A method and system for calculating power loss of a photovoltaic power station

Abstract

The application discloses a kind of photovoltaic power station power loss amount calculation method and system, the photovoltaic power station unit after fault is divided into normal operation unit, low voltage ride through unit and off-grid unit, the proportion of each type of unit is calculated according to the active current and reactive current of grid-connected point, and the power loss amount of photovoltaic power station can be effectively calculated according to the proportion, to provide quantitative reference for accurate machine cutting and load cutting control strategy, improve the safety and stability of power grid under high proportion of new energy access.

Description

Technical Field

[0001] This invention relates to a method and system for calculating power loss in photovoltaic power plants, belonging to the field of power loss discrimination in photovoltaic power plants. Background Technology

[0002] In recent years, photovoltaic (PV) power generation technology has developed rapidly, and the scale of PV power generation connected to the grid has become increasingly large. The integration of numerous power electronic devices into the grid has not only changed the grid structure but also, due to its inherent vulnerability, makes it prone to large-scale grid disconnection accidents during faults. The resulting power losses pose a serious challenge to the safety and stability of the power grid. Domestic and international scholars have conducted limited research on the real-time calculation of power losses in PV power plants, and currently, there are no corresponding methods. Summary of the Invention

[0003] This invention provides a method and system for calculating the power loss of a photovoltaic power plant, which solves the problems disclosed in the background art.

[0004] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0005] A method for calculating the power loss of a photovoltaic power plant includes:

[0006] In response to the occurrence of a fault, the photovoltaic power station units are divided into normally operating units, low voltage ride-through units, and off-grid units. Based on the active current at the grid connection point of the photovoltaic power station at the moment before the fault occurs, the active current at the grid connection point of the photovoltaic power station in steady state after the fault occurs, and the reactive current at the grid connection point of the photovoltaic power station in steady state after the fault occurs, the proportion of normally operating units, the proportion of low voltage ride-through units, and the proportion of off-grid units in the photovoltaic power station are calculated.

[0007] Based on the proportion of normally operating units, the proportion of low voltage ride-through units, and the proportion of disconnected units in a photovoltaic power plant, calculate the power loss of the photovoltaic power plant during the fault period and the power loss of the photovoltaic power plant after the fault is cleared.

[0008] The formula for calculating the proportion of normally operating units, the proportion of low-voltage ride-through units, and the proportion of off-grid units in a photovoltaic power plant is as follows:

[0009]

[0010]

[0011] λ = 1 - θ - η

[0012] Where θ is the proportion of normally operating units in the photovoltaic power plant, η is the proportion of low voltage ride-through units, λ is the proportion of off-grid units, and i d_mea i represents the active current at the grid connection point of the photovoltaic power station under steady-state conditions after the fault occurs. q_meaThe reactive current at the grid connection point of the photovoltaic power station under steady-state conditions after the fault occurs, where m is the total number of photovoltaic power station units, and i d0 The active current at the grid connection point of the photovoltaic power station at the moment before the fault occurred, parameter i limit =1.2I N I N U is the rated current of the inverter. N U is the rated voltage at the grid connection point. d Let dq be the grid connection point voltage. The power factor angle of the unit under normal operation, and the reactive power setpoint of the inverter.

[0013] Based on the proportion of normally operating units, the proportion of low-voltage ride-through units, and the proportion of disconnected units in a photovoltaic power plant, calculate the power loss of the photovoltaic power plant during the fault and the power loss of the photovoltaic power plant after the fault is cleared, including:

[0014] Based on the proportion of normally operating units, the proportion of low voltage ride-through units, and the proportion of grid disconnected units in a photovoltaic power plant, calculate the capacity of normally operating units, the capacity of low voltage ride-through units, and the capacity of grid disconnected units during a fault.

[0015] Based on the capacity of the normally operating units, the capacity of the low-voltage ride-through units, and the capacity of the disconnected units during the fault, calculate the power loss of the photovoltaic power station during the fault and the power loss of the photovoltaic power station after the fault is cleared.

