Inverter control method and device, impedance measurement method and device, and power grid system

Abstract

The invention relates to an inverter control method and device, an impedance measurement method and device and a power grid system, and relates to the technical field of power electronics. The inverter control method comprises the following steps: respectively acquiring a grid-connected point current of a grid-connected point in a power grid system, a real-time phase of a grid-connected point voltage and a disturbance phase; the grid-connected point is a connection point of the inverter and the power distribution network; performing current separation processing on the grid-connected point current according to the real-time phase and the disturbance phase, and obtaining a fundamental current and a disturbance current; performing disturbance control processing on the disturbance current according to the disturbance phase, obtaining a disturbance modulation voltage reference instruction, performing fundamental wave control processing on the fundamental wave current according to the real-time phase, and obtaining a fundamental wave modulation voltage reference instruction; and generating a driving signal for driving the inverter according to the disturbance modulation voltage reference instruction and the fundamental wave modulation voltage reference instruction. According to the invention, accurate control of injection disturbance can be realized, and the problem of too large disturbance or insufficient disturbance is avoided.

Description

Technical Field

[0001] The present application relates to the field of power electronics technology, and particularly to an inverter control method and device, an impedance measurement method and device, and a power grid system. Background Art

[0002] With the advancement of the construction of new distribution networks, a large number of power electronic devices such as distributed photovoltaic power generation, distributed wind power generation, and distributed energy storage devices are connected to the distribution network. The penetration rate of power electronic devices in the distribution network increases year by year, and the stability problems and harmonic over-standard problems caused by power electronic devices become increasingly prominent. As an important parameter for stability analysis and harmonic responsibility division, the impedance of the distribution network and the connected power electronic devices is crucial to accurately obtain.

[0003] Considering the characteristics of the large-scale access and flexible control of power electronics, based on the transformation of the control strategy of the inverter of the power electronic device, the corresponding power electronic device can be controlled to inject a disturbance into the measured power grid system, so as to carry out broadband impedance parameter measurement of the distribution network, and apply the obtained parameters to fields such as harmonic responsibility division and power quality governance of the distribution network.

[0004] In the existing disturbance control strategy, generally, a disturbance command is added to the modulation loop or current loop, and a disturbance is injected into the measured power grid system through the disturbance command to realize the impedance measurement of the distribution network. However, the existing disturbance control strategy cannot achieve precise control of the injected disturbance, and it is easy to cause problems such as excessive disturbance or insufficient disturbance during actual measurement. Summary of the Invention

[0005] Based on this, in view of the above technical problems, it is necessary to provide an inverter control method and device, an impedance measurement method and device, and a power grid system, which can achieve precise control of the injected disturbance and avoid problems such as over-disturbance or under-disturbance.

[0006] The present application provides an inverter control method, which is applied to an inverter in a power grid system, and the power grid system further includes a distribution network connected to the inverter; the method includes:

[0007] Obtain the real-time phases of the grid connection point current and grid connection point voltage, and the disturbance phase in the power grid system respectively; the grid connection point is the connection point between the inverter and the distribution network;

[0008] Perform current separation processing on the grid connection point current according to the real-time phase and the disturbance phase, and obtain the fundamental current and the disturbance current;

[0009] Perform disturbance control processing on the disturbance current according to the disturbance phase, and obtain a disturbance modulation voltage reference command, and perform fundamental control processing on the fundamental current according to the real-time phase, and obtain a fundamental modulation voltage reference command;

[0010] Generate a driving signal for driving the inverter according to the disturbance modulation voltage reference instruction and the fundamental wave modulation voltage reference instruction.

[0011] In one embodiment, the grid connection point current, the fundamental wave current, and the disturbance current are respectively currents in a three-phase coordinate system; wherein, the current separation process is performed on the grid connection point current according to the real-time phase and the disturbance phase, and the fundamental wave current and the disturbance current are obtained, including:

[0012] Perform Park transformation processing and filtering processing on the grid connection point current according to the real-time phase, and obtain two-phase fundamental wave currents;

[0013] Perform inverse Park transformation processing on the two-phase fundamental wave currents according to the real-time phase, and obtain the fundamental wave current;

[0014] Perform Park transformation processing and filtering processing on the grid connection point current according to the disturbance phase, and obtain two-phase disturbance currents;

[0015] Perform inverse Park transformation processing on the two-phase disturbance currents according to the disturbance phase, and obtain the disturbance current.

[0016] In one embodiment, the disturbance control process is performed on the disturbance current according to the disturbance phase, and the disturbance modulation voltage reference instruction is obtained, including:

[0017] Obtain the reference amplitude of the disturbance current;

[0018] Obtain a disturbance current reference instruction according to the reference amplitude of the disturbance current and the disturbance phase;

[0019] Perform proportional-resonant control processing on the disturbance current and the disturbance current reference instruction, and obtain the disturbance modulation voltage reference instruction.

[0020] In one embodiment, the proportional frequency adjustment is performed on the disturbance current and the disturbance current reference instruction, and the disturbance modulation voltage reference instruction is obtained, including:

[0021] Obtain the disturbance current difference between the disturbance current and the disturbance current reference instruction;

[0022] Perform proportional-resonant control processing on the disturbance current difference according to the disturbance frequency, and obtain the disturbance modulation voltage reference instruction.

[0023] In one embodiment, the grid connection point voltage is a three-phase grid connection point voltage; respectively obtaining the real-time phases of the grid connection point current and the grid connection point voltage of the power grid system, and the disturbance phase, including:

[0024] Obtain the grid connection point current, the grid connection point voltage, and the disturbance phase respectively;

[0025] Perform Clarke transformation processing and filtering processing on the grid connection point voltage, and obtain the two-phase grid connection point voltage;

[0026] Perform inverse Clarke transformation processing on the two-phase grid connection point voltage, and obtain the filtered grid connection point voltage;

[0027] Perform phase-locking processing on the filtered grid connection point voltage, and obtain the real-time phase.

[0028] The present application provides an impedance measurement method, which is applied to a power grid system. The power grid system includes an inverter and a distribution network, and the inverter is controlled by the method as described above; the method includes:

[0029] Obtain the grid connection point current, the grid connection point voltage, and the disturbance frequency of the grid connection point in the power grid system respectively; the grid connection point is the connection point between the inverter and the distribution network;

[0030] Perform phase-locking processing and filtering processing on the grid connection point voltage, and obtain the real-time phase of the grid connection point voltage and the filtered grid connection point voltage;

[0031] Perform current separation processing on the grid connection point current according to the real-time phase and the disturbance frequency, and obtain the disturbance current;

[0032] Determine the impedance of the distribution network according to the grid connection point voltage, the filtered grid connection point voltage, the disturbance current, and the disturbance frequency.

[0033] In one embodiment, the determining the impedance of the distribution network according to the grid connection point voltage, the filtered grid connection point voltage, the disturbance current, and the disturbance frequency includes:

[0034] Obtain the disturbance voltage according to the grid connection point voltage and the filtered grid connection point voltage;

[0035] Perform discrete Fourier transform and positive and negative sequence operation according to the disturbance voltage, the disturbance current, and the disturbance frequency, and obtain the positive and negative sequence currents and positive and negative sequence voltages corresponding to the disturbance frequency;

[0036] Determine the impedance of the distribution network according to the positive and negative sequence currents and the positive and negative sequence voltages.

[0037] The present application provides an inverter control device, which is applied to an inverter in a power grid system. The power grid system further includes a distribution network connected to the inverter; the device includes:

[0038] The first current separation unit is configured to respectively obtain the real-time phases of the grid connection point current and the grid connection point voltage at the grid connection point in the power grid system, as well as the disturbance phase, perform current separation processing on the grid connection point current according to the real-time phase and the disturbance phase, and obtain the fundamental current and the disturbance current; the grid connection point is the connection point between the inverter and the distribution network;

[0039] The disturbance control unit is configured to perform disturbance control processing on the disturbance current according to the disturbance phase, and obtain a disturbance modulation voltage reference command;

[0040] The fundamental control unit is configured to perform fundamental control processing on the fundamental current according to the real-time phase, and obtain a fundamental modulation voltage reference command;

[0041] The modulation unit is configured to generate a drive signal for driving the inverter according to the disturbance modulation voltage reference command and the fundamental modulation voltage reference command.

[0042] The present application provides an impedance measurement device applied to a power grid system. The power grid system includes an inverter and a distribution network, and the inverter is controlled by the method as described above; the device includes:

[0043] The phase-locked unit is configured to obtain the grid connection point voltage at the grid connection point in the power grid system, perform phase-locking processing and filtering processing on the grid connection point voltage, and obtain the real-time phase of the grid connection point voltage and the filtered grid connection point voltage;

[0044] The second current separation unit is configured to respectively obtain the grid connection point current and the disturbance frequency at the grid connection point in the power grid system, perform current separation processing on the grid connection point current according to the real-time phase and the disturbance frequency, and obtain the disturbance current;

[0045] The impedance measurement unit is configured to determine the impedance of the distribution network according to the grid connection point voltage, the filtered grid connection point voltage, the disturbance current, and the disturbance frequency.

