Method and device for measuring broadband impedance of power grid by switching impedance

Abstract

The invention provides a method and a device for measuring broadband impedance of a power grid by switching impedance, and the method comprises the steps: generating broadband disturbance signals corresponding to a plurality of frequency points in a to-be-measured frequency band according to the to-be-measured frequency band; according to the broadband disturbance signal, switching an impedance device to a power grid by controlling the on-off of a switching device, and exciting harmonic voltage and harmonic current corresponding to each frequency point in the power grid; extracting harmonic voltage and harmonic current of each frequency point from the voltage and current of the power grid; and determining an impedance value of each frequency point according to the harmonic voltage and the harmonic current of each frequency point. According to the measurement method provided by the invention, the broadband impedance of the power grid can be measured more accurately.

Description

Technical Field

[0001] The present invention relates to the technical field of power system impedance measurement, and in particular to a method and device for measuring wide-band impedance of a power grid by switching impedance. Background Art

[0002] With the increasing penetration of renewable energy into the power grid, the proportion of power electronic equipment in the power system has increased annually. This has significantly altered the structure and operational characteristics of the power system. Wideband oscillations have become a major challenge threatening the safe and stable operation of the power system. When power electronic equipment is connected to a weak grid, its interaction with the grid's impedance characteristics can easily trigger wideband oscillations of 2Hz-2kHz, causing equipment disconnection and torsional vibration of the shaft system of thermal power plants, seriously impacting the ability to absorb renewable energy.

[0003] Broadband oscillations arise from the dynamic interaction between power electronics and the grid's impedance characteristics. The impedance characteristics of renewable energy converters interact with those of the grid, potentially forming a negatively damped resonant circuit. Impedance analysis is a fundamental method for assessing the risk of broadband oscillations associated with renewable energy grid integration. This requires obtaining a broadband impedance curve for the grid's impedance.

[0004] Although the traditional swept frequency method can achieve impedance measurement, its measurement method of multiple single-frequency injections takes up to several hours and cannot capture the true impedance characteristics of the system under dynamic changes. Summary of the Invention

[0005] The present invention provides a method and device for measuring the broadband impedance of a power grid by switching impedance, which can more accurately measure the broadband impedance of the power grid.

[0006] According to a first aspect of an embodiment of the present invention, a method for measuring a wideband impedance of a power grid by switching impedance is provided, the method comprising:

[0007] Generate broadband disturbance signals corresponding to multiple frequency points in the frequency band to be measured according to the frequency band to be measured;

[0008] According to the broadband disturbance signal, the impedance device is switched to the power grid by controlling the on and off of the switching device, thereby exciting the corresponding harmonic voltage and harmonic current at each frequency point in the power grid;

[0009] Extract the harmonic voltage and harmonic current at each frequency point from the voltage and current of the power grid respectively;

[0010] According to the harmonic voltage and harmonic current at each frequency point, the impedance value at each frequency point is determined.

[0011] In a possible implementation, generating broadband disturbance signals corresponding to multiple frequency points in the frequency band to be measured according to the frequency band to be measured includes:

[0012] Determine a frequency point set to be measured according to the frequency band to be measured, where the frequency point set to be measured includes multiple frequency points in the frequency band to be measured;

[0013] A phase adjustment algorithm is used to determine the phase angle corresponding to each frequency point, wherein the phase angle corresponding to each frequency point is not exactly the same;

[0014] Based on each frequency point and its corresponding phase angle, a modulation signal generation algorithm is used to generate a broadband disturbance signal.

[0015] In one possible implementation, a phase adjustment algorithm is used to determine the phase angle corresponding to each frequency point, including: calculating the phase angle corresponding to each frequency point using the following formula:

[0016]

[0017] The value is the starting phase, N is the number of frequency points, Represents the phase angle of the i-th frequency point.

[0018] In one possible implementation, a modulation signal generation algorithm is used based on each frequency point and its corresponding phase angle to generate a broadband disturbance signal, including:

[0019] The broadband disturbance signal is calculated using the following formula:

[0020]

[0021] Among them, S(t) represents the broadband disturbance signal, t represents time, K0, K i are all constants, f i represents the frequency of the i-th frequency point, represents the phase angle of the i-th frequency point;

[0022] After being modulated according to the broadband disturbance signal, the harmonics are input into a harmonic generation circuit connected to the power grid; wherein the harmonic generation circuit includes at least a switching device and an impedance device.

[0023] In a possible implementation, extracting the harmonic voltage and harmonic current at each frequency point from the voltage and current of the power grid includes:

[0024] Collect the voltage and current of the power grid;

[0025] The harmonic voltage and harmonic current at each frequency point are extracted from the voltage and current respectively.

