Island detection method and system for energy storage inverter

Abstract

The present invention discloses an island detection method and system for an energy storage inverter, and the island detection method for the energy storage inverter includes: S1: obtaining the average frequency and effective value of the grid voltage of the energy storage inverter within a first preset time; S2: obtaining an instantaneous sampling value of the grid voltage once every preset period within a second preset time, and calculating the total error of the first grid voltage within the second preset time; S3: performing island disturbance on the energy storage inverter, and obtaining an instantaneous sampling value of the grid voltage once every preset period within a third preset time, and calculating the total error of the second grid voltage within the third preset time; judging whether the absolute value of the difference between the total error of the second grid voltage and the total error of the first grid voltage is greater than the absolute value of the island identification amount, and if so, judging that the island occurs. The present invention realizes the improvement of the accuracy of island detection while reducing the impact of active island detection on grid quality, and the control is simple.

Description

Technical Field

[0001] The present invention relates to the technical field of energy storage equipment, and in particular to an island detection method and system for an energy storage inverter. Background Art

[0002] The islanding effect refers to the phenomenon that when the photovoltaic grid-connected power generation system installed at each user fails to detect the power outage in time and cannot quickly disconnect itself from the mains network when it stops working due to a fault accident or power outage maintenance, a self-sufficient power supply island phenomenon that the power company cannot control is formed, where the photovoltaic grid-connected power generation system supplies power to the surrounding loads. When the islanding effect occurs, it may cause safety hazards to the distribution equipment and end users. Therefore, it is very necessary to detect whether the equipment may have the islanding effect.

[0003] Among them, the active island detection method is to control the inverter to make its output power, frequency or phase have certain disturbances; the passive island detection method is to detect the island effect by using the changes in the voltage, frequency, phase or harmonics at the inverter output when the power grid is off. Among them, the existing active island detection method of energy storage inverter is to be implemented through harmonic injection and other methods. On the one hand, there is a problem of complex control, and on the other hand, there is also a problem of damaging the output power quality.

[0004] The disclosure of the above background technology content is only used to assist in understanding the concept and technical solution of the present invention. It does not necessarily belong to the prior art of this patent application. In the absence of clear evidence that the above content has been disclosed on the filing date of this patent application, the above background technology should not be used to evaluate the novelty and creativity of the present application. Summary of the invention

[0005] In order to solve the above technical problems, the present invention proposes an island detection method and system for an energy storage inverter, which can improve the accuracy of island detection while reducing the impact of active island detection on power grid quality, and has simple control.

[0006] In order to achieve the above object, the present invention proposes the following technical solutions:

[0007] In a first aspect, the present invention discloses an island detection method for an energy storage inverter, comprising the following steps:

[0008] S1: Obtaining the average frequency of the grid voltage and the effective value of the grid voltage of the energy storage inverter within a first preset time;

[0009] S2: acquiring an instantaneous sampling value of the grid voltage of the energy storage inverter once every preset period within a second preset time, and calculating a total error of the first grid voltage within the second preset time according to an average frequency of the grid voltage, an effective value of the grid voltage and all instantaneous sampling values ​​of the grid voltage acquired within the second preset time;

[0010] S3: Performing islanding disturbance on the energy storage inverter, and obtaining an instantaneous sampling value of the grid voltage of the energy storage inverter with islanding disturbance once every preset period within a third preset time, and calculating a second grid voltage total error within the third preset time according to an average frequency of the grid voltage, an effective value of the grid voltage and all instantaneous sampling values ​​of the grid voltage obtained within the third preset time; and then determining whether the absolute value of the difference between the second grid voltage total error and the first grid voltage total error is greater than the absolute value of the islanding identification amount, and if so, determining that an islanding occurs.

[0011] Preferably, step S1 comprises:

[0012] S11: Grid phase locking, tracking the current grid phase;

[0013] S12: Obtaining an average frequency of the grid voltage of the energy storage inverter within a first preset time, and setting each grid voltage cycle to consist of points with the same time interval, and obtaining the preset cycle according to the average frequency of the grid voltage and the number of points;

[0014] S13: performing average filtering on the grid voltage of the energy storage inverter within the first preset time, and obtaining an effective value of the grid voltage after the average filtering.

[0015] Preferably, an island detection is completed within a preset total cycle, and the preset total cycle includes the first preset time, the second preset time and the third preset time which are sequentially continuous with each other.