[0046] The present application provides a power grid system. The system includes an inverter and a distribution network, and the system further includes the inverter control device as described above, and / or the impedance measurement device as described above.

[0047] The above inverter control method and device, impedance measurement method and device, and power grid system respectively obtain the real-time phases of the grid connection point current and grid connection point voltage in the power grid system, as well as the disturbance phase; the grid connection point is the connection point between the inverter and the distribution network; the grid connection point current is subjected to current separation processing according to the real-time phase and the disturbance phase, and the fundamental current and the disturbance current are obtained; the disturbance current is subjected to disturbance control processing according to the disturbance phase, and a disturbance modulation voltage reference command is obtained, and the fundamental current is subjected to fundamental control processing according to the real-time phase, and a fundamental modulation voltage reference command is obtained; a drive signal for driving the inverter is generated according to the disturbance modulation voltage reference command and the fundamental modulation voltage reference command. This method can separate the fundamental current and the disturbance current in the grid connection point current. Thus, it provides an input basis for subsequent independent fundamental control and disturbance control respectively. Moreover, on the basis of performing fundamental control on the fundamental current, by introducing a disturbance control strategy to separately perform disturbance control adjustment on the disturbance current, it not only realizes effective control of the fundamental current, but also realizes effective and accurate control of the disturbance current. Therefore, it can inject disturbances into the system as needed, avoid problems such as over-disturbance or insufficient disturbance, enable the inverter to have accurate fundamental control ability and disturbance control ability, and thus is conducive to carrying out impedance measurement of the distribution network; in addition, the disturbance injected in this application will not act on the fundamental control of the inverter in turn, avoiding the influence on the fundamental power control of the inverter and improving the reliability of the system; and this method does not require additional equipment, reducing costs. Description of the Drawings

[0048] Figure 1 It is a schematic structural diagram of a power grid system in an embodiment;

[0049] Figure 2 It is a schematic flowchart of an inverter control method in an embodiment;

[0050] Figure 3 It is a schematic flowchart of an inverter control method in another embodiment;

[0051] Figure 4 It is a schematic flowchart of the current separation process in an inverter control method in an embodiment;

[0052] Figure 5 It is a schematic flowchart of an inverter control method in yet another embodiment;

[0053] Figure 6 It is a schematic flowchart of the disturbance control process in an inverter control method in an embodiment;

[0054] Figure 7 It is a schematic flowchart of an inverter control method in still another embodiment;

[0055] Figure 8Schematic diagram of the phase-locked processing in the inverter control method in an embodiment;

[0056] Figure 9 Schematic diagram of the impedance measurement method in an embodiment;

[0057] Figure 10 Schematic diagram of the impedance measurement method in another embodiment;

[0058] Figure 11 Schematic diagram of the impedance calculation process in the impedance measurement method in an embodiment;

[0059] Figure 12 Structural block diagram of the inverter control device in an embodiment;

[0060] Figure 13 Schematic diagram of the structure of the power grid system in another embodiment;

[0061] Figure 14 Structural block diagram of the impedance measurement device in an embodiment;

[0062] Figure 15 Internal structure diagram of a computer device in an embodiment.

[0063] Description of reference numerals:

[0064] 10. Inverter; 11. Inverter bridge; 20. Distribution network; 30. Inverter control device; 31. First current separation unit; 311. Current separation unit; 32. Disturbance control unit; 321. Disturbance control loop; 33. Fundamental wave control unit; 331. Fundamental wave current control loop; 34. Modulation unit; 341. Modulation loop; 35. Phase-locked loop; 40. Impedance measurement device; 41. Phase-locked unit; 42. Second current separation unit; 43. Impedance measurement unit; 431. Signal processing unit; 432. Impedance calculation unit; 433. Impedance measurement result summary unit. Detailed implementation manners

[0065] In order to make the objectives, technical solutions and advantages of the present application clearer and more understandable, the present application will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0066] The inverter control method and device, and the impedance measurement method and device provided by the embodiments of the present application can be applied to a power grid system as shown in Figure 1 The power grid system includes an inverter 10 and a distribution network 20. Among them, the inverter 10 includes a DC-side power supply U dc , an inverter bridge 11 and a filter. Among them, the DC-side power supply U dcFor providing a DC voltage. The inverter bridge 11 is used to convert the DC voltage into AC voltages of various frequencies. The inverter bridge 11 may include a full-bridge inverter circuit. The filter may include an inductor L f1 , which is used to filter the AC voltage output by the inverter 10. The power distribution network 20 includes an equivalent resistance R g , an equivalent inductor L g , and an equivalent voltage source u g . The first end and the second end of the inverter bridge 11 are respectively connected to the DC-side power supply U dc . The midpoint of the bridge arm of the inverter bridge 11 is connected to the first end of the inductor L f1 . The second end of the inductor L f1 is connected to the equivalent resistance R g .

[0067] In one embodiment, as Figure 2 shown, an inverter control method is provided. Taking the inverter in the power grid system shown Figure 1 as an example, it includes the following S202 to S208.

[0068] S202: Respectively obtain the real-time phases of the grid connection point current, grid connection point voltage, and disturbance phase in the power grid system; the grid connection point is the connection point between the inverter and the power distribution network.

[0069] The grid connection point can be understood as the connection point between the power grid and distributed energy resources (such as solar photovoltaic systems, wind power generation systems, etc.). For example, in Figure 1 , the grid connection point can be understood as the connection point between the inverter 10 and the power distribution network 20, that is, the connection point between the inductor L f1 and the equivalent resistance R g . Among them, the grid connection point current i g refers to the current flowing through the grid connection point. The grid connection point voltage u PCC refers to the voltage measured at the grid connection point. The disturbance phase θ P can be understood as the phase of the disturbance signal to be injected into the power grid system.

[0070] In applications, the real-time phases θ g of the grid connection point current i PCC and the grid connection point voltage u PLL , as well as the disturbance frequency ω p , can be respectively obtained. Among them, the disturbance frequency ω p can be understood as the frequency of the disturbance signal to be injected into the power grid system. The disturbance frequency ω p can be set according to the disturbance injection requirement, which is not limited here. Based on this, the disturbance phase θ p can be obtained according to the disturbance frequency ω P, which can be expressed by the formula as θ P = ω p * t.

[0071] S204: Perform current separation processing on the grid - connection point current according to the real - time phase and the disturbance phase, and obtain the fundamental current and the disturbance current.

[0072] The fundamental current i g0 refers to the component with the same frequency as the power - grid power frequency in a periodic AC signal. In the embodiment of the present application, the fundamental current i g0 refers to the fundamental current component at the grid - connection point, which can be understood as the actual fundamental current i g0 at the grid - connection point. The disturbance current i p includes all current components with non - fundamental frequencies, including but not limited to harmonic currents, inter - harmonic currents, and transient currents, etc. In the embodiment of the present application, the disturbance current i p refers to the disturbance current component at the grid - connection point. For example, in the impedance measurement scenario, the disturbance current can be the actual disturbance current at the grid - connection point after injecting a disturbance into the power - grid system.

[0073] In the application, the grid - connection point current i PLL can be subjected to current separation processing according to the real - time phase θ P and the disturbance phase θ g , that is, the fundamental current i PLL is extracted from the grid - connection point current i g according to the real - time phase θ g0 , and the corresponding fundamental current i g0 is obtained. And the disturbance current i P is extracted from the grid - connection point current i g according to the disturbance phase θ p , and the corresponding disturbance current i p is obtained.

[0074] S206: Perform disturbance control processing on the disturbance current according to the disturbance phase, and obtain the disturbance modulation voltage reference instruction, and perform fundamental control processing on the fundamental current according to the real - time phase, and obtain the fundamental modulation voltage reference instruction.

[0075] The disturbance modulation voltage reference instruction m p is a reference value used to guide the subsequent voltage modulation of the disturbance signal. The disturbance modulation voltage reference instruction m p is intended to compensate for the difference between the actual disturbance and the set disturbance, and use the disturbance modulation voltage reference value as a reference basis for subsequent modulation processing, so that the disturbance injected by the inverter 10 into the power - grid system under the drive of the drive signal can be as close as possible to the set disturbance.

