Control method and device of inverter power supply system and inverter power supply system

Abstract

The invention provides a control method and device of an inverter power supply system and the inverter power supply system. The inverter power supply system comprises at least two inverters which are connected in parallel, the direct current end of each inverter is connected with a corresponding battery, and the method comprises the following steps: obtaining the current dischargeable capacity and chargeable capacity of the battery connected with the inverter and the average dischargeable capacity and the average chargeable capacity of the inverter power supply system; and adjusting a preset droop curve of the inverter to obtain a target droop curve, thereby controlling operation of the inverter according to the target droop curve. According to the technical scheme, the active power of each inverter can be distributed according to the dischargeable capacity and the chargeable capacity of the battery of each inverter, so that the situation that the corresponding inverter exits in advance due to the fact that the battery with the low dischargeable capacity is exhausted in advance is avoided, and then the battery utilization rate of the inverter power supply system is improved.

Description

Technical Field

[0001] This application relates to the field of power electronics, and more specifically, to a control method, apparatus, and inverter power supply system for an inverter power supply system. Background Technology

[0002] When supplying power to a load through an inverter power supply system consisting of multiple inverters connected in parallel, the bidirectional energy flow capability of the inverters can typically be used to charge and discharge the batteries connected to the DC terminals of the inverters. For example, the load can be discharged through the batteries connected to each inverter, and the batteries connected to each inverter can be charged through the photovoltaic modules connected to the inverters.

[0003] However, during the operation of an inverter power supply system, the remaining state of charge (SOC) of the batteries connected to each inverter varies, and the energy output from the photovoltaic modules cannot prioritize charging batteries with lower remaining capacity. Therefore, batteries with low remaining capacity will deplete their charge prematurely as they continue to supply power to the load, causing the corresponding inverter to shut down early. This results in a decrease in the total output power of the inverter power supply system. When the total output power drops below the load, the inverter power supply system will trigger an overload error due to insufficient output power and stop operating. Consequently, batteries with relatively sufficient remaining capacity in the inverter power supply system cannot continue to supply power to the load, leading to relatively low battery energy utilization in the inverter power supply system. Summary of the Invention

[0004] This application provides a control method, device, and inverter power supply system for an inverter power supply system. The various aspects involved in this application will be described below.

[0005] Firstly, a control method for an inverter power supply system is provided. The inverter power supply system includes at least two inverters connected in parallel. The DC terminal of each inverter is connected to a corresponding battery, and the AC terminal of each inverter supplies power to the load through a parallel connection point. For each inverter, the method includes: obtaining the current discharge capacity and rechargeable capacity of the battery connected to the inverter, the average discharge capacity and average rechargeable capacity of the inverter power supply system, wherein the average discharge capacity is the average of the current discharge capacity of the batteries connected to each inverter, and the average rechargeable capacity is the average of the current rechargeable capacity of the batteries connected to each inverter; adjusting a preset droop curve of the inverter based on the average discharge capacity, average rechargeable capacity, discharge capacity, and rechargeable capacity to obtain a target droop curve, wherein the droop curve reflects the negative correlation between active power and frequency; and controlling the inverter operation according to the target droop curve.

[0006] In one possible implementation, the inverter's preset droop curve is adjusted to obtain a target droop curve based on the average dischargeable capacity, average rechargeable capacity, dischargeable capacity, and rechargeable capacity. This includes: adjusting the discharge droop slope of the preset droop curve to a target discharge droop slope based on the average dischargeable capacity and dischargeable capacity, where the discharge droop slope is the slope corresponding to the positive half-axis of the active power axis; and adjusting the charging droop slope of the preset droop curve to a target charging droop slope based on the average rechargeable capacity and rechargeable capacity, where the charging droop slope is the slope corresponding to the negative half-axis of the active power axis.

[0007] In one possible implementation, at least one of the inverters has its DC terminal connected to a corresponding photovoltaic module. The method further includes: obtaining the photovoltaic input power corresponding to the inverter, where the photovoltaic input power is zero when the inverter is not connected to the photovoltaic module; adjusting a preset droop curve of the inverter based on the average discharge capacity, average rechargeable capacity, discharge capacity, and rechargeable capacity to obtain a target droop curve; and further includes: adjusting the intercept of the preset droop curve with adjusted slope based on the average discharge capacity, average rechargeable capacity, discharge capacity, rechargeable capacity, and photovoltaic input power corresponding to the inverter when the photovoltaic input power corresponding to the inverter is not zero.

[0008] In one possible implementation, adjusting the discharge droop slope of a preset droop curve to a target discharge droop slope based on the average dischargeable capacity and the dischargeable capacity includes: determining a target discharge droop slope based on the average dischargeable capacity and the dischargeable capacity; adjusting the discharge droop slope of the preset droop curve to the target discharge droop slope; and adjusting the charging droop slope of the preset droop curve to a target charging droop slope based on the average rechargeable capacity and the rechargeable capacity includes: determining a target charging droop slope based on the average rechargeable capacity and the rechargeable capacity; and adjusting the charging droop slope of the preset droop curve to the target charging droop slope.

[0009] In one possible implementation, the intercept of a preset droop curve with an adjusted slope is adjusted based on the average dischargeable capacity, average rechargeable capacity, dischargeable capacity, rechargeable capacity, and photovoltaic input power corresponding to the inverter. This includes: determining an intercept adjustment value based on the average dischargeable capacity, average rechargeable capacity, dischargeable capacity, rechargeable capacity, and photovoltaic input power corresponding to the inverter; and adjusting the intercept of the preset droop curve with an adjusted slope based on the intercept adjustment value.

