Fault analysis method, device and system based on power grid current

Abstract

The invention relates to a fault analysis method, device and system based on power grid current, relates to the technical field of power systems, and solves the problem of low calculation speed and convergence speed caused by nonlinear power supply influence in a short-circuit current iterative calculation process. The method comprises the following steps: determining each target power supply type to which a nonlinear power supply accessed to each target network point in a plurality of network points accessed to a power grid belongs; each target power supply type corresponds to different equivalent models; determining each target short-circuit current corresponding to each target network point by adopting a target equivalent model corresponding to a target power supply type to which each target network point belongs and the network point voltage of each target power supply; and based on the network voltage influence on each target power supply network after each target short-circuit current of the target power supply type is iteratively changed, dividing nonlinear power supplies of each target power supply type to carry out iterative calculation in batches so as to consider the network voltage and the short-circuit current of each target network under the influence of the nonlinear power supplies to carry out fault analysis.

Description

Technical Field

[0001] The present disclosure relates to the technical field of power systems, and in particular to a fault analysis method, device and system based on power grid current. Background Art

[0002] With the transformation of the global energy structure and the urgent need for environmental protection, the construction of new power systems is gradually becoming an important direction for global energy development. Against this background, the proportion of new energy and power electronic equipment such as wind power, photovoltaic and energy storage power stations in my country's power system continues to rise, making it increasingly difficult to use traditional short-circuit current analysis theories and methods to calculate the fault current of large-scale wind, light and storage connected to the power grid. At present, the mainstream method for realizing the fault current calculation of large-scale wind, light and storage connected to the power grid is to treat wind, light and storage equipment as nonlinear voltage-controlled current sources. When calculating the fault current, the nonlinear voltage-controlled current sources of the entire network are input into an equivalent model for iterative calculation. However, with the increase in the number of wind, light, storage and other equipment in the power grid, the speed, convergence and convergence speed of fault calculation in the iterative calculation process based on short-circuit current will continue to decrease, especially when performing fault calculation in large-scale and complex topological power grids. Due to the huge order of its mathematical matrix model, the efficiency of fault analysis is lower. Summary of the invention

[0003] The present invention provides a fault analysis method, device and system based on power grid current, so as to at least solve the problem that in the iterative calculation process based on short-circuit current in the related prediction method, the calculation speed and convergence speed are reduced due to the influence of nonlinear power supply, resulting in low efficiency of fault analysis. The technical solution of the present invention is as follows:

[0004] According to a first aspect of an embodiment of the present invention, a fault analysis method based on grid current is provided, which is applied to a grid system, wherein the grid system includes a doubly-fed induction fan, a permanent magnet direct-drive fan, a photovoltaic power source and an energy storage system, and the method includes: determining each target power source type to which the nonlinear power source connected to each target grid point among multiple grid points connected to the grid belongs; each target power source type includes one or more of the following: a doubly-fed induction fan, a permanent magnet direct-drive fan and a photovoltaic power source, and an energy storage system; the doubly-fed induction fan, the permanent magnet direct-drive fan and the photovoltaic power source and the energy storage system correspond to three different equivalent models respectively; each target grid point represents a grid point to which the power source connected is a nonlinear power source; each target grid point uses the target equivalent model corresponding to the target power source type to which each target grid point belongs and the grid point voltage of the target power source connected to each target grid point to determine each target short-circuit current corresponding to each target grid point; based on the change trend of the grid point voltage of each target grid point caused by the iterative change of each target short-circuit current of each target power source type under different iteration steps, the nonlinear power sources of each target power source type are divided, and iterative calculations are performed in batches, so as to perform fault analysis according to the calculation results of the iterative calculations performed in batches.

[0005] After the target short-circuit currents of the target power types mentioned above are iteratively changed, the change trend of the network point voltage of each target network point caused by the change is an upward trend or a downward trend.

[0006] In the above implementation, different equivalent models are set for different types of nonlinear power supplies, and the short-circuit current of each target network point is determined according to the equivalent model to which each target network point belongs.

[0007] Specifically, the target equivalent model corresponding to the target power source type to which each target network point belongs is first determined; and then the target equivalent model corresponding to each target network point is respectively adopted to determine each target short-circuit current corresponding to each target network point.

[0008] In one implementation, a target equivalent model corresponding to a target power source type to which each target network point belongs is used to determine each target short-circuit current corresponding to each target network point, including: when it is determined that a nonlinear power source of a first network point among multiple network points is a double-fed induction wind turbine, a first short-circuit current of the first network point is determined according to a first equivalent model corresponding to the double-fed induction wind turbine and a network point voltage of the first network point;

[0009] and / or, when it is determined that the nonlinear power supply of the second network point among the multiple network points is a permanent magnet direct-drive wind turbine and a photovoltaic power supply, determining the second short-circuit current of the second network point according to the second equivalent model corresponding to the permanent magnet direct-drive wind turbine and the photovoltaic power supply and the network point voltage of the second network point;

[0010] And / or, when determining that a nonlinear power supply having a third network point among multiple network points is an energy storage system, if the energy storage system is in a discharging state, determining a third short-circuit current of the third network point according to the second equivalent model and the network voltage of the third network point; and, if the energy storage system is in a charging state, determining a fourth short-circuit current of the third network point according to a third equivalent model corresponding to the energy storage system and the network voltage of the third network point.

[0011] In another implementation, the first short-circuit current includes the grid-connected point orthogonal axis current per unit value of the first grid point, the grid-connected point direct axis current per unit value of the first grid point, and the grid-connected point current per unit value of the first grid point; the first equivalent model is specifically:

[0012]

[0013] Where: I q 1 I is the per unit value of the orthogonal axis current of the first grid point; d 1 I is the per unit value of the direct axis current of the first grid point; w1 1 is the per-unit value of the grid-connected current of the first grid point; θ w1 is the phase angle between the grid-connected voltage and current of the first grid point; U L is the positive sequence voltage drop threshold parameter, U T 1 is the grid-connected point voltage per unit value of the first grid point; 2 is the dynamic reactive current proportional coefficient of energy storage; I max is the maximum current of the inverter; U Cb Input threshold value for the crowbar resistor; I N is the rated current of the inverter; Z Cb * is the positive sequence equivalent impedance when the crowbar circuit operates.

[0014] In another implementation, the second short-circuit current includes the grid-connected point orthogonal axis current per unit value of the second network point, the grid-connected point direct axis current per unit value of the second network point, and the grid-connected point current per unit value of the second network point; the second equivalent model is specifically:

[0015]

[0016] Among them, I q 2 I is the per unit value of the orthogonal axis current at the grid connection point of the second grid point; d 2 I is the per unit value of the direct-axis current of the second grid point; w2 2 is the per-unit value of the grid-connected current of the second grid point; θ w2 is the phase angle between the grid-connected voltage and current of the second grid point; U Lis the positive sequence voltage drop threshold parameter, U T 2 is the grid-connected point voltage per unit value of the second network point; 2 is the dynamic reactive current proportional coefficient of energy storage; I max is the maximum current of the inverter; I N is the rated current of the inverter.