[0026] According to a second aspect of an embodiment of the present invention, a device for measuring a wideband impedance of a power grid by switching impedance is provided, the device comprising:

[0027] A control module is used to generate a broadband disturbance signal corresponding to multiple frequency points in the frequency band to be measured according to the frequency band to be measured; and is also used to control the on and off of the switching device according to the broadband disturbance signal;

[0028] The harmonic generation circuit is used to respond to the broadband disturbance signal and switch the impedance device to the power grid by switching the switch device on and off, thereby exciting the corresponding harmonic voltage and harmonic current at each frequency point in the power grid;

[0029] Sampling module, used to collect voltage and current of the power grid;

[0030] The control module is further used to extract the harmonic voltage and harmonic current at each frequency point from the voltage and current respectively; and is further used to determine the impedance value of each frequency point of the power grid based on the harmonic voltage and harmonic current.

[0031] In one possible implementation, the harmonic generation circuit includes a first switching device, a second switching device, and a first impedance device;

[0032] The anode of the first switching device is connected to one of the three phases of the power grid, the cathode of the first switching device is connected to the cathode of the second switching device, the anode of the second switching device is connected to one end of the first impedance device, and the other end of the first impedance device is grounded;

[0033] Alternatively, one end of the first impedance device is connected to one of the three phases of the power grid, the other end of the first impedance device is connected to the anode of the first switching device, the cathode of the first switching device is connected to the cathode of the second switching device, and the anode of the second switching device is grounded;

[0034] Wherein, the gates of the first switching device and the second switching device are both connected to the control module.

[0035] In a possible implementation, the harmonic generation circuit further includes a second impedance device;

[0036] One end of the second impedance device is connected to the anode of the first switching device, and the other end of the second impedance device is connected to the anode of the second switching device.

[0037] In one possible implementation, the harmonic generation circuit includes a third switching device, a bridge rectifier circuit, and a third impedance device;

[0038] The cathode of the third switching device is connected to the first DC output terminal of the bridge rectifier circuit, the anode of the third switching device is connected to one end of the third impedance device, the other end of the third impedance device is connected to the second DC output terminal of the bridge rectifier circuit, one AC input terminal of the bridge rectifier circuit is connected to one of the three phases of the power grid, and the other AC input terminal of the bridge rectifier circuit is grounded;

[0039] Alternatively, a cathode of the third switching device is connected to one end of the third impedance device, the other end of the third impedance device is connected to the first DC output end of the bridge rectifier circuit, and an anode of the third switching device is connected to the second DC output end of the bridge rectifier circuit; an AC input end of the bridge rectifier circuit is connected to one of the three phases of the power grid, and the other AC input end of the bridge rectifier circuit is grounded;

[0040] Alternatively, the cathode of the third switching device is connected to the first DC output terminal of the bridge rectifier circuit, and the anode of the third switching device is connected to the second DC output terminal of the bridge rectifier circuit; one AC input terminal of the bridge rectifier circuit is connected to one of the three phases of the power grid, and the other AC input terminal is connected to one end of the third impedance device, and the other end of the third impedance device is grounded;

[0041] Alternatively, the cathode of the third switching device is connected to the first DC output terminal of the bridge rectifier circuit, and the anode of the third switching device is connected to the second DC output terminal of the bridge rectifier circuit; one AC input terminal of the bridge rectifier circuit is connected to one end of the third impedance device, the other end of the third impedance device is grounded, and the other AC input terminal of the bridge rectifier circuit is connected to one phase of the three phases of the power grid;

[0042] The gate of the third switching device is connected to the control module; the connection point of the anodes of the two diodes in the bridge rectifier circuit serves as the first DC output terminal, and the connection point of the cathodes of the two diodes serves as the second DC output terminal.

[0043] In a possible implementation, the harmonic generating circuit further includes a fourth impedance device;

[0044] Two ends of the fourth impedance device are respectively connected to an AC input end of the bridge rectifier circuit.

[0045] The embodiment of the present invention provides a method and device for measuring the broadband impedance of a power grid by switching impedance. According to the frequency band to be measured, a broadband disturbance signal corresponding to multiple frequency points in the frequency band to be measured is generated; according to the broadband disturbance signal, the impedance device is switched to the power grid by controlling the on and off of the switching device, thereby stimulating the corresponding harmonic voltage and harmonic current at each frequency point in the power grid; the harmonic voltage and harmonic current at each frequency point are extracted from the voltage and current of the power grid respectively; and the impedance value at each frequency point is determined based on the harmonic voltage and harmonic current at each frequency point. Based on the broadband disturbance signal at multiple frequency points in the broadband power grid, the on and off of the switching device is controlled, and the impedance device is switched between two states: connecting to the power grid and disconnecting from the power grid. When connecting to the power grid, the impedance device absorbs the power grid's electrical energy, and when disconnecting from the power grid, the impedance device stops absorbing the power grid's electrical energy. This achieves the simultaneous stimulation of harmonics at multiple frequency points in the power grid, thereby simultaneously measuring the impedance of the power grid at multiple frequency points and more accurately measuring the broadband impedance of the power grid. Moreover, harmonics can be stimulated in the power grid without connecting to an additional power supply, thereby reducing hardware costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are merely embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying any creative work.