[0016] The normal operating capacity of the units during the fault period is the product of the total number of photovoltaic power plant units, the capacity of a single photovoltaic power plant unit, and the proportion of normally operating units in the photovoltaic power plant.

[0017] The low-voltage ride-through capacity during a fault is the product of the total number of photovoltaic power plant units, the capacity of a single photovoltaic power plant unit, and the proportion of low-voltage ride-through units in the photovoltaic power plant.

[0018] The off-grid capacity during a fault is the product of the total number of photovoltaic power plant units, the capacity of a single photovoltaic power plant unit, and the proportion of off-grid units in the photovoltaic power plant.

[0019] Based on the normally operating unit capacity, low-voltage ride-through unit capacity, and grid disconnected unit capacity during the fault, calculate the power loss of the photovoltaic power station during the fault and the power loss of the photovoltaic power station after the fault is cleared, including:

[0020] According to the principle of reactive power priority for low voltage ride-through of photovoltaic power plants, the power loss of photovoltaic power plants during the fault period is the sum of the capacity of normally operating units during the fault period and the capacity of low voltage ride-through units during the fault period.

[0021] After the fault is cleared, the low-voltage ride-through units of the photovoltaic power station resume normal operation, and the power loss of the photovoltaic power station is equal to the capacity of the units disconnected from the grid during the fault.

[0022] A photovoltaic power plant power loss calculation system includes:

[0023] The proportional calculation module, in response to the occurrence of a fault, divides the photovoltaic power station units into normally operating units, low voltage ride-through units, and off-grid units. Based on the active current of the photovoltaic power station grid connection point at the moment before the fault occurs, the active current of the photovoltaic power station grid connection point in steady state after the fault occurs, and the reactive current of the photovoltaic power station grid connection point in steady state after the fault occurs, it calculates the proportion of normally operating units, the proportion of low voltage ride-through units, and the proportion of off-grid units in the photovoltaic power station.

[0024] The power loss calculation module calculates the power loss of the photovoltaic power station during the fault period and the power loss of the photovoltaic power station after the fault is cleared, based on the proportion of normally operating units, the proportion of low voltage ride-through units, and the proportion of disconnected units in the photovoltaic power station.

[0025] The formulas used by the proportional calculation module to calculate the proportion of normally operating units, the proportion of low-voltage ride-through units, and the proportion of off-grid units in a photovoltaic power plant are as follows:

[0026]

[0027]

[0028] λ = 1 - θ - η

[0029] Where θ is the proportion of normally operating units in the photovoltaic power plant, η is the proportion of low voltage ride-through units, λ is the proportion of off-grid units, and i d_mea i represents the active current at the grid connection point of the photovoltaic power station under steady-state conditions after the fault occurs. q_mea The reactive current at the grid connection point of the photovoltaic power station under steady-state conditions after the fault occurs, where m is the total number of photovoltaic power station units, and i d0 The active current at the grid connection point of the photovoltaic power station at the moment before the fault occurred, parameter i limit =1.2I N I N U is the rated current of the inverter. N U is the rated voltage at the grid connection point. d Let dq be the grid connection point voltage. The power factor angle of the unit under normal operation, and the reactive power setpoint of the inverter.

[0030] The power loss calculation module is used to calculate the capacity of normally operating units, low voltage ride-through units, and grid-off units during a fault, based on the proportion of normally operating units, low voltage ride-through units, and grid-off units in the photovoltaic power plant. It also calculates the power loss of the photovoltaic power plant during the fault and the power loss of the photovoltaic power plant after the fault is cleared, based on the capacity of normally operating units, low voltage ride-through units, and grid-off units during the fault.

[0031] A computer-readable storage medium storing one or more programs, the one or more programs including instructions that, when executed by a computing device, cause the computing device to perform a method for calculating power loss in a photovoltaic power plant.

[0032] A computing device includes one or more processors, one or more memories, and one or more programs, wherein the one or more programs are stored in the one or more memories and configured to be executed by the one or more processors, and the one or more programs include instructions for performing a method for calculating power loss in a photovoltaic power plant.

