Photovoltaic access system protection method and apparatus

Abstract

The application provides a photovoltaic access system protection method and device, the method comprises the following steps: detecting the impedance of the photovoltaic access system to obtain the detection impedance of the photovoltaic access system; determining the calculation impedance of the photovoltaic access system based on the current, voltage and voltage-current phase angle of the photovoltaic access system; in the case that the detection impedance is consistent with the calculation impedance, determining whether the photovoltaic access system resonates based on the reactance, capacitance and angular frequency of the photovoltaic access system; the angular frequency is determined based on the voltage-current phase; in the case that the photovoltaic access system resonates, adjusting the impedance of the photovoltaic access system. The photovoltaic access system protection method and device provided by the application can avoid the problem that the photovoltaic access system causes serious overvoltage or overcurrent and further seriously affects the safety in the case of resonance without changing the parameters of the distributed photovoltaic converter in the photovoltaic access system.

Description

Technical Field

[0001] This invention relates to the field of photovoltaic grid connection technology, and in particular to a method and apparatus for protecting photovoltaic grid connection systems. Background Technology

[0002] Distributed photovoltaic (PV) grid connection systems are easy to deploy and can be flexibly connected to local low-voltage power distribution systems, thus they are widely used in petrochemical enterprises to meet their carbon emission standards.

[0003] Distributed photovoltaic grid connection systems are mostly implemented by connecting to the grid in the form of converters and filters. However, resonance problems may occur between multiple distributed grid connection points or between the grid and loads, leading to severe overvoltage or overcurrent, which seriously affects safety. Summary of the Invention

[0004] This invention provides a method and apparatus for protecting photovoltaic (PV) grid connection systems, which addresses the shortcomings of existing technologies where PV grid connection systems are prone to resonance, thus affecting safety.

[0005] This invention provides a protection method for a photovoltaic grid connection system, comprising:

[0006] Impedance detection is performed on the photovoltaic grid connection system to obtain the detection impedance of the photovoltaic grid connection system;

[0007] The calculated impedance of the photovoltaic access system is determined based on the current, voltage, and voltage-current phase angle of the photovoltaic access system.

[0008] When the detected impedance is consistent with the calculated impedance, it is determined whether the photovoltaic access system has resonance based on the reactance, capacitance and angular frequency of the photovoltaic access system; the angular frequency is determined based on the voltage and current phase.

[0009] If resonance is found in the photovoltaic access system, the impedance of the photovoltaic access system is adjusted.

[0010] According to a photovoltaic (PV) grid connection system protection method provided by the present invention, determining whether resonance exists in the PV grid connection system based on the reactance, capacitance, and angular frequency of the PV grid connection system includes:

[0011] Based on the reactance, capacitance, and angular frequency in the series circuit of the photovoltaic access system, determine whether voltage resonance exists in the photovoltaic access system;

[0012] And / or,

[0013] Based on the reactance, capacitance, and angular frequency in the parallel circuit of the photovoltaic access system, determine whether current resonance exists in the photovoltaic access system.

[0014] According to a photovoltaic (PV) grid connection system protection method provided by the present invention, determining whether voltage resonance exists in the PV grid connection system based on the reactance, capacitance, and angular frequency in the series circuit of the PV grid connection system includes:

[0015] If the reactance, capacitance, and angular frequency in the series circuit satisfy the voltage resonance model, it is determined that voltage resonance exists in the photovoltaic access system.

[0016] The voltage resonance model is as follows:

[0017]

[0018] Where, ω 1n L represents the angular frequency in the series circuit. 1n C represents the reactance in the series circuit. 1n This represents the capacitance in the series circuit.

[0019] According to a photovoltaic (PV) grid connection system protection method provided by the present invention, determining whether current resonance exists in the PV grid connection system based on the reactance, capacitance, and angular frequency in the parallel circuit of the PV grid connection system includes:

[0020] If the reactance, capacitance, and angular frequency in the parallel circuit satisfy the current resonance model, it is determined that the photovoltaic access system has current resonance.

[0021] The current resonance model is as follows:

[0022]

[0023] Where, ω 2n L represents the angular frequency in the parallel circuit. 2n C represents the reactance in the parallel circuit. 2n This represents the capacitance in the parallel circuit.

