Broadband impedance measuring device and broadband impedance sweep frequency measuring method

Abstract

The invention discloses a broadband impedance measurement device and a broadband impedance sweep frequency measurement method, and the device comprises a main path input switch, a disturbance control and gain calculation module, a main path output switch, and single-phase measurement units, wherein the number of the single-phase measurement units is equal to the number of electric phases of a power grid. The single-phase measurement unit comprises a broadband disturbance generator, an output filtering unit, a coupling transformer, a disturbance detection unit, a bypass switch and an output voltage and current detection unit. The disturbance control and gain calculation module is connected with the disturbance detection unit, the output voltage and current detection unit and the broadband disturbance generator. The method comprises the steps of injecting disturbance according to a sweep frequency point table; extracting disturbance response voltage according to the voltage of the secondary winding of the coupling transformer; calculating a disturbance gain according to the disturbance injection voltage and the disturbance response voltage; and comparing the disturbance gain with a preset risk gain threshold value and a preset early warning gain threshold value, and performing control according to a comparison result.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of power system grid-connected detection technology, and particularly relates to a wideband impedance measuring device and a wideband impedance sweep frequency measuring method. BACKGROUND

[0002] With the rapid development of power electronics technology, in the field of new energy power generation, large-scale new energy power generation equipment is connected to the power grid, but the impedance characteristics of the power grid affect the stable operation and control of power electronic devices such as wind and photovoltaic grid-connected inverters. Moreover, new energy power generation equipment cannot be represented as an ideal current source, resulting in the interactive coupling of weak power grid impedance and new energy power generation equipment impedance, affecting the stable operation of the new energy power generation system. Therefore, accurate measurement of the impedance of new energy power generation equipment is of great significance to the stability research of large-scale new energy grid-connected power generation systems.

[0003] However, the existing impedance characteristic measurement methods and devices are mostly for low-voltage and small-capacity new energy power generation equipment and micro-grid systems, and it is difficult to meet the requirements of impedance characteristic measurement of power generation equipment in new energy power generation bases, and the accuracy of impedance characteristic measurement is low. SUMMARY

[0004] The technical problem to be solved by the present application is to provide a wideband impedance measuring device and a wideband impedance sweep frequency measuring method to improve the accuracy and adaptability of impedance characteristic measurement.

[0005] In a first aspect, the present application provides a wideband impedance measuring device electrically connected between a power grid and a measured power generation equipment, the wideband impedance measuring device comprising a main path input switch, a disturbance control and gain calculation module, a main path output switch, and a number of single-phase measuring units equal to the number of electrical phases of the power grid. Each single-phase measuring unit is connected to the corresponding electrical phase of the power grid through the main path input switch. The single-phase measuring unit is connected to the measured power generation equipment through the main path output switch. The single-phase measuring unit comprises a wideband disturbance generator, an output filter unit, a coupling transformer, a disturbance detection unit, a bypass switch, and an output voltage and current detection unit. The output voltage and current detection unit is connected to the corresponding electrical phase of the power grid through the main path input switch after passing through the bypass switch. The output voltage and current detection unit is connected to the measured power generation equipment through the main path output switch. The disturbance control and gain calculation module is connected to the disturbance detection unit, the output voltage and current detection unit, and the wideband disturbance generator. The wideband disturbance generator is connected to the primary winding of the coupling transformer through the output filter unit. The secondary winding of the coupling transformer is connected to the bypass switch. The disturbance detection unit is connected in parallel with the bypass switch. The disturbance detection unit is electrically connected between the two ends of the secondary winding of the coupling transformer.