[0033] The beneficial effects achieved by this invention are as follows: This invention divides the photovoltaic power plant units after a fault into normal operating units, low voltage ride-through units, and off-grid units. The proportion of each type of unit is calculated based on the active and reactive currents at the grid connection point. Based on the proportion, the power loss of the photovoltaic power plant can be effectively calculated, providing a quantitative reference for precise load shedding control strategies and improving the safety and stability of the power grid under high-proportion renewable energy access. Attached Figure Description

[0034] Figure 1 This is a flowchart of the method of the present invention;

[0035] Figure 2 This is a detailed flowchart of the method of the present invention;

[0036] Figure 3 This is a diagram of the simulation system structure.

[0037] Figure 4 The waveform diagram shows the simulation results of the active current of a photovoltaic power station.

[0038] Figure 5 The waveform diagram shows the simulation results of reactive current in a photovoltaic power plant. Detailed Implementation

[0039] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and should not be used to limit the scope of protection of the present invention.

[0040] like Figure 1 As shown, a method for calculating the power loss of a photovoltaic power station includes the following steps:

[0041] Step 1: In response to the occurrence of a fault, the photovoltaic power station units are divided into normally operating units, low voltage ride-through units, and off-grid units. Based on the active current at the grid connection point of the photovoltaic power station at the moment before the fault occurs, the active current at the grid connection point of the photovoltaic power station in steady state after the fault occurs, and the reactive current at the grid connection point of the photovoltaic power station in steady state after the fault occurs, the proportion of normally operating units, the proportion of low voltage ride-through units, and the proportion of off-grid units in the photovoltaic power station are calculated.

[0042] Step 2: Based on the proportion of normally operating units, the proportion of low voltage ride-through units, and the proportion of disconnected units in the photovoltaic power station, calculate the power loss of the photovoltaic power station during the fault and the power loss of the photovoltaic power station after the fault is cleared.

[0043] The above method classifies the photovoltaic power plant units after a fault into normal operating units, low voltage ride-through units, and disconnected units. The proportion of each type of unit is calculated based on the active and reactive currents at the grid connection point. Based on the proportion, the power loss of the photovoltaic power plant can be effectively calculated, providing a quantitative reference for precise load shedding control strategies and improving the safety and stability of the power grid under high-proportion renewable energy access.

[0044] like Figure 2 As shown, when implementing the method for calculating the power loss of a photovoltaic power station, the grid connection point of the photovoltaic power station can be monitored in real time. Specifically, active current and reactive current can be monitored. When a fault occurs, such as when a sudden change in current is detected, the photovoltaic power station units can be divided into normal operating units, low voltage ride-through units, and off-grid units according to the requirements of the photovoltaic power station grid connection low voltage ride-through specification.

[0045] To meet the requirements of the low voltage ride-through specification for grid connection of photovoltaic power plants, the specific control methods are as follows: Under normal operation, photovoltaic power plants are generally connected to the grid with unity power factor. When a fault occurs, reactive power is generated. The control strategy is divided into two parts: active power control and reactive power control.

[0046] The external regulation characteristics of the active power component mainly depend on the outer voltage loop, from which the control equation for the active current can be obtained:

[0047]

[0048] Among them, i d This is the reference value for the current in the active power control section. For DC link bus voltage limits, u dc The DC link bus voltage, k p1 k i1 These are the proportional and integral gain of the outer loop PI controller in the active power control section.

[0049] According to the technical regulations for connecting photovoltaic power plants to the power system, the reactive current output of a photovoltaic power plant should meet the following requirement:

[0050]

[0051] Among them, I q To output reactive current for photovoltaic power plants, I N U is the rated current of the inverter. N U is the rated voltage at the grid connection point. d The voltage at the grid connection point in the dq coordinate system;

[0052] The equation that the reactive current must satisfy can be as follows:

[0053]

[0054] Where, k p2 k i2 These represent the proportional and integral gain of the outer-loop PI controller in the reactive power control section. i is the reactive power setpoint for the inverter. q L represents the reactive component of the grid-side current, and L is the inverter inductance.

