A photovoltaic power station primary frequency modulation droop characteristic control method and system

Abstract

The present application relates to the technical field of primary frequency modulation of photovoltaic power station, and discloses a kind of primary frequency modulation droop characteristic control method and system of photovoltaic power station, the method comprises: real-time acquisition and grid-connected point frequency, synchronous acquisition voltage current signal, extract multi-dimensional feature;Based on the mode determination result of the multi-dimensional feature output by transient characteristic fingerprint library, if it is transient mode, lockout primary frequency modulation, if it is steady-state mode, calculate frequency deviation and judge whether the frequency deviation exceeds dead zone, if yes, according to the frequency deviation and irradiance level Switching droop characteristic form, and obtain first power target value;Determine the current frequency operating state, dynamically coordinate the first power target value and AGC instruction, determine second power target value;Generate each inverter response characteristic image, generate the frequency modulation instruction of each inverter in combination with the second power target value, significantly improve the response sensitivity, control accuracy and operating stability of primary frequency modulation of photovoltaic power station.

Description

Technical Field

[0001] This application relates to the field of primary frequency regulation technology for photovoltaic power plants, and in particular to a method and system for controlling the droop characteristics of primary frequency regulation in photovoltaic power plants. Background Technology

[0002] With a high proportion of new energy sources being connected to the grid, system frequency stability faces the dual challenges of reduced inertia and insufficient frequency regulation resources. As a static power source, photovoltaic power plants do not possess rotational inertia and must achieve primary frequency regulation through station-level active power control.

[0003] In existing technologies, linear or simple polygonal active-frequency droop characteristics with a fixed slope are commonly used, maintaining a constant droop rate across the entire frequency band. This design cannot meet the control requirements under different frequency disturbance intensities: it is sluggish in response to small frequency difference disturbances, and prone to power over-regulation or oscillation under large frequency difference disturbances. Furthermore, it does not consider the impact of random fluctuations in photovoltaic output on the effectiveness of the droop characteristics. Moreover, it often uses a "same-direction superposition, reverse-direction blocking" logic with a fixed frequency threshold, without considering the AGC command change rate, scheduling command priority, and frequency recovery dynamic process. Finally, it allocates power proportionally according to rated capacity or simply considers the current output of the inverter, resulting in some inverters responding with lag and slowing down the overall frequency regulation performance of the entire station. Summary of the Invention

[0004] To address the aforementioned technical problems, this application provides a method and system for controlling the primary frequency regulation droop characteristics of a photovoltaic power station, effectively solving the problems of sluggish response with small frequency differences, easy over-regulation with large frequency differences, unreasonable coordination logic, and the impact of allocation methods on frequency regulation performance in the prior art.

[0005] On one hand, the present invention provides a method for controlling the primary frequency regulation droop characteristics of a photovoltaic power station, comprising: Real-time acquisition of grid connection point frequency, synchronous acquisition of voltage and current signals, and extraction of multi-dimensional features; Based on the transient feature fingerprint database, the modality determination result of the multidimensional features is output, and the modality determination result includes transient modes and steady-state modes; If it is a transient mode, the first frequency modulation is blocked. If it is a steady-state mode, the frequency deviation is calculated and it is determined whether the frequency deviation exceeds the dead zone. If so, the droop characteristic mode is adaptively switched according to the frequency deviation and the irradiance level, and the first power target value is obtained. Determine the current frequency operating status, and dynamically coordinate the first power target value and AGC instructions based on the frequency operating status to determine the second power target value; Generate response characteristic profiles for each inverter, and generate frequency modulation commands for each inverter based on the response characteristic profiles and the second power target value.

[0006] Furthermore, based on the transient feature fingerprint database, the modality determination result of the multidimensional features is output, including: The multidimensional features include voltage amplitude abrupt change rate, frequency change rate, harmonic distortion rate, and three-phase imbalance. The multidimensional features are compared with the pre-set transient judgment thresholds in the transient feature fingerprint database, and the number of features exceeding the thresholds is counted. If the number of features is less than the preset number, it is determined to be a steady-state mode; If the number of features is not less than the preset number, the initial transient flag and fault duration timing are triggered to obtain the fault duration of the initial transient flag; If the duration of the fault is within the preset short-circuit fault time window interval, it is determined that the transient mode has been entered. If it is lower than the lower limit of the time window interval, the initial transient flag is cleared and the steady-state mode is maintained. If it exceeds the upper limit of the time window interval, it is determined to be a continuous abnormal condition, triggering an alarm and maintaining the transient mode.

[0007] Further, calculating the frequency deviation and determining whether the frequency deviation exceeds the dead zone includes: Real-time calculation of the frequency deviation between the grid connection point frequency and the rated frequency; Pre-set dead zone threshold, small frequency difference threshold, and mid-frequency difference threshold; If the absolute value of the frequency difference is not greater than the dead zone threshold, then the frequency difference is determined to be within the dead zone, and no frequency modulation is triggered. If the absolute value of the frequency difference is greater than the dead zone threshold and not greater than the small frequency difference threshold, then the frequency difference is determined to be in the first frequency difference interval. If the absolute value of the frequency difference is greater than the small frequency difference threshold but not greater than the medium frequency difference threshold, then the frequency difference is determined to be within the standard frequency difference range. If the absolute value of the frequency difference is greater than the mid-frequency difference threshold, then the frequency difference is determined to be within the second frequency difference range.

