Inverter grid-connected and off-grid detection method, device and equipment and storage medium

Abstract

The invention relates to the technical field of photovoltaic energy storage inverter grid-connected and off-grid detection, and discloses an inverter grid-connected and off-grid detection method, device and equipment and a storage medium, and the method comprises the steps: judging whether an inverter is in a grid-connected operation state or not; when the inverter is in the grid-connected operation state, acquiring the fundamental voltage of the inverter and the sampling voltage of the power grid at the current moment; after virtual power grid voltage is obtained through calculation based on the fundamental wave voltage, phase voltages of the same phase between the virtual power grid voltage and the sampling voltage are compared; and in a preset time, if the difference value of the phase voltage of at least one phase is out of a preset range, determining that the inverter is in an off-grid state. According to the method, false triggering detection is not easy, the calculation process related to grid-connected and off-grid detection of the power grid voltage is simplified, the problem that the proportion of chip resources is too high during calculation is solved, and meanwhile the accuracy and rapidity of grid-connected and off-grid detection are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of photovoltaic energy storage inverter on-grid and off-grid detection, and in particular to an inverter on-grid and off-grid detection method, device, equipment and storage medium. Background Art

[0002] The current grid off-grid detection scheme for energy storage inverters mostly adopts grid voltage amplitude detection or modulation ratio threshold detection. The current grid voltage amplitude detection requires real-time sampling of the three-phase grid voltage. After setting the number of sampling times for a power frequency cycle, it is determined whether the cumulative sum of the three-phase instantaneous voltage sampled each time is lower than the set power failure detection point. However, the voltage at the power failure detection point is related to the local grid. When the grid is oscillating, it is easy to falsely trigger the off-grid detection and cause off-grid; while the modulation ratio threshold detection is based on whether the modulation ratio of the inverter output exceeds the set threshold. This detection scheme does not need to consider the grid voltage, but the disadvantage is that the modulation ratio of the inverter output is easy to saturate when the grid has harmonics, and the setting requirements for the modulation ratio threshold are high, which may cause false triggering. Summary of the invention

[0003] Therefore, the technical problem to be solved by the present invention is to solve the problem of complex inverter on-grid and off-grid detection process and low accuracy in the prior art, thereby providing an inverter on-grid and off-grid detection method, device, equipment and storage medium.

[0004] In order to achieve the above object, the present invention provides the following technical solutions:

[0005] In a first aspect, the present invention provides an inverter on-grid and off-grid detection method, comprising: determining whether the inverter is in a grid-connected operating state; when the inverter is in a grid-connected operating state, obtaining the fundamental voltage of the inverter and the sampling voltage of the grid at the current moment; after obtaining a virtual grid voltage based on the fundamental voltage calculation, respectively comparing the magnitude of the phase voltage of the same phase between the virtual grid voltage and the sampling voltage; within a preset time, if the difference in the phase voltage of at least one phase is outside a preset range, determining that the inverter is in an off-grid state.

[0006] The inverter on-grid and off-grid detection method provided by the present invention calculates the virtual grid voltage by using the fundamental voltage, and compares the sampled voltage of the grid with the phase voltage of each phase of the virtual grid voltage. When the voltage difference of any phase exceeds a preset range, it can be determined that the inverter is off-grid. The calculation process and judgment method are simple, which reduces the resource occupation of the computing chip, improves the detection speed, has fewer calculation steps and high accuracy.

[0007] In an optional embodiment, the output end of the inverter is connected to the power supply end of the load through a static transfer switch, and the process of determining whether the inverter is in a grid-connected operation state includes: determining whether the output end of the inverter is connected to the static transfer switch; when the inverter is connected to the static transfer switch, it indicates that the inverter has a grid-connected and off-grid switching function, and then determining whether the inverter is in a grid-connected state and completes phase locking; when the inverter is in a grid-connected state and completes phase locking, it is determined that the inverter is in a normal grid-connected operation state.