[0047] Figure 1 A schematic flow chart of a method for measuring wide-band impedance of a power grid by switching impedance provided by an embodiment of the present invention;

[0048] Figure 2 A comparison chart of the measured values and actual values obtained by using the measurement method provided by the present invention for simulation testing;

[0049] Figure 3 A schematic structural diagram of a power grid wideband impedance measurement device by switching impedance provided by an embodiment of the present invention;

[0050] Figure 4 A schematic structural diagram of a harmonic generation circuit provided by an embodiment of the present invention;

[0051] Figure 5 A schematic structural diagram of another harmonic generation circuit provided by an embodiment of the present invention;

[0052] Figure 6 A schematic structural diagram of another harmonic generation circuit provided by an embodiment of the present invention;

[0053] Figure 7 A schematic structural diagram of another harmonic generation circuit provided by an embodiment of the present invention; DETAILED DESCRIPTION

[0054] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0055] An embodiment of the present invention provides a method for measuring wide-band impedance of a power grid by switching impedance, which can be applied to electronic equipment and specifically executed by hardware or software in the electronic equipment.

[0056] The following describes the method for measuring the broadband impedance of a power grid by switching impedance provided by an embodiment of the present invention, taking an electronic device as an example of an execution subject. Figure 1 As shown, the measurement method may include the following steps:

[0057] S110 , generating, according to the frequency band to be measured, broadband disturbance signals corresponding to a plurality of frequency points in the frequency band to be measured.

[0058] The frequency band to be measured indicates the frequency range in which the grid impedance needs to be measured and is set by the measurement personnel.

[0059] According to the frequency band to be measured, a set of N discrete frequency points to be measured is generated [f1, f2, ... f i …f N ], f i Indicates the i-th frequency point. The interval between frequency points is set by the measurement personnel as needed.

[0060] In one example, the measurement interval is set to 1 Hz, the starting measurement frequency is 1 Hz, and the frequency band to be measured is 1 Hz-2000 Hz. Then the set of frequency points to be measured is [1 Hz, 2 Hz, 3 Hz, ..., 2000 Hz], including 2000 frequency points.

[0061] Then, a broadband disturbance signal corresponding to each frequency point in the frequency band to be measured is generated.

[0062] In one example, the generated broadband disturbance signal includes disturbance signals of 2000 frequencies, namely [1 Hz, 2 Hz, 3 Hz, ..., 2000 Hz].

[0063] A broadband disturbance signal is input into a harmonic generation circuit connected to a power grid, wherein the harmonic generation circuit comprises at least a switching device and an impedance device.

[0064] S120 , according to the broadband disturbance signal, the impedance device is switched to the power grid by controlling the on and off of the switching device, thereby exciting the corresponding harmonic voltage and harmonic current at each frequency point in the power grid.

[0065] Three harmonic generation circuits are connected to one of the three phases of the power grid, each comprising at least a switching device and an impedance device. Based on a broadband disturbance signal, the switching devices in the harmonic generation circuits are periodically turned on and off, switching the impedance devices between grid-connected and grid-disconnected states. When connected, the impedance devices absorb grid energy, while when disconnected, they cease absorbing grid energy. This allows the simultaneous generation of harmonics at multiple frequencies in the grid.

[0066] S130 , extracting the harmonic voltage and harmonic current at each frequency point from the voltage and current of the power grid respectively.

[0067] Collect the voltage V of the power grid respectively abc and current I abc , respectively, from the voltage V abc and current I abc Extract the harmonic voltage V at each frequency point abc (f i ) and harmonic current I abc (f i ).

[0068] S140 , determining an impedance value at each frequency point according to the harmonic voltage and harmonic current at each frequency point.

[0069] The impedance value at each frequency point is calculated using the following formula:

[0070]

[0071] Z(f i ) represents the frequency point f i impedance value.

[0072] After obtaining the impedance value at each frequency point, the following steps may also be included:

[0073] S150 , generating a broadband impedance characteristic curve based on the calculated impedance value of the power grid at each frequency point and the phase angle of the broadband disturbance signal at each frequency point.

[0074] Figure 2 This is a comparison chart obtained through simulation measurement. The horizontal axis is the frequency of the frequency point, and the vertical axis is the amplitude of the impedance value of the power grid at each frequency point and the phase angle of the harmonic corresponding to each frequency point. It can be seen from the figure that the measured values are basically consistent with the actual values.

[0075] An embodiment of the present invention provides a method for measuring the broadband impedance of a power grid by switching impedance. According to the frequency band to be measured, a broadband disturbance signal corresponding to multiple frequency points in the frequency band to be measured is generated. Based on the broadband disturbance signal at multiple frequency points in the broadband band of the power grid, the on-off of a switching device is controlled, and the impedance device is switched between two states: connected to the power grid and cut off from the power grid. When connected to the power grid, the device absorbs the power energy of the power grid, and when cut off from the power grid, the device stops absorbing the power energy of the power grid. This achieves the simultaneous excitation of harmonics at multiple frequency points in the power grid, thereby simultaneously measuring the impedance of the power grid at multiple frequency points, and more accurately measuring the broadband impedance of the power grid. Moreover, harmonics can be excited in the power grid without connecting to an additional power supply, thereby reducing hardware costs.

