Evaluation method suitable for photovoltaic equivalent inertia under additional frequency control

Abstract

The invention provides an evaluation method suitable for photovoltaic equivalent inertia under additional frequency control, and relates to the technical field of power system operation control, and the method comprises the steps: obtaining the operation angular frequency, rated capacity and rated inertia of each synchronous motor in an actual power system; determining the system inertia center frequency of the actual power system according to the operation angular frequency and the rated inertia of each synchronous motor; determining the equivalent inertia of the photovoltaic-containing power system under the disturbance of the photovoltaic-containing power system according to the disturbance quantity of the actual power system and the inertia center frequency of the system; determining the inertia of the synchronous motor of the system according to the rated capacity and the rated inertia of each synchronous motor; and evaluating the equivalent inertia of the photovoltaic equipment according to the equivalent inertia of the photovoltaic power system and the inertia of the synchronous motor of the system. According to the scheme, the equivalent inertia of the photovoltaic equipment in the power system can be evaluated without knowing additional frequency control parameters of the photovoltaic equipment, and the evaluation accuracy is relatively high.

Description

Technical Field

[0001] The present invention relates to the technical field of power system operation control, and in particular to an evaluation method for photovoltaic equivalent inertia under additional frequency control. Background Art

[0002] In modern power systems, with the increasing proportion of renewable energy generation, especially the large-scale grid connection of photovoltaic power generation, the inertia characteristics of the system have changed significantly. As one of the key indicators of power system stability, the size of inertia directly affects the frequency response capability of the system when facing power disturbances.

[0003] Inertia generally refers to the inertia level of traditional electrical equipment with rotating elements. For example, the rotational inertia of synchronous motors and asynchronous motors is referred to as inertia. Equipment without rotating elements in new power systems cannot provide rotational inertia for the system itself, but can provide equivalent inertia for the system through additional frequency control. Equivalent inertia is usually described by the inertia time constant, in seconds. Among them, in new power systems, the equivalent inertia of photovoltaic equipment is an important component of providing inertial support for the system through additional frequency control.

[0004] However, in actual new power systems, not all photovoltaic devices are equipped with additional frequency control, and the parameters of photovoltaic devices using additional frequency control are difficult to obtain, making it difficult to evaluate the equivalent inertia of all photovoltaic devices in the system. Summary of the invention

[0005] In view of this, in order to address the above shortcomings, it is necessary to propose an evaluation method for photovoltaic equivalent inertia under additional frequency control, so as to evaluate the equivalent inertia of photovoltaic equipment in the power system without knowing the additional frequency control parameters of photovoltaic equipment.

[0006] In a first aspect, the present invention provides a method for evaluating photovoltaic equivalent inertia under additional frequency control, the method comprising:

[0007] Obtain the operating angular frequency, rated capacity and rated inertia of each synchronous motor in the actual power system;

[0008] Determining the system inertia center frequency of the actual power system according to the operating angular frequency and rated inertia of each synchronous motor;

[0009] Determine the equivalent inertia of the photovoltaic power system under the disturbance of the photovoltaic power system according to the disturbance of the actual power system and the inertia center frequency of the system;

[0010] Determining the inertia of the synchronous motors of the system according to the rated capacity and rated inertia of each synchronous motor;

[0011] The equivalent inertia of the photovoltaic equipment is evaluated based on the equivalent inertia of the photovoltaic power system and the inertia of the synchronous motor of the system.

[0012] Preferably, determining the system inertia center frequency of the actual power system according to the operating angular frequency and rated inertia of each synchronous motor includes:

[0013] The system inertia center frequency is calculated using the following formula:

[0014]

[0015] Among them, ω coi Used to characterize the system's inertial center frequency, ω j Used to characterize the operating angular frequency of the jth synchronous motor, n G It is used to characterize the number of synchronous motors in actual power systems. j Used to characterize the rated inertia of the jth synchronous motor.

[0016] Preferably, the determining the equivalent inertia of the photovoltaic power system under the disturbance of the photovoltaic power system according to the disturbance of the actual power system and the inertia center frequency of the system includes:

[0017] Calculating the difference between the system inertia center frequency at two adjacent time points, and dividing the obtained difference by the time interval to obtain the rate of change of the system inertia center frequency;

[0018] Obtain the power change of power generation or load in the power system;

[0019] The ratio of the power change to the rate of change of the system inertia center frequency is calculated to obtain the equivalent inertia of the photovoltaic power system.