[0024] According to a photovoltaic (PV) grid connection system protection method provided by the present invention, adjusting the impedance of the PV grid connection system when resonance is determined to exist includes:

[0025] If resonance is found in the photovoltaic access system, adjust the series or parallel circuit impedance of the photovoltaic access system.

[0026] According to a photovoltaic (PV) grid connection system protection method provided by the present invention, after adjusting the impedance of the PV grid connection system, the method further includes:

[0027] The photovoltaic access system is subjected to resonance detection. If resonance exists in the photovoltaic access system, each photovoltaic inverter in the photovoltaic access system is taken out of the working mode in the order of voltage from large to small or current from large to small, until the photovoltaic access system eliminates resonance.

[0028] The present invention also provides a protection device for a photovoltaic grid connection system, comprising:

[0029] The detection unit allows the user to perform impedance detection on the photovoltaic access system and obtain the detection impedance of the photovoltaic access system.

[0030] The calculation unit is used to determine the calculated impedance of the photovoltaic access system based on the current, voltage, and voltage-current phase angle of the photovoltaic access system.

[0031] The determining unit is configured to determine whether resonance exists in the photovoltaic access system based on the reactance, capacitance, and angular frequency of the photovoltaic access system, provided that the detected impedance is consistent with the calculated impedance; the angular frequency is determined based on the voltage and current phase.

[0032] The adjustment unit is used to adjust the impedance of the photovoltaic access system when it is determined that resonance exists in the photovoltaic access system.

[0033] The present invention also provides an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the program to implement the photovoltaic access system protection method as described above.

[0034] The present invention also provides a non-transitory computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the photovoltaic access system protection method as described above.

[0035] The present invention also provides a computer program product, including a computer program that, when executed by a processor, implements the photovoltaic access system protection method as described above.

[0036] The photovoltaic (PV) grid connection system protection method and device provided by this invention, when the detected impedance and the calculated impedance are consistent, determines whether the PV grid connection system has resonance based on the reactance, capacitance and angular frequency of the PV grid connection system, and adjusts the impedance of the PV grid connection system when resonance is determined to exist. In this way, without changing the parameters of the distributed PV converters in the PV grid connection system, it can avoid the problem of serious overvoltage or overcurrent caused by resonance in the PV grid connection system, which would seriously affect safety. Attached Figure Description

[0037] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0038] Figure 1 This is a flowchart illustrating the photovoltaic grid connection system protection method provided by the present invention;

[0039] Figure 2 This is a schematic diagram of the structure of the photovoltaic access system protection device provided by the present invention;

[0040] Figure 3 This is a schematic diagram of the structure of the photovoltaic access system protection system provided by the present invention;

[0041] Figure 4 This is a flowchart illustrating the protection method for a photovoltaic access system protection system provided by the present invention;

[0042] Figure 5 This is a schematic diagram of the structure of the electronic device provided by the present invention. Detailed Implementation

[0043] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0044] Distributed photovoltaic grid connection systems are mostly implemented by connecting to the grid in the form of converters and filters. However, resonance problems may occur between multiple distributed grid connection points or between the grid and loads, leading to severe overvoltage or overcurrent, which seriously affects safety.

[0045] In response, this invention provides a protection method for photovoltaic grid connection systems. Figure 1 This is a flowchart illustrating the photovoltaic grid connection system protection method provided by the present invention, as shown below. Figure 1 As shown, the method includes the following steps:

[0046] Step 110: Perform impedance testing on the photovoltaic access system to obtain the test impedance of the photovoltaic access system.

[0047] Step 120: Determine the calculated impedance of the photovoltaic access system based on the current, voltage, and voltage-current phase angle of the photovoltaic access system.

[0048] Here, the photovoltaic (PV) grid connection system refers to a system requiring resonance detection. This system may include multiple distributed photovoltaic (PV) converters (DPCs). Resonance may occur between these DPCs or between them and the grid. To ensure grid security, resonance detection is necessary for the PV grid connection system, and resonance needs to be eliminated if present. To address this, this invention performs impedance detection on the PV grid connection system to obtain its detection impedance. The detection impedance can be the impedance value obtained after impedance detection of each distributed PV converter in the PV grid connection system. Furthermore, this invention calculates the calculated impedance based on the current, voltage, and voltage-current phase angle of the PV grid connection system; that is, the calculated impedance is an impedance value calculated based on relevant parameters.

