CN115344828A - A method and system for calculating the power loss of a photovoltaic power station - Google Patents

Abstract

The invention discloses a method and a system for calculating power loss of a photovoltaic power station.

Description

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

technical field

The invention relates to a method and system for calculating the power loss amount of a photovoltaic power station, belonging to the field of power loss judgment of a photovoltaic power station.

Background technique

In recent years, photovoltaic power generation technology has developed rapidly, and the grid-connected scale of photovoltaic power generation has become larger and larger. A large number of power electronic devices have been connected to the power grid, which not only changes the shape of the power grid, but also makes it prone to large-scale off-grid accidents when faults occur, resulting in The power loss has brought severe challenges to the security and stability of the power grid. Scholars at home and abroad have little research on the real-time calculation of power loss in photovoltaic power plants, and there is no corresponding method at present.

Contents of the invention

The invention provides a method and system for calculating the power loss amount of a photovoltaic power station, which solves the problems disclosed in the background technology.

In order to solve the problems of the technologies described above, the technical solution adopted in the present invention is:

A method for calculating the power loss of a photovoltaic power station, comprising:

In response to the occurrence of a fault, the units of the photovoltaic power station are divided into normal operation units, low-voltage ride-through units and off-grid units. and the reactive current of the grid-connected point of the photovoltaic power station in the steady state after the fault occurs, and calculate the proportion of the normal operation unit, the proportion of the low voltage ride-through unit and the proportion of the off-grid unit in the photovoltaic power station;

According to the proportion of normal operating units in the photovoltaic power station, the proportion of low-voltage ride-through units and the proportion of off-grid units, 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 removed are calculated.

Calculate the proportion of normal operating units, the proportion of low voltage ride-through units and the proportion of off-grid units in the photovoltaic power station, the formula is:

λ=1-θ-η

为正常运行的机组功率因数角，逆变器无功给定值

Among them, θ is the proportion of normal operating units in the photovoltaic power station, η is the proportion of low-voltage ride-through units, λ is the proportion of off-grid units, id_mea is the active current of the _{grid-connected point of the photovoltaic power station in the steady state after the fault occurs, and i q_mea is} The reactive current of the grid-connected point of the photovoltaic power station in the steady state after the fault occurs, m is the total number of units of the photovoltaic power station, and i _d0 is the active current of the grid-connected point of the photovoltaic power station _at the moment before the fault occurs, the parameter i _limit = 1.2IN, and I _N is the inverter The rated current of the device, U _N is the rated voltage of the grid-connected point, U _d is the voltage of the grid-connected point under dq coordinates,

is the power factor angle of the unit in normal operation, and the reactive power reference value of the inverter

According to the proportion of normal operating units in the photovoltaic power station, the proportion of low-voltage ride-through units and the proportion of off-grid units, calculate 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 removed, including:

According to the proportion of normal operating units, the proportion of low voltage ride through units and the proportion of off-grid units in the photovoltaic power station, the capacity of normal operation units, low voltage ride through units and off-grid units during the fault period is calculated;

According to the normal operating unit capacity, low voltage ride-through unit capacity and off-grid unit capacity during the fault period, 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 removed are calculated.

The normal operating unit capacity during the fault period is the product of the total number of photovoltaic power station units, the single unit capacity of photovoltaic power station units and the proportion of normal operating units in the photovoltaic power station;

The low-voltage ride-through unit capacity during the fault period is the product of the total number of photovoltaic power station units, the single-unit capacity of photovoltaic power station units and the proportion of low-voltage ride-through units in the photovoltaic power station;

The capacity of the off-grid unit during the fault period is the product of the total number of photovoltaic power station units, the unit capacity of the photovoltaic power station unit and the proportion of off-grid units in the photovoltaic power station.

According to the normal operating unit capacity, low voltage ride-through unit capacity and off-grid unit capacity during the fault period, calculate 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 removed, including:

According to the principle of reactive power priority for photovoltaic power station low voltage ride through, the power loss of photovoltaic power station during the fault period is the sum of the capacity of the normal operation unit during the fault period and the capacity of the low voltage ride through unit during the fault period;

After the fault is removed, the low-voltage ride-through unit of the photovoltaic power station returns to normal operation, and the power loss of the photovoltaic power station is the capacity of the off-grid unit during the fault period.