[0017] In another implementation, the third short-circuit current includes the grid-connected point orthogonal axis current per unit value of the third grid point, the grid-connected point direct axis current per unit value of the third grid point, and the grid-connected point current per unit value of the third grid point; the third equivalent model is specifically:

[0018]

[0019] Among them, I q 3 I is the per unit value of the rectangular axis current at the grid connection point of the third grid point; d 3 I is the per unit value of the direct-axis current at the third grid point; w3 3 is the per-unit value of the grid-connected current of the third grid point; θ w3 The phase angle between the voltage and current at the third grid point; U L is the positive sequence voltage drop threshold parameter, U T 3 is the voltage per unit value of the third grid point; 2 is the dynamic reactive current proportional coefficient of energy storage; I max is the maximum current of the inverter; I N is the rated current of the inverter.

[0020] In another implementation, based on the changes in the network point voltages of each target network point caused by the iterative changes of each target short-circuit current of the target power type under different iteration steps, the nonlinear power supplies of each target power type are divided, and iterative calculations are performed in batches, so as to perform fault analysis on each target network point according to the calculation results of the iterative calculations performed in batches, including: for any nonlinear power supply of the target power type, determining each target short-circuit current of each target network point under the nonlinear power supply of the target power type in multiple iteration steps; according to the order of iteration steps, based on the current difference between the target short-circuit currents of each target network point obtained in adjacent steps in the multiple iteration steps, determining the voltage difference of the network point voltages of each target power supply caused before and after the target short-circuit current changes; for any target network point among the target network points, dividing the target power supplies with the same voltage difference change trend into the same group, and iterating together according to the same group when performing the short-circuit current iterative calculation;

[0021] After completing the grouping of each target power source, the target short-circuit current of each group is iteratively calculated in turn, so as to perform fault analysis based on the calculation results after iterative calculation in batches according to each group.

[0022] The voltage difference change trend means that the upward trend or downward trend is the same, that is, it rises and falls at the same time.

[0023] Short-circuit current is also called fault current or power short-circuit current.

[0024] According to a second aspect of an embodiment of the present invention, a fault analysis device based on grid current is provided, which is applied to a grid system, wherein the grid system includes a double-fed induction wind turbine, a permanent magnet direct-drive wind turbine, a photovoltaic power source and an energy storage system, and the device includes:

[0025] The first determination unit is used to determine each target power source type to which the nonlinear power source connected to each target network point among multiple network points connected to the power grid belongs; each target power source type includes one or more of the following: a double-fed induction wind turbine, a permanent magnet direct-drive wind turbine and a photovoltaic power source, and an energy storage system; the double-fed induction wind turbine, the permanent magnet direct-drive wind turbine and the photovoltaic power source and the energy storage system correspond to three different equivalent models respectively;

[0026] A second determination unit is used to respectively use the target equivalent model corresponding to the target power source type to which each target network point belongs and the network point voltage of each target power source to determine each target short-circuit current corresponding to each target network point;

[0027] A fault analysis unit is used to calculate the impact of the iterative changes of each target short-circuit current based on the target power type on the network point voltage of each target power point, divide the nonlinear power supply of each target power type into batches for iterative calculation, complete the calculation of the network point voltage and short-circuit current of each target network point under the influence of the nonlinear power supply, and perform fault analysis on each target network point.

[0028] In one implementation, the second determination unit is specifically used to: when it is determined that a nonlinear power supply of a first network point among multiple network points is a doubly fed induction wind turbine, determine a first short-circuit current of the first network point according to a first equivalent model corresponding to the doubly fed induction wind turbine and the network voltage of the first network point; and / or, when it is determined that a nonlinear power supply of a second network point among multiple network points is a permanent magnet direct-drive wind turbine and a photovoltaic power source, determine a second short-circuit current of the second network point according to a second equivalent model corresponding to the permanent magnet direct-drive wind turbine and the photovoltaic power source and the network voltage of the second network point; and / or, when it is determined that a nonlinear power supply of a third network point among multiple network points is an energy storage system, if the energy storage system is in a discharging state, determine a third short-circuit current of the third network point according to the second equivalent model and the network voltage of the third network point; and, if the energy storage system is in a charging state, determine a fourth short-circuit current of the third network point according to a third equivalent model corresponding to the energy storage system and the network voltage of the third network point.

[0029] In another implementation, the first short-circuit current includes the grid-connected point orthogonal axis current per unit value of the first grid point, the grid-connected point direct axis current per unit value of the first grid point, and the grid-connected point current per unit value of the first grid point; the first equivalent model is specifically:

[0030]

[0031] Where: I q 1 I is the per unit value of the orthogonal axis current of the first grid point; d 1 I is the per unit value of the direct axis current of the first grid point; w1 1 is the per-unit value of the grid-connected current of the first grid point; θ w1 is the phase angle between the grid-connected voltage and current of the first grid point; U L is the positive sequence voltage drop threshold parameter, U T 1 is the grid-connected point voltage per unit value of the first grid point; 2 is the dynamic reactive current proportional coefficient of energy storage; I max is the maximum current of the inverter; U Cb Input threshold value for the crowbar resistor; I N is the rated current of the inverter; Z Cb * is the positive sequence equivalent impedance when the crowbar circuit operates.

[0032] In another implementation, the second short-circuit current includes the grid-connected point orthogonal axis current per unit value of the second network point, the grid-connected point direct axis current per unit value of the second network point, and the grid-connected point current per unit value of the second network point; the second equivalent model is specifically:

[0033]

[0034] Among them, I q 2 I is the per unit value of the orthogonal axis current at the grid connection point of the second grid point; d 2 I is the per unit value of the direct-axis current of the second grid point; w2 2 is the per-unit value of the grid-connected current of the second grid point; θ w2 is the phase angle between the grid-connected voltage and current of the second grid point; U L is the positive sequence voltage drop threshold parameter, U T 2 is the grid-connected point voltage per unit value of the second network point; 2 is the dynamic reactive current proportional coefficient of energy storage; I max is the maximum current of the inverter; I N is the rated current of the inverter.