[0049] Understandably, after obtaining the detection impedance, it can be stored in a detection impedance database so that the detection impedance can be quickly retrieved from the database. Similarly, after obtaining the calculated impedance, it can be stored in a calculated impedance database so that the calculated impedance can be quickly retrieved from the database.

[0050] Step 130: If the detected impedance and the calculated impedance are consistent, determine whether there is resonance in the photovoltaic access system based on the reactance, capacitance and angular frequency of the photovoltaic access system; the angular frequency is determined based on the voltage and current phase.

[0051] Specifically, if the detected impedance matches the calculated impedance, it indicates that the photovoltaic (PV) grid connection system may have resonance. In this case, based on the reactance, capacitance, and angular frequency of the PV grid connection system, it can be determined whether the current PV grid connection system has resonance. The angular frequency is determined based on the phase of the voltage and current. Resonance includes voltage resonance and current resonance. Voltage resonance refers to the situation in a series circuit composed of an inductor and a capacitor where the voltage and current at the circuit terminals are in phase, or the power factor of the circuit is equal to 1. In a parallel circuit of an inductor and a capacitor, when the capacitance value makes the voltage and current in phase in the circuit, meaning all the power from the source is consumed by the resistance, forming a resistive circuit, it is called parallel resonance, or current resonance.

[0052] Furthermore, if the detected impedance is inconsistent with the calculated impedance, it indicates that there is no resonance in the photovoltaic access system. In this case, it is not necessary to further determine whether resonance exists based on the reactance, capacitance, and angular frequency of the photovoltaic access system.

[0053] Step 140: If resonance is found in the photovoltaic grid connection system, adjust the impedance of the photovoltaic grid connection system.

[0054] Specifically, if resonance exists in the photovoltaic (PV) grid connection system, it can lead to severe overvoltage or overcurrent, thereby seriously affecting grid safety. To address this, this invention, upon determining that resonance exists in the PV grid connection system, adjusts the impedance of the system. For example, the impedance of the series or parallel circuits within the PV grid connection system can be adjusted to eliminate resonance.

[0055] The improved photovoltaic (PV) grid connection system protection method of this invention determines whether resonance exists in the PV grid connection system based on the reactance, capacitance, and angular frequency of the PV grid connection system when the detected impedance and calculated impedance are consistent. If resonance is determined to exist, the impedance of the PV grid connection system is adjusted. This avoids serious overvoltage or overcurrent problems that could seriously affect safety in the event of resonance in the PV grid connection system without changing the parameters of each distributed PV converter in the PV grid connection system.

[0056] Based on the above embodiments, determining whether a photovoltaic (PV) grid connection system exhibits resonance based on its reactance, capacitance, and angular frequency includes:

[0057] Based on the reactance, capacitance, and angular frequency in the series circuit of the photovoltaic access system, determine whether voltage resonance exists in the photovoltaic access system;

[0058] And / or,

[0059] Based on the reactance, capacitance, and angular frequency in the parallel circuit of the photovoltaic grid connection system, determine whether current resonance exists in the photovoltaic grid connection system.

[0060] Specifically, voltage resonance refers to the situation in a series circuit composed of an inductor and a capacitor where the voltage and current at the circuit terminals are in phase or the power factor of the circuit is equal to 1. If voltage resonance exists in a photovoltaic (PV) grid connection system, then the reactance, capacitance, and angular frequency in the series circuit of the PV grid connection system satisfy the voltage resonance model, which can be used to determine whether voltage resonance exists in the PV grid connection system.

[0061] In a circuit where an inductor and a capacitor are connected in parallel, when the capacitance is such that the voltage and current in the circuit are in phase, meaning all the electrical energy is consumed by the resistor and the circuit becomes a resistive circuit, this is called parallel resonance, or current resonance. If current resonance exists in a photovoltaic (PV) grid connection system, then the reactance, capacitance, and angular frequency in the parallel circuit of the PV grid connection system satisfy the current resonance model. Based on this, it can be determined whether current resonance exists in the PV grid connection system.

