An inverter control method and device and an inverter

Abstract

The application discloses an inverter control method and device and an inverter, relates to the distributed grid-connected power generation technical field, and aims to solve the technical problem that synchronous regulation of multiple inverters in anti-flow control may cause control conflict, leading to control delay and regulation failure of the grid-connected system. Each inverter independently acquires the current power of a grid-connected point to determine an action to be executed, and determines an action triggering time based on priority, so that different inverters can execute power regulation actions in sequence, avoiding control conflict caused by synchronous regulation. When the action triggering time is reached, if the inverter and the total minimum stable operation power of the currently connected power generation module do not match after the inverter regulates the power generation power limit value, the start-stop state of the power generation module is adjusted again, thereby solving the problem of unstable operation caused by simple power regulation. It can be seen that the inverter control method provided by the application can realize reliable anti-flow function, and improves the stability and reliability of the grid-connected system.

Description

Technical Field

[0001] This invention relates to the field of distributed grid-connected power generation technology, and in particular to an inverter control method, device, and inverter. Background Technology

[0002] In distributed photovoltaic (PV) power generation systems, when the PV power output exceeds the local load power, excess power flows back into the grid. Since traditional grids are generally designed based on forward loads, this reverse power flow can interfere with normal power dispatching and relay protection functions, affecting power quality. Therefore, to reduce the impact of distributed PV power generation systems on the grid, inverters with anti-reverse flow capabilities are needed to regulate output power and ensure the normal operation of the distribution network.

[0003] In existing scenarios involving parallel networking of multiple inverters, a centralized controller is often omitted to reduce costs. This leads to communication limitations between the inverters, making it difficult to obtain real-time power data and the number of inverters online. Information on the overall power flow can only be obtained from the electricity meter at the grid connection point. To address this, existing technologies typically assume an equivalent number of micro-inverters N in the network, divide the total reverse power by N to obtain the regulation power of each inverter, and after each regulation, re-acquire the meter reading, compare it with the previous reading, and then each inverter updates the equivalent number of inverters in the network automatically. However, due to potential discrepancies in the assumed number of equivalent micro-inverters between multiple inverters caused by regulation synchronization issues, this method suffers from control delays, lacks timeliness, and results in poor control performance. Summary of the Invention

[0004] The purpose of this invention is to provide an inverter control method, device, and inverter to solve the technical problem of control delay and regulation failure in grid-connected systems caused by control conflicts resulting from the synchronous regulation of multiple inverters in anti-reverse flow control scenarios in existing power regulation methods.

[0005] To address the aforementioned technical problems, this invention provides an inverter control method applicable to any one of multiple inverters in a grid-connected system. Each inverter is connected to the power grid and a multi-generation module. The inverter control method includes: Obtain the current power at the grid connection point of the inverter; The action to be performed is determined based on the current power level. The action to be performed includes power reduction and power increase actions. The timing of its own action is determined based on the preset priority of the inverter; the order of action triggering is positively correlated with the priority of the inverter. When the action triggering time is reached, the inverter's power generation limit is adjusted based on the action to be executed; When the adjusted power generation limit does not match the total minimum stable operating power of the currently connected power generation modules, the start / stop status of the power generation modules is adjusted.

[0006] Optionally, the action to be performed can be determined based on the current power, including: The current power is compared with the preset lower trigger power threshold and the preset upper trigger power threshold. If the current power is less than or equal to the power reduction trigger threshold, the action to be executed is determined to be a power reduction action; If the current power is greater than the power increase trigger threshold, the action to be executed is determined to be a power increase action.

[0007] Optionally, the inverter is assigned a unique priority number. When the action to be performed is a power increase action, the smaller the priority number, the higher the priority of the inverter; when the action to be performed is a power decrease action, the larger the priority number, the higher the priority of the inverter. The timing of its own action is determined based on the preset inverter priority, including: When the action to be executed is a power reduction action, determine the difference between the total number of inverters in the grid-connected system and its own priority number; The power reduction counting threshold is determined based on the difference, and the magnitude of the power reduction counting threshold is positively linearly correlated with the difference. When the action to be performed is a power increase action, the power increase count threshold is determined based on its own priority number. The power increase count threshold is positively linearly correlated with the priority number.

[0008] Optionally, determining when the inverter reaches the action trigger point includes: When the action to be performed is a power reduction action, the current boost power count value of the inverter is cleared to zero; Increment the inverter's current power reduction count value by 1 to obtain the new current power reduction count value; the initial value of the power reduction count value is 0. When a new power reduction count value reaches the power reduction count threshold, the timing for triggering the action is determined. When the pending action is a power increase action, the current power reduction counter value of the inverter is cleared to zero; Increment the inverter's current power boost count by 1 to obtain the new current power boost count; the initial value of the power boost count is 0. When the new current boost power count value reaches the boost power count threshold, the new current boost power count value is cleared to zero, thus determining the timing for triggering the action.

[0009] Optionally, the inverter's power generation limit can be adjusted based on the action to be performed, including: When the action to be performed is a power reduction action, the current power generation limit of the inverter is subtracted from the preset power reduction step size to obtain the adjusted power generation limit. When the action to be performed is a power increase action, the current power generation limit of the inverter is added to the preset power increase step size to obtain the adjusted power generation limit.