[0020] Preferably, determining the system synchronous motor inertia according to the rated capacity and rated inertia of each synchronous motor includes:

[0021] Obtaining the system rated capacity of the actual power system;

[0022] The inertia of the synchronous motor of the system is calculated using the following formula:

[0023]

[0024] Among them, H g Used to characterize the inertia of the synchronous motor in the system, S j Used to characterize the rated capacity of the jth synchronous motor, S B Used to characterize the rated capacity of the system.

[0025] Preferably, the step of evaluating the equivalent inertia of the photovoltaic device according to the equivalent inertia of the photovoltaic power system and the inertia of the synchronous motor of the system includes:

[0026] The difference between the equivalent inertia of the photovoltaic power system and the inertia of the synchronous motor of the system is calculated to obtain the equivalent inertia of the photovoltaic device.

[0027] Preferably, after determining the estimated equivalent inertia of the photovoltaic device, the method further comprises:

[0028] Acquire additional frequency control related parameters of the photovoltaic device in an experimental environment; wherein the additional frequency control related parameters include: an additional frequency control coefficient and a low-pass filter time constant;

[0029] Calculating the theoretical equivalent inertia of the photovoltaic device using the additional frequency control related parameters;

[0030] The relative error between the estimated equivalent inertia and the theoretical equivalent inertia is calculated to verify the accuracy of the photovoltaic equivalent inertia evaluation in the actual system.

[0031] Preferably, the calculating of the theoretical equivalent inertia of the photovoltaic device by using the additional frequency control related parameters includes:

[0032] Calculate the additional power generated by the additional frequency control of photovoltaic power generation in the frequency domain by using the additional frequency control coefficient and the low-pass filter time constant;

[0033] Utilizing the additional power, calculating the frequency domain theoretical equivalent inertia of the photovoltaic device under the additional frequency control in the frequency domain;

[0034] Performing Laplace transformation on the frequency domain theoretical equivalent inertia to obtain the time domain theoretical equivalent inertia of the photovoltaic device under additional frequency control;

[0035] The theoretical equivalent inertia of the photovoltaic device is determined according to the time domain theoretical equivalent inertia.

[0036] Preferably, the method of calculating the additional power generated by the additional frequency control of photovoltaic power generation in the frequency domain by using the additional frequency control coefficient and the low-pass filter time constant includes:

[0037] The additional power is calculated using the following formula:

[0038]

[0039] Among them, ΔP vir is the additional power provided by the photovoltaic device to the system at the instant of disturbance under additional frequency control. s is used to represent the integral operator of Laplace transform when the time domain is converted into the frequency domain. S B Used to characterize the system rated capacity, SPV Used to characterize the rated capacity of photovoltaic equipment, K d is the additional frequency control coefficient, T p is the low-pass filter time constant.

[0040] In a second aspect, the present invention provides a computer-readable storage medium having a computer program stored thereon, which, when executed in a computer, causes the computer to execute any of the methods described in the first aspect.

[0041] In a third aspect, the present invention provides a computing device, including a memory and a processor, wherein executable code is stored in the memory, and when the processor executes the executable code, any method described in the first aspect is implemented.

[0042] It can be seen from the above technical scheme that in the evaluation method for photovoltaic equivalent inertia under additional frequency control provided by the present invention, the operating angular frequency, rated capacity and rated inertia of each synchronous motor in the actual power system are first obtained, and then the system inertia center frequency of the power system is determined according to the operating angular frequency and rated inertia of each synchronous motor. In this way, the equivalent inertia of the photovoltaic power system under the disturbance of the photovoltaic power system can be determined by combining the system inertia center frequency and the disturbance of the power system; further, the inertia of the system synchronous motor can be determined according to the rated capacity and rated inertia of each synchronous motor, and then the equivalent inertia of the photovoltaic power system and the inertia of the system synchronous motor can be evaluated. It can be seen that when evaluating the equivalent inertia of the photovoltaic device, the equivalent inertia of the photovoltaic device can be evaluated without knowing the additional frequency control parameters of the photovoltaic device, which solves the problem that it is difficult to obtain the additional frequency control parameters of the photovoltaic device in the new power system, which leads to the difficulty in accurately evaluating the equivalent inertia of the photovoltaic device. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 A flowchart of a method for evaluating photovoltaic equivalent inertia under additional frequency control provided in an embodiment of the present invention.