[0062] Based on any of the above embodiments, determining whether voltage resonance exists in the photovoltaic grid connection system based on the reactance, capacitance, and angular frequency in the series circuit of the photovoltaic grid connection system includes:

[0063] Under the condition that the reactance, capacitance and angular frequency in the series circuit satisfy the voltage resonance model, it is determined that voltage resonance exists in the photovoltaic access system;

[0064] The voltage resonance model is as follows:

[0065]

[0066] Where, ω 1n L represents the angular frequency in a series circuit. 1n C represents the reactance in a series circuit. 1n This represents the capacitance in a series circuit, where n = 1, 2, 3...

[0067] Specifically, if the reactance, capacitance, and angular frequency in the series circuit satisfy the voltage resonance model, it can be determined that voltage resonance exists in the photovoltaic grid connection system. It can be understood that the aforementioned voltage resonance model can be used to determine whether voltage resonance exists in each distributed photovoltaic inverter in the photovoltaic grid connection system. For example, based on the reactance, capacitance, and angular frequency in the series circuit of the nth distributed photovoltaic inverter, it can be determined whether voltage resonance exists in that distributed photovoltaic inverter.

[0068] Based on any of the above embodiments, determining whether current resonance exists in the photovoltaic grid connection system based on the reactance, capacitance, and angular frequency in the parallel circuit of the photovoltaic grid connection system includes:

[0069] Under the condition that the reactance, capacitance and angular frequency in the parallel circuit satisfy the current resonance model, it is determined that there is current resonance in the photovoltaic grid connection system;

[0070] The current resonance model is:

[0071]

[0072] Where, ω 2n L represents the angular frequency in a parallel circuit. 2n C represents the reactance in a parallel circuit. 2n This represents the capacitance in a parallel circuit, where n = 1, 2, 3...

[0073] Specifically, if the reactance, capacitance, and angular frequency in the parallel circuit satisfy the current resonance model, it can be determined that current resonance exists in the photovoltaic grid-connected system. It can be understood that the aforementioned current resonance model can be used to determine whether current resonance exists in each distributed photovoltaic inverter in the photovoltaic grid-connected system. For example, based on the reactance, capacitance, and angular frequency in the parallel circuit of the nth distributed photovoltaic inverter, it can be determined whether current resonance exists in that distributed photovoltaic inverter.

[0074] Based on any of the above embodiments, when it is determined that resonance exists in the photovoltaic grid connection system, the impedance of the photovoltaic grid connection system is adjusted, including:

[0075] If resonance is found in the photovoltaic grid connection system, adjust the series or parallel circuit impedance of the photovoltaic grid connection system.

[0076] Specifically, if resonance exists in the photovoltaic (PV) grid connection system, it can lead to severe overvoltage or overcurrent, thereby seriously affecting grid security. To address this, this embodiment of the invention, upon determining that resonance exists in the PV grid connection system, adjusts the series or parallel circuit impedance of the PV grid connection system to eliminate resonance. It is understood that the parallel circuit capacitance of the PV grid connection system can also be adjusted to eliminate current resonance.

[0077] Specifically, adjusting the impedance of the series circuit can eliminate voltage resonance in the photovoltaic (PV) grid connection system; adjusting the impedance of the parallel circuit can eliminate current resonance in the PV grid connection system. Therefore, this embodiment of the invention, when resonance is determined to exist in the PV grid connection system, adjusts the impedance of the PV grid connection system to avoid severe overvoltage or overcurrent that could seriously affect safety.

[0078] Based on any of the above embodiments, the impedance of the photovoltaic grid connection system is adjusted, and then the following steps are also included:

[0079] Resonance detection is performed on the photovoltaic grid connection system. If resonance exists in the photovoltaic grid connection system, each photovoltaic inverter in the photovoltaic grid connection system is taken out of the working mode in the order of voltage from large to small or current from large to small, until the photovoltaic grid connection system eliminates resonance.

[0080] Specifically, if resonance still exists in the photovoltaic (PV) grid connection system after adjusting its impedance, it indicates that adjusting the impedance cannot eliminate the resonance. To ensure grid safety, this embodiment of the invention deactivates each PV inverter in the PV grid connection system in descending order of voltage or descending order of current until the resonance is eliminated.