[0008] The inverter on-grid and off-grid detection method provided by the present invention determines whether the system has an on-grid and off-grid switching function by judging whether the inverter is connected to a static transfer switch, only calculates and judges the voltage difference for the system with the switching function, optimizes the detection steps, and further improves the detection speed and efficiency.

[0009] In an optional embodiment, within a preset time, if the difference in phase voltage of at least one phase is outside a preset range, the process of determining that the inverter is in an off-grid state includes: setting a detection flag for the phase voltage difference of each phase, the value of the detection flag representing whether the phase voltage difference of the phase is within a preset range; within a preset time, when it is determined that the difference in phase voltage of at least one phase is outside a preset range, setting the corresponding detection flag to 1; when the preset time is reached, detecting the value of each corresponding detection flag; when at least one detection flag is 1, determining that the inverter is in an off-grid state.

[0010] In an optional embodiment, the method further includes: when the difference in phase voltage of any phase is within a preset range, or the inverter is not connected to a static transfer switch, or the inverter has not completed phase locking, clearing the timing and setting each corresponding detection flag to 0.

[0011] In an optional implementation, the method further includes: when all detection flags are 0, determining that the inverter is in a grid-connected state.

[0012] In an optional implementation, before determining that the inverter is in an off-grid state, the process further includes: performing safety fault detection and grid rapid overvoltage detection on the inverter.

[0013] In an optional implementation, after determining that the inverter is in an off-grid state, the process further includes: controlling the static transfer switch between the inverter and the power grid to switch the inverter to an off-grid operation state.

[0014] In a second aspect, the present invention provides an inverter on-grid and off-grid detection device, comprising: a judgment module, used to judge whether the inverter is in a grid-connected operation state; an acquisition module, used to obtain the fundamental voltage of the inverter and the sampling voltage of the grid at the current moment when the inverter is in the grid-connected operation state; a calculation and comparison module, used to calculate the virtual grid voltage based on the fundamental voltage, and then compare the magnitude of the phase voltage of the same phase between the virtual grid voltage and the sampling voltage; an on-grid and off-grid state judgment module, used to judge that the inverter is in an off-grid state if the difference in the phase voltage of at least one phase is outside a preset range within a preset time.

[0015] In a third aspect, the present invention provides a computer device, comprising: a memory and a processor, the memory and the processor are communicatively connected to each other, the memory stores computer instructions, and the processor executes the inverter on-grid and off-grid detection method of the first aspect by executing the computer instructions.

[0016] In a fourth aspect, the present invention provides a computer-readable storage medium having computer instructions stored thereon, the computer instructions being used to enable a computer to execute the inverter on-grid and off-grid detection method of the first aspect. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0018] Figure 1 is a flow chart of an inverter on-grid and off-grid detection method according to an embodiment of the present invention;

[0019] Figure 2 is a flow chart of another inverter on-grid and off-grid detection method according to an embodiment of the present invention;

[0020] Figure 3 is a flow chart of another inverter on-grid and off-grid detection method according to an embodiment of the present invention;

[0021] Figure 4 is a schematic diagram of a specific process of switching between the on-grid and off-grid states of an inverter according to an embodiment of the present invention;

[0022] Figure 5 is a schematic diagram of a specific process of an inverter on-grid and off-grid detection method according to an embodiment of the present invention;

[0023] Figure 6 is a schematic diagram of an inverter on-grid and off-grid detection device according to an embodiment of the present invention;

[0024] Figure 7 It is a schematic diagram of the hardware structure of a computer device according to an embodiment of the present invention. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings 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 those skilled in the art without creative work are within the scope of protection of the present invention.

[0026] According to an embodiment of the present invention, a DC converter control method embodiment is provided. It should be noted that the steps shown in the flowchart of the accompanying drawings can be executed in a computer system such as a set of computer executable instructions, and although a logical order is shown in the flowchart, in some cases, the steps shown or described can be executed in an order different from that shown here.