[0016] Preferably, the moment when the instantaneous sampling value of the grid voltage of the energy storage inverter is obtained for the first time within the second preset time is the moment when the first phase-locked voltage angle is zero after the starting time of the second preset time, and the moment when the instantaneous sampling value of the grid voltage of the energy storage inverter with island disturbance is obtained for the first time within the third preset time is the moment when the first phase-locked voltage angle is zero after the starting time of the third preset time.

[0017] Preferably, in step S2, calculating the total error of the first grid voltage within the second preset time according to the average frequency of the grid voltage, the effective value of the grid voltage and all instantaneous sampling values ​​of the grid voltage acquired within the second preset time includes:

[0018] Calculating a first grid voltage sub-error according to the average frequency of the grid voltage, the effective value of the grid voltage and each instantaneous sampling value of the grid voltage acquired within the second preset time;

[0019] All first grid voltage sub-errors calculated within the second preset time are added together to obtain a total first grid voltage error within the second preset time.

[0020] Preferably, in step S3, calculating the second grid voltage total error within the third preset time according to the average frequency of the grid voltage, the grid voltage effective value and all instantaneous sampling values ​​of the grid voltage acquired within the third preset time comprises:

[0021] Calculating a second grid voltage sub-error according to the average frequency of the grid voltage, the effective value of the grid voltage and each instantaneous sampling value of the grid voltage acquired within the third preset time;

[0022] All second grid voltage sub-errors calculated within the third preset time are added together to obtain a second grid voltage total error within the third preset time.

[0023] Preferably, in step S2, the total error of the first grid voltage within the second preset time calculated according to the average frequency of the grid voltage, the effective value of the grid voltage and all instantaneous sampling values ​​of the grid voltage acquired within the second preset time includes:

[0024] The total number of instantaneous sampling values ​​of the grid voltage obtained within the second preset time is p ,when p / n When is an integer, the total error of the first grid voltage is:

[0025]

[0026] when p / n When is a non-integer, the total error of the first grid voltage is:

[0027]

[0028] In the formula, S n represents the total error of the first grid voltage, V R represents the effective value of the grid voltage, n Indicates the number of preset cycles contained in each grid voltage cycle, grid voltage cycle=1 / average frequency of grid voltage, V xIndicates the first x The instantaneous sampling value of the grid voltage of the energy storage inverter obtained for the first time, x The value is 1~ p , p Indicates the total number of instantaneous sampling values ​​of the grid voltage obtained within the second preset time; m express p / n The floor value of .

[0029] Preferably, in step S3, the total error of the second grid voltage within the third preset time calculated according to the average frequency of the grid voltage, the effective value of the grid voltage and all instantaneous sampling values ​​of the grid voltage acquired within the third preset time includes:

[0030] The total number of instantaneous sampling values ​​of the grid voltage obtained within the third preset time is q ,when q / n When is an integer, the total error of the second grid voltage is:

[0031]

[0032] when q / n When is a non-integer, the total error of the second grid voltage is:

[0033]

[0034] In the formula, represents the total error of the second grid voltage, V R represents the effective value of the grid voltage, n Indicates the number of preset cycles contained in each grid voltage cycle, grid voltage cycle=1 / average frequency of grid voltage, V y Indicates the first y The instantaneous sampling value of the grid voltage of the energy storage inverter obtained by the island disturbance, y The value is 1~ q , q represents the total number of instantaneous sampling values ​​of the grid voltage obtained within the third preset time; s express q / n The floor value of .

[0035] Preferably, performing islanding disturbance on the energy storage inverter in step S3 specifically includes: performing frequency disturbance on the energy storage inverter, and the frequency disturbance amount of the energy storage inverter is less than or equal to 0.18 Hz.

[0036] In a second aspect, the present invention discloses an island detection system for an energy storage inverter, including a state recognition module, an error accumulation module, a new error accumulation and island determination module, wherein:

[0037] The state identification module is used to obtain the average frequency of the grid voltage and the effective value of the grid voltage of the energy storage inverter within a first preset time;

[0038] The error accumulation module is used to obtain the instantaneous sampling value of the grid voltage of the energy storage inverter once every preset period within the second preset time, and calculate the total error of the first grid voltage within the second preset time according to the average frequency of the grid voltage, the effective value of the grid voltage and all the instantaneous sampling values ​​of the grid voltage obtained within the second preset time;

[0039] The new error accumulation and island determination module is used to perform island disturbance on the energy storage inverter, and obtain the instantaneous sampling value of the grid voltage of the energy storage inverter with island disturbance once every preset period within a third preset time, and calculate the second grid voltage total error within the third preset time according to the average frequency of the grid voltage, the effective value of the grid voltage and all the instantaneous sampling values ​​of the grid voltage obtained within the third preset time; then determine whether the absolute value of the difference between the second grid voltage total error and the first grid voltage total error is greater than the absolute value of the island identification amount, and if so, determine that islanding occurs.