[0044] Figure 2 Schematic diagram of the simplified SFR model under traditional power system disturbance.

[0045] Figure 3 Schematic diagram of the simplified SFR model under disturbance of the photovoltaic power system.

[0046] Figure 4 A two-stage photovoltaic power generation additional frequency control block diagram provided by an embodiment of the present invention.

[0047] Figure 5 A topology diagram of a photovoltaic four-machine two-zone system provided in an embodiment of the present invention.

[0048] Figure 6 This is the evaluation and verification diagram of the photovoltaic equivalent inertia results for Condition 1.

[0049] Figure 7 This is the evaluation and verification diagram of the photovoltaic equivalent inertia results for Condition 2. DETAILED DESCRIPTION

[0050] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0051] like Figure 1 As shown, the present invention provides an evaluation method for photovoltaic equivalent inertia under additional frequency control, and the evaluation method may include the following steps:

[0052] Step 101: Obtain the operating angular frequency, rated capacity and rated inertia of each synchronous motor in the actual power system;

[0053] Step 102: determining the system inertia center frequency of the actual power system according to the operating angular frequency and rated inertia of each synchronous motor;

[0054] Step 103: determining the equivalent inertia of the photovoltaic power system under the photovoltaic power system disturbance according to the actual power system disturbance and the system inertia center frequency;

[0055] Step 104: Determine the inertia of the system synchronous motor according to the rated capacity and rated inertia of each synchronous motor;

[0056] Step 105: Evaluate the equivalent inertia of the photovoltaic equipment according to the equivalent inertia of the photovoltaic power system and the inertia of the system synchronous motor.

[0057] In this embodiment, when evaluating the equivalent inertia of the photovoltaic device, the equivalent inertia of the photovoltaic device can be evaluated without knowing the additional frequency control parameters of the photovoltaic device, which solves the problem that it is difficult to obtain the additional frequency control parameters of the photovoltaic device in the new power system, and thus it is difficult to accurately evaluate the equivalent inertia of the photovoltaic device. Moreover, this solution can comprehensively evaluate the equivalent inertia of all photovoltaic devices in the entire power system. Compared with existing research that mainly focuses on the inertia evaluation of a single photovoltaic device, it can more accurately evaluate the actual inertia contribution of photovoltaic devices in the new power system.

[0058] For step 101, the operating angular frequency, rated capacity and rated inertia of each synchronous motor in the actual power system are obtained;

[0059] In this step, in the actual power system, the operating angular frequency, rated capacity and rated inertia of each synchronous motor can be obtained by recording and monitoring the operating parameters of the synchronous motor, for example, they can be obtained from the power system.

[0060] For step 102, the system inertia center frequency of the actual power system is determined according to the operating angular frequency and rated inertia of each synchronous motor;

[0061] like Figure 2 As shown in the figure, in order to quantitatively evaluate the actual inertia of the power system containing photovoltaics, the system frequency response SFR model is considered. The SFR model is a model that describes the average frequency response of the power system after a disturbance. A single synchronous motor model is used instead of the entire power system to study the frequency. In traditional power systems, the SFR model usually includes models such as the speed regulator, prime mover, and load, which can simulate the dynamic frequency changes of the system after power imbalance. Among them, ΔP d is the change in power generation or load in the power grid, ΔP m is the change in mechanical power of the synchronous motor, ΔP a is the power difference allocated to the synchronous motor, D is the equivalent damping coefficient of the generator, R is the speed regulator adjustment coefficient, T R is the reheating time constant of the synchronous motor, F H K is the work ratio of the high-pressure cylinder of the synchronous motor. m is a coefficient related to the generator power factor and reserve capacity.

[0062] Thus, when determining the system inertia center frequency in the SFR model in step 102, the system inertia center frequency can be calculated using the following calculation formula:

[0063]

[0064] Among them, ω coi Used to characterize the system's inertial center frequency, ω j Used to characterize the operating angular frequency of the jth synchronous motor, n G It is used to characterize the number of synchronous motors in actual power systems. j Used to characterize the rated inertia of the jth synchronous motor.