[0076] In one embodiment, S110: generating, according to the frequency band to be measured, broadband disturbance signals corresponding to multiple frequency points in the frequency band to be measured, may include the following steps:

[0077] S111 : Determine a frequency point set to be measured according to a frequency band to be measured, where the frequency point set to be measured includes a plurality of frequency points in the frequency band to be measured.

[0078] According to the frequency band to be measured, a set of N discrete frequency points to be measured is generated [f1, f2, ... f i …f N ], f i Indicates the i-th frequency point. The interval between frequency points is set by the measurement personnel as needed.

[0079] In an example, the measurement interval is set to 1 Hz, the starting measurement frequency is 1 Hz, and the frequency band to be measured is 1 Hz-2000 Hz. Then the set of frequency points to be measured is [1 Hz, 2 Hz, 3 Hz, ..., 2000 Hz], and the frequency points are: 1 Hz, 2 Hz, 3 Hz, ..., 2000 Hz, for a total of 2000 frequency points.

[0080] S112: Using a phase adjustment algorithm, determine the phase angle corresponding to each frequency point, wherein the phase angle corresponding to each frequency point is not completely the same.

[0081] In one example, the phase angle corresponding to each frequency point is calculated using the following formula:

[0082]

[0083] The value is the starting phase, N is the number of frequency points, Represents the phase angle of the i-th frequency point.

[0084] Adjust the phase of each frequency point so that the phase angle corresponding to each frequency point is not exactly the same. In this way, the phase of the harmonic amplitude corresponding to each frequency point is not exactly the same, avoiding the superposition of the harmonic amplitudes corresponding to multiple frequency points at the same phase to cause a higher harmonic amplitude, thereby avoiding affecting the normal operation of the power grid.

[0085] S113 , based on each frequency point and its corresponding phase angle, a modulation signal generation algorithm is used to generate a broadband disturbance signal.

[0086] The broadband disturbance signal can be calculated using the following formula:

[0087]

[0088] Among them, S(t) represents the broadband disturbance signal, t represents time, K0, K i are all constants, f i represents the frequency of the i-th frequency point, represents the phase angle of the i-th frequency point;

[0089] In one example, K0 takes a value of 0.5, K i The value is 0.02.

[0090] Then, after being modulated according to the broadband disturbance signal, the signal is input into a harmonic generation circuit connected to the power grid; wherein the harmonic generation circuit includes at least one switching device and at least one impedance device harmonic generation circuit.

[0091] Pulse width modulation (PWM) and other modulation techniques may be used to modulate the broadband disturbance signal to generate a driving signal to drive the harmonic generation circuit.

[0092] The measurement method provided in an embodiment of the present invention adjusts the phase angle corresponding to each frequency point, generates a broadband disturbance signal based on each frequency point and its corresponding phase angle, and after modulation, inputs the signal into a harmonic generation circuit, thereby controlling the on and off of a switching device, switching the impedance device between two states: connecting to the power grid and disconnecting from the power grid, and simultaneously exciting harmonics of multiple frequency points in the power grid, while avoiding the adverse effects of high harmonic amplitudes on the power grid.

[0093] In one embodiment, S130: extracting the harmonic voltage and harmonic current at each frequency point from the voltage and current of the power grid respectively may include the following steps:

[0094] S131, collecting the voltage and current of the power grid.

[0095] S132, extracting the harmonic voltage and harmonic current at each frequency point from the voltage and current respectively.

[0096] In one example, a Fourier decomposition algorithm is applied to the voltage and current of the power grid respectively to extract the harmonic voltage at each frequency point in the voltage and to extract the harmonic current at each frequency point in the current.

[0097] The method provided by the embodiment of the present invention simultaneously extracts harmonics at multiple frequency points from the power grid, thereby improving measurement efficiency.

[0098] The embodiment of the present invention also provides a wide-band impedance measurement device for a power grid by switching impedance, such as Figure 3 As shown, the new energy unit is connected to the grid through the busbar, Z line The impedance of the power grid line is represented by a wide-band impedance measurement device 300 connected to the power grid through a switching impedance. The measurement device 300 may include a control module 310, a harmonic generation circuit 320, and a sampling module 330, wherein:

[0099] The control module 310 is used to generate a broadband disturbance signal corresponding to multiple frequency points in the frequency band to be measured according to the frequency band to be measured; and is also used to control the on and off of the switching device according to the broadband disturbance signal;

[0100] The harmonic generation circuit 320 is used to respond to the broadband disturbance signal and switch the impedance device to the power grid by switching the switch device on and off, thereby exciting the corresponding harmonic voltage and harmonic current at each frequency point in the power grid.

[0101] Each of the three phases of the power grid is connected to a harmonic generating circuit 320. Figure 3 Only one of the harmonic generating circuits is shown as an example.

[0102] The sampling module 330 is used to collect the voltage and current of the power grid.

