affect the circuit under test, and does not consume the power of the power supply under test, making it suitable for high-current sensing.

[0097] In a preferred embodiment of the present invention, the power grid 4 is a three-phase circuit, and each phase of the circuit includes a grounding unit 41.

[0098] Each grounding unit 41 consists of a resistor and a capacitor connected in parallel, and the alternating current through the capacitor is the capacitance current to ground.

[0099] Specifically, in this embodiment, it is composed of three single-phase transformers connected in three phases in the circuit, and the main magnetic flux of each phase forms a separate loop along its own iron core;

[0100] Under different power frequency conditions, the capacitive reactance generated by the capacitor is also different, and the current flowing through the capacitor does not generate power consumption in the capacitor.

[0101] The above description is merely a preferred embodiment of the present invention and does not limit the implementation and protection scope of the present invention. Those skilled in the art should realize that any equivalent substitutions and obvious changes made based on the description and illustrations of the present invention should be included within the protection scope of the present invention.

Claims

1. A parameter measurement method, applicable to the measurement of power grid-to-ground parameters, characterized in that, An output device is used, which is connected to the power grid through a grounding transformer, and the output power of the output device is preset. Step S1: Using the output device, a frequency conversion waveform is output to the power grid through the grounding transformer according to the output power; Step S2: Use a measuring device to collect power grid data at multiple different frequency points in the frequency conversion waveform, and process the data to obtain the power grid's ground parameters; In step S1, the output device is formed by sequentially cascading multiple output modules. The output terminal of the first output module is connected to an injection inductor, the input of the first output module is connected to the output terminal of the next output module, and the input terminal of the last output module is grounded. The output terminal of the output device is connected to a first node through the injection inductor, and the first node is connected to the grounding transformer. In step S2, the power grid data includes voltage data acquired using a voltage transformer. The voltage transformer is connected in series between the injected inductor and the first node; In step S2, the power grid data also includes first current data acquired using a current transformer. The current transformer is connected in series between a resonant inductor and the ground terminal; The other end of the resonant inductor is connected to the first node; In step S2, the power grid data also includes second current data acquired using a Hall sensor; The Hall sensor is connected in series between the input terminal and the ground terminal of the last output module; In step S2, the ground parameters are obtained using the following formula. Uph=2500*IL*(I1 / f1-I2 / f2) / (f1*I1-f2*I2); Ic=50*Uph*(U1 / f1-U2 / f2) / ( U1- U2); in, Uph is the rated voltage of the output device; Ic is the ground parameter; U1 is the voltage data acquired at a first frequency; U2 is the voltage data acquired at a second frequency; I1 is the second current data acquired at the first frequency; I2 is the second current data acquired at the second frequency; IL represents the first current data; f1 is the first frequency; f2 is the second frequency.

2. A parameter measurement system, characterized in that, The parameter measurement method applied to claim 1 includes: The output device is connected to the power grid via a grounding transformer, and is used to output a frequency-converted waveform to the power grid through the grounding transformer according to the output power. The measuring device, connected to the output device, is used to collect power grid data at multiple different frequency points in the frequency conversion waveform and calculate the power grid's parameters relative to ground.

3. The parameter measurement system as described in claim 2, characterized in that, The output device comprises multiple cascaded output modules connected in sequence. The output terminal of the first output module is connected to an injection inductor, the input terminal of the first output module is connected to the output terminal of the next output module, and the input terminal of the last output module is grounded. The output device also includes an injection inductor and a resonant coil. The injected inductor is connected to the output terminal of the first output module and, through the first node, to the secondary side of the grounding transformer. One end of the resonant coil is grounded, and the other end is connected to the secondary side of the grounding transformer through the first node.

4. The parameter measurement system as described in claim 3, characterized in that, The measuring device includes, A controller calculates the ground parameters of the power grid using the power grid data; A voltage transformer is connected to the controller and is used to collect voltage data from the power grid data. The voltage transformer is connected to the controller and is placed between the injected inductor and the first node. A Hall sensor, connected to the controller, is used to collect the second current data and is placed between the input terminal of the last output module and a ground terminal; A current transformer, connected to the controller, is used to collect the first current data and is placed between the resonant coil and the grounding terminal.

5. A parameter measurement system as described in claim 2, characterized in that, The power grid is a three-phase circuit, and each phase of the circuit includes a grounding unit. Each of the grounding units consists of a resistor and a capacitor connected in parallel, and the alternating current through the capacitor is the capacitance current to ground.

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