[0040] In a third aspect, the present invention discloses a computer-readable storage medium, in which a computer program is stored, wherein the computer program is configured to be executable by a processor to execute the island detection method for the energy storage inverter described in the first aspect.

[0041] Compared with the prior art, the beneficial effects of the present invention are as follows: the islanding detection method of the energy storage inverter proposed in the present invention, wherein the error of the grid voltage before and after the islanding disturbance is processed by multi-sample accumulation, so that the result of the islanding disturbance can be amplified, thereby achieving the effect of obtaining a more obvious judgment basis through a smaller islanding disturbance amount, and a smaller islanding disturbance amount means lower pollution to the grid, therefore, the present invention achieves the improvement of the accuracy of islanding detection while reducing the impact of active islanding detection on the grid quality; and the error accumulation comparison method proposed in the present invention is simpler to control than when performing islanding detection by methods such as harmonic injection.

[0042] In a further embodiment, the present invention also has the following beneficial effects:

[0043] (1) The effective value of the grid voltage obtained within the first preset time is obtained through average filtering, which can further improve the accuracy of island detection.

[0044] (2) The time for first acquiring the instantaneous sampling value of the grid voltage of the energy storage inverter is constrained within the second preset time and the third preset time, respectively, so as to reduce the error caused by the difference in the starting state and further improve the accuracy of island detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 It is a flow chart of an island detection method for an energy storage inverter disclosed in Embodiment 1 of the present invention;

[0046] Figure 2 It is the time period included in an island detection;

[0047] Figure 3 This is a flowchart of calling modules during an island detection process. DETAILED DESCRIPTION

[0048] The following is a detailed description of the embodiments of the present invention. It should be emphasized that the following description is only exemplary and is not intended to limit the scope and application of the present invention.

[0049] It should be noted that when a component is referred to as being "fixed to" or "disposed on" another component, it can be directly on the other component or indirectly on the other component. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or indirectly connected to the other element. In addition, connection can be used for both fixing and circuit / signal communication.

[0050] It should be understood that the terms "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing the embodiments of the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0051] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the embodiments of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0052] like Figure 1 As shown, Embodiment 1 of the present invention discloses an island detection method for an energy storage inverter, comprising the following steps:

[0053] S1: Obtaining the average frequency of the grid voltage and the effective value of the grid voltage of the energy storage inverter within a first preset time;

[0054] Among them, an island detection is completed within a preset total cycle, and a preset total cycle includes a first preset time, a second preset time, and a third preset time that are sequentially continuous. Specifically, the entire island detection method uses time T as a cycle, and the selection of T is related to the grid standard used by the energy storage inverter. For example, if the corresponding grid standard requires that an island be detected within 5 seconds after the grid is lost, then T must be less than or equal to 5 seconds. For example, in a specific example, T is 2.5 seconds; in this solution, T is refined into a first preset time (state recognition time), a second preset time (error accumulation time), and a third preset time (new error accumulation and island determination time). Figure 2 In a further specific example, the total time of the island detection method is 2.5 seconds, the first preset time (state identification time) is 0.5 seconds, the second preset time (error accumulation time) is 1 second, and the third preset time (new error accumulation and island determination time) is 1 second; wherein the second preset time and the third preset time may be the same or different.

[0055] Specifically, step S1 includes:

[0056] S11: Grid phase locking, tracking the current grid phase;

[0057] S12: Obtaining the average frequency of the grid voltage of the energy storage inverter within the first preset time, and setting each grid voltage cycle to consist of points with the same time interval, and obtaining a preset cycle according to the average frequency and number of points of the grid voltage;

[0058] The relationship between the preset period, the average frequency and the number of points is: 1 / average frequency = number of points × preset period. In a specific example, the number of points is set to 400 points and the average frequency is 50 Hz. Substituting into the above relationship, the preset period can be obtained to be 50 μs. In other examples, the number of points can also be set to other values ​​such as 200, 300, 500, etc.