[0006] In a second aspect, the present application also provides a wideband impedance sweep frequency measurement method applied to the wideband impedance measurement device, which comprises the following steps: the disturbance control and gain calculation module reads the pre-stored sweep frequency point table, sequentially sets the disturbance injection voltage according to the disturbance voltage value corresponding to each frequency point of the pre-stored sweep frequency point table, and the wideband disturbance generator performs disturbance injection operation on the power grid; the disturbance control and gain calculation module extracts the disturbance response voltage according to the voltage of the secondary winding of the coupling transformer detected by the disturbance detection unit; the disturbance control and gain calculation module calculates the disturbance gain according to the disturbance injection voltage and the disturbance response voltage; the disturbance control and gain calculation module compares the disturbance gain with the preset early warning gain threshold and the preset risk gain threshold respectively, and adjusts and controls the disturbance injection according to the comparison result.

[0007] The wideband impedance measurement device of the present application is electrically connected between the power grid and the measured power generation equipment, and comprises a main path input switch, a disturbance control and gain calculation module, a main path output switch, and a number of single-phase measurement units equal to the number of electrical phases of the power grid. Each single-phase measurement unit is connected to the corresponding electrical phase of the power grid through the main path input switch, and is connected to the measured power generation equipment through the main path output switch. The single-phase measurement unit comprises a wideband disturbance generator, an output filter unit, a coupling transformer, a disturbance detection unit, a bypass switch, and an output voltage and current detection unit. The disturbance is injected into the power grid by using disturbance coupling, and the main power loop passes through the power grid, so that the wideband impedance measurement device only needs to withstand the response power of the disturbance part, which can reduce the capacity requirement of the wideband impedance measurement device, realize application in high-voltage high-power systems, meet the fine requirements of impedance characteristic measurement of power generation equipment in new energy power generation bases, have high adaptability, reduce the influence of the wideband impedance measurement device on the fundamental wave of the power grid, realize high-precision disturbance measurement, and ensure measurement accuracy and system safety. The wideband impedance sweep frequency measurement method of the present application also has the above functions. BRIEF DESCRIPTION OF DRAWINGS

[0008] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0009] Figure 1 A circuit diagram of the wideband impedance measurement device provided by the embodiment of the present application in application; Figure 2 A flowchart of the wideband impedance sweep measurement method provided by the embodiment of the present application; Figure 3 A simulation waveform diagram of the voltage detected by the disturbance detection unit and the disturbance gain when the traditional impedance measurement method is continuously and automatically swept; Figure 4 A simulation waveform diagram of the voltage detected by the disturbance detection unit and the disturbance gain when the wideband impedance sweep measurement method provided by the embodiment of the present application is continuously and automatically swept. DETAILED DESCRIPTION

[0010] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all the other embodiments obtained by those of ordinary skill in the art without creative effort belong to the scope of the present application.

[0011] Please refer to Figure 1 , Figure 1The circuit diagram of the wideband impedance measuring device provided by the embodiment of the present application is applied to the wideband impedance measuring device 10 electrically connected between the power grid 20 and the measured power generation equipment 30. The wideband impedance measuring device 10 comprises a main path input switch 11, a disturbance control and gain calculation module 12, a main path output switch 13, and a single-phase measuring unit 14 equal in number to the number of electrical phases of the power grid 20. Each single-phase measuring unit 14 is connected to the corresponding electrical phase of the power grid 20 through the main path input switch 11. The single-phase measuring unit 14 is connected to the measured power generation equipment 30 through the main path output switch 13. The single-phase measuring unit 14 comprises a wideband disturbance generator 141, an output filter unit 142, a coupling transformer 143, a disturbance detection unit 144, a bypass switch 145, and an output voltage and current detection unit 146. Each output voltage and current detection unit 146 is connected to the corresponding electrical phase of the power grid 20 through the main path input switch 11 after passing through the bypass switch 145. The output voltage and current detection unit 146 is connected to the measured power generation equipment 30 through the main path output switch 13. The disturbance control and gain calculation module 12 is connected to the disturbance detection unit 144, the output voltage and current detection unit 146, and the wideband disturbance generator 141. The wideband disturbance generator 141 is connected to the primary winding of the coupling transformer 143 through the output filter unit 142. The secondary winding of the coupling transformer 143 is connected to the bypass switch 145. The disturbance detection unit 144 is connected in parallel to the bypass switch 145. The disturbance detection unit 144 is electrically connected between the two ends of the secondary winding of the coupling transformer 143.