[0035] In another implementation, the third short-circuit current includes the grid-connected point orthogonal axis current per unit value of the third grid point, the grid-connected point direct axis current per unit value of the third grid point, and the grid-connected point current per unit value of the third grid point; the third equivalent model is specifically:

[0036]

[0037] Among them, I q 3 I is the per unit value of the rectangular axis current at the grid connection point of the third grid point; d 3 I is the per unit value of the direct-axis current at the third grid point; w3 3 is the per-unit value of the grid-connected current of the third grid point; θ w3 The phase angle between the voltage and current at the third grid point; U L is the positive sequence voltage drop threshold parameter, U T 3 is the voltage per unit value of the third grid point; 2 is the dynamic reactive current proportional coefficient of energy storage; I max is the maximum current of the inverter; I N is the rated current of the inverter.

[0038] In another implementation, the fault analysis unit is specifically used to: determine, for a nonlinear power supply of any target power supply type, each target short-circuit current of each target network point in multiple iteration steps under the nonlinear power supply of the target power supply type; determine, in accordance with the iteration step sequence, based on the current difference between the target short-circuit currents of each target network point obtained in adjacent steps in the multiple iteration steps, the voltage difference of the network point voltage of each target power supply caused before and after the target short-circuit current changes; for any target network point among each target network point, divide the target power supplies with the same voltage difference change trend into the same group, and iterate together according to the same group when performing the short-circuit current iterative calculation;

[0039] After completing the grouping of each target power source, the target short-circuit current of each group is iteratively calculated in turn, so as to perform fault analysis based on the calculation results after iterative calculation in batches according to each group.

[0040] The voltage difference change trend means that the upward trend or downward trend is the same, that is, it rises and falls at the same time.

[0041] Short-circuit current is also called fault current or power short-circuit current.

[0042] According to a third aspect of an embodiment of the present invention, a power grid system is provided, which includes a doubly-fed induction wind turbine, a permanent magnet direct-drive wind turbine, a photovoltaic power supply and an energy storage system, and is configured to execute the grid current-based fault analysis method of the above-mentioned first aspect and any possible implementation method thereof.

[0043] According to a fourth aspect of an embodiment of the present invention, a computer device is provided, comprising: a processor and a memory for storing processor executable instructions; wherein the processor is configured to execute executable instructions to implement a fault analysis method based on grid current as in the first aspect and any possible implementation thereof.

[0044] According to a fifth aspect of an embodiment of the present invention, a computer-readable storage medium is provided, on which instructions are stored, and the computer-readable storage medium is characterized in that when the instructions in the computer-readable storage medium are executed by a processor of a computer device, the electronic device is enabled to execute the fault analysis method based on grid current as in the first aspect.

[0045] According to a sixth aspect of an embodiment of the present disclosure, a computer program product is provided, the computer program product comprising computer instructions, which, when executed on a computer device, enables the computer device to execute the fault analysis method based on grid current of the above-mentioned first aspect and any possible implementation manner thereof.

[0046] The technical solution provided by the embodiment of the present invention brings at least the following beneficial effects: the present application sets different equivalent models for different types of nonlinear power sources, so that according to the equivalent model corresponding to the nonlinear power source, the short-circuit current of each target network point to which the nonlinear power source belongs is determined, so that the short-circuit current of each network under different types of nonlinear power sources is calculated according to different types of equivalent model classifications. Based on this, by dividing the nonlinear characteristics of the nonlinear voltage-controlled current source model, considering the iteration direction of these nonlinear power sources participating in iterative calculations under different grid connection point voltages, the nonlinear power sources that have a greater impact on each other during iterative calculations are divided into batches to participate in the iterative calculations, avoiding the situation where the number of iterations is too high or even non-convergence due to the simultaneous participation of multiple nonlinear power sources with large differences in iteration, thereby improving the convergence and calculation efficiency of fault current calculations of large-scale wind, light, storage and other equipment connected to the power grid.

[0047] It is to be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] The drawings herein are incorporated into and constitute a part of the specification, illustrate embodiments consistent with the present disclosure, and together with the description are used to explain the principles of the present disclosure, and do not constitute improper limitations on the present disclosure.

[0049] Figure 1 A flowchart of a fault analysis method based on power grid current is shown in an embodiment of the present invention;

[0050] Figure 2A schematic diagram of a first network point current and voltage variation curve according to an embodiment of the present invention;

[0051] Figure 3 A schematic diagram of a second network point current and voltage change curve according to an embodiment of the present invention;

[0052] Figure 4 A schematic diagram of a third network point current and voltage variation curve shown in an embodiment of the present invention;

[0053] Figure 5 A schematic diagram of a multi-station power grid shown in an embodiment of the present invention;

[0054] Figure 6 The invention is a block diagram showing a fault analysis device based on grid current according to an exemplary embodiment. DETAILED DESCRIPTION

[0055] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0056] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by technicians in the technical field to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" in the specification and claims of this application and the above-mentioned figure descriptions and any variations thereof are intended to cover non-exclusive inclusions.

[0057] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0058] It should be noted that the terms "first", "second", etc. in the specification and claims of the present disclosure and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present disclosure described herein can be implemented in an order other than those illustrated or described herein. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present disclosure. Instead, they are merely examples of devices and methods consistent with some aspects of the present disclosure as detailed in the appended claims.

[0059] The present application provides method operation steps as described in the embodiments or flow charts, but more or fewer operation steps may be included based on conventional or non-creative work. The order of steps listed in the embodiments is only a method for fault analysis based on grid current among many step execution orders, and does not represent the only execution order. The method should be implemented by software and / or hardware.

[0060] Figure 1 FIG. 1 is a flow chart of a fault analysis method based on grid current provided in an embodiment of the present application. Figure 1 As shown, the fault analysis method based on grid current includes the following steps. The method can be applied to a grid system including a double-fed induction wind turbine, a permanent magnet direct-drive wind turbine, a photovoltaic power source and an energy storage system.

[0061] S11, determining each target power source type to which the nonlinear power source connected to each target network point among multiple network points connected to the power grid belongs.

[0062] Each target power source type includes one or more of the following: a doubly-fed induction wind turbine, a permanent magnet direct-drive wind turbine and a photovoltaic power source, and an energy storage system; the doubly-fed induction wind turbine, the permanent magnet direct-drive wind turbine and the photovoltaic power source, and the energy storage system correspond to three different equivalent models respectively.

[0063] Each target network point represents a network point to which the connected power source is a nonlinear power source.

[0064] S12, respectively using the target equivalent model corresponding to the target power source type to which each target network point belongs and the network point voltage of the target power source to which each target network point is connected, to determine each target short-circuit current corresponding to each target network point.

[0065] In the above steps, different equivalent models are set for different types of nonlinear power supplies, and the short-circuit current of each target network point is determined according to the equivalent model to which each target network point belongs.

[0066] Specifically, the target equivalent model corresponding to the target power source type of each target network point is first determined; then the target equivalent model corresponding to each target network point and the network point voltage of each target power source are respectively used to determine each target short-circuit current corresponding to each target network point.

