Photovoltaic inverter intelligent frequency modulation method, system and storage medium

Abstract

The present invention discloses a photovoltaic inverter intelligent frequency modulation method, system and storage medium, and relates to the technical field of power system. The photovoltaic inverter intelligent frequency modulation method comprises the following steps: voltage monitoring compliance assessment; frequency monitoring compliance assessment; power monitoring compliance assessment. The present invention evaluates the voltage monitoring circuit to obtain the voltage monitoring compliance assessment index and judges whether to perform voltage frequency modulation, then evaluates the frequency monitoring circuit to obtain the frequency monitoring compliance assessment index and judges whether to perform frequency frequency modulation, and finally evaluates the power detection circuit to obtain the power monitoring compliance assessment index and judges whether to perform power frequency modulation, thereby achieving the effect of improving the response accuracy in the process of intelligent frequency modulation of the photovoltaic inverter, and solving the problem of insufficient response in the process of intelligent frequency modulation of the photovoltaic inverter in the prior art.

Description

Technical Field

[0001] The present invention relates to the technical field of power systems, and in particular to a photovoltaic inverter intelligent frequency modulation method, system and storage medium. Background Art

[0002] Photovoltaic power generation system is a technical system that uses solar energy to convert into electrical energy. It is mainly composed of photovoltaic panels, photovoltaic inverters, and related control systems and grid connection equipment. Photovoltaic panels are responsible for converting solar energy into DC power, while photovoltaic inverters are responsible for converting DC power into AC power for use in homes, businesses or power grids. Traditional photovoltaic inverters have many challenges in frequency regulation, such as low frequency regulation accuracy, slow response speed, and high energy consumption during frequency regulation. These problems limit the overall performance and efficiency of photovoltaic power generation systems. In order to solve the problems of traditional photovoltaic inverters in frequency regulation, intelligent frequency regulation technology came into being. Intelligent frequency regulation technology is a frequency regulation method based on advanced control algorithms and real-time data acquisition and analysis. It can realize the precise regulation and control of the output power of photovoltaic power generation systems by photovoltaic inverters.

[0003] Existing methods are mainly based on historical data of photovoltaic cell arrays to train artificial neural network models to achieve intelligent prediction and control of photovoltaic cell arrays, thereby adjusting the output frequency of photovoltaic inverters.

[0004] For example, the invention patent with announcement number: CN110783953B announces a fast frequency regulation response communication method for a string inverter photovoltaic power station, including: after the frequency regulation system sends a power setting instruction to the secondary power control device, the secondary power control device calculates the active power target value of all inverters, broadcasts and sends instructions containing the active power target value of all inverters, and after the inverter receives the instruction, it does not need to reply to confirm, but parses out the active power setting value corresponding to its own communication address and executes it. The transformer measurement and control device is connected to the secondary power control device via RS485, and the secondary power control device directly collects the active power on the transformer side and uploads it to the frequency regulation system. The frequency regulation system performs closed-loop regulation again based on this feedback value.

[0005] For example, the invention patent application with publication number: CN115864428A discloses a distributed frequency modulation method and system suitable for a grid-connected photovoltaic power station inverter, including: for the inverter of the grid-connected photovoltaic power station, a battery pack of preset capacity is connected to the DC side of the inverter; according to the charge state of the battery pack, the charging and discharging rules of the battery pack are determined; according to the charging and discharging rules, the modulation coefficient of the inverter is determined; according to the modulation coefficient, the frequency modulation rule of the inverter is determined, and the inverter of the grid-connected photovoltaic power station is distributedly modulated according to the frequency modulation rule.

[0006] However, in the process of implementing the technical solution of the invention in the embodiments of the present application, the present application found that the above technology has at least the following technical problems:

[0007] In the prior art, when the grid state is abnormal, the inverter may be impacted by abnormal signals. These abnormal signals may cause the circuit parameters inside the inverter to change, thereby affecting the stability of the inverter output, causing the inverter to be unable to adjust quickly and accurately, resulting in insufficient response during the intelligent frequency regulation process of the photovoltaic inverter. Summary of the invention

[0008] The embodiments of the present application solve the problem of insufficient response in the intelligent frequency modulation process of photovoltaic inverters in the prior art by providing a photovoltaic inverter intelligent frequency modulation method, system and storage medium, and improve the response accuracy in the intelligent frequency modulation process of photovoltaic inverters.

[0009] The embodiment of the present application provides a photovoltaic inverter intelligent frequency modulation method, comprising the following steps: S1, evaluating a voltage monitoring circuit to obtain voltage monitoring related data, obtaining a voltage monitoring compliance evaluation index based on the voltage monitoring related data, and judging whether to perform voltage frequency modulation according to the voltage monitoring compliance evaluation index, wherein the voltage frequency modulation is used to improve the stability of the output voltage of the power grid and the photovoltaic inverter, and the voltage monitoring compliance evaluation index is used to evaluate the compliance of voltage changes; S2, evaluating a frequency monitoring circuit to obtain frequency monitoring related data, obtaining a frequency monitoring compliance evaluation index based on the frequency monitoring related data, and judging whether to perform frequency frequency modulation according to the frequency monitoring compliance evaluation index, wherein the frequency frequency modulation is used to improve the stability of the output frequency of the power grid and the photovoltaic inverter, and the frequency monitoring compliance evaluation index is used to evaluate the compliance of frequency changes; S3, evaluating a power detection circuit to obtain power monitoring related data, obtaining a power monitoring compliance evaluation index based on the power monitoring related data, and judging whether to perform power frequency modulation according to the power monitoring compliance evaluation index, wherein the power frequency modulation is used to improve the stability of the output power of the power grid and the photovoltaic inverter, and the power monitoring compliance evaluation index is used to evaluate the compliance of the output power changes.

[0010] Furthermore, the voltage monitoring related data include grid voltage change, photocurrent, open circuit voltage, battery internal resistance, maximum load current and transmission line impedance; the frequency monitoring related data include the minimum current fluctuation period and the maximum frequency deviation; the power monitoring related data include inverter output voltage, inverter output current, phase angle and on-resistance; the grid voltage change represents the maximum value of the grid voltage change within a preset time period; the photocurrent represents the average value of the current generated by the photovoltaic cell within a preset time period; the open circuit voltage represents the average value of the open circuit voltage of the photovoltaic cell within a preset time period; the inverter output voltage represents the output voltage of the photovoltaic inverter at the end of the first preset time period; the inverter output current represents the output current of the photovoltaic inverter at the end of the first preset time period; the phase angle represents the phase angle between the output voltage and the output current of the photovoltaic inverter within the first preset time period; the on-resistance represents the on-resistance of the photovoltaic inverter within the first preset time period; the first preset time period represents the preset time period corresponding to voltage frequency modulation and frequency frequency modulation.

[0011] Furthermore, the specific process of obtaining the voltage monitoring compliance evaluation index based on the voltage monitoring related data is as follows: the grid voltage change compliance value is obtained by performing a ratio operation on the sum of the grid voltage change amount and the preset voltage change maximum threshold obtained from the database and twice the preset voltage change maximum threshold; the photovoltaic cell output voltage compliance value is obtained by performing a ratio operation on the sum of the initial photovoltaic cell output voltage and the preset photovoltaic cell output voltage average threshold obtained from the database and twice the preset photovoltaic cell output voltage average threshold, and the initial photovoltaic cell output voltage is obtained by multiplying the open circuit voltage by the product of the photocurrent and the battery internal resistance. Perform difference calculation to obtain; perform ratio calculation on the sum of the initial transmission line voltage drop and the preset transmission line voltage drop maximum threshold obtained from the database and twice the preset transmission line voltage drop maximum threshold to obtain the transmission line voltage drop compliance value; the transmission line voltage drop compliance value is used to reflect the compliance of the transmission line voltage drop within a preset time period; combine the obtained grid voltage change compliance value, photovoltaic cell output voltage compliance value and transmission line voltage drop compliance value, as well as the first preset inverter weight, the second preset inverter weight and the third preset inverter weight obtained from the database to obtain the voltage monitoring compliance evaluation index.