[0010] In one possible implementation, obtaining the current discharge capacity and rechargeable capacity of the battery connected to the inverter includes: obtaining the current remaining capacity of the battery connected to the inverter; determining the discharge capacity based on the remaining capacity, the minimum discharge capacity of the battery, and the battery voltage, wherein the minimum discharge capacity is the remaining capacity corresponding to when the battery can no longer discharge; and determining the rechargeable capacity based on the remaining capacity, the maximum charging capacity of the battery, and the battery voltage, wherein the maximum charging capacity is the remaining capacity corresponding to when the battery can no longer be charged.

[0011] In one possible implementation, each inverter in the inverter power supply system includes a main inverter. The average dischargeable capacity is determined by the main inverter based on the current dischargeable capacity of the batteries connected to each inverter. The average rechargeable capacity is also determined by the main inverter based on the current rechargeable capacity of the batteries connected to each inverter. The method further includes sending the dischargeable capacity and rechargeable capacity to the main inverter.

[0012] Secondly, a control device for an inverter power supply system is provided. The inverter power supply system includes at least two inverters connected in parallel. The DC terminal of each inverter is connected to a corresponding battery, and the AC terminal of each inverter supplies power to the load through a parallel connection point. For each inverter, the device includes: a processing module, used to obtain the current discharge capacity and rechargeable capacity of the battery connected to the inverter, the average discharge capacity and average rechargeable capacity of the inverter power supply system, wherein the average discharge capacity is the average of the current discharge capacity of the batteries connected to each inverter, and the average rechargeable capacity is the average of the current rechargeable capacity of the batteries connected to each inverter; and adjusting a preset droop curve of the inverter based on the average discharge capacity, average rechargeable capacity, discharge capacity, and rechargeable capacity to obtain a target droop curve, wherein the droop curve reflects the negative correlation between active power and frequency; and a control module, used to control the operation of the inverter according to the target droop curve.

[0013] In one possible implementation, the processing module is specifically configured to adjust the discharge droop slope of a preset droop curve to a target discharge droop slope based on the average dischargeable capacity and the dischargeable capacity, wherein the discharge droop slope is the slope of the droop curve corresponding to the positive half-axis of the active power axis; and to adjust the charging droop slope of a preset droop curve to a target charging droop slope based on the average rechargeable capacity and the rechargeable capacity, wherein the charging droop slope is the slope of the droop curve corresponding to the negative half-axis of the active power axis.

[0014] In one possible implementation, the DC terminal of at least one of the inverters is also connected to the corresponding photovoltaic module. The processing module is further configured to obtain the photovoltaic input power corresponding to the inverter. When the inverter is not connected to the photovoltaic module, the corresponding photovoltaic input power is zero. When the photovoltaic input power corresponding to the inverter is not zero, the intercept of a preset droop curve with an adjusted slope is adjusted based on the average discharge capacity, average rechargeable capacity, discharge capacity, rechargeable capacity, and photovoltaic input power corresponding to the inverter.

[0015] In one possible implementation, the processing module is specifically configured to: determine a target discharge droop slope based on the average dischargeable capacity and the dischargeable capacity; adjust the discharge droop slope of a preset droop curve to the target discharge droop slope; determine a target charging droop slope based on the average rechargeable capacity and the rechargeable capacity; and adjust the charging droop slope of a preset droop curve to the target charging droop slope.

[0016] In one possible implementation, the processing module is specifically configured to determine the intercept adjustment value based on the average dischargeable capacity, average rechargeable capacity, dischargeable capacity, rechargeable capacity, and photovoltaic input power corresponding to the inverter; and adjust the intercept of the preset droop curve with adjusted slope based on the intercept adjustment value.

[0017] In one possible implementation, the processing module is specifically configured to obtain the current remaining capacity of the battery connected to the inverter; determine the dischargeable capacity based on the remaining capacity, the minimum discharge capacity of the battery, and the battery voltage, wherein the minimum discharge capacity is the remaining capacity corresponding to when the battery can no longer discharge; and determine the rechargeable capacity based on the remaining capacity, the maximum charging capacity of the battery, and the battery voltage, wherein the maximum charging capacity is the remaining capacity corresponding to when the battery can no longer be charged.

[0018] In one possible implementation, each inverter in the inverter power supply system includes a main inverter. The average dischargeable capacity is determined by the main inverter based on the current dischargeable capacity of the batteries connected to each inverter. The average rechargeable capacity is also determined by the main inverter based on the current rechargeable capacity of the batteries connected to each inverter. The processing module is further configured to send the dischargeable capacity and rechargeable capacity to the main inverter.

[0019] Thirdly, an inverter power supply system is provided, comprising: at least two inverters connected in parallel, wherein the DC terminal of each inverter is connected to a corresponding battery, the AC terminal of each inverter supplies power to the load through a parallel connection point, and each inverter performs the method described in the first aspect or any possible implementation thereof.

[0020] Fourthly, a computer-readable storage medium is provided, on which a computer program is stored, the computer program including program instructions, which, when executed by each inverter of the inverter power supply system, perform the method described in the first aspect or any possible implementation thereof.