[0027] In the inverter power supply system, it is often necessary to detect the on-grid and off-grid status of the inverter. In order to ensure that false detection will not cause disconnection from the grid, the existing on-grid and off-grid detection technology usually adopts a more complex calculation method to improve accuracy, but it will increase the MCU resource usage of the computing chip; at the same time, some detection methods also use on-grid and off-grid switching to improve the speed of on-grid and off-grid detection and switching. When grid voltage fluctuations are detected, on-grid and off-grid switching will be performed quickly, resulting in the 1ms power outage test process also triggering the on-grid and off-grid switching action, causing false triggering.

[0028] This embodiment provides a method for detecting an inverter on-grid or off-grid, which can simplify the detection and judgment process and reduce the possibility of false triggering. Figure 1 As shown, the method includes:

[0029] Step S1: Determine whether the inverter is in a grid-connected operation state.

[0030] Optionally, the output end of the inverter is connected to the power supply end of the load through a static transfer switch. When the inverter needs to be connected to the grid, the system switches the inverter to a state of being connected to the grid by controlling the static transfer switch. When the inverter needs to be off-grid, the system disconnects the inverter from the grid by controlling the static transfer switch, and the inverter is powered independently. Figure 2 As shown, the process of judging whether the inverter is in the grid-connected operation state includes:

[0031] Step S11: Determine whether the output end of the inverter is connected to a static transfer switch.

[0032] Step S12: When the inverter is connected to the static transfer switch, it indicates that the inverter has the grid-connected and off-grid switching function, and then it is determined whether the inverter is in the grid-connected state and the phase lock is completed.

[0033] Step S13: When the inverter is in the grid-connected state and phase locking is completed, it is determined that the inverter is in the normal grid-connected operation state.

[0034] Specifically, when it is determined that the static transfer switch of the inverter is not connected, it indicates that the inverter does not have the grid-connected and off-grid switching function, and the inverter is assumed to be in the grid-connected operation state by default, and the subsequent grid-connected and off-grid detection steps can be skipped.

[0035] Step S2: when the inverter is in the grid-connected operation state, the fundamental voltage of the inverter and the sampling voltage of the grid at the current moment are obtained.

[0036] Specifically, when it is determined that the inverter is in the grid-connected operation state, the actual sampled instantaneous value of the grid voltage is obtained, and the fundamental voltage of the inverter is calculated using the fast Fourier transform. The fast Fourier calculation can obtain a stable and accurate fundamental voltage amplitude. At the same time, the fast Fourier calculation maintains a calculation cycle of about 20ms in the code, reducing the resource occupation of the computing chip.

[0037] Step S3: After the virtual grid voltage is obtained based on the fundamental voltage calculation, the magnitude of the phase voltage of the same phase between the virtual grid voltage and the sampled voltage is compared respectively.

[0038] Specifically, the virtual grid voltage is calculated according to the fundamental voltage, and the phase voltage amplitude of each phase of the virtual grid voltage is compared with the phase voltage amplitude of each phase of the sampled voltage, and the absolute value of the difference between the phase voltage amplitudes of each phase is calculated respectively.

[0039] Step S4: within a preset time, if the difference of the phase voltage of at least one phase is outside a preset range, it is determined that the inverter is in an off-grid state.

[0040] Specifically, after the virtual grid voltage is calculated, the timing starts according to the preset time, such as Figure 3 As shown, within a preset time, if the difference of the phase voltage of at least one phase is outside a preset range, the process of determining that the inverter is in an off-grid state includes:

[0041] Step S41: setting a detection flag for the phase voltage difference of each phase respectively, and the value of the detection flag represents whether the phase voltage difference of the phase is within a preset range.

[0042] Optionally, for the A, B, C three-phase grid voltages, detection flags Flag1, Flag2, and Flag3 are set correspondingly, respectively.

[0043] Step S42: within a preset time, when it is determined that the difference of the phase voltage of at least one phase is outside a preset range, the corresponding detection flag is set to 1.