[0012] Furthermore, the specific method for judging whether to perform voltage frequency modulation according to the voltage monitoring compliance evaluation index is as follows: judging whether the voltage monitoring compliance evaluation index is within the preset voltage monitoring compliance range obtained from the database, when the voltage monitoring compliance evaluation index is within the preset voltage monitoring compliance range, not performing voltage frequency modulation; when the voltage monitoring compliance evaluation index is not within the preset voltage monitoring compliance range, performing voltage frequency modulation; the specific steps of the voltage frequency modulation are as follows: the first step is to perform photovoltaic cell maximum power point tracking, when the monitored voltage monitoring compliance evaluation index is within the preset voltage monitoring compliance range, stop performing voltage frequency modulation, otherwise execute the second step; the second step is to perform voltage detection, when the monitored voltage monitoring compliance evaluation index is within the preset voltage monitoring compliance range, stop performing voltage frequency modulation, otherwise triggering island protection.

[0013] Further, the frequency monitoring compliance evaluation index is obtained by analyzing the grid frequency compliance value, the grid angular frequency compliance value, and the grid frequency offset compliance value: the grid frequency compliance value is used to reflect the compliance degree of the grid frequency within the preset time period, and the grid frequency compliance value is represented by the result of a ratio operation between the sum of the initial grid frequency and the preset grid frequency maximum threshold obtained from the database and 2 times the preset grid frequency maximum threshold, and the initial grid frequency is represented by the inverse of the minimum period of current fluctuation; the grid angular frequency compliance value is used to reflect the compliance degree of the grid angular frequency within the preset time period, and the grid angular frequency compliance value is represented by the result of a ratio operation between the sum of the initial grid angular frequency and the preset grid angular frequency maximum threshold obtained from the database and 2 times the preset grid angular frequency maximum threshold, and the initial grid angular frequency is obtained by processing the initial grid frequency; the grid frequency offset compliance value is used to reflect the compliance degree of the grid frequency offset within the preset time period, and the grid frequency offset compliance value is represented by the result of a ratio operation between 2 times the preset grid frequency offset maximum threshold obtained from the database and the frequency offset maximum value and the sum of the preset grid frequency offset maximum threshold.

[0014] Furthermore, the specific process of judging whether to perform frequency modulation according to the frequency monitoring compliance evaluation index is as follows: judging whether the frequency monitoring compliance evaluation index is within the preset frequency monitoring compliance range obtained from the database, when the frequency monitoring compliance evaluation index is within the preset frequency monitoring compliance range, not performing frequency modulation; when the frequency monitoring compliance evaluation index is not within the preset frequency monitoring compliance range, performing frequency modulation; the specific process of the frequency modulation is as follows: step one, performing frequency control, when the monitored frequency monitoring compliance evaluation index is within the preset frequency monitoring compliance range, stopping frequency modulation, otherwise executing step two; step two, performing frequency detection, when the monitored frequency monitoring compliance evaluation index is within the preset frequency monitoring compliance range, stopping frequency modulation, otherwise triggering island protection.

[0015] Further, the specific process of obtaining the power monitoring compliance evaluation index based on the power monitoring related data is as follows: obtaining the inverter power compliance value and the inverter power loss compliance value; obtaining the power monitoring compliance evaluation index through the inverter power compliance value and the inverter power loss compliance value and the voltage monitoring compliance evaluation index after voltage frequency modulation and the frequency monitoring compliance evaluation index after frequency frequency modulation; the method for obtaining the power monitoring compliance evaluation index is:

[0016] ;

[0017] In the formula, Indicates that the power monitoring meets the evaluation index in the yth first preset time period, , y represents the number of the first preset time period, c represents the total number of the first preset time period, represents the inverter power compliance value in the yth first preset time period, represents the inverter power loss compliance value in the yth first preset time period, It indicates that the voltage monitoring after voltage frequency modulation in the yth first preset time period meets the evaluation index, It represents the frequency monitoring compliance evaluation index of frequency modulation during the yth first preset time period, and e represents a natural constant.

[0018] The inverter power compliance value is used to reflect the compliance level of the inverter power within a preset time period; the inverter power loss compliance value is used to reflect the compliance level of the inverter power loss within a preset time period.

[0019] Furthermore, the specific process of determining whether to perform power frequency modulation according to the power monitoring compliance evaluation index is as follows: when the power monitoring compliance evaluation index is within the preset power monitoring compliance range, power frequency modulation is not performed; when the power monitoring compliance evaluation index is not within the preset power monitoring compliance range, power frequency modulation is performed; the specific process of the power frequency modulation is as follows: V1, performing optical fiber communication, when the monitored power monitoring compliance evaluation index is within the preset power monitoring compliance range, power frequency modulation is stopped, otherwise V2 is executed; V2, performing power detection, when the monitored power monitoring compliance evaluation index is within the preset power monitoring compliance range, power frequency modulation is stopped, otherwise island protection is triggered.

[0020] The embodiment of the present application provides a photovoltaic inverter intelligent frequency regulation system, including a voltage monitoring compliance assessment module, a frequency monitoring compliance assessment module and a power monitoring compliance assessment module: wherein the voltage monitoring compliance assessment module is used to evaluate the voltage monitoring circuit to obtain voltage monitoring related data, obtain the voltage monitoring compliance assessment index based on the voltage monitoring related data, and judge whether to perform voltage frequency regulation according to the voltage monitoring compliance assessment index, wherein the voltage frequency regulation is used to improve the stability of the output voltage of the power grid and the photovoltaic inverter, and the voltage monitoring compliance assessment index is used to evaluate the compliance of the voltage change; the frequency monitoring compliance assessment module is used to evaluate the frequency monitoring circuit to obtain frequency monitoring related data, based on the voltage monitoring related data The frequency monitoring related data obtains the frequency monitoring compliance evaluation index, and determines whether to perform frequency modulation according to the frequency monitoring compliance evaluation index. The frequency modulation is used to improve the stability of the output frequency of the power grid and the photovoltaic inverter, and the frequency monitoring compliance evaluation index is used to evaluate the compliance of frequency changes; the power monitoring compliance evaluation module is used to evaluate the power detection circuit to obtain power monitoring related data, obtain the power monitoring compliance evaluation index based on the power monitoring related data, and determine whether to perform power modulation according to the power monitoring compliance evaluation index. The power modulation is used to improve the stability of the output power of the power grid and the photovoltaic inverter, and the power monitoring compliance evaluation index is used to evaluate the compliance of the output power change.

[0021] An embodiment of the present application provides a computer-readable storage medium for storing a program, wherein the program, when executed by a processor, implements the photovoltaic inverter intelligent frequency regulation method.

[0022] One or more technical solutions provided in the embodiments of the present application have at least the following technical effects or advantages:

[0023] 1. By evaluating the voltage monitoring circuit to obtain the voltage monitoring compliance evaluation index and determine whether to perform voltage frequency modulation, then evaluating the frequency monitoring circuit to obtain the frequency monitoring compliance evaluation index and determine whether to perform frequency frequency modulation, and finally evaluating the power detection circuit to obtain the power monitoring compliance evaluation index and determine whether to perform power frequency modulation, the reliability of the intelligent frequency modulation of the photovoltaic inverter is improved, and then the response accuracy of the photovoltaic inverter in the intelligent frequency modulation process is improved, which effectively solves the problem of insufficient response in the intelligent frequency modulation process of the photovoltaic inverter in the prior art.

[0024] 2. By combining the obtained grid voltage change compliance value, photovoltaic cell output voltage compliance value and transmission line voltage drop compliance value as well as the first preset inverter weight, the second preset inverter weight and the third preset inverter weight to obtain the voltage monitoring compliance evaluation index, the accurate quantification of the compliance of the voltage change evaluation is achieved, thereby achieving the improvement of the accuracy of the compliance of the voltage change evaluation.