[0055] Due to the inherent capacity limitations of the inverter, the active current must satisfy the following inequality constraint:

[0056]

[0057] Wherein, parameter i limit =1.2I N

[0058] The control model for a photovoltaic power station during low-voltage ride-through is shown in the following equation:

[0059]

[0060] Where C is the DC link voltage regulator capacitor, P W U is the maximum output power of the photovoltaic unit. d I d These represent the grid connection point voltage and current in the dq coordinate system, U. r ω represents the equivalent voltage loss of the inverter, and ω is the angular frequency.

[0061] After a fault occurs, due to the influence of actual factors such as different transmission line impedances, under the control of the above model, photovoltaic power station units can be divided into normal operating units, low voltage ride-through units, and grid disconnected units. The proportion of normal operating units is defined as θ, the proportion of low voltage ride-through units is defined as η, and the proportion of grid disconnected units is defined as λ, where θ + η + λ = 1.

[0062] Assuming a photovoltaic power station has m units, each with a capacity of aMW, the capacity of the three types of units can be determined by setting the above ratio.

[0063] According to Kirchhoff's current law, the active current I at the photovoltaic field outlet monitoring point is... dΣ and reactive current I dΣ , can be represented as:

[0064]

[0065] Considering that all generating units have similar active and reactive power output characteristics under the same control strategy, then

[0066]

[0067]

[0068] Among them, i d_mea i represents the active current at the grid connection point of the photovoltaic power station under steady-state conditions after the fault occurs. q_mea i represents the reactive current at the grid connection point of the photovoltaic power station under steady-state conditions after the fault occurs. d_lvrt i represents the active current output by the low-voltage ride-through unit. q_normal i is the reactive current output by the unit during normal operation. dΣ_cal Let i be the sum of the active current output when all units are operating normally. qΣ_cal This is the sum of the reactive currents output when all voltages of the unit are through.

[0069] Given the power factor of the unit under normal operation but

[0070]

[0071] According to the above formula, the proportions of various types of units are:

[0072]

[0073]

[0074] λ = 1 - θ - η

[0075] Among them, i d0 This refers to the active current at the grid connection point of the photovoltaic power station just moments before the fault occurred. The power factor angle of the unit under normal operation; the power factor of the unit under normal operation. Inverter reactive power setpoint

[0076]

[0077] Based on the active current at the grid-connected point of the photovoltaic power station just before the fault occurred, the active current at the grid-connected point of the photovoltaic power station in steady state after the fault occurred, and the reactive current at the grid-connected point of the photovoltaic power station in steady state after the fault occurred, the proportion of normally operating units, the proportion of low voltage ride-through units, and the proportion of disconnected units in the photovoltaic power station can be calculated.

[0078] Once the proportions are calculated, the capacity of normally operating units, low-voltage ride-through units, and grid-off units during a fault period can be calculated based on the proportions of normally operating units, low-voltage ride-through units, and grid-off units in the photovoltaic power plant. Specifically, the capacity of normally operating units during a fault period is the product of the total number of photovoltaic power plant units, the capacity of each unit, and the proportion of normally operating units in the photovoltaic power plant. The capacity of low-voltage ride-through units during a fault period is the product of the total number of photovoltaic power plant units, the capacity of each unit, and the proportion of low-voltage ride-through units in the photovoltaic power plant. The capacity of grid-off units during a fault period is the product of the total number of photovoltaic power plant units, the capacity of each unit, and the proportion of grid-off units in the photovoltaic power plant. These can be expressed by the formulas maθ, maη, and maλ, respectively.

[0079] Furthermore, based on the capacity of normally operating units, the capacity of low-voltage ride-through units, and the capacity of units disconnected from the grid during the fault, the power loss of the photovoltaic power station during the fault and the power loss of the photovoltaic power station after the fault is cleared can be calculated as follows: According to the reactive power priority principle of low-voltage ride-through of photovoltaic power stations, the power loss of photovoltaic power stations during the fault is the sum of the capacity of normally operating units and the capacity of low-voltage ride-through units during the fault, ΔP1=maη+maλ; after the fault is cleared, the low-voltage ride-through units of the photovoltaic power station return to normal operation, and the power loss of the photovoltaic power station is the capacity of the units disconnected from the grid during the fault, ΔP2=maλ.