[0067] S13, based on the change trend of the network point voltage of each target network point caused by the iterative change of each target short-circuit current of each target power type under different iteration steps, the nonlinear power supply of each target power type is divided, and iterative calculation is performed in batches, so as to perform fault analysis according to the calculation results of the iterative calculation performed in batches.

[0068] After the target short-circuit currents of the target power types mentioned above are iteratively changed, the change trend of the network point voltage of each target network point caused by the change is an upward trend or a downward trend.

[0069] In the above implementation, when the wind, light, and storage devices are equivalent to nonlinear voltage-controlled current sources, there are also differences between the equivalent nonlinear power supply models of devices of different types and states. When performing iterative calculation of fault current, by grouping the nonlinear power sources participating in the iteration and allowing nonlinear power sources with similar characteristics to participate in the iterative calculation in batches, the convergence of the iterative calculation can be effectively improved, thereby achieving the purpose of improving the efficiency of fault current calculation for large-scale wind, light, and storage connected to the power grid.

[0070] In some embodiments, when performing large-scale fault current calculations for wind, solar, and storage devices connected to the power grid, the calculation process mainly includes first calculating the grid connection point voltage of these devices after a grid failure occurs when the wind, solar, and storage devices exit, and then obtaining the fault current corresponding to the grid connection point voltage based on the nonlinear voltage-controlled current source equivalent model of each wind, solar, and storage device. Then, the grid connection point voltage of these devices after a grid failure occurs when considering the wind, solar, and storage devices is recalculated, and it is continuously iterated until the iterative difference of the grid connection point voltage of the wind, solar, and storage devices is within the threshold.

[0071] Through the above implementation, different equivalent models are set for different types of nonlinear power sources, so that according to the equivalent model corresponding to the nonlinear power source, the short-circuit current of each target network point to which the nonlinear power source belongs is determined, so that the short-circuit current of each network under different types of nonlinear power sources is calculated according to different types of equivalent models. Based on this, by dividing the nonlinear characteristics of the nonlinear voltage-controlled current source model, considering the iteration direction of these nonlinear power sources participating in the iterative calculation under different grid connection point voltages, the nonlinear power sources that have a greater impact on each other during the iterative calculation are divided into batches to participate in the iterative calculation, avoiding the situation where the number of iterations is too high or even non-convergence due to the simultaneous participation of multiple nonlinear power sources with large differences in iteration, thereby improving the convergence and calculation efficiency of the fault current calculation of large-scale wind, light, storage and other equipment connected to the power grid.

[0072] As an implementation mode, in the above step S12, the target equivalent model corresponding to the target power source type of each target network point is used to determine each target short-circuit current corresponding to each target network point, which specifically includes one or more of the following situations.

[0073] First, when it is determined that the nonlinear power supply of the first network point among the multiple network points is a double-fed induction wind turbine, a first short-circuit current of the first network point is determined according to a first equivalent model corresponding to the double-fed induction wind turbine and the network point voltage of the first network point.

[0074] The second method is to determine the second short-circuit current of the second network point according to the second equivalent model corresponding to the permanent magnet direct-drive wind machine and the photovoltaic power supply and the network point voltage of the second network point when it is determined that the nonlinear power supply of the second network point among the multiple network points is a permanent magnet direct-drive wind machine and a photovoltaic power supply.

[0075] The third type is that when it is determined that a nonlinear power supply having a third network point among multiple network points is an energy storage system, if the energy storage system is in a discharging state, a third short-circuit current of the third network point is determined according to the second equivalent model and the network voltage of the third network point.

[0076] A fourth method is to determine that a nonlinear power source having a third network point among multiple network points is an energy storage system, and if the energy storage system is in a charging state, determine a fourth short-circuit current of the third network point according to a third equivalent model corresponding to the energy storage system and the network voltage of the third network point.

[0077] Each target short-circuit current includes one or more of a first short-circuit current, a second short-circuit current, a third short-circuit current and a fourth short-circuit current. The first network point is each target network point where the connected nonlinear power source is a double-fed induction wind turbine; the second network point is each target network point where the connected nonlinear power source is a permanent magnet direct-drive wind turbine and a photovoltaic power source; the third network point is each target network point where the connected nonlinear power source is an energy storage system.

[0078] Based on this, the first short-circuit current includes the grid-connected point orthogonal axis current per unit value of the first grid point, the grid-connected point direct axis current per unit value of the first grid point and the grid-connected point current per unit value of the first grid point, and the first equivalent model is specifically as follows.

[0079]

[0080] Where: I q 1 I is the per unit value of the orthogonal axis current of the first grid point; d 1 I is the per unit value of the direct axis current of the first grid point; w1 1 is the per-unit value of the grid-connected current of the first grid point; θ w1is the phase angle between the grid-connected voltage and current of the first grid point; U L is the positive sequence voltage drop threshold parameter, U T 1 is the grid-connected point voltage per unit value of the first grid point; 2 is the dynamic reactive current proportional coefficient of energy storage; I max is the maximum current of the inverter; U Cb Input threshold value for the crowbar resistor; I N is the rated current of the inverter; Z Cb * is the positive sequence equivalent impedance when the crowbar circuit operates.

[0081] Based on this, the IU curve of the doubly fed wind turbine is drawn, that is, the relationship between the voltage and current of the first grid point, such as Figure 2 As shown, the horizontal axis is the per-unit value of the grid-connected point voltage, the left vertical axis is the per-unit value of the fault current, and the right vertical axis is the fault current phase angle. Assuming that the threshold voltage value of the crowbar resistor is 0.5pu, it can be found that the fault current amplitude does not change much before the crowbar resistor is put into use, but the phase angle changes with the grid-connected point voltage. After the crowbar resistor is put into use, the wind turbine can be regarded as a resistance circuit, and the grid-connected point voltage and the fault current are linearly related.

[0082] In another implementation, the second short-circuit current includes the grid-connected point orthogonal axis current per unit value of the second network point, the grid-connected point direct axis current per unit value of the second network point, and the grid-connected point current per unit value of the second network point; the second equivalent model is specifically as follows.

[0083] The second short-circuit current of the second network point is a short-circuit current or a fault current of a network point where the nonlinear power source is a direct-drive wind turbine and a photovoltaic device.

[0084]

[0085] Among them, I q 2 I is the per unit value of the orthogonal axis current at the grid connection point of the second grid point; d 2 I is the per unit value of the direct-axis current of the second grid point; w2 2 is the per-unit value of the grid-connected current of the second grid point; θ w2 is the phase angle between the grid-connected voltage and current of the second grid point; U L is the positive sequence voltage drop threshold parameter, U T 2 is the grid-connected point voltage per unit value of the second network point; 2 is the dynamic reactive current proportional coefficient of energy storage; I max is the maximum current of the inverter; I N is the rated current of the inverter.