[0010] Optionally, determine whether the adjusted power generation limit matches the total minimum stable operating power of the currently connected power generation modules, including: Obtain the number of power generation modules currently in operation and the minimum stable operating power of a single power generation module; When the action to be performed is a power reduction action, the total minimum stable operating power is determined based on the number of power generation modules currently in operation and the minimum stable operating power. If the adjusted power generation limit is less than the total minimum stable operating power, then the power generation limit is determined to be mismatched with the total minimum stable operating power. When the action to be performed is a power increase action, the number of currently running power generation modules is increased by one to obtain the target number of running modules; The total minimum stable operating power is determined by the product of the target number of operations and the minimum stable operating power. If the adjusted power generation limit is greater than or equal to the total minimum stable operating power, then the power generation limit is determined to be mismatched with the total minimum stable operating power.

[0011] Optionally, the start / stop status of the power generation module can be adjusted, including: When the action to be performed is a power reduction action, control one of the power generation modules that is currently in operation to stop running; When the action to be performed is a power increase action, control one of the power generation modules that is currently not in operation to start running.

[0012] Optionally, when the action to be performed is a power reduction action, after adjusting the inverter's power generation limit based on the action to be performed, the following steps are also included: The single-channel power limit of each power generation module currently in operation is determined based on the power generation limit after inverter adjustment. Each power generation module is controlled based on a single-path power limit.

[0013] To address the aforementioned technical problems, the present invention also provides an inverter control device, comprising: Memory, used to store computer programs; A processor is used to execute computer programs to implement the steps of the inverter control method described above.

[0014] To address the aforementioned technical problems, the present invention also provides an inverter, including an inverter body and an inverter control device as described above; the inverter body is connected to the inverter control device.

[0015] This invention provides an inverter control method applied to a multi-machine, multi-path grid-connected system consisting of a power grid, multiple generator modules, and multiple inverters. Each inverter independently acquires the current power at the grid connection point to determine the action to be executed and determines the action triggering timing based on a preset priority. This allows different inverters to execute power regulation actions in priority order, enabling multiple inverters in the grid-connected system to trigger regulation actions sequentially. This avoids numerical deviations caused by synchronous regulation of multiple inverters in traditional equivalent estimation methods. Furthermore, upon reaching the action triggering timing, the inverter adjusts its own power generation limit. If the adjusted power generation limit does not match the total minimum stable operating power of the currently connected generator modules, the inverter further adjusts the start / stop state of the generator modules, solving the operational instability problem that may result from solely relying on power limit adjustment. Therefore, the inverter control method provided by this invention can avoid control delay and numerical deviation problems in the anti-reverse current regulation process, achieving reliable anti-reverse current function and effectively improving the stability and reliability of the grid-connected system.

[0016] The present invention also provides an inverter control device and an inverter, which have the same beneficial effects as the inverter control method described above. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the prior art and embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 A flowchart of an inverter control method provided by the present invention; Figure 2 This invention provides a structural diagram of a distributed photovoltaic grid-connected system; Figure 3 A flowchart of another inverter control method provided by the present invention; Figure 4 A flowchart of another inverter control method provided by the present invention; Figure 5 A flowchart of another inverter control method provided by the present invention; Figure 6 A structural diagram of an inverter control device provided by the present invention; Figure 7This is a structural diagram of an inverter provided by the present invention. Detailed Implementation

[0019] The core of this invention is to provide an inverter control method, device, and inverter, which aims to enable multiple inverters to independently and orderly adjust power, avoiding mutual interference caused by synchronous operation; at the same time, it ensures the stable operation of the power generation module during the adjustment process and improves the control accuracy of the grid-connected system.

[0020] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, 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, 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.

[0021] This invention provides an inverter control method, such as... Figure 1 As shown, Figure 1 This invention provides a flowchart of an inverter control method. The inverter control method is applied to any one of multiple inverters in a grid-connected system. Each inverter is connected to the power grid and a multi-generation module. The inverter control method includes: S11. Obtain the current power at the grid connection point of the inverter; First, it should be noted that, as Figure 2 As shown, Figure 2 This invention provides a structural diagram of a distributed photovoltaic grid-connected system. A distributed photovoltaic grid-connected system typically includes multiple photovoltaic modules (PV modules). To achieve power inversion and grid connection, multiple micro-inverters are often configured in parallel, with each inverter connecting to several photovoltaic modules. The outputs of all inverters are uniformly connected to a grid connection point, which is equipped with a bidirectional meter. The meter broadcasts the real-time power of the grid connection point to all inverters in the system at regular intervals. The basic logic of the anti-reverse current function of the photovoltaic grid-connected system is to monitor the real-time power of the grid connection point and adjust the upper limit of the photovoltaic power generation system's output according to the direction and magnitude of the real-time power, thereby fully utilizing the photovoltaic power generation capacity without generating reverse power.

[0022] Considering that in the above-mentioned multi-machine multi-path parallel networking scenario, a centralized energy manager or cloud controller is usually omitted to reduce the configuration cost of the grid-connected system. However, this results in a lack of multi-terminal communication capabilities between different inverters. It is difficult for a single inverter to obtain each other's real-time power data and the number of inverters online in real time. It can only rely on the total power performance of the grid connection point to perceive the global status.