[0080] To verify the above method, a 9MW trunk-type photovoltaic power plant simulation system was built in PSCAD / EMTDC (see [link]). Figure 3 Three 3MW PV units are connected to the photovoltaic power station bus via a transformer substation and collector lines, and then transmitted to the main power grid via a step-up transformer and a 220kV overhead line. A single-phase ground fault is set at the midpoint of the 220kV overhead line, and the grid connection point current is monitored to perform simulation analysis of the fault steady state.

[0081] When the system reached 0.3s, a short-circuit ground fault occurred on phase A of the 220kV overhead line, and the grid connection voltage dropped to 0pu. The three photovoltaic units were in normal operation, low voltage ride-through, and grid disconnection states, respectively. Power factor of a unit under normal operation Photovoltaic unit output current such as Figure 4 and Figure 5 As shown, the active current of PV1 under normal operation fluctuates but remains at its rated value, while the reactive current remains zero; the active current of PV2 undergoing low-voltage ride-through decreases significantly, while the reactive current increases sharply; the output current of PV3 disconnected from the grid is not zero. A system of equations for θ, η, and λ can be obtained:

[0082]

[0083] Solving for θ, we get θ = 0.333, η = 0.346, and λ = 0.321. Ignoring the errors caused by the simulation environment, the actual value of the off-grid capacity ratio of the unit is basically consistent with the calculated value. The power loss of the photovoltaic power station during the fault is 6.003MW. After the fault is cleared, the low voltage ride-through unit of the photovoltaic power station returns to normal operation. The power loss caused by the off-grid disconnection of the photovoltaic unit is 2.889MW.

[0084] The above method can accurately determine the power loss of photovoltaic power plants during voltage dips, providing technical support for the formulation of grid stability control measures such as shelving and load shelving. It is conducive to realizing grid stability control measures such as precise shelving and load shelving. Moreover, the determination process only requires monitoring the grid connection point current of the photovoltaic power plant, with low computational load, high real-time performance, and low implementation cost.

[0085] Based on the same technical solution, this invention also discloses a software system for the above method, a photovoltaic power plant power loss calculation system, comprising:

[0086] The proportional calculation module, in response to a fault, divides the photovoltaic power plant into normally operating units, low-voltage ride-through units, and off-grid units according to the requirements of the photovoltaic power plant grid-connected low-voltage ride-through specification. Based on the active current of the photovoltaic power plant grid-connected point at the moment before the fault, the active current of the photovoltaic power plant grid-connected point in steady state after the fault, and the reactive current of the photovoltaic power plant grid-connected point in steady state after the fault, it calculates the proportion of normally operating units, low-voltage ride-through units, and off-grid units in the photovoltaic power plant.

[0087] The formulas used by the proportional calculation module to calculate the proportion of normally operating units, the proportion of low-voltage ride-through units, and the proportion of off-grid units in a photovoltaic power plant are as follows:

[0088]

[0089]

[0090] λ = 1 - θ - η

[0091] Where θ is the proportion of normally operating units in the photovoltaic power plant, η is the proportion of low voltage ride-through units, λ is the proportion of off-grid units, and i d_mea i represents the active current at the grid connection point of the photovoltaic power station under steady-state conditions after the fault occurs. q_mea The reactive current at the grid connection point of the photovoltaic power station under steady-state conditions after the fault occurs, where m is the total number of photovoltaic power station units, and i d0 The active current at the grid connection point of the photovoltaic power station at the moment before the fault occurred, parameter i limit =1.2I N I N U is the rated current of the inverter. N U is the rated voltage at the grid connection point. dLet dq be the grid connection point voltage. The power factor angle of the unit under normal operation; the power factor of the unit under normal operation. Inverter reactive power setpoint

[0092] The power loss calculation module calculates the power loss of the photovoltaic power station during the fault period and the power loss of the photovoltaic power station after the fault is cleared, based on the proportion of normally operating units, the proportion of low voltage ride-through units, and the proportion of disconnected units in the photovoltaic power station.