[0076] Since the disturbance current ip represents the actual disturbance current of the power grid system. Therefore, a preset disturbance current reference command can be obtained, and according to the disturbance current i p , the disturbance phase θ P and the disturbance current reference command are used for disturbance control adjustment, and a disturbance modulation voltage reference command m p is obtained to compensate for the difference between the disturbance current i p and the disturbance current reference command. Among them, the disturbance control process can be understood as performing error adjustment on the disturbance current i p and the disturbance current reference command.

[0077] The fundamental wave modulation voltage reference command m 0 is a reference value used to guide the subsequent voltage modulation of the fundamental wave signal. The fundamental wave modulation voltage reference command m 0 is designed to compensate for the difference between the actual fundamental wave and the set disturbance, and use the fundamental wave modulation voltage reference value as a reference for subsequent modulation processing, so that the inverter 10 can work as close as possible to the set fundamental wave under the drive of the drive signal.

[0078] In the application, a preset fundamental wave current reference command can be obtained, and according to the fundamental wave current i g0 , the real-time phase θ PLL and the fundamental wave current reference command are used for fundamental wave control adjustment, and a fundamental wave modulation voltage reference command m 0 is obtained to supplement the difference between the fundamental wave current i g0 and the fundamental wave current reference command. Among them, the fundamental wave control process can be understood as performing error adjustment on the fundamental wave current i g0 and the fundamental wave current reference command.

[0079] It should be noted that the control and adjustment process of the fundamental wave current i g0 can adopt control algorithms in related technologies. For example, a dq-axis current control strategy can be adopted, or a proportional-resonant (PR) control on the abc coordinate axes can be adopted, which will not be limited too much here.

[0080] S208: Generate a drive signal for driving the inverter 10 according to the disturbance modulation voltage reference command and the fundamental wave modulation voltage reference command.

[0081] The drive signal can be used to drive the inverter bridge 11 in the inverter 10. In the application, according to the disturbance modulation voltage reference command m p and the fundamental wave modulation voltage reference command m 0Perform modulation processing and generate a drive signal. Among them, the modulation processing method can be any suitable method in the related art. For example, pulse width modulation (PWM) can be adopted, such as space vector pulse width modulation (SVPWM) or sinusoidal pulse width modulation (SPWM), and no further limitation is made here.

[0082] For the inverter control method provided by the above embodiment, the grid connection point current i at the grid connection point in the power grid system is obtained respectively g , and the real-time phase θ of the grid connection point voltage PLL , and the disturbance phase θ P ; the grid connection point is the connection point between the inverter 10 and the distribution network 20; according to the real-time phase θ PLL and the disturbance phase θ P perform current separation processing on the grid connection point current i g and obtain the fundamental current i g0 and the disturbance current i p ; according to the disturbance phase θ P perform disturbance control processing on the disturbance current i p and obtain the disturbance modulation voltage reference command m p , and according to the real-time phase θ PLL perform fundamental wave control processing on the fundamental wave current and obtain the fundamental wave modulation voltage reference command m 0 ; according to the disturbance modulation voltage reference command m p and the fundamental wave modulation voltage reference command m 0 , generate a drive signal for driving the inverter 10. This method can separate the fundamental current i g and the disturbance current i g0 in the grid connection point current i p , thus providing an input basis for subsequent independent fundamental wave control and disturbance control respectively, and on the basis of performing fundamental wave control on the fundamental current i g0 , by introducing a disturbance control strategy to separately perform disturbance control adjustment on the disturbance current i p , not only the effective control of the fundamental current i g0 is realized, but also the effective control of the disturbance current i pEffective and precise control can inject disturbances into the system as needed, avoiding over-disturbance or insufficient disturbance problems, enabling the inverter 10 to have accurate fundamental wave control and disturbance control capabilities, which is beneficial to the impedance measurement of the distribution network 20. In addition, the disturbances injected in this application will not act on the fundamental wave control of the inverter, avoiding the impact on the fundamental wave power control of the inverter and improving the reliability of the system. Moreover, this method does not require additional equipment, reducing costs.

[0083] As Figure 3 and Figure 4 shown, in one embodiment, in S204, the grid-connected point current is processed for current separation according to the real-time phase and the disturbance phase, and the fundamental wave current and the disturbance current are obtained, including the following S302 to S308.

[0084] S302: Perform Park transformation and filtering on the grid-connected point current according to the real-time phase, and obtain two-phase fundamental wave currents.

[0085] S304: Perform inverse Park transformation on the two-phase fundamental wave currents according to the real-time phase, and obtain the fundamental wave current.

[0086] S306: Perform Park transformation and filtering on the grid-connected point current according to the disturbance phase, and obtain two-phase disturbance currents.

[0087] S308: Perform inverse Park transformation on the two-phase disturbance currents according to the disturbance phase, and obtain the disturbance current.

[0088] The grid-connected point current i g , the fundamental wave current i g0 and the disturbance current i p are respectively the currents in the three-phase coordinate system, i.e., the abc axis. The two-phase fundamental wave currents and the two-phase disturbance currents are respectively the currents in the two-phase coordinate system, i.e., the dq axis. Among them, the two-phase fundamental wave currents can include the d-axis fundamental wave current i g0d and the q-axis fundamental wave current i g0q . The two-phase disturbance currents can include the d-axis disturbance current i pd and the q-axis disturbance current i pq .

[0089] The Park transformation refers to the conversion from the three-phase coordinate system abc axis to the two-phase coordinate system dq axis. The inverse Park transformation is the inverse process of the Park transformation, that is, the conversion from the two-phase coordinate system dq axis to the three-phase coordinate system abc axis. The fundamental wave current i g0 is the current in the three-phase coordinate system.

[0090] In the application, as Figure 4 shown in the first channel, the grid-connected point current i PLL can be based on the real-time phase θ gThe Park transformation is performed, and after low-pass filtering, the fundamental current \(i_d\) on the d-axis is obtained g0d and the fundamental current \(i_q\) on the q-axis g0q . Thus, according to the real-time phase \(\theta\) PLL , the inverse Park transformation can be performed on the fundamental current \(i_d\) on the d-axis g0d and the fundamental current \(i_q\) on the q-axis g0q to obtain the fundamental current \(i_a\), \(i_b\), \(i_c\) in the three-phase coordinate system g0 .

[0091] Among them, the disturbance phase \(\theta\) P varies according to the different disturbance frequencies \(\omega\) p . The relationship between the disturbance phase \(\theta\) P and the disturbance frequency \(\omega\) p and time \(t\) can be \(\theta\) P = \(\omega\) p * \(t\). As shown in the second channel of Figure 4 , according to the disturbance phase \(\theta\) P , the Park transformation can be performed on the grid-connected point current \(i\) g , and after low-pass filtering, the disturbance current \(i_d\) on the d-axis is obtained pd and the disturbance current \(i_q\) on the q-axis pq . Thus, according to the disturbance phase \(\theta\) P , the inverse Park transformation can be performed on the disturbance current \(i_d\) on the d-axis pd and the disturbance current \(i_q\) on the q-axis pq to obtain the disturbance current \(i_a\), \(i_b\), \(i_c\) in the three-phase coordinate system p .

[0092] For the inverter control method provided by the above embodiment, according to the real-time phase \(\theta\) PLL , the Park transformation processing and filtering processing are performed on the grid-connected point current \(i\) g , and two-phase fundamental currents are obtained. According to the real-time phase \(\theta\) PLL , the inverse Park transformation processing is performed on the two-phase fundamental currents, and the fundamental current \(i_a\), \(i_b\), \(i_c\) is obtained g0 . According to the disturbance phase \(\theta\) P , the Park transformation processing and filtering processing are performed on the grid-connected point current \(i\) g , and two-phase disturbance currents are obtained. According to the disturbance phase \(\theta\) P , the inverse Park transformation processing is performed on the two-phase disturbance currents, and the disturbance current \(i_a\), \(i_b\), \(i_c\) is obtained p . This method realizes the separation and extraction of the fundamental current \(i_a\), \(i_b\), \(i_c\) g0 and the disturbance current \(i_a\), \(i_b\), \(i_c\) p through two channels of current separation, providing an input basis for subsequent fundamental current \(i_a\), \(i_b\), \(i_c\) g0 control and disturbance current \(i_a\), \(i_b\), \(i_c\) p control to achieve separate control of the fundamental current \(i_a\), \(i_b\), \(i_c\) g0 and the disturbance current \(i_a\), \(i_b\), \(i_c\) pIndependent and precise control can avoid problems such as over-perturbation or insufficient perturbation, enabling the inverter 10 to have accurate fundamental wave control ability and perturbation control ability, which helps to improve the accuracy of subsequent impedance measurement of the distribution network 20.

[0093] In one embodiment, as Figure 5 and Figure 6 shown, S206, perform perturbation control processing on the perturbation current according to the perturbation phase, and obtain the perturbation modulation voltage reference command, including the following S502 to S506.