[0012] In this embodiment, the number of electrical phases of the power grid 20 is 3, i.e., the power grid 20 is a three-phase power grid. The power grid 20 can be a three-phase power grid with a voltage value of 220 kV. Therefore, the wideband impedance measuring device 10 comprises three single-phase measuring units 14, and one single-phase measuring unit 14 corresponds to and is connected to one phase of the power grid 20. The disturbance control and gain calculation module 12 is connected to the disturbance detection unit 144, the output voltage and current detection unit 146, and the wideband disturbance generator 141 of each single-phase measuring unit 14, Figure 1The connection lines of the disturbance detection unit 144, the output voltage and current detection unit 146, and the wide-band disturbance generator 141 of the remaining two single-phase measurement units 14 and the disturbance control and gain calculation module 12 are omitted to avoid disordered connection lines. Of course, in other embodiments, the number of electrical phases of the power grid 20 can be 1, 2, or more than 3. The power grid 20 can be connected to the wide-band impedance measurement device 10 through the box transformer 40, and the voltage value input to the wide-band impedance measurement device 10 through the box transformer 40 is 35 kV. The output voltage and current detection unit 146 includes a voltage detection unit for detecting the output voltage and a current detection unit for detecting the output current. The power supply 15 of the wide-band disturbance generator 141 can be isolated from the power grid 20, and the power supply voltage of the wide-band disturbance generator can be 690 V. The wide-band impedance measurement device 10 is electrically connected between the power grid 20 and the measured power generation equipment 30, and includes a main path input switch 11, a disturbance control and gain calculation module 12, a main path output switch 13, and a number of single-phase measurement units 14 equal to the number of electrical phases of the power grid 20. Each single-phase measurement unit 14 is connected to the corresponding electrical phase of the power grid 20 through the main path input switch 11, and the single-phase measurement unit 14 is connected to the measured power generation equipment 30 through the main path output switch 13. The single-phase measurement unit 14 includes a wide-band disturbance generator 141, an output filter unit 142, a coupling transformer 143, a disturbance detection unit 144, a bypass switch 145, and an output voltage and current detection unit 146. By using disturbance coupling to inject disturbance into the power grid, the main power loop passes through the power grid 20, so that the wide-band impedance measurement device 10 only needs to withstand the response power of the disturbance part, which can reduce the body capacity requirement of the wide-band impedance measurement device 10, realize the application in a high-voltage high-power system, meet the fine requirements of impedance characteristic measurement of power generation equipment in new energy power generation bases, have high adaptability, and can also reduce the influence of the wide-band impedance measurement device 10 on the fundamental wave of the power grid 20, realize high-precision disturbance measurement, and moreover, by setting the disturbance control and gain calculation module 12 to sample the voltage of the secondary winding of the coupling transformer 143 and calculate and analyze the disturbance gain, by comparing the disturbance gain with the preset early warning gain threshold and the preset risk gain threshold, respectively, the resonance band is pre-judged and avoided, the resonance band risk is effectively avoided, and the measurement accuracy and system safety are ensured.