[0008] Further, the droop characteristic mode is adaptively switched according to the frequency deviation and irradiance level to obtain the first power target value, including: When the frequency deviation is within the standard frequency deviation range, the droop characteristic shape is set as a standard droop curve, and the basic frequency modulation power is generated based on the product of the standard droop rate, the frequency deviation, and the rated power. When the frequency deviation is within the first frequency deviation range, the droop characteristic shape is set as a concave curve, the gain factor of the concave curve is determined, and the basic frequency modulation power is generated by combining the standard linear calculation value. When the frequency deviation is within the second frequency difference range, the droop characteristic shape is set as a convex curve, the attenuation factor of the convex curve is determined, and the basic frequency modulation power is generated by combining the standard linear extrapolation value. Simultaneously collect irradiance data of photovoltaic power stations, calculate the ratio of the current average irradiance of the entire station to the rated irradiance, determine the current irradiance level based on the ratio, and determine the corresponding correction coefficient; The corrected frequency modulation power is obtained based on the base frequency modulation power and the correction coefficient, and combined with the initial power at the start of frequency modulation, the first power target value is obtained.

[0009] Furthermore, when the frequency deviation is within the first frequency difference range, the relative position coefficient of the frequency deviation is calculated, and the relative position coefficient of the frequency deviation is the ratio of the frequency deviation to the small frequency difference threshold. The gain factor is obtained by multiplying the sensitivity gain coefficient and the frequency deviation relative position coefficient, wherein the sensitivity gain coefficient is a preset constant; When the frequency deviation is within the second frequency deviation range, the frequency deviation excess coefficient is calculated. The frequency deviation excess coefficient is the ratio of the portion of the frequency deviation that exceeds the intermediate frequency difference threshold to the maximum frequency deviation limit. The attenuation factor is obtained by multiplying the saturation attenuation coefficient and the frequency deviation excess coefficient, wherein the saturation attenuation coefficient is a preset constant.

[0010] Furthermore, it also includes performing a boundary continuity check on the first power target value when switching between frequency difference intervals. The check process includes: If the current control cycle is at the boundary of the frequency difference interval, the power target value of the previous control cycle is called, and the difference between the current first power target value and the power target value of the previous control cycle is calculated. If the difference is greater than the preset boundary switching judgment limit, the current first power target value is set to the sum of the power target value of the previous control cycle and the boundary switching step size. If the difference is not greater than the preset boundary switching judgment threshold, the current first power target value is not adjusted.

[0011] Further, based on the frequency operating state, the first power target value and the AGC command are dynamically coordinated to determine the second power target value, including: Determine the current frequency operating status, which includes normal status, cooperative status, priority status, and recovery status; Synchronously acquire AGC instructions and parse the current target value, change direction, and change rate of the AGC instructions; If the current frequency operation status is normal, the current target value of the AGC command is set to the second power target value; If the current frequency operating state is a cooperative state, the second power target value is determined based on the frequency modulation direction corresponding to the first power target value, the change direction, and the change rate; If the current frequency operating state is the priority state, the second power target value is determined according to the frequency modulation direction corresponding to the first power target value and the change direction; If the current frequency operation state is in the recovery state, a primary frequency adjustment margin is generated, and the second power target value is obtained by adding the primary frequency adjustment margin and the current target value of the AGC instruction.

[0012] Furthermore, frequency modulation commands for each inverter are generated based on the response characteristic profiles of each inverter and the second power target value, including: The total field adjustment and frequency modulation direction are generated based on the second power target value; The response characteristics profile of each inverter includes the response lag time, maximum power point tracking efficiency, and health status score of each inverter. The regulation of each inverter is generated based on the total regulation, the response lag time, the maximum power point tracking efficiency, and the health status score. The adjustment amount of each inverter is constrained and tested. If the test passes, the final active power target value of each inverter is generated as the frequency regulation command, based on the current actual output of each inverter.

[0013] Furthermore, the regulation of each inverter is generated based on the total regulation, the response lag time, the maximum power point tracking efficiency, and the health status score, including: The reciprocal of the response lag time is used as the allocation weighting factor for each inverter; The total field regulation is initially allocated according to the allocation weight factor ratio to obtain the first regulation of each inverter; The first adjustment amount is corrected based on the current frequency modulation direction and the maximum power point tracking efficiency of each inverter to obtain the second adjustment amount of each inverter. Based on the health status score, the regulation limit of each inverter is generated, and the compensation amount between the regulation limit and the second regulation amount is calculated. The compensation amount is redistributed according to the health weight ratio of inverters whose health status score is greater than the preset threshold score, and the second adjustment amount of the corresponding inverter is added to obtain the final adjustment amount of each inverter.

[0014] On the other hand, the present invention also provides a primary frequency regulation droop characteristic control system for photovoltaic power plants, comprising: The acquisition module is used to acquire the grid connection point frequency in real time, synchronously acquire voltage and current signals, and extract multi-dimensional features. The determination module is used to output the modality determination result of the multidimensional features based on the transient feature fingerprint database, and the modality determination result includes transient modes and steady-state modes; The first analysis module is used to lock the primary frequency modulation if it is a transient mode, and to calculate the frequency deviation and determine whether the frequency deviation exceeds the dead zone if it is a steady mode. If so, it adaptively switches the droop characteristic mode according to the frequency deviation and the irradiance level, and obtains the first power target value. The second analysis module is used to determine the current frequency operating status, and dynamically coordinate the first power target value and AGC instructions according to the frequency operating status to determine the second power target value. The control module is used to generate response characteristic profiles for each inverter and generate frequency modulation commands for each inverter based on the response characteristic profiles and the second power target value.

