A multi-inverter parallel system power control method and a master inverter thereof

Abstract

The application provides a multi-inverter parallel system power control method and a master inverter. When it is determined that the master inverter fails, a plurality of target slave inverters which do not fail are determined from each slave inverter according to the device state of each slave inverter, wherein each slave inverter and the master inverter belong to the same multi-inverter parallel system; a to-be-switched slave inverter which meets the host switching rule is determined from each target slave inverter according to the derated power information of each target slave inverter, wherein the derated power information of the target slave inverter comprises a derated operating power of the target slave inverter after a derating operation; the to-be-switched slave inverter is switched to the master inverter, and the switched master inverter is controlled to send a synchronous clock signal reference current signal to each target slave inverter.

Description

Technical Field

[0001] This invention relates to the field of new energy technology, specifically to a power control method for a multi-inverter parallel system and its main inverter. Background Technology

[0002] With the continuous development and utilization of renewable energy, more and more new energy power plants, composed of distributed energy sources such as solar, wind, and battery energy storage systems, have gradually reached a certain scale. In these new energy power plants, multiple inverters are typically connected in parallel for control to ensure safe, stable, and reliable operation.

[0003] Currently, the main parallel control method for multiple inverters is the master-slave control method, which consists of one master inverter and multiple slave inverters forming a multi-inverter parallel system. The master inverter has a common control unit function, which is used to send synchronous clock and reference current signals to each slave inverter. However, once the master inverter fails and shuts down, the slave inverters will lose synchronous clock and reference current signals, thus forcing the slave inverters to shut down and causing the multi-inverter parallel system to completely fail.

[0004] Therefore, there is an urgent need for a power control method for multi-inverter parallel systems that can ensure the normal operation of slave inverters when the main inverter fails and shuts down, thus preventing the multi-inverter parallel system from becoming paralyzed. Summary of the Invention

[0005] In view of this, embodiments of this application provide a power control method for a multi-inverter parallel system and its main inverter, with the aim of ensuring the normal operation of the slave inverters when the main inverter fails and shuts down, thereby preventing the multi-inverter parallel system from becoming paralyzed.

[0006] The first aspect of this application provides a power control method for a multi-inverter parallel system, applied to the main inverter, the method comprising:

[0007] When the main inverter is determined to have failed, multiple target slave inverters that have not failed are identified from each slave inverter based on the device status of each slave inverter; wherein each slave inverter and the main inverter belong to the same multi-inverter parallel system.

[0008] Based on the derating power information of each target slave inverter, a slave inverter that meets the master switchover rules is determined from each target slave inverter; wherein, the derating power information of the target slave inverter includes the derating operating power of the target slave inverter after the derating operation is performed;

[0009] The switchable slave inverter is switched to master inverter, and the switched master inverter is controlled to send synchronous clock signal and reference current signal to each target slave inverter.

[0010] Optionally, based on the derating power information of each target slave inverter, determining the slave inverter to be switched from each target slave inverter that meets the master switching rules includes:

[0011] Control each of the aforementioned targets to perform a derating operation from the inverter;

[0012] Based on the reduced operating power of each target inverter after the derating operation, the target inverters are sorted from largest to smallest to obtain an inverter sequence;

[0013] The system derating expectation is calculated based on the derating power of the first target slave inverter and the derating power of the second target slave inverter; wherein the first target slave inverter and the second target slave inverter are the two target slave inverters at the end of the inverter sequence, and the derating power of the first target slave inverter is greater than the derating power of the second target slave inverter.

[0014] If the system derating expectation meets the preset derating threshold, the first target slave inverter is determined to be the slave inverter to be switched, and the second target slave inverter is turned off;

[0015] If the system's expected reduction does not meet the preset derating threshold, the second target inverter will be determined as the inverter to be switched to.

[0016] Optionally, based on the first target derating power of the inverter and the second target derating power of the inverter, the system derating expectation is calculated, including:

[0017] Calculate the product of the first target inverter's dated operating power and a first coefficient, and the product of the second target inverter's dated operating power and a second coefficient; wherein the first coefficient is less than the second coefficient;

[0018] The system derating power is obtained by calculating the difference between the product of the first target inverter's drated operating power and the first coefficient and the product of the second target inverter's drated operating power and the second coefficient.

[0019] Optionally, the process of determining whether the main inverter has malfunctioned includes:

[0020] Obtain the device status of the main inverter and determine whether the device status of the main inverter is any of the preset fault states among a plurality of preset fault states;

[0021] If the device status of the main inverter is any of the preset fault states among the plurality of preset fault states, it is determined that the main inverter has failed.

[0022] If the device status of the main inverter is not any of the preset fault states among the plurality of preset fault states, it is determined that the main inverter has not malfunctioned.