[0013] The disturbance control and gain calculation module 12 can adopt an MCU or a single-chip microcomputer, be used for reading a pre-stored frequency sweep point table, sequentially set a disturbance injection voltage according to a disturbance voltage value corresponding to each frequency point of the pre-stored frequency sweep point table, and control the wide-band disturbance generator 141 to perform a disturbance injection operation on the power grid according to the set disturbance injection voltage; extract a disturbance response voltage according to a voltage of a secondary winding of the coupling transformer 143 detected and obtained by the disturbance detection unit 144; calculate a disturbance gain according to the disturbance injection voltage and the disturbance response voltage; compare the disturbance gain with a pre-set early warning gain threshold and a pre-set risk gain threshold respectively, and perform a disturbance injection adjustment control according to a comparison result, and judge whether there is a next frequency point in the pre-stored frequency sweep point table, and end the frequency sweep measurement when there is no next frequency point in the pre-stored frequency sweep point table. The pre-set early warning gain threshold and the pre-set risk gain threshold can be obtained by threshold conversion based on a disturbance injection amount and an upper limit of a harmonic content allowed by a stable operation of the measured power generation equipment 30.

[0014] Preferably, the output filter unit 142 includes an inductor and a capacitor, one end of an output end of the wide-band disturbance generator 141 is connected to a first end of a primary winding of the coupling transformer 143 and a first end of the capacitor through the inductor, and the other end of the output end of the wide-band disturbance generator 141 is connected to a second end of the primary winding of the coupling transformer 143 and a second end of the capacitor.

[0015] Specifically, the wide-band disturbance generator 141 includes a bidirectional rectifier and a variable frequency inverter, and the wide-band disturbance generator 141 can output a disturbance injection voltage with a frequency range of 1-2000 Hz. In an embodiment, the number of bidirectional rectifiers is one, and the number of variable frequency inverters can be multiple, the bidirectional rectifier and the variable frequency inverter share a common bus, and multiple variable frequency inverters can output a single-phase disturbance voltage in a wave superposition manner.

[0016] In another embodiment, multiple variable frequency inverters can independently output a multi-phase disturbance.

[0017] Of course, in other embodiments, the number of bidirectional rectifiers is multiple, and the number of variable frequency inverters is multiple, the bidirectional rectifiers and the variable frequency inverters are connected one by one and correspond to each other, and multi-phase disturbance voltage independent output is realized.

[0018] Specifically, the coupling transformer 143 adopts a three-phase four-core column wide-band coupling transformer, which is used for decoupling a phase-to-phase disturbance voltage, and the disturbance injection voltage output by the wide-band disturbance generator 141 is coupled by the coupling transformer 143 and then injected into the power grid 20, so that the transmission of the disturbance injection voltage with a frequency range of 1-2000 Hz can be realized. In some embodiments, the coupling transformer 143 can be a three-phase five-core column wide-band coupling transformer. Of course, in other embodiments, the coupling transformer 143 can be a single-phase transformer.

[0019] Specifically, the disturbance detection unit 144 is a voltage transformer for detecting the voltage of the secondary winding of the coupling transformer 143. The disturbance detection unit 144 can adopt a high-precision electronic voltage transformer, which can support wide-band high-precision voltage detection, and the voltage detection precision is not greater than 0.2%.

[0020] Referring to Figure 2 , Figure 2 A flowchart of a wide-band impedance sweep measurement method provided by an embodiment of the present application is provided. The wide-band impedance sweep measurement method is applied to the wide-band impedance measurement device described above. The wide-band impedance sweep measurement method comprises steps S10-S40: S10: The disturbance control and gain calculation module reads the pre-stored sweep point table, and sequentially sets the disturbance injection voltage according to the disturbance voltage value corresponding to each frequency point of the pre-stored sweep point table, and samples the wide-band disturbance generator for disturbance injection operation on the power grid.

[0021] S20: The disturbance control and gain calculation module extracts the disturbance response voltage according to the voltage of the secondary winding of the coupling transformer detected by the disturbance detection unit.

[0022] In some embodiments, before the step S20, the wide-band impedance sweep measurement method further comprises: The disturbance control and gain calculation module initially sets the disturbance injection voltage to 0, and when the disturbance injection voltage is 0, the voltage of the secondary winding of the coupling transformer detected by the disturbance detection unit is obtained as the fundamental response voltage amplitude, and the fundamental response voltage amplitude is stored. Then, before the sweep measurement by the disturbance control and gain calculation module, the coupling voltage amplitude of the coupling transformer under the operating frequency current of the measured power generation equipment due to short circuit can be calculated, that is, the fundamental response voltage amplitude.