[0023] Based on this, in this step, each inverter independently receives the real-time power broadcast by the bidirectional meter, uses it as the current power to determine the overall power flow of the grid-connected system, and then determines whether to perform power regulation actions. It is evident that this step utilizes only the data communication between the inverter and the bidirectional meter, enabling each inverter to obtain the total power data of the grid-connected system without a centralized controller. This eliminates hardware costs and multiple communication requirements, providing a data foundation for subsequent inverter power regulation.

[0024] S12. Determine the action to be executed based on the current power, including power reduction action and power increase action; When photovoltaic (PV) power generation exceeds local load power, excess electricity will flow back to the grid. Since distribution networks are typically designed based on forward loads, this reverse power flow can interfere with the normal dispatching of the power grid system. Conversely, when power generation is less than local load and the grid does not require reverse flow protection, if the inverter remains in reduced-power operation, it will lead to a waste of PV power generation resources.

[0025] Based on this, such as Figure 3 As shown, Figure 3 This is a flowchart of another inverter control method provided by the present invention. The inverter compares the acquired current power with a preset power threshold. If the current power is less than the power threshold, it indicates that the photovoltaic power generation is greater than the local power load of the grid-connected system, and there is a risk of reverse current. The inverter needs to perform a power reduction action. If the current power is greater than or equal to the power threshold, it indicates that the photovoltaic power generation is less than the local power load, and there is no risk of reverse current. The inverter needs to perform a power increase action.

[0026] It should be noted that the current power read by a bidirectional meter includes both numerical and directional attributes. For example, the current power at the grid connection point is defined as P. net The preset power threshold is P. set Then when P net ≥P set When P is in a forward direction, it indicates that the power at the grid connection point flows from the distribution network to the local system, which includes photovoltaics and loads; conversely, if P... net <P set This represents the power transmitted from the local system to the distribution network in the reverse direction. Meanwhile, the aforementioned power threshold P... set It can be set to 0; or, in order to reserve control margin against backflow and prevent frequent false triggering, it can be set to a smaller positive power value according to actual needs.

[0027] As can be seen, this step clarifies the adjustment direction of the subsequent output power of each inverter, providing a judgment condition for anti-reverse current control.

[0028] S13. Determine the triggering time of its own action based on the preset priority of the inverter; wherein, the order of the action triggering time is positively correlated with the priority of the inverter; Considering that in a grid-connected system without a centralized controller, if multiple inverters synchronously perform adjustment actions after receiving the current power from the meter, coordination interference will occur, making it impossible to accurately determine the actual impact of the action of a single inverter on the total power at the grid connection point, which may lead to control delay or adjustment failure of the grid-connected system.

[0029] Based on this, this step presets different priorities for each inverter, achieving peak-shaving regulation by controlling response delays. Specifically, during grid-connected system configuration, each inverter within the system can be assigned a unique number to represent its priority. The inverter determines its corresponding waiting time or counting threshold based on its own priority. For different pending actions such as power reduction or power increase, each inverter calculates different action trigger times based on its own priority, thus staggering the action times of multiple inverters. It is evident that this step establishes the order of inverter actions through pre-configured priorities, eliminating control conflicts caused by multi-machine synchronous regulation.

[0030] S14. When the action triggering time is reached, adjust the inverter's power generation limit based on the action to be executed; Considering that after determining the triggering time through the above steps, each inverter needs to perform power generation limit adjustment when it reaches its own action triggering time.

[0031] Specifically, the inverter accumulates a counter value according to the determined action to be executed, based on the control cycle, to determine whether the action triggering timing has been reached. If the action to be executed is a power reduction action, the inverter accumulates the power reduction counter. When the power reduction triggering timing corresponding to its own priority is reached, the inverter reduces the overall generator power limit by a predetermined step size. If the action to be executed is a power increase action, the inverter accumulates the power increase counter. When the power increase triggering timing corresponding to its own priority is reached, the inverter increases the overall generator power limit by a predetermined step size. Since the triggering timings of multiple inverters are different, when the grid connection point needs to reduce or increase power, the multiple inverters in the grid-connected system will complete the power adjustment sequentially according to priority, ensuring the orderly allocation and execution of the anti-reverse current regulation task.

[0032] S15. When the adjusted power generation limit does not match the total minimum stable operating power of the power generation modules currently connected to the module, adjust the start / stop status of the power generation module.

[0033] Considering that the power generation module needs to be maintained above the minimum operating power to work stably, if the power generation limit is continuously lowered until it is below the minimum allowable value required for the normal operation of the power generation module, it may cause abnormal operation or even damage.

[0034] Based on this, after adjusting the power generation limit, if the limit is lower than the total minimum stable operating power of the currently active power generation modules, some power generation modules are shut down to reduce the demand on the total minimum stable operating power. If the limit is increased and the startup conditions are met, the shut-down power generation modules are restarted. Each input channel within the inverter corresponds to one power generation module, and the start and stop of a single module can be achieved by controlling the power device switch of the corresponding channel. Therefore, this step, by controlling the start and stop of individual modules, avoids hardware malfunctions caused by excessively low power generation limits, ensuring the inverter's operational stability.