[0044] Specifically, within the preset time, when it is determined that the difference of the phase voltage of at least one phase is outside the preset range, the corresponding detection flag Flag1 or Flag2 or Flag3 is set to 1, and the detection flag corresponding to the phase voltage within the preset range is set to 0. When the inverter is not connected to the static transfer switch, or the inverter has not completed phase locking, or after the preset time is reached, the phase voltage difference of each phase is within the preset range, the inverter is assumed to be in the grid-connected state, the current timing is cleared, and each corresponding detection flag Flag1, Flag2 and Flag3 are set to 0.

[0045] Step S43: When the preset time is reached, the values ​​of the corresponding detection marks are detected.

[0046] Step S44: When at least one detection flag is 1, it is determined that the inverter is in an off-grid state.

[0047] Specifically, if the value of at least one detection flag among all Flag1, Flag2 and Flag3 within the preset time is 1, it indicates that the working voltage of the inverter in the current working state deviates greatly from the predicted standard working voltage when connected to the grid, that is, it is in an off-grid state; if the values ​​of all detection flags are 0, it indicates that the working voltage of the inverter in the current working state deviates little from or is consistent with the predicted standard working voltage when connected to the grid, and it is determined that the inverter is currently in a grid-connected state.

[0048] Specifically, when it is determined that the inverter is currently in an off-grid state, the static transfer switch connected to the inverter is controlled to operate, and the inverter is controlled to switch to off-grid operation; when it is determined that the inverter is currently in a grid-connected state, the static transfer switch is controlled not to operate, and the inverter maintains grid-connected operation.

[0049] In some optional implementations, before determining that the inverter is in an off-grid state, the process further includes: performing safety fault detection and grid rapid overvoltage detection on the inverter.

[0050] Specifically, Figure 4 In the process, before determining whether the inverter is currently in the grid-connected state or the off-grid state, it is also necessary to perform safety fault detection and grid rapid overvoltage detection on the inverter and the power supply system, perform electrical safety tests, electromagnetic compatibility tests, environmental adaptability tests, etc. on the inverter, and monitor the voltage in the grid in real time to detect whether the voltage exceeds the set safety threshold, so as to promptly discover and handle overvoltage conditions, prevent equipment damage or grid accidents, ensure that the inverter is in normal working condition, and ensure the safety of the power supply system.

[0051] For example, reference Figure 5 The process of detecting the inverter on and off the grid and controlling the inverter on and off the grid switching is as follows:

[0052] (1) Check whether the power supply system where the inverter is located has a static transfer switch.

[0053] (2) If there is a static transfer switch, determine whether the inverter is in the grid-connected state and complete the phase lock; if there is no static transfer switch, clear the current timing and set all detection flags to 0, and directly enter step (5).

[0054] (3) If it is determined that the inverter has completed phase locking, a virtual three-phase grid voltage is calculated based on the three-phase fundamental voltage, and after comparing the collected three-phase voltage with the virtual voltage, safety fault detection and grid rapid overvoltage detection are performed.

[0055] (4) If it is determined that the inverter has not completed phase locking, safety fault detection and grid rapid overvoltage detection are directly performed.

[0056] (5) Determine the value of each detection mark within a preset time. If at least one detection mark is 1, it is determined that the inverter is in an off-grid state; if all detection marks are 0, it is determined that the inverter is in a grid-connected state.

[0057] (6) When the inverter is determined to be in an off-grid state, the static transfer switch is controlled to operate so that the inverter exits the grid and operates off-grid; when the inverter is determined to be in a grid-connected state, the static transfer switch remains unchanged so that the inverter maintains grid-connected operation.

[0058] In this embodiment, an inverter on-grid and off-grid detection device is also provided, which is used to implement the above embodiments and preferred implementations, and will not be repeated for what has been described. As used below, the term "module" can be a combination of software and / or hardware that implements a predetermined function. Although the device described in the following embodiments is preferably implemented in software, the implementation of hardware, or a combination of software and hardware, is also possible and conceivable.

[0059] This embodiment provides an inverter on-grid and off-grid detection device, such as Figure 6 As shown, the device comprises:

[0060] The judging module 601 is used to judge whether the inverter is in a grid-connected operation state.