[0023] In some embodiments, the step S20 of extracting the disturbance response voltage comprises: When the disturbance injection voltage is the disturbance voltage value corresponding to each frequency point of the pre-stored sweep point table, the output current detected by the output voltage and current detection unit is obtained, the output current is phase-locked by a phase-locked loop to obtain a fundamental phase angle, and the fundamental current coupling voltage under the current disturbance is calculated in combination with the fundamental response voltage amplitude; wherein the fundamental phase angle is a phase angle that changes with time, and the value of the fundamental current coupling voltage under the current disturbance is the product of the fundamental response voltage amplitude and the sine value of the fundamental phase angle. When the disturbance injection voltage is the disturbance voltage value corresponding to each frequency point of the pre-stored sweep point table, the voltage of the secondary winding of the coupling transformer detected by the disturbance detection unit is obtained, and the voltage of the primary winding of the coupling transformer is calculated as the coupling voltage under the current disturbance; wherein the value of the voltage of the primary winding of the coupling transformer can be obtained according to the turns ratio of the primary winding to the secondary winding of the coupling transformer in combination with the voltage of the secondary winding of the coupling transformer. The difference between the coupling voltage under the current disturbance and the fundamental current coupling voltage under the current disturbance is calculated as the disturbance response voltage, and the disturbance response voltage is extracted.

[0024] It should be noted that the phase-locked loop is a control circuit that makes the phase and frequency of the output signal of the circuit accurately follow the phase and frequency of the input reference signal.

[0025] Of course, in other embodiments, the extraction of the disturbance response voltage in the step S20 is: The disturbance signal harmonic processing technology is adopted to analyze the voltage of the secondary winding of the coupling transformer obtained by the disturbance detection unit in real time through Fourier transform, and the disturbance response voltage is directly extracted.

[0026] S30: The disturbance control and gain calculation module calculates the disturbance gain according to the disturbance injection voltage and the disturbance response voltage.

[0027] Specifically, in some embodiments, when the disturbance control and gain calculation module is in a disturbance closed-loop control mode, the calculation of the disturbance gain in the step S30 includes: The disturbance feedback voltage is obtained by negative feedback through the voltage loop combined with the PI control algorithm according to the disturbance response voltage and the disturbance injection voltage, and the actual disturbance voltage is calculated by using the PID adjustment algorithm; wherein the PID adjustment algorithm includes three parts of proportion (Proportional), integral (Integral) and differential (Differential); the voltage loop is a closed-loop feedback structure in a control system with voltage as the control target, and the PI control (Proportional-Integral Control) algorithm is the core algorithm for realizing the closed-loop adjustment.

[0028] The ratio of the disturbance injection voltage to the actual disturbance voltage is calculated to obtain the closed-loop disturbance gain.

[0029] Of course, in other embodiments, when the disturbance control and gain calculation module is in a disturbance open-loop control mode, the calculation of the disturbance gain in the step S30 is specifically: The ratio of the voltage of the secondary winding of the coupling transformer to the disturbance injection voltage is calculated to obtain the open-loop disturbance gain.

[0030] S40: The disturbance control and gain calculation module is used to compare the disturbance gain with the preset early warning gain threshold and the preset risk gain threshold respectively, and adjust and control the disturbance injection according to the comparison result.