[0025] 3. By judging whether the voltage monitoring compliance assessment index is within the preset voltage monitoring compliance range, then judging whether the frequency monitoring compliance assessment index is within the preset frequency monitoring compliance range, and finally judging whether the power monitoring compliance assessment index is within the preset power monitoring compliance range, the refinement of the photovoltaic inverter frequency modulation is achieved, thereby achieving the improvement of the photovoltaic inverter frequency modulation accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 A flow chart of a photovoltaic inverter intelligent frequency modulation method provided in an embodiment of the present application;

[0027] Figure 2 An overall flow chart provided for the embodiments of the present application;

[0028] Figure 3 A statistical diagram of changes in the grid voltage change compliance value-voltage monitoring compliance evaluation index provided in an embodiment of the present application;

[0029] Figure 4 A schematic diagram of the structure of a photovoltaic inverter intelligent frequency modulation system provided in an embodiment of the present application;

[0030] Figure 5 A schematic diagram of a power grid island provided in an embodiment of the present application. DETAILED DESCRIPTION

[0031] The embodiments of the present application solve the problem of insufficient response in the intelligent frequency modulation process of photovoltaic inverters in the prior art by providing a photovoltaic inverter intelligent frequency modulation method, system and storage medium. The voltage monitoring circuit is evaluated to obtain voltage monitoring related data and a voltage monitoring compliance evaluation index is obtained based on the voltage monitoring related data. Whether to perform voltage frequency modulation is determined according to the voltage monitoring compliance evaluation index. Then, the frequency monitoring circuit is evaluated to obtain frequency monitoring related data and a frequency monitoring compliance evaluation index is obtained based on the frequency monitoring related data. Whether to perform frequency frequency modulation is determined according to the frequency monitoring compliance evaluation index. Finally, the power detection circuit is evaluated to obtain power monitoring related data and a power monitoring compliance evaluation index is obtained based on the power monitoring related data. Whether to perform power frequency modulation is determined according to the power monitoring compliance evaluation index. Thus, the response accuracy in the intelligent frequency modulation process of the photovoltaic inverter is improved.

[0032] The technical solution in the embodiment of the present application is to solve the problem of insufficient response during the intelligent frequency modulation process of the photovoltaic inverter. The overall idea is as follows:

[0033] By evaluating the voltage monitoring circuit to obtain the voltage monitoring compliance evaluation index and judging whether to perform voltage frequency modulation, then evaluating the frequency monitoring circuit to obtain the frequency monitoring compliance evaluation index and judging whether to perform frequency frequency modulation, and finally evaluating the power detection circuit to obtain the power monitoring compliance evaluation index and judging whether to perform power frequency modulation, the effect of improving the response accuracy of the photovoltaic inverter in the intelligent frequency modulation process is achieved.

[0034] In order to better understand the above technical solution, the above technical solution will be described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0035] like Figure 1 As shown, it is a flow chart of a photovoltaic inverter intelligent frequency modulation method provided by an embodiment of the present application, and the method includes the following steps: S1, voltage monitoring compliance assessment: evaluating the voltage monitoring circuit to obtain voltage monitoring related data, obtaining a voltage monitoring compliance assessment index based on the voltage monitoring related data, and judging whether to perform voltage frequency modulation according to the voltage monitoring compliance assessment index. The voltage frequency modulation is used to improve the stability of the output voltage of the power grid and the photovoltaic inverter, and the voltage monitoring compliance assessment index is used to evaluate the compliance of the voltage change; S2, frequency monitoring compliance assessment: evaluating the frequency monitoring circuit to obtain frequency monitoring related data, and obtaining a voltage monitoring compliance assessment index based on the frequency monitoring related data. Obtain the frequency monitoring compliance assessment index, and determine whether to perform frequency modulation based on the frequency monitoring compliance assessment index. Frequency modulation is used to improve the stability of the output frequency of the power grid and photovoltaic inverters, and the frequency monitoring compliance assessment index is used to evaluate the compliance of frequency changes. S3, power monitoring compliance assessment: evaluate the power detection circuit to obtain power monitoring related data, and obtain the power monitoring compliance assessment index based on the power monitoring related data. Determine whether to perform power frequency modulation based on the power monitoring compliance assessment index. Power frequency modulation is used to improve the stability of the output power of the power grid and photovoltaic inverters, and the power monitoring compliance assessment index is used to evaluate the compliance of output power changes.

[0036] It should be added that the voltage monitoring related data include grid voltage change, photocurrent, open circuit voltage, battery internal resistance, maximum load current and transmission line impedance; frequency monitoring related data include the minimum period of current fluctuation and the maximum frequency deviation; power monitoring related data include inverter output voltage, inverter output current, phase angle and on-resistance; grid voltage change represents the maximum value of grid voltage change within a preset time period, that is, the maximum value of the difference between the maximum and minimum values ​​of grid voltage within the preset time period; photocurrent represents the average value of current generated by photovoltaic cells within the preset time period; open circuit voltage represents the average value of open circuit voltage of photovoltaic cells within the preset time period; inverter output voltage represents the value of the first preset time period. The output voltage of the photovoltaic inverter when the beam is on; the inverter output current represents the output current of the photovoltaic inverter at the end of the first preset time period; the phase angle represents the phase angle between the output voltage and the output current of the photovoltaic inverter within the first preset time period; the on-resistance represents the on-resistance of the photovoltaic inverter within the first preset time period; the preset time period meets the lighting condition requirements, and the light intensity and lighting time will directly affect the current output of the photovoltaic cell. Therefore, when measuring the photocurrent, it is necessary to ensure that the lighting conditions within the preset time period meet the preset light intensity and preset light time. The preset light intensity and preset light time are set by the preset personnel. The first preset time period represents the preset time period corresponding to the voltage frequency modulation and the frequency frequency modulation.

[0037] like Figure 2 As shown, it is the overall flow chart provided by the embodiment of the present application. The mutual influence relationship between the voltage monitoring compliance evaluation index, the frequency monitoring compliance evaluation index and the power monitoring compliance evaluation index constitutes the basis of the frequency modulation of the photovoltaic inverter. The stability of voltage is the premise of frequency stability. The reduction of the voltage monitoring compliance evaluation index may indirectly lead to the reduction of the frequency monitoring compliance evaluation index. The stability of voltage and frequency directly affect the stability of the output power. According to the voltage monitoring compliance evaluation index, the frequency monitoring compliance evaluation index and the power monitoring compliance evaluation index, it is judged whether to perform response frequency modulation (voltage frequency modulation, frequency frequency modulation and power frequency modulation). Specifically, when the voltage monitoring compliance evaluation index is not within the preset voltage monitoring compliance range, voltage frequency modulation is performed, when the frequency monitoring compliance evaluation index is not within the preset frequency monitoring compliance range, frequency frequency modulation is performed, and when the power monitoring compliance evaluation index is not within the preset power monitoring compliance range, power frequency modulation is performed. By real-time monitoring of the changes in the voltage monitoring compliance evaluation index, the frequency monitoring compliance evaluation index and the power monitoring compliance evaluation index and taking corresponding frequency modulation measures, it is helpful to ensure the stable operation of the power grid and the photovoltaic inverter, thereby realizing the improvement of the response accuracy in the process of intelligent frequency modulation of the photovoltaic inverter.

[0038] It needs to be explained that, within a preset time period, the grid voltage is monitored in real time by a voltage sensor to measure the grid voltage change and the open-circuit voltage, the current generated by the photovoltaic cell is monitored in real time by a current sensor to obtain the photogenerated current, the load current connected to the output end of the photovoltaic inverter is monitored in real time by a current sensor and then statistical analysis is performed to obtain the maximum load current of the photogenerated current, the internal resistance of the photovoltaic cell is measured by a battery internal resistance tester to obtain the battery internal resistance, and the impedance of the transmission line is measured by an impedance tester to obtain the transmission line impedance.