[0035] In summary, this embodiment utilizes the inverter to obtain the current power of the electricity meters in the grid-connected system to determine the power adjustment direction. Based on priority, it staggers the triggering times of each inverter's actions, independently adjusting the overall power generation limit, thus avoiding control interference caused by synchronous adjustment of multiple inverters in scenarios without a centralized controller. Subsequently, when the power generation limit is too low, it coordinates with the start-stop control of the power generation module to ensure stable hardware operation. Therefore, the inverter control method provided by this invention solves the coordination interference problem in multi-inverter anti-reverse current scenarios, effectively improving the stability and accuracy of power control in the grid-connected system without the need for an additional centralized controller.

[0036] Based on the above embodiments: As an optional embodiment, determining the action to be performed based on the current power includes: The current power is compared with the preset lower trigger power threshold and the preset upper trigger power threshold. If the current power is less than or equal to the power reduction trigger threshold, the action to be executed is determined to be a power reduction action; If the current power is greater than the power increase trigger threshold, the action to be executed is determined to be a power increase action.

[0037] Considering that if the current power at the grid connection point fluctuates around a single power threshold, the inverter is prone to repeatedly switching between power reduction and power increase actions. Such frequent control state transitions not only increase the losses of internal circuit components of the inverter, but also cause oscillations in the output power of the grid-connected system, affecting the overall stability of the grid-connected system.

[0038] Based on this, this embodiment sets both a downward trigger power threshold and an upward trigger power threshold. After obtaining the current power at the grid connection point, the inverter compares the current power with the two thresholds. The upward trigger power threshold is greater than the downward trigger power threshold. When the current power is greater than the downward trigger power threshold but less than or equal to the upward trigger power threshold, the inverter maintains the current power generation limit unchanged. Only when the current power is less than or equal to the downward trigger power threshold does the inverter determine that there is a reverse current risk and execute a power downward adjustment. When the current power is greater than the upward trigger power threshold, the inverter executes a power upward adjustment. This dual-threshold judgment method effectively avoids false triggering of inverter power adjustments caused by power fluctuations.

[0039] It should be noted that the specific values ​​for lowering and raising the trigger power threshold can be configured based on the total installed capacity of the generator modules in the grid-connected system, the normal fluctuation range of the local load, and the anti-reverse current specifications of the local distribution network. In practical applications, the lower trigger power threshold is usually set to a positive power value close to zero or a very small value to strictly prevent power from flowing back to the distribution network; the higher trigger power threshold is set to a larger positive power value to ensure that the local load is fully powered before raising the inverter's generator power limit.

[0040] As can be seen, by setting different values ​​for the lowering and raising of the trigger power threshold, this embodiment avoids the false triggering of the inverter's power regulation when the grid connection point power fluctuates near the critical threshold, effectively improving the accuracy of anti-reverse current control and the stability of the inverter and grid connection system operation.

[0041] As an optional embodiment, the inverter is assigned a unique priority number. When the action to be performed is a power increase action, the smaller the priority number, the higher the priority of the inverter; when the action to be performed is a power decrease action, the larger the priority number, the higher the priority of the inverter. The timing of its own action is determined based on the preset inverter priority, including: When the action to be executed is a power reduction action, determine the difference between the total number of inverters in the grid-connected system and its own priority number; The power reduction counting threshold is determined based on the difference, and the magnitude of the power reduction counting threshold is positively linearly correlated with the difference. When the action to be performed is a power increase action, the power increase count threshold is determined based on its own priority number. The power increase count threshold is positively linearly correlated with the priority number.

[0042] Considering that if the power increase and decrease processes in a grid-connected system both use the same response sequence, it would lead to the same inverter consistently prioritizing power regulation tasks, resulting in uneven aging of the inverter's internal circuitry and inconsistent hardware losses. Furthermore, a fixed response sequence makes it difficult to accommodate the response rate requirements of different power regulation directions when faced with sudden load changes.

[0043] Based on this, this embodiment assigns a unique priority number to each inverter in the grid-connected system, and assigns different physical meanings to the priority numbers under different action types, such as... Figure 4 and Figure 5 As shown, Figure 4 A flowchart of another inverter control method provided by the present invention. Figure 5 This is a flowchart of another inverter control method provided by the present invention. Specifically, the total number of inverters in the grid-connected system is denoted as... N INV The inverter's own priority number is K INV (For example, numbered 1, 2, ..., N INV At the same time, priority numbers can also be assigned to the generator modules on each inverter. K PV (For example, each power generation module is numbered 1, 2, ..., K PV , ..., N PV ), and let the power reduction counting threshold be . The power-up counting threshold is It should be noted that in a distributed grid-connected system, each inverter only knows the total number of inverters configured in the grid-connected system. N INV and its own number K INV It does not require knowing how many inverters are actually online and connected to the grid during operation. This premise ensures that this method can arbitrarily shut down any inverter in the grid-connected system.

[0044] When performing a power increase action, a smaller priority number indicates a higher priority, allowing inverters with lower priority numbers to increase their power first. Conversely, when performing a power decrease action, a larger priority number indicates a higher priority, allowing inverters with higher priority numbers to decrease their power first. When the action to be performed is a power decrease action, the inverter calculates the total number of inverters in the grid-connected system. N INV Priority number K INV The difference is used to determine the power reduction counting threshold. The smaller the difference, the lower the calculated power reduction counting threshold, and the sooner the inverter reaches the activation trigger point. The specific power reduction counting threshold... The calculation formula is: ; in, k This is the preset counting interval.