[0059] During the specific execution process, the preset period is assigned to the timing interrupt period of the timer.

[0060] S13: Perform average filtering on the grid voltage of the energy storage inverter within the first preset time, and obtain the effective value of the grid voltage after average filtering. The effective value of the grid voltage is V R .

[0061] S2: obtaining an instantaneous grid voltage sampling value of the energy storage inverter once every preset period within the second preset time, and calculating a total error of the first grid voltage within the second preset time according to an average frequency of the grid voltage, an effective value of the grid voltage and all instantaneous grid voltage sampling values ​​obtained within the second preset time;

[0062] Specifically, step S2 includes:

[0063] S21: acquiring an instantaneous sampling value of the grid voltage of the energy storage inverter once every preset period within a second preset time;

[0064] The moment of first acquiring the instantaneous sampling value of the grid voltage of the energy storage inverter within the second preset time is the moment when the first phase-locked voltage angle is zero after the start moment of the second preset time.

[0065] After entering this time period (second preset time), the error is accumulated from the moment when the first phase-locked voltage angle is zero, that is, the total time of the accumulated error is from the moment when the first phase-locked voltage angle is zero after the start time of the second preset time to the end time of the second preset time. In a specific example, the second preset time (error accumulation time) is 1 second, and the total time of the accumulated error is 950ms.

[0066] During the specific execution process, the instantaneous sampling value of the grid voltage is read once at each timer interruption. V x , V x Indicates the first x The instantaneous sampling value of the grid voltage of the energy storage inverter obtained this time.

[0067] S22: calculating a total error of the first grid voltage within the second preset time according to the average frequency of the grid voltage, the effective value of the grid voltage and all instantaneous sampling values ​​of the grid voltage acquired within the second preset time;

[0068] Step S22 specifically includes:

[0069] S221: Calculate a first grid voltage sub-error according to an average frequency of the grid voltage, an effective value of the grid voltage, and instantaneous sampling values ​​of each grid voltage acquired within a second preset time;

[0070] Among them, the first grid voltage sub-error is: , where V x Indicates the first x The instantaneous sampling value of the grid voltage of the energy storage inverter obtained for the first time, V R Indicates the effective value of the grid voltage. nrepresents the number of points, where x The instantaneous sampling value of the grid voltage of the energy storage inverter obtained for the first time is the first value of a grid voltage cycle. b point (i.e. b The value is obtained by the timing interrupt cycle.

[0071] S222: Add all first grid voltage sub-errors calculated within the second preset time to obtain a first grid voltage total error within the second preset time.

[0072] Among them, the total number of instantaneous sampling values ​​of the grid voltage obtained within the second preset time is p .

[0073] when p / n When is an integer, the total error of the first grid voltage is:

[0074]

[0075] when p / n When is a non-integer, the total error of the first grid voltage is:

[0076]

[0077] In the formula, S n represents the total error of the first grid voltage, V R Indicates the effective value of the grid voltage. n Indicates the number of preset cycles contained in each grid voltage cycle, grid voltage cycle = 1 / average frequency of grid voltage, V x Indicates the first x The instantaneous sampling value of the grid voltage of the energy storage inverter obtained for the first time, x The value is 1~ p , p Indicates the total number of instantaneous sampling values ​​of the grid voltage obtained within the second preset time; m express p / n The rounded-down value of is the number of grid voltage cycles contained in the total time of the accumulated error in the second preset time.

[0078] It can be seen from the above first total grid voltage error that the total time of the accumulated error in the second preset time contains multiple grid voltage cycles, among which a The first grid voltage error obtained from a grid voltage cycle is:

[0079]

[0080] S3: Perform islanding disturbance on the energy storage inverter, and obtain the instantaneous sampling value of the grid voltage of the energy storage inverter with islanding disturbance once every preset period within the third preset time, and calculate the total error of the second grid voltage within the third preset time according to the average frequency of the grid voltage, the effective value of the grid voltage and all the instantaneous sampling values ​​of the grid voltage obtained within the third preset time; determine whether the absolute value of the difference between the total error of the second grid voltage and the total error of the first grid voltage is greater than the absolute value of the islanding identification amount, and if so, determine that islanding occurs.