[0094] S502: Obtain the reference amplitude of the perturbation current.

[0095] The reference amplitude I p of the perturbation current is preset and can be set accordingly according to the perturbation injection requirement, and will not be overly limited here.

[0096] S504: Obtain the perturbation current reference command according to the reference amplitude and phase of the perturbation current.

[0097] The perturbation current reference command is the reference value of the perturbation current in the three-phase coordinate system, including the reference command i pa_ref of the a-phase perturbation current, the reference command i pb_ref of the b-phase perturbation current, and the reference command i pc_ref of the c-phase perturbation current. In application, the perturbation current reference command can be obtained according to the reference amplitude I p of the perturbation current and the perturbation phase θ P , and can be expressed by the formula as:

[0098] (1)

[0099] S506: Perform proportional-resonant control processing according to the perturbation current and the perturbation current reference command, and obtain the perturbation modulation voltage reference command.

[0100] The perturbation current i p and the perturbation modulation voltage reference command m p are respectively currents in the three-phase coordinate system. Among them, the perturbation current i p includes the a-phase perturbation current i p_a , the b-phase perturbation current i p_b , and the c-phase perturbation current i p_c . The perturbation modulation voltage reference command m p includes the a-phase perturbation modulation voltage reference command m p_a , the b-phase perturbation modulation voltage reference command m p_b , and the c-phase perturbation modulation voltage reference command m p_c .

[0101] The resonant frequency ω in the proportional-resonant control processing processf is the same as the disturbance frequency ω p , that is, ω f = ω p . That is to say, the resonance frequency ω f varies with the set disturbance frequency ω p . In application, the disturbance current reference command can be compared with the disturbance current i p and proportional-resonant control processing is performed, or error adjustment is performed, so as to obtain the disturbance modulation voltage reference command m p .

[0102] Please continue to refer to Figure 6 , in one embodiment, S506, current adjustment processing is performed according to the disturbance current, the disturbance current reference amplitude, and the disturbance frequency to generate a disturbance modulation voltage reference command, including: obtaining the disturbance current difference between the disturbance current and the disturbance current reference command, performing proportional-resonant control processing on the disturbance current difference according to the disturbance frequency, and obtaining the disturbance modulation voltage reference command.

[0103] Based on the above, the disturbance current i p includes the a-phase disturbance current i p_a , the b-phase disturbance current i p_b , and the c-phase disturbance current i p_c . The disturbance current reference command i p_ref includes the a-phase disturbance current reference command i pa_ref , the b-phase disturbance current reference command i pb_ref , and the c-phase disturbance current reference command i pc_ref . In this regard, the a-phase disturbance current difference between the a-phase disturbance current i p_a and the a-phase disturbance current reference command i pa_ref can be obtained respectively, the b-phase disturbance current difference between the b-phase disturbance current i p_b and the b-phase disturbance current reference command i pb_ref , and the c-phase disturbance current difference between the c-phase disturbance current i p_c and the c-phase disturbance current reference command i pc_ref . The proportional-resonant control processing is performed on the a-phase disturbance current difference to obtain the a-phase disturbance modulation voltage reference command m p_a , the proportional-resonant control processing is performed on the b-phase disturbance current difference to obtain the b-phase disturbance modulation voltage reference command m p_b , and the proportional-resonant control processing is performed on the c-phase disturbance current difference to obtain the c-phase disturbance modulation voltage reference command m p_c . Thus, according to the a-phase disturbance modulation voltage reference command m p_a , the b-phase disturbance modulation voltage reference command m p_b , and the c-phase disturbance modulation voltage reference command m p_cObtain the disturbance modulation voltage reference command m p .

[0104] For the inverter control method provided in the above embodiment, obtain the disturbance current reference amplitude I p , and according to the disturbance current reference amplitude I p and the disturbance phase θ P obtain the disturbance current reference command i p_ref , and according to the disturbance current i p and the disturbance current reference command i p_ref perform proportional-resonant control processing, and obtain the disturbance modulation voltage reference command m p , so that the drive signal can be obtained through modulation processing according to the disturbance modulation voltage reference command m p to drive the inverter 10 to inject disturbances into the system, realizing precise control of the disturbance current, enabling the inverter 10 to have the disturbance control ability, and avoiding the problems of insufficient disturbance or over-disturbance. Further, this method obtains the disturbance current difference between the disturbance current i p and the disturbance current reference command i p_ref , and performs proportional-resonant control processing on the disturbance current difference according to the disturbance frequency ω p , and obtains the disturbance modulation voltage reference command m p . Thus, by comparing the disturbance current i p with the disturbance current reference command i p_ref and realizing error adjustment through proportional-resonant control, the subsequent modulation can be adjusted in the direction of the disturbance current reference command i p_ref . In this way, precise control of the disturbance current i p can be achieved, enabling the inverter 10 to have fundamental wave control performance and disturbance control performance, so that disturbances can be injected into the power grid system as needed, which is helpful for subsequent applications, such as impedance measurement of the distribution network 20, etc.

[0105] As Figure 7 and Figure 8 shown, in one embodiment, the grid-connected point voltage u PCC is a three-phase grid-connected point voltage. S202, respectively obtain the real-time phases of the grid-connected point current and grid-connected point voltage of the power grid system, and the disturbance phase, including the following S702 to S708.

[0106] S702: Respectively obtain the grid-connected point current, grid-connected point voltage and disturbance phase.

[0107] S704: Perform Clarke transformation processing and filtering processing on the grid-connected point voltage, and obtain the two-phase grid-connected point voltage.

[0108] S706: Perform inverse Clarke transformation processing on the two-phase grid-connected point voltage, and obtain the filtered grid-connected point voltage.

[0109] S708: Perform phase-locking processing on the filtered grid connection point voltage and obtain the real-time phase.

[0110] Grid connection point voltage u PCC is the grid connection point voltage in the three-phase coordinate system, i.e., the abc axes. The two-phase grid connection point voltage is the grid connection point voltage in the two-phase coordinate system, i.e., the αβ axes. Among them, the two-phase grid connection point voltage includes the α-axis grid connection point voltage u α and the β-axis grid connection point voltage .

[0111] The Clarke transformation refers to the transformation from the three-phase coordinate system, i.e., the abc axes, to the two-phase coordinate system, i.e., the αβ axes. The inverse Clarke transformation is the inverse process of the Clarke transformation, that is, the transformation from the two-phase coordinate system, i.e., the αβ axes, to the three-phase coordinate system, i.e., the abc axes.

[0112] In application, the grid connection point current i g , the grid connection point voltage u PCC and the disturbance phase θ P can be obtained respectively, and Clarke transformation processing is performed on the grid connection point voltage u PCC , that is, the grid connection point voltage u PCC under the abc axes of the three-phase coordinate system is converted into the α-axis grid connection point voltage u α and the β-axis grid connection point voltage under the αβ axes of the two-phase coordinate system. Then, filtering processing is performed on the α-axis grid connection point voltage u α and the β-axis grid connection point voltage respectively to obtain the filtered α-axis grid connection point voltage and the filtered β-axis grid connection point voltage , so as to obtain the filtered grid connection point voltage to filter out the disturbance voltage component formed during the impedance measurement process and prevent the disturbance voltage component from flowing into the control system of the inverter 10, affecting the control effect of the system fundamental wave current. Among them, the filtering processing process N(s) can be expressed by the formula as:

[0113] (2)

[0114] In the above formula, s is the Laplace operator. In application, the filtered α-axis grid connection point voltage and the filtered β-axis grid connection point voltage basically do not contain the disturbance voltage component and mainly contain the fundamental wave voltage component of the system.

[0115] Based on the above, the filtered α-axis grid connection point voltage and the filtered β-axis grid connection point voltage Perform the inverse Clarke transformation to obtain the grid connection point voltage mainly containing the fundamental voltage component, that is, the filtered grid connection point voltage. . Then, the filtered grid connection point voltage can be phase-locked, and the real-time phase θ of the grid connection point voltage can be obtained. PLL . Among them, the filtered grid connection point voltage can be used for impedance measurement of the distribution network 20, and the real-time phase θ PLL can be used to extract the disturbance current i p subsequently.

[0116] For the inverter control method provided in the above embodiment, the grid connection point current i g , the grid connection point voltage u PCC and the disturbance phase θ P are obtained respectively. The Clarke transformation processing and filtering processing are performed on the grid connection point voltage u PCC , and the two-phase grid connection point voltage is obtained. The inverse Clarke transformation processing is performed on the two-phase grid connection point voltage, and the filtered grid connection point voltage is obtained. The phase-locking processing is performed on the filtered grid connection point voltage , and the real-time phase θ PLL is obtained. In this way, the disturbance voltage component can be filtered out, the influence of the disturbance voltage component on the power grid system can be avoided, and it is helpful to improve the accuracy of subsequent impedance measurement.