[0015] The method and system for controlling the primary frequency regulation droop characteristics of a photovoltaic power station according to embodiments of this application have the following advantages compared with the prior art: By extracting multidimensional features, transient and steady-state operating conditions can be accurately distinguished, avoiding malfunctions in frequency regulation during the next transient process such as short circuits; By adaptively switching the droop characteristics under different frequency difference ranges and different irradiance, the sensitivity under small frequency difference and the saturation suppression under large frequency difference are taken into account, thereby improving the stability of frequency modulation control. By dynamically coordinating the first power target value and AGC commands in conjunction with the frequency operating status, the AGC adjustment requirements and the priority of primary frequency regulation are taken into account, thus avoiding secondary frequency fluctuations. By profiling the inverter response characteristics and combining response lag time, maximum power point tracking efficiency, and health status to allocate regulation in a hierarchical manner, the system makes full use of inverter resources with fast response and good operating status, thereby improving the overall frequency regulation response speed of the entire station and effectively improving the primary frequency regulation performance of the photovoltaic power station. Attached Figure Description

[0016] Figure 1 This is a flowchart illustrating a method for controlling the primary frequency regulation droop characteristics of a photovoltaic power station according to an embodiment of this application. Figure 2 This is a schematic diagram of a primary frequency regulation droop characteristic control system for a photovoltaic power station provided in an embodiment of this application; Figure 3 This is a schematic diagram of the structure of the electronic device provided in the embodiments of this application. Detailed Implementation

[0017] The specific embodiments of this application will be described in further detail below with reference to the accompanying drawings and examples. The following examples are used to illustrate this application, but are not intended to limit the scope of this application.

[0018] In the description of this application, it should be understood that the terms "center", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0019] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, unless otherwise stated, "a plurality of" means two or more.

[0020] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0021] like Figure 1 As shown in the embodiment of this application, a method for controlling the primary frequency regulation droop characteristic of a photovoltaic power station includes: S101: Real-time acquisition of grid connection point frequency, synchronous acquisition of voltage and current signals, and extraction of multi-dimensional features; S102: Output the modality determination result of the multidimensional features based on the transient feature fingerprint database, the modality determination result including transient modes and steady-state modes; Specifically, the transient characteristic fingerprint database is trained and constructed based on a large amount of historical short-circuit disturbance, voltage fluctuation, load switching and other abnormal operating conditions data. It can cover the characteristic thresholds of various transient events commonly seen at the grid connection point of photovoltaic power plants, effectively distinguish between transient processes and steady-state frequency deviations, avoid malfunctions of primary frequency regulation during transient processes, and improve the robustness of control logic.

[0022] In a specific implementation process, the modality determination result of the multidimensional features is output based on the transient feature fingerprint database, including the following steps: The multidimensional features include voltage amplitude mutation rate, frequency change rate, harmonic distortion rate, and three-phase imbalance. The relative rate of change of the voltage amplitude in the current sampling period with that in the previous sampling period is calculated as the voltage amplitude mutation rate. The rate of change of the frequency measurement value in the current sampling period with that in the previous sampling period is calculated as the frequency change rate. Harmonic analysis is performed on the instantaneous voltage value to calculate the total harmonic distortion rate and the content rate of the main subharmonics as the harmonic distortion rate. The ratio of the negative sequence voltage component to the positive sequence voltage component is calculated based on the symmetrical component method as the three-phase unbalance. A1: Compare the multidimensional features with the preset transient judgment thresholds in the transient feature fingerprint database, and count the number of features that exceed the thresholds; Among them, the transient judgment threshold refers to the critical value pre-set for different features in the transient feature fingerprint database, which is used to distinguish between normal steady-state operation and transient disturbance process. Each feature corresponds to an independent judgment threshold, which can be adapted to the feature fluctuation characteristics under different operating conditions.

[0023] A2: If the number of features is less than the preset number, it is determined to be a steady-state mode. In this application, the preset number is 3. If the number of features is not less than the preset number, the initial transient flag and the fault duration timer are triggered to obtain the fault duration of the initial transient flag. A3: When the duration of the fault is within the preset short-circuit fault time window interval, it is determined that the transient mode has been entered. If it is lower than the lower limit of the time window interval, the initial transient flag is cleared and the steady-state mode is maintained. If it exceeds the upper limit of the time window interval, it is determined to be a continuous abnormal condition, triggering an alarm and maintaining the transient mode.

[0024] Specifically, the preset short-circuit fault time window interval refers to the typical time range from fault clearing to reclosing or successful fault isolation after a short-circuit fault occurs in the power grid. The endpoints of the interval can be preset according to the voltage level of the power grid connected to the station and the protection action setting value of the area, or can be adjusted and updated online according to the actual operating conditions.

[0025] In the transient mode, the system also includes continuous monitoring of the real-time values ​​of multi-dimensional features. When all features recover to within their respective normal range thresholds, a recovery confirmation timer is started. If the duration of the recovery confirmation timer is greater than the recovery confirmation delay, the transient process is determined to have ended, and an unlock signal is output. If any feature exceeds the limit again, the recovery confirmation timer is reset, and the transient locking state is maintained.

[0026] Understandably, by comprehensively judging transient modes through multi-dimensional features, compared with judging by a single feature, false positives and false negatives can be reduced. Combining the fault duration window to further confirm the transient process can effectively avoid a single frequency adjustment malfunction during the transient process. At the same time, setting a recovery confirmation delay after the transient mode ends can prevent premature unlocking before the transient process is completely over, further improving the reliability of the control logic.

[0027] S103: If it is a transient mode, block the first frequency modulation; S104: If it is a steady-state mode, calculate the frequency deviation and determine whether the frequency deviation exceeds the dead zone; In a specific implementation process, calculating the frequency deviation and determining whether the frequency deviation exceeds the dead zone includes the following steps: B1: Real-time calculation of the frequency deviation between the grid connection point frequency and the rated frequency; B2: Pre-set dead zone threshold, small frequency difference threshold, and mid-frequency difference threshold; Among them, the dead zone threshold is ±0.03Hz, and the small frequency difference threshold, medium frequency difference threshold, and maximum frequency deviation limit are all preset according to the grid frequency regulation requirements and the actual operating capacity of the photovoltaic power station.