[0081] Specifically, step S3 includes:

[0082] S31: perform island disturbance on the energy storage inverter;

[0083] The active island disturbance used in this embodiment is to perform frequency disturbance on the energy storage inverter. There are two main grid frequency standards in the world. One is f = 50Hz ; the other is f = 60Hz Among them, the frequency disturbance of the energy storage inverter is less than or equal to 0.36% f， Taking the grid frequency as 50 Hz as an example, the frequency disturbance amount is less than or equal to 0.18 Hz. For example, in a specific example, the frequency disturbance amount is 0.15 Hz.

[0084] S32: acquiring an instantaneous sampling value of the grid voltage of the energy storage inverter with islanding disturbance every preset period within a third preset time,

[0085] The moment of first acquiring the instantaneous sampling value of the grid voltage of the energy storage inverter within the third preset time is the moment when the first phase-locked voltage angle is zero after the start moment of the third preset time.

[0086] After entering this time period (third preset time), new errors are accumulated from the moment when the first phase-locked voltage angle is zero, that is, the total time for accumulating new errors is from the moment when the first phase-locked voltage angle is zero after the start time of the third preset time to the end time of the third preset time. In a specific example, the third preset time (new error accumulation and island determination time) is 1 second, and the total time for accumulating new errors is 950ms.

[0087] During the specific execution process, the instantaneous sampling value of the grid voltage is read once at each timer interruption. , Indicates the first y The instantaneous sampling value of the grid voltage of the energy storage inverter obtained this time.

[0088] S33: calculating a total error of the second grid voltage within the third preset time according to the average frequency of the grid voltage, the effective value of the grid voltage and all instantaneous sampling values ​​of the grid voltage acquired within the third preset time;

[0089] Step S33 specifically includes:

[0090] S331: Calculate a second grid voltage sub-error according to the average frequency of the grid voltage, the effective value of the grid voltage and each grid voltage instantaneous sampling value acquired within a third preset time;

[0091] Among them, the first grid voltage sub-error is: , where Indicates the first y The instantaneous sampling value of the grid voltage of the energy storage inverter with island disturbance is obtained. V R Indicates the effective value of the grid voltage. n represents the number of points, where y The instantaneous sampling value of the grid voltage of the energy storage inverter obtained for the first time is the first value of a grid voltage cycle. d point (i.e. d The value is obtained by the timing interrupt cycle.

[0092] S332: Adding all the second grid voltage sub-errors calculated within the third preset time to obtain a total second grid voltage error within the third preset time;

[0093] The total number of instantaneous grid voltage sampling values ​​obtained within the third preset time is q ,when q / n When is an integer, the total error of the second grid voltage is:

[0094]

[0095] Among them, when q / n When is a non-integer, the total error of the second grid voltage is:

[0096]

[0097] In the formula, represents the total error of the second grid voltage, V R Indicates the effective value of the grid voltage. n Indicates the number of preset cycles contained in each grid voltage cycle, grid voltage cycle = 1 / average frequency of grid voltage, Indicates the first yThe instantaneous sampling value of the grid voltage of the energy storage inverter with island disturbance is obtained. y The value is 1~ q , q Indicates the total number of instantaneous sampling values ​​of the grid voltage obtained within the third preset time; s express q / n The rounded-down value of is the number of grid voltage cycles included in the total time of accumulating new errors in the third preset time.

[0098] It can be seen from the above second total grid voltage error that the total time of the accumulated error in the third preset time contains multiple grid voltage cycles, among which c The first grid voltage error obtained from a grid voltage cycle is:

[0099]

[0100] S34: Determine whether the absolute value of the difference between the second grid voltage total error and the first grid voltage total error is greater than the absolute value of the island identification amount; if so, determine that an island occurs.

[0101] Among them, the island identification amount determines the size of the active island frequency disturbance, and the size of the frequency disturbance amount determines the degree of damage to the performance quality of the power grid by the island detection method, and also affects the accuracy of the island detection. In a specific embodiment, the island identification amount can be obtained by experimental testing. For example, in a specific example, the island identification amount is tested to be 100000V. If the absolute value of the difference between the total error of the second power grid voltage and the total error of the first power grid voltage is greater than 100000V, it is determined that the island occurs, and the system executes the action of disconnecting from the power grid; if the absolute value of the difference between the total error of the second power grid voltage and the total error of the first power grid voltage is less than or equal to 100000V, the island disturbance is exited, and the next cycle is entered to re-execute the steps of the island detection method. In the specific execution process, after the island detection method is executed in each cycle, the relevant process quantity can be cleared, and the active island frequency disturbance control is also stopped.