[0117] In one embodiment, the embodiment of the present application provides an impedance measurement method, which can be applied to the power grid system as Figure 1 shown. The power grid system includes an inverter 10 and a distribution network 20. Among them, the inverter 10 can be controlled by using the inverter control method provided in the foregoing embodiment. For the relevant introduction of the power grid system, reference can be made to the foregoing content, which will not be elaborated here. As Figure 9 shown, this impedance measurement method includes the following S902 to S908.

[0118] S902: Respectively obtain the grid connection point current, grid connection point voltage and disturbance frequency at the grid connection point in the power grid system; the grid connection point is the connection point between the inverter and the distribution network.

[0119] S904: Perform phase-locking processing and filtering processing on the grid connection point voltage, and obtain the real-time phase of the grid connection point voltage and the filtered grid connection point voltage.

[0120] S906: Perform current separation processing according to the grid connection point current, real-time phase and disturbance frequency, and obtain the disturbance current.

[0121] S908: Determine the impedance of the distribution network according to the grid connection point voltage, the filtered grid connection point voltage, the disturbance current and the disturbance frequency.

[0122] Among them, S902 is similar to the aforementioned S202. For specific introduction, reference can be made to the content related to S202 above, which will not be elaborated here. S904 can be referred to Figure 7 and Figure 8 and related content, which will not be elaborated here. S906 is the same as the aforementioned S204. For specific introduction, reference can be made to the content related to S204 above, which will not be elaborated here.

[0123] The impedance of the distribution network 20 refers to the impedance of the distribution network 20 at the disturbance frequency ω p At this point. In application, the impedance of the distribution network 20 at the disturbance frequency ω can be determined according to the grid connection point voltage u PCC , the filtered grid connection point voltage , the disturbance current i p and the disturbance frequency ω p . p At this point.

[0124] For the impedance measurement method provided in the above embodiment, the grid connection point current i of the grid connection point in the power grid system is obtained respectively g , the grid connection point voltage u PCC and the disturbance frequency ω p ; the grid connection point is the connection point between the inverter 10 and the distribution network 20. The grid connection point voltage u PCC is subjected to phase-locked processing and filtering processing, and the real-time phase θ of the grid connection point voltage is obtained PLL and the filtered grid connection point voltage . According to the grid connection point current i g , the real-time phase θ PLL and the disturbance frequency ω p , current separation processing is performed, and the disturbance current i p is obtained. According to the grid connection point voltage u PCC , the filtered grid connection point voltage , the disturbance current i p and the disturbance frequency ω p , the impedance of the distribution network 20 is determined. In this way, on the basis of realizing the precise control of the injected disturbance, the impedance measurement of the distribution network 20 is realized, and the problems of excessive or insufficient disturbance during the measurement process are avoided, and the impedance measurement accuracy is improved.

[0125] In one embodiment, as shown in Figure 10 and Figure 11 , S908, determining the impedance of the distribution network 20 according to the grid connection point voltage, the filtered grid connection point voltage, the disturbance current and the disturbance frequency includes the following S1002 to S1006.

[0126] S1002: Obtain the disturbance voltage according to the grid connection point voltage and the filtered grid connection point voltage.

[0127] In the application, the grid connection point voltage u can be calculated. PCC and the filtered grid connection point voltage to obtain the voltage difference u PCC - , and this voltage difference is the disturbance voltage u p , that is, u p = u PCC - .

[0128] S1004: Perform discrete Fourier transform and positive and negative sequence operations based on the disturbance voltage, disturbance current, and disturbance frequency, and obtain the positive and negative sequence currents and positive and negative sequence voltages corresponding to the disturbance frequency.

[0129] The positive and negative sequence currents include the positive sequence current i gp (jω p ) and the negative sequence current i gn (jω p ), and the positive and negative sequence voltages include the positive sequence voltage U PCCp (jω p ) and the negative sequence voltage U PCCn (jω p ).

[0130] In the application, according to the disturbance frequency ω p , the disturbance voltage u p and the disturbance current i p can be respectively subjected to discrete Fourier (Discrete Fourier Transform, DFT) transform, and after positive and negative sequence operations, the positive sequence current i p at the injection disturbance frequency ω gp (jω p ), negative sequence current i gn (jω p ), positive sequence voltage U PCCp (jω p ) and negative sequence voltage U PCCn (jω p ) can be obtained.

[0131] S1006: Determine the impedance of the distribution network according to the positive and negative sequence currents and positive and negative sequence voltages.

[0132] The impedance of the distribution network 20 can include the positive sequence impedance Z gp (jω p ) and the negative sequence impedance Z gn (jω p ). In the application, according to the positive sequence current i gp (jω p ) and the positive sequence voltage U PCCp (jω p ), the impedance of the distribution network 20 at the disturbance frequency ωp Positive sequence impedance Z at gp (jω p ), and according to the negative sequence current i gn (jω p ) and negative sequence voltage U PCCn (jω p ) to determine the negative sequence impedance Z p of the distribution network 20 at the disturbance frequency ω gn (jω p ). The calculation process can be described as follows:

[0133] (3)

[0134] In the application, multiple measurements can be performed for different disturbance frequencies ω p Each measurement only obtains the positive sequence impedance Z gp (jω p ) and the negative sequence impedance Z gn (jω p ) at a single frequency point, and the results of each measurement can be stored, and the corresponding disturbance frequency ω p label and positive and negative sequence impedance labels are provided to prevent the impedances obtained from different measurement processes from being confused, making the measurement results worthless. At the same time, the impedance measurement data can also be exported. In this way, the broadband impedance of the distribution network 20 can be obtained, providing data support for harmonic responsibility division and power quality governance of the distribution network 20 in the power grid system.

[0135] It should be understood that although each of the above embodiments involved in the flowchart is displayed in sequence according to the arrow indication, these are not necessarily executed in the order indicated by the arrow. Unless there is a clear indication in this article, the execution of these does not have a strict order limit, and these can be executed in other orders. Moreover, at least a part of the flowchart involved in each of the above embodiments may include multiple or multiple stages, and these or stages are not necessarily executed at the same time, but can be executed at different times, and the execution order of these or stages is not necessarily sequential, but can be rotated or alternated with at least a part of other or other or stages among these or stages.

[0136] Based on the same inventive concept, the embodiment of the present application also provides an inverter control device for implementing the above-mentioned disturbance control method. The implementation solution provided by this device to solve the problem is similar to the implementation solution described in the above method. Therefore, the specific limitations in one or more of the following inverter control device embodiments can refer to the limitations on the disturbance control method in the above text, and will not be repeated here.

[0137] In one embodiment, as Figure 12As shown, an inverter control device 30 is provided, which can be applied to a power grid system as shown in Figure 1 The power grid system includes an inverter 10 and a distribution network 20. Among them, the inverter control device 30 includes a first current separation unit 31, a disturbance control unit 32, a fundamental wave control unit 33, and a modulation unit 34.

[0138] The first current separation unit 31 is used to respectively obtain the grid connection point current i of the grid connection point in the power grid system g , the real-time phase θ of the grid connection point voltage PLL , and the disturbance phase θ P . According to the real-time phase θ PLL and the disturbance phase θ P , the grid connection point current i is subjected to current separation processing g , and the fundamental wave current i is obtained g0 and the disturbance current i p ; the grid connection point is the connection point between the inverter 10 and the distribution network 20. The disturbance control unit 32 is used to perform disturbance control processing on the disturbance current i according to the disturbance phase θ P , and obtain the disturbance modulation voltage reference instruction m p . Exemplarily, the disturbance control unit 32 may include a disturbance control loop 321. The fundamental wave control unit 33 is used to perform fundamental wave control processing on the fundamental wave current i according to the real-time phase θ p , and obtain the fundamental wave modulation voltage reference instruction m PLL . Exemplarily, the fundamental wave control unit 33 may include a fundamental wave current control loop 331. The modulation unit 34 is used to generate a drive signal for driving the inverter 10 according to the disturbance modulation voltage reference instruction m g0 and the fundamental wave modulation voltage reference instruction m 0 . Exemplarily, the modulation unit 34 may include a modulation loop 341. p and the fundamental wave modulation voltage reference instruction m 0 .

