Reactive power compensation method and device based on photovoltaic inverter

Abstract

This invention relates to the field of power grid control technology, specifically to a reactive power compensation method and apparatus based on photovoltaic inverters. The method includes: acquiring real-time operating data of the photovoltaic inverter and historical compensation data from key monitoring points of the power grid; determining whether voltage fluctuations have occurred in the power grid based on the grid voltage in the real-time operating data; when grid voltage fluctuations are detected and the grid voltage exceeds a preset voltage range, calculating the reactive power demand of the power grid based on the real-time operating data; and determining the current state of the photovoltaic inverter based on the active and reactive power in the real-time operating data, where the current state includes normal operation, fault status, or current limiting status. This invention, by monitoring the operating status of the photovoltaic inverter and the voltage fluctuations of the power grid in real time, can flexibly adjust the reactive power output of the inverter according to the actual reactive power demand of the power grid, ensuring voltage stability and avoiding the negative impacts of grid voltage fluctuations.

Description

Technical Field

[0001] This invention relates to the field of power grid control technology, specifically to a reactive power compensation method and device based on photovoltaic inverters. Background Technology

[0002] Currently, traditional methods typically lack real-time monitoring of inverter operating status and grid voltage fluctuations, making it impossible to dynamically adjust inverter output based on actual grid reactive power demand. Furthermore, traditional methods lack intelligent management based on operating data and historical compensation, which may lead to some inverters operating at high loads for extended periods. This increases the risk of equipment failure, reduces inverter lifespan, and lacks a scientific approach to maintenance and replacement.

[0003] Furthermore, traditional methods generally do not determine whether the compensation effect meets the standard, nor do they provide early warnings based on cumulative operating time. When equipment malfunctions or requires maintenance, users may only be able to passively discover the problem, which reduces system stability and security. Moreover, when grid parameters change, traditional methods cannot dynamically update reactive power regulation capabilities or automatically adjust inverter output, resulting in poor system adaptability and an inability to quickly respond to changes in grid load or power factor. Summary of the Invention

[0004] To achieve the above objectives, the present invention provides the following technical solution: a reactive power compensation method based on a photovoltaic inverter, comprising:

[0005] Acquire real-time operating data of the photovoltaic inverter and historical compensation data of key monitoring points of the power grid; determine whether voltage fluctuations occur in the power grid based on the grid voltage in the real-time operating data; when grid voltage fluctuations are detected and the grid voltage exceeds the preset voltage range, calculate the reactive power demand of the power grid based on the real-time operating data;

[0006] The current state of the photovoltaic inverter is determined based on the active power and reactive power in the real-time operating data. The current state includes normal operation, fault state, or current limiting state.

[0007] In response to the current state being a normal operating state, the reactive power regulation capability of the photovoltaic inverter is determined based on the grid voltage and active power in the real-time operating data.

[0008] When the reactive power regulation capacity is greater than the reactive power demand and the inverter temperature is within a safe range, a first inverter is selected as a candidate compensation device, a first compensation effect is determined based on the real-time operating data of the first inverter, and the cumulative operating time of the first inverter is determined based on the historical compensation data.

[0009] If the first compensation effect meets the preset compensation standard and the cumulative operating time of the first inverter has not reached the maintenance threshold, it is determined that the first inverter will continue to perform reactive power compensation; otherwise, the second inverter is selected as a candidate compensation device based on the real-time operating data.

[0010] Preferably, the method further includes:

[0011] The second compensation effect is determined based on the real-time operating data of the second inverter, and the cumulative operating time of the second inverter is determined based on the historical compensation data;

[0012] Based on the first compensation effect, the second compensation effect, the cumulative operating time of the first inverter, and the cumulative operating time of the second inverter, it is determined whether the first inverter or the second inverter will perform reactive power compensation for the power grid.

[0013] In response to determining that reactive power compensation is performed on the power grid by the first inverter or the second inverter, the compensated power grid parameters are obtained, and the reactive power regulation capability is updated based on the compensated power grid parameters;

[0014] Based on the updated reactive power regulation capability and the reactive power demand of the power grid, the reactive power output command of the first inverter or the second inverter is adjusted.

[0015] Preferably, determining the first compensation effect based on the real-time operating data of the first inverter, and determining the cumulative operating time of the first inverter based on the historical compensation data, includes:

[0016] The actual reactive power output data of the first inverter during the compensation period is obtained, and the actual reactive power output data is compared with the reactive power demand of the power grid to obtain the first compensation effect.

[0017] The operating records of the first inverter in the historical compensation data are queried to obtain the cumulative operating time of the first inverter.

[0018] Preferably, based on the first compensation effect, the second compensation effect, the cumulative operating time of the first inverter, and the cumulative operating time of the second inverter, it is determined whether the first inverter or the second inverter will perform reactive power compensation to the power grid, including:

[0019] If the first compensation effect does not meet the preset compensation standard, the second compensation effect meets the preset compensation standard, and the cumulative operating time of the second inverter has not reached the maintenance threshold, then it is determined that the second inverter will perform reactive power compensation to the power grid.

[0020] If the first compensation effect does not meet the preset compensation standard, the second compensation effect meets the preset compensation standard, and the cumulative operating time of the second inverter reaches the maintenance threshold, then it is determined that the second inverter will perform reactive power compensation for the power grid, and an early warning message is output. The early warning message is used to instruct the user to maintain or replace the second inverter.

[0021] Preferably, determining whether the reactive power compensation of the power grid is performed by the first inverter or the second inverter based on the first compensation effect, the second compensation effect, the cumulative operating time of the first inverter, and the cumulative operating time of the second inverter further includes:

[0022] If the first compensation effect does not meet the preset compensation standard, and the second compensation effect does not meet the preset compensation standard, a prompt message is output, which is used to instruct the user to check the photovoltaic array or grid fault.