[0045] When the action to be executed is a power increase action, the inverter directly determines the power increase count threshold based on its own priority number. The smaller the priority number, the lower the calculated power increase count threshold, and the earlier the inverter reaches the action triggering time. The specific power increase count threshold... The calculation formula is: ; in, k This is the preset counting interval.

[0046] The above process achieves a balanced distribution of the operating time of multiple inverters in the grid-connected system by using opposite priority response logic for the power increase and power decrease directions.

[0047] It should be noted that the total number of inverters in the grid-connected system N INV The calculation formulas for the power increase and power decrease counting thresholds can be pre-written into the memory of each inverter during the initial setup of the grid-connected system. The specific calculation formulas can include a fixed base control cycle, for example, using an integer multiple of this control cycle as the basis for counting accumulation, thereby ensuring that the calculated triggering times of each inverter are staggered on the time axis. Furthermore, the specific control cycle can be flexibly configured according to the requirements of the anti-reverse current response. For example, if the anti-reverse current regulation requires a power reset response within 2 minutes, the corresponding control cycle can be set to 1 second, with 20 times this cycle as the counting base, i.e., the preset counting interval. k =20; If the anti-backflow regulations require a response within 30 seconds, the control cycle can be shortened to 20ms or 50ms accordingly, using 20 times that as the counting benchmark, and taking the preset counting interval. k =20.

[0048] Among them, the counting interval k The smaller the value, the faster the system response after power reversal, but it must be much larger than the communication delay; otherwise, it may cause interference between different inverters. Conversely, the larger the value, the faster the system response after power reversal. k The larger the value, the longer the inverter may need to wait for power control response. In the worst-case scenario (i.e., all inverters in the grid-connected system are offline except for inverter number 1), the maximum response delay required after a reverse current occurs in the grid-connected system corresponds to... k ( NINV -1) corresponds to the time.

[0049] As can be seen, this embodiment, by employing a reversible priority determination method for two different pending actions—power increase and power decrease—and combining it with a counting threshold calculation that is linearly related to the priority number, effectively avoids control conflicts caused by multi-machine synchronous adjustment, achieves a balanced distribution of the working time of each inverter in the grid-connected system, and extends the overall service life of the hardware.

[0050] As an optional embodiment, determining when the inverter reaches the action trigger point includes: When the action to be performed is a power reduction action, the current boost power count value of the inverter is cleared to zero; Increment the inverter's current power reduction count value by 1 to obtain the new current power reduction count value; the initial value of the power reduction count value is 0. When a new power reduction count value reaches the power reduction count threshold, the timing for triggering the action is determined. When the pending action is a power increase action, the current power reduction counter value of the inverter is cleared to zero; Increment the inverter's current power boost count by 1 to obtain the new current power boost count; the initial value of the power boost count is 0. When the new current boost power count value reaches the boost power count threshold, the new current boost power count value is cleared to zero, thus determining the timing for triggering the action.

[0051] Considering that in the actual operation of the grid-connected system, the real-time power at the grid connection point may fluctuate due to sudden load changes, the action to be executed by the inverter in the continuous control cycle may change between power reduction and power increase, which may lead to false triggering of power adjustment by the inverter and affect the stability of the output power of the grid-connected system.

[0052] Based on this, this embodiment configures mutually exclusive reset logic and independent accumulation counters for power reduction and power increase actions. Specifically, the power reduction count value is recorded as... The power count value is recorded as Within each control cycle, when the inverter determines that the current action to be performed is a power downshift, it will increase the power counter value. Reset to zero to interrupt the previous upward timing, and simultaneously reduce the power count value. Increment by 1; conversely, if the action to be performed is a power increase action, interrupt the power decrease timing and increment the power increase count value. The inverter only confirms the triggering of an action when specific actions to be executed occur consecutively, causing the corresponding count value to continuously accumulate and reach a set count threshold. Specifically, when the action to be executed is a power increase action and the power increase count threshold is reached, the new current power increase count value is directly set. The purpose of resetting to zero is to force the inverter to reassess the grid connection point power in subsequent control cycles after the current power increase is completed, so as to avoid the inverter continuously and endlessly increasing the power, thereby ensuring the safe operation of the hardware circuit.

[0053] It should be noted that the power-up count value and power reduction count value The update frequency is determined by the broadcast cycle of the bidirectional meter in the grid-connected system or the local communication sampling cycle of the inverter (such as the aforementioned 20ms, 50ms or 1s).

[0054] As can be seen, this embodiment utilizes mutually exclusive zeroing and continuous accumulation counting logic to avoid inverter malfunctions caused by instantaneous power fluctuations at the grid connection point, thereby improving the accuracy of grid-connected system anti-reverse current regulation without the need for centralized controller intervention.

[0055] As an optional embodiment, adjusting the inverter's power generation limit based on the action to be performed includes: When the action to be performed is a power reduction action, the current power generation limit of the inverter is subtracted from the preset power reduction step size to obtain the adjusted power generation limit. When the action to be performed is a power increase action, the current power generation limit of the inverter is added to the preset power increase step size to obtain the adjusted power generation limit.

[0056] Considering that in the process of preventing reverse current in the grid-connected system, if the output power of the inverter is reduced to zero or a small value when a reverse current risk is determined, or if the power is directly increased to the maximum rated power of the inverter when the current power is greater than the threshold for increasing the trigger power, it may cause current surges in the distribution network or cause power reverse current to occur again, thereby causing oscillations in the current power at the grid connection point.