[0065] For step 103, according to the disturbance of the actual power system and the system inertia center frequency, the equivalent inertia of the photovoltaic power system under the disturbance of the photovoltaic power system is determined;

[0066] In this step, after adopting the additional frequency control, the frequency model of the photovoltaic power system is analyzed, the feedback loop of the SFR model of the photovoltaic power system is added, and the simplified SFR model of the photovoltaic power system under disturbance is established, such as Figure 3As shown. According to the SFR model definition, the equivalent inertia of the photovoltaic power system can be defined by the ratio of the disturbance size to the rate of change of the inertia center frequency. Specifically, in step 103, when determining the equivalent inertia of the photovoltaic power system under the disturbance of the photovoltaic power system according to the actual disturbance of the power system and the system inertia center frequency, the difference between the system inertia center frequency at two adjacent time points can be first calculated, and then the rate of change of the system inertia center frequency can be obtained by dividing their difference by the time interval, and then the power change of the power generation or load in the power system can be obtained; further, the ratio of the power change to the rate of change of the system inertia center frequency is calculated to obtain the equivalent inertia of the photovoltaic power system.

[0067] For example, the equivalent inertia of a photovoltaic power system can be calculated using the following formula:

[0068]

[0069] In the formula, H nsys is the equivalent inertia of the photovoltaic power system, ΔP d It is the power change of power generation or load in the power grid.

[0070] In step 104, the inertia of the synchronous motor of the system is determined according to the rated capacity and rated inertia of each synchronous motor;

[0071] In this step, the rated capacity and rated inertia of all synchronous motors in the collection system, as well as the system rated capacity S B , assuming that the rated capacity and rated inertia of the jth synchronous motor are S j and H j , the system synchronous motor inertia H can be calculated based on the following formula g :

[0072]

[0073] For step 105 , the equivalent inertia of the photovoltaic equipment is evaluated according to the equivalent inertia of the photovoltaic power system and the inertia of the synchronous motor of the system.

[0074] Combination Figure 3 From the model, it can be seen that when the equivalent damping coefficient D of the synchronous motor is ignored, the inertia of the synchronous motor of the system can be expressed as follows:

[0075]

[0076] Among them, ΔP m is the change in mechanical power of the synchronous motor, ΔP a is the power difference allocated to the synchronous motor, ΔP virIt is the power provided by the photovoltaic device to the system at the moment of disturbance under additional frequency control. Considering that the mechanical power of the synchronous motor cannot change suddenly at the moment of disturbance, ΔP m is approximately 0. Therefore, based on H nsys =H g +H pv The equivalent inertia H of the photovoltaic equipment can be evaluated pv That is, the difference between the equivalent inertia of the photovoltaic power system and the inertia of the system synchronous motor is calculated to obtain the equivalent inertia H of the photovoltaic equipment. pv .

[0077] Furthermore, in order to ensure the accuracy of the estimated equivalent inertia, after determining the estimated equivalent inertia of the photovoltaic equipment, an experimental environment can be further constructed to verify the accuracy of the estimated equivalent inertia through the theoretical equivalent inertia calculated in the experimental environment. Specifically, after determining the estimated equivalent inertia, further verification can be performed through the following steps:

[0078] Step 106: obtaining additional frequency control related parameters of the photovoltaic device in an experimental environment; wherein the additional frequency control related parameters include: an additional frequency control coefficient and a low-pass filter time constant;

[0079] Step 107: Calculate the theoretical equivalent inertia of the photovoltaic device by using the additional frequency control related parameters;

[0080] Step 108: Calculate the relative error between the estimated equivalent inertia and the theoretical equivalent inertia to verify the accuracy of the photovoltaic equivalent inertia estimation in the actual system.

[0081] For step 106, additional frequency control related parameters of the photovoltaic device are obtained in an experimental environment;

[0082] In this step, consider building an experimental environment and obtaining the additional frequency control coefficient K of the photovoltaic device d and low-pass filter time constant T p Among them, the additional frequency control coefficient affects the response speed of the photovoltaic device to the frequency change, and the low-pass filter time constant is used to filter out the high-frequency noise in the frequency signal to ensure the stability of the control. These two parameters do not need to be known in the inertia evaluation of the actual power system.