[0039] During the preset time period, the current fluctuation is monitored in real time by the current sensor and the digital oscilloscope, and then statistical analysis is performed to obtain the minimum period of current fluctuation. The grid frequency is monitored in real time by the frequency meter and the digital oscilloscope, and then statistical analysis is performed to obtain the maximum frequency deviation, that is, the maximum value of the frequency deviation measured in the preset time period.

[0040] During a first preset time period, the current at the output end of the photovoltaic inverter is measured by a current sensor to obtain the inverter output current, the voltage at the output end of the photovoltaic inverter is measured by a voltage sensor to obtain the inverter output voltage, the phase angle between the inverter output voltage and the output current is measured by a phase meter and a digital oscilloscope, and the on-resistance of the photovoltaic inverter is measured by an on-resistance tester.

[0041] Furthermore, the specific process of obtaining the voltage monitoring compliance evaluation index based on the voltage monitoring related data is as follows: the grid voltage change compliance value (i.e., the voltage monitoring compliance evaluation index in the limiting expression) is obtained by performing a ratio operation on the sum of the grid voltage change amount and the preset voltage change maximum threshold obtained from the database and twice the preset voltage change maximum threshold. The grid voltage change compliance value is used to reflect the fluctuation degree of the grid voltage within the preset time period; the photovoltaic cell output voltage compliance value (i.e., the voltage monitoring compliance evaluation index in the restriction expression) is obtained by performing a ratio operation on the sum of the initial photovoltaic cell output voltage and the preset photovoltaic cell output voltage average threshold obtained from the database and twice the preset photovoltaic cell output voltage average threshold. ), the initial photovoltaic cell output voltage is obtained by performing a difference operation between the open circuit voltage and the product of the photocurrent and the internal resistance of the cell; the photovoltaic cell output voltage compliance value is used to reflect the compliance degree of the photovoltaic cell output voltage within the preset time period; the transmission line voltage drop compliance value (i.e., the voltage monitoring compliance evaluation index in the limiting expression) is obtained by performing a ratio operation between the sum of the initial transmission line voltage drop and the preset transmission line voltage drop maximum threshold obtained from the database and twice the preset transmission line voltage drop maximum threshold. ), the initial transmission line voltage drop is represented by the result of the product operation of the maximum load current and the transmission line impedance; the transmission line voltage drop compliance value is used to reflect the compliance of the transmission line voltage drop within a preset time period; the obtained grid voltage change compliance value, photovoltaic cell output voltage compliance value and transmission line voltage drop compliance value and the first preset inverter weight, the second preset inverter weight and the third preset inverter weight obtained from the database are combined to obtain the voltage monitoring compliance evaluation index; the first preset inverter weight is used to reflect the influence of the grid voltage change compliance value on the voltage monitoring compliance evaluation index within the preset time period; the second preset inverter weight is used to reflect the influence of the photovoltaic cell output voltage compliance value on the voltage monitoring compliance evaluation index within the preset time period; the third preset inverter weight is used to reflect the influence of the transmission line voltage drop compliance value on the voltage monitoring compliance evaluation index within the preset time period.

[0042] The voltage monitoring compliance assessment index is obtained by the following method:

[0043] ;

[0044] ;

[0045] ;

[0046] ;

[0047] In the formula, Indicates that the voltage monitoring meets the evaluation index in the xth preset time period, , x represents the number of the preset time period, s represents the total number of preset time periods, Indicates that the grid voltage change meets the value in the xth preset time period, Indicates that the photovoltaic cell output voltage meets the value in the xth preset time period, Indicates the transmission line voltage drop compliance value in the xth preset time period, Indicates the change in grid voltage in the xth preset time period, represents the photocurrent in the xth preset time period, represents the open circuit voltage at the xth preset time period, Indicates the internal resistance of the battery at the xth preset time period, Indicates the maximum load current in the xth preset time period, represents the transmission line impedance, Indicates the maximum threshold of preset voltage change. Indicates the maximum threshold of voltage drop of the preset transmission line. Indicates the maximum threshold of voltage drop of the preset transmission line. represents the first preset inverter weight, represents the second preset inverter weight, represents the third preset inverter weight, and e represents a natural constant.

[0048] In this embodiment, the aforementioned database is a database for storing various types of setting data established before the design of a photovoltaic inverter intelligent frequency regulation method provided in an embodiment of the present application. The database includes but is not limited to voltage change, transmission line voltage drop, grid frequency, etc., and various numerical values ​​therein are directly set by technical personnel. For example, the preset maximum voltage change threshold is represented by the maximum value of the grid voltage change in the historical time period in the database, the preset photovoltaic cell output voltage average threshold is represented by the average value of the photovoltaic cell output voltage in the historical time period in the database, and the preset transmission line voltage drop maximum threshold is represented by the maximum value of the transmission line voltage drop in the historical time period in the database.

[0049] It should be added that a mapping set of grid voltage change compliance values, photovoltaic cell output voltage compliance values, transmission line voltage drop compliance values ​​and corresponding weights is pre-set in the database. The mapping set is used to describe the mapping relationship between grid voltage change compliance values, photovoltaic cell output voltage compliance values, transmission line voltage drop compliance values ​​and corresponding weights. The mapping relationship can be a one-to-one correspondence or a many-to-one relationship. In this embodiment, the value range is 0-1. By inputting the real-time grid voltage change compliance value, photovoltaic cell output voltage compliance value and transmission line voltage drop compliance value into the mapping set, the corresponding first preset inverter weight, second preset inverter weight and third preset inverter weight can be obtained.

[0050] like Figure 3 As shown, it is a statistical diagram of the change of the grid voltage change compliance value-voltage monitoring compliance evaluation index provided in the embodiment of the present application, specifically assuming that: the grid voltage change compliance value The range is 0.6-0.9, and the photovoltaic cell output voltage meets the value Fixed to 0.75, the voltage drop of the transmission line meets the value is fixed to 0.65, the first preset inverter weight, the second preset inverter weight and the third preset inverter weight are fixed to 0.4, 0.3 and 0.3 respectively, Figure 3 It can be seen that as the grid voltage change compliance value gradually increases, the voltage monitoring compliance evaluation index gradually decreases, which means that the fluctuation degree of the grid voltage gradually increases, resulting in a gradual decrease in the compliance of the voltage change.

[0051] It should be understood that the algorithm of this embodiment combines the voltage monitoring related data analysis to obtain the voltage monitoring compliance evaluation index. The greater the change in the grid voltage, the greater the degree of change in the grid voltage, which may cause the voltage monitoring compliance evaluation index to decrease. The greater the maximum load current and the transmission line impedance, the greater the resistance of the transmission line, which may cause the voltage monitoring compliance evaluation index to decrease. The greater the open circuit voltage, the smaller the photocurrent, which means the greater the compliance of the photovoltaic cell output voltage, which may cause the voltage monitoring compliance evaluation index to increase.

[0052] It should be understood that the voltage monitoring related data in the algorithm of this embodiment does not exist independently, but has mutual correlation, and needs comprehensive analysis. The greater the grid voltage fluctuation, that is, the greater the grid voltage change, the more likely it is that the connection between the photovoltaic cell and the grid will be unstable, thereby affecting the stable output of the photocurrent. The increase in photocurrent usually means that the current that the photovoltaic cell can provide increases, which may increase the maximum load current. The higher the open circuit voltage, the higher the voltage that the photovoltaic cell can provide, which may increase the maximum load current. The increase in the maximum load current will increase the current in the transmission line, thereby increasing the loss and heat generation of the transmission line, which may cause the impedance of the transmission line to change (such as an increase in resistance), thereby affecting the stability of the grid voltage, and may cause the voltage monitoring compliance evaluation index to decrease. The parameters of the algorithm of this embodiment need to consider the impact on the results together. By analyzing the comprehensive impact between the parameters, the accurate quantification of the compliance of the voltage change evaluation is achieved, thereby achieving the improvement of the response accuracy in the intelligent frequency modulation process of the photovoltaic inverter.