[0023] Preferably, determining whether the reactive power compensation of the power grid is performed by the first inverter or the second inverter based on the first compensation effect, the second compensation effect, the cumulative operating time of the first inverter, and the cumulative operating time of the second inverter further includes:

[0024] In response to the first compensation effect meeting the preset compensation standard, the cumulative operating time of the first inverter reaching the maintenance threshold, and the second compensation effect not meeting the preset compensation standard, it is determined that the first inverter will perform reactive power compensation to the power grid, and an early warning message is output. The early warning message is used to instruct the user to perform maintenance on the first inverter.

[0025] Preferably, determining whether the reactive power compensation of the power grid is performed by the first inverter or the second inverter based on the first compensation effect, the second compensation effect, the cumulative operating time of the first inverter, and the cumulative operating time of the second inverter further includes:

[0026] In response to the first compensation effect meeting the preset compensation standard, the cumulative operating time of the first inverter reaching the maintenance threshold, the second compensation effect meeting the preset compensation standard, and the cumulative operating time of the second inverter not reaching the maintenance threshold, it is determined that the second inverter will perform reactive power compensation to the power grid.

[0027] In response to the first compensation effect meeting the preset compensation standard, the cumulative operating time of the first inverter reaching the maintenance threshold, the second compensation effect meeting the preset compensation standard, and the cumulative operating time of the second inverter reaching the maintenance threshold, it is determined that the first inverter or the second inverter will perform reactive power compensation to the power grid based on the cumulative operating time of the first inverter and the cumulative operating time of the second inverter, and an early warning message is output. The early warning message is used to instruct the user to perform rotation maintenance on the inverter or add a new photovoltaic inverter.

[0028] Preferably, obtaining the compensated grid parameters and updating the reactive power regulation capability based on the compensated grid parameters includes:

[0029] Real-time acquisition of voltage and power factor data of the compensated network points to determine whether the voltage has recovered to the preset voltage range;

[0030] In response to the voltage returning to the preset voltage range, the remaining reactive power capacity of the photovoltaic inverter is recalculated based on the current active power and reactive power, and the reactive power regulation capability is updated.

[0031] Preferably, based on the updated reactive power regulation capability and the reactive power demand of the power grid, the reactive power output command of the first inverter or the second inverter is adjusted, including:

[0032] Compare the updated reactive power regulation capability with the reactive power demand of the power grid. If the updated reactive power regulation capability is less than the reactive power demand, reduce the active power output of the first inverter or the second inverter to release the reactive power regulation capability.

[0033] Based on the reduced active power output, a reactive power output command is regenerated and sent to the corresponding inverter.

[0034] A reactive power compensation device based on a photovoltaic inverter, applicable to the aforementioned reactive power compensation method based on a photovoltaic inverter, includes:

[0035] The voltage judgment unit is configured to acquire real-time operating data of the photovoltaic inverter and historical compensation data of key monitoring points of the power grid; determine whether voltage fluctuations have occurred in the power grid based on the grid point voltage in the real-time operating data; when grid voltage fluctuations are detected and the grid point voltage exceeds a preset voltage range, calculate the reactive power demand of the power grid based on the real-time operating data.

[0036] The status judgment unit is configured to determine the current status of the photovoltaic inverter based on the active power and reactive power in the real-time operating data. The current status includes normal operation status, fault status, or current limiting status.

[0037] The adjustment determination unit is configured to determine the reactive power regulation capability of the photovoltaic inverter based on the grid voltage and active power in the real-time operating data in response to the current state being a normal operating state.

[0038] The effect determination unit is configured to, in response to the reactive power regulation capacity being greater than the reactive power demand and the inverter temperature being within a safe range, select a first inverter as a candidate compensation device, determine a first compensation effect based on the real-time operating data of the first inverter, and determine the cumulative operating time of the first inverter based on the historical compensation data;

[0039] The reactive power compensation unit is configured to determine that the first inverter will continue to perform reactive power compensation when the first compensation effect meets the preset compensation standard and the cumulative operating time of the first inverter has not reached the maintenance threshold; otherwise, a second inverter is selected as a candidate compensation device based on the real-time operating data.

[0040] Compared with the prior art, the beneficial effects of the present invention are:

[0041] This invention monitors the operating status of photovoltaic inverters and the voltage fluctuations of the power grid in real time. It can flexibly adjust the reactive power output of the inverters according to the actual reactive power demand of the power grid, ensuring the voltage stability of the power grid and avoiding the negative impact of power grid voltage fluctuations. Moreover, by using the inverter's operating data, historical compensation data, and cumulative operating time, it can avoid overuse of a certain inverter, ensure that it operates within a safe range, reduce the risk of equipment failure, and reasonably arrange the maintenance and replacement of inverters, thereby extending the service life of the equipment.

[0042] This invention, by judging the compensation effect and cumulative operating time of the inverter, can promptly output early warning information when the compensation effect does not meet the standard or the equipment is close to its maintenance cycle, prompting users to perform necessary inspections, maintenance, or replacements, ensuring the stability and safety of the system. Moreover, the compensated grid parameters are collected in real time, and the reactive power regulation capability can be dynamically updated according to changes in grid voltage and power factor, and the reactive power output of the inverter can be adjusted to further improve the system's adaptability and responsiveness. Furthermore, by automatically selecting the most suitable inverter for reactive power compensation and determining the optimal operating mode through system analysis and decision-making, manual intervention is greatly reduced, and the intelligence and management efficiency of the entire photovoltaic system are improved. Attached Figure Description

[0043] Figure 1 This is a schematic flowchart of the overall method in one embodiment of the present invention;

[0044] Figure 2 This is a schematic diagram of the overall device architecture in one embodiment of the present invention.

[0045] In the diagram: 1. Voltage judgment unit; 2. Status judgment unit; 3. Adjustment determination unit; 4. Effect determination unit; 5. Reactive power compensation unit. Detailed Implementation

[0046] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0047] Example 1, please refer to Figure 1 This invention provides a technical solution: a reactive power compensation method based on a photovoltaic inverter, comprising:

[0048] S1. Obtain real-time operating data of the photovoltaic inverter and historical compensation data of key monitoring points of the power grid; determine whether voltage fluctuations occur in the power grid based on the grid voltage in the real-time operating data; when grid voltage fluctuations are detected and the grid voltage exceeds the preset voltage range, calculate the reactive power demand of the power grid based on the real-time operating data.