[0103] The control module 320 is further configured to extract the harmonic voltage and harmonic current at each frequency point from the voltage and the current respectively; and to determine the impedance value of each frequency point of the power grid based on the harmonic voltage and harmonic current.

[0104] An embodiment of the present invention provides a wide-band impedance measurement device for a power grid by switching impedance. According to the frequency band to be measured, a wide-band disturbance signal corresponding to multiple frequency points in the frequency band to be measured is generated. Based on the wide-band disturbance signal of multiple frequencies, the on-off of a switching device in a harmonic generation circuit is controlled, and the impedance device is switched between two states: connected to the power grid and cut off from the power grid. When connected to the power grid, the device absorbs the power energy of the power grid, and when cut off from the power grid, the device stops absorbing the power energy of the power grid. This achieves the simultaneous excitation of harmonics at multiple frequency points in the power grid, thereby simultaneously measuring the impedance of the power grid at multiple frequency points, and more accurately measuring the wide-band impedance of the power grid. Moreover, harmonics can be excited in the power grid without connecting to an additional power supply, thereby reducing hardware costs.

[0105] In one embodiment, the control module 310 may include a phase adjustment unit 311, a signal generation unit 312, and an extraction and calculation unit 313, wherein:

[0106] The phase adjustment unit 311 is configured to determine a set of frequency points to be measured based on the frequency band to be measured, where the set of frequency points to be measured includes multiple frequency points in the frequency band to be measured; and further configured to determine a phase angle corresponding to each frequency point using a phase adjustment algorithm, where the phase angles corresponding to the various frequency points are not identical.

[0107] Specifically, the phase angle corresponding to each frequency point is calculated using the following formula:

[0108]

[0109] The value is the starting phase, N is the number of frequency points, Represents the phase angle of the i-th frequency point.

[0110] The signal generating unit 312 is configured to generate a broadband disturbance signal based on each frequency point and its corresponding phase angle by adopting a modulation signal generating algorithm.

[0111] Specifically, the broadband disturbance signal is calculated using the following formula:

[0112]

[0113] Among them, S(t) represents the broadband disturbance signal, t represents time, K0, K i are all constants, f i represents the frequency of the i-th frequency point, represents the phase angle of the i-th frequency point;

[0114] After being modulated according to the broadband disturbance signal, it is input into the harmonic generation circuit.

[0115] The switching device may include an insulated gate bipolar transistor (IGBT), etc., which is a switching tube controlled by PWM.

[0116] In one example, the switching device includes an IGBT and a diode connected in reverse parallel to the IGBT, and the gate, anode, and cathode of the IGBT serve as the gate, anode, and cathode of the switching device, respectively.

[0117] The broadband disturbance signal is modulated by PWM or other modulation techniques to generate a driving signal to drive the harmonic generation circuit.

[0118] The extraction and calculation unit 313 is used to collect the voltage and current of the power grid; it is also used to extract the harmonic voltage and harmonic current of each frequency point from the voltage and current respectively; it is also used to determine the impedance value of each frequency point based on the harmonic voltage and harmonic current of each frequency point.

[0119] The measuring device provided by the embodiment of the present invention adjusts the phase angle corresponding to each frequency point, generates a broadband disturbance signal based on each frequency point and its corresponding phase angle, and inputs the signal into the harmonic generation circuit after modulation, thereby controlling the on and off of the switching device, switching the impedance device between the two states of connecting to the power grid and disconnecting from the power grid, and simultaneously exciting harmonics of multiple frequency points in the power grid, while avoiding the adverse effects of high harmonic amplitudes on the power grid; and simultaneously extracting harmonics of multiple frequency points from the power grid, thereby improving measurement efficiency.

[0120] In one embodiment, Figure 4 As shown, the harmonic generating circuit 320 includes a first switching device Q1 , a second switching device Q2 , and a first impedance device Z1 .

[0121] The gates of Q1 and Q2 are both connected to the control module.

[0122] In one example, Q1 and Q2 each include an IGBT and a diode connected in reverse parallel to the IGBT, and the gate, anode, and cathode of the IGBTs constituting Q1 and Q2 serve as the gate, anode, and cathode of Q1 and Q2, respectively.

[0123] The anode of Q1 is connected to one of the three phases of the power grid, the cathode of Q1 is connected to the cathode of Q2, the anode of Q2 is connected to one end of Z1, and the other end of Z1 is grounded.

[0124] Alternatively, one end of Z1 is connected to one of the three phases of the power grid, the other end of Z1 is connected to the anode of Q1, the cathode of Q1 is connected to the cathode of Q2, and the anode of Q2 is grounded.

[0125] In one example, Z1 is an adjustable impedance device. The greater the impedance of Z1, the greater the peak value of the harmonics excited in the power grid. The measurement personnel can flexibly adjust the impedance of the first impedance device based on needs, thereby adjusting the peak value of the harmonics.

[0126] The broadband disturbance signal controls Q1 and Q2 to be turned on and off periodically, and switches Z1 to the grid periodically, thereby exciting the corresponding harmonic voltage and harmonic current at each frequency point in the grid.