[0053] Furthermore, a specific method for determining whether to perform voltage frequency modulation based on the voltage monitoring compliance assessment index is as follows: determine whether the voltage monitoring compliance assessment index is within a preset voltage monitoring compliance range obtained from a database; when the voltage monitoring compliance assessment index is within the preset voltage monitoring compliance range (including the voltage monitoring compliance assessment index taking the upper and lower limits of the preset voltage monitoring compliance range), it indicates that the voltage is qualified and voltage frequency modulation is not performed; when the voltage monitoring compliance assessment index is not within the preset voltage monitoring compliance range, it indicates that the voltage is abnormal and voltage frequency modulation is performed; the specific steps of voltage frequency modulation are as follows: the first step is to perform photovoltaic cell maximum power point tracking; when the monitored voltage monitoring compliance assessment index is within the preset voltage monitoring compliance range, stop voltage frequency modulation, otherwise execute the second step, photovoltaic cell maximum power point tracking means adjusting the output voltage of the photovoltaic inverter through the MPPT (Maximum Power Point Tracking) algorithm; the second step is to perform voltage detection through a voltage detection algorithm; when the monitored voltage monitoring compliance assessment index is within the preset voltage monitoring compliance range, stop voltage frequency modulation, otherwise trigger island protection.

[0054] In this embodiment, the upper limit of the preset voltage monitoring compliance range is represented by the maximum value of the voltage monitoring compliance evaluation index of the historical time period in the database, and the lower limit of the preset voltage monitoring compliance range is represented by the average value of the voltage monitoring compliance evaluation index of the historical time period in the database.

[0055] Triggering island protection means that if an island effect is detected, a prompt control relay is sent to disconnect the energy storage system from the grid and send out a warning signal, or a high-speed controller such as DSP (Digital Signal Processing) or FPGA (Field-Programmable Gate Array) is used for monitoring to ensure that a quick response can be made after the island effect is detected to disconnect the energy storage system from the grid. The MPPT algorithm is used to dynamically adjust the output voltage of the photovoltaic inverter to maximize the output power of the photovoltaic cell. The goal of the MPPT algorithm is to find and track the maximum power point to ensure that the photovoltaic system always works in the optimal state. The voltage detection algorithm (voltage harmonic detection algorithm based on Fourier transform) is usually used to detect abnormal fluctuations in grid voltage (such as overvoltage, undervoltage, etc.). The voltage harmonic detection method determines the voltage state by detecting the total harmonic distortion of the output voltage of the grid-connected inverter (photovoltaic inverter); the voltage detection algorithm (voltage harmonic detection algorithm based on Fourier transform) is used to monitor the grid voltage state in real time to ensure the stable operation of the photovoltaic inverter system, thereby improving the response accuracy during the intelligent frequency regulation of the photovoltaic inverter.

[0056] Furthermore, the frequency monitoring compliance evaluation index is calculated by the grid frequency compliance value (i.e., ), grid angular frequency compliance value (i.e., frequency monitoring compliance evaluation index in the limit expression ), grid frequency deviation compliance value (i.e., frequency monitoring compliance evaluation index in the limit expression ) analysis shows that: the grid frequency compliance value is used to reflect the compliance degree of the grid frequency within the preset time period, and the grid frequency compliance value is represented by the result of the ratio operation of the sum of the initial grid frequency and the preset grid frequency maximum threshold obtained from the database and 2 times the preset grid frequency maximum threshold, and the initial grid frequency is represented by the inverse of the minimum period of current fluctuation; the grid angular frequency compliance value is used to reflect the compliance degree of the grid angular frequency within the preset time period, and the grid angular frequency compliance value is represented by the result of the ratio operation of the sum of the initial grid angular frequency and the preset grid frequency maximum threshold obtained from the database and 2 times the preset grid angular frequency maximum threshold, and the initial grid angular frequency is obtained by processing the initial grid frequency; the grid frequency offset compliance value is used to reflect the compliance degree of the grid frequency offset within the preset time period, and the grid frequency offset compliance value is represented by the result of the ratio operation of 2 times the preset grid frequency offset maximum threshold obtained from the database and the frequency offset maximum value and the sum of the preset grid frequency offset maximum threshold.

[0057] Among them, the frequency monitoring compliance assessment index is obtained by the following method:

[0058] ;

[0059] ;

[0060] ;

[0061] ;

[0062] In the formula, Indicates the frequency monitoring compliance evaluation index in the xth preset time period, , x represents the number of the preset time period, s represents the total number of preset time periods, Indicates that the grid frequency meets the value in the xth preset time period, Indicates the grid angular frequency compliance value in the xth preset time period, Indicates the grid frequency deviation compliance value in the xth preset time period, Indicates the minimum period of current fluctuation in the xth preset time period, Indicates the maximum value of the frequency deviation in the xth preset time period, Indicates the preset maximum threshold of grid frequency. Indicates the preset maximum threshold of grid angular frequency, represents the preset maximum threshold of grid frequency deviation, e represents a natural constant, Generally, 3.14 is taken.

[0063] In this embodiment, the preset grid frequency maximum threshold is represented by the maximum value of the grid frequency in the historical time period in the database, the preset grid angular frequency maximum threshold is represented by the maximum value of the grid angular frequency in the historical time period in the database, and the preset grid frequency deviation maximum threshold is represented by the maximum value of the grid frequency deviation in the historical time period in the database.

[0064] Specifically, assuming that the grid frequency meets the value The range is 0.6-0.9, and the grid angular frequency meets the value The range is 0.6-0.9, and the grid frequency deviation meets the value The range is 0.6-0.9, as shown in Table 1, which is a statistical table of changes in the frequency monitoring compliance evaluation index provided in the embodiment of the present application:

[0065] Table 1 Statistics of changes in frequency monitoring compliance assessment index

[0066]

[0067] It can be seen from the above table that as the grid frequency compliance value, grid angular frequency compliance value and grid frequency offset compliance value gradually increase, the frequency monitoring compliance assessment index gradually increases, which means that the compliance of frequency changes gradually improves.

[0068] It should be understood that the algorithm of this embodiment combines the frequency monitoring related data analysis to obtain the frequency monitoring compliance evaluation index. The smaller the minimum period of current fluctuation, the higher the degree of compliance of the grid frequency and the grid angular frequency, which may lead to an increase in the frequency monitoring compliance evaluation index. The larger the maximum frequency offset, the greater the degree of grid frequency offset, which may lead to a decrease in the frequency monitoring compliance evaluation index. However, the frequency monitoring related data in the algorithm of this embodiment do not exist independently, but are interrelated and need to be comprehensively analyzed. Changes in the minimum period of current fluctuation may cause the offset of the grid frequency. The larger the frequency offset, the greater the disturbance to the grid, which in turn affects the frequency monitoring compliance evaluation index, which may lead to a decrease in the frequency monitoring compliance evaluation index. When the grid is disturbed, the current fluctuation may increase (that is, the minimum period of current fluctuation becomes smaller), and the frequency may also shift, which may lead to a decrease in the frequency monitoring compliance evaluation index. The parameters of the algorithm of this embodiment need to consider the impact on the results together. By analyzing the comprehensive influence between the parameters, the accurate quantification of the compliance of the evaluation frequency change is achieved, thereby achieving the improvement of the response accuracy in the intelligent frequency modulation process of the photovoltaic inverter.

[0069] Furthermore, the specific process of determining whether to perform frequency modulation according to the frequency monitoring compliance evaluation index is as follows: determining whether the frequency monitoring compliance evaluation index is within the preset frequency monitoring compliance range obtained from the database; when the frequency monitoring compliance evaluation index is within the preset frequency monitoring compliance range (including the frequency monitoring compliance evaluation index taking the upper and lower limits of the preset frequency monitoring compliance range), it indicates that the frequency is normal and frequency modulation is not performed; when the frequency monitoring compliance evaluation index is not within the preset frequency monitoring compliance range, it indicates that the frequency is abnormal and frequency modulation is performed; the specific process of frequency modulation is as follows: step one, performing frequency control; when the monitored frequency monitoring compliance evaluation index is within the preset frequency monitoring compliance range, stopping frequency modulation; otherwise, executing step two; frequency control means that frequency control means making the frequency more stable through PWM (PulseWidth Modulation) technology; step two, performing frequency detection through a frequency detection algorithm; when the monitored frequency monitoring compliance evaluation index is within the preset frequency monitoring compliance range, stopping frequency modulation; otherwise, triggering island protection.