[0061] The acquisition module 602 is used to acquire the fundamental voltage of the inverter and the sampled voltage of the grid at the current moment when the inverter is in the grid-connected operation state.

[0062] The calculation and comparison module 603 is used to compare the magnitude of the phase voltage of the same phase between the virtual grid voltage and the sampled voltage after obtaining the virtual grid voltage based on the fundamental voltage.

[0063] The grid-connected or off-grid state determination module 604 is used to determine that the inverter is in an off-grid state if the difference in phase voltage of at least one phase is outside a preset range within a preset time.

[0064] The inverter on-grid and off-grid detection device in this embodiment is presented in the form of a functional unit, where the unit refers to an ASIC circuit, a processor and memory that executes one or more software or fixed programs, and / or other devices that can provide the above functions.

[0065] The further functional description of each of the above modules and units is the same as that of the above corresponding embodiments and will not be repeated here.

[0066] An embodiment of the present invention further provides a computer device having the above inverter on-grid and off-grid detection device.

[0067] See also Figure 7 , Figure 7 is a schematic diagram of the structure of a computer device provided by an optional embodiment of the present invention, such as Figure 7 As shown, the computer device includes: one or more processors 10, a memory 20, and interfaces for connecting various components, including high-speed interfaces and low-speed interfaces. Various components are connected to each other using different buses for communication, and can be installed on a common mainboard or installed in other ways as needed. The processor can process the instructions executed in the computer device, including instructions stored in or on the memory to display the graphical information of the GUI on an external input / output device (such as, a display device coupled to the interface). In some optional embodiments, if necessary, multiple processors and / or multiple buses can be used together with multiple memories and multiple memories. Similarly, multiple computer devices can be connected, and each device provides some necessary operations (for example, as a server array, a group of blade servers, or a multi-processor system). Figure 7 A processor 10 is taken as an example.

[0068] The processor 10 may be a central processing unit, a network processor or a combination thereof. The processor 10 may further include a hardware chip. The hardware chip may be a dedicated integrated circuit, a programmable logic device or a combination thereof. The programmable logic device may be a complex programmable logic device, a field programmable gate array, a general purpose array logic or any combination thereof.

[0069] The memory 20 stores instructions executable by at least one processor 10, so that at least one processor 10 executes the method shown in the above embodiment.

[0070] The memory 20 may include a program storage area and a data storage area, wherein the program storage area may store an operating system, an application required for at least one function; the data storage area may store data created by the use of a computer device based on the presentation of a small program landing page, etc. In addition, the memory 20 may include a high-speed random access memory, and may also include a non-transient memory, such as at least one disk storage device, a flash memory device, or other non-transient solid-state storage device. In some optional embodiments, the memory 20 may optionally include a memory remotely arranged relative to the processor 10, and these remote memories may be connected to the computer device via a network. Examples of the above-mentioned network include, but are not limited to, the Internet, an intranet, a local area network, a mobile communication network, and combinations thereof.

[0071] The memory 20 may include a volatile memory, such as a random access memory; the memory may also include a non-volatile memory, such as a flash memory, a hard disk or a solid state drive; the memory 20 may also include a combination of the above types of memory.

[0072] The computer device further comprises a communication interface 30 for the computer device to communicate with other devices or a communication network.

[0073] The embodiment of the present invention also provides a computer-readable storage medium. The method according to the embodiment of the present invention can be implemented in hardware, firmware, or can be implemented as a computer code that can be recorded in a storage medium, or can be implemented as a computer code that is originally stored in a remote storage medium or a non-temporary machine-readable storage medium and will be stored in a local storage medium through a network download, so that the method described herein can be stored in such software processing on a storage medium using a general-purpose computer, a dedicated processor, or programmable or dedicated hardware. Among them, the storage medium can be a magnetic disk, an optical disk, a read-only storage memory, a random access memory, a flash memory, a hard disk or a solid-state hard disk, etc.; further, the storage medium can also include a combination of the above types of memories. It can be understood that a computer, a processor, a microprocessor controller, or programmable hardware includes a storage component that can store or receive software or computer code. When the software or computer code is accessed and executed by a computer, a processor, or hardware, the method shown in the above embodiment is implemented.