[0049] S2. Determine the current state of the photovoltaic inverter based on the active power and reactive power in the real-time operation data. The current state includes normal operation, fault state, or current limiting state.

[0050] S3. If the current state is normal operation, then the reactive power regulation capability of the photovoltaic inverter is determined based on the grid voltage and active power in the real-time operation data.

[0051] S4. When the reactive power regulation capacity is greater than the reactive power demand and the inverter temperature is within the safe range, the first inverter is selected as the candidate compensation device, the first compensation effect is determined based on the real-time operating data of the first inverter, and the cumulative operating time of the first inverter is determined based on the historical compensation data.

[0052] S5. In response to the first compensation effect meeting the preset compensation standard and the cumulative operating time of the first inverter not reaching the maintenance threshold, it is determined that the first inverter will continue to perform reactive power compensation; otherwise, the second inverter is selected as the candidate compensation device based on real-time operating data.

[0053] It should be noted that real-time operating data of photovoltaic inverters refers to the current operating status of the photovoltaic system, such as grid voltage, active power (supply), and reactive power (non-energy components of grid demand); historical compensation data refers to past grid compensation records, which helps the system determine which devices were able to effectively compensate for reactive power in the past. For example, assuming the photovoltaic system's inverter is running, data monitoring can show that the inverter's active power is 100kW and reactive power is 30kVAr; the grid monitoring points provide historical compensation data, recording previous compensation situations, such as using another inverter for compensation last month under the same voltage fluctuations.

[0054] Grid voltage fluctuations refer to fluctuations in grid voltage, which may cause equipment to malfunction. The presence of grid voltage fluctuations is determined by monitoring the voltage at specific points in the grid. If the voltage exceeds a preset range (e.g., 220V ± 10%), it can be considered that a grid voltage fluctuation has occurred. For example, if the current grid voltage is 245V, exceeding the normal voltage range (e.g., 220V ± 10%), the system detects a grid voltage fluctuation.

[0055] When grid voltage fluctuations are detected, the system calculates the reactive power required by the grid based on real-time data. When grid fluctuations occur, the photovoltaic inverter may need to provide a certain amount of reactive power to compensate for the grid's demand and ensure grid stability. For example, the system detects grid voltage fluctuations and calculates that the grid needs 40 kVAr of reactive power to restore stability.

[0056] A photovoltaic inverter may be in one of three states: normal operation, fault, or current limiting. The current state of the inverter can be determined by analyzing the active and reactive power data in real time. For example, if the inverter's active power is normal (100kW) and its reactive power is not overloaded (30kVAr), then the inverter is in normal operation. If a fault occurs, the inverter may not be able to provide sufficient reactive power or may enter a current limiting state, restricting the power supply.

[0057] When a photovoltaic inverter is in normal operation, the system calculates the inverter's reactive power regulation capability based on the grid voltage and active power. If the reactive power regulation capability is greater than the grid demand and the inverter's temperature is within a safe range, the inverter can be selected for reactive power compensation. For example, if the inverter's reactive power regulation capability is 50 kVAr, the grid requires 40 kVAr, and the inverter temperature is normal (not exceeding the set safe temperature), then the inverter can be selected as the compensation device.

[0058] If an inverter meets the compensation criteria and has not reached the maintenance threshold (e.g., cumulative operating time has not exceeded 1000 hours), it can continue to be used for reactive power compensation. If the inverter has been running for too long, it may need maintenance, and the system will select another backup inverter for compensation. For example, suppose the first inverter has been running for 800 hours and meets the compensation criteria, so the system decides to continue using it. If the first inverter has been running for 1000 hours, it needs maintenance, and the system will select a second inverter for compensation.

[0059] In an optional embodiment, the method further includes:

[0060] The second compensation effect is determined based on the real-time operating data of the second inverter, and the cumulative operating time of the second inverter is determined based on the historical compensation data.

[0061] Based on the first compensation effect, the second compensation effect, the cumulative operating time of the first inverter, and the cumulative operating time of the second inverter, it is determined whether the first inverter or the second inverter will provide reactive power compensation to the power grid.

[0062] In response to determining that the first inverter or the second inverter will perform reactive power compensation on the power grid, the grid parameters after compensation are obtained, and the reactive power regulation capability is updated based on the grid parameters after compensation.

[0063] Based on the updated reactive power regulation capability and the reactive power demand of the power grid, adjust the reactive power output command of the first inverter or the second inverter.

[0064] It should be noted that the real-time operating data and historical compensation data of the second inverter also need to be monitored and analyzed. Real-time data reveals the operating status of the second inverter (such as voltage, current, and power), while historical compensation data provides information on the inverter's performance under similar past conditions. For example, assuming the second inverter currently has an active power of 95kW, a reactive power of 35kVAr, and a grid voltage of 240V, historical data records the second inverter's compensation effect during grid voltage fluctuations; for instance, it previously successfully compensated for a reactive power demand of 40kVAr.

[0065] Real-time data can be used to calculate the reactive power compensation effect of the second inverter, which is the effective reactive power it can provide. Simultaneously, historical data is needed to determine the cumulative operating time of the second inverter to decide whether maintenance is required. For example, if the second inverter has been running for 950 hours and currently provides 40 kVAr of reactive power compensation, meeting the grid's requirements, further maintenance may need to be considered if its cumulative operating time approaches the maintenance threshold (e.g., 1000 hours).

[0066] Based on the compensation effects of the first and second inverters, and their cumulative operating time, the system will determine which inverter to use for reactive power compensation of the power grid. If the first inverter performs better and has not reached the maintenance threshold, it may be selected for compensation. If the second inverter is in a more suitable state, it will be selected. For example, suppose the first inverter has a reactive power compensation effect of 50 kVAr and has been running for 800 hours, while the second inverter has a compensation effect of 40 kVAr and has been running for 950 hours. Since the first inverter has a slightly stronger compensation capability and a shorter cumulative operating time, the system will select the first inverter for reactive power compensation.