[0081] Therefore, this embodiment of the invention performs resonance detection on the photovoltaic grid connection system. If resonance exists in the photovoltaic grid connection system, each photovoltaic inverter in the photovoltaic grid connection system will exit the working mode in the order of voltage from large to small or current from large to small until the photovoltaic grid connection system eliminates the resonance, thereby further ensuring the safety of the power grid.

[0082] The photovoltaic access system protection device provided by the present invention is described below. The photovoltaic access system protection device described below can be referred to in correspondence with the photovoltaic access system protection method described above.

[0083] Based on any of the above embodiments, the present invention also provides a photovoltaic grid connection system protection device, such as... Figure 2 As shown, the device includes:

[0084] Detection unit 210: The user performs impedance detection on the photovoltaic access system to obtain the detection impedance of the photovoltaic access system;

[0085] The calculation unit 220 is used to determine the calculated impedance of the photovoltaic access system based on the current, voltage, and voltage-current phase angle of the photovoltaic access system.

[0086] The determining unit 230 is used to determine whether the photovoltaic access system has resonance based on the reactance, capacitance and angular frequency of the photovoltaic access system when the detected impedance is consistent with the calculated impedance; the angular frequency is determined based on the voltage and current phase.

[0087] The adjustment unit 240 is used to adjust the impedance of the photovoltaic access system when it is determined that resonance exists in the photovoltaic access system.

[0088] Based on any of the above embodiments, the determining unit 230 includes:

[0089] The voltage resonance determination unit is used to determine whether voltage resonance exists in the photovoltaic access system based on the reactance, capacitance and angular frequency in the series circuit of the photovoltaic access system;

[0090] And / or,

[0091] The current resonance determination unit is used to determine whether current resonance exists in the photovoltaic access system based on the reactance, capacitance and angular frequency in the parallel circuit of the photovoltaic access system.

[0092] Based on any of the above embodiments, the voltage resonance determination unit is used for:

[0093] If the reactance, capacitance, and angular frequency in the series circuit satisfy the voltage resonance model, it is determined that voltage resonance exists in the photovoltaic access system.

[0094] The voltage resonance model is as follows:

[0095]

[0096] Where, ω 1n L represents the angular frequency in the series circuit. 1n C represents the reactance in the series circuit. 1n This represents the capacitance in the series circuit.

[0097] Based on any of the above embodiments, the current resonance determination unit includes:

[0098] If the reactance, capacitance, and angular frequency in the parallel circuit satisfy the current resonance model, it is determined that the photovoltaic access system has current resonance.

[0099] The current resonance model is as follows:

[0100]

[0101] Where, ω 2n L represents the angular frequency in the parallel circuit. 2n C represents the reactance in the parallel circuit. 2n This represents the capacitance in the parallel circuit.

[0102] Based on any of the above embodiments, the adjustment unit 240 is used for:

[0103] If resonance is found in the photovoltaic access system, adjust the series or parallel circuit impedance of the photovoltaic access system.

[0104] Based on any of the above embodiments, the device further includes:

[0105] The harmonic elimination unit is used to adjust the impedance of the photovoltaic access system and then perform resonance detection on the photovoltaic access system. If resonance exists in the photovoltaic access system, the photovoltaic inverters in the photovoltaic access system will exit the working mode in order of voltage from large to small or current from large to small until the resonance of the photovoltaic access system is eliminated.

[0106] Based on any of the above embodiments, the present invention also provides a photovoltaic grid connection system protection system, such as... Figure 3 As shown, the system includes: impedance detection units 1, 2...N, current feedback units 1, 2...N, voltage feedback units 1, 2...N, voltage / current phase angle detection units 1, 2...N, adjustable impedance units 1, 2...N, etc., corresponding to distributed photovoltaic power generation converters 1, 2...N respectively, an impedance detection database, an impedance calculation database, and a stability controller.