[0021] In this embodiment, the droop curves of each inverter in the inverter power supply system can be adjusted based on the current discharge and rechargeable capacities of the batteries connected to each inverter, as well as the average discharge and average rechargeable capacities of the inverter power supply system. This allows each inverter to operate according to the adjusted target droop curve. Consequently, the discharge power of each inverter discharging to the load through the batteries can be distributed according to the discharge capacity of the batteries connected to it. Therefore, the inverter corresponding to the battery with the higher discharge capacity outputs more power to the load, and more power from the photovoltaic modules flows to the battery with the higher rechargeable capacity (i.e., the battery with the lower discharge capacity). Thus, the battery with the higher discharge capacity in the inverter power supply system can output more power, while the battery with the lower discharge capacity can output less power, balancing the energy output of the batteries connected to each inverter and slowing down the depletion time of the batteries with lower discharge capacities. This prevents the corresponding inverter from prematurely shutting down due to the premature depletion of batteries with lower discharge capacities. Furthermore, this prevents the total output power of the inverter power supply system from decreasing due to the premature shutdown of some inverters, ensuring that the inverter power supply system does not stop operating due to overload error caused by the total output power dropping below the load. This allows each battery in the inverter power supply system to continuously supply power to the load, thereby improving the battery energy utilization rate of the inverter power supply system. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments or related technologies of this application, the accompanying drawings used in the description of the embodiments or related technologies will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 This is a schematic diagram of the inverter power supply system provided in the embodiments of this application;

[0024] Figure 2 This is a flowchart illustrating the control method of the inverter power supply system provided in the embodiments of this application;

[0025] Figure 3 This is one of the schematic diagrams of the drooping curve provided in the embodiments of this application;

[0026] Figure 4 This is a second schematic diagram of the drooping curve provided in the embodiments of this application;

[0027] Figure 5 This is the third schematic diagram of the drooping curve provided in the embodiments of this application;

[0028] Figure 6 This is a schematic diagram of the control device of the inverter power supply system provided in the embodiments of this application. Detailed Implementation

[0029] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art based on the embodiments of this application are within the scope of protection of this application.

[0030] When supplying power to a load through an inverter power supply system consisting of multiple inverters connected in parallel, the bidirectional energy flow capability of the inverters can typically be used to charge and discharge the batteries connected to the DC terminals of the inverters. For example, the load can be discharged through the batteries connected to each inverter, and the batteries connected to each inverter can be charged through the photovoltaic modules connected to the inverters.

[0031] However, during the operation of an inverter power supply system, the remaining state of charge (SOC) of the batteries connected to each inverter varies, and the energy output from the photovoltaic modules cannot prioritize charging batteries with lower remaining capacity. Therefore, batteries with low remaining capacity will deplete their charge prematurely as they continue to supply power to the load, causing the corresponding inverter to shut down early. This results in a decrease in the total output power of the inverter power supply system. When the total output power drops below the load, the inverter power supply system will trigger an overload error due to insufficient output power and stop operating. Consequently, batteries with relatively sufficient remaining capacity in the inverter power supply system cannot continue to supply power to the load, leading to relatively low battery energy utilization in the inverter power supply system.

[0032] Therefore, to address the aforementioned problems, this application provides a control method for an inverter power supply system. This method adjusts the droop curves of each inverter in the inverter power supply system based on the current discharge and rechargeable capacities of the batteries connected to each inverter, as well as the average discharge and rechargeable capacities of the inverter power supply system. This allows each inverter to operate according to the adjusted target droop curve. This ensures that the discharge power of each inverter discharging to the load through the batteries is distributed according to the discharge capacity of the batteries connected to it. Consequently, the inverter corresponding to the battery with the higher discharge capacity outputs more power to the load, and more power from the photovoltaic modules flows to the battery with the higher rechargeable capacity (i.e., the battery with the lower discharge capacity). Thus, the battery with the higher discharge capacity in the inverter power supply system can output more power, while the battery with the lower discharge capacity can output less power, balancing the energy output of the batteries connected to each inverter and slowing down the depletion time of the batteries with lower discharge capacities. This prevents the premature depletion of batteries with lower discharge capacities, which could lead to the premature shutdown of the corresponding inverter. Furthermore, this prevents the total output power of the inverter power supply system from decreasing due to the premature shutdown of some inverters, ensuring that the inverter power supply system does not stop operating due to overload error caused by the total output power dropping below the load. This allows each battery in the inverter power supply system to continuously supply power to the load, thereby improving the battery energy utilization rate of the inverter power supply system.

[0033] The droop curve, specifically the active power-frequency droop curve, illustrates the negative correlation between active power and frequency, enabling droop control of inverters. In inverter power supply systems with multiple inverters operating in parallel, droop control based on the active power-frequency droop curve can automatically allocate the active power of each inverter according to its droop characteristics, achieving system power balance. For example, when the inverter power supply system is in steady state, all inverters operate at the same frequency (the system frequency), and the active power of each inverter can be determined according to the active power-frequency droop curve based on the system frequency. The active power of an inverter refers to the power it actually performs during operation, providing effective energy to the external environment; it is one of the core indicators for measuring the inverter's power supply capability.

[0034] In this embodiment, the control method for the inverter power supply system can be applied to a corresponding inverter power supply system. This inverter power supply system may include at least two inverters connected in parallel. The DC terminal of each inverter is connected to a corresponding battery, and the AC terminals of each inverter supply power to the load through a parallel connection point. The inverters can be controlled in parallel using a master-slave configuration, with one master inverter providing overall control. However, in practical applications, other parallel control methods can also be used, which are not limited here. Optionally, in practical applications, at least one DC terminal of each inverter in the inverter power supply system can also be connected to a corresponding photovoltaic module, so that the electrical energy output from the photovoltaic module can charge the batteries connected to each inverter.

[0035] For example, taking an inverter power supply system consisting of two inverters as an example, such as Figure 1 As shown, the inverter power supply system may include a first inverter and a second inverter connected in parallel. The first inverter and the second inverter jointly supply power to the load. The first inverter may be connected to a first battery and a first photovoltaic module, respectively, and the second inverter may be connected to a second battery. The first battery can discharge through the first inverter to supply power to the load, and the second battery can discharge through the second inverter to supply power to the load. The energy from the first photovoltaic module can be input to the first inverter as photovoltaic input power, thereby charging the first battery through the first inverter, and also inputting energy through the first inverter to the second inverter to charge the second battery through the second inverter.