[0083] For step 107, the theoretical equivalent inertia of the photovoltaic device is calculated using the additional frequency control related parameters;

[0084] This step can be implemented as follows when calculating the theoretical equivalent inertia of the photovoltaic device using the additional frequency control related parameters:

[0085] The additional power generated by the additional frequency control of photovoltaic power generation in the frequency domain is calculated using the additional frequency control coefficient and the low-pass filter time constant;

[0086] Using the extra power, the frequency domain theoretical equivalent inertia of the photovoltaic device under additional frequency control is calculated in the frequency domain;

[0087] The frequency domain theoretical equivalent inertia is Laplace transformed to obtain the time domain theoretical equivalent inertia of the photovoltaic device under additional frequency control.

[0088] According to the theoretical equivalent inertia in the time domain, the theoretical equivalent inertia of the photovoltaic equipment is determined.

[0089] In this embodiment, first, a photovoltaic device control block diagram can be established based on the control parameters measured in the experimental environment, and the additional power generated when the theoretical state is disturbed can be calculated. Specifically, the rated capacity S of the photovoltaic device PV and system rated capacity S B , derive the additional power of the photovoltaic equivalent under the additional frequency control. In order to enable the photovoltaic equipment to have the ability of frequency response without configuring additional energy storage, the load reduction control is introduced as the energy source in the maximum frequency tracking control (MPPT) control of the boost circuit. At the same time, the additional frequency control is adopted, and the frequency of the photovoltaic grid-connected point is used as feedback. The active power output reference value of the photovoltaic is changed through the additional frequency control coefficient, and then the photovoltaic output is changed instantly after the disturbance. After conversion to the rated capacity, the duty cycle d is obtained through PI control to control the output of the boost circuit, and finally the inverter is controlled in the form of DC capacitor voltage to change the photovoltaic active output. The whole process is as follows Figure 4 shown.

[0090] In this process, although there is a certain delay in the boost circuit and the inverter circuit, the response speed of the power electronic devices is much faster than the inertia response and electromagnetic transient response process, so the dynamics of the power electronic devices can be ignored, and the photovoltaic active output is approximately equal to the power reference value. In summary, when the photovoltaic load reduction rate is constant, the additional power generated by photovoltaic power generation in the frequency domain under additional frequency control can be calculated by the following calculation formula:

[0091]

[0092] Among them, ΔP vir is the additional power provided by the photovoltaic device to the system at the instant of disturbance under additional frequency control. s is used to represent the integral operator of Laplace transform when the time domain is converted into the frequency domain. S B Used to characterize the system rated capacity, S PV Used to characterize the rated capacity of photovoltaic equipment, K d is the additional frequency control coefficient, T p is the low-pass filter time constant.

[0093] Furthermore, according to the definition of photovoltaic theoretical inertia Combined with the above additional power, the frequency domain theoretical equivalent inertia of photovoltaic equipment in the frequency domain can be obtained as follows:

[0094]

[0095] Furthermore, by performing Laplace transform on the above frequency domain theoretical equivalent inertia, the time domain equivalent inertia of the photovoltaic device in the time domain can be obtained as follows:

[0096]

[0097] From the above time domain equivalent inertia, it can be seen that when the low-pass filter time constant is small, It will reach a stable value in a very short time, so the theoretical equivalent inertia of the photovoltaic device can be approximated as follows:

[0098]

[0099] For step 108, the relative error between the estimated equivalent inertia and the theoretical equivalent inertia is calculated to verify the accuracy of the photovoltaic equivalent inertia estimation in the actual system.

[0100] In this step, the purpose is to compare the theoretical inertia of photovoltaic equipment under the experimental environment with the actual system inertia evaluation results. For example, the relative error between the evaluated equivalent inertia and the theoretical equivalent inertia can be calculated to confirm the effectiveness and accuracy of the photovoltaic equivalent inertia evaluation in the actual system. Specifically, the relative error between the evaluated equivalent inertia and the theoretical equivalent inertia can be calculated using the following error formula:

[0101]

[0102] Among them, H pv and are the estimated equivalent inertia and theoretical equivalent inertia of the photovoltaic equipment, respectively. In this way, the accuracy of the estimated equivalent inertia can be verified according to the size of the relative error. Specifically, by obtaining the relative error, it can be further determined whether it is necessary to apply a correction to the photovoltaic additional frequency control parameters.

[0103] The effects of the present invention are further described below in conjunction with specific simulation experiments.

[0104] A four-machine two-zone system was built in Matlab / Simulink. The frequency of the model was set to 50 Hz and all loads were set to constant power load models. The rated capacity of all synchronous motors was 900 MVA, and the inertia time constants of synchronous motors G1 and G2 were 6.5 s, and those of G3 and G4 were 6.175 s.