[0127] In one example, if Figure 5 As shown, the harmonic generating circuit further includes a second impedance device Z2;

[0128] One end of Z2 is connected to the anode of Q1, and the other end of Z2 is connected to the anode of Q2.

[0129] Z2 may be an adjustable impedance device.

[0130] Z2 in the harmonic generation circuit can reduce the voltage across the switching device and reduce the requirements on the performance of the switching device.

[0131] The harmonic generating circuit provided in the embodiment of the present invention does not require an external power supply, and changes the current flowing into the harmonic generating circuit by switching impedance, thereby exciting harmonics corresponding to multiple frequency points on the grid side.

[0132] In one embodiment, Figure 6 As shown, the harmonic generating circuit includes a third switching device Q3, a bridge rectifier circuit and a third impedance device Z3;

[0133] Among them, the gate of Q3 is connected to the control module; the bridge rectifier circuit includes a diode D1, a diode D2, a diode D3, and a diode D4, the anode connection point of D1 and D2 serves as the first DC output terminal -1, the cathode connection point of D3 and D4 serves as the second DC output terminal -2, and the cathode connection point of D1 and the anode connection point of D3, and the cathode connection point of D2 and the anode connection point of D4 both serve as AC input terminals.

[0134] In one example, Q3 includes an IGBT and a diode connected in reverse parallel to the IGBT, and the gate, anode, and cathode of the IGBT serve as the gate, anode, and cathode of Q3 respectively.

[0135] The cathode of Q3 is connected to the first DC output terminal of the bridge rectifier circuit, the anode of Q3 is connected to one end of Z3, the other end of Z3 is connected to the second DC output terminal of the bridge rectifier circuit, an AC input terminal of the bridge rectifier circuit is connected to one of the three phases of the power grid, and the other AC input terminal of the bridge rectifier circuit is grounded.

[0136] Alternatively, the cathode of Q3 is connected to one end of Z3, the other end of Z3 is connected to the first DC output end of the bridge rectifier circuit, and the anode of Q3 is connected to the second DC output end of the bridge rectifier circuit; an AC input end of the bridge rectifier circuit is connected to one of the three phases of the power grid, and the other AC input end of the bridge rectifier circuit is grounded.

[0137] Alternatively, the cathode of Q3 is connected to the first DC output terminal of the bridge rectifier circuit, and the anode of Q3 is connected to the second DC output terminal of the bridge rectifier circuit; one AC input terminal of the bridge rectifier circuit is connected to one of the three phases of the power grid, and the other AC input terminal is connected to one end of Z3, and the other end of Z3 is grounded;

[0138] Alternatively, the cathode of Q3 is connected to the first DC output terminal of the bridge rectifier circuit, and the anode of Q3 is connected to the second DC output terminal of the bridge rectifier circuit; an AC input terminal of the bridge rectifier circuit is connected to one end of Z3, the other end of Z3 is grounded, and the other AC input terminal of the bridge rectifier circuit is connected to one phase of the three phases of the power grid.

[0139] In one example, Z3 is an adjustable impedance device. The greater the impedance of Z3, the greater the peak value of the harmonics excited in the power grid. The measurement personnel can flexibly adjust the impedance of the third impedance device based on needs, thereby adjusting the peak value of the harmonics.

[0140] The broadband disturbance signal controls Q3 to be turned on and off periodically, and switches Z3 to the grid periodically, thereby exciting the corresponding harmonic voltage and harmonic current at each frequency point in the grid.

[0141] In one example, if Figure 7 As shown, the harmonic generation circuit further includes a fourth impedance device Z4, and both ends of Z4 are respectively connected to an AC input end of the bridge rectifier circuit.

[0142] Z4 may be an adjustable impedance device.

[0143] Z4 in the harmonic generation circuit can reduce the voltage across the switching device and reduce the requirements on the performance of the switching device.

[0144] The harmonic generating circuit provided in the embodiment of the present invention does not require an external power supply, and changes the current flowing into the harmonic generating circuit by switching impedance, thereby exciting harmonics corresponding to multiple frequency points on the grid side.

[0145] The harmonic generating circuits in the above embodiments are illustrative only. Any harmonic generating circuit topology that can switch impedance to the power grid by controlling the switching devices to be periodically turned on and off falls within the protection scope of the present invention.

[0146] The wideband impedance measurement device for a power grid using switching impedances provided in this embodiment is based on the same inventive concept as the wideband impedance measurement method for a power grid using switching impedances provided in the aforementioned embodiments of the present invention. It can implement the wideband impedance measurement method for a power grid using switching impedances provided in any of the aforementioned embodiments of the present invention and possesses the functional modules and beneficial effects corresponding to the wideband impedance measurement method for a power grid using switching impedances. For technical details not fully described in this embodiment, please refer to the specific processing details of the wideband impedance measurement method for a power grid using switching impedances provided in the aforementioned embodiments of the present invention and will not be further elaborated here.

[0147] An embodiment of the present invention also provides a grid broadband impedance measurement system through switching impedance. The measurement system includes: a grid broadband impedance measurement device through switching impedance, a grid and a new energy generator set. The new energy generator set is connected to the grid through a busbar and is connected to the grid through the grid broadband impedance measurement device through switching impedance.