[0036] Taking the inverter power supply system as an example of parallel control of each inverter using a master-slave configuration, one of the first inverter and the second inverter can be the master inverter, and the other can be the slave inverter. For example, the first inverter can be used as the master inverter, and the second inverter can be used as the slave inverter.

[0037] It should be noted that in practical applications, inverter power supply systems may also include other necessary or required devices besides those listed above, and there are no restrictions here.

[0038] In the embodiments of this application, the control method for the inverter power supply system provided in this application can be executed separately by each inverter in the inverter power supply system. For example, each inverter can execute the method by its assigned controller.

[0039] The control method of an inverter power supply system provided in the embodiments of this application will be described in detail below with reference to the accompanying drawings.

[0040] The control method for the inverter power supply system provided in the embodiments of this application is executed for each of the inverters, such as... Figure 2 As shown, the control method of an inverter power supply system provided in this application embodiment may include the following S201-S203.

[0041] S201. Obtain the current discharge capacity and rechargeable capacity of the battery connected to the inverter, as well as the average discharge capacity and average rechargeable capacity of the inverter power supply system.

[0042] The average dischargeable capacity is the average of the current dischargeable capacities of the batteries connected to each inverter, and the average rechargeable capacity is the average of the current rechargeable capacities of the batteries connected to each inverter.

[0043] For example, the current discharge capacity and rechargeable capacity of the battery connected to the inverter can be obtained by the inverter acquiring the current remaining capacity (State of Charge, SOC) of its connected battery, and then determining the discharge capacity based on the battery's current SOC, minimum discharge capacity, and voltage; or determining the rechargeable capacity based on the battery's current SOC, maximum charge capacity, and voltage. The minimum discharge capacity is the SOC at which the battery can no longer discharge (e.g., 5%, 10%), and the maximum charge capacity is the SOC at which the battery can no longer charge (e.g., 95%, 100%). The minimum discharge capacity and maximum charge capacity can be preset according to actual conditions.

[0044] For example, the above-mentioned discharge capacity can be calculated using the following formula:

[0045] SOC di =(SOC―SOC) min V bat

[0046] Among them, SOC di SOC is the discharge capacity of the battery connected to inverter i, and SOC is the current remaining capacity of the battery connected to inverter i. min V represents the minimum discharge capacity of the battery connected to inverter i. bat This is the voltage of the battery connected to inverter i.

[0047] For example, the above-mentioned rechargeable capacity can be calculated using the following formula:

[0048] SOC ci =(SOC) max —SOC)V bat

[0049] Among them, SOC ci SOC is the rechargeable capacity of the battery connected to inverter i, and SOC is the current remaining capacity of the battery connected to inverter i. max V represents the maximum charging capacity of the battery connected to inverter i. batThis is the voltage of the battery connected to inverter i.

[0050] For example, the average discharge capacity and average rechargeable capacity of the inverter power supply system can be obtained by each inverter sending the rechargeable and discharge capacities of its connected batteries to each other, so that the inverter can calculate the average discharge capacity and average rechargeable capacity based on the rechargeable and discharge capacities of each inverter.

[0051] Of course, if the inverters in the inverter power supply system adopt a master-slave parallel control, meaning each inverter includes a master inverter, then each inverter can send the rechargeable and dischargeable capacities of its connected batteries to the master inverter. The master inverter then calculates the average dischargeable capacity and average rechargeable capacity based on the corresponding rechargeable and dischargeable capacities of each inverter. Thus, each inverter can obtain the average dischargeable capacity and average rechargeable capacity from the master inverter.

[0052] Data exchange between inverters can be achieved through communication connections between them, such as communication connections using the Controller Area Network (CAN) protocol.

[0053] As an example, the average dischargeable capacity can be calculated using the following formula:

[0054]

[0055] Among them, SOC davg For average discharge capacity, SOC di Let n be the discharge capacity of the battery connected to inverter i, and n be the number of inverters in the inverter power supply system.

[0056] Accordingly, the average rechargeable capacity can be calculated using the following formula:

[0057]

[0058] Among them, SOC cavg For average rechargeable capacity, SOC ci n represents the rechargeable capacity of the battery connected to inverter i, and n represents the number of inverters in the inverter power supply system.

[0059] S202. Based on the average dischargeable capacity, average rechargeable capacity, dischargeable capacity, and rechargeable capacity, adjust the preset droop curve of the inverter to obtain the target droop curve.

[0060] The droop curve can be a power-frequency droop curve, reflecting the negative correlation between active power and frequency. The frequency of the droop curve decreases as active power increases. Specifically, the region corresponding to the positive half-axis of the active power axis represents battery discharge through the inverter, while the region corresponding to the negative half-axis represents battery charging through the inverter. Therefore, the slope of the droop curve corresponding to the positive half-axis of the active power axis can be called the discharge droop slope, and the slope corresponding to the negative half-axis can be called the charging droop slope.

[0061] In this embodiment of the application, the preset droop curve can be a droop curve that is preset for each inverter in the inverter power supply system, and each inverter operates by default using the preset droop curve.

[0062] A preset droop curve is typically a straight line with a fixed slope; that is, the slope of the discharge droop curve and the slope of the charge droop curve are usually equal, i.e., the same value. For example, a preset droop curve might be defined as f = K × P + 50 (where f is the inverter output frequency, P is the inverter active power, K is the curve slope, and 50 is the rated frequency). Figure 3 The diagram shown is a schematic of a preset droop curve. According to this preset droop curve, when the active power of the inverter increases, the corresponding frequency decreases accordingly.

[0063] For example, adjusting the preset droop curve of the inverter based on the average dischargeable capacity, average rechargeable capacity, dischargeable capacity, and rechargeable capacity can be achieved by adjusting the discharge droop slope of the preset droop curve to the target discharge droop slope based on the average dischargeable capacity and dischargeable capacity; and adjusting the charging droop slope of the preset droop curve to the target charging droop slope based on the average rechargeable capacity and rechargeable capacity.