[0067] After selecting the first or second inverter for reactive power compensation, the system needs to obtain the compensated grid parameters (such as grid voltage and frequency). Using this data, the system updates its reactive power regulation capability to ensure that the equipment's output always matches the grid demand. For example, after reactive power compensation by the first inverter, the grid voltage is adjusted from 240V to 235V. The system updates its reactive power regulation capability through real-time monitoring. The new regulation capability may become 45kVAr because the grid voltage has stabilized, allowing the inverter to provide more reactive power.

[0068] Based on the grid's reactive power demand and the updated reactive power regulation capability, the system will issue a new reactive power output command, requiring the first or second inverter to adjust its reactive power output. This is a dynamic adjustment process to ensure that the reactive power output of the inverter can continuously meet the grid demand and ensure grid stability. For example, suppose the grid's current reactive power demand is 40 kVAr, but due to previous compensation, the inverter's regulation capability has now increased to 45 kVAr. The system issues a command requiring the inverter to increase its reactive power from 30 kVAr to 40 kVAr to fully compensate for the grid demand.

[0069] In an optional embodiment, determining the first compensation effect based on real-time operating data of the first inverter and determining the cumulative operating time of the first inverter based on historical compensation data includes:

[0070] The actual reactive power output data of the first inverter during the compensation period is obtained, and the actual reactive power output data is compared with the reactive power demand of the power grid to obtain the first compensation effect.

[0071] By querying the historical compensation data of the first inverter's operating records, the cumulative operating time of the first inverter can be calculated.

[0072] It should be noted that monitoring the actual output of the first inverter over a certain period of time, especially the reactive power it provides, is crucial. Reactive power determines the stability of the grid voltage, so this is key data for judging the compensation effect. For example, suppose the first inverter actually outputs 35 kvar (kVAr) of reactive power between 9 am and 10 am, while the grid requires 40 kvar of reactive power at that time.

[0073] The actual reactive power output of the inverter is compared with the actual demand of the power grid to determine its compensation effect. The compensation effect reflects whether the inverter can meet the reactive power demand of the power grid and the degree of adequacy of the compensation. For example, if the power grid needs 40 kVAr, but the inverter only provides 35 kVAr, then the compensation effect of the first inverter is that it provides 85% of the demand (35 / 40), which means that it can basically meet the reactive power demand of the power grid, but there is still a certain gap.

[0074] In addition to real-time performance, it is also necessary to know how long the first inverter has been running. This helps to determine the equipment status, maintenance needs, and load capacity. By querying historical operation records, the cumulative operating time can be calculated. For example, by checking the historical compensation data of the first inverter, it can be found that it has been running continuously for 780 hours since its installation. This information can help determine whether it is close to the time when it needs to be shut down for maintenance. If the maintenance threshold is 1000 hours, then there is still a certain safety margin.

[0075] In an optional embodiment, determining whether the first inverter or the second inverter will perform reactive power compensation to the power grid based on the first compensation effect, the second compensation effect, the cumulative operating time of the first inverter, and the cumulative operating time of the second inverter includes:

[0076] If the first compensation effect does not meet the preset compensation standard, the second compensation effect meets the preset compensation standard, and the cumulative operating time of the second inverter has not reached the maintenance threshold, then it is determined that the second inverter will perform reactive power compensation to the power grid.

[0077] If the first compensation effect does not meet the preset compensation standard, the second compensation effect meets the preset compensation standard, and the cumulative operating time of the second inverter reaches the maintenance threshold, then it is determined that the second inverter will perform reactive power compensation for the power grid, and an early warning message is output. The early warning message is used to instruct the user to maintain or replace the second inverter.

[0078] It should be noted that, based on the operating status and compensation effect of the two inverters, the system intelligently selects which inverter to use for reactive power compensation to the grid and issues maintenance warnings when necessary. The judgment is based on four key factors: the compensation effect of the first inverter (whether it meets the standard); the compensation effect of the second inverter (whether it meets the standard); the cumulative operating time of the first inverter (whether it is close to the maintenance threshold); and the cumulative operating time of the second inverter (whether it is close to the maintenance threshold).

[0079] Scenario 1: The first inverter is insufficient, the second inverter is available, and it is not yet time for maintenance;

[0080] Conditions: The first inverter's compensation effect is insufficient, the second inverter's compensation effect is sufficient, and the second inverter's cumulative operating time has not exceeded the maintenance threshold; Action: Select the second inverter to perform reactive power compensation for the grid; Example: Grid reactive power demand: 40kVAr; First inverter output: 30kVAr → insufficient compensation effect; Second inverter output: 38kVAr → compensation effect is sufficient; Second inverter's cumulative operating time: 900 hours (maintenance threshold 1000 hours); In this case, the system will select the second inverter to continue compensating the grid because it is still capable and its operating status is safe;

[0081] Scenario 2: The first inverter is insufficient, and the second inverter is usable, but it is close to or has reached the maintenance threshold;

[0082] Conditions: The compensation effect of the first inverter is insufficient, while the compensation effect of the second inverter is sufficient, but the cumulative operating time of the second inverter has reached the maintenance threshold. Action: The second inverter will still compensate the grid, but a warning will be issued simultaneously to remind the user to maintain or replace the second inverter. Example: Grid reactive power demand: 40kVAr; First inverter output: 30kVAr → insufficient compensation effect; Second inverter output: 38kVAr → compensation effect is sufficient; Second inverter cumulative operating time: 1000 hours (reaching the maintenance threshold). Here, the system will still use the second inverter to provide compensation, but will generate a warning message, such as "The second inverter has reached the maintenance time limit, please arrange maintenance or replacement." This ensures grid stability and also reminds the user to avoid equipment failure.

[0083] In an optional embodiment, determining whether the first inverter or the second inverter will perform reactive power compensation to the power grid based on the first compensation effect, the second compensation effect, the cumulative operating time of the first inverter, and the cumulative operating time of the second inverter further includes:

[0084] If the first compensation effect does not meet the preset compensation standard, and the second compensation effect does not meet the preset compensation standard, a prompt message will be output to instruct the user to check for photovoltaic array or grid faults.