[0102] The island detection method disclosed in the first embodiment of the present invention is divided into three time periods within a cycle (i.e., a first preset time, a second preset time, and a third preset time that are sequentially continuous with each other), wherein the work completed within the first time period (state recognition time) ensures the accuracy of the grid voltage, frequency, and timer time used in the method, and ensures the accuracy of the island detection; the second time period (error accumulation time) and the third time period (new error accumulation and island determination time) perform multi-sample accumulation processing on the error, and achieves the purpose of amplifying the island disturbance result by performing error accumulation on the disturbed signal within a period of time, and finally achieves the effect of obtaining a more obvious judgment basis through a smaller frequency disturbance, thereby reducing the impact of active island detection on the grid quality while improving the accuracy of island detection; and the error accumulation comparison method proposed in the present invention is simpler to control than the harmonic injection method and other methods for island detection.

[0103] Embodiment 2 of the present invention discloses an island detection system for an energy storage inverter, including a state recognition processing module, an error accumulation processing module, and a new error accumulation and island determination processing module, wherein:

[0104] The state identification processing module is used to obtain the average frequency and effective value of the grid voltage of the energy storage inverter within the first preset time; further, the state identification module is used to execute the specific process steps in step S1 of the island detection method for the energy storage inverter in the above-mentioned embodiment 1, which will not be repeated here.

[0105] The error accumulation processing module is used to obtain the instantaneous sampling value of the grid voltage of the energy storage inverter once every preset period within the second preset time, and calculate the total error of the first grid voltage within the second preset time according to the average frequency of the grid voltage, the effective value of the grid voltage and all the instantaneous sampling values ​​of the grid voltage obtained within the second preset time; further, the error accumulation module is used to execute the specific process steps in step S2 of the island detection method for the energy storage inverter in the above-mentioned embodiment 1, which will not be repeated here.

[0106] The new error accumulation and island determination processing module is used to perform island disturbance on the energy storage inverter, and obtain the instantaneous sampling value of the grid voltage of the energy storage inverter with island disturbance once every preset period within the third preset time, and calculate the second grid voltage total error within the third preset time according to the average frequency of the grid voltage, the effective value of the grid voltage and all the instantaneous sampling values ​​of the grid voltage obtained within the third preset time; then judge whether the absolute value of the difference between the second grid voltage total error and the first grid voltage total error is greater than the absolute value of the island identification amount, and if so, judge that the island occurs; further, the new error accumulation and island determination module is used to execute the specific process steps in step S3 of the island detection method for the energy storage inverter in the above-mentioned embodiment 1, which will not be repeated here.

[0107] When performing island detection on the energy storage inverter, the above modules can be called for processing according to the time period at the current moment. Within the preset total cycle of an island detection, the first preset time, the second preset time and the third preset time are sequentially continuous with each other, wherein the first preset time corresponds to the state recognition time period, the second preset time corresponds to the error accumulation time period, and the third preset time corresponds to the new error accumulation and island determination time period. The processing flow of calling each module (including the state recognition processing module, the error accumulation processing module, the new error accumulation and island determination processing module) is as follows: Figure 3 shown.

[0108] The island detection system of the energy storage inverter can not only reduce the damage of active island disturbance to the power performance quality, but also accurately identify the island effect in the system and reduce the safety hazards of island effect to distribution equipment and end users.

[0109] Embodiment 3 of the present invention discloses a computer-readable storage medium, in which a computer program is stored. The computer program is configured to be executable by a processor to execute the steps of the islanding detection method for the energy storage inverter in the above-mentioned embodiment 1.

[0110] Optionally, the storage medium may include but is not limited to: a USB flash drive, a read-only memory (ROM), a random access memory (RAM), a mobile hard disk, a magnetic disk or an optical disk, and other media that can store computer programs.

[0111] The background section of the present invention may contain background information about the problem or environment of the present invention, rather than describing the prior art by others. Therefore, the content contained in the background section is not an admission by the applicant that the prior art is available.