[0105] In order to verify that the present invention can simultaneously evaluate the equivalent inertia of all photovoltaic devices in a region, different numbers of photovoltaic devices are connected in the region, such as Figure 5 As shown, the setting conditions are as follows:

[0106] Condition 1: Only the photovoltaic unit PV1 with a rated capacity of 250MW is connected at the node 8 in area 2, and additional frequency control is adopted with a low-pass filter time constant T p = 0.001s. Set node 9 to have an impact load disturbance at 15s, the disturbance size is 176MW, and the frequency measurement window is 200ms.

[0107] Condition 2: Connect the PV units PV1 and PV2 with a rated capacity of 250MW at nodes 8 and 9 in area 2 at the same time, use additional frequency control and take the low-pass filter time constant T p =0.001s. Similarly, node 9 is set to have an impact load disturbance at 15s, the disturbance size is 176MW, and the frequency measurement window is 200ms.

[0108] For the connected PV power station, different PV additional frequency control coefficients are set to simulate the inertia evaluation under different working conditions. The PV equivalent inertia after disturbance is calculated as shown in Table 1 below.

[0109] Table 1 Theoretical equivalent inertia of photovoltaic under different additional frequency control

[0110] Photovoltaic additional frequency control coefficient <![CDATA[K d =10]]> <![CDATA[K d =15]]> <![CDATA[K d =20]]> Working condition 1 Photovoltaic theoretical inertia time constant / s 1.389 2.083 2.778 Working condition 2 Photovoltaic theoretical inertia time constant / s 2.778 4.167 5.555

[0111] First, according to the calculation formula of the system synchronous motor inertia, the equivalent aggregate inertia time constant of the synchronous motor is calculated as follows:

[0112]

[0113] Then, when the photovoltaic system adopts additional frequency control, the overall equivalent inertia of the system is evaluated under different additional frequency control coefficients. The evaluation results of working conditions 1 and 2 are shown in Table 2 below. The inertia time constants in the table are all based on the system benchmark capacity.

[0114] Table 2 Equivalent inertia evaluation results of four-machine two-zone system

[0115]

[0116] The photovoltaic equivalent inertia is further evaluated and compared with the theoretical value, such as Figure 6-7 When the photovoltaic system adopts additional frequency control, the present invention can effectively calculate the theoretical inertia provided by the photovoltaic equipment, and accurately evaluate the photovoltaic equivalent inertia using the proposed evaluation method in the actual system, and the evaluation error between the theoretical value and the measured value is within 10%.

[0117] In addition, the present invention also provides a computer-readable storage medium on which a computer program is stored. When the computer program is executed in a computer, the computer is caused to execute the method of any of the above embodiments.

[0118] The present invention further provides a computing device, including a memory and a processor, wherein executable code is stored in the memory, and when the processor executes the executable code, the method of any of the above embodiments is implemented.

[0119] The device embodiment and method embodiment of the present invention are based on the same inventive concept. For detailed description, please refer to the method embodiment, which will not be described in detail here.

[0120] The modules or units in the device of the embodiment of the present invention can be combined, divided and deleted according to actual needs. The above disclosure is only the preferred embodiment of the present invention, and of course it cannot be used to limit the scope of the rights of the present invention. Those skilled in the art can understand that all or part of the processes of the above embodiment are implemented, and the equivalent changes made according to the claims of the present invention still fall within the scope of the invention.

Claims

1. An evaluation method for photovoltaic equivalent inertia under additional frequency control, It is characterized in that The assessment method includes: Obtain the operating angular frequency, rated capacity and rated inertia of each synchronous motor in the actual power system; Determining the system inertia center frequency of the actual power system according to the operating angular frequency and rated inertia of each synchronous motor; Determine the equivalent inertia of the photovoltaic power system under the disturbance of the photovoltaic power system according to the disturbance of the actual power system and the inertia center frequency of the system; Determining the inertia of the synchronous motors of the system according to the rated capacity and rated inertia of each synchronous motor; The equivalent inertia of the photovoltaic equipment is evaluated based on the equivalent inertia of the photovoltaic power system and the inertia of the synchronous motor of the system.