[0028] B3: If the absolute value of the frequency difference is not greater than the dead zone threshold, then the frequency difference is determined to be within the dead zone, and no frequency modulation is triggered; if the absolute value of the frequency difference is greater than the dead zone threshold but not greater than the small frequency difference threshold, then the frequency difference is determined to be within the first frequency difference interval; if the absolute value of the frequency difference is greater than the small frequency difference threshold but not greater than the intermediate frequency difference threshold, then the frequency difference is determined to be within the standard frequency difference interval; if the absolute value of the frequency difference is greater than the intermediate frequency difference threshold, then the frequency difference is determined to be within the second frequency difference interval.

[0029] Specifically, the first frequency deviation range refers to the range where the frequency deviation just exceeds the dead zone but has not reached a large deviation level. At this time, it is necessary to improve the response sensitivity of primary frequency regulation so that the photovoltaic power station can quickly output regulation power to help the grid frequency recover smoothly and avoid further expansion of the deviation. The second frequency deviation range refers to the range where the frequency deviation has reached a large level and is close to the maximum adjustable capacity boundary of the photovoltaic power station. At this time, it is necessary to saturate and suppress the regulation power to prevent the photovoltaic power station from excessively participating in frequency regulation and exhausting its own reserve capacity, while also preventing regulation overshoot from causing new frequency fluctuations. The standard frequency deviation range uses a fixed droop coefficient to calculate the power target value, which meets the conventional requirements of the grid for the droop characteristics of primary frequency regulation.

[0030] Understandably, determining the frequency difference range lays the foundation for adjusting the overall gain of the droop characteristics in conjunction with the current irradiance level of the photovoltaic power station, ultimately yielding the first power target value.

[0031] S105: If so, the droop characteristic mode is adaptively switched according to the frequency deviation and irradiance level, and a first power target value is obtained; In a specific implementation process, the droop characteristic mode is adaptively switched according to the frequency deviation and irradiance level to obtain the first power target value, including the following cases: The first scenario: When the frequency deviation is within the standard frequency deviation range, the droop characteristic shape is set as a standard droop curve, and the basic frequency modulation power is generated based on the product of the standard droop rate, the frequency deviation, and the rated power. The second scenario: When the frequency deviation is within the first frequency difference range, the droop characteristic shape is set as a concave curve, the gain factor of the concave curve is determined, and the basic frequency modulation power is generated by combining the standard linear calculation value. Specifically, the gain factor enables the power adjustment to achieve maximum sensitivity gain at the dead zone boundary and decreases as the frequency deviation increases.

[0032] Specifically, the standard linear calculation value = the basic power adjustment amount of traditional primary frequency modulation (difference rate × frequency deviation × rated power), and the standard linear extrapolation value = "extending" the standard straight line of the second frequency difference interval to the large frequency difference position to calculate how much power should be theoretically generated, which serves as the attenuation benchmark for convex saturation constraints.

[0033] Wherein, when the frequency deviation is within the first frequency difference interval, the frequency deviation relative position coefficient is calculated, and the frequency deviation relative position coefficient is the ratio of the frequency deviation to the small frequency difference threshold; The gain factor is obtained by multiplying the sensitivity gain coefficient and the frequency deviation relative position coefficient, wherein the sensitivity gain coefficient is a preset constant; Specifically, the sensitivity gain coefficient represents the maximum sensitivity increase at the dead zone boundary, and the frequency deviation relative position coefficient decreases linearly as the ratio increases, so that the closer the frequency deviation is to the dead zone boundary, the larger the gain factor is, and the closer the frequency deviation is to the small frequency difference threshold, the smaller the gain factor is.

[0034] The third case: When the frequency deviation is in the second frequency difference range, the droop characteristic shape is set as a convex curve, the attenuation factor of the convex curve is determined, and the basic frequency modulation power is generated by combining the standard linear extrapolation value. Specifically, the attenuation factor causes the growth rate of the power regulation to decrease as the frequency deviation increases, gradually approaching the limiting value; When the frequency deviation is within the second frequency difference range, the frequency deviation excess coefficient is calculated. The frequency deviation excess coefficient is the ratio of the portion of the frequency deviation that exceeds the intermediate frequency difference threshold to the maximum frequency deviation limit. The attenuation factor is obtained by multiplying the saturation attenuation coefficient and the frequency deviation excess coefficient, wherein the saturation attenuation coefficient is a preset constant.

[0035] Specifically, the saturation attenuation coefficient characterizes the maximum attenuation amplitude in the large frequency difference range. The frequency deviation excess coefficient increases linearly with the increase of the ratio, so that the closer the frequency deviation is to the mid-frequency difference threshold, the smaller the attenuation factor, and the closer the frequency deviation is to the maximum frequency deviation limit, the larger the attenuation factor.

[0036] Simultaneously collect irradiance data of photovoltaic power stations, calculate the ratio of the current average irradiance of the entire station to the rated irradiance, determine the current irradiance level based on the ratio, and determine the corresponding correction coefficient; Specifically, the irradiance levels include low, medium, and high levels. If the ratio is not lower than the high irradiance threshold, it is determined to be a high irradiance level, and the correction coefficient is 1.0; if the ratio is between the low irradiance threshold and the high irradiance threshold, it is determined to be a medium irradiance level, and the correction coefficient is 0.85; if the ratio is lower than the low irradiance threshold, it is determined to be a low irradiance level, and the correction coefficient is 0.70.