[0139] In one embodiment, as shown in Figure 4 and Figure 13 , the grid connection point current i g , the fundamental wave current i g0 and the disturbance current i p are respectively currents in the three-phase coordinate system. Among them, the first current separation unit 31 includes a first channel and a second channel. Both the first channel and the second channel include an abc / dq transformation sub-unit, a low-pass filtering sub-unit, and a da / abc transformation sub-unit. In the first channel, the abc / dq transformation sub-unit is used to perform abc / dq transformation on the grid connection point current i according to the real-time phase θ PLL gPerform Park transformation processing; the low-pass filter subunit is used to filter the grid-connected point current after Park transformation processing and obtain two-phase fundamental currents; the dq / abc transformation subunit is used to perform inverse Park transformation processing on the two-phase fundamental currents according to the real-time phase θ PLL and obtain the fundamental current i g0 . In the second channel, the abc / dq transformation subunit is used to perform Park transformation processing on the grid-connected point current i P according to the disturbance phase θ g ; the low-pass filter subunit is used to filter the grid-connected point current i g after Park transformation processing and obtain two-phase disturbance currents; the dq / abc transformation subunit is used to perform inverse Park transformation processing on the two-phase disturbance currents according to the disturbance phase θ P and obtain the disturbance current i p .

[0140] In one embodiment, as shown in Figure 6 and Figure 13 , the disturbance control unit 32 is further used to obtain the reference amplitude I p of the disturbance current; according to the reference amplitude I p of the disturbance current and the disturbance phase θ P to obtain the reference command i p_ref of the disturbance current; according to the disturbance current i p and the reference command i p_ref of the disturbance current to perform proportional-resonant control processing and obtain the reference command m p of the disturbance modulation voltage.

[0141] In one embodiment, as shown in Figure 6 and Figure 13 , the disturbance control unit 32 includes a reference command generation subunit, a subtractor, and a PR controller. Among them, the reference command generation subunit is used to obtain the reference amplitude I p of the disturbance current, and according to the reference amplitude I p of the disturbance current and the disturbance phase θ P to obtain the reference command i p_ref of the disturbance current. The subtractor is used to obtain the disturbance current difference between the disturbance current i p and the reference command i p_ref of the disturbance current. The PR controller is used to perform proportional-resonant control processing on the disturbance current difference according to the disturbance frequency ω p and obtain the reference command m p of the disturbance modulation voltage.

[0142] In one embodiment, as shown in Figure 8 and Figure 13 , the grid-connected point voltage u PCCis the three-phase grid connection point voltage. The inverter control device 30 further includes a phase-locked unit 41, and the phase-locked unit 41 is used to obtain the grid connection point voltage u PCC , perform Clarke transformation processing and filtering processing on the grid connection point voltage u PCC , and obtain the two-phase grid connection point voltage; perform inverse Clarke transformation processing on the two-phase grid connection point voltage, and obtain the filtered grid connection point voltage ; perform phase-locking processing on the filtered grid connection point voltage , and obtain the real-time phase θ PLL . Exemplarily, the phase-locked unit 41 may include a phase-locked loop 35.

[0143] Exemplarily, the phase-locked unit 41 may include an abc / αβ transformation subunit, a filtering subunit, an αβ / abc transformation subunit, and a phase-locking subunit; wherein, the abc / αβ transformation subunit is used to obtain the grid connection point voltage u PCC , and perform Clarke transformation processing on the grid connection point voltage u PCC ; the filtering subunit is used to perform filtering processing on the grid connection point voltage after Clarke transformation processing, and obtain the two-phase grid connection point voltage; the αβ / abc transformation subunit is used to perform inverse Clarke transformation processing on the two-phase grid connection point voltage, and obtain the filtered grid connection point voltage ; the phase-locking subunit is used to perform phase-locking processing on the filtered grid connection point voltage , and obtain the real-time phase θ PLL . Exemplarily, the phase-locking subunit may include an SRF-PLL (Synchronous Reference Frame Phase-Locked Loop, synchronous reference frame phase-locked loop 35), which is used to perform phase-locking processing on the filtered grid connection point voltage to obtain the real-time phase θ PLL .

[0144] Based on the same inventive concept, an impedance measurement device 40 for implementing the impedance measurement method involved above is further provided in an embodiment of the present application. The implementation solution provided by this device to solve the problem is similar to the implementation solution described in the above method. Therefore, the specific limitations in one or more embodiments of the impedance measurement device 40 provided below can refer to the limitations on the impedance measurement method in the above text, and will not be elaborated here.

[0145] In one embodiment, as Figure 14 shown, an impedance measurement device 40 is provided, which is applied to the power grid system as Figure 1 shown. The power grid system includes an inverter 10 and a distribution network 20, wherein the inverter 10 can be controlled by using the disturbance control method provided in the foregoing embodiment. The impedance measurement device 40 includes a phase-locked unit 41, a second current separation unit 42, and an impedance measurement unit 43.

[0146] The phase-locked unit 41 is used to obtain the grid connection point voltage u of the grid connection point in the power grid system. PCC , for the grid voltage u PCC Perform phase locking and filtering, and obtain the real-time phase θ of the grid connection point voltage PLL and the grid connection point voltage after filtering The phase-locked unit 41 may be the same as the phase-locked unit 41 in the inverter control device 30. For example, the inverter control device 30 and the impedance measurement device 40 may include the same phase-locked unit 41, and the phase-locked unit 41 may be a phase-locked loop 35. The second current separation unit 42 is used to obtain the grid-connected point current i of the grid-connected point in the power grid system. g and the disturbance frequency ω p , according to the real-time phase θ PLL and the disturbance frequency ω p The grid-connected current i g Perform current separation and obtain the disturbance current i p For example, the second current separation unit 42 may be the same as the first current separation unit 31 in the inverter control device 30. For example, the inverter control device 30 and the impedance measurement device 40 may include the same current separation unit 311. The impedance measurement unit 43 is used to measure the impedance of the grid-connected point voltage u PCC , Grid connection point voltage after filtering , disturbance current i p and the disturbance frequency ω p , determine the impedance of the distribution network 20.

[0147] In one embodiment, Figure 13 As shown, the impedance measurement unit 43 includes a signal processing unit 431 and an impedance calculation unit 432. The signal processing unit 431 is used to calculate the impedance according to the grid connection point voltage u PCC and the grid connection point voltage after filtering Get the disturbance voltage u p ; According to the disturbance voltage u p , disturbance current i p and the disturbance frequency ω p Perform discrete Fourier transform and positive and negative sequence operations, and obtain the disturbance frequency ω p The impedance calculation unit 432 is used to determine the impedance of the distribution network 20 according to the positive and negative sequence currents and the positive and negative sequence voltages.

[0148] For example, Figure 11 As shown, the impedance calculation unit 432 may include a subtractor, a DFT subunit and a positive and negative sequence operation subunit; wherein the subtractor is used to calculate the impedance according to the grid connection point voltage u PCC and the grid connection point voltage after filtering Obtain the disturbance voltage u p ; The DFT subunit is used to perform discrete Fourier transform on the disturbance voltage u p and the disturbance current i p according to the disturbance frequency ω p ; The positive and negative sequence operation subunit is used to perform positive and negative sequence operations on the disturbance voltage and disturbance current after discrete Fourier transform, and obtain the positive and negative sequence currents and positive and negative sequence voltages corresponding to the disturbance frequency ω p

[0149] In one embodiment, as Figure 13 shown, the impedance measurement unit 43 further includes an impedance measurement result summarization unit 433, and the impedance measurement result summarization unit 433 can be used to store the impedance of the distribution network at different disturbance frequencies ω p . In application, the impedance measurement result summarization unit 433 can use the disturbance frequency ω p tag and the positive and negative sequence impedance tags to store the impedance of the distribution network at different disturbance frequencies ω p .

[0150] Each unit in the above inverter bridge 11 control device and impedance measurement device 40 can be implemented in whole or in part by software, hardware, and their combination. Each of the above units can be embedded in the processor of the computer device in hardware form or independent of it, or stored in the memory of the computer device in software form, so that the processor can call and execute the operations corresponding to each of the above units.

[0151] Based on the same application concept, in one embodiment, as Figure 13 shown, a power grid system is provided, which includes an inverter 10 and a distribution network 20; the system further includes the inverter control device 30 provided in any one of the foregoing embodiments, and / or, the impedance measurement device 40 provided in any one of the foregoing embodiments.

[0152] In one embodiment, as Figure 13 shown, a power grid system is provided, which includes an inverter 10, a distribution network 20, an inverter control device 30, and an impedance measurement device 40.

[0153] Among them, the inverter 10 includes a DC side power supply U dc , an inverter bridge 11, and an inductor L f1 ; the distribution network 20 includes an equivalent resistance R g , an equivalent inductor L g , and an equivalent voltage source u g ​。The connection point between the inverter 10 and the power distribution network 20 is the grid connection point. The inverter control device 30 includes a phase-locked loop 35, a current separation unit 311, a fundamental current control loop 331, a disturbance control loop 321, and a modulation loop 341. It can be understood that in this power grid system, the inverter control device 30 and the impedance measurement device 40 share a current separation unit 311 and a phase-locked loop 35, and the current separation unit 311 and the phase-locked loop 35 can be integrated into the inverter control device 30.