[0023] Optionally, when a fault is determined in the master inverter, at least one target slave inverter that has not failed is determined from among the slave inverters based on the device status of each slave inverter, including:

[0024] For each slave inverter, when it is determined that the master inverter has failed, it is determined whether the device status of the slave inverter is any of the preset fault states among a plurality of preset fault states;

[0025] If the device status of the slave inverter is any of the preset fault states among the plurality of preset fault states, it is determined that the slave inverter has failed.

[0026] If the device status of the slave inverter is not any of the preset fault states among the plurality of preset fault states, it is determined that the slave inverter has not failed, and the inverter that has not failed is identified as the target slave inverter.

[0027] Optionally, the method further includes:

[0028] When a fault is detected in the slave inverter, the slave inverter is shut down.

[0029] Optionally, the method further includes:

[0030] When it is determined that the main inverter has not failed, the expected value of system fault, the number of system faults, and the expected value of system power are determined based on the equipment status and power information of each inverter; wherein, each inverter includes each slave inverter and the main inverter;

[0031] Based on the expected system fault value, the number of system faults, and the expected system power value, calculate the downtime expectation of the multi-inverter parallel system;

[0032] Accordingly, when a fault is determined in the master inverter, at least one target slave inverter that has not experienced a fault is determined from among the slave inverters based on the device status of each slave inverter, including:

[0033] When it is determined that the main inverter has failed, or when it is determined that the main inverter has not failed and the shutdown expectation is within the preset expectation range, at least one target slave inverter that has not failed is determined from each of the slave inverters based on the equipment status of each slave inverter.

[0034] Optionally, based on the expected system fault value, the number of system faults, and the expected system power, the downtime expectation of the multi-inverter parallel system is calculated, including:

[0035] The downtime expectation of the multi-inverter parallel system is determined based on the expected system fault value and its corresponding weight, the number of system faults and their corresponding weight, and the expected system power value and its corresponding weight.

[0036] Optionally, the method further includes:

[0037] If the shutdown expectation is greater than any preset expectation value within the preset expectation range, the multi-inverter parallel system is controlled to shut down.

[0038] Optionally, before the main inverter after control switching sends the synchronization clock signal reference current signal to each of the target slave inverters, the method further includes:

[0039] Based on the equipment status and derating power information of each target inverter, the expected value of target system faults, the number of target system faults, and the expected value of target system power are determined; wherein each target inverter includes the slave inverter to be switched to become the master inverter and each target slave inverter;

[0040] Based on the expected value of the target system fault, the number of target system faults, and the expected value of the target system power, calculate the expected downtime of the multi-inverter parallel system;

[0041] If the target shutdown expectation is greater than any preset expectation value within the preset expectation range, control the shutdown of the multi-inverter parallel system after switching the main inverter;

[0042] Accordingly, before the main inverter sends the synchronization clock signal reference current signal to each of the target slave inverters after the control switch, the process includes:

[0043] If the target shutdown expectation is within the preset expectation range, the main inverter after control switching sends a synchronous clock signal and a reference current signal to each of the target slave inverters.

[0044] Optionally, the method further includes:

[0045] If the number of faults in the target system exceeds a preset fault threshold, the multi-inverter parallel system after the main inverter is switched off will be shut down.

[0046] A second aspect of this application provides a main inverter, the main inverter including a master-slave controller and a fault linkage rule controller;

[0047] The fault linkage rule controller is used to, when it is determined that the main inverter has failed, determine at least one target slave inverter that has not failed from among the slave inverters based on the equipment status of each slave inverter; wherein, each slave inverter and the main inverter belong to the same multi-inverter parallel system; and determine the slave inverter to be switched from among the target slave inverters that meets the master switching rules based on the derating power information of each target slave inverter; wherein, the derating power information of the target slave inverter includes the derating operating power of the target slave inverter after the derating operation;

[0048] The master-slave controller is used to switch the master inverter to the slave inverter to be switched, and to control the switched master inverter to send a synchronization clock signal and a reference current signal to each of the target slave inverters.

[0049] This application provides a power control method and system for a multi-inverter parallel system, applied to a master inverter. When a fault is detected in the master inverter, at least one target slave inverter that has not experienced a fault is determined from among the slave inverters based on the device status of each slave inverter. Each slave inverter belongs to the same multi-inverter parallel system as the master inverter. Based on the derating power information of each target slave inverter, a slave inverter that meets the master inverter switching rules is determined from among the target slave inverters. The derating power information of the target slave inverter includes the operating power of the target slave inverter after derating. The master inverter is switched to the slave inverter to be switched, and the switched master inverter is controlled to send a synchronization clock signal and reference current signal to each target slave inverter. The technical solution provided in this application allows the main inverter to be switched to a non-faulty slave inverter that meets the master switchover rules when the main inverter fails. This enables the switched main inverter to send synchronous clock signals and reference current signals to each of the target slave inverters, thereby ensuring the normal operation of the slave inverters when the main inverter fails and shuts down, and preventing the paralysis of the multi-inverter parallel system. Attached Figure Description