[0112] The above content is a further detailed description of the present invention in combination with specific / preferred embodiments, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, without departing from the concept of the present invention, it can also make several substitutions or modifications to these described embodiments, and these substitutions or modifications should be regarded as belonging to the protection scope of the present invention. In the description of this specification, the description of reference terms "an embodiment", "some embodiments", "preferred embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in combination with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily target the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, in the absence of mutual contradiction, the technical personnel in this field can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples. Although the embodiments of the present invention and their advantages have been described in detail, it should be understood that various changes, substitutions and modifications can be made herein without departing from the scope defined by the attached claims.

Claims

1. A method for detecting an islanding of an energy storage inverter, characterized in that: The following steps are involved: S1: Obtaining the average frequency of the grid voltage and the effective value of the grid voltage of the energy storage inverter within a first preset time; S2: acquiring an instantaneous sampling value of the grid voltage of the energy storage inverter once every preset period within a second preset time, and calculating a total error of the first grid voltage within the second preset time according to an average frequency of the grid voltage, an effective value of the grid voltage and all instantaneous sampling values ​​of the grid voltage acquired within the second preset time; S3: performing islanding disturbance on the energy storage inverter, and obtaining an instantaneous sampling value of the grid voltage of the energy storage inverter during the islanding disturbance every preset period within a third preset time, and calculating a second grid voltage total error within the third preset time according to an average frequency of the grid voltage, an effective value of the grid voltage, and all instantaneous sampling values ​​of the grid voltage obtained within the third preset time; and then determining whether the absolute value of the difference between the second grid voltage total error and the first grid voltage total error is greater than the absolute value of the islanding identification amount, and if so, determining that an islanding occurs; Wherein, step S1 comprises: S11: Grid phase locking, tracking the current grid phase; S12: Obtaining an average frequency of the grid voltage of the energy storage inverter within a first preset time, and setting each grid voltage cycle to consist of points with the same time interval, and obtaining the preset cycle according to the average frequency of the grid voltage and the number of points; S13: performing average filtering on the grid voltage of the energy storage inverter within the first preset time, and obtaining an effective value of the grid voltage after the average filtering; In step S2, calculating the total error of the first grid voltage within the second preset time according to the average frequency of the grid voltage, the effective value of the grid voltage and all instantaneous sampling values ​​of the grid voltage acquired within the second preset time includes: Calculating a first grid voltage sub-error according to the average frequency of the grid voltage, the effective value of the grid voltage and each instantaneous sampling value of the grid voltage acquired within the second preset time; Adding all first grid voltage sub-errors calculated within the second preset time to obtain a total first grid voltage error within the second preset time; In step S3, calculating the total error of the second grid voltage within the third preset time according to the average frequency of the grid voltage, the effective value of the grid voltage and all instantaneous sampling values ​​of the grid voltage acquired within the third preset time includes: Calculating a second grid voltage sub-error according to the average frequency of the grid voltage, the effective value of the grid voltage and each instantaneous sampling value of the grid voltage acquired within the third preset time; All second grid voltage sub-errors calculated within the third preset time are added together to obtain a second grid voltage total error within the third preset time.

2. The island detection method for energy storage inverter according to claim 1, characterized in that: An island detection is completed once within a preset total cycle, and the preset total cycle includes the first preset time, the second preset time and the third preset time which are sequentially continuous with each other.

3. The island detection method for energy storage inverter according to claim 2, characterized in that: The moment when the instantaneous sampling value of the grid voltage of the energy storage inverter is obtained for the first time within the second preset time is the moment when the first phase-locked voltage angle is zero after the starting time of the second preset time, and the moment when the instantaneous sampling value of the grid voltage of the energy storage inverter with island disturbance is obtained for the first time within the third preset time is the moment when the first phase-locked voltage angle is zero after the starting time of the third preset time.

4. The island detection method for energy storage inverter according to claim 1, characterized in that: In step S2, the total error of the first grid voltage within the second preset time is calculated based on the average frequency of the grid voltage, the effective value of the grid voltage and all instantaneous sampling values ​​of the grid voltage acquired within the second preset time, including: The total number of instantaneous sampling values ​​of the grid voltage obtained within the second preset time is p ,when p / n When is an integer, the total error of the first grid voltage is: ； when p / n When is a non-integer, the total error of the first grid voltage is: ； In the formula, S n represents the total error of the first grid voltage, V R represents the effective value of the grid voltage, n Indicates the number of preset cycles contained in each grid voltage cycle, grid voltage cycle=1 / average frequency of grid voltage, V x Indicates the first x The instantaneous sampling value of the grid voltage of the energy storage inverter obtained for the first time, x The value is 1~ p , p Indicates the total number of instantaneous sampling values ​​of the grid voltage obtained within the second preset time; m express p / n The floor value of .