A photovoltaic power station power loss calculation system, comprising:

The proportion calculation module, in response to a fault, divides the photovoltaic power plant units into normal operation units, low voltage ride-through units and off-grid units. The active current of the network point and the reactive current of the grid-connected point of the photovoltaic power station in the steady state after the fault occurs, calculate the proportion of normal operation units, the proportion of low voltage ride-through units and the proportion of off-grid units in the photovoltaic power station;

The loss amount 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 removed according to the proportion of the normal operation unit, the proportion of the low voltage ride-through unit and the proportion of the off-grid unit in the photovoltaic power station.

The ratio calculation module calculates the formulas for calculating the proportion of normal operation units, low voltage ride-through units and off-grid units in photovoltaic power plants as follows:

λ=1-θ-η

为正常运行的机组功率因数角，逆变器无功给定值

Among them, θ is the proportion of normal operating units in the photovoltaic power station, η is the proportion of low-voltage ride-through units, λ is the proportion of off-grid units, id_mea is the active current of the _{grid-connected point of the photovoltaic power station in the steady state after the fault occurs, and i q_mea is} The reactive current of the grid-connected point of the photovoltaic power station in the steady state after the fault occurs, m is the total number of units of the photovoltaic power station, and i _d0 is the active current of the grid-connected point of the photovoltaic power station _at the moment before the fault occurs, the parameter i _limit = 1.2IN, and I _N is the inverter The rated current of the device, U _N is the rated voltage of the grid-connected point, U _d is the voltage of the grid-connected point under dq coordinates,

is the power factor angle of the unit in normal operation, and the reactive power reference value of the inverter

The loss amount calculation module is used to calculate the capacity of normal operating units, low voltage During the normal operation unit capacity, low voltage ride through unit capacity and off-grid unit capacity, calculate 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 removed.

A computer-readable storage medium that stores one or more programs, and the one or more programs include instructions that, when executed by a computing device, cause the computing device to execute a method for calculating the power loss amount of a photovoltaic power plant.

A computing device comprising 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 Executed by multiple processors, the one or more programs include instructions for executing the method for calculating the power loss amount of the photovoltaic power station.

The beneficial effects achieved by the present invention: the present invention divides the faulty photovoltaic power plant units into normal operation units, low-voltage ride-through units and off-grid units, and calculates the proportion of various units according to the active current and reactive current of the grid-connected point. The ratio can effectively calculate the power loss of photovoltaic power plants, provide a quantitative reference for precise machine-cutting and load-cutting control strategies, and improve the security and stability of the power grid under a high proportion of new energy access.

Description of drawings

Fig. 1 is the flowchart of the inventive method;

Fig. 2 is the detailed flowchart of the inventive method;

Figure 3 is a structural diagram of the simulation system;

Fig. 4 is a waveform diagram of the simulation result of the active current of the photovoltaic power station;

Fig. 5 is a waveform diagram of the reactive current simulation result of the photovoltaic power station.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings. The following examples are only used to illustrate the technical solution of the present invention more clearly, but not to limit the protection scope of the present invention.

As shown in Figure 1, a method for calculating the power loss of a photovoltaic power station includes the following steps:

Step 1. In response to the occurrence of a fault, the units of the photovoltaic power station are divided into normal operation units, low-voltage ride-through units and off-grid units. The active current of the photovoltaic power station and the reactive current of the grid-connected point of the photovoltaic power station in the steady state after the fault occurs, and calculate the proportion of the normal operation unit, the proportion of the low voltage ride-through unit and the proportion of the off-grid unit in the photovoltaic power station;

Step 2. Calculate 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 removed according to the proportion of the normal operation unit, the proportion of the low voltage ride-through unit and the proportion of the off-grid unit in the photovoltaic power station.

The above method divides the faulty photovoltaic power plant units into normal operation units, low-voltage ride-through units and off-grid units, and calculates the proportion of various units according to the active current and reactive current of the grid-connected point, and can effectively calculate the photovoltaic power plant power according to the proportion. The amount of loss provides a quantitative reference for precise machine-cutting and load-cutting control strategies, and improves the security and stability of the power grid under a high proportion of new energy access.

As shown in Figure 2, when implementing the calculation method for the power loss of photovoltaic power plants, real-time monitoring of the grid-connected points of photovoltaic power plants can be carried out. Specifically, active current and reactive current can be monitored. According to the requirements of low voltage ride-through regulations for grid-connected power plants, photovoltaic power plant units are divided into normal operation units, low voltage ride-through units and off-grid units.