[0050] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0051] Figure 1 A structural diagram of a multi-inverter parallel system provided in this application embodiment;

[0052] Figure 2 A flowchart illustrating a power control method for a multi-inverter parallel system provided in an embodiment of this application;

[0053] Figure 3 A schematic diagram of the structure of a main inverter provided in an embodiment of this application;

[0054] Figure 4 This is a structural diagram of another multi-inverter parallel system provided in an embodiment of this application. Detailed Implementation

[0055] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0056] In this application, the terms "comprising," "including," or any other variations thereof are intended to cover a 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 limitation, 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.

[0057] As can be seen from the above background technology, once the main inverter fails and shuts down, the slave inverter will lose the synchronization clock and reference current signal, thereby forcing the slave inverter to shut down and causing the multi-inverter parallel system to be completely paralyzed.

[0058] In existing technologies, redundant logic control can be used to address the aforementioned problems. Specifically, a redundant, hot-standby voltage outer loop controller is added to the control logic of each slave inverter. When the master inverter fails, the voltage outer loop controller switches the operating mode of any slave inverter to the master inverter's operating mode, allowing that slave inverter to take over the operation of the faulty master inverter, thus preventing a complete system failure. However, this method cannot guarantee the operational status of the slave inverter that has switched to master mode. If the operating status of the slave inverter that has switched to master mode is abnormal, it can still lead to the system failure. Furthermore, due to the circulating current and current sharing control methods used in multi-inverter parallel systems, the operating status of slave inverters strictly follows that of the master inverter. If the derating of the selected slave inverter as master inverter is too high, it will also affect the derating of other slave inverters, resulting in a decrease in the charging and discharging power of the entire multi-inverter parallel system, thereby affecting the normal operation of the multi-inverter parallel system.

[0059] Therefore, this application provides a power control method and system for a multi-inverter parallel system. In the event of a main inverter failure, at least one target slave inverter that has not failed can be identified from among the slave inverters, ensuring the normal operation of the slave inverter switched to the main inverter. Furthermore, this application can determine the slave inverter to be switched from among the target slave inverters that meets the main inverter switching rules based on the reduced operating power after derating operations on each target slave inverter. This avoids abnormal derating of the slave inverter switched to the main inverter, ensuring the normal operation of other slave inverters in the event of a main inverter failure and shutdown, thus preventing the multi-inverter parallel system from paralyzing.

[0060] See Figure 1 The diagram shows a structural diagram of a multi-inverter parallel system provided in an embodiment of this application. The multi-inverter parallel system includes a master inverter and multiple slave inverters.

[0061] See Figure 2 This document illustrates a flowchart of a power control method for a multi-inverter parallel system provided in an embodiment of this application, applicable to... Figure 1 The illustrated main inverter in a multi-inverter parallel system, also known as the master inverter, is described in the following steps:

[0062] S201: Determine whether the main inverter has malfunctioned; if the main inverter has malfunctioned, proceed to step S202; if the main inverter has not malfunctioned, proceed to step S205.

[0063] In the embodiments of this application, multiple preset fault states can be preset. For example, multiple preset fault states may include islanding fault state, overvoltage fault state, undervoltage fault state, etc. The corresponding preset fault states can be set according to the actual application, and this application does not limit them here.

[0064] Optionally, the process of determining whether the main inverter has failed may be as follows: obtain the device status of the main inverter and determine whether the device status of the main inverter is any of the multiple preset fault states; if the device status of the main inverter is any of the multiple preset fault states, determine that the main inverter has failed; if the device status of the main inverter is not any of the multiple preset fault states, determine that the main inverter has not failed.

[0065] If it is determined that the main inverter has failed, step S202 can be executed; if it is determined that the main inverter has not failed, step S205 can be executed.

[0066] S202: Determine multiple target slave inverters that have not experienced a fault from each slave inverter based on the device status of each slave inverter.

[0067] In the specific execution of step S202, if it is determined that the main inverter has failed, the device status of each slave inverter can be further obtained so as to determine multiple target slave inverters that have not failed from each slave inverter based on the device status of each slave inverter.

[0068] Optionally, for each slave inverter, the process of determining whether a slave inverter has failed can be as follows: For each slave inverter, when it is determined that the master inverter has failed, it can be further determined whether the device status of the slave inverter is any of the multiple preset fault states; if the device status of the slave inverter is any of the multiple preset fault states, it is determined that the slave inverter has failed; if the device status of the slave inverter is not any of the multiple preset fault states, it is determined that the slave inverter has not failed, and the inverter that has not failed is identified as the target slave inverter.