[0086] Based on this, the IU curve of the direct-drive wind turbine and photovoltaic equipment is drawn, that is, the relationship between the voltage and current of the second network point, such as Figure 3 As shown, the horizontal axis is the per-unit value of the grid-connected point voltage, the left vertical axis is the per-unit value of the fault current, and the right vertical axis is the fault current phase angle. When the positive sequence voltage at the equipment grid-connected point drops below 0.9pu, the amplitude of the equipment fault current does not change much, but the phase angle increases as the grid-connected point voltage decreases, indicating that the quadrature-axis component in the fault current continues to increase.

[0087] In another implementation, the third short-circuit current includes the grid-connected point orthogonal axis current per unit value of the third grid point, the grid-connected point direct axis current per unit value of the third grid point, and the grid-connected point current per unit value of the third grid point; the third equivalent model is specifically as follows.

[0088]

[0089] Among them, I q 3 I is the per unit value of the rectangular axis current at the grid connection point of the third grid point; d 3 I is the per unit value of the direct-axis current at the third grid point; w3 3 is the per-unit value of the grid-connected current of the third grid point; θ w3 The phase angle between the voltage and current at the third grid point; U L is the positive sequence voltage drop threshold parameter, U T 3 is the voltage per unit value of the third grid point; 2 is the dynamic reactive current proportional coefficient of energy storage; I max is the maximum current of the inverter; I N is the rated current of the inverter.

[0090] Based on this, the IU curve of the energy storage system in the charging state is drawn, that is, the relationship between the voltage and current of the third network point, such as Figure 4 As shown, the horizontal axis is the per-unit value of the grid connection point voltage, the left vertical axis is the per-unit value of the fault current, and the right vertical axis is the fault current phase angle. When the positive sequence voltage at the grid connection point of the energy storage system drops below 0.9pu, the amplitude of the equipment fault current does not change much, but the absolute value of the phase angle increases with the decrease of the grid connection point voltage, indicating that the quadrature-axis component in the fault current continues to increase.

[0091] As mentioned above, when performing iterative calculation of fault current, there are differences between the equivalent nonlinear voltage-controlled current source models of wind, solar, and storage equipment, which leads to the mutual influence of power sources with different nonlinear characteristics during iteration, increasing the difficulty of convergence.

[0092] Therefore, the nonlinear characteristic division method of nonlinear voltage-controlled current source considering the grid connection point voltage and the electrical connection between nonlinear power sources is adopted, and the wind, light and storage equipment are iteratively calculated in batches during the iterative calculation. The specific process of iterative calculation after using the batch method is as follows:

[0093] For a power grid containing wind, solar, and storage equipment, the node voltage equations of each sequence network can be established according to the power grid structure and component parameters as follows:

[0094]

[0095] Among them, U k That is, the voltage of each bus node in the power grid, I k That is, the injected current of each bus node in the power grid, Z kk That is, the self-impedance and mutual impedance of each bus node in the power grid.

[0096] Before iterative calculation, it is necessary to generate an associated voltage vector reflecting the electrical association relationship of each nonlinear power source in the power grid according to the node impedance matrix Z in formula (4). The specific process is as follows:

[0097] Before iterative calculation, it is necessary to generate an associated voltage vector reflecting the electrical association relationship of each nonlinear power source in the power grid according to the node impedance matrix Z in equation (4). The specific process is as follows:

[0098] First, a unit fault current vector of a single nonlinear power source is generated. The vector has n rows and 1 column. When the bus node number to which the corresponding nonlinear power source is connected is k, the value of the kth row of the vector is 1.

[0099]

[0100] Secondly, the unit vector of formula (5) is substituted into formula (4) as the current to calculate the voltage change of each bus node of the power grid after the nonlinear power source k injects unit current, that is, formula (6).

[0101]

[0102] Third, the formulas (5) and (6) of the first and second steps above are executed for all nonlinear power sources in the power grid to complete the calculation and generation of the associated voltage vectors of all nonlinear power sources.

[0103] Going further, we start iterative calculation of fault current considering wind, solar and storage.

[0104] First, all nonlinear power sources in the grid are removed. When the grid does not contain nonlinear power sources such as wind, light, and storage, the current I injected into each node is a fixed value, and the voltage U of each node can be calculated once using the above node voltage equation. If the kth node is the grid connection point of the nonlinear power source, then the grid connection point voltage U can be calculated based on its grid connection point voltage U k The nonlinear voltage-controlled current source model is used to calculate the nonlinear power supply fault current I of the k-node of the power grid at the first iteration. k1 .

[0105] After calculating the first iteration fault current of all nonlinear power sources in the power grid in turn, the nonlinear power source injection current vector of each bus node is obtained as follows. When the bus is not connected to a nonlinear power source, the value of the corresponding node in the vector is 0.

[0106] ΔI k1 =I k1 -I k Formula (7).

[0107]

[0108] The following calculation is then performed to obtain the voltage U1 of each node of the power grid in the first iteration.

[0109] ΔU k1 =ZΔI k1 Formula (9).

[0110] U1=U+ΔU k1 Formula (10).

[0111] If the nonlinear power supply is not iterated in batches, the iterative calculation is performed continuously according to formula (7) to formula (10). k When it is less than a certain threshold and meets the convergence condition, it stops. kn That is the calculated final fault current of wind, solar and storage equipment.

[0112] If the nonlinear power sources are iteratively calculated in batches, then after each iteration, the fault current change of each wind, light, and storage device at the corresponding grid connection point is calculated according to formula (7) to formula (8). After the fault current change of each nonlinear power source is obtained, it is multiplied by the associated voltage vector of the nonlinear power source obtained by formula (6) to obtain the voltage influence vector of each node voltage in the power grid caused by the fault current change of each nonlinear power source in this iteration.

[0113]

[0114] Where k is the grid-connected bus node number of the nonlinear power source, and p is the number of iterations.

[0115] Then, the voltage influence vectors of all nonlinear power sources are calculated according to formula (11), and the basis for multiple nonlinear power sources to be divided into the same group is defined: Assuming that there are nonlinear power sources on both busbars i and j, their corresponding voltage influence vectors are U ip , U jp , compare whether the positive and negative values ​​of the i-th and j-th rows of the two vectors are consistent. If they are consistent, the two nonlinear power sources can be divided into one group. When the number of power sources increases, the number of compared rows increases accordingly.

[0116] The voltage influence vectors of all nonlinear power sources are traversed in a loop, and the nonlinear power sources are grouped according to the above method. Then, the fault current change vectors are generated for the nonlinear power sources in each group in turn.