[0154] In application, the inputs of the inverter control device 30 include the grid connection point voltage u PCC and the grid connection point current i g , where the grid-connected voltage u PCC is input into the phase-locked loop 35 and outputs the locked real-time phase θ PLL of the grid connection point voltage and the grid connection point voltage after filtering out the disturbance ; the grid connection point current i g and the real-time phase θ PLL of the grid connection point voltage are then input into the current separation unit 311, and the output channels of the current separation unit 311 respectively output the fundamental current i g0 and the disturbance current i p ; then the fundamental current i g0 output by the current separation unit 311 and the real-time phase θ PLL of the grid connection point voltage output by the phase-locked loop 35 are simultaneously input into the fundamental current control loop 331; the fundamental current control loop 331 then generates a fundamental modulation voltage reference command m 0 and inputs it into the modulation loop 341; the disturbance current i p output by the current separation unit 311 and the reference amplitude I p set for the disturbance current, the disturbance frequency ω p are then input into the disturbance control loop 321; the disturbance control loop 321 generates a disturbance modulation voltage reference command m p after control adjustment and inputs it into the modulation loop 341; the modulation loop 341 generates a drive signal for the inverter bridge 11 according to the input disturbance modulation voltage reference command m p and the fundamental modulation voltage reference command m 0 .

[0155] The impedance measurement unit 43 includes a signal processing unit 431, an impedance calculation unit 432, and an impedance measurement result summary unit 433; among them, the input signals of the signal processing unit 431 are the disturbance current i p output by the current separation unit 311, the grid connection point voltage u PCC , the grid connection point voltage after filtering out the disturbance in the phase-locked loop 35 , disturbance frequency ω p ; After the above signal passes through the signal processing unit 431, the positive-sequence current signal i at the injected disturbance frequency ω p is obtained. gp (jω p ), negative-sequence current signal i gn (jω p ), positive-sequence voltage signal U PCCp (jω p ) and negative-sequence voltage signal U PCCn (jω p ); The above positive- and negative-sequence voltage and positive- and negative-sequence current signals are input into the impedance calculation unit 432, and the positive-sequence impedance Z of the power grid is calculated gp (jω p ) and negative-sequence impedance Z gn (jω p ). The impedances measured at each frequency point are all input into the impedance measurement result summary unit 433 to obtain the impedance measurement result of the full frequency band.

[0156] For the phase-locked loop 35, as Figure 8 shown, the grid-connected point voltage u PCC is first input into the abc / ab transformation sub-unit to obtain the α-axis grid-connected point voltage u α and the β-axis grid-connected point voltage . The above voltages are input into the filter sub-unit N(s) to filter out the voltage disturbance components formed during the impedance measurement process, and prevent the above components from flowing into the control system of the inverter 10 through the phase-locked loop 35 and affecting the system fundamental current control effect; The expression of the filter sub-unit N(s) can be referred to the previous formula (2).

[0157] For the current separation unit 311, as Figure 4 shown, the grid-connected point current i g are respectively input into the abc / dq transformation sub-units of two different channels. In the first channel of the figure, the phase input into the abc / dq transformation sub-unit is the real-time phase θ of the grid-connected point voltage output by the phase-locked loop 35 PLL . After the two-channel signals after transformation pass through low-pass filtering, the d-axis fundamental current i g0d and the q-axis fundamental current i g0q are obtained respectively, and then the abc-axis fundamental current i PLL is obtained through the dq / abc transformation sub-unit with the input phase being the real-time phase θ of the grid-connected point voltage g0 ; In the second channel, the phase input into the abc / dq transformation sub-unit is θ p , which changes according to the different disturbance control frequencies at this time, and its value and the relationship with the input disturbance frequency ω p and time t can be expressed as θ p = ω p*t, grid connection point current i g It is input into the low-pass filter through this unit, and then the d-axis disturbance current i pd and the q-axis disturbance current i pq are obtained respectively; then through the dq / abc transformation unit with the input phase of θ p , the disturbance current i p under the abc axis is obtained. In summary, the grid connection point current i g can obtain the fundamental current i g0 and the disturbance current i p respectively through the two channels of current separation. In the subsequent links, the fundamental current i g0 is input into the fundamental current control loop 331, and the disturbance current i p is input into the disturbance control loop 321.

[0158] For the disturbance control loop 321, as Figure 6 shown, the disturbance current command amplitude I p and the disturbance frequency ω p are first input into the reference command generation unit to generate the a-phase disturbance current reference command i pa_ref , the b-phase disturbance current reference command i pb_ref , and the c-phase disturbance current reference command i pc_ref . The generation method can refer to the previous formula (1). The generated command values i pa_ref , i pb_ref and i pc_ref are respectively compared with the actual disturbance current values i pa , i pb and i pc of each phase. Then the comparison error is input into the PR controller for error adjustment. It should be noted that at this time, the resonant frequency setting ω f = ω p . It should be noted that the resonant frequency ω f changes with the change of the set disturbance output frequency; the outputs of each PR controller are respectively used as the a-phase disturbance modulation voltage reference command m p_a , the b-phase disturbance modulation voltage reference command m p_b , and the c-phase disturbance modulation voltage reference command m p_c ; the reference commands of the abc phases together constitute the three-phase command values of the disturbance modulation voltage m p and are input into the modulation loop 341.

[0159] The fundamental current control loop 331 and the modulation loop 341 can adopt the general control algorithms of the grid-connected inverter 10. For example, SVPWM modulation or SPWM modulation can be adopted in the modulation loop 341, and common control strategies such as the dq-axis current control method or the PR control on the abc coordinate axes can be adopted in the fundamental current control loop 331. Details are not elaborated here.

[0160] For the signal processing unit 431, as Figure 11 shown, its input signals include the disturbance current i p output by the current separation unit 311, the grid connection point voltage u PCC , the voltage after filtering out the disturbance in the phase-locked loop 35 , and the disturbance frequency ω p ; the grid connection point voltage u PCC and the voltage after filtering out the disturbance in the phase-locked loop 35 are used to obtain the disturbance voltage signal u p ; then the disturbance voltage signal u p and the disturbance current signal i p are both input into the DFT unit, and the corresponding frequency-domain components are extracted according to the disturbance frequency ω p at this time. After positive and negative sequence operations, the positive sequence current signal i p at the injection disturbance frequency ω gp (jω p ), the negative sequence current signal i gn (jω p ), the positive sequence voltage signal U PCCp (jω p ) and the negative sequence voltage signal U PCCn (jω p ) are obtained; and the extracted voltage disturbance and current disturbance values are sent to the impedance calculation unit 432.

[0161] The impedance calculation unit 432 can calculate the positive sequence impedance Z p of the power grid at the disturbance frequency ω gp (jω p ) and the negative sequence impedance Z gn (jω p ) based on the obtained disturbance positive and negative sequence voltages and positive and negative sequence currents. The calculation process can be described and referred to the previous formula (3).

[0162] The impedance measurement result summary unit 433 mainly needs to perform multiple measurements when obtaining the broadband impedance of the distribution network 20. Each measurement only obtains the positive sequence impedance Z gp (jω p ) and the negative sequence impedance Z gn (jω p) The results of each measurement need to be stored, and frequency tags and positive / negative sequence tags are provided to prevent the impedances obtained from different measurement processes from being confused, which would render the measurement results worthless. At the same time, this unit also provides an export function for impedance measurement data.

[0163] In one embodiment, a computer device is provided. The computer device can be a server, and its internal structure diagram can be as Figure 15 shown. The computer device includes a processor, a memory, and a network interface connected through a system bus. Among them, the processor of the computer device is used to provide computing and control capabilities. The memory of the computer device includes a non-volatile storage medium and an internal memory. The non-volatile storage medium stores an operating system, a computer program, and a database. The internal memory provides an environment for the operation of the operating system and the computer program in the non-volatile storage medium. The network interface of the computer device is used to communicate with an external terminal through a network connection. When the computer program is executed by the processor, it implements an inverter control method and / or an impedance measurement method.

[0164] Those skilled in the art can understand that Figure 15 the structure shown in

[0165] is only a block diagram of some structures related to the solution of the present application, and does not constitute a limitation on the computer device to which the solution of the present application is applied. The specific computer device may include more or fewer components than those shown in the figure, or combine certain components, or have different component arrangements.

[0166] In one embodiment, a computer device is provided, including a memory and a processor. A computer program is stored in the memory, and when the processor executes the computer program, it implements the steps of the aforementioned inverter control method and / or impedance measurement method.