[0057] Based on this, this embodiment employs a step-by-step power regulation logic. Specifically, when it is determined that the action triggering time has been reached and the action to be executed is a power reduction action, the inverter reduces the preset power reduction step size based on the current power generation limit to obtain a new power generation limit; when the action to be executed is a power increase action, the preset power increase step size is increased based on the current power generation limit to obtain an adjusted power generation limit. The above control method, by adjusting the step size according to the current limit, enables the inverter's output power to transition smoothly, avoiding oscillations in the grid-connected system's output power.

[0058] It should be noted that the size of the power reduction step size and the power increase step size directly affect the power regulation response speed of the grid-connected system. Preferably, to balance response speed and the smoothness of the regulation process, the step size can be set as a percentage of the difference between the current power at the grid connection point and the preset anti-reverse current target power (e.g., 10% or 20% of this difference), depending on actual control needs. Furthermore, the adjusted power generation limit has upper and lower boundaries in practical applications. Its maximum value must not exceed the inverter's rated power, and its minimum value must not be lower than the minimum power limit for stable inverter operation, to ensure the safety of the inverter's internal circuitry.

[0059] As can be seen, this embodiment achieves smooth adjustment of the inverter's power generation limit by setting preset power down-adjustment step size and power up-adjustment step size, effectively improving the accuracy of anti-reverse current control and avoiding current surges caused by power fluctuations to the grid-connected system.

[0060] As an optional embodiment, determining whether the adjusted power generation limit matches the total minimum stable operating power of the currently connected power generation modules includes: Obtain the number of power generation modules currently in operation and the minimum stable operating power of a single power generation module; When the action to be performed is a power reduction action, the total minimum stable operating power is determined based on the number of power generation modules currently in operation and the minimum stable operating power. If the adjusted power generation limit is less than the total minimum stable operating power, then the power generation limit is determined to be mismatched with the total minimum stable operating power. When the action to be performed is a power increase action, the number of currently running power generation modules is increased by one to obtain the target number of running modules; The total minimum stable operating power is determined by the product of the target number of operations and the minimum stable operating power. If the adjusted power generation limit is greater than or equal to the total minimum stable operating power, then the power generation limit is determined to be mismatched with the total minimum stable operating power.

[0061] In multi-unit, multi-path grid-connected systems, each generator module has a minimum power threshold to maintain normal operation and voltage stability. If, during the power reduction process of anti-reverse current control, the assigned power limit of the inverter is directly lower than the sum of the minimum power levels that all currently operating generator modules can maintain, it can lead to DC bus voltage instability or frequent inverter restarts. Furthermore, during power increase, if the inverter only increases the power limit of the currently operating generator modules and cannot wake up the non-operating modules, it may reduce the utilization rate of photovoltaic energy.

[0062] Based on this, this embodiment determines whether there is a match between the power generation limit and the physical operating boundary of the power generation module. Specifically, the number of power generation modules currently in operation is denoted as... The minimum stable operating power of a single-channel generator module is The adjusted power generation limit is When the action to be performed is a power reduction action, the inverter calculates the total minimum stable operating power required under the current operating condition (i.e., If it is found that the adjusted power generation limit is no longer sufficient to support the stable operation of the current number of power generation modules (i.e.) If the current number of operating modules is increased by one, it is considered a mismatch, which serves as a prerequisite for triggering the subsequent shutdown of the generator module. When the pending action is a power increase action, the inverter increases the current number of operating modules by one to predict the total minimum stable operating power after adding a new generator module (i.e., the power output of the generator module). If the adjusted power generation limit still exceeds the underlying power requirement after activating the new module (i.e.) If the current power is not met, it is also considered a mismatch, indicating that the current power meets the conditions for activating the power generation module that is not in operation.

[0063] It should be noted that the minimum stable operating power of a single-channel power generation module is jointly determined by the hardware output characteristics of the external photovoltaic panel and the inherent hardware losses of the inverter itself (such as the losses of internal switching devices). This value is usually a fixed constant and is pre-written into the inverter's memory. For example, in practical applications, the inverter's loss in maintaining the internal hardware operation of a single-channel power generation module is approximately 5W. Considering the output characteristics of the external photovoltaic panel, the minimum stable operating power of this single-channel power generation module can preferably be set above 15W. Furthermore, during power upscaling, after determining that the current power generation limit meets the conditions for starting a power generation module that is not in operation, the inverter also needs to further detect whether the output voltage of the external photovoltaic panel corresponding to the power generation module to be started reaches the minimum input voltage allowed by the inverter. The inverter will only formally execute the start-up operation of the corresponding power generation module when this input voltage condition is met, in order to avoid start-up failure or DC-side voltage oscillation due to insufficient front-end voltage.

[0064] As can be seen, this embodiment introduces a bidirectional comparison of the total minimum stable operating power related to the number of online power generation modules, providing accurate boundary conditions for the inverter to adjust the power generation limit and start / stop the power generation modules, thereby further improving the stability and reliability of the grid-connected system.

[0065] As an optional embodiment, adjusting the start / stop state of the power generation module includes: When the action to be performed is a power reduction action, control one of the power generation modules that is currently in operation to stop running; When the action to be performed is a power increase action, control one of the power generation modules that is currently not in operation to start running.