[0031] Preferably, the step S40 specifically comprises: The disturbance control and gain calculation module is used to determine whether the disturbance gain is greater than the preset early warning gain threshold, and when the disturbance gain is greater than the preset early warning gain threshold, an early warning control signal for prompting entering the resonance band early warning is output, and the disturbance injection voltage is amplitude-reduced by the amplitude reduction coefficient. The disturbance control and gain calculation module is used to determine whether the disturbance gain is greater than the preset risk gain threshold, and when the disturbance gain is greater than the preset risk gain threshold, a warning control signal for prompting the resonance risk warning is output, the injection of the disturbance injection voltage is stopped, and the sweep frequency measurement is ended; when the disturbance gain is not greater than the preset risk gain threshold, it is determined whether there is a next frequency point in the pre-stored sweep frequency point table, and when there is no next frequency point in the pre-stored sweep frequency point table, the sweep frequency measurement is ended.

[0032] The preset risk gain threshold is greater than the preset early warning gain threshold. The wideband impedance sweep frequency measurement method injects disturbance into the power grid by using disturbance coupling, so that the wideband impedance measurement device only needs to bear the disturbance part response power, which can reduce the body capacity requirement of the wideband impedance measurement device, realize application in high-voltage high-power system, meet the fine requirement of impedance characteristic measurement of power generation equipment in new energy power generation base, have high adaptability, and can also reduce the influence of the wideband impedance measurement device on the fundamental wave of the power grid, realize high-precision disturbance measurement, and moreover, by setting the disturbance control and gain calculation module to sample the voltage of the secondary winding of the coupling transformer and calculate and analyze the disturbance gain, the resonance band is pre-judged and avoided by comparing the disturbance gain with the preset early warning gain threshold and the preset risk gain threshold, the resonance band risk is effectively avoided, and the measurement accuracy and system safety are ensured.

[0033] Specifically, after the disturbance control and gain calculation module determines whether the disturbance gain is greater than the preset early warning gain threshold, the method further comprises: When the disturbance gain is not greater than the preset early warning gain threshold, it is determined whether there is a next frequency point in the pre-stored sweep frequency point table, and when there is no next frequency point in the pre-stored sweep frequency point table, the sweep frequency measurement is ended.

[0034] After the determination of whether there is a next frequency point in the pre-stored sweep frequency point table, the method further comprises: When there is a next frequency point in the pre-stored sweep frequency point table, the steps S10-S40 are continuously executed.

[0035] Figure 3 And Figure 4The simulation waveforms of the voltage detected by the disturbance detection unit and the disturbance gain when continuously and automatically sweeping frequency by using the traditional impedance measurement method and the wideband impedance sweep measurement method of the present application are shown respectively, Figure 3 and Figure 4 In the above, the abscissa is time, the unit is s, the curve of the upper half of the graph is the simulation waveform of the disturbance gain, the dotted part of the lower half of the graph is the disturbance frequency, and the black part is the disturbance response. Figure 3 As shown in the above, the disturbance fixed amplitude is set to 200V, the frequency starts from 50Hz and continuously increases at a rate of 100Hz / s to the 10kV measured power equipment, as shown in the above, when the disturbance frequency increases to about 1010Hz, the disturbance gain rapidly rises to 3.0, indicating that the harmonic response current of the measured power equipment at this point is large. Figure 4 As shown in the above, the disturbance fixed amplitude is set to 200V, the frequency starts from 50Hz and continuously increases at a rate of 100Hz / s to the 10kV measured power equipment, when the disturbance frequency increases to about 960Hz, the resonance band early warning is triggered, the disturbance amplitude is reduced, so the disturbance gain curve shows the second last peak, when the disturbance frequency increases to about 990Hz, the resonance risk warning is triggered, the disturbance injection voltage is reduced to 0, avoiding system collapse caused by disturbance, showing the last peak.