5. The island detection method for energy storage inverter according to claim 1, characterized in that: In step S3, the total error of the second grid voltage within the third preset time is calculated based on the average frequency of the grid voltage, the effective value of the grid voltage and all instantaneous sampling values ​​of the grid voltage acquired within the third preset time, including: The total number of instantaneous sampling values ​​of the grid voltage obtained within the third preset time is q ,when q / n When is an integer, the total error of the second grid voltage is: ； when q / n When is a non-integer, the total error of the second grid voltage is: ； In the formula, represents the total error of the second grid voltage, V R represents the effective value of the grid voltage, n Indicates the number of preset cycles contained in each grid voltage cycle, grid voltage cycle=1 / average frequency of grid voltage, V y Indicates the first y The instantaneous sampling value of the grid voltage of the energy storage inverter obtained by the island disturbance, y The value is 1~ q , q represents the total number of instantaneous sampling values ​​of the grid voltage obtained within the third preset time; s express q / n The floor value of .

6. The island detection method for energy storage inverter according to claim 1, characterized in that: The islanding disturbance performed on the energy storage inverter in step S3 specifically includes: performing frequency disturbance on the energy storage inverter, and the frequency disturbance amount of the energy storage inverter is less than or equal to 0.18 Hz.

7. An island detection system for an energy storage inverter, characterized in that: It includes a state recognition module, an error accumulation module, a new error accumulation and island determination module, wherein: The state identification module is used to obtain the average frequency and effective value of the grid voltage of the energy storage inverter within the first preset time; wherein, obtaining the average frequency and effective value of the grid voltage of the energy storage inverter within the first preset time includes: grid phase locking, tracking the current grid phase; obtaining the average frequency of the grid voltage of the energy storage inverter within the first preset time, and setting each grid voltage cycle to consist of points with the same time interval, and obtaining a preset cycle according to the average frequency and the number of points of the grid voltage; performing average filtering on the grid voltage of the energy storage inverter within the first preset time, and obtaining the effective value of the grid voltage after average filtering; The error accumulation module is used to obtain the instantaneous sampling value of the grid voltage of the energy storage inverter once every preset period within the second preset time, and calculate the first grid voltage total error within the second preset time according to the average frequency of the grid voltage, the effective value of the grid voltage and all the instantaneous sampling values ​​of the grid voltage obtained within the second preset time; wherein, calculating the first grid voltage total error within the second preset time according to the average frequency of the grid voltage, the effective value of the grid voltage and all the instantaneous sampling values ​​of the grid voltage obtained within the second preset time includes: calculating the first grid voltage sub-error according to the average frequency of the grid voltage, the effective value of the grid voltage and each instantaneous sampling value of the grid voltage obtained within the second preset time; adding all the first grid voltage sub-errors calculated within the second preset time to obtain the first grid voltage total error within the second preset time; The new error accumulation and island determination module is used to perform island disturbance on the energy storage inverter, and obtain the instantaneous sampling value of the grid voltage of the energy storage inverter with island disturbance once every preset period within a third preset time, and calculate the second grid voltage total error within the third preset time according to the average frequency of the grid voltage, the effective value of the grid voltage and all the instantaneous sampling values ​​of the grid voltage obtained within the third preset time; then judge whether the absolute value of the difference between the second grid voltage total error and the first grid voltage total error is greater than the absolute value of the island identification amount, if so, judge that the island occurs; wherein, according to the average frequency of the grid voltage, the effective value of the grid voltage and all the instantaneous sampling values ​​of the grid voltage obtained within the third preset time, calculating the second grid voltage total error within the third preset time includes: calculating the second grid voltage sub-error according to the average frequency of the grid voltage, the effective value of the grid voltage and each instantaneous sampling value of the grid voltage obtained within the third preset time; adding all the second grid voltage sub-errors calculated within the third preset time to obtain the second grid voltage total error within the third preset time.

8. A computer-readable storage medium, characterized in that: A computer program is stored in the computer-readable storage medium, wherein the computer program is configured to be executable by a processor to execute the islanding detection method for the energy storage inverter according to any one of claims 1 to 6.

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