[0148] The device for measuring the wide-band impedance of a power grid by switching impedance is described in the above embodiment and will not be described in detail here.

[0149] In addition, an embodiment of the present invention further provides a storage medium having computer program instructions stored thereon, and the computer program instructions are used by a processor to execute the steps of the method for measuring wide-band impedance of a power grid by switching impedance in various embodiments of the present invention described above in this specification.

[0150] An embodiment of the present invention further provides a computer program product comprising computer program instructions. When the instructions in the computer program product are executed by a processor of an electronic device, the electronic device executes the steps of the method for measuring the wide-band impedance of a power grid by switching impedance in various embodiments of the present invention described above in this specification.

[0151] The computer program product may be written in any combination of one or more programming languages to implement the operations of embodiments of the present invention, including object-oriented programming languages such as Java, C++, and conventional procedural programming languages such as C or similar programming languages. The program code may be executed entirely on the user's computing device, partially on the user's computing device, as a stand-alone software package, partially on the user's computing device and partially on a remote computing device, or entirely on a remote computing device or server.

[0152] For simplicity of description, the aforementioned method embodiments are described as a series of actions. However, those skilled in the art should be aware that the present invention is not limited by the order of the actions described, as certain steps can be performed in other orders or simultaneously according to the present invention. Furthermore, those skilled in the art should also be aware that the embodiments described in this specification are preferred embodiments, and the actions and modules involved are not necessarily required for the present invention.

[0153] It should be noted that the various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. Similarities between the various embodiments can be referred to in conjunction with each other. For device embodiments, since they are generally similar to method embodiments, their description is relatively simple, and for relevant details, reference can be made to the description of the method embodiments.

[0154] The steps in the methods of the various embodiments of the present invention can be adjusted in sequence, combined, and deleted according to actual needs, and the technical features recorded in the various embodiments can be replaced or combined.

[0155] The modules and submodules in the devices and terminals of various embodiments of the present invention may be combined, divided, or deleted according to actual needs.

[0156] In the several embodiments provided herein, it should be understood that the disclosed terminals, devices, and methods can be implemented in other ways. For example, the terminal embodiments described above are merely illustrative. For example, the division of modules or submodules is merely a logical functional division. In actual implementation, other division methods may be used, such as combining or integrating multiple submodules or modules into another module, or omitting or not implementing certain features. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be an indirect coupling or communication connection between devices or modules via some interface, which may be electrical, mechanical, or other forms.

[0157] The modules or submodules described as separate components may or may not be physically separate, and the components of the modules or submodules may or may not be physical modules or submodules, that is, they may be located in one place or distributed across multiple network modules or submodules. Some or all of the modules or submodules may be selected to achieve the purpose of this embodiment according to actual needs.

[0158] In addition, the functional modules or submodules in the various embodiments of the present invention may be integrated into a single processing module, or each module or submodule may exist physically separately, or two or more modules or submodules may be integrated into a single module. The aforementioned integrated modules or submodules may be implemented in the form of hardware or software functional modules or submodules.

[0159] Professionals may further appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of the two. In order to clearly illustrate the interchangeability of hardware and software, the above description has generally described the components and steps of each example according to their functions. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professionals and technicians may use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of the present invention.

[0160] The steps of the methods or algorithms described in conjunction with the embodiments disclosed herein may be implemented directly using hardware, software units executed by a processor, or a combination of the two. The software units may be placed in random access memory (RAM), internal memory, read-only memory (ROM), electrically programmable ROM, electrically erasable programmable ROM, registers, hard disk, removable disk, CD-ROM, or any other form of storage medium known in the art.

[0161] Finally, it should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or device comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or elements inherent to such process, method, article, or device. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of additional identical elements in the process, method, article, or device comprising the element.

[0162] The above description of the disclosed embodiments will enable one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for measuring the broadband impedance of a power grid by switching impedance, characterized in that: The measuring method comprises: generating, according to the frequency band to be measured, broadband disturbance signals corresponding to a plurality of frequency points in the frequency band to be measured; According to the broadband disturbance signal, the impedance device is switched to the power grid by controlling the on and off of the switching device, thereby exciting the corresponding harmonic voltage and harmonic current at each frequency point in the power grid; Extract the harmonic voltage and harmonic current at each frequency point from the voltage and current of the power grid respectively; The impedance value at each frequency point is determined according to the harmonic voltage and the harmonic current at each frequency point.

2. The measuring method according to claim 1, wherein The step of generating, according to the frequency band to be measured, broadband disturbance signals corresponding to a plurality of frequency points in the frequency band to be measured comprises: Determining a frequency point set to be measured according to the frequency band to be measured, where the frequency point set to be measured includes a plurality of frequency points in the frequency band to be measured; A phase adjustment algorithm is used to determine the phase angle corresponding to each frequency point, wherein the phase angle corresponding to each frequency point is not exactly the same; Based on each frequency point and its corresponding phase angle, a modulation signal generation algorithm is used to generate a broadband disturbance signal.