[0107] like Figure 4As shown, the protection method based on the above photovoltaic grid connection protection system includes: First, the impedance detection unit detects the impedance value of the distributed photovoltaic power generation converter and stores the detected impedance value in the detection impedance database; Second, the current feedback unit, voltage feedback unit, and voltage / current phase angle detection unit respectively feed the photovoltaic power generation converter current, voltage, and voltage / current phase angle to the calculated impedance database to obtain the calculated impedance value, and store the calculated impedance value in the calculated impedance database; Next, when the detected impedance value in the detection impedance database and the calculated impedance value in the calculated impedance database are consistent, the stability controller determines whether voltage resonance or current resonance has occurred based on the impedance situation. If so, the adjustable impedance unit is selected to adjust the impedance of the corresponding series or parallel circuit for hardware resonance elimination; After the adjustable impedance unit is selected, if the resonance between the 1.2...N distributed photovoltaic power generation converters and the petrochemical enterprise grid cannot be eliminated, the distributed photovoltaic power generation converters exit the working mode sequentially according to the voltage decreasing or the current decreasing, until the photovoltaic grid connection system is operating stably.

[0108] Figure 5 This is a schematic diagram of the structure of the electronic device provided by the present invention, such as... Figure 5 As shown, the electronic device may include a processor 510, a memory 520, a communication interface 530, and a communication bus 540, wherein the processor 510, memory 520, and communication interface 530 communicate with each other through the communication bus 540. The processor 510 can call logic instructions in the memory 520 to execute a photovoltaic (PV) grid connection system protection method. This method includes: performing impedance detection on the PV grid connection system to obtain the detected impedance; determining the calculated impedance of the PV grid connection system based on the current, voltage, and voltage-current phase angle; if the detected impedance matches the calculated impedance, determining whether resonance exists in the PV grid connection system based on the reactance, capacitance, and angular frequency of the PV grid connection system; the angular frequency is determined based on the voltage-current phase; and adjusting the impedance of the PV grid connection system if resonance is determined to exist.

[0109] Furthermore, the logical instructions in the aforementioned memory 520 can be implemented as software functional units and, when sold or used as independent products, can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, essentially, or the part that contributes to the prior art, or a part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of the present invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0110] On the other hand, the present invention also provides a computer program product, the computer program product comprising a computer program stored on a non-transitory computer-readable storage medium, the computer program comprising program instructions, wherein when the program instructions are executed by a computer, the computer is able to execute the photovoltaic access system protection method provided by the above methods, the method comprising: performing impedance detection on the photovoltaic access system to obtain the detected impedance of the photovoltaic access system; determining the calculated impedance of the photovoltaic access system based on the current, voltage, and voltage-current phase angle of the photovoltaic access system; when the detected impedance is consistent with the calculated impedance, determining whether the photovoltaic access system resonates based on the reactance, capacitance, and angular frequency of the photovoltaic access system; the angular frequency being determined based on the voltage-current phase; and adjusting the impedance of the photovoltaic access system when it is determined that the photovoltaic access system resonates.

[0111] In another aspect, the present invention also provides a non-transitory computer-readable storage medium storing a computer program thereon, which, when executed by a processor, implements the photovoltaic grid connection system protection methods provided above. The method includes: performing impedance detection on the photovoltaic grid connection system to obtain a detected impedance; determining a calculated impedance of the photovoltaic grid connection system based on the current, voltage, and voltage-current phase angle of the photovoltaic grid connection system; if the detected impedance matches the calculated impedance, determining whether resonance exists in the photovoltaic grid connection system based on the reactance, capacitance, and angular frequency of the photovoltaic grid connection system; the angular frequency being determined based on the voltage-current phase; and adjusting the impedance of the photovoltaic grid connection system if resonance is determined to exist.

[0112] The device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs. Those skilled in the art can understand and implement this without any creative effort.

[0113] Through the above description of the embodiments, those skilled in the art can clearly understand that each embodiment can be implemented by means of software plus necessary general-purpose hardware platforms, and of course, it can also be implemented by hardware. Based on this understanding, the above technical solutions, in essence or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, magnetic disk, optical disk, etc., and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute the methods described in the various embodiments or some parts of the embodiments.