[0066] In grid-connected photovoltaic systems, when power regulation demands exceed the power regulation range of the inverter's currently operating generator modules, simply relying on software-level power limit adjustments is insufficient to meet the actual needs of preventing reverse current or increasing power generation. Furthermore, simultaneously shutting down or starting multiple generator modules at once when the hardware start / stop boundary is triggered could lead to over-regulation and could easily damage the inverter's internal hardware circuitry due to sudden changes in the DC bus voltage.

[0067] Based on this, in this embodiment, when the action to be performed is a power down-adjustment or up-adjustment action, the inverter only controls one generator module to stop or start at a time, that is, only the operating state of a single generator module is changed at a time, thereby achieving a smooth power transition. Specifically, during the shutdown process, the inverter switches from the currently running [module name missing] to the [module name missing]. The power generation modules are shut down one by one. During startup, it is checked sequentially to see if there are any idle modules that meet the startup voltage requirements, and the first eligible module is started. This process ensures that the anti-reverse current command or power increase command can be executed correctly at the hardware level, avoiding over-adjustment and effectively reducing the transient impact on the inverter caused by the hardware state switching of the power generation modules.

[0068] It should be noted that, in order to improve the boundary protection logic under extreme conditions, the inverter will also consider the number of generator modules currently in operation when performing power regulation. Perform a judgment. If the current action to be executed is a power reduction action, then when the judgment... When the value is 0, it indicates that all power generation modules connected to the inverter have been turned off, and there is no room for further power reduction. The inverter will directly end the adjustment of the current control cycle and wait for the next control cycle to reacquire the grid connection point power. If the current action to be executed is a power increase action, when it is determined that... When the value is 0, it indicates that the inverter is in a completely standby state. The inverter will directly control the generator module with the lowest priority number connected to it to start running and end the adjustment of the current control cycle in order to quickly establish a basic generator response.

[0069] As can be seen, this embodiment effectively improves the stability of the inverter's internal circuitry and the lifespan of the power generation module by controlling the start-stop of each circuit according to priority order.

[0070] As an optional embodiment, when the action to be performed is a power reduction action, after adjusting the inverter's power generation limit based on the action to be performed, the method further includes: The single-channel power limit of each power generation module currently in operation is determined based on the power generation limit after inverter adjustment. Each power generation module is controlled based on a single-path power limit.

[0071] Considering that in the actual operation of photovoltaic grid-connected systems, inverters typically integrate multiple independent power generation modules, it is necessary to coordinate the operation of each power generation module to prevent some power generation modules from maintaining full load output while the rest of the power generation modules hardly need to exert any power.

[0072] Based on this, this embodiment provides a power allocation method refined to the hardware level. Specifically, after the inverter updates the overall power generation limit, it can further calculate downwards, reasonably allocating the power generation limit to each currently operating power generation module, and calculating the corresponding single-channel power limit. Furthermore, the inverter can independently adjust the output power of each power generation module based on this single-channel power limit. This process effectively increases the accuracy of the control process and prevents individual power generation modules from being damaged due to overload.

[0073] It should be noted that those skilled in the art can set the specific allocation method for the single-channel power limit of each power generation module according to actual operating conditions. For example, an equal-distribution calculation method can be used, where the limit of the total power generation of the unit after inverter adjustment is recorded as... The number of power generation modules currently in operation is Then calculate the single-path power limit allocated to each power generation module. The formula is: ; Based on the above calculations, the inverter can assign the same limit to each currently operating power generation module. Furthermore, considering the potential differences in sunlight conditions for the photovoltaic panels connected to different power generation modules, a weighted allocation method can also be used. This involves pre-setting the weights of each power generation module within the inverter to proportionally adjust the power generation limit. Perform calculations and allocations.

[0074] As can be seen, this embodiment achieves more precise power control by setting a secondary allocation after the overall power limit, which can effectively improve the control accuracy and long-term operational reliability of the grid-connected system.

[0075] In summary, the inverter control method provided by this invention achieves the anti-reverse current function of multi-machine, multi-channel photovoltaic inverters through distributed collaborative regulation. The aforementioned anti-reverse current power control function only requires the meter to broadcast the real-time power of the grid connection point to all inverters, and the inverters achieve turn-by-turn control through pre-configured different response delays. Specifically, this method uses response delays to adjust the upper and lower limits of the power generation capacity of multi-machine, multi-channel photovoltaic inverters, and to start and stop a certain power generation module according to a predetermined priority. On the one hand, when power reverse current occurs in the grid-connected system, the inverter with the highest number among the online power generation inverters in the grid-connected system begins to reduce its power, while the remaining inverters continue to maintain maximum power generation until it falls below the minimum power threshold for stable operation, after which they shut down. The remaining online power generation inverter with the highest number then takes over the regulation task, unaffected by communication failures or maintenance plans. On the other hand, when the load of the grid-connected system increases and there is a power flow greater than the forward flow, the inverter with the smallest number is checked in turn to check whether there is a reverse flow power control limit. If there is, the power generation limit of the whole machine is adjusted upward until all online inverters are released from the reverse flow control limit.

[0076] The present invention also provides an inverter control device, such as... Figure 6 As shown, Figure 6 A structural diagram of an inverter control device provided by the present invention. The inverter control device includes: Memory 21 is used to store computer programs; The processor 22 is configured to execute a computer program to implement the steps of the inverter control method as described in any of the embodiments above.