[0036] In summary, the wideband impedance measurement device of the present application is electrically connected between the power grid and the measured power equipment, the wideband impedance measurement device includes a main path input switch, a disturbance control and gain calculation module, a main path output switch and a number of single-phase measurement units equal to the number of electrical phases of the power grid, each single-phase measurement unit is connected to the corresponding electrical phase of the power grid through the main path input switch, the single-phase measurement unit is connected to the measured power equipment through the main path output switch, the single-phase measurement unit includes a wideband disturbance generator, an output filter unit, a coupling transformer, a disturbance detection unit, a bypass switch and an output voltage and current detection unit, the disturbance is injected into the power grid by using the disturbance coupling mode, the main power loop is connected to the power grid, so that the wideband impedance measurement device only needs to bear the response power of the disturbance part, which can reduce the capacity requirement of the wideband impedance measurement device, realize the application in high-voltage high-power system, meet the fine requirements of impedance characteristic measurement of power equipment in new energy power generation base, have high adaptability, can reduce the influence of the wideband impedance measurement device on the fundamental wave of the power grid, realize high-precision disturbance measurement, and the disturbance control and gain calculation module is arranged to sample the voltage of the secondary winding of the coupling transformer and calculate and analyze the disturbance gain, the resonance band is pre-judged and avoided by comparing the disturbance gain with the preset early warning gain threshold and the preset risk gain threshold, the resonance band risk is effectively avoided, and the measurement accuracy and system safety are ensured. The wideband impedance sweep measurement method of the present application also has the above functions.

[0037] The above merely illustrates the specific embodiments of the present application, but the protection scope of the present application is not limited thereto, and any skilled person in the art can easily think of various equivalent modifications or replacements within the technical range disclosed by the present application, and these modifications or replacements shall be covered within the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.

Claims

1. A broadband impedance measurement device, characterized in that, Electrically connected between the power grid and the power generation equipment under test, the broadband impedance measurement device includes a main input switch, a disturbance control and gain calculation module, a main output switch, and single-phase measurement units equal in number to the power grid phases. Each single-phase measurement unit is connected to the corresponding power grid phase through the main input switch and to the power generation equipment under test through the main output switch. Each single-phase measurement unit includes a broadband disturbance generator, an output filter unit, a coupling transformer, a disturbance detection unit, a bypass switch, and an output voltage and current detection unit. The output voltage and current detection unit is connected to the power generation equipment under test through the bypass switch. After being switched off, the main input switch is connected to the corresponding power grid phase. The output voltage and current detection unit is connected to the tested power generation equipment through the main output switch. The disturbance control and gain calculation module is connected to the disturbance detection unit, the output voltage and current detection unit, and the broadband disturbance generator. The broadband disturbance generator is connected to the primary winding of the coupling transformer through the output filter unit. The secondary winding of the coupling transformer is connected to the bypass switch. The disturbance detection unit is connected in parallel with the bypass switch. The disturbance detection unit is electrically connected between the two ends of the secondary winding of the coupling transformer.

2. The broadband impedance measuring device according to claim 1, characterized in that, The output filtering unit includes an inductor and a capacitor. One end of the output terminal of the broadband disturbance generator is connected to the first end of the primary winding of the coupling transformer and the first end of the capacitor via the inductor. The other end of the output terminal of the broadband disturbance generator is connected to the second end of the primary winding of the coupling transformer and the second end of the capacitor.

3. The broadband impedance measuring device according to claim 1, characterized in that, The broadband disturbance generator includes a bidirectional rectifier and a frequency inverter.

4. The broadband impedance measuring device according to claim 1, characterized in that, The coupling transformer is a three-phase four-core wideband coupling transformer, and the disturbance detection unit is a voltage transformer used to detect the voltage of the secondary winding of the coupling transformer.

5. A broadband impedance sweep frequency measurement method, characterized in that, Applied to the broadband impedance measurement device as described in any one of claims 1-4, the broadband impedance sweep frequency measurement method includes the following steps: The disturbance control and gain calculation module reads the pre-stored frequency sweep point table, sets the disturbance injection voltage according to the disturbance voltage value corresponding to each frequency point in the pre-stored frequency sweep point table, and uses the wideband disturbance generator to perform disturbance injection operation on the power grid. The disturbance control and gain calculation module extracts the disturbance response voltage based on the voltage of the secondary winding of the coupling transformer detected by the disturbance detection unit. The disturbance control and gain calculation module is used to calculate the disturbance gain based on the disturbance injection voltage and the disturbance response voltage; The disturbance control and gain calculation module compares the disturbance gain with the preset early warning gain threshold and the preset risk gain threshold respectively, and performs disturbance injection adjustment control based on the comparison results.