[0085] It should be noted that when neither inverter can meet the reactive power demand of the grid, the system can no longer simply select one inverter for compensation. Instead, it needs to alert the user that there may be a deeper problem, such as a photovoltaic array failure or a grid issue. The judgment criteria remain the same: the compensation effect of the first inverter (whether it meets the standard); the compensation effect of the second inverter (whether it meets the standard); the cumulative operating time of the first inverter (whether it is safe); and the cumulative operating time of the second inverter (whether it is safe).

[0086] This rule primarily focuses on whether the compensation effect meets the standard. If neither inverter meets the requirement, a prompt will be triggered.

[0087] Situation: Both inverters are not compensating up to standard;

[0088] Conditions: The compensation effect of the first inverter is insufficient, and the compensation effect of the second inverter is also insufficient; Action: The system will no longer select inverter compensation, but will output a prompt message to remind the user to check whether there is a fault in the photovoltaic array or the grid; Example: Grid reactive power demand: 40kVAr; First inverter output: 28kVAr → insufficient compensation effect; Second inverter output: 30kVAr → insufficient compensation effect; First inverter cumulative operating time: 800 hours (safe); Second inverter cumulative operating time: 950 hours (safe); In this case, the system cannot meet the grid demand through either inverter, so it will output a prompt message, such as: Warning: Reactive power compensation of both inverters is insufficient, please check whether there is a fault in the photovoltaic array or the grid.

[0089] In an optional embodiment, determining whether the first inverter or the second inverter will perform reactive power compensation to the power grid based on the first compensation effect, the second compensation effect, the cumulative operating time of the first inverter, and the cumulative operating time of the second inverter further includes:

[0090] If the first compensation effect meets the preset compensation standard, the cumulative operating time of the first inverter reaches the maintenance threshold, and the second compensation effect does not meet the preset compensation standard, then it is determined that the first inverter will perform reactive power compensation for the power grid, and an early warning message is output. The early warning message is used to instruct the user to perform maintenance on the first inverter.

[0091] It should be noted that there are several key conditions: First, the compensation effect of the first inverter meets the standard, that is, it can meet the reactive power demand of the power grid; the cumulative operating time of the first inverter has reached the maintenance threshold, indicating that this inverter has been running for a long time and may be close to the time when it needs to be repaired or replaced; second, the compensation effect of the second inverter does not meet the standard, that is, the second inverter cannot effectively compensate for the reactive power of the power grid.

[0092] Under these conditions, the system will: continue to use the first inverter because its compensation effect meets the requirements and can satisfy the grid's needs; and output a warning message to remind the user that the cumulative operating time of the first inverter has reached the maintenance threshold and should be maintained or inspected to ensure its long-term stable operation.

[0093] Example: Suppose the system has the following conditions: Grid reactive power demand: 50 kVAr; Output of the first inverter: 50 kVAr (compensation effect meets requirements); Cumulative operating time of the first inverter: 1500 hours (reached maintenance threshold of 1000 hours); Output of the second inverter: 30 kVAr (compensation effect insufficient, unable to meet demand); Cumulative operating time of the second inverter: 800 hours (far from reaching maintenance threshold); In this case, the system will choose to continue using the first inverter for compensation because its output effect meets the grid demand; Although the first inverter has reached the maintenance threshold, it can still continue to work, so it is not replaced immediately; However, the system will issue a warning message: "Warning: The cumulative operating time of the first inverter has reached the maintenance threshold, please arrange for maintenance or inspection;" This allows the user to promptly arrange for equipment maintenance or repair to avoid potential failures caused by prolonged high-load operation.

[0094] In an optional embodiment, determining whether the first inverter or the second inverter will perform reactive power compensation to the power grid based on the first compensation effect, the second compensation effect, the cumulative operating time of the first inverter, and the cumulative operating time of the second inverter further includes:

[0095] If the first compensation effect meets the preset compensation standard, the cumulative operating time of the first inverter reaches the maintenance threshold, the second compensation effect meets the preset compensation standard, and the cumulative operating time of the second inverter does not reach the maintenance threshold, then it is determined that the second inverter will perform reactive power compensation for the power grid.

[0096] In response to the first compensation effect meeting the preset compensation standard, the cumulative operating time of the first inverter reaching the maintenance threshold, the second compensation effect meeting the preset compensation standard, and the cumulative operating time of the second inverter reaching the maintenance threshold, it is determined whether the first inverter or the second inverter will perform reactive power compensation to the power grid based on the cumulative operating time of the first inverter and the cumulative operating time of the second inverter, and an early warning message is output. The early warning message is used to instruct users to perform rotation maintenance on the inverters or add new photovoltaic inverters.

[0097] It's important to clarify how to select the first or second inverter for reactive power compensation under specific conditions, and how to handle maintenance and management issues. Specifically, there are two scenarios: If the first inverter's compensation effect meets the standard and its cumulative operating time reaches the maintenance threshold, and if the second inverter's compensation effect also meets the standard, but its cumulative operating time has not reached the maintenance threshold, then the second inverter is selected for compensation. If both the first and second inverters meet the compensation effect, but their cumulative operating times have reached the maintenance threshold, then the choice of which inverter to use depends on their cumulative operating times. In this case, the system will output a warning message, prompting the user to perform rotation maintenance or consider adding a new photovoltaic inverter.

[0098] The compensation effect of the first inverter meets the requirements: this indicates that it can meet the reactive power demand of the power grid; the cumulative operating time of the first inverter reaches the maintenance threshold: this indicates that the equipment has been used for a period of time and needs maintenance; the compensation effect of the second inverter meets the requirements: this indicates that the second inverter can work normally; the cumulative operating time of the second inverter has not reached the maintenance threshold: this indicates that it is relatively new and does not yet need maintenance; if the cumulative operating time of both inverters reaches the maintenance threshold, it is necessary to decide which inverter to use based on the specific situation, and at the same time issue an early warning.