[0070] In this embodiment, the upper limit of the preset frequency monitoring compliance range is represented by the maximum value of the frequency monitoring compliance evaluation index of the historical time period in the database, and the lower limit of the preset frequency monitoring compliance range is represented by the average value of the frequency monitoring compliance evaluation index of the historical time period in the database.

[0071] Frequency detection is performed through frequency detection algorithms, such as the fast Fourier transform algorithm, which estimates the frequency of the power grid based on the characteristics of the sampled signal to achieve real-time monitoring of the power grid frequency status. PWM technology controls the components in the circuit by changing the pulse width of the signal, thereby achieving precise control of the output signal. It has a faster response speed and helps to maintain the stability of the power grid frequency, thereby achieving improved response accuracy during the intelligent frequency modulation process of the photovoltaic inverter.

[0072] Further, the specific process of obtaining the power monitoring compliance evaluation index based on the power monitoring related data is as follows: Obtain the inverter power compliance value (that is, ) and the inverter power loss compliance value (i.e., the power monitoring compliance evaluation index in the limit expression ); The power monitoring compliance evaluation index is obtained through the inverter power compliance value and the inverter power loss compliance value, the voltage monitoring compliance evaluation index after voltage frequency modulation, and the frequency monitoring compliance evaluation index after frequency frequency modulation.

[0073] The method for obtaining the power monitoring compliance assessment index is:

[0074] ;

[0075] ;

[0076] ;

[0077] In the formula, Indicates that the power monitoring meets the evaluation index in the yth first preset time period, , y represents the number of the first preset time period, c represents the total number of the first preset time period, represents the inverter power compliance value in the yth first preset time period, represents the inverter power loss compliance value in the yth first preset time period, It indicates that the voltage monitoring after voltage frequency modulation in the yth first preset time period meets the evaluation index, Indicates that the frequency monitoring compliance evaluation index for frequency modulation during the yth first preset time period, represents the inverter output voltage in the yth first preset time period, represents the inverter output current in the yth first preset time period, represents the phase angle in the yth first preset time period, represents the maximum load current in the yth first preset time period, represents the on-resistance, Indicates the preset maximum inverter power threshold. represents the preset inverter power loss average threshold value, and e represents a natural constant;

[0078] It needs to be explained that the inverter power compliance value is used to reflect the compliance degree of the inverter power within the preset time period; the inverter power loss compliance value is used to reflect the compliance degree of the inverter power loss within the preset time period; the inverter power compliance value is represented by the result of the ratio operation of the sum of the initial inverter power and the preset inverter power maximum threshold obtained from the database and twice the preset inverter power average threshold; the initial inverter power is obtained by processing the inverter output voltage, inverter output current and phase angle; the inverter power loss compliance value is represented by the result of the ratio operation of the sum of the initial inverter power loss value and the preset inverter power loss average threshold obtained from the database and twice the preset inverter power loss average threshold; the initial inverter power loss value is obtained by processing the maximum load current and on-resistance.

[0079] In this embodiment, the preset inverter power maximum threshold is represented by the maximum value of the inverter power in the historical time period in the database, and the preset inverter power loss average threshold is represented by the average value of the inverter power loss in the historical time period in the database.

[0080] It should be understood that the algorithm of this embodiment combines power monitoring related data, voltage monitoring compliance evaluation index and frequency monitoring compliance evaluation index analysis to obtain the power monitoring compliance evaluation index. The larger the inverter output voltage, inverter output current and phase angle, the higher the inverter power compliance, which may lead to an increase in the power monitoring compliance evaluation index. The larger the maximum load current, the greater the power loss compliance, which may lead to a decrease in the power monitoring compliance evaluation index.

[0081] In the algorithm of this embodiment, the power monitoring related data, the voltage monitoring compliance evaluation index and the frequency monitoring compliance evaluation index do not exist independently, but are interrelated. The size of the inverter output voltage directly affects the size of the inverter output power. The higher the inverter output voltage, the greater the inverter output voltage power under the same inverter output voltage and current. The size of the inverter output current also affects the output power. When the inverter output voltage is constant, the greater the inverter output voltage and current, the greater the inverter output voltage power, and the changes in the inverter output voltage and output current are mutually restricted. When the load remains unchanged, the increase in output voltage may lead to a decrease in output current. When the voltage monitoring compliance evaluation index is higher, the inverter output voltage may be more stable. The higher the frequency monitoring compliance evaluation index, the more accurate the frequency of the inverter output current, which may cause the power monitoring compliance evaluation index to increase. The parameters of the algorithm of this embodiment need to consider the impact on the results together. By analyzing the comprehensive influence between the parameters, the accurate quantification of the compliance of the output power change is achieved, thereby achieving the improvement of the response accuracy in the intelligent frequency modulation process of the photovoltaic inverter.

[0082] Furthermore, the specific process of judging whether to perform power frequency modulation according to the power monitoring compliance evaluation index is as follows: judging whether the power monitoring compliance evaluation index is within the preset power monitoring compliance range obtained from the database: when the power monitoring compliance evaluation index is within the preset power monitoring compliance range (including the power monitoring compliance evaluation index taking the upper and lower limits of the preset power monitoring compliance range), it indicates that the power is normal and power frequency modulation is not performed; when the power monitoring compliance evaluation index is not within the preset power monitoring compliance range, it indicates that the power is abnormal and power frequency modulation is performed; the specific process of power frequency modulation is as follows: V1, performing optical fiber communication, when the monitored power monitoring compliance evaluation index is within the preset power monitoring compliance range, power frequency modulation is stopped, otherwise V2 is executed, performing optical fiber communication indicates improving the communication coordination between the photovoltaic inverter and the power grid through optical fiber communication technology; V2, performing power detection through the power balance detection algorithm, when the monitored power monitoring compliance evaluation index is within the preset power monitoring compliance range, power frequency modulation is stopped, otherwise island protection is triggered.

[0083] In this embodiment, the upper limit of the preset power monitoring compliance range is represented by the maximum value of the power monitoring compliance evaluation index of the historical time period in the database, and the lower limit of the preset power monitoring compliance range is represented by the average value of the power monitoring compliance evaluation index of the historical time period in the database.

[0084] Power balance detection algorithms (such as the power difference method) are used to monitor and evaluate the balance between the output power of photovoltaic inverters and the demand of the power grid. Optical fiber communication technologies, such as GPON (Gigabit-capable Passive Optical Network) technology, have the characteristics of high-speed transmission, which can ensure the real-time and accurate transmission of data between photovoltaic inverters and the power grid, and help photovoltaic inverters to quickly respond to changes in power grid demand and adjust output power and frequency to maintain stable operation of the system, thereby improving the response accuracy during the intelligent frequency modulation process of photovoltaic inverters.