[0117]

[0118] In the formula, when there is no nonlinear power supply at the k bus node in the group, the kth row of the vector is 0. If there is a nonlinear power supply at the k bus node, the corresponding fault current change value is calculated according to formula (7) as the value of the kth row of the vector.

[0119] Then, the iterative calculation process from formula (7) to formula (10) is performed on the fault current change vector generated by each group until the ΔU of all nonlinear power sources in the group is k When the convergence condition is met, it stops.

[0120] When all grouped nonlinear power sources have completed the iterative calculation, the iterative calculation of the fault current based on the nonlinear characteristics of the wind, light and storage equipment is completed.

[0121] In one implementation, based on each target short-circuit current of the target power type, a fault analysis is performed on a fault caused by a grid point voltage of each target grid point under a nonlinear power supply of the target power type, including the following steps.

[0122] First, for any nonlinear power supply of a target power supply type, each target short-circuit current of each target network point in a plurality of iteration steps under the nonlinear power supply of the target power supply type is determined.

[0123] Secondly, according to the order of iterative steps, based on the current difference between the target short-circuit currents of each target node obtained at adjacent moments in multiple steps, the voltage difference of the node voltage of each target node before and after the target short-circuit current changes is determined considering the influence of this current difference.

[0124] Thirdly, for any target power supply network point in each target power supply network point, the target power supplies with the same voltage difference variation characteristics are divided into the same group and are iterated together when the short-circuit current is iterated.

[0125] Fourthly, based on the target power supply grouping, the target power supply short-circuit current of each group is iteratively calculated in turn, and the calculation of the network point voltage and short-circuit current of each target network point under the influence of nonlinear power supply is completed to perform fault analysis on each target network point.

[0126] In a specific implementation, each target network point is a site.

[0127] The above method is implemented and verified using the IEEE-33 node (representing different plants or different network points) power grid. The target network points of the power grid are as follows: Figure 5 As shown in the figure, plant 0 is the power supply point of the upper power grid, plant 19, 20, 22, 23, and 24 are wind turbine grid connection points, plant 12, 13, 14, 16, and 17 are photovoltaic grid connection points, and plant 5 and 28 are energy storage grid connection points. Different plants and stations correspond to the grid points one by one.

[0128] Grid faults are set at different locations in the power grid. The number of iterations, time consumption and average deviation results of fault calculation before and after batch iterative calculation using the patented algorithm are shown in Table 1 below.

[0129] In Table 1, after the wind, solar, and storage devices are divided into batches for iterative calculation based on nonlinear characteristics, the calculation takes 311ms, which is 241ms faster than the non-batch iterative calculation, and the error is no more than 0.64%.

[0130] It can be seen that compared with the prior art, the algorithm proposed in this application can significantly reduce the number of iterative calculations while ensuring the correctness of the calculation, improve the calculation efficiency, and reduce the calculation time.

[0131] Table 1

[0132]

[0133] The above nonlinear power supply is also called a nonlinear voltage-controlled current source, the short-circuit current is also called a fault current, and the short-circuit voltage is also called a fault voltage. When calculating the fault current of a traditional synchronous generator, the relationship between the fault current and the fault voltage can be simplified to I = (EU) / X, where I is the current, E is the generator electromotive force, U is the fault voltage, and X is the generator impedance. If the IU characteristic diagram drawn with I and U as the horizontal and vertical axes is a straight line, it is a linear model. However, the IU characteristic diagram of the wind, light, and storage equipment of the present application is a broken line, and the relationship between the current and voltage obtained when calculating the current by a given fault voltage is nonlinear.

[0134] In order to realize the above functions, the fault analysis device based on the grid current includes hardware structures and / or software modules corresponding to the execution of each function. It should be easily appreciated by those skilled in the art that, in combination with the algorithm steps of each example described in the embodiments disclosed herein, the present application can be implemented in the form of hardware or a combination of hardware and computer software. Whether a function is executed in the form of hardware or computer software driving hardware depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of this application.

[0135] The present disclosure also provides a Figure 6 A grid current-based fault analysis device is shown, which is applied to a grid system, which includes a double-fed induction wind turbine, a permanent magnet direct-drive wind turbine, a photovoltaic power supply and an energy storage system. The device includes: a first determination unit 601, a second determination unit 602 and a fault analysis unit 603.

[0136] The first determination unit 601 is used to determine the target power source types to which the nonlinear power sources connected to each target network point among the multiple network points connected to the power grid belong; each target power source type includes one or more of the following: a double-fed induction wind turbine, a permanent magnet direct-drive wind turbine and a photovoltaic power source, and an energy storage system; the double-fed induction wind turbine, the permanent magnet direct-drive wind turbine and the photovoltaic power source and the energy storage system correspond to three different equivalent models respectively. The second determination unit 602 is used to respectively use the target equivalent model corresponding to the target power source type to which each target network point belongs and the network point voltage of the target power source connected to each target network point to determine each target short-circuit current corresponding to each target network point. The fault analysis unit 603 is used to divide the nonlinear power sources of each target power source type based on the change trend of the network point voltage of each target network point caused by the iterative change of each target short-circuit current of each target power source type under different iteration steps, and perform iterative calculations in batches, so as to perform fault analysis according to the calculation results of the iterative calculations in batches.

[0137] In one embodiment, the second determination unit 602 is specifically used to: when it is determined that the nonlinear power supply of a first network point among the multiple network points is a doubly fed induction wind turbine, determine the first short-circuit current of the first network point according to the first equivalent model corresponding to the doubly fed induction wind turbine and the network voltage of the first network point; and / or, when it is determined that the nonlinear power supply of a second network point among the multiple network points is a permanent magnet direct-drive wind turbine and a photovoltaic power source, determine the second short-circuit current of the second network point according to the second equivalent model corresponding to the permanent magnet direct-drive wind turbine and the photovoltaic power source and the network voltage of the second network point; and / or, when it is determined that the nonlinear power supply of a third network point among the multiple network points is an energy storage system, if the energy storage system is in a discharging state, determine the third short-circuit current of the third network point according to the second equivalent model and the network voltage of the third network point; and, if the energy storage system is in a charging state, determine the fourth short-circuit current of the third network point according to the third equivalent model corresponding to the energy storage system and the network voltage of the third network point.

[0138] In another implementation manner, the first short-circuit current includes the grid-connected point orthogonal axis current per unit value of the first grid point, the grid-connected point direct axis current per unit value of the first grid point, and the grid-connected point current per unit value of the first grid point; the first equivalent model is specifically:

[0139]

[0140] Where: I q 1 I is the per unit value of the orthogonal axis current of the first grid point; d 1 I is the per unit value of the direct axis current of the first grid point; w1 1 is the per-unit value of the grid-connected current of the first grid point; θ w1 is the phase angle between the grid-connected voltage and current of the first grid point; U L is the positive sequence voltage drop threshold parameter, U T 1 is the grid-connected point voltage per unit value of the first grid point; 2 is the dynamic reactive current proportional coefficient of energy storage; I max is the maximum current of the inverter; U Cb Input threshold value for the crowbar resistor; I N is the rated current of the inverter; Z Cb * is the positive sequence equivalent impedance when the crowbar circuit operates.