In order to meet the grid-connected low-voltage ride-through requirements of photovoltaic power stations, the specific control methods are as follows: During normal operation, photovoltaics are generally connected to the grid with a unit power factor. When a fault occurs, reactive power will be generated. The control strategy is divided into active power control and reactive power control. two parts.

The external adjustment characteristics of the active part mainly depend on the voltage outer loop, and the control equation of the active current can be obtained:

为直流环节母线电压限值，u_dc为直流环节母线电压，k_p1、k_i1分别为有功控制部分外环PI控制器容量比例和积分增益。Among them, i _d is the current reference value of the active power control part,

is the DC link bus voltage limit, u _dc is the DC link bus voltage, k _p1 and k _i1 are the capacity ratio and integral gain of the outer loop PI controller of the active power control part, respectively.

It can be seen from the technical regulations on the connection of photovoltaic power stations to the power system that the output reactive current of photovoltaic power stations should meet the following requirements:

Among them, I _q is the output reactive current of the photovoltaic power station, I _N is the rated current of the inverter, U _N is the rated voltage of the grid-connected point, and U _d is the voltage of the grid-connected point under dq coordinates;

Then the equation that the reactive current satisfies can be as follows:

为逆变器无功给定值，i_q为网侧电流中的无功分量，L为逆变器电感。Among them, k _p2 and k _i2 are respectively the capacity ratio and integral gain of the outer loop PI controller of the reactive power control part,

Inverter reactive power given value, i _q is reactive component in grid side current, L is inverter inductance.

Due to the capacity limitation of the inverter itself, the active current should satisfy the following inequality constraints:

Among them, the parameter i _limit =1.2I _N

Then, during the low voltage ride through process, the control model of the photovoltaic power station is shown in the following formula:

Among them, C is the DC link voltage stabilizing capacitor, P _W is the maximum output power of the photovoltaic unit, U _d and I _d are the voltage and current of the grid-connected point under dq coordinates, U _r is the equivalent voltage loss of the inverter, and ω is the angle frequency.

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 plant units can be divided into normal operation units, low voltage ride-through units and off-grid units, where the ratio of normal operation units is defined as θ , the proportion of low-voltage ride-through units is η, the proportion of off-grid units is λ, θ+η+λ=1.

Assuming that there are m units in the photovoltaic power station, and the capacity of each unit is aMW, the capacity of the three types of units can be determined by determining the above ratio.

According to Kirchhoff's current law, the active current _IdΣ and reactive current _IdΣ at the outlet monitoring point of the photovoltaic electric field can be expressed as:

Considering that each unit has similar active and reactive power output characteristics under the same control strategy, then

Among them, id_mea is the active current of the _{grid-connected point of the photovoltaic power station in the steady state after the fault occurs, i q_mea is} the reactive current of the grid-connected point of the photovoltaic power station in the steady state after the fault occurs, and _{id_lvrt} is the active current output by the low-voltage ride-through unit, i _{q_normal} is the reactive current output by the units in normal operation, i _{dΣ_cal} is the sum of the active currents output when all the units are operating normally, and i _{qΣ_cal} is the sum of the reactive currents output when all the units are assumed to be running through voltage;

则Known, normal operating unit power factor

but

According to the above formula, the proportion of various units can be obtained as follows:

λ=1-θ-η

为正常运行的机组功率因数角，正常运行的机组功率因数

逆变器无功给定值Among them, i _d0 is the active current of the grid-connected point of the photovoltaic power station at the moment before the fault occurs,

is the power factor angle of the unit in normal operation, and the power factor of the unit in normal operation

Inverter reactive power reference

That is, according to the active current of the grid-connected point of the photovoltaic power station immediately before the fault, the active current of the grid-connected point of the photovoltaic power station in the steady state after the fault occurs, and the reactive current of the grid-connected point of the photovoltaic power station in the steady state after the fault occurs, the normal power of the photovoltaic power station can be calculated. The proportion of operating units, the proportion of low-voltage ride-through units and the proportion of off-grid units.