[0064] In some possible implementations, the discharge droop slope of the preset droop curve is adjusted to the target discharge droop slope based on the average dischargeable capacity and the dischargeable capacity. This can be achieved by first determining the target discharge droop slope based on the average dischargeable capacity and the dischargeable capacity, and then adjusting the discharge droop slope of the preset droop curve to the target discharge droop slope.

[0065] For example, the target discharge droop slope can be calculated using the following formula:

[0066]

[0067] Among them, K di SOC is the target discharge droop slope corresponding to inverter i. davg For average discharge capacity, SOC di K represents the discharge capacity of the battery connected to inverter i. stThe discharge droop slope is the preset droop curve.

[0068] In some possible implementations, the charging droop slope of the preset droop curve is adjusted to the target charging droop slope based on the average rechargeable capacity and the rechargeable capacity. This can be achieved by first determining the target charging droop slope based on the average rechargeable capacity and the rechargeable capacity, and then adjusting the charging droop slope of the preset droop curve to the target charging droop slope.

[0069] For example, the target charging droop slope can be calculated using the following formula:

[0070]

[0071] Among them, K ci The target charging droop slope corresponding to inverter i, SOC cavg For average rechargeable capacity, SOC ci K represents the rechargeable capacity of the battery connected to inverter i. st The charging droop slope is the preset droop curve.

[0072] Based on the above example, the charging droop slope and discharging droop slope of the preset droop curve can be adjusted separately. For example, as... Figure 4 As shown, the dashed line is the preset droop curve, and the solid line is the droop curve after the slope has been adjusted. The adjusted droop curves correspond to different slopes on the positive and negative half-axis of the active power axis, respectively.

[0073] In some possible implementations, the DC terminal of at least one of the inverters in the inverter power supply system can also be connected to the corresponding photovoltaic module so that the electrical energy output by the photovoltaic module can charge the batteries connected to each inverter. In this case, the control method of the inverter power supply system provided in this application embodiment can also be combined with the photovoltaic input power input from the photovoltaic module to the corresponding inverter to adjust the droop curve of the inverter, so as to distribute the energy of the photovoltaic module proportionally according to the rechargeable capacity of each battery, thereby prioritizing higher power charging of batteries with higher rechargeable capacity (i.e., lower SOC) and increasing the discharge time of batteries with higher rechargeable capacity.

[0074] For example, in this embodiment, each inverter can also acquire its corresponding photovoltaic input power. The photovoltaic input power acquired by an inverter without connected photovoltaic modules is zero. Therefore, the inverter can adjust the intercept of a preset droop curve (i.e., a preset droop curve with adjusted discharge and charging droop slopes according to the aforementioned embodiments) based on the average discharge capacity, average chargeable capacity, discharge capacity, chargeable capacity, and the photovoltaic input power corresponding to the inverter.

[0075] For example, the inverter can first determine the intercept adjustment value based on the average discharge capacity, average chargeable capacity, discharge capacity, chargeable capacity, and the photovoltaic input power corresponding to the inverter, and then adjust the intercept of the preset droop curve with adjusted slope according to the intercept adjustment value.

[0076] For example, the intercept adjustment value can be calculated using the following formula:

[0077]

[0078] Among them, f bi The intercept adjustment value corresponding to inverter i, SOC ci The rechargeable capacity of the battery connected to inverter i, SOC cavg For average rechargeable capacity, SOC davg For average discharge capacity, SOC di P represents the discharge capacity of the battery connected to inverter i. pvi Let be the photovoltaic input power corresponding to inverter i, and n be the number of inverters in the inverter power supply system. Based on this formula, for inverters without connected photovoltaic modules, and inverters where the photovoltaic modules are not outputting energy, since their corresponding photovoltaic input power is zero, the corresponding intercept adjustment value f is... bi If it is zero, then the intercept of its sag curve will not be adjusted.

[0079] The intercept adjustment value calculated using this formula can be used to adjust the droop curve intercept, allowing the inverter connected to photovoltaic modules to discharge and use the photovoltaic input power to charge all other inverters. Even when a load is connected and other inverters are discharging, they can still be controlled according to the charging droop slope. This way, except for the inverter connected to photovoltaic modules which is controlled according to the discharging droop slope, all other inverters are controlled according to the charging droop slope, resulting in lower control complexity. Thus, the excess photovoltaic input power of the inverter connected to photovoltaic modules is only used to charge the batteries connected to other inverters. Although the inverters are actually discharging, it can be understood that the energy of the photovoltaic modules is used for charging, and the batteries then continue to discharge according to their capacity, resulting in a cumulative effect of discharge. The energy of the photovoltaic modules does not participate in the energy balance of battery discharge.

[0080] As an example, adjusting the intercept of the corresponding sag curve based on the intercept adjustment value can be done by adjusting the horizontal intercept of the corresponding sag curve based on the intercept adjustment value. For example, taking the adjustment of the intercept of a preset sag curve (f = K × P + 50) as an example, ... Figure 5 As shown, the dashed line represents the preset sag curve (f = K × P + 50), and the solid line represents the sag curve after adjusting the intercept (f = K × (Pf)). bi(+50). Of course, in practical applications, the intercept adjustment value can also be converted according to the slope of the droop curve, so as to adjust the vertical intercept of the droop curve. There are no restrictions here.