[0114] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A protection method for a photovoltaic grid connection system, characterized in that, include: Impedance detection is performed on the photovoltaic grid connection system to obtain the detection impedance of the photovoltaic grid connection system; The calculated impedance of the photovoltaic access system is determined based on the current, voltage, and voltage-current phase angle of the photovoltaic access system. If the detected impedance is consistent with the calculated impedance, the presence of resonance in the photovoltaic access system is determined based on the reactance, capacitance, and angular frequency of the photovoltaic access system. The angular frequency is determined based on the voltage and current phases; If resonance is determined in the photovoltaic access system, the impedance of the photovoltaic access system is adjusted. The step of adjusting the impedance of the photovoltaic grid connection system when resonance is determined to exist includes: If resonance is found in the photovoltaic access system, adjust the series or parallel circuit impedance of the photovoltaic access system. After adjusting the impedance of the photovoltaic grid connection system, the method further includes: The photovoltaic access system is subjected to resonance detection. If resonance exists in the photovoltaic access system, each photovoltaic inverter in the photovoltaic access system is taken out of the working mode in the order of voltage from large to small or current from large to small, until the photovoltaic access system eliminates resonance.

2. The photovoltaic grid connection system protection method according to claim 1, characterized in that, The determination of whether the photovoltaic access system exhibits resonance based on its reactance, capacitance, and angular frequency includes: Based on the reactance, capacitance, and angular frequency in the series circuit of the photovoltaic access system, determine whether voltage resonance exists in the photovoltaic access system; And / or, Based on the reactance, capacitance, and angular frequency in the parallel circuit of the photovoltaic access system, determine whether current resonance exists in the photovoltaic access system.

3. The photovoltaic grid connection system protection method according to claim 2, characterized in that, The determination of whether voltage resonance exists in the photovoltaic grid connection system based on the reactance, capacitance, and angular frequency in the series circuit of the photovoltaic grid connection system includes: If the reactance, capacitance, and angular frequency in the series circuit satisfy the voltage resonance model, it is determined that voltage resonance exists in the photovoltaic access system. The voltage resonance model is as follows: ; in, This represents the angular frequency in the series circuit. This represents the reactance in the series circuit. This represents the capacitance in the series circuit.

4. The photovoltaic grid connection system protection method according to claim 2, characterized in that, The determination of whether current resonance exists in the photovoltaic grid connection system based on the reactance, capacitance, and angular frequency in the parallel circuit of the photovoltaic grid connection system includes: If the reactance, capacitance, and angular frequency in the parallel circuit satisfy the current resonance model, it is determined that the photovoltaic access system has current resonance. The current resonance model is as follows: ; in, This represents the angular frequency in the parallel circuit. This represents the reactance in the parallel circuit. This represents the capacitance in the parallel circuit.

5. A protection device for a photovoltaic grid connection system, characterized in that, include: The detection unit allows the user to perform impedance detection on the photovoltaic access system and obtain the detection impedance of the photovoltaic access system. The calculation unit is used to determine the calculated impedance of the photovoltaic access system based on the current, voltage, and voltage-current phase angle of the photovoltaic access system. The determining unit is used to determine whether the photovoltaic access system has resonance based on the reactance, capacitance and angular frequency of the photovoltaic access system when the detected impedance is consistent with the calculated impedance. The angular frequency is determined based on the voltage and current phases; An adjustment unit is used to adjust the impedance of the photovoltaic access system when it is determined that resonance exists in the photovoltaic access system. The step of adjusting the impedance of the photovoltaic grid connection system when resonance is determined to exist includes: If resonance is found in the photovoltaic access system, adjust the series or parallel circuit impedance of the photovoltaic access system. After adjusting the impedance of the photovoltaic grid connection system, the method further includes: The photovoltaic access system is subjected to resonance detection. If resonance exists in the photovoltaic access system, each photovoltaic inverter in the photovoltaic access system is taken out of the working mode in the order of voltage from large to small or current from large to small, until the photovoltaic access system eliminates resonance.

6. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the program, it implements the photovoltaic access system protection method as described in any one of claims 1 to 4.

7. A non-transitory computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the photovoltaic access system protection method as described in any one of claims 1 to 4.

8. A computer program product, comprising a computer program, characterized in that, When the computer program is executed by the processor, it implements the photovoltaic access system protection method as described in any one of claims 1 to 4.

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