[0037] The corrected frequency modulation power is obtained based on the base frequency modulation power and the correction coefficient, and combined with the initial power at the start of frequency modulation, the first power target value is obtained.

[0038] Understandably, by adaptively adjusting the shape of the droop characteristic within the frequency deviation range, the response sensitivity under the first frequency deviation is ensured, preventing the long-term accumulation of small frequency offsets from causing larger frequency deviations. At the same time, the frequency modulation depth is limited under the second frequency deviation scenario, preventing overmodulation from causing the photovoltaic power station to exceed its output limit and ensuring the safe operation of the power station itself. Combined with the irradiance level to correct the frequency modulation power, it can adapt to the adjustable margin under different output scenarios of the photovoltaic power station and improve the rationality of the primary frequency modulation action.

[0039] After obtaining the first power target value, the method further includes performing a boundary continuity check on the first power target value during frequency difference interval switching. The check process includes: C1: If the current control cycle is at the boundary of the frequency difference interval, then call the power target value of the previous control cycle and calculate the difference between the current first power target value and the power target value of the previous control cycle. C2: If the difference is greater than the preset boundary switching judgment limit, the current first power target value is set to the sum of the power target value of the previous control cycle and the boundary switching step size. If the difference is not greater than the preset boundary switching judgment threshold, the current first power target value is not adjusted.

[0040] Among them, the preset boundary switching judgment threshold is the criterion for judging whether the power target value needs to be smoothed when switching between different frequency difference intervals. When the power step generated by the switching between two adjacent intervals exceeds the threshold, the power target value needs to be limited and smoothed to avoid the output fluctuation of the photovoltaic power station caused by the sudden change of the target power.

[0041] Specifically, the boundary switching step size refers to the smaller of the boundary switching rate limit and the maximum allowable power change rate of the device. The boundary switching rate limit is dynamically determined based on the direction of change of the current frequency deviation: when the frequency deviation switches from the dead zone to the first frequency deviation interval, the boundary switching rate limit takes the first limit, which corresponds to the tangent slope of the concave curve at the dead zone boundary; when the frequency deviation switches from the first frequency deviation interval to the standard frequency deviation interval, the boundary switching rate limit takes the second limit, which corresponds to the constant slope of the standard drooping curve; when the frequency deviation switches from the standard frequency deviation interval to the second frequency deviation interval, the boundary switching rate limit takes the third limit, which corresponds to the tangent slope of the convex curve at the intermediate frequency deviation threshold.

[0042] Understandably, by switching the boundary step size as described above, it is ensured that when crossing the boundary of the interval in any direction, the rate of change of the power target value matches the initial slope of the target interval, thus achieving a seamless and smooth transition.

[0043] S106: Determine the current frequency operating status, and dynamically coordinate the first power target value and AGC command according to the frequency operating status to determine the second power target value; In a specific implementation process, the second power target value is determined by dynamically coordinating the first power target value and AGC instructions based on the frequency operating state, including the following steps: D1: Determine the current frequency operating status, which includes normal status, cooperative status, priority status, and recovery status; D2: Synchronously acquire AGC instructions, and parse the current target value, change direction, and change rate of the AGC instructions; D3: If the current frequency operation status is normal, set the current target value of the AGC instruction to the second power target value; If the current frequency operating state is a cooperative state, the second power target value is determined based on the frequency modulation direction corresponding to the first power target value, the change direction, and the change rate; In the coordinated state, it is determined whether the frequency modulation direction corresponding to the first power target value is in the same direction as the change direction of the AGC command. If they are in the same direction, the first power target value and the current target value of the AGC command are dynamically weighted and summed to obtain the second power target value. If they are not in the same direction, it is determined whether the rate of change is greater than a preset threshold. If it is greater than the preset threshold, the first adjustment amount of the first power target value relative to the initial power and the second adjustment amount of the current target value of the AGC command relative to the initial power are calculated based on the initial power at the start of frequency modulation. The first adjustment amount and the second adjustment amount are algebraically superimposed to obtain the joint adjustment amount. It is determined whether the absolute value of the joint adjustment amount exceeds a preset superposition limit value. If it does not exceed the limit value, the initial power is superimposed with the joint adjustment amount to obtain the second power target value. If it exceeds the limit value, the initial power is superimposed with a limit adjustment amount with the same sign as the joint adjustment amount to obtain the second power target value. If it is not greater than the preset threshold value, the first power target value is set as the second power target value.

[0044] The preset threshold for the rate of change refers to the maximum output change allowed per unit time of the AGC command. It is the critical value that distinguishes between normal slow adjustment and emergency large-scale adjustment of AGC. When the rate of change of the AGC command does not exceed this threshold, it indicates that the AGC adjustment demand is gentle. Priority is given to ensuring the adjustment output of the primary frequency regulation to avoid conflict between two opposing adjustment processes and affect the recovery of the power grid frequency.

[0045] Specifically, the dynamic weight is adaptively adjusted according to the magnitude of the frequency deviation. The closer the frequency deviation is to the dead zone threshold, the greater the weight of the AGC instruction; conversely, the greater the weight of the first power target value. Limiting adjustment amount refers to the adjustment amount that is in the same direction as the joint adjustment amount and is equal in size to the preset superimposed limit value. This avoids the total adjustment amount obtained when the two adjustment directions are opposite, which exceeds the maximum output variation range that the photovoltaic power station can withstand, and ensures stable power output of the power station.