[0081] In practical applications, based on the aforementioned method of adjusting the intercept of the corresponding droop curve according to the intercept adjustment value, the target droop curve obtained after adjusting the intercept of the preset droop curve with adjusted slope according to the intercept adjustment value can be represented as an adjustment of the preset droop curve based on the target discharge droop slope, the target charging droop curve, and the intercept adjustment value. For example, taking the preset droop curve as f = K × P + 50, the expression for the target droop curve corresponding to inverter i in the region corresponding to the positive half-axis of the active power axis can be f = K di ×(Pf bi The expression for the region corresponding to the negative half-axis of the active power axis is f = K + 50. ci ×(Pf bi )+50.

[0082] S203. Control the inverter operation according to the target droop curve.

[0083] When the inverter power supply system is in steady state, all inverters in the system maintain the same output frequency (i.e., the system frequency). Therefore, after the inverter's droop curve is adjusted to the target droop curve, the inverter can operate according to the active power corresponding to the system frequency in the target droop curve.

[0084] For example, taking inverter 1 and inverter 2 as examples, where inverter 1 is connected to a photovoltaic module, when the photovoltaic module has zero output (i.e., the photovoltaic input power corresponding to inverter 1 is zero), each inverter can supply power to the load solely through the discharge of its connected battery. At this time, when the inverter power supply system is in steady state, since the frequencies of inverter 1 and inverter 2 are equal and constitute the system frequency, after controlling the inverter operation according to the target droop curve, and combining with the aforementioned formula, the active power of the two inverters satisfies the following relationship:

[0085]

[0086] Among them, SOC d1 P1 is the discharge capacity of inverter 1, P1 is the active power of inverter 1 operating at the system frequency according to the target droop curve, and SOC is the discharge capacity of inverter 1. d2 P2 is the discharge capacity of inverter 2, and P2 is the active power of inverter 2 operating at the system frequency according to the target droop curve.

[0087] After simplifying the above relationship, we can obtain:

[0088]

[0089] Therefore, it can be seen that after operation based on the target droop curve control, the ratio of active power among the inverters is equal to the ratio of the discharge capacities of their connected batteries. Thus, after each inverter operates according to the target droop curve obtained by the method provided in this application embodiment, it can distribute active power according to the discharge capacity of its connected batteries, enabling batteries with higher discharge capacities to discharge at greater power. This balances the discharge rate of batteries with different SOCs, preventing batteries with lower SOCs from prematurely depleting their charge and causing the corresponding inverters to prematurely shut down.

[0090] For example, continuing with inverters 1 and 2, where inverter 1 is connected to photovoltaic (PV) modules, when the PV modules have a certain power output (i.e., the PV input power corresponding to inverter 1 is not zero, while the PV input power corresponding to inverter 2 is zero), inverter 1 can charge the batteries connected to each inverter using the energy input from the PV modules. At this time, when the inverter power supply system is in steady state, since the frequencies of inverter 1 and inverter 2 are equal and equal to the system frequency, after controlling the inverter operation according to the target droop curve, combined with the aforementioned formula, the active power of the two inverters satisfies the following relationship:

[0091]

[0092] Among them, SOC d1 The discharge capacity of inverter 1, SOC c1 P1 is the rechargeable capacity of inverter 1, and P1 is the active power of inverter 1 operating at the system frequency according to the target droop curve. pv1 The photovoltaic input power corresponding to inverter 1, SOC c2 P2 is the rechargeable capacity of inverter 2, and P2 is the active power of inverter 2 operating at the system frequency according to the target droop curve.

[0093] After simplifying the above relationship, we can obtain:

[0094]

[0095] Among them, according to the balance control objective, the photovoltaic input power of The energy needed to charge the battery connected to inverter 1 is required. Therefore, Therefore, based on the above relation, we can obtain

[0096] Therefore, it can be seen that after operating based on the target droop curve, when the photovoltaic modules are outputting energy, the inverter connected to the photovoltaic modules can allocate charging power to each battery according to the proportion of each battery's rechargeable capacity in the total rechargeable capacity. This prioritizes charging batteries with larger rechargeable capacities (i.e., lower SOCs) at high power, preventing batteries with lower SOCs from prematurely depleting their power and causing their corresponding inverters to shut down prematurely.

[0097] Based on the aforementioned control method for the inverter power supply system, the droop curves of each inverter in the inverter power supply system are adjusted according to the current discharge and rechargeable capacities of the batteries connected to each inverter, the average discharge and average rechargeable capacities of the inverter power supply system, and the photovoltaic input power corresponding to each inverter. This ensures that the discharge power of each inverter discharging to the load through the batteries is distributed according to the discharge capacity of the batteries connected to it, and that the power output of the photovoltaic modules is distributed according to the rechargeable capacity of the batteries connected to each inverter. This allows batteries with higher discharge capacities to output more power, and batteries with lower discharge capacities to output less power, thus balancing the energy output of the batteries connected to each inverter and slowing down the depletion time of batteries with lower discharge capacities. This prevents the premature depletion of batteries with lower discharge capacities, which could lead to the premature shutdown of the corresponding inverter. Furthermore, this prevents the total output power of the inverter power supply system from decreasing due to the premature shutdown of some inverters, ensuring that the inverter power supply system does not stop operating due to overload error caused by the total output power dropping below the load. This allows each battery in the inverter power supply system to continuously supply power to the load, thereby improving the battery energy utilization rate of the inverter power supply system.

[0098] The method embodiments of this application have been described in detail above with reference to the accompanying drawings. The apparatus embodiments of this application will now be described in detail. It should be understood that the descriptions of the apparatus embodiments correspond to the descriptions of the method embodiments; therefore, any parts not described in detail can be referred to the foregoing method embodiments.