[0093] The power loss calculation module is used to calculate the capacity of normally operating units, low voltage ride-through units, and grid-off units during a fault, based on the proportion of normally operating units, low voltage ride-through units, and grid-off units in the photovoltaic power plant. It also calculates the power loss of the photovoltaic power plant during the fault and the power loss of the photovoltaic power plant after the fault is cleared, based on the proportion of normally operating units, low voltage ride-through units, and grid-off units in the photovoltaic power plant.

[0094] Based on the same technical solution, the present invention also discloses a computer-readable storage medium storing one or more programs, the one or more programs including instructions that, when executed by a computing device, cause the computing device to perform a method for calculating the power loss of a photovoltaic power station.

[0095] Based on the same technical solution, the present invention also discloses a computing device, including one or more processors, one or more memories, and one or more programs, wherein the one or more programs are stored in the one or more memories and configured to be executed by the one or more processors, and the one or more programs include instructions for executing a method for calculating the power loss of a photovoltaic power plant.

[0096] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0097] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0098] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0099] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0100] The above are merely embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention are included within the scope of the claims of the present invention pending approval.

Claims

1. A method for calculating power loss in a photovoltaic power plant, characterized in that, include: In response to the occurrence of a fault, the photovoltaic power station units are divided into normally operating units, low voltage ride-through units, and off-grid units. Based on the active current at the grid connection point of the photovoltaic power station at the moment before the fault occurs, the active current at the grid connection point of the photovoltaic power station in steady state after the fault occurs, and the reactive current at the grid connection point of the photovoltaic power station in steady state after the fault occurs, the proportion of normally operating units, the proportion of low voltage ride-through units, and the proportion of off-grid units in the photovoltaic power station are calculated. The formulas used to calculate the proportion of normally operating units, the proportion of low-voltage ride-through units, and the proportion of grid-connected units in a photovoltaic power plant are as follows: ； ； ； Where θ is the proportion of normally operating units in the photovoltaic power plant, η is the proportion of low voltage ride-through units, λ is the proportion of off-grid units, and i d_mea i represents the active current at the grid connection point of the photovoltaic power station under steady-state conditions after the fault occurs. q_mea The reactive current at the grid connection point of the photovoltaic power station under steady-state conditions after the fault occurs, where m is the total number of photovoltaic power station units, and i d0 The active current at the grid connection point of the photovoltaic power station at the moment before the fault occurred, parameter i limit =1.2I N I N U is the rated current of the inverter. N U is the rated voltage at the grid connection point. d Let dq be the grid connection point voltage. The power factor angle of the unit under normal operation, and the reactive power setpoint of the inverter. ; Based on the proportion of normally operating units, the proportion of low voltage ride-through units, and the proportion of disconnected units in a photovoltaic power plant, calculate the power loss of the photovoltaic power plant during the fault period and the power loss of the photovoltaic power plant after the fault is cleared.

2. The method for calculating power loss in a photovoltaic power station according to claim 1, characterized in that, Based on the proportion of normally operating units, the proportion of low-voltage ride-through units, and the proportion of disconnected units in a photovoltaic power plant, calculate the power loss of the photovoltaic power plant during the fault and the power loss of the photovoltaic power plant after the fault is cleared, including: Based on the proportion of normally operating units, the proportion of low voltage ride-through units, and the proportion of grid disconnected units in a photovoltaic power plant, calculate the capacity of normally operating units, the capacity of low voltage ride-through units, and the capacity of grid disconnected units during a fault. Based on the capacity of the normally operating units, the capacity of the low-voltage ride-through units, and the capacity of the disconnected units during the fault, calculate the power loss of the photovoltaic power station during the fault and the power loss of the photovoltaic power station after the fault is cleared.