[0046] If the current frequency operating state is the priority state, the second power target value is determined according to the frequency modulation direction corresponding to the first power target value and the change direction; In the priority state, the frequency regulation direction corresponding to the first power target value is compared with the AGC command change direction. If they are opposite, the AGC command is completely blocked and the second power target value is equal to the first power target value. If they are in the same direction, the second power target value is equal to the first power target value plus the AGC command increment after being reduced by the proportional reduction coefficient. The proportional reduction coefficient is adaptively adjusted according to the frequency deviation. The closer the frequency deviation is to the preset threshold corresponding to the priority state, the smaller the participation ratio of the AGC command. The value range of the proportional reduction coefficient is 0-1 to ensure that the primary frequency regulation needs are prioritized under large frequency differences and to avoid AGC regulation interfering with the primary frequency regulation action. The preset threshold corresponding to the priority state refers to the lowest absolute value of frequency deviation that triggers the primary frequency regulation priority control in the power grid dispatch regulations. The preset threshold corresponding to the priority state refers to the minimum absolute value of the frequency deviation that triggers the primary frequency regulation priority control mode. When the absolute value of the frequency deviation at the grid connection point of the photovoltaic power station reaches or exceeds this threshold, it indicates that the grid frequency deviation has reached a serious level, and it is necessary to prioritize the regulation resources of primary frequency regulation and reduce the interference of AGC regulation on the primary frequency regulation action.

[0047] If the current frequency operation state is in recovery state, a primary frequency modulation margin is generated, and a second power target value is obtained by adding the primary frequency modulation margin and the current target value of the AGC instruction.

[0048] When in the recovery state, the primary frequency modulation needs to be gradually withdrawn. The primary frequency modulation margin begins to decay from the frequency modulation adjustment amount at the moment of entering the recovery state. The decay time constant is adaptively adjusted according to the frequency recovery speed. The faster the frequency recovery, the smaller the decay time constant, and the slower the frequency recovery, the larger the decay time constant. The value range of the decay time constant is 3-8 seconds.

[0049] Understandably, by coordinating primary frequency regulation and AGC control according to different frequency operation scenarios, the priority of primary frequency regulation under large frequency difference disturbances is guaranteed, and conflicts between different control commands are avoided. At the same time, AGC control can be smoothly connected during the frequency recovery process, so as to achieve shock-free exit of primary frequency regulation and improve the coordination of photovoltaic power plants in the multi-level control of the power grid.

[0050] S107: Generate response characteristic profiles for each inverter, and generate frequency modulation commands for each inverter based on the response characteristic profiles of each inverter and the second power target value.

[0051] After generating the frequency modulation command for each inverter, the process also includes closed-loop feedback dynamic correction, which specifically includes: collecting the actual output power of the entire station and calculating the deviation from the second power target value; dynamically adjusting the correction parameters according to the current frequency modulation stage: focusing on fast tracking in the response stage, focusing on stable convergence in the adjustment stage, and focusing on eliminating steady-state error in the stabilization stage; and returning the corrected power target value to step S101 to form closed-loop control.

[0052] In a specific implementation process, frequency modulation commands for each inverter are generated based on the response characteristic profiles of each inverter and the second power target value, including the following steps: The response characteristics profile of each inverter includes the response lag time, maximum power point tracking efficiency, and health status score of each inverter. Response lag time refers to the time interval from receiving a power command to the start of actual power output change; maximum power point tracking efficiency refers to the MPPT efficiency under current irradiance and temperature conditions; health status score is a score that comprehensively considers years of operation, fault history, operating temperature, and the degree of aging of power devices. D1: Generate the total field adjustment and frequency modulation direction based on the second power target value; D2: Generate the regulation of each inverter based on the total regulation, the response lag time, the maximum power point tracking efficiency, and the health status score. This includes the following steps. D21: Use the reciprocal of the response lag time as the allocation weighting factor for each inverter; D22: The total regulation of the entire field is initially allocated according to the allocation weight factor ratio to obtain the first regulation of each inverter; D23: Based on the current frequency modulation direction and the maximum power point tracking efficiency of each inverter, the first adjustment amount is corrected to obtain the second adjustment amount of each inverter; D24: Generate the regulation limit for each inverter based on the health status score, and calculate the compensation between the regulation limit and the second regulation; Specifically, the allocated regulation amount of inverters with health status scores lower than the preset threshold score is reduced by the health derating ratio to obtain the regulation limitation amount. The compensation amount = the first regulation amount minus the regulation limitation amount, thereby ensuring that inverters with poor health status reduce their frequency regulation participation depth and reduce operational risks. At the same time, the reduced regulation amount is transferred to inverters with good health status and fast response speed to ensure that the total frequency regulation amount of the whole field meets the requirements and improves the overall primary frequency regulation response quality. The preset threshold score is set to 60 points, and the health derating ratio is (preset threshold score - actual score) / preset threshold score, that is, the lower the score, the lower the allowed regulation depth ratio.

[0053] D25: The compensation amount is redistributed according to the health weight ratio of inverters whose health status score is greater than the preset threshold score, and the second adjustment amount of the corresponding inverter is added to obtain the final adjustment amount of each inverter.

[0054] The health weight ratio is the ratio of the health status score of each health inverter to the sum of the health status scores of all health inverters.

[0055] Specifically, redistribution refers to splitting the compensation amount according to the health weight ratio of each healthy inverter and adding it to the second regulation amount of the corresponding healthy inverter. The inverter with the higher health status score is allocated more compensation regulation amount, making full use of the regulation potential of healthy inverters, ensuring that the total regulation amount of the whole field meets the target requirements, while reducing the regulation burden of abnormal equipment in a differentiated manner, taking into account both the overall response effect and the safety of equipment operation.

[0056] D3: Perform constraint verification on the adjustment amount of each inverter. If the verification passes, combine the current actual output of each inverter to generate the final active power target value of each inverter as the frequency regulation command.