[0085] like Figure 4 As shown, it is a structural schematic diagram of a photovoltaic inverter intelligent frequency regulation system provided in an embodiment of the present application. A photovoltaic inverter intelligent frequency regulation system provided in an embodiment of the present application includes a voltage monitoring compliance assessment module, a frequency monitoring compliance assessment module and a power monitoring compliance assessment module: wherein the voltage monitoring compliance assessment module is used to evaluate the voltage monitoring circuit to obtain voltage monitoring related data, obtain a voltage monitoring compliance assessment index based on the voltage monitoring related data, and determine whether to perform voltage frequency regulation according to the voltage monitoring compliance assessment index. The voltage frequency regulation is used to improve the stability of the output voltage of the power grid and the photovoltaic inverter, and the voltage monitoring compliance assessment index is used to evaluate the compliance of the voltage change; the frequency monitoring compliance assessment module is used to evaluate the frequency monitoring circuit The circuit is evaluated to obtain frequency monitoring related data, a frequency monitoring compliance assessment index is obtained based on the frequency monitoring related data, and whether to perform frequency modulation is determined according to the frequency monitoring compliance assessment index. Frequency modulation is used to improve the stability of the output frequency of the power grid and photovoltaic inverter, and the frequency monitoring compliance assessment index is used to evaluate the compliance of frequency changes; the power monitoring compliance assessment module is used to evaluate the power detection circuit to obtain power monitoring related data, a power monitoring compliance assessment index is obtained based on the power monitoring related data, and whether to perform power frequency modulation is determined according to the power monitoring compliance assessment index. Power frequency modulation is used to improve the stability of the output power of the power grid and photovoltaic inverter, and the power monitoring compliance assessment index is used to evaluate the compliance of output power changes.

[0086] Among them, the embodiment of the present application also provides a computer-readable storage medium for storing a program, and when the program is executed by a processor, a photovoltaic inverter intelligent frequency regulation method is implemented.

[0087] In this embodiment, if Figure 5As shown, it is a schematic diagram of a power grid island provided in an embodiment of the present application, Figure 5 It can be seen that when the power grid is out of power, the independent power supply area formed will quickly disconnect after detecting the power grid outage to prevent the occurrence of island effect. The voltage monitoring compliance assessment module, frequency monitoring compliance assessment module and power monitoring compliance assessment module are interconnected and interact with each other in the photovoltaic inverter system. The data monitored by the voltage monitoring circuit, frequency monitoring circuit and power detection circuit are interrelated, that is, voltage monitoring related data, frequency monitoring related data and power monitoring related data. Changes in voltage and frequency may affect the stability of output power; fluctuations in output power may also reflect instability in voltage or frequency; the voltage monitoring compliance assessment module determines whether voltage frequency modulation is needed based on the voltage monitoring compliance assessment index. When the voltage monitoring compliance assessment index is not within the preset voltage monitoring compliance range, it indicates that the voltage is The voltage is abnormal, which affects the stability of frequency monitoring and power monitoring. The frequency monitoring compliance assessment module determines whether frequency modulation is needed according to the frequency monitoring compliance assessment index. When the frequency monitoring compliance assessment index is not within the preset frequency monitoring compliance range, it indicates that the frequency is abnormal, which affects the stability of power monitoring. The power monitoring compliance assessment module determines whether power modulation is needed according to the power monitoring compliance assessment index. When the power monitoring compliance assessment index is not within the preset power monitoring compliance range, it indicates that the power is abnormal, reflecting the instability of voltage or frequency. Through the voltage monitoring compliance assessment module, the frequency monitoring compliance assessment module and the power monitoring compliance assessment module, the stability of the power grid and the photovoltaic inverter in terms of voltage, frequency and power is ensured together, thereby realizing the improvement of the response accuracy in the process of intelligent frequency modulation of the photovoltaic inverter.

[0088] To summarize, the embodiment of the present application evaluates the voltage monitoring circuit to obtain the voltage monitoring compliance evaluation index and determines whether to perform voltage frequency modulation, then evaluates the frequency monitoring circuit to obtain the frequency monitoring compliance evaluation index and determines whether to perform frequency frequency modulation, and finally evaluates the power detection circuit to obtain the power monitoring compliance evaluation index and determines whether to perform power frequency modulation, thereby improving the reliability of the intelligent frequency modulation of the photovoltaic inverter, and further improving the response accuracy during the intelligent frequency modulation process of the photovoltaic inverter, effectively solving the problem of insufficient response during the intelligent frequency modulation process of the photovoltaic inverter in the prior art.

[0089] It will be appreciated by those skilled in the art that embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Furthermore, the present invention may take the form of a computer program product implemented 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.

[0090] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0091] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0092] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0093] Although the preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0094] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A photovoltaic inverter intelligent frequency modulation method, characterized in that: The following steps are involved: S1, evaluating the voltage monitoring circuit to obtain voltage monitoring related data, obtaining a voltage monitoring compliance evaluation index based on the voltage monitoring related data, and judging whether to perform voltage frequency modulation according to the voltage monitoring compliance evaluation index, wherein the voltage frequency modulation is used to improve the stability of the output voltage of the power grid and the photovoltaic inverter, and the voltage monitoring compliance evaluation index is used to evaluate the compliance of the voltage change; S2, evaluating the frequency monitoring circuit to obtain frequency monitoring related data, obtaining a frequency monitoring compliance evaluation index based on the frequency monitoring related data, and judging whether to perform frequency modulation according to the frequency monitoring compliance evaluation index, wherein the frequency modulation is used to improve the stability of the output frequency of the power grid and the photovoltaic inverter, and the frequency monitoring compliance evaluation index is used to evaluate the compliance of the frequency change; S3, evaluating the power detection circuit to obtain power monitoring related data, obtaining a power monitoring compliance evaluation index based on the power monitoring related data, and judging whether to perform power frequency modulation according to the power monitoring compliance evaluation index, wherein the power frequency modulation is used to improve the stability of the output power of the power grid and the photovoltaic inverter, and the power monitoring compliance evaluation index is used to evaluate the compliance of the output power change; The specific process of obtaining the voltage monitoring compliance evaluation index based on the voltage monitoring related data is as follows: The grid voltage change compliance value is obtained by performing a ratio operation on the sum of the grid voltage change amount and the preset voltage change maximum threshold obtained from the database and twice the preset voltage change maximum threshold; The photovoltaic cell output voltage compliance value is obtained by performing a ratio operation on the sum of the initial photovoltaic cell output voltage and the preset photovoltaic cell output voltage average threshold obtained from the database and twice the preset photovoltaic cell output voltage average threshold, wherein the initial photovoltaic cell output voltage is obtained by performing a difference operation on the open circuit voltage and the product of the photocurrent and the battery internal resistance; The transmission line voltage drop compliance value is obtained by performing a ratio operation on the sum of the initial transmission line voltage drop and the preset transmission line voltage drop maximum threshold obtained from the database and twice the preset transmission line voltage drop maximum threshold; The transmission line voltage drop compliance value is used to reflect the compliance of the transmission line voltage drop within a preset time period; The obtained grid voltage variation compliance value, photovoltaic cell output voltage compliance value and transmission line voltage drop compliance value are combined with the first preset inverter weight, the second preset inverter weight and the third preset inverter weight obtained from the database to obtain a voltage monitoring compliance evaluation index.

2. A photovoltaic inverter intelligent frequency modulation method as claimed in claim 1, characterized in that: The voltage monitoring related data include grid voltage variation, photovoltaic current, open circuit voltage, battery internal resistance, maximum load current and transmission line impedance; The frequency monitoring related data include the minimum period of current fluctuation and the maximum value of frequency deviation; The power monitoring related data includes inverter output voltage, inverter output current, phase angle and on-resistance; The grid voltage variation represents the maximum value of the grid voltage variation within a preset time period; The photogenerated current represents the average value of the current generated by the photovoltaic cell within a preset time period; The open circuit voltage represents the average value of the open circuit voltage of the photovoltaic cell within a preset time period; The inverter output voltage represents the output voltage of the photovoltaic inverter at the end of the first preset time period; The inverter output current represents the output current of the photovoltaic inverter at the end of the first preset time period; The phase angle represents the phase angle between the output voltage and the output current of the photovoltaic inverter within the first preset time period; The on-resistance represents the on-resistance of the photovoltaic inverter within a first preset time period; The first preset time period represents a preset time period corresponding to voltage frequency modulation and frequency frequency modulation.