[0141] In another implementation manner, the second short-circuit current includes the grid-connected orthogonal axis current per unit value of the second grid point, the grid-connected axis current per unit value of the second grid point, and the grid-connected point current per unit value of the second grid point; the second equivalent model is specifically:

[0142]

[0143] Among them, I q 2 I is the per unit value of the orthogonal axis current at the grid connection point of the second grid point; d 2 I is the per unit value of the direct-axis current of the second grid point; w2 2 is the per-unit value of the grid-connected current of the second grid point; θ w2 is the phase angle between the grid-connected voltage and current of the second grid point; U L is the positive sequence voltage drop threshold parameter, U T 2 is the grid-connected point voltage per unit value of the second network point; 2 is the dynamic reactive current proportional coefficient of energy storage; I max is the maximum current of the inverter; I N is the rated current of the inverter.

[0144] In another implementation manner, the third short-circuit current includes the grid-connected point orthogonal axis current per unit value of the third grid point, the grid-connected point direct axis current per unit value of the third grid point, and the grid-connected point current per unit value of the third grid point; the third equivalent model is specifically:

[0145]

[0146] Among them, I q 3 I is the per unit value of the rectangular axis current at the grid connection point of the third grid point; d 3 I is the per unit value of the direct-axis current at the third grid point; w3 3 is the per-unit value of the grid-connected current of the third grid point; θ w3 The phase angle between the voltage and current at the third grid point; U L is the positive sequence voltage drop threshold parameter, U T 3 is the voltage per unit value of the third grid point; 2 is the dynamic reactive current proportional coefficient of energy storage; I max is the maximum current of the inverter; I N is the rated current of the inverter.

[0147] In another embodiment, the fault analysis unit 603 is specifically used to: determine, for a nonlinear power supply of any target power supply type, each target short-circuit current of each target network point during multiple iteration steps under the nonlinear power supply of the target power supply type; determine, in accordance with the order of iteration steps, based on the current difference between the target short-circuit currents of each target network point obtained in adjacent steps in the multiple iteration steps, the voltage difference of the network point voltage of each target power supply caused before and after the change of the target short-circuit current; for any target network point among each target network point, divide the target power supplies with the same voltage difference change trend into the same group, and iterate together according to the same group when performing the iterative calculation of the short-circuit current; after completing the grouping of each target power supply, iteratively calculate the target short-circuit current of each group in turn, so as to perform fault analysis according to the calculation results after the iterative calculation is performed in batches according to each group.

[0148] Regarding the device in the above embodiment, the specific manner in which each unit module performs the operation has been described in detail in the embodiment of the method, and will not be elaborated here.

[0149] The embodiment of the present application also provides a computer-readable storage medium, when the instructions in the computer-readable storage medium are executed by a processor of a fault analysis device based on grid current or an electronic device, the fault analysis device based on grid current or the electronic device can perform a fault analysis method based on grid current as described in any of the above possible implementations. And the same technical effect can be achieved, so it will not be repeated here to avoid repetition.

[0150] The embodiment of the present application also provides a computer program product, including a computer program or an instruction, and the computer program or the instruction is executed by a processor as a fault analysis method based on grid current in any possible implementation manner described above. And the same technical effect can be achieved, and to avoid repetition, it will not be repeated here.

[0151] Those skilled in the art will readily appreciate other embodiments of the present application after considering the specification and practicing the invention disclosed herein. The present application is intended to cover any modification, use or adaptation of the present application, which follows the general principles of the present application and includes common knowledge or customary techniques in the art that are not disclosed in the present application. The specification and examples are intended to be exemplary only, and the true scope and spirit of the present application are indicated by the following claims.

[0152] It should be understood that the present application is not limited to the precise structures that have been described above and shown in the drawings, and that various modifications and changes may be made without departing from the scope thereof. The scope of the present application is limited only by the appended claims.

Claims

1. A fault analysis method based on power grid current, characterized in that: Applied to a power grid system, the power grid system includes a double-fed induction wind turbine, a permanent magnet direct-drive wind turbine, a photovoltaic power source and an energy storage system, the method includes: Determine each target power source type to which the nonlinear power source connected to each target network point among multiple network points connected to the power grid belongs; the target power source types include one or more of the following: a doubly-fed induction wind turbine, a permanent magnet direct-drive wind turbine, a photovoltaic power source, and an energy storage system; the doubly-fed induction wind turbine, the permanent magnet direct-drive wind turbine, the photovoltaic power source, and the energy storage system correspond to three different equivalent models respectively; each target network point represents a network point where the power source connected is a nonlinear power source; Determine each target short-circuit current corresponding to each target network point by respectively using the target equivalent model corresponding to the target power source type to which each target network point belongs and the network point voltage of the target power source to which each target network point is connected; Based on the changing trend of the network point voltage of each target network point caused by the iterative change of each target short-circuit current of the target power type under different iteration steps, the nonlinear power supply of each target power type is divided, and iterative calculation is performed in batches, so as to perform fault analysis on each target network point according to the calculation results of the iterative calculation performed in batches.

2. The method according to claim 1, characterized in that The adopting the target equivalent model corresponding to the target power source type to which each target network point belongs to determine each target short-circuit current corresponding to each target network point includes: When it is determined that a nonlinear power supply of a first network point among the multiple network points is a doubly fed induction wind turbine, a first short-circuit current of the first network point is determined according to a first equivalent model corresponding to the doubly fed induction wind turbine and the network voltage of the first network point; and / or, when it is determined that a nonlinear power supply of a second network point among the multiple network points is a permanent magnet direct-drive wind turbine and a photovoltaic power source, a second short-circuit current of the second network point is determined according to a second equivalent model corresponding to the permanent magnet direct-drive wind turbine and the photovoltaic power source and the network voltage of the second network point; and / or, when it is determined that a nonlinear power supply of a third network point among the multiple network points is an energy storage system, if the energy storage system is in a discharging state, a third short-circuit current of the third network point is determined according to the second equivalent model and the network voltage of the third network point; and, if the energy storage system is in a charging state, a fourth short-circuit current of the third network point is determined according to a third equivalent model corresponding to the energy storage system and the network voltage of the third network point.