[0074] Although the embodiments of the present invention have been described in conjunction with the accompanying drawings, those skilled in the art may make various modifications and variations without departing from the spirit and scope of the present invention, and such modifications and variations are all within the scope defined by the appended claims.

Claims

1. A method for detecting an inverter on-grid or off-grid, characterized in that: include: Determine whether the inverter is in grid-connected operation; When the inverter is in a grid-connected operation state, obtaining the fundamental voltage of the inverter and the sampling voltage of the grid at the current moment; After obtaining the virtual grid voltage based on the fundamental voltage, respectively comparing the magnitude of the phase voltage of the same phase between the virtual grid voltage and the sampled voltage; If the difference of the phase voltage of at least one phase is outside a preset range within a preset time, it is determined that the inverter is in an off-grid state.

2. The method according to claim 1, characterized in that The output end of the inverter is connected to the power supply end of the load through a static transfer switch, and the process of determining whether the inverter is in a grid-connected operation state includes: Determining whether the output end of the inverter is connected to a static transfer switch; When the inverter is connected to the static transfer switch, it indicates that the inverter has a grid-connected and off-grid switching function, and then it is determined whether the inverter is in a grid-connected state and phase-locked; When the inverter is in the grid-connected state and phase locking is completed, it is determined that the inverter is in the normal grid-connected operation state.

3. The method according to claim 2, characterized in that The process of determining that the inverter is in an off-grid state if the difference of the phase voltage of at least one phase is outside a preset range within a preset time includes: A detection flag is set for each phase voltage difference, and the value of the detection flag indicates whether the phase voltage difference of the phase is within a preset range; Within a preset time, when it is determined that the difference of the phase voltage of at least one phase is outside the preset range, the corresponding detection flag is set to 1; When the preset time is reached, the value of each corresponding detection mark is detected; When at least one detection flag is 1, it is determined that the inverter is in an off-grid state.

4. The method according to claim 2, characterized in that: Also includes: When the difference of the phase voltages of any phase is within a preset range, or the inverter is not connected to a static transfer switch, or the inverter has not completed phase locking, the timing is cleared and the detection flag of each corresponding phase is set to 0.

5. The method according to claim 3, characterized in that: Also includes: When all detection flags are 0, it is determined that the inverter is in a grid-connected state.

6. The method according to claim 1, characterized in that Before the process of determining that the inverter is in an off-grid state, the process further includes: The inverter is subjected to safety fault detection and grid rapid overvoltage detection.

7. The method according to claim 1, characterized in that After the process of determining that the inverter is in an off-grid state, the process further includes: The static transfer switch between the inverter and the power grid is controlled to switch the inverter to an off-grid operation state.

8. An inverter on-grid and off-grid detection device, characterized in that: include: A judgment module, used to judge whether the inverter is in a grid-connected operation state; An acquisition module, used to acquire the fundamental voltage of the inverter and the sampling voltage of the grid at the current moment when the inverter is in a grid-connected operation state; A calculation and comparison module, configured to compare the magnitude of the phase voltage of the same phase between the virtual grid voltage and the sampled voltage after obtaining the virtual grid voltage based on the fundamental voltage; The on-grid and off-grid state determination module is used to determine that the inverter is in an off-grid state if the difference in phase voltage of at least one phase is outside a preset range within a preset time.

9. A computer device, characterized in that: include: A memory and a processor, wherein the memory and the processor are communicatively connected to each other, the memory stores computer instructions, and the processor executes the inverter on-grid and off-grid detection method according to any one of claims 1 to 7 by executing the computer instructions.

10. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores computer instructions, and the computer instructions are used to enable a computer to execute the inverter on-grid and off-grid detection method according to any one of claims 1 to 7.

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