[0166] In one embodiment, a computer-readable storage medium is provided, on which a computer program is stored. When the computer program is executed by the processor, it implements the steps of the aforementioned inverter control method and / or impedance measurement method.

[0167] In one embodiment, a computer program product is provided, including a computer program. When the computer program is executed by the processor, it implements the steps of the aforementioned inverter control method and / or impedance measurement method.

[0168] It should be noted that the user information (including but not limited to user device information, user personal information, etc.) and data (including but not limited to data for analysis, stored data, displayed data, etc.) involved in the present application are all information and data that have been authorized by the user or fully authorized by all parties.

[0169] Those of ordinary skill in the art can understand that all or part of the processes in the methods of the above embodiments can be completed by instructing relevant hardware through a computer program. The computer program can be stored in a non-volatile computer-readable storage medium. When the computer program is executed, it can include the processes of the embodiments of the above methods. Among them, any reference to a memory, database, or other medium used in the embodiments provided in the present application can include at least one of non-volatile and volatile memories. Non-volatile memory can include read-only memory (ROM), magnetic tape, floppy disk, flash memory, optical memory, high-density embedded non-volatile memory, resistive random access memory (ReRAM), magnetoresistive random access memory (MRAM), ferroelectric random access memory (FRAM), phase change memory (PCM), graphene memory, etc. Volatile memory can include random access memory (RAM) or external cache memory, etc. By way of illustration and not limitation, RAM can be in various forms, such as static random access memory (SRAM) or dynamic random access memory (DRAM), etc. The databases involved in the embodiments provided in the present application can include at least one of relational databases and non-relational databases. Non-relational databases can include distributed databases based on blockchain, etc., without limitation. The processors involved in the embodiments provided in the present application can be general-purpose processors, central processors, graphics processors, digital signal processors, programmable logic devices, data processing logics based on quantum computing, etc., without limitation.

[0170] The technical features of the above embodiments can be combined arbitrarily. For the sake of concise description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification.

[0171] The above-described embodiments only represent several implementation manners of the present application. The description is relatively specific and detailed, but it should not be construed as a limitation on the patent scope of the present application. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several modifications and improvements can still be made, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the appended claims.

Claims

1. An inverter control method, characterized in that: An inverter applied to a power grid system, wherein the power grid system further comprises a power distribution network connected to the inverter; the method comprises: Respectively obtaining the real-time phase of the grid-connected point current and the grid-connected point voltage, as well as the disturbance phase of the grid-connected point in the power grid system; the grid-connected point is the connection point between the inverter and the distribution network; Performing current separation processing on the grid-connected point current according to the real-time phase and the disturbance phase, and obtaining fundamental current and disturbance current; Performing disturbance control processing on the disturbance current according to the disturbance phase and obtaining a disturbance modulation voltage reference instruction, and performing fundamental wave control processing on the fundamental wave current according to the real-time phase and obtaining a fundamental wave modulation voltage reference instruction; A drive signal for driving the inverter is generated according to the disturbance modulation voltage reference instruction and the fundamental wave modulation voltage reference instruction.

2. The method according to claim 1, characterized in that The grid-connected point current, the fundamental current, and the disturbance current are respectively currents in a three-phase coordinate system; wherein, the current separation processing is performed on the grid-connected point current according to the real-time phase and the disturbance phase, and the fundamental current and the disturbance current are obtained, including: Performing Park transformation and filtering processing on the grid-connected point current according to the real-time phase, and obtaining two-phase fundamental current; Performing inverse Park transformation processing on the two-phase fundamental current according to the real-time phase, and obtaining the fundamental current; Performing Park transformation and filtering processing on the grid-connected point current according to the disturbance phase, and obtaining two-phase disturbance current; An inverse Park transform is performed on the two-phase disturbance current according to the disturbance phase, and the disturbance current is obtained.

3. The method according to claim 1, characterized in that The performing disturbance control processing on the disturbance current according to the disturbance phase and obtaining a disturbance modulation voltage reference instruction includes: Obtaining a disturbance current reference amplitude; Acquire a disturbance current reference instruction according to the disturbance current reference amplitude and the disturbance phase; Proportional resonance control processing is performed according to the disturbance current and the disturbance current reference instruction, and the disturbance modulation voltage reference instruction is obtained.

4. The method according to claim 3, characterized in that The step of performing proportional frequency adjustment according to the disturbance current and the disturbance current reference instruction and obtaining the disturbance modulation voltage reference instruction comprises: Acquiring a disturbance current difference between the disturbance current and the disturbance current reference instruction; The disturbance current difference is subjected to proportional resonance control processing according to the disturbance frequency, and the disturbance modulation voltage reference instruction is obtained.

5. The method according to any one of claims 1 to 4, characterized in that: The grid connection point voltage is a three-phase grid connection point voltage; the real-time phase of the grid connection point current and the grid connection point voltage, and the disturbance phase of the grid connection point current and the grid connection point voltage of the power grid system are respectively obtained, including: Respectively obtaining the grid-connected point current, the grid-connected point voltage and the disturbance phase; Performing Clarke transformation and filtering processing on the grid connection point voltage, and obtaining the two-phase grid connection point voltage; Performing an inverse Clarke transform on the two-phase grid-connected point voltage and obtaining a filtered grid-connected point voltage; The filtered grid connection point voltage is phase-locked and the real-time phase is obtained.

6. An impedance measurement method, characterized in that: Applied to a power grid system, the power grid system includes an inverter and a distribution network, the inverter is controlled by a method according to any one of claims 1 to 5; the method includes: Respectively obtaining a grid connection point current, a grid connection point voltage and a disturbance frequency of a grid connection point in the power grid system; the grid connection point is a connection point between the inverter and the power distribution network; Performing phase-locking processing and filtering processing on the grid connection point voltage, and obtaining the real-time phase of the grid connection point voltage and the filtered grid connection point voltage; Performing current separation processing on the grid-connected point current according to the real-time phase and the disturbance frequency, and obtaining the disturbance current; The impedance of the distribution network is determined according to the grid connection point voltage, the filtered grid connection point voltage, the disturbance current and the disturbance frequency.

7. The method according to claim 6, characterized in that The determining the impedance of the distribution network according to the grid connection point voltage, the filtered grid connection point voltage, the disturbance current and the disturbance frequency includes: Obtaining a disturbance voltage according to the grid connection point voltage and the filtered grid connection point voltage; Performing discrete Fourier transform and positive and negative sequence operations according to the disturbance voltage, the disturbance current and the disturbance frequency, and obtaining positive and negative sequence currents and positive and negative sequence voltages corresponding to the disturbance frequency; The impedance of the power distribution network is determined according to the positive and negative sequence currents and the positive and negative sequence voltages.

8. An inverter control device, characterized in that: An inverter applied to a power grid system, wherein the power grid system further comprises a power distribution network connected to the inverter; the device comprises: A first current separation unit, used to respectively obtain the grid-connected point current and the real-time phase of the grid-connected point voltage, and the disturbance phase of the grid-connected point in the power grid system, perform current separation processing on the grid-connected point current according to the real-time phase and the disturbance phase, and obtain the fundamental current and the disturbance current; the grid-connected point is the connection point between the inverter and the distribution network; A disturbance control unit, used for performing disturbance control processing on the disturbance current according to the disturbance phase, and obtaining a disturbance modulation voltage reference instruction; A fundamental wave control unit, used for performing fundamental wave control processing on the fundamental wave current according to the real-time phase, and obtaining a fundamental wave modulation voltage reference instruction; A modulation unit is used to generate a drive signal for driving the inverter according to the disturbance modulation voltage reference instruction and the fundamental wave modulation voltage reference instruction.

9. An impedance measuring device, characterized in that: Applied to a power grid system, the power grid system includes an inverter and a distribution network, the inverter is controlled by the method according to any one of claims 1 to 5; the device includes: A phase-locking unit, used to obtain a grid-connected point voltage of a grid-connected point in the power grid system, perform phase-locking processing and filtering processing on the grid-connected point voltage, and obtain a real-time phase of the grid-connected point voltage and a grid-connected point voltage after filtering; A second current separation unit is used to respectively obtain a grid connection point current and a disturbance frequency of a grid connection point in the power grid system, perform current separation processing on the grid connection point current according to the real-time phase and the disturbance frequency, and obtain the disturbance current; An impedance measurement unit is used to determine the impedance of the distribution network according to the grid connection point voltage, the filtered grid connection point voltage, the disturbance current and the disturbance frequency.

10. A power grid system, characterized in that: The power grid system includes an inverter and a power distribution network; the system also includes the inverter control device as claimed in claim 8, and / or the impedance measurement device as claimed in claim 9.

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