[0099] example:

[0100] Scenario 1: Select a second inverter;

[0101] Reactive power demand of the power grid: 60 kVAr; Output of the first inverter: 60 kVAr (compensation effect meets requirements); Cumulative operating time of the first inverter: 1200 hours (maintenance threshold reached); Output of the second inverter: 55 kVAr (compensation effect meets requirements); Cumulative operating time of the second inverter: 400 hours (maintenance threshold not reached); In this case: Although the first inverter can meet the demand, it needs maintenance due to its long operating time; Although the output of the second inverter is slightly insufficient, it can still be used because its cumulative operating time has not reached the maintenance period; Therefore, the system will select the second inverter for compensation; The system will perform the corresponding operation without outputting warning information because the selected inverter can still meet the demand and is in good condition;

[0102] Scenario 2: Output early warning information;

[0103] Grid reactive power demand: 70kVAr; Output of the first inverter: 70kVAr (compensation effect meets requirements); Cumulative operating time of the first inverter: 1500 hours (maintenance threshold reached); Output of the second inverter: 70kVAr (compensation effect meets requirements); Cumulative operating time of the second inverter: 1200 hours (maintenance threshold reached); In this case: the compensation effect of both inverters meets the requirements, but their cumulative operating time has reached the maintenance threshold; the system needs to decide which inverter to use based on their cumulative operating time (for example, the one with shorter operating time can be selected); at the same time, the system will output a warning message: "Warning: Both inverters have reached the maintenance threshold, please arrange for rotation maintenance or consider adding a new photovoltaic inverter;" This ensures the continuous and effective operation of the equipment and avoids potential failures.

[0104] In an optional embodiment, obtaining the compensated grid parameters and updating the reactive power regulation capability based on the compensated grid parameters includes:

[0105] Real-time collection of voltage and power factor data at the compensated network points to determine whether the voltage has recovered to the preset voltage range;

[0106] In response to the voltage returning to the preset voltage range, the remaining reactive power capacity of the photovoltaic inverter is recalculated based on the current active and reactive power, and the reactive power regulation capability is updated.

[0107] It should be noted that real-time monitoring and updating of the grid's reactive power regulation capability is crucial. Specifically, the operation includes real-time acquisition of voltage and power factor data of the grid after compensation, determining whether the voltage has recovered to the preset range, and recalculating the remaining reactive power capacity of the photovoltaic inverter to update the reactive power regulation capability. Real-time acquisition of grid parameters is also necessary: ​​after compensation, it is necessary to obtain the grid's voltage and power factor data in real time. These data can reflect the operating status of the grid, especially whether the grid has recovered to the normal voltage level after compensation.

[0108] Determine if the voltage has returned to the preset range: By comparing the actual measured voltage with the preset voltage range, determine if the grid voltage meets the requirements; if the grid voltage returns to the preset range, it means that the reactive power compensation has achieved the expected effect and the grid is operating normally.

[0109] The reactive power capacity is recalculated based on active and reactive power: If the voltage returns to the normal range, the system will recalculate the remaining reactive power capacity based on the current active power (i.e., the actual output power of the photovoltaic system) and reactive power (i.e., the photovoltaic inverter's ability to compensate the grid); then, the system will update the reactive power regulation capability of the photovoltaic inverter.

[0110] example:

[0111] Scenario 1: The power grid returns to normal, and reactive power regulation capacity is updated;

[0112] Before reactive power compensation, the grid voltage was 220V and the power factor was 0.9, indicating a reactive power problem that required compensation. After compensation by the photovoltaic inverter, the grid voltage rose to 230V and the power factor improved to 0.95. The system's real-time data showed a voltage of 230V and a power factor of 0.95, which is within the preset voltage range (220V-240V). In this case, the grid voltage has returned to the normal range, and the compensation was successful. The system recalculates the remaining reactive power capacity of the photovoltaic inverter based on the current active power (assuming 5kW) and reactive power (assuming 1kVAr). Assuming the total reactive power capacity of the photovoltaic inverter is 3kVAr, the remaining reactive power capacity is 2kVAr. The system updates the inverter's reactive power regulation capability to ensure it can provide more reactive power as needed, maintaining grid stability.

[0113] Scenario 2: Voltage has not recovered, and reactive power regulation capability cannot be updated;

[0114] After compensation, the grid voltage is 200V and the power factor is 0.85, which is still lower than the preset voltage range (220V-240V). The data collected by the system is: voltage 200V, power factor 0.85, the voltage has not recovered to the normal range. In this case, the grid voltage has not recovered, indicating that the compensation has not achieved the expected effect and the grid is still in an unstable state. The system will not update the reactive power capacity of the photovoltaic inverter according to the existing active and reactive power. Further adjustments or additional compensation measures may be needed, such as adding additional inverters or adjusting the operating status of existing inverters.

[0115] In an optional embodiment, adjusting the reactive power output command of the first inverter or the second inverter based on the updated reactive power regulation capability and the reactive power demand of the power grid includes:

[0116] Compare the updated reactive power regulation capability with the reactive power demand of the power grid. If the updated reactive power regulation capability is less than the reactive power demand, reduce the active power output of the first inverter or the second inverter to release the reactive power regulation capability.

[0117] Based on the reduced active power output, a reactive power output command is regenerated and sent to the corresponding inverter.

[0118] It should be noted that the updated reactive power regulation capability (i.e., the remaining reactive power compensation capability of the inverter) is compared with the actual reactive power demand of the power grid. The reactive power demand of the power grid is usually determined by factors such as load conditions and power generation, reflecting the reactive power required in the power grid to maintain stable operation.

[0119] In response to reactive power regulation capacity being less than reactive power demand: If the updated reactive power regulation capacity is less than the reactive power demand of the grid, the system will take measures to release more reactive power. This is usually achieved by reducing the active power output of the inverter, because the active and reactive power outputs of the inverter are mutually constrained. Reducing the active power output can release more reactive power regulation capacity and help the grid meet the reactive power demand.