[0057] Understandably, by allocating frequency regulation adjustments in a differentiated manner, the regulation potential of each inverter can be fully utilized. Under the premise of ensuring the safe operation of the equipment, the overall primary frequency regulation response speed and accuracy of the photovoltaic power station can be improved, and the frequency regulation progress of the entire plant can be avoided due to the delayed response or poor health of some inverters.

[0058] Figure 2 This invention provides a primary frequency regulation droop characteristic control system for a photovoltaic power station, such as... Figure 2 As shown, the system includes: The acquisition module 201 is used to acquire the grid connection point frequency in real time, synchronously acquire voltage and current signals, and extract multi-dimensional features. The determination module 202 is used to output the modality determination result of the multidimensional features based on the transient feature fingerprint database, wherein the modality determination result includes transient modes and steady-state modes; The first analysis module 203 is used to block the primary frequency modulation if it is a transient mode, and to calculate the frequency deviation and determine whether the frequency deviation exceeds the dead zone if it is a steady mode. If so, it adaptively switches the droop characteristic mode according to the frequency deviation and the irradiance level, and obtains the first power target value. The second analysis module 204 is used to determine the current frequency operating status, and dynamically coordinate the first power target value and AGC command according to the frequency operating status to determine the second power target value. The control module 205 is used to generate response characteristic profiles of each inverter and generate frequency modulation commands for each inverter based on the response characteristic profiles of each inverter and the second power target value.

[0059] Figure 3 This is a schematic diagram of the structure of an electronic device provided in an embodiment of the present invention. The electronic device may include: a processor 310, a communication interface 320, a memory 330, and a communication bus 340. The processor 310, communication interface 320, and memory 330 communicate with each other via the communication bus 340. The processor 310 can call logic instructions stored in the memory 330 to execute a method for controlling the primary frequency regulation droop characteristics of a photovoltaic power station.

[0060] Furthermore, the logical instructions in the aforementioned memory 330 can be implemented as software functional units and, when sold or used as independent products, can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art, or a part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of the present invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0061] The above description is only a preferred embodiment of this application. It should be noted that for those skilled in the art, several improvements and substitutions can be made without departing from the technical principles of this application, and these improvements and substitutions should also be considered within the scope of protection of this application.

Claims

1. A method for controlling droop characteristics of primary frequency modulation of a photovoltaic power station, characterized in that, include: Real-time acquisition of grid connection point frequency, synchronous acquisition of voltage and current signals, and extraction of multi-dimensional features; Based on the transient feature fingerprint database, the modality determination result of the multidimensional features is output, and the modality determination result includes transient modes and steady-state modes; If it is a transient mode, the first frequency modulation is blocked. If it is a steady-state mode, the frequency deviation is calculated and it is determined whether the frequency deviation exceeds the dead zone. If so, the droop characteristic mode is adaptively switched according to the frequency deviation and the irradiance level to obtain the first power target value. Determine the current frequency operating status, and dynamically coordinate the first power target value and AGC instructions based on the frequency operating status to determine the second power target value; Generate response characteristic profiles for each inverter, and generate frequency modulation commands for each inverter based on the response characteristic profiles and the second power target value.

2. The photovoltaic power plant primary frequency modulation droop characteristic control method according to claim 1, characterized in that, Based on the transient feature fingerprint database, the modality determination result of the multidimensional features is output, including: The multidimensional features include voltage amplitude abrupt change rate, frequency change rate, harmonic distortion rate, and three-phase imbalance. The multidimensional features are compared with the pre-set transient judgment thresholds in the transient feature fingerprint database, and the number of features exceeding the thresholds is counted. If the number of features is less than the preset number, it is determined to be a steady-state mode; If the number of features is not less than the preset number, the initial transient flag and fault duration timing are triggered to obtain the fault duration of the initial transient flag; If the duration of the fault is within the preset short-circuit fault time window interval, it is determined that the transient mode has been entered. If it is lower than the lower limit of the time window interval, the initial transient flag is cleared and the steady-state mode is maintained. If it exceeds the upper limit of the time window interval, it is determined to be a continuous abnormal condition, triggering an alarm and maintaining the transient mode.

3. The method for controlling the primary frequency regulation droop characteristic of a photovoltaic power station as described in claim 1, characterized in that, Calculating the frequency deviation and determining whether the frequency deviation exceeds the dead zone includes: Real-time calculation of the frequency deviation between the grid connection point frequency and the rated frequency; Pre-set dead zone threshold, small frequency difference threshold, and mid-frequency difference threshold; If the absolute value of the frequency difference is not greater than the dead zone threshold, then the frequency difference is determined to be within the dead zone, and no frequency modulation is triggered. If the absolute value of the frequency difference is greater than the dead zone threshold and not greater than the small frequency difference threshold, then the frequency difference is determined to be in the first frequency difference interval. If the absolute value of the frequency difference is greater than the small frequency difference threshold but not greater than the medium frequency difference threshold, then the frequency difference is determined to be within the standard frequency difference range. If the absolute value of the frequency difference is greater than the mid-frequency difference threshold, then the frequency difference is determined to be within the second frequency difference range.