In the case of calculating the ratio, the capacity of the normal operation unit, the capacity of the low voltage ride-through unit and the capacity of the off-grid unit can be calculated according to the proportion of the normal operation unit, the proportion of the low voltage ride-through unit and the proportion of the off-grid unit in the photovoltaic power station ; Among them, the normal operating unit capacity during the fault period is the product of the total number of photovoltaic power station units, the single unit capacity of photovoltaic power station units and the proportion of normal operating units in the photovoltaic power station, and the low voltage ride-through unit capacity during the fault period is the total number of photovoltaic power station units, the single unit capacity of photovoltaic power station units and The product of the proportion of low-voltage ride-through units in the photovoltaic power station, the capacity of off-grid units during a fault is the product of the total number of photovoltaic power station units, the unit capacity of photovoltaic power station units and the proportion of off-grid units in the photovoltaic power station, which can be expressed as: maθ, maη, ma lambda.

Further, 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 removed can be calculated according to the capacity of the normal operating unit during the fault period, the capacity of the low-voltage ride-through unit and the capacity of the off-grid unit. According to the principle of power priority, the power loss of the photovoltaic power station during the fault period is the sum of the capacity of the normal operating unit during the fault period and the capacity of the low-voltage ride-through unit during the fault period ΔP ₁ = maη+maλ; after the fault is removed, the low-voltage ride-through unit of the photovoltaic power station returns to normal operation. The power loss amount of the photovoltaic power station is the capacity of the off-grid unit during the fault period ΔP ₂ =maλ.

In order to verify the above method, a 9MW trunk-line photovoltaic power station simulation system was built in PSCAD/EMTDC, as shown in Figure 3. Three groups of PVs with a capacity of 3MW are connected to the busbar of the photovoltaic power station through box transformers and collector lines, and then connected to the 220kV overhead line through a step-up transformer. sent to the large grid. Set a single-phase ground short-circuit fault at the midpoint of the 220kV overhead line, monitor the current at the grid-connected point, and conduct simulation analysis on the fault steady state.

正常运行的机组功率因数

光伏机组输出电流如图4与图5所示，正常运行的PV1的有功电流有所波动，但依然能保持在额定值，无功电流则保持为0；低电压穿越的PV2的有功电流有明显下降，无功电流则突增；脱网的PV3的输出电流皆未0。可得到关于θ、η、λ的方程组：When the system runs for 0.3s, a short-circuit ground fault occurs on phase A of the 220kV overhead line, and the voltage at the grid connection point drops to 0pu.

Normal operating unit power factor

The output current of the photovoltaic unit is shown in Figure 4 and Figure 5. The active current of PV1 under normal operation fluctuates, but it can still be maintained at the rated value, and the reactive current remains at 0; the active current of PV2 under low voltage ride-through has obvious The reactive current increases suddenly; the output current of the off-grid PV3 is not 0. A system of equations about θ, η, λ can be obtained:

The solution is θ=0.333, η=0.346, λ=0.321, ignoring the error caused by the simulation environment, the actual value of the off-grid capacity ratio of the unit is basically consistent with the calculated value, and the power loss of the photovoltaic power station during the fault period is 6.003MW; The low-voltage ride-through unit of the power station returned to normal operation, and the power loss caused by the off-grid of the photovoltaic unit was 2.889MW.

The above method can more accurately judge the power loss of photovoltaic power plants during the voltage drop period, and provide technical support for the formulation of power grid stability control measures such as machine and load shedding, which is conducive to the realization of stable control measures such as precise machine and load shedding, and the identification process It only needs to monitor the grid-connected point current of the photovoltaic power station, with a small amount of calculation, high real-time performance, and low implementation cost.

Based on the same technical solution, the present invention also discloses the software system of the above method, a photovoltaic power station power loss calculation system, including:

The proportion calculation module, in response to a fault, divides the photovoltaic power plant units into normal operation units, low voltage ride-through units and off-grid units according to the grid-connected low-voltage ride-through specification requirements of photovoltaic power plants, and according to the active power of the grid-connected point of the photovoltaic power station at the moment before the fault occurs Calculate the proportion of normal operating units in photovoltaic power plants, the proportion of low voltage ride-through units and off-grid The proportion of the unit.