[0069] Furthermore, in the embodiments of this application, for each slave inverter, when it is determined that the slave inverter has failed, the slave inverter can be shut down to avoid mistakenly switching the failed slave inverter to the master inverter when the master inverter fails, which would cause the multi-inverter parallel system to malfunction.

[0070] In this embodiment, in order to further ensure the normal operation of the multi-inverter parallel system, before determining at least one target slave inverter that has not experienced a fault from each slave inverter based on the equipment status of each slave inverter, the number of faulty slave inverters can be determined based on the number of slave inverters that have experienced a fault, and it can be determined whether the number of faulty slave inverters is greater than a preset threshold. If the number of faulty slave inverters is greater than the preset threshold, it can be considered that the risk of the multi-inverter parallel system continuing to operate is relatively high, so the multi-inverter parallel system can be shut down for maintenance.

[0071] It should be noted that the preset threshold is set based on the number of inverters in the multi-inverter parallel system; the number of inverters includes the number of master inverters and slave inverters.

[0072] For example, if a multi-inverter parallel system includes 5 inverters, the preset threshold can be set to 2. If the number of faults in the multi-inverter parallel system is 3, it means that 3 inverters have failed. Therefore, it can be considered that the risk of the multi-inverter parallel system continuing to operate is relatively high. Thus, the multi-inverter parallel system can be shut down for maintenance, so that it can be restarted after the maintenance is completed.

[0073] S203: Based on the derating power information of each target slave inverter, determine the slave inverter to be switched from each target slave inverter that meets the master switching rules; wherein, the derating power information of the target slave inverter includes the operating power of the target slave inverter after the derating operation.

[0074] In this embodiment, since the multi-inverter parallel system adopts current sharing control to avoid circulating current control, that is, the operating power of the master inverter and the slave inverter are equal, if an inverter in the multi-inverter parallel system is derated, the multi-inverter parallel system will inevitably use the derated amount of the inverter with the largest derated amount as the standard to derate the other inverters together. Otherwise, the multi-inverter parallel system will generate circulating current. Moreover, if the system derated amount of the multi-inverter parallel system exceeds a certain amount, it will affect the overall operation of the multi-inverter parallel system.

[0075] For example, if one of the five target inverters has a derating of 40%, while the others have no derating, and the entire multi-inverter parallel system operates at 250kW, with each target inverter operating at 50kW, and one target inverter derating to 60%, then all target inverters will undergo a common derating of 40%, reducing the overall operating power of the multi-inverter parallel system from 205kW to 150kW. If this target inverter is considered to be near faulty and shut down, the system will operate at 200kW. Therefore, shutting down the faulty inverter provides 50kW more power than common derating, making it more advantageous. Furthermore, switching the faulty inverter to the master inverter at this point would directly cause the multi-inverter parallel system to fail.

[0076] As can be seen from the above, corresponding master switchover rules can be pre-set so that after identifying at least one target slave inverter that has not experienced a fault from among the slave inverters, the derating operation of each target slave inverter in the multi-inverter parallel system can be further performed. The derating operation power of each target slave inverter after the derating operation is evaluated according to the master switchover rules, so as to determine whether there is a slave inverter to be switched that meets the master switchover rules, and whether there is a faulty inverter that needs to be shut down, so as to ensure the normal operation of the multi-inverter parallel system after the master inverter switchover.

[0077] Specifically, the derated operating power after each target is derated from the inverter can be used as the independent variable, and the shutdown or overall derated operation of the multi-inverter parallel system can be used as the output result guide to construct the corresponding system derated expectation calculation function, as shown in formula (1).

[0078] E(s1,s2,...,s n )=f(p1,p2,...,p n )

[0079] Where, p i For the i-th target, s is the dated operating power of the inverter. i The i-th target is the operating state of the inverter.

[0080] It should be noted that when s i When the value is 0, it means that the i-th inverter is in the off state. When the value is 1, it means that the i-th inverter is in the running state.

[0081] In this embodiment of the application, the slave inverters that meet the master switching rules can be determined from each target slave inverter based on the constructed system derating expectation function and the derating power information of each target slave inverter.

[0082] Optionally, based on the constructed system derating expectation function and the derating power information of each target slave inverter, the process of determining the slave inverter to be switched from each target slave inverter that meets the master switching rules can be as follows: Based on the derating operating power of each target slave inverter after the derating operation, sort the target slave inverters from largest to smallest to obtain an inverter sequence; calculate the system derating expectation based on the operating power of the first target slave inverter and the derating operating power of the second target slave inverter; wherein, the first target slave inverter and the second target slave inverter are the two target slave inverters at the end of the inverter sequence, and the derating operating power of the first target slave inverter is greater than that of the second target slave inverter; if the system derating expectation meets the preset derating threshold, determine the first target slave inverter as the slave inverter to be switched, and shut down the second target slave inverter; if the system derating expectation does not meet the preset derating threshold, determine the second target slave inverter as the slave inverter to be switched.