3. A photovoltaic inverter intelligent frequency modulation method as claimed in claim 1, characterized in that: The specific method for determining whether to perform voltage frequency modulation according to the voltage monitoring compliance evaluation index is as follows: Determine whether the voltage monitoring compliance evaluation index is within a preset voltage monitoring compliance range obtained from a database, and when the voltage monitoring compliance evaluation index is within the preset voltage monitoring compliance range, do not perform voltage frequency modulation; When the voltage monitoring compliance assessment index is not within the preset voltage monitoring compliance range, voltage frequency modulation is performed; The specific steps of voltage frequency modulation are as follows: The first step is to track the maximum power point of the photovoltaic cell. When the monitored voltage monitoring compliance assessment index is within the preset voltage monitoring compliance range, the voltage frequency modulation is stopped, otherwise the second step is executed; The second step is to perform voltage detection. When the monitored voltage monitoring compliance assessment index is within the preset voltage monitoring compliance range, the voltage frequency modulation is stopped, otherwise the island protection is triggered.

4. A photovoltaic inverter intelligent frequency modulation method as claimed in claim 2, characterized in that: The frequency monitoring compliance evaluation index is obtained by analyzing the grid frequency compliance value, grid angular frequency compliance value, and grid frequency offset compliance value: The grid frequency compliance value is used to reflect the compliance degree of the grid frequency within a preset time period. The grid frequency compliance value is represented by the result of a ratio operation between the sum of the initial grid frequency and the preset grid frequency maximum threshold obtained from the database and twice the preset grid frequency maximum threshold. The initial grid frequency is represented by the inverse of the minimum period of current fluctuation; The grid angular frequency compliance value is used to reflect the compliance degree of the grid angular frequency within a preset time period, and the grid angular frequency compliance value is represented by the result of a ratio operation between the sum of the initial grid angular frequency and the preset grid angular frequency maximum threshold obtained from the database and twice the preset grid angular frequency maximum threshold, and the initial grid angular frequency is obtained by processing the initial grid frequency; The grid frequency offset compliance value is used to reflect the compliance degree of the grid frequency offset within a preset time period. The grid frequency offset compliance value is represented by the result of a ratio operation between twice the preset grid frequency offset maximum threshold obtained from the database and the sum of the frequency offset maximum value and the preset grid frequency offset maximum threshold.

5. A photovoltaic inverter intelligent frequency modulation method as claimed in claim 4, characterized in that: The specific process of judging whether to perform frequency modulation according to the frequency monitoring compliance evaluation index is as follows: Determine whether the frequency monitoring compliance evaluation index is within the preset frequency monitoring compliance range obtained from the database, and when the frequency monitoring compliance evaluation index is within the preset frequency monitoring compliance range, do not perform frequency modulation; When the frequency monitoring compliance assessment index is not within the preset frequency monitoring compliance range, frequency modulation is performed; The specific process of the frequency modulation is as follows: Step 1: Perform frequency control. When the monitored frequency monitoring compliance assessment index is within the preset frequency monitoring compliance range, stop frequency modulation. Otherwise, perform step 2. Step 2: Perform frequency detection. When the monitored frequency monitoring compliance evaluation index is within the preset frequency monitoring compliance range, stop frequency modulation. Otherwise, island protection is triggered.

6. A photovoltaic inverter intelligent frequency modulation method as claimed in claim 2, characterized in that: The specific process of obtaining the power monitoring compliance evaluation index based on the power monitoring related data is as follows: Obtain the inverter power compliance value and the inverter power loss compliance value; The power monitoring compliance evaluation index is obtained through the inverter power compliance value and the inverter power loss compliance value, as well as the voltage monitoring compliance evaluation index after voltage frequency modulation and the frequency monitoring compliance evaluation index after frequency frequency modulation; The method for obtaining the power monitoring compliance evaluation index is: ； In the formula, Indicates that the power monitoring meets the evaluation index in the yth first preset time period, , y represents the number of the first preset time period, c represents the total number of the first preset time period, represents the inverter power compliance value in the yth first preset time period, represents the inverter power loss compliance value in the yth first preset time period, It indicates that the voltage monitoring after voltage frequency modulation in the yth first preset time period meets the evaluation index, represents a frequency monitoring compliance evaluation index for frequency modulation during the yth first preset time period, and e represents a natural constant; The inverter power compliance value is used to reflect the compliance degree of the inverter power within a preset time period; The inverter power loss compliance value is used to reflect the compliance level of the inverter power loss within a preset time period.

7. A photovoltaic inverter intelligent frequency modulation method as claimed in claim 6, characterized in that: The specific process of judging whether to perform power frequency modulation according to the power monitoring compliance evaluation index is as follows: When the power monitoring compliance assessment index is within the preset power monitoring compliance range, power frequency modulation is not performed; When the power monitoring compliance assessment index is not within the preset power monitoring compliance range, power frequency adjustment is performed; The specific process of the power frequency modulation is as follows: V1, for optical fiber communication, when the monitored power monitoring compliance evaluation index is within the preset power monitoring compliance range, the power frequency modulation is stopped, otherwise V2 is executed; V2, perform power detection. When the monitored power monitoring compliance evaluation index is within the preset power monitoring compliance range, stop power frequency modulation, otherwise trigger island protection.

8. A photovoltaic inverter intelligent frequency modulation system, characterized in that: Including voltage monitoring compliance assessment module, frequency monitoring compliance assessment module and power monitoring compliance assessment module: The voltage monitoring compliance assessment module is used to evaluate the voltage monitoring circuit to obtain voltage monitoring related data, obtain the voltage monitoring compliance assessment index based on the voltage monitoring related data, and determine whether to perform voltage frequency modulation according to the voltage monitoring compliance assessment index. The voltage frequency modulation is used to improve the stability of the output voltage of the power grid and the photovoltaic inverter. The voltage monitoring compliance assessment index is used to evaluate the compliance of the voltage change; The frequency monitoring compliance assessment module is used to evaluate the frequency monitoring circuit to obtain frequency monitoring related data, obtain the frequency monitoring compliance assessment index based on the frequency monitoring related data, and determine whether to perform frequency modulation according to the frequency monitoring compliance assessment index. The frequency modulation is used to improve the stability of the output frequency of the power grid and the photovoltaic inverter, and the frequency monitoring compliance assessment index is used to evaluate the compliance of the frequency change; The power monitoring compliance assessment module is used to evaluate the power detection circuit to obtain power monitoring related data, obtain the power monitoring compliance assessment index based on the power monitoring related data, and determine whether to perform power frequency modulation according to the power monitoring compliance assessment index. The power frequency modulation is used to improve the stability of the output power of the power grid and the photovoltaic inverter. The power monitoring compliance assessment index is used to evaluate the compliance of the output power change; The specific process of obtaining the voltage monitoring compliance evaluation index based on the voltage monitoring related data is as follows: The grid voltage change compliance value is obtained by performing a ratio operation on the sum of the grid voltage change amount and the preset voltage change maximum threshold obtained from the database and twice the preset voltage change maximum threshold; The photovoltaic cell output voltage compliance value is obtained by performing a ratio operation on the sum of the initial photovoltaic cell output voltage and the preset photovoltaic cell output voltage average threshold obtained from the database and twice the preset photovoltaic cell output voltage average threshold, wherein the initial photovoltaic cell output voltage is obtained by performing a difference operation on the open circuit voltage and the product of the photocurrent and the battery internal resistance; The transmission line voltage drop compliance value is obtained by performing a ratio operation on the sum of the initial transmission line voltage drop and the preset transmission line voltage drop maximum threshold obtained from the database and twice the preset transmission line voltage drop maximum threshold; The transmission line voltage drop compliance value is used to reflect the compliance of the transmission line voltage drop within a preset time period; The obtained grid voltage variation compliance value, photovoltaic cell output voltage compliance value and transmission line voltage drop compliance value are combined with the first preset inverter weight, the second preset inverter weight and the third preset inverter weight obtained from the database to obtain a voltage monitoring compliance evaluation index.

9. A computer-readable storage medium for storing a program, wherein when the program is executed by a processor, the method for intelligent frequency regulation of a photovoltaic inverter as claimed in any one of claims 1 to 7 is implemented.

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