[0077] For a description of the inverter control device provided by the present invention, please refer to the embodiments of the inverter control method described above, which will not be repeated here.

[0078] The present invention also provides an inverter, such as Figure 7 As shown, Figure 7 This is a structural diagram of an inverter provided by the present invention. The inverter includes an inverter body 31 and an inverter control device 32 as described above; the inverter body 31 is connected to the inverter control device 32.

[0079] For a description of the inverter provided by this invention, please refer to the embodiments of the inverter control method described above, which will not be repeated here.

[0080] It should be noted that, in this specification, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0081] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An inverter control method, characterized in that, An inverter is used in a grid-connected system, wherein each inverter is connected to the power grid and a multi-generation module, and the inverter control method includes: Obtain the current power at the grid connection point where the inverter is connected to the power grid; Based on the current power, the action to be performed is determined, including a power reduction action and a power increase action; The timing of its own action is determined based on the preset priority of the inverter; wherein, the order of the action triggering timing is positively correlated with the priority of the inverter. When the action triggering time is reached, the power generation limit of the inverter is adjusted based on the action to be executed; When the adjusted power generation limit does not match the total minimum stable operating power of the currently connected power generation modules, the start / stop status of the power generation modules is adjusted.

2. The inverter control method as described in claim 1, characterized in that, Based on the current power, determine the action to be performed, including: The current power is compared with the preset lower trigger power threshold and the preset upper trigger power threshold; If the current power is less than or equal to the power reduction trigger threshold, the action to be performed is determined to be the power reduction action; If the current power is greater than the power increase trigger threshold, the action to be executed is determined to be the power increase action.

3. The inverter control method as described in claim 1, characterized in that, The inverter is assigned a unique priority number. When the action to be performed is a power increase action, the smaller the priority number, the higher the priority of the inverter. When the action to be performed is a power decrease action, the larger the priority number, the higher the priority of the inverter. The timing of its own action is determined based on the preset priority of the inverter, including: When the action to be performed is a power reduction action, determine the difference between the total number of inverters in the grid-connected system and their own priority number; A power reduction counting threshold is determined based on the difference, and the magnitude of the power reduction counting threshold is positively linearly correlated with the difference. When the action to be performed is a power increase action, the power increase count threshold is determined based on its own priority number, and the power increase count threshold is positively linearly correlated with the priority number.

4. The inverter control method as described in claim 3, characterized in that, Determining when the inverter reaches the trigger point for the action includes: When the action to be performed is a power reduction action, the current boost power count value of the inverter is cleared to zero; Increment the current power reduction count value of the inverter by 1 to obtain the new current power reduction count value; wherein, the initial value of the power reduction count value is 0; When a new power reduction count value reaches the power reduction count threshold, the timing for triggering the action is determined. When the action to be performed is a power increase action, the current power reduction count value of the inverter is cleared to zero; The current power boost count value of the inverter is incremented by 1 to obtain the new current power boost count value; wherein the initial value of the power boost count value is 0; When the new current power boost count value reaches the power boost count threshold, the new current power boost count value is cleared to zero, thus determining the timing for triggering the action.

5. The inverter control method as described in claim 1, characterized in that, Adjusting the inverter's power generation limit based on the action to be performed includes: When the action to be performed is a power reduction action, the current power generation limit of the inverter is subtracted from the preset power reduction step size to obtain the adjusted power generation limit. When the action to be performed is a power increase action, the current power generation limit of the inverter is added to a preset power increase step size to obtain the adjusted power generation limit.

6. The inverter control method as described in claim 1, characterized in that, Determining whether the adjusted power generation limit matches the total minimum stable operating power of the currently connected power generation modules includes: Obtain the number of the power generation modules currently in operation and the minimum stable operating power of a single power generation module; When the action to be performed is a power reduction action, the total minimum stable operating power is determined based on the number of the power generation modules currently in operation and the minimum stable operating power. If the adjusted power generation limit is less than the total minimum stable operating power, then the power generation limit is determined to be mismatched with the total minimum stable operating power. When the action to be performed is a power increase action, the number of the power generation modules currently in operation is increased by one to obtain the target number of operating modules; The total minimum stable operating power is determined based on the product of the target number of operations and the minimum stable operating power. If the adjusted power generation limit is greater than or equal to the total minimum stable operating power, then the power generation limit is determined to be mismatched with the total minimum stable operating power.

7. The inverter control method as described in claim 6, characterized in that, Adjusting the start / stop status of the power generation module includes: When the action to be performed is a power reduction action, one of the power generation modules currently in operation is controlled to stop running; When the action to be performed is a power increase action, control one of the power generation modules that is currently not in operation to start running.

8. The inverter control method according to any one of claims 1 to 7, characterized in that, When the action to be performed is a power reduction action, after adjusting the inverter's power generation limit based on the action to be performed, the method further includes: The single-channel power limit of each power generation module currently in operation is determined based on the power generation limit after the inverter is adjusted. Each power generation module is controlled based on the single-channel power limit.

9. An inverter control device, characterized in that, include: Memory, used to store computer programs; A processor for executing the computer program to implement the steps of the inverter control method as described in any one of claims 1 to 8.

10. An inverter, characterized in that, It includes an inverter body and an inverter control device as described in claim 9; the inverter body is connected to the inverter control device.

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