[0083] It should be noted that if the system derating expectation calculated based on the derating operating power of the first target slave inverter and the derating operating power of the second target slave inverter meets the preset derating threshold, it means that the derating amount of the second target slave inverter is the largest. Furthermore, if the derating is carried out jointly based on the derating amount of the second target slave inverter, it may affect the normal operation of the multi-inverter parallel system. Therefore, the second target slave inverter can be shut down to avoid affecting the normal operation of the multi-inverter parallel system.

[0084] As a preferred embodiment of this application, the calculation process of the system derating expectation can be as follows: calculate the product of the derating operating power of the first target slave inverter and the first coefficient, and the product of the derating operating power of the second target slave inverter and the second coefficient; calculate the difference between the product of the derating operating power of the first target slave inverter and the first coefficient and the product of the derating operating power of the second target slave inverter and the second coefficient to obtain the system derating power.

[0085] It should be noted that the first coefficient is less than the second coefficient. For example, the first coefficient can be 4 and the second coefficient can be 7.5. The preset devaluation threshold can be 0. It can be set according to the actual application. This application embodiment does not limit it.

[0086] In this embodiment, the system derating expectation meeting the preset derating threshold can be that the system derating threshold is greater than the preset derating threshold; the system derating expectation not meeting the preset derating threshold can be that the system derating threshold is not greater than the preset derating threshold. This embodiment of the application does not limit this.

[0087] For example, suppose a parallel system has 5 target slave inverters, and their derating operating powers are p1, p2, ..., p5. Based on the constructed system derating expectation function, the target slave inverters are sorted from largest to smallest according to their derating operating powers after the derating operation, resulting in an inverter sequence of p1>p2>...>p5. From this inverter sequence, it can be determined that target slave inverter number 4 is the first target slave inverter and target slave inverter number 5 is the second target slave inverter.

[0088] Assuming the first coefficient is 4, the second coefficient is 7.5, and the preset derating threshold can be 0; the product of the derating operating power of the first target slave inverter and the first coefficient is 4*p4, and the product of the derating operating power of the second target slave inverter and the second coefficient is 7.5*p5, then the system derating power is 4*p4-7.5*p5; if 4*p4>7.5*p5, then it can be determined that the system derating expectation meets the preset derating threshold, and the first target slave inverter can be identified as the slave inverter to be switched, and the second target slave inverter can be turned off, that is, the fourth target slave inverter is identified as the slave inverter to be switched, and the fifth target slave inverter is turned off.

[0089] S204: Switch the main inverter to the slave inverter to be switched, and control the switched main inverter to send synchronous clock signal and reference current signal to each target slave inverter.

[0090] In the specific execution of step S204, after determining the slave inverter to be switched from each target slave inverter, the master inverter is switched to the slave inverter to be switched, and the switched master inverter is controlled to send synchronous clock signal and reference current signal to each target slave inverter. This ensures that the slave inverter can operate normally in the event of a fault shutdown of the master inverter, thus avoiding the problem of paralysis of the multi-inverter parallel system.

[0091] It should be noted that switching from a slave inverter to a master inverter means switching the operating mode of the slave inverter to the master inverter operating mode.

[0092] It should also be noted that the host operating mode may include the power control method for multi-inverter parallel systems provided in the embodiments of this application.

[0093] S205: Based on the equipment status and power information of each inverter, determine the expected value of system faults, the number of system faults, and the expected system power.

[0094] In the specific execution of step S205, if it is determined that the main inverter has not failed, in order to further ensure the normal operation of the multi-inverter parallel system, the expected value of system fault and the number of system faults can be determined based on the equipment status of each inverter, and the expected value of system power can be determined based on the power information of each inverter, so as to determine whether the main inverter needs to be switched or whether the multi-inverter parallel system needs to be shut down based on the shutdown expectation of the multi-inverter parallel system.

[0095] In this embodiment, the device status of the inverters in the multi-inverter parallel system, the number of system faults and the operating power can be used as independent variables, and the downtime expectation of the multi-inverter parallel system can be used as the output result to construct the corresponding downtime expectation calculation function, as shown in formula (2).

[0096] E(s1,s2,...,s n )=g(w1f1(x1,x2,...,x n ),w2f2(m),w3f3(p1,p2,...,p n (2)

[0097] Where E is the expected downtime, s i Let f1 be the expected system fault function, w1 be the weight corresponding to the expected system fault function, and x be the operating state of the i-th inverter. i Let f2 be the device state of the i-th inverter, w2 be the expected function of the number of system faults, m be the number of inverters with the preset fault state, f3 be the expected function of system power, w3 be the weight of the expected function of system power, and p be the device state of the i-th inverter. i Let be the operating power of the i-th inverter, and n be the number of inverters in the multi-inverter parallel system.