[0120] Regenerate reactive power output instructions and send them to the inverter: After adjusting the active power, the system needs to recalculate the reactive power output instructions of the inverter based on the new active power output; these new instructions will be sent to the corresponding photovoltaic inverter to guide it to adjust the reactive power output, thereby achieving the reactive power compensation required by the grid.

[0121] example:

[0122] Scenario 1: Insufficient reactive power regulation capability, requiring adjustment of active power output;

[0123] The grid's reactive power demand is 5 kVAr; the updated first inverter has a reactive power regulation capacity of 3 kVAr, and the second inverter has a reactive power regulation capacity of 2 kVAr, totaling 5 kVAr. However, due to increased grid load, the actual reactive power demand exceeds the available reactive power regulation capacity. The system finds that the 5 kVAr reactive power regulation capacity is exactly equal to the grid's demand, but considering the grid's need for some redundancy compensation, the system judges that the current reactive power capacity is insufficient to cope with sudden changes in demand. To increase reactive power regulation capacity, the system decides to reduce the active power output of the first and second inverters. For example, assuming the current active power output of the first inverter is 4 kW and that of the second inverter is 3 kW, the system may choose to reduce the active power output of both, such as reducing the first inverter to 3.5 kW and the second inverter to 2.5 kW. After reducing the active power, the system regenerates the reactive power output command, adjusting the reactive power output of each inverter so that the grid can meet the 5 kVAr reactive power demand and ensure stable grid operation.

[0124] Scenario 2: The reactive power regulation capacity meets the demand and no adjustment is required;

[0125] The grid's reactive power demand remains at 5 kVAr; the updated first inverter has a reactive power regulation capacity of 6 kVAr, and the second inverter has a reactive power regulation capacity of 2 kVAr, totaling 8 kVAr. In this situation: the system compares the reactive power regulation capacity with the grid demand and finds that the 8 kVAr reactive power regulation capacity is greater than the 5 kVAr demand; there is no need to reduce the active power output because the grid demand has been over-met, and the inverter still has sufficient reactive power regulation capacity; the system will continue to monitor the grid status and adjust the inverter's reactive power output as needed, but no major adjustments are required at this time.

[0126] Example 2, please refer to Figure 2 This invention provides a technical solution: a reactive power compensation device based on a photovoltaic inverter, applicable to the aforementioned reactive power compensation method based on a photovoltaic inverter, comprising:

[0127] Voltage judgment unit 1 is configured to acquire real-time operating data of photovoltaic inverter and historical compensation data of key monitoring points of the power grid; determine whether voltage fluctuations have occurred in the power grid based on the grid voltage in the real-time operating data; when grid voltage fluctuations are detected and the grid voltage exceeds the preset voltage range, calculate the reactive power demand of the power grid based on the real-time operating data.

[0128] Status judgment unit 2 is configured to determine the current status of the photovoltaic inverter based on the active power and reactive power in the real-time operating data. The current status includes normal operation status, fault status or current limiting status.

[0129] Adjustment determination unit 3 is configured to determine the reactive power regulation capability of the photovoltaic inverter based on the grid voltage and active power in the real-time operation data in response to the current state being the normal operating state.

[0130] Effect determination unit 4 is configured to select the first inverter as a candidate compensation device when the reactive power regulation capacity is greater than the reactive power demand and the inverter temperature is within the safe range, determine the first compensation effect based on the real-time operating data of the first inverter, and determine the cumulative operating time of the first inverter based on historical compensation data.

[0131] The reactive power compensation unit 5 is configured to determine that the first inverter will continue to perform reactive power compensation when the first compensation effect meets the preset compensation standard and the cumulative operating time of the first inverter has not reached the maintenance threshold; otherwise, the second inverter will be selected as the candidate compensation device based on real-time operating data.

[0132] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited thereto. Various changes can be made within the scope of knowledge possessed by those skilled in the art without departing from the spirit of the present invention.

Claims

1. A reactive power compensation method based on photovoltaic inverters, characterized in that, include: Acquire real-time operating data of photovoltaic inverters and historical compensation data of key monitoring points in the power grid; The system determines whether voltage fluctuations occur in the power grid based on the grid point voltage in the real-time operation data. When grid voltage fluctuations are detected and the grid point voltage exceeds the preset voltage range, the reactive power demand of the power grid is calculated based on the real-time operation data. The current state of the photovoltaic inverter is determined based on the active power and reactive power in the real-time operating data. The current state includes normal operation, fault state, or current limiting state. In response to the current state being a normal operating state, the reactive power regulation capability of the photovoltaic inverter is determined based on the grid voltage and active power in the real-time operating data. When the reactive power regulation capacity is greater than the reactive power demand and the inverter temperature is within a safe range, a first inverter is selected as a candidate compensation device, a first compensation effect is determined based on the real-time operating data of the first inverter, and the cumulative operating time of the first inverter is determined based on the historical compensation data. If the first compensation effect meets the preset compensation standard and the cumulative operating time of the first inverter has not reached the maintenance threshold, it is determined that the first inverter will continue to perform reactive power compensation; otherwise, the second inverter is selected as a candidate compensation device based on the real-time operating data.

2. The reactive power compensation method based on a photovoltaic inverter according to claim 1, characterized in that, The method further includes: The second compensation effect is determined based on the real-time operating data of the second inverter, and the cumulative operating time of the second inverter is determined based on the historical compensation data; Based on the first compensation effect, the second compensation effect, the cumulative operating time of the first inverter, and the cumulative operating time of the second inverter, it is determined whether the first inverter or the second inverter will perform reactive power compensation for the power grid. In response to determining that reactive power compensation is performed on the power grid by the first inverter or the second inverter, the compensated power grid parameters are obtained, and the reactive power regulation capability is updated based on the compensated power grid parameters; Based on the updated reactive power regulation capability and the reactive power demand of the power grid, the reactive power output command of the first inverter or the second inverter is adjusted.