3. The measuring method according to claim 2, characterized in that The phase adjustment algorithm is used to determine the phase angle corresponding to each frequency point, including: using the following formula to calculate the phase angle corresponding to each frequency point: The value is the starting phase, N is the number of frequency points, Represents the phase angle of the i-th frequency point.

4. The measuring method according to claim 2, characterized in that The method of generating a broadband disturbance signal by using a modulation signal generation algorithm based on each frequency point and its corresponding phase angle includes: The broadband disturbance signal is calculated using the following formula: Among them, S(t) represents the broadband disturbance signal, t represents time, K0, K i are all constants, f i represents the frequency of the i-th frequency point, represents the phase angle of the i-th frequency point; After being modulated according to the broadband disturbance signal, the signal is input into a harmonic generation circuit connected to the power grid; wherein the harmonic generation circuit at least includes the switching device and the impedance device.

5. The measuring method according to claim 1, wherein: Extracting the harmonic voltage and harmonic current at each frequency point from the voltage and current of the power grid includes: collecting the voltage and current of the power grid; The harmonic voltage and harmonic current at each frequency point are extracted from the voltage and the current respectively.

6. A device for measuring the broadband impedance of a power grid by switching impedance, characterized in that: The measuring device comprises: A control module, configured to generate, according to a frequency band to be measured, a broadband disturbance signal corresponding to a plurality of frequency points in the frequency band to be measured; and further configured to control the on and off of a switching device according to the broadband disturbance signal; A harmonic generation circuit is configured to respond to the broadband disturbance signal and switch an impedance device to the power grid by switching a switching device on and off, thereby stimulating a corresponding harmonic voltage and harmonic current at each frequency point in the power grid; A sampling module, used for collecting the voltage and current of the power grid; The control module is further configured to extract the harmonic voltage and harmonic current at each frequency point from the voltage and the current respectively; and is further configured to determine the impedance value at each frequency point of the power grid based on the harmonic voltage and harmonic current.

7. The measuring device according to claim 6, characterized in that The harmonic generating circuit includes a first switching device, a second switching device and a first impedance device; The anode of the first switching device is connected to one of the three phases of the power grid, the cathode of the first switching device is connected to the cathode of the second switching device, the anode of the second switching device is connected to one end of the first impedance device, and the other end of the first impedance device is grounded; Alternatively, one end of the first impedance device is connected to one of the three phases of the power grid, the other end of the first impedance device is connected to the anode of the first switching device, the cathode of the first switching device is connected to the cathode of the second switching device, and the anode of the second switching device is grounded; Wherein, the gates of the first switching device and the second switching device are both connected to the control module.

8. The measuring device according to claim 7, characterized in that The harmonic generating circuit further includes a second impedance device; One end of the second impedance device is connected to the anode of the first switching device, and the other end of the second impedance device is connected to the anode of the second switching device.

9. The measuring device according to claim 6, characterized in that The harmonic generating circuit includes a third switching device, a bridge rectifier circuit and a third impedance device; The cathode of the third switching device is connected to the first DC output terminal of the bridge rectifier circuit, the anode of the third switching device is connected to one end of the third impedance device, the other end of the third impedance device is connected to the second DC output terminal of the bridge rectifier circuit, one AC input terminal of the bridge rectifier circuit is connected to one of the three phases of the power grid, and the other AC input terminal of the bridge rectifier circuit is grounded; Alternatively, a cathode of the third switching device is connected to one end of the third impedance device, the other end of the third impedance device is connected to the first DC output end of the bridge rectifier circuit, and an anode of the third switching device is connected to the second DC output end of the bridge rectifier circuit; an AC input end of the bridge rectifier circuit is connected to one of the three phases of the power grid, and the other AC input end of the bridge rectifier circuit is grounded; Alternatively, the cathode of the third switching device is connected to the first DC output terminal of the bridge rectifier circuit, and the anode of the third switching device is connected to the second DC output terminal of the bridge rectifier circuit; one AC input terminal of the bridge rectifier circuit is connected to one of the three phases of the power grid, and the other AC input terminal is connected to one end of the third impedance device, and the other end of the third impedance device is grounded; Alternatively, the cathode of the third switching device is connected to the first DC output terminal of the bridge rectifier circuit, and the anode of the third switching device is connected to the second DC output terminal of the bridge rectifier circuit; one AC input terminal of the bridge rectifier circuit is connected to one end of the third impedance device, the other end of the third impedance device is grounded, and the other AC input terminal of the bridge rectifier circuit is connected to one phase of the three phases of the power grid; The gate of the third switching device is connected to the control module; the connection point of the anodes of the two diodes in the bridge rectifier circuit serves as the first DC output end, and the connection point of the cathodes of the two diodes serves as the second DC output end.

10. The measuring device according to claim 9, characterized in that The harmonic generating circuit further includes a fourth impedance device; Two ends of the fourth impedance device are respectively connected to an AC input end of the bridge rectifier circuit.

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