3. The method for calculating power loss in a photovoltaic power station according to claim 2, characterized in that, The normal operating capacity of the photovoltaic power plant during the fault period is the product of the total number of photovoltaic power plant units, the capacity of each photovoltaic power plant unit, and the proportion of normally operating units in the photovoltaic power plant. The low-voltage ride-through capacity during a fault is the product of the total number of photovoltaic power plant units, the capacity of a single photovoltaic power plant unit, and the proportion of low-voltage ride-through units in the photovoltaic power plant. The off-grid capacity during a fault is the product of the total number of photovoltaic power plant units, the capacity of a single photovoltaic power plant unit, and the proportion of off-grid units in the photovoltaic power plant.

4. The method for calculating power loss in a photovoltaic power station according to claim 2, characterized in that, Based on the normally operating unit capacity, low-voltage ride-through unit capacity, and grid disconnected unit capacity during the fault, calculate the power loss of the photovoltaic power station during the fault and the power loss of the photovoltaic power station after the fault is cleared, including: According to the principle of reactive power priority for low voltage ride-through of photovoltaic power plants, the power loss of photovoltaic power plants during the fault period is the sum of the capacity of normally operating units during the fault period and the capacity of low voltage ride-through units during the fault period. After the fault is cleared, the low-voltage ride-through units of the photovoltaic power station resume normal operation, and the power loss of the photovoltaic power station is equal to the capacity of the units disconnected from the grid during the fault.

5. A photovoltaic power plant power loss calculation system, characterized in that, include: The proportional calculation module, in response to the occurrence of a fault, divides the photovoltaic power station units into normally operating units, low voltage ride-through units, and off-grid units. Based on the active current of the photovoltaic power station grid connection point at the moment before the fault occurs, the active current of the photovoltaic power station grid connection point in steady state after the fault occurs, and the reactive current of the photovoltaic power station grid connection point in steady state after the fault occurs, it calculates the proportion of normally operating units, the proportion of low voltage ride-through units, and the proportion of off-grid units in the photovoltaic power station. The formulas used in the proportional calculation module to calculate the proportion of normally operating units, the proportion of low-voltage ride-through units, and the proportion of off-grid units in a photovoltaic power plant are as follows: ； ； ； Where θ is the proportion of normally operating units in the photovoltaic power plant, η is the proportion of low voltage ride-through units, λ is the proportion of off-grid units, and i d_mea i represents the active current at the grid connection point of the photovoltaic power station under steady-state conditions after the fault occurs. q_mea The reactive current at the grid connection point of the photovoltaic power station under steady-state conditions after the fault occurs, where m is the total number of photovoltaic power station units, and i d0 The active current at the grid connection point of the photovoltaic power station at the moment before the fault occurred, parameter i limit =1.2I N I N U is the rated current of the inverter. N U is the rated voltage at the grid connection point. d Let dq be the grid connection point voltage. The power factor angle of the unit under normal operation, and the reactive power setpoint of the inverter. ; The power loss calculation module calculates the power loss of the photovoltaic power station during the fault period and the power loss of the photovoltaic power station after the fault is cleared, based on the proportion of normally operating units, the proportion of low voltage ride-through units, and the proportion of disconnected units in the photovoltaic power station.

6. The photovoltaic power station power loss calculation system according to claim 5, characterized in that, The loss calculation is used to calculate the capacity of normally operating units, low voltage ride-through units, and grid-off units during a fault, based on the proportion of normally operating units, low voltage ride-through units, and grid-off units in the photovoltaic power plant. Based on the capacity of normally operating units, low voltage ride-through units, and grid-off units during the fault, the power loss of the photovoltaic power plant during the fault and the power loss of the photovoltaic power plant after the fault is cleared are calculated.

7. A computer-readable storage medium for storing one or more programs, characterized in that, The one or more programs include instructions that, when executed by a computing device, cause the computing device to perform any of the methods according to claims 1 to 4.

8. A computing device, characterized in that, include: One or more processors, one or more memories, and one or more programs, wherein the one or more programs are stored in the one or more memories and configured to be executed by the one or more processors, the one or more programs including instructions for performing any of the methods according to claims 1 to 4.

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