[0098] It should be noted that when s i When the value is 0, it means that the i-th inverter is in the off state. When the value is 1, it means that the i-th inverter is in the running state.

[0099] In some embodiments, the expected value of system faults can be determined based on the constructed downtime expectation calculation function and the expected functions of equipment status and system faults of each inverter; the expected value of the number of system faults can be determined based on the constructed downtime expectation calculation function, the expected functions of equipment status and the number of system faults of each inverter; and the expected value of system power can be determined based on the constructed downtime expectation calculation function, the operating power in the power information of each inverter, and the expected function of system power.

[0100] S207: Calculate the downtime expectation of a multi-inverter parallel system based on the expected system fault value, the number of system faults, and the expected system power value.

[0101] In this embodiment of the application, after calculating the expected value of system faults, the number of system faults, and the expected value of system power, the weights corresponding to the expected value of system faults, the number of system faults, and the expected value of system power can be further determined. Based on the expected value of system faults and their weights, the number of system faults and their weights, and the expected value of system power and their weights, the shutdown expectation of the multi-inverter parallel system can be determined.

[0102] It should be noted that the weight corresponding to the expected value of system faults is the same as the weight corresponding to the expected function of system faults, the weight corresponding to the number of system faults is the same as the weight corresponding to the number of system faults function, and the weight corresponding to the expected value of system power is the same as the weight corresponding to the expected function of system power.

[0103] For example, in a multi-inverter parallel system with 5 inverters, inverter 1 is the main inverter. At a certain moment, inverters 2 and 3 report islanding faults, inverter 4 reports an overvoltage fault, and inverters 1 and 5 are operating normally at full load. Based on the equipment status and power information of each inverter, the expected system fault function can be f1(0, islanding, islanding, overvoltage, 0), and the expected system fault value can be determined to be 3; the expected number of system faults can be f2(2), and the expected number of system faults can be determined to be 2; the expected system power function can be f3(p1, p5), and the expected system power value can be determined to be 2.

[0104] Assuming the weight of the expected system fault function is 0.5, the weight of the expected number of system faults is 0.3, the weight of the expected system power function is 0.1, and the weight of other expected functions is 0.1, then by weighting the expected system fault value with its weight, the expected number of system faults with its weight, the expected system power value with its weight, and the weight of other expected functions, the expected shutdown value of the multi-inverter parallel system can be calculated as 2.3. The specific calculation method is shown in formula (3).

[0105] w1*f1+w2*f2+w3*f3=(0.5*3+0.3*2+0.1*2+0.1*0) / (0.5+0.3+0.1+0.1)=2.3(3)

[0106] It should be noted that 0 in the system fault expectation function indicates that the device state is not the preset fault state.

[0107] S208: Determine whether the shutdown expectation is within the preset expectation range; if the shutdown expectation is within the preset expectation range, return to step S202; if the shutdown expectation is greater than any preset expectation value within the preset expectation range, execute step S209.

[0108] In this embodiment, a preset expected range and corresponding fault linkage rules can be set in advance. The fault linkage rules can indicate that: if the shutdown expectation is less than any preset expected value within the preset expected range, the current system is operating stably, and neither main inverter switching nor shutdown of the multi-inverter parallel system is required. If the shutdown expectation is within the preset expected range, the current system requires main inverter switching, and step S202 can be executed to perform the corresponding main inverter switching. If the shutdown expectation is greater than any preset expected value within the preset expected range, it can be considered that there is a certain risk in continuing system operation, and shutdown of the multi-inverter parallel system can be controlled.

[0109] During the specific execution of step S208, after calculating the shutdown expectation of the multi-inverter parallel system, it is possible to further determine whether it is necessary to switch the main inverter or to control the shutdown of the multi-inverter parallel system based on the shutdown expectation, the preset expectation range and the fault linkage rules.

[0110] Specifically, based on the shutdown expectation, the preset expectation range, and the fault linkage rules, the process of determining whether a main inverter switch or a multi-inverter parallel system shutdown is required can be as follows: Determine if the shutdown expectation is within the preset expectation range. If it is, the system requires a main inverter switch, and step S202 can be executed to perform the switch. If the shutdown expectation is greater than any preset expectation value within the range, the system is considered to be at risk of continued operation, and the multi-inverter parallel system shutdown can be controlled, i.e., step S209 can be executed. If the shutdown expectation is less than any preset expectation value within the range, the system is considered to be operating stably, and the current operating mode can be maintained.

[0111] S209: Controls the shutdown of a multi-inverter parallel system.