6. The broadband impedance sweep frequency measurement method according to claim 5, characterized in that, Before the disturbance control and gain calculation module extracts the disturbance response voltage based on the voltage of the secondary winding of the coupling transformer detected by the disturbance detection unit, the wideband impedance sweep frequency measurement method further includes: The disturbance control and gain calculation module initially sets the disturbance injection voltage to 0. When the disturbance injection voltage is 0, the voltage of the secondary winding of the coupling transformer detected by the disturbance detection unit is obtained as the fundamental response voltage amplitude, and the fundamental response voltage amplitude is stored.

7. The broadband impedance sweep frequency measurement method according to claim 6, characterized in that, The extraction of the disturbance response voltage includes: When the disturbance injection voltage is the disturbance voltage value corresponding to each frequency point in the pre-stored frequency sweep point table, the output current detected by the output voltage and current detection unit is obtained, and the output current is phase-locked to the fundamental wave through the phase-locked loop to obtain the fundamental wave phase angle. Combined with the fundamental wave response voltage amplitude, the fundamental wave current coupling voltage under the current disturbance is calculated. When the disturbance injection voltage is the disturbance voltage value corresponding to each frequency point in the pre-stored frequency sweep point table, the voltage of the secondary winding of the coupling transformer detected by the disturbance detection unit is obtained, and the voltage of the primary winding of the coupling transformer is calculated as the coupling voltage under the current disturbance. The difference between the coupling voltage under the current disturbance and the coupling voltage of the fundamental current under the current disturbance is calculated as the disturbance response voltage, and the disturbance response voltage is extracted.

8. The broadband impedance sweep frequency measurement method according to claim 5, characterized in that, When the disturbance control and gain calculation module is in the disturbance closed-loop control mode, the calculation of disturbance gain includes: The disturbance feedback voltage is obtained by negative feedback through a voltage loop combined with a PI control algorithm based on the disturbance response voltage and the disturbance injection voltage. The actual disturbance voltage is then calculated using a PID adjustment algorithm on the disturbance feedback voltage. Calculate the ratio of the injected disturbance voltage to the actual disturbance voltage to obtain the closed-loop disturbance gain.

9. The broadband impedance sweep frequency measurement method according to claim 5, characterized in that, When the disturbance control and gain calculation module is in the disturbance open-loop control mode, the calculation of the disturbance gain is specifically as follows: Calculate the ratio of the voltage on the secondary winding of the coupling transformer to the disturbance injection voltage to obtain the open-loop disturbance gain.

10. The broadband impedance sweep frequency measurement method according to claim 5, characterized in that, The disturbance control and gain calculation module compares the disturbance gain with a preset early warning gain threshold and a preset risk gain threshold, respectively, and performs disturbance injection adjustment control based on the comparison results, including: The disturbance control and gain calculation module is used to determine whether the disturbance gain is greater than the preset warning gain threshold. When the disturbance gain is greater than the preset warning gain threshold, a warning control signal is output to indicate that the resonant band has been entered. The disturbance injection voltage is reduced by a reduction factor. The disturbance control and gain calculation module determines whether the disturbance gain is greater than the preset risk gain threshold. When the disturbance gain is greater than the preset risk gain threshold, a warning control signal is output to indicate the resonance risk warning, the injection of disturbance injection voltage is stopped and the frequency sweep measurement ends. When the disturbance gain is not greater than the preset risk gain threshold, it is determined whether there is a next frequency point in the pre-stored frequency sweep point table. When there is no next frequency point in the pre-stored frequency sweep point table, the frequency sweep measurement ends.

Images