The ratio calculation module calculates the formulas for calculating the proportion of normal operation units, low voltage ride-through units and off-grid units in photovoltaic power plants as follows:

λ=1-θ-η

为正常运行的机组功率因数角，正常运行的机组功率因数

逆变器无功给定值

Among them, θ is the proportion of normal operating units in the photovoltaic power station, η is the proportion of low-voltage ride-through units, λ is the proportion of off-grid units, id_mea is the active current of the _{grid-connected point of the photovoltaic power station in the steady state after the fault occurs, and i q_mea is} The reactive current of the grid-connected point of the photovoltaic power station in the steady state after the fault occurs, m is the total number of units of the photovoltaic power station, and i _d0 is the active current of the grid-connected point of the photovoltaic power station _at the moment before the fault occurs, the parameter i _limit = 1.2IN, and I _N is the inverter The rated current of the device, U _N is the rated voltage of the grid-connected point, U _d is the voltage of the grid-connected point under dq coordinates,

is the power factor angle of the unit in normal operation, and the power factor of the unit in normal operation

Inverter reactive power reference

The loss amount 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 removed according to the proportion of the normal operation unit, the proportion of the low voltage ride-through unit and the proportion of the off-grid unit in the photovoltaic power station.

The loss amount calculation module is used to calculate the capacity of normal operating units, low voltage During the normal operation unit capacity, low voltage ride through unit capacity and off-grid unit capacity, calculate 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 removed.

Based on the same technical solution, the present invention also discloses a computer-readable storage medium that stores one or more programs, and the one or more programs include instructions that, when executed by a computing device, cause the computing The device executes the method for calculating the power loss amount of the photovoltaic power station.

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 one or more programs are stored in the one or more In the memory and configured to be executed by the one or more processors, the one or more programs include instructions for executing the method for calculating the power loss amount of the photovoltaic power plant.

Those skilled in the art should understand that the embodiments of the present invention may be provided as methods, systems, or computer program products. Accordingly, the present invention can take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention may 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.) having computer-usable program code embodied therein.

The present 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 should be understood that each procedure and/or block in the flowchart and/or block diagram, and a combination of procedures and/or blocks in the flowchart and/or block diagram can be realized by computer program instructions. These computer program instructions may be provided to a general purpose computer, special purpose computer, embedded processor, or processor of other programmable data processing equipment to produce a machine such that the instructions executed by the processor of the computer or other programmable data processing equipment produce a An apparatus for realizing the functions specified in one or more procedures of the flowchart and/or one or more blocks of the block diagram.

These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing apparatus to operate in a specific manner, such that the instructions stored in the computer-readable memory produce an article of manufacture comprising instruction means, the instructions The device realizes the function specified in one or more procedures of the flowchart and/or one or more blocks of the block diagram.

These computer program instructions can also be loaded onto a computer or other programmable data processing device, causing a series of operational steps to be performed on the computer or other programmable device to produce a computer-implemented process, thereby The instructions provide steps for implementing the functions specified in the flow chart or blocks of the flowchart and/or the block or blocks of the block diagrams.

The above are only embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention are included in the pending application of the present invention. within the scope of the claims.

Claims (10)

1. A method for calculating the power loss of a photovoltaic power station, comprising: In response to the occurrence of a fault, the units of the photovoltaic power station are divided into normal operation units, low-voltage ride-through units and off-grid units. and the reactive current of the grid-connected point of the photovoltaic power station in the steady state after the fault occurs, and calculate the proportion of the normal operation unit, the proportion of the low voltage ride-through unit and the proportion of the off-grid unit in the photovoltaic power station; According to the proportion of normal operating units in the photovoltaic power station, the proportion of low-voltage ride-through units and the proportion of off-grid units, 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 removed are calculated. 2. A method for calculating the power loss of a photovoltaic power station according to claim 1, wherein the calculation method for calculating the proportion of normal operating units, the proportion of low-voltage ride-through units and the proportion of off-grid units in a photovoltaic power station is as follows:

λ=1-θ-η Among them, θ is the proportion of normal operating units in the photovoltaic power station, η is the proportion of low-voltage ride-through units, λ is the proportion of off-grid units, _{id_mea} is the active current of the grid-connected _point of the photovoltaic power station in the steady state after the fault occurs, i _{q_mea} is the reactive current of the grid- _connected point of the photovoltaic power station in the steady state after the fault occurs, m is the total number of units of the photovoltaic power station, and i _d0 is the active current of the grid-connected point of the photovoltaic power station immediately before the fault occurs, and the parameter i _limit =1.2I _N , I _N is the rated current of the inverter, U _N is the rated voltage of the grid-connected point, U _d is the voltage of the grid-connected point under dq coordinates,

is the power factor angle of the unit in normal operation, and the reactive power reference value of the inverter