[0112] In the specific execution of step S209, if it is determined that the shutdown expectation is greater than any preset expectation value within the preset expectation range, it can be considered that there is a certain risk in the continued operation of the system. In this way, the shutdown of the multi-inverter parallel system can be controlled to avoid the multi-inverter parallel system from malfunctioning during operation.

[0113] This application provides a power control method for a multi-inverter parallel system. In the event of a main inverter failure, the main inverter can be switched to a non-faulty slave inverter that meets the master inverter switching rules. The switched main inverter then sends synchronous clock and reference current signals to each target slave inverter, ensuring the normal operation of the slave inverters even when the main inverter fails and shuts down, thus preventing the multi-inverter parallel system from collapsing. If the main inverter is not faulty, the shutdown expectation of the multi-inverter parallel system can be further calculated. When the shutdown expectation is within a preset expectation range, the corresponding main inverter switching process is executed, preventing the continued operation of the current main inverter from causing a system failure. Furthermore, if the shutdown expectation exceeds any preset expectation value within the preset expectation range, it can be considered that continued system operation poses a certain risk, allowing for system shutdown control to prevent system failures during operation.

[0114] Furthermore, to ensure the normal operation of the multi-inverter parallel system, before the master inverter sends the synchronization clock signal and reference current signal to each target slave inverter after the control switch, the expected value of the target system fault, the number of target system faults, and the expected value of the target system power can be determined based on the equipment status and derating power information of each target inverter. Based on these values, the expected downtime of the multi-inverter parallel system after the master inverter switch is calculated. This allows for determination of whether a new master inverter switch is needed, or whether the multi-inverter parallel system needs to be shut down after the master inverter switch, based on the expected downtime, preset expectation range, and fault linkage rules. Each target inverter includes the slave inverter to be switched to the master inverter and the target slave inverters.

[0115] It should be noted that the expected value of the target system fault can be determined based on the shutdown expectation calculation function constructed by formula (2), the expected value of the target system fault can be determined based on the equipment status and system fault expectation function of each target inverter, the expected value of the target system fault can be determined based on the equipment status and system fault quantity expectation function of each target inverter, and the expected value of the target system power can be determined based on the operating power and system power expectation function in the derating power information of each target inverter.

[0116] Determine the weights corresponding to the expected value of the target system faults, the weights corresponding to the number of target system faults, and the weights corresponding to the expected value of the target system power. Based on the expected value of the target system faults and their weights, the number of target system faults and their weights, and the expected value of the target system power and their weights, determine the downtime expectation of the multi-inverter parallel system.

[0117] The system determines whether the target shutdown expectation is within a preset shutdown range. If the target shutdown expectation is greater than any preset expectation value within the preset expectation range, it can be considered that there is a certain risk if the multi-inverter parallel system after switching the main inverter continues to operate. Therefore, the multi-inverter parallel system after switching the main inverter can be shut down. If the target shutdown expectation is within the preset expectation range, it indicates that the currently switched main inverter may not be suitable, and the main inverter switching process can be returned to, i.e., return to step S202. If the target shutdown expectation is less than any preset expectation value within the preset expectation range, it indicates that the multi-inverter parallel system after switching the main inverter can operate stably. The main inverter switching can be omitted, and the multi-inverter parallel system shutdown can be left undone.

[0118] Corresponding to the power control method for a multi-inverter parallel system provided in the above embodiments of the present invention, the present invention also provides a structural block diagram of a main inverter, as shown below. Figure 3 As shown, the main inverter includes a master-slave controller and a fault linkage rule controller;

[0119] The fault linkage rule controller is used to determine at least one target slave inverter that has not failed from among the slave inverters when a fault is determined to have occurred in the master inverter, based on the equipment status of each slave inverter; wherein each slave inverter and the master inverter belong to the same multi-inverter parallel system; and to determine the slave inverter to be switched from among the target slave inverters that meets the master switching rules based on the derating power information of each target slave inverter; wherein the derating power information of the target slave inverter includes the derating operating power of the target slave inverter after the derating operation.

[0120] The master-slave controller is used to switch the master inverter to the slave inverter to be switched, and to control the switched master inverter to send synchronous clock signals and reference current signals to each target slave inverter.

[0121] In this embodiment, the fault linkage control rule controller is connected to each slave inverter via a CAN bus, and the master-slave controller is connected to each slave inverter and the fault linkage control rule controller, respectively. Figure 4 As shown.