[0099] This application also provides a control device for an inverter power supply system. The inverter power supply system includes at least two inverters connected in parallel. The DC terminal of each inverter is connected to a corresponding battery, and the AC terminals of each inverter supply power to the load through a parallel connection point. For each inverter, refer to... Figure 6As shown, the device includes: a processing module 601, used to acquire the current discharge capacity and rechargeable capacity of the batteries connected to the inverter, the average discharge capacity and average rechargeable capacity of the inverter power supply system, wherein the average discharge capacity is the average of the current discharge capacity of the batteries connected to each inverter, and the average rechargeable capacity is the average of the current rechargeable capacity of the batteries connected to each inverter; and adjusts the preset droop curve of the inverter according to the average discharge capacity, average rechargeable capacity, discharge capacity, and rechargeable capacity to obtain a target droop curve, wherein the droop curve reflects the negative correlation between active power and frequency; and a control module 602, used to control the operation of the inverter according to the target droop curve.

[0100] In one possible implementation, the processing module 601 is specifically configured to adjust the discharge droop slope of the preset droop curve to a target discharge droop slope based on the average dischargeable capacity and the dischargeable capacity, wherein the discharge droop slope is the slope corresponding to the positive half-axis of the droop curve on the active power axis; and to adjust the charging droop slope of the preset droop curve to a target charging droop slope based on the average rechargeable capacity and the rechargeable capacity, wherein the charging droop slope is the slope corresponding to the negative half-axis of the droop curve on the active power axis.

[0101] In one possible implementation, the DC terminal of at least one of the inverters is also connected to the corresponding photovoltaic module. The processing module 601 is further configured to obtain the photovoltaic input power corresponding to the inverter. When the inverter is not connected to the photovoltaic module, the corresponding photovoltaic input power is zero. When the photovoltaic input power corresponding to the inverter is not zero, the intercept of the preset droop curve with adjusted slope is adjusted according to the average discharge capacity, average rechargeable capacity, discharge capacity, rechargeable capacity, and photovoltaic input power corresponding to the inverter.

[0102] In one possible implementation, the processing module 601 is specifically configured to: determine a target discharge droop slope based on the average dischargeable capacity and the dischargeable capacity; adjust the discharge droop slope of a preset droop curve to the target discharge droop slope; determine a target charging droop slope based on the average rechargeable capacity and the rechargeable capacity; and adjust the charging droop slope of a preset droop curve to the target charging droop slope.

[0103] In one possible implementation, the processing module 601 is specifically used to determine the intercept adjustment value based on the average dischargeable capacity, average rechargeable capacity, dischargeable capacity, rechargeable capacity, and photovoltaic input power corresponding to the inverter; and to adjust the intercept of the preset droop curve with adjusted slope based on the intercept adjustment value.

[0104] In one possible implementation, the processing module 601 is specifically used to obtain the current remaining capacity of the battery connected to the inverter; determine the dischargeable capacity based on the remaining capacity, the minimum discharge capacity of the battery, and the battery voltage, wherein the minimum discharge capacity is the remaining capacity corresponding to when the battery can no longer discharge; and determine the rechargeable capacity based on the remaining capacity, the maximum charging capacity of the battery, and the battery voltage, wherein the maximum charging capacity is the remaining capacity corresponding to when the battery can no longer charge.

[0105] In one possible implementation, each inverter in the inverter power supply system includes a main inverter. The average dischargeable capacity is determined by the main inverter based on the current dischargeable capacity of the batteries connected to each inverter. The average rechargeable capacity is also determined by the main inverter based on the current rechargeable capacity of the batteries connected to each inverter. The processing module 601 is further configured to send the dischargeable capacity and rechargeable capacity to the main inverter.

[0106] This application also provides an inverter power supply system, including: at least two inverters connected in parallel, the DC terminal of each inverter being connected to a corresponding battery, the AC terminal of each inverter supplying power to the load through a parallel connection point, and each inverter performing the method described in any of the preceding embodiments.

[0107] This application also provides a computer-readable storage medium storing a computer program thereon. The computer program includes program instructions, which, when executed by each inverter of the inverter power supply system, perform the method described in any of the preceding embodiments.

[0108] It should be understood that, in the embodiments of this application, determining B based on A does not mean determining B solely based on A; B can also be determined based on A and / or other information.

[0109] It should be understood that in the embodiments of this application, "B corresponding to A" means that B is associated with A, and B can be determined based on A. However, it should also be understood that determining B based on A does not mean that B is determined solely based on A; B can also be determined based on A and / or other information.

[0110] It should be understood that the term "and / or" in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. Additionally, the character " / " in this article generally indicates that the preceding and following related objects have an "or" relationship.

[0111] It should be understood that in the various embodiments of this application, the order of the above-mentioned processes does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0112] In the several embodiments provided in this application, it should be understood that the disclosed systems, apparatuses, and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection between apparatuses or units may be electrical, mechanical, or other forms.

[0113] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0114] In addition, the functional units in the various embodiments of this application can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit.

[0115] In the above embodiments, implementation can be achieved, in whole or in part, through software, hardware, firmware, or any combination thereof. When implemented in software, it can be implemented, in whole or in part, as a computer program product. A computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, all or part of the flow or function according to the embodiments of this application is generated. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions can be stored in a computer-readable storage medium or transmitted from one computer-readable storage medium to another. For example, computer instructions can be transmitted from one website, computer, server, or data center to another website, computer, server, or data center via wired (e.g., coaxial cable, fiber optic, digital subscriber line (DSL)) or wireless (e.g., infrared, wireless, microwave, etc.) means. The computer-readable storage medium can be any available medium that a computer can read or a data storage device such as a server or data center that integrates one or more available media. The available media can be magnetic media (e.g., floppy disks, hard disks, magnetic tapes), optical media (e.g., digital video discs, DVDs) or semiconductor media (e.g., solid-state disks, SSDs) etc.