3. A method for calculating the power loss of a photovoltaic power station according to claim 1, characterized in that, according to the proportion of normal operating units in the photovoltaic power station, the proportion of low-voltage ride-through units and the proportion of off-grid units, the photovoltaic power generation during the fault period is calculated. The power loss of the power station and the power loss of the photovoltaic power station after the fault is removed, including: According to the proportion of normal operating units, the proportion of low voltage ride through units and the proportion of off-grid units in the photovoltaic power station, the capacity of normal operation units, low voltage ride through units and off-grid units during the fault period is calculated; According to the normal operating unit capacity, low voltage ride-through unit capacity and off-grid unit capacity during the fault period, 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 removed are calculated. 4. A method for calculating the power loss of a photovoltaic power station according to claim 3, wherein the capacity of the unit in normal operation during the fault period is the product of the total number of units in the photovoltaic power station, the unit capacity of the unit in the photovoltaic power station and the ratio of the units in normal operation in the photovoltaic power station ; The low-voltage ride-through unit capacity during the fault period is the product of the total number of photovoltaic power station units, the single-unit capacity of photovoltaic power station units and the proportion of low-voltage ride-through units in the photovoltaic power station; The off-grid unit capacity during the fault period is the product of the total number of photovoltaic power station units, the single-unit capacity of photovoltaic power station units and the proportion of off-grid units in the photovoltaic power station. 5. A method for calculating the power loss of a photovoltaic power station according to claim 3, wherein the power loss of the photovoltaic power station during the fault is calculated according to the capacity of the normal operation unit, the capacity of the low voltage ride-through unit and the capacity of the off-grid unit during the failure period and the amount of power loss of the photovoltaic power station after fault removal, including: According to the principle of reactive power priority for photovoltaic power station low voltage ride through, the power loss of photovoltaic power station during the fault period is the sum of the capacity of the normal operation unit during the fault period and the capacity of the low voltage ride through unit during the fault period; After the fault is removed, the low-voltage ride-through unit of the photovoltaic power station returns to normal operation, and the power loss of the photovoltaic power station is the capacity of the off-grid unit during the fault period. 6. A photovoltaic power station power loss calculation system, characterized in that it comprises: The proportion calculation module, in response to a fault, divides the photovoltaic power plant units into normal operation units, low voltage ride-through units and off-grid units. The active current of the network point and the reactive current of the grid-connected point of the photovoltaic power station in the steady state after the fault occurs, calculate the proportion of normal operation units, the proportion of low voltage ride-through units and the proportion of off-grid units in the photovoltaic power station; The loss amount 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 removed according to the proportion of the normal operation unit, the proportion of the low voltage ride-through unit and the proportion of the off-grid unit in the photovoltaic power station. 7. A photovoltaic power plant power loss calculation system according to claim 6, characterized in that, the ratio calculation module calculates the formula for calculating the proportion of normal operating units, the proportion of low-voltage ride-through units and the proportion of off-grid units in a photovoltaic power station:

λ=1-θ-η Among them, θ is the proportion of normal operating units in the photovoltaic power station, η is the proportion of low-voltage ride-through units, λ is the proportion of off-grid units, id _{_mea} is the active current of the grid-connected point of the photovoltaic power station in the steady state after the fault occurs, i _q _mea is the reactive current of the grid-connected point of the photovoltaic power station in the steady state after the fault occurs, m is the total number of units of the photovoltaic power station, and i _d0 is the active current of the grid-connected point of the photovoltaic power station _at the moment before the fault occurs, the parameter i _limit = 1.2IN, and I _N is Inverter rated current, U _N is the rated voltage of grid-connected point, U _d is the voltage of grid-connected point under dq coordinates,

is the power factor angle of the unit in normal operation, and the reactive power reference value of the inverter

8. A photovoltaic power plant power loss calculation system according to claim 6, characterized in that the loss calculation is based on the proportion of normal operating units in the photovoltaic power station, the proportion of low voltage ride through units and the proportion of off-grid units , to calculate the normal operation unit capacity, low voltage ride through unit capacity and off-grid unit capacity during the fault period, according to the normal operation unit capacity, low voltage ride through unit capacity and off-grid unit capacity during the fault period, calculate the power loss and fault removal of the photovoltaic power station during the fault period The amount of power loss in the post-PV power plant. 9. A computer-readable storage medium storing one or more programs, wherein the one or more programs comprise instructions which, when executed by a computing device, cause the computing device to perform the Any one of the methods described in 1 to 5. 10. A computing device, comprising: 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 include instructions for performing any of the methods according to claims 1-5.

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