[0122] This application provides a power control system for a multi-inverter parallel system. When a fault is detected in the master inverter, at least one target slave inverter that has not failed is determined from among the slave inverters based on the equipment status of each slave inverter. Each slave inverter and the master inverter belong to the same multi-inverter parallel system. Based on the derating power information of each target slave inverter, a slave inverter that meets the master inverter switching rules is determined from among the target slave inverters. The derating power information of the target slave inverter includes the derating operating power after the target slave inverter has undergone a derating operation. The master inverter is switched to the slave inverter to be switched, and the switched master inverter is controlled to send a synchronous clock signal and a reference current signal to each target slave inverter. The technical solution provided in this application allows the main inverter to be switched to a non-faulty slave inverter that meets the master switchover rules when the main inverter fails. This enables the switched main inverter to send synchronous clock signals and reference current signals to each target slave inverter, thereby ensuring the normal operation of the slave inverters when the main inverter fails and shuts down, and avoiding the problem of paralysis in a multi-inverter parallel system.

[0123] Optionally, based on the derating power information of each target slave inverter, a fault linkage rule controller is determined from each target slave inverter to identify the slave inverter to be switched that meets the master switching rules. Specifically, this controller is used for:

[0124] Control each target to perform derating operation from the inverter;

[0125] Based on the derated operating power of each target inverter after the derated operation, the target inverters are sorted from largest to smallest to obtain the inverter sequence;

[0126] The system derating expectation is calculated based on the derating power of the first target slave inverter and the derating power of the second target slave inverter; wherein, the first target slave inverter and the second target slave inverter are the two target slave inverters at the end of the inverter sequence, and the derating power of the first target slave inverter is greater than the derating power of the second target slave inverter.

[0127] If the system derating expectation meets the preset derating threshold, the first target inverter will be determined as the switchable inverter, and the second target inverter will be turned off.

[0128] If the system's expected reduction does not meet the preset derating threshold, the second target will be determined from the inverter to be switched to.

[0129] Optionally, based on the first target derating power of the inverter and the second target derating power of the inverter, a fault linkage rule controller is calculated to determine the system derating expectation, specifically for:

[0130] Calculate the product of the first target derated operating power of the inverter and a first coefficient, and the product of the second target derated operating power of the inverter and a second coefficient; wherein the first coefficient is less than the second coefficient;

[0131] The system derating power is obtained by calculating the product of the first target inverter's drated operating power and the first coefficient, and the product of the second target inverter's drated operating power and the second coefficient.

[0132] Optionally, a fault linkage rule controller for determining whether the main inverter has malfunctioned is specifically used for:

[0133] Obtain the device status of the main inverter and determine whether the device status of the main inverter is any of the multiple preset fault states.

[0134] If the main inverter is in any of the preset fault states among multiple preset fault states, the main inverter is determined to have failed.

[0135] If the main inverter's device status is not any of the multiple preset fault states, it is determined that the main inverter has not experienced a fault.

[0136] Optionally, when a fault is determined in the main inverter, a fault linkage rule controller is used to determine at least one target slave inverter that has not experienced a fault, based on the device status of each slave inverter. Specifically, this controller is used for:

[0137] For each slave inverter, when a fault is detected in the master inverter, it is determined whether the device status of the slave inverter is any of the multiple preset fault states.

[0138] If the inverter's device status is any of the multiple preset fault states, it is determined that the inverter has failed.

[0139] If the device status of the slave inverter is not any of the preset fault states among the multiple preset fault states, it is determined that the slave inverter has not failed, and the slave inverter that has not failed is identified as the target slave inverter.

[0140] Optionally, the fault linkage rule controller is also used to: shut down the slave inverter when a fault is determined to have occurred in the slave inverter.

[0141] Optionally, the fault linkage rule controller is also used for:

[0142] When it is determined that the main inverter has not failed, the expected value of system faults, the number of system faults, and the expected value of system power are determined based on the equipment status and power information of each inverter; where each inverter includes each slave inverter and the main inverter.

[0143] Calculate the downtime expectation of a multi-inverter parallel system based on the expected system fault value, the number of system faults, and the expected system power.

[0144] Accordingly, when a fault is determined in the master inverter, at least one target slave inverter that has not experienced a fault is identified from among the slave inverters based on the device status of each slave inverter, including:

[0145] When it is determined that the main inverter has failed, or when it is determined that the main inverter has not failed and the shutdown expectation is within the preset expectation range, at least one target slave inverter that has not failed is determined from each slave inverter according to the equipment status of each slave inverter.

[0146] Optionally, a fault linkage rule controller is used to calculate the downtime expectation of a multi-inverter parallel system based on the expected system fault value, the number of system faults, and the expected system power value. Specifically, this controller is used for:

[0147] Determine the weights corresponding to the expected system fault value, the number of system faults, and the expected system power;

[0148] The downtime expectation of a multi-inverter parallel system is determined based on the expected value of system faults and their weights, the number of system faults and their weights, and the expected value of system power and their weights.

[0149] Optionally, the fault linkage rule controller is also used for:

[0150] If the shutdown expectation is greater than any preset expectation value within the preset expectation range, control the