2. The method for evaluating photovoltaic equivalent inertia under additional frequency control according to claim 1, It is characterized in that Determining the system inertia center frequency of the actual power system according to the operating angular frequency and rated inertia of each synchronous motor includes: The inertia center frequency of the system is calculated using the following formula: Among them, ω coi Used to characterize the system's inertial center frequency, ω j Used to characterize the operating angular frequency of the jth synchronous motor, n G It is used to characterize the number of synchronous motors in actual power systems. j Used to characterize the rated inertia of the jth synchronous motor.

3. The method for evaluating photovoltaic equivalent inertia under additional frequency control according to claim 2, It is characterized in that The determining of the equivalent inertia of the photovoltaic power system under the disturbance of the photovoltaic power system according to the disturbance of the actual power system and the inertia center frequency of the system comprises: Calculating the difference between the inertia center frequency of the system at two adjacent time points, and dividing the obtained difference by the time interval to obtain the rate of change of the inertia center frequency of the system; Obtain the power change of power generation or load in the power system; The ratio of the power change to the rate of change of the system inertia center frequency is calculated to obtain the equivalent inertia of the photovoltaic power system.

4. The method for evaluating photovoltaic equivalent inertia under additional frequency control according to claim 3, It is characterized in that Determining the system synchronous motor inertia in the actual power system according to the rated capacity and rated inertia of each synchronous motor includes: Obtaining the system rated capacity of the actual power system; The inertia of the synchronous motor of the system is calculated using the following formula: Among them, H g Used to characterize the inertia of the synchronous motor in the system, S j Used to characterize the rated capacity of the jth synchronous motor, S B Used to characterize the rated capacity of the system.

5. The method for evaluating photovoltaic equivalent inertia under additional frequency control according to claim 4, It is characterized in that The step of evaluating the equivalent inertia of the photovoltaic device according to the equivalent inertia of the photovoltaic power system and the inertia of the synchronous motor of the system includes: The difference between the equivalent inertia of the photovoltaic power system and the inertia of the synchronous motor of the system is calculated to obtain the equivalent inertia of the photovoltaic device.

6. The method for evaluating photovoltaic equivalent inertia under additional frequency control according to claim 1, It is characterized in that After determining the estimated equivalent inertia of the photovoltaic equipment, it further includes: Acquire additional frequency control related parameters of the photovoltaic device in an experimental environment; wherein the additional frequency control related parameters include: an additional frequency control coefficient and a low-pass filter time constant; Calculating the theoretical equivalent inertia of the photovoltaic device using the additional frequency control related parameters; The relative error between the estimated equivalent inertia and the theoretical equivalent inertia is calculated to verify the accuracy of the photovoltaic equivalent inertia evaluation in the actual system.

7. The method for evaluating photovoltaic equivalent inertia under additional frequency control according to claim 6, It is characterized in that The method of calculating the theoretical equivalent inertia of the photovoltaic device by using the additional frequency control related parameters includes: Calculate the additional power generated by the additional frequency control of photovoltaic power generation in the frequency domain by using the additional frequency control coefficient and the low-pass filter time constant; Utilizing the additional power, calculating the frequency domain theoretical equivalent inertia of the photovoltaic device under the additional frequency control in the frequency domain; Performing Laplace transformation on the frequency domain theoretical equivalent inertia to obtain the time domain theoretical equivalent inertia of the photovoltaic device under additional frequency control; The theoretical equivalent inertia of the photovoltaic device is determined according to the time domain theoretical equivalent inertia.

8. The method for evaluating photovoltaic equivalent inertia under additional frequency control according to claim 7, It is characterized in that The method of calculating the additional power generated by the additional frequency control of photovoltaic power generation in the frequency domain by using the additional frequency control coefficient and the low-pass filter time constant includes: The additional power is calculated using the following formula: Where ΔP vir is the additional power provided by the photovoltaic device to the system at the instant of disturbance under additional frequency control. s is used to represent the integral operator of Laplace transform when the time domain is converted into the frequency domain. S B Used to characterize the system rated capacity, S PV Used to characterize the rated capacity of photovoltaic equipment, K d is the additional frequency control coefficient, T p is the low-pass filter time constant.

9. A computer-readable storage medium having a computer program stored thereon, which, when executed in a computer, causes the computer to execute the method according to any one of claims 1 to 8.

10. A computing device comprising a memory and a processor, wherein the memory stores executable codes, and when the processor executes the executable codes, the method according to any one of claims 1 to 8 is implemented.

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