4. The method for controlling the primary frequency regulation droop characteristic of a photovoltaic power station as described in claim 3, characterized in that, Based on the frequency deviation and irradiance level, the droop characteristic mode is adaptively switched to obtain the first power target value, including: When the frequency deviation is within the standard frequency deviation range, the droop characteristic shape is set as a standard droop curve, and the basic frequency modulation power is generated based on the product of the standard droop rate, the frequency deviation, and the rated power. When the frequency deviation is within the first frequency deviation range, the droop characteristic shape is set as a concave curve, the gain factor of the concave curve is determined, and the basic frequency modulation power is generated by combining the standard linear calculation value. When the frequency deviation is within the second frequency difference range, the droop characteristic shape is set as a convex curve, the attenuation factor of the convex curve is determined, and the basic frequency modulation power is generated by combining the standard linear extrapolation value. Simultaneously collect irradiance data of photovoltaic power stations, calculate the ratio of the current average irradiance of the entire station to the rated irradiance, determine the current irradiance level based on the ratio, and determine the corresponding correction coefficient; The corrected frequency modulation power is obtained based on the base frequency modulation power and the correction coefficient, and combined with the initial power at the start of frequency modulation, the first power target value is obtained.

5. The method for controlling the primary frequency regulation droop characteristic of a photovoltaic power station as described in claim 4, characterized in that, When the frequency deviation is within the first frequency difference range, the relative position coefficient of the frequency deviation is calculated, and the relative position coefficient of the frequency deviation is the ratio of the frequency deviation to the small frequency difference threshold. The gain factor is obtained by multiplying the sensitivity gain coefficient and the frequency deviation relative position coefficient, wherein the sensitivity gain coefficient is a preset constant; When the frequency deviation is within the second frequency deviation range, the frequency deviation excess coefficient is calculated. The frequency deviation excess coefficient is the ratio of the portion of the frequency deviation that exceeds the intermediate frequency difference threshold to the maximum frequency deviation limit. The attenuation factor is obtained by multiplying the saturation attenuation coefficient and the frequency deviation excess coefficient, wherein the saturation attenuation coefficient is a preset constant.

6. The method for controlling the primary frequency regulation droop characteristic of a photovoltaic power station as described in claim 4, characterized in that, It also includes performing a boundary continuity check on the first power target value when switching between frequency difference intervals. The check process includes: If the current control cycle is at the boundary of the frequency difference interval, the power target value of the previous control cycle is called, and the difference between the current first power target value and the power target value of the previous control cycle is calculated. If the difference is greater than the preset boundary switching judgment limit, the current first power target value is set to the sum of the power target value of the previous control cycle and the boundary switching step size. If the difference is not greater than the preset boundary switching judgment threshold, the current first power target value is not adjusted.

7. The method for controlling the primary frequency regulation droop characteristic of a photovoltaic power station as described in claim 1, characterized in that, Based on the frequency operating status, the first power target value and AGC instructions are dynamically coordinated to determine the second power target value, including: Determine the current frequency operating status, which includes normal status, cooperative status, priority status, and recovery status; Synchronously acquire AGC instructions and parse the current target value, change direction, and change rate of the AGC instructions; If the current frequency operation status is normal, the current target value of the AGC command is set to the second power target value; If the current frequency operating state is a cooperative state, the second power target value is determined based on the frequency modulation direction corresponding to the first power target value, the change direction, and the change rate; If the current frequency operating state is the priority state, the second power target value is determined according to the frequency modulation direction corresponding to the first power target value and the change direction; If the current frequency operation state is in the recovery state, a primary frequency adjustment margin is generated, and the second power target value is obtained by adding the primary frequency adjustment margin and the current target value of the AGC instruction.

8. The method for controlling the primary frequency regulation droop characteristic of a photovoltaic power station as described in claim 1, characterized in that, Based on the response characteristic profiles of each inverter and the second power target value, frequency modulation commands are generated for each inverter, including: The total field adjustment and frequency modulation direction are generated based on the second power target value; The response characteristics profile of each inverter includes the response lag time, maximum power point tracking efficiency, and health status score of each inverter. The regulation of each inverter is generated based on the total regulation, the response lag time, the maximum power point tracking efficiency, and the health status score. The adjustment amount of each inverter is constrained and tested. If the test passes, the final active power target value of each inverter is generated as the frequency regulation command, based on the current actual output of each inverter.

9. The method for controlling the primary frequency regulation droop characteristic of a photovoltaic power station as described in claim 8, characterized in that, The regulation of each inverter is generated based on the total regulation, the response lag time, the maximum power point tracking efficiency, and the health status score, including: The reciprocal of the response lag time is used as the allocation weighting factor for each inverter; The total field regulation is initially allocated according to the allocation weight factor ratio to obtain the first regulation of each inverter; The first adjustment amount is corrected based on the current frequency modulation direction and the maximum power point tracking efficiency of each inverter to obtain the second adjustment amount of each inverter. Based on the health status score, the regulation limit of each inverter is generated, and the compensation amount between the regulation limit and the second regulation amount is calculated. The compensation amount is redistributed according to the health weight ratio of inverters whose health status score is greater than the preset threshold score, and the second adjustment amount of the corresponding inverter is added to obtain the final adjustment amount of each inverter.

10. A primary frequency regulation droop characteristic control system for a photovoltaic power station, characterized in that, include: The acquisition module is used to acquire the grid connection point frequency in real time, synchronously acquire voltage and current signals, and extract multi-dimensional features. The determination module is used to output the modality determination result of the multidimensional features based on the transient feature fingerprint database, and the modality determination result includes transient modes and steady-state modes; The first analysis module is used to lock the primary frequency modulation if it is a transient mode, and to calculate the frequency deviation and determine whether the frequency deviation exceeds the dead zone if it is a steady mode. If so, it adaptively switches the droop characteristic mode according to the frequency deviation and the irradiance level, and obtains the first power target value. The second analysis module is used to determine the current frequency operating status, and dynamically coordinate the first power target value and AGC instructions according to the frequency operating status to determine the second power target value. The control module is used to generate response characteristic profiles for each inverter and generate frequency modulation commands for each inverter based on the response characteristic profiles and the second power target value.

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