[0116] The above are merely specific embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A control method for an inverter power supply system, characterized in that, The inverter power supply system includes at least two inverters connected in parallel. The DC terminal of each inverter is connected to a corresponding battery, and the AC terminals of each inverter supply power to the load through a parallel connection point. For each inverter, the method includes: The current discharge capacity and rechargeable capacity of the battery connected to the inverter, the average discharge capacity and average rechargeable capacity of the inverter power supply system are obtained. The average discharge capacity is the average of the current discharge capacity of the battery connected to each inverter, and the average rechargeable capacity is the average of the current rechargeable capacity of the battery connected to each inverter. Based on the average dischargeable capacity, the average rechargeable capacity, the dischargeable capacity, and the rechargeable capacity, the preset droop curve of the inverter is adjusted to obtain the target droop curve, which reflects the negative correlation between active power and frequency. The inverter is controlled to operate according to the target droop curve.

2. The method according to claim 1, characterized in that, The step of adjusting the preset droop curve of the inverter based on the average dischargeable capacity, the average rechargeable capacity, the dischargeable capacity, and the rechargeable capacity to obtain the target droop curve includes: Based on the average dischargeable capacity and the dischargeable capacity, the discharge droop slope of the preset droop curve is adjusted to the target discharge droop slope, which is the slope of the droop curve on the positive half-axis of the active power axis. Based on the average rechargeable capacity and the rechargeable capacity, the charging droop slope of the preset droop curve is adjusted to the target charging droop slope, which is the slope of the droop curve corresponding to the negative half-axis of the active power axis.

3. The method according to claim 1, characterized in that, The DC terminal of at least one of the inverters is also connected to a corresponding photovoltaic module, and the method further includes: Obtain the photovoltaic input power corresponding to the inverter, where the photovoltaic input power is zero when the inverter is not connected to photovoltaic modules; The step of adjusting the preset droop curve of the inverter based on the average dischargeable capacity, the average rechargeable capacity, the dischargeable capacity, and the rechargeable capacity to obtain the target droop curve further includes: When the photovoltaic input power corresponding to the inverter is not zero, the intercept of the preset droop curve with adjusted slope is adjusted according to the average discharge capacity, the average rechargeable capacity, the discharge capacity, the rechargeable capacity, and the photovoltaic input power corresponding to the inverter.

4. The method according to claim 2, characterized in that, The step of adjusting the discharge droop slope of the preset droop curve to the target discharge droop slope based on the average dischargeable capacity and the dischargeable capacity includes: The target discharge droop slope is determined based on the average dischargeable capacity and the dischargeable capacity. The discharge droop slope of the preset droop curve is adjusted to the target discharge droop slope; The step of adjusting the charging droop slope of the preset droop curve to the target charging droop slope based on the average rechargeable capacity and the rechargeable capacity includes: The target charging droop slope is determined based on the average rechargeable capacity and the rechargeable capacity. The charging droop slope of the preset droop curve is adjusted to the target charging droop slope.

5. The method according to claim 3, characterized in that, The step of adjusting the intercept of a preset droop curve with an adjusted slope based on the average discharge capacity, the average rechargeable capacity, the discharge capacity, the rechargeable capacity, and the photovoltaic input power corresponding to the inverter includes: The intercept adjustment value is determined based on the average dischargeable capacity, the average rechargeable capacity, the dischargeable capacity, the rechargeable capacity, and the photovoltaic input power corresponding to the inverter; The intercept of the preset droop curve with adjusted slope is adjusted according to the intercept adjustment value.

6. The method according to claim 1, characterized in that, The step of obtaining the current discharge capacity and rechargeable capacity of the battery connected to the inverter includes: Obtain the current remaining capacity of the battery connected to the inverter; The dischargeable capacity is determined based on the remaining capacity, the minimum discharge capacity of the battery, and the voltage of the battery. The minimum discharge capacity is the remaining capacity when the battery can no longer discharge. The rechargeable capacity is determined based on the remaining capacity, the maximum charging capacity of the battery, and the voltage of the battery. The maximum charging capacity is the remaining capacity when the battery can no longer be charged.

7. The method according to any one of claims 1-6, characterized in that, Each inverter in the inverter power supply system includes a main inverter. The average dischargeable capacity is determined by the main inverter based on the current dischargeable capacity of the batteries connected to each inverter. The average rechargeable capacity is determined by the main inverter based on the current rechargeable capacity of the batteries connected to each inverter. The method further includes: The discharge capacity and the rechargeable capacity are sent to the main inverter.

8. A control device for an inverter power supply system, characterized in that, The inverter power supply system includes at least two inverters connected in parallel. The DC terminal of each inverter is connected to a corresponding battery, and the AC terminals of each inverter supply power to the load through a parallel connection point. For each inverter, the device includes: The processing module is used to obtain the current discharge capacity and rechargeable capacity of the battery connected to the inverter, the average discharge capacity and average rechargeable capacity of the inverter power supply system, wherein the average discharge capacity is the average of the current discharge capacity of the battery connected to each inverter, and the average rechargeable capacity is the average of the current rechargeable capacity of the battery connected to each inverter; and adjusts the preset droop curve of the inverter according to the average discharge capacity, the average rechargeable capacity, the discharge capacity, and the rechargeable capacity to obtain the target droop curve, wherein the droop curve reflects the negative correlation between active power and frequency; The control module is used to control the operation of the inverter according to the target droop curve.

9. An inverter power supply system, characterized in that, The method includes at least two inverters connected in parallel, with the DC terminal of each inverter connected to a corresponding battery, and the AC terminal of each inverter supplying power to the load through a parallel connection point. Each inverter performs the method as described in any one of claims 1 to 7.

10. A computer-readable storage medium, characterized in that, It stores a computer program, which includes program instructions that, when executed by each inverter of the inverter power supply system, perform the method as described in any one of claims 1 to 7.

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