3. The reactive power compensation method based on a photovoltaic inverter according to claim 2, characterized in that, Determining the first compensation effect based on the real-time operating data of the first inverter, and determining the cumulative operating time of the first inverter based on the historical compensation data, including: The actual reactive power output data of the first inverter during the compensation period is obtained, and the actual reactive power output data is compared with the reactive power demand of the power grid to obtain the first compensation effect. The operating records of the first inverter in the historical compensation data are queried to obtain the cumulative operating time of the first inverter.

4. The reactive power compensation method based on a photovoltaic inverter according to claim 3, characterized in that, Based on the first compensation effect, the second compensation effect, the cumulative operating time of the first inverter, and the cumulative operating time of the second inverter, it is determined whether the first inverter or the second inverter will provide reactive power compensation to the power grid, including: If the first compensation effect does not meet the preset compensation standard, the second compensation effect meets the preset compensation standard, and the cumulative operating time of the second inverter has not reached the maintenance threshold, then it is determined that the second inverter will perform reactive power compensation to the power grid. If the first compensation effect does not meet the preset compensation standard, the second compensation effect meets the preset compensation standard, and the cumulative operating time of the second inverter reaches the maintenance threshold, then it is determined that the second inverter will perform reactive power compensation for the power grid, and an early warning message is output. The early warning message is used to instruct the user to maintain or replace the second inverter.

5. The reactive power compensation method based on a photovoltaic inverter according to claim 4, characterized in that, Based on the first compensation effect, the second compensation effect, the cumulative operating time of the first inverter, and the cumulative operating time of the second inverter, determining whether the first inverter or the second inverter will perform reactive power compensation to the power grid further includes: If the first compensation effect does not meet the preset compensation standard, and the second compensation effect does not meet the preset compensation standard, a prompt message is output, which is used to instruct the user to check the photovoltaic array or grid fault.

6. The reactive power compensation method based on a photovoltaic inverter according to claim 5, characterized in that, Based on the first compensation effect, the second compensation effect, the cumulative operating time of the first inverter, and the cumulative operating time of the second inverter, determining whether the first inverter or the second inverter will perform reactive power compensation to the power grid further includes: In response to the first compensation effect meeting the preset compensation standard, the cumulative operating time of the first inverter reaching the maintenance threshold, and the second compensation effect not meeting the preset compensation standard, it is determined that the first inverter will perform reactive power compensation to the power grid, and an early warning message is output. The early warning message is used to instruct the user to perform maintenance on the first inverter.

7. The reactive power compensation method based on a photovoltaic inverter according to claim 6, characterized in that, Based on the first compensation effect, the second compensation effect, the cumulative operating time of the first inverter, and the cumulative operating time of the second inverter, determining whether the first inverter or the second inverter will perform reactive power compensation to the power grid further includes: In response to the first compensation effect meeting the preset compensation standard, the cumulative operating time of the first inverter reaching the maintenance threshold, the second compensation effect meeting the preset compensation standard, and the cumulative operating time of the second inverter not reaching the maintenance threshold, it is determined that the second inverter will perform reactive power compensation to the power grid. In response to the first compensation effect meeting the preset compensation standard, the cumulative operating time of the first inverter reaching the maintenance threshold, the second compensation effect meeting the preset compensation standard, and the cumulative operating time of the second inverter reaching the maintenance threshold, it is determined that the first inverter or the second inverter will perform reactive power compensation to the power grid based on the cumulative operating time of the first inverter and the cumulative operating time of the second inverter, and an early warning message is output. The early warning message is used to instruct the user to perform rotation maintenance on the inverter or add a new photovoltaic inverter.

8. The reactive power compensation method based on a photovoltaic inverter according to claim 7, characterized in that, Obtaining the compensated grid parameters and updating the reactive power regulation capability based on the compensated grid parameters includes: Real-time acquisition of voltage and power factor data of the compensated network points to determine whether the voltage has recovered to the preset voltage range; In response to the voltage returning to the preset voltage range, the remaining reactive power capacity of the photovoltaic inverter is recalculated based on the current active power and reactive power, and the reactive power regulation capability is updated.

9. The reactive power compensation method based on a photovoltaic inverter according to claim 8, characterized in that, Based on the updated reactive power regulation capability and the reactive power demand of the power grid, adjust the reactive power output command of the first inverter or the second inverter, including: Compare the updated reactive power regulation capability with the reactive power demand of the power grid. If the updated reactive power regulation capability is less than the reactive power demand, reduce the active power output of the first inverter or the second inverter to release the reactive power regulation capability. Based on the reduced active power output, a reactive power output command is regenerated and sent to the corresponding inverter.

10. A reactive power compensation device based on a photovoltaic inverter, applicable to the reactive power compensation method based on a photovoltaic inverter as described in any one of claims 1-9, characterized in that, include: The voltage judgment unit is configured to acquire real-time operating data of the photovoltaic inverter and historical compensation data of key monitoring points of the power grid; determine whether voltage fluctuations have occurred in the power grid based on the grid point voltage in the real-time operating data; when grid voltage fluctuations are detected and the grid point voltage exceeds a preset voltage range, calculate the reactive power demand of the power grid based on the real-time operating data. The status judgment unit is configured to determine the current status of the photovoltaic inverter based on the active power and reactive power in the real-time operating data. The current status includes normal operation status, fault status, or current limiting status. The adjustment determination unit is configured to determine the reactive power regulation capability of the photovoltaic inverter based on the grid voltage and active power in the real-time operating data in response to the current state being a normal operating state. The effect determination unit is configured to, in response to the reactive power regulation capacity being greater than the reactive power demand and the inverter temperature being within a safe range, select a first inverter as a candidate compensation device, determine a first compensation effect based on the real-time operating data of the first inverter, and determine the cumulative operating time of the first inverter based on the historical compensation data; The reactive power compensation unit is configured to determine that the first inverter will continue to perform reactive power compensation when the first compensation effect meets the preset compensation standard and the cumulative operating time of the first inverter has not reached the maintenance threshold; otherwise, a second inverter is selected as a candidate compensation device based on the real-time operating data.

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