3. The method according to claim 2, characterized in that The first short-circuit current includes the grid-connected point orthogonal axis current per unit value of the first network point, the grid-connected point direct axis current per unit value of the first network point, and the grid-connected point current per unit value of the first network point; the first equivalent model is specifically: Where: I q 1 I is the per unit value of the orthogonal axis current of the first grid point; d 1 I is the per unit value of the direct axis current of the first grid point; w1 1 is the per-unit value of the grid-connected current of the first grid point; θ w1 is the phase angle between the grid-connected voltage and current of the first grid point; U L is the positive sequence voltage drop threshold parameter, U T 1 is the grid-connected point voltage per unit value of the first grid point; 2 is the dynamic reactive current proportional coefficient of energy storage; I max is the maximum current of the inverter; U Cb Input threshold value for the crowbar resistor; I N is the rated current of the inverter; Z Cb * is the positive sequence equivalent impedance when the crowbar circuit operates.

4. The method according to claim 2, characterized in that: The second short-circuit current includes the grid-connected orthogonal axis current per unit value of the second network point, the grid-connected direct axis current per unit value of the second network point, and the grid-connected current per unit value of the second network point; the second equivalent model is specifically: Among them, I q 2 I is the per unit value of the orthogonal axis current at the grid connection point of the second grid point; d 2 I is the per unit value of the direct-axis current of the second grid point; w2 2 is the per-unit value of the grid-connected current of the second grid point; θ w2 is the phase angle between the grid-connected voltage and current of the second grid point; U L is the positive sequence voltage drop threshold parameter, U T 2 is the grid-connected point voltage per unit value of the second network point; 2 is the dynamic reactive current proportional coefficient of energy storage; I max is the maximum current of the inverter; I N is the rated current of the inverter.

5. The method according to claim 2, characterized in that: The third short-circuit current includes the grid-connected point orthogonal axis current per unit value of the third grid point, the grid-connected point direct axis current per unit value of the third grid point, and the grid-connected point current per unit value of the third grid point; the third equivalent model is specifically: Among them, I q 3 I is the per unit value of the rectangular axis current at the grid connection point of the third grid point; d 3 I is the per unit value of the direct-axis current at the third grid point; w3 3 is the per-unit value of the grid-connected current of the third grid point; θ w3 The phase angle between the voltage and current at the third grid point; U L is the positive sequence voltage drop threshold parameter, U T 3 is the voltage per unit value of the third grid point; 2 is the dynamic reactive current proportional coefficient of energy storage; I max is the maximum current of the inverter; I N is the rated current of the inverter.

6. The method according to any one of claims 1 to 5, characterized in that The change of the network point voltage of each target network point caused by the iterative change of each target short-circuit current of the target power type in different iteration steps, dividing the nonlinear power supply of each target power type, and performing iterative calculation in batches, so as to perform fault analysis on each target network point according to the calculation results of the iterative calculation in batches, includes: For any nonlinear power supply of the target power supply type, determining each target short-circuit current of each target network point during multiple iteration steps under the nonlinear power supply of the target power supply type; Determine, in an iterative step sequence, a voltage difference between the network point voltages of each target power source caused before and after the target short-circuit current changes based on the current differences between the target short-circuit currents of each target network point obtained in adjacent steps of the multiple iterative steps; For any target network point among the target network points, the target power sources with the same voltage difference change trend are divided into the same group, and when performing the short-circuit current iterative calculation, they are iterated together according to the same group; After the target power sources are grouped, the target short-circuit currents of the groups are iteratively calculated in turn, so as to perform fault analysis according to the calculation results after the iterative calculations are performed in batches according to the groups.

7. A fault analysis device based on power grid current, characterized in that: Applied to a power grid system, the power grid system includes a double-fed induction wind turbine, a permanent magnet direct-drive wind turbine, a photovoltaic power source and an energy storage system, and the device includes: The first determination unit is used to determine each target power source type to which the nonlinear power source connected to each target network point among multiple network points connected to the power grid belongs; the target power source types include one or more of the following: a double-fed induction wind turbine, a permanent magnet direct-drive wind turbine, a photovoltaic power source, and an energy storage system; the double-fed induction wind turbine, the permanent magnet direct-drive wind turbine, the photovoltaic power source, and the energy storage system correspond to three different equivalent models respectively; each target network point represents a network point where the power source connected is a nonlinear power source; A second determination unit is used to determine each target short-circuit current corresponding to each target network point by respectively using a target equivalent model corresponding to a target power source type to which each target network point belongs and a network point voltage of a target power source to which each target network point is connected; A fault analysis unit is used to divide the nonlinear power supplies of each target power type based on the changes in the network point voltage of each target network point caused by the iterative changes of each target short-circuit current of the target power type in different iteration steps, and perform iterative calculations in batches, so as to perform fault analysis according to the calculation results of the iterative calculations performed in batches.

8. The device according to claim 7, characterized in that The second determining unit is specifically configured to: When it is determined that a nonlinear power supply at a first network point among the multiple network points is a doubly fed induction wind turbine, a first short-circuit current of the first network point is determined according to a first equivalent model corresponding to the doubly fed induction wind turbine and the network voltage of the first network point; and / or, when it is determined that a nonlinear power supply at a second network point among the multiple network points is a permanent magnet direct-drive wind turbine and a photovoltaic power supply, a second short-circuit current of the second network point is determined according to a second equivalent model corresponding to the permanent magnet direct-drive wind turbine and the photovoltaic power supply and the network voltage of the second network point; and / or, when it is determined that a nonlinear power supply at a third network point among the multiple network points is an energy storage system, if the energy storage system is in a discharging state, a third short-circuit current of the third network point is determined according to the second equivalent model and the network voltage of the third network point; And, if the energy storage system is in a charging state, a fourth short-circuit current of the third network point is determined according to a third equivalent model corresponding to the energy storage system and a network point voltage of the third network point.

9. The device according to claim 7 or 8, characterized in that The fault analysis unit is specifically used for: For any nonlinear power supply of the target power supply type, determining each target short-circuit current of each target network point during multiple iteration steps under the nonlinear power supply of the target power supply type; Determine, in an iterative step sequence, a voltage difference between the network point voltages of each target power source caused before and after the target short-circuit current changes based on the current differences between the target short-circuit currents of each target network point obtained in adjacent steps of the multiple iterative steps; For any target network point among the target network points, the target power sources with the same voltage difference change trend are divided into the same group, and when performing the short-circuit current iterative calculation, they are iterated together according to the same group; After the target power sources are grouped, the target short-circuit currents of the groups are iteratively calculated in turn, so as to perform fault analysis according to the calculation results after the iterative calculations are performed in batches according to the groups.

10. A power grid system, characterized in that: The power grid system includes a double-fed induction wind turbine, a permanent magnet direct-drive wind turbine, a photovoltaic power source and an energy storage system, and is configured to execute the fault analysis method based on power grid current as described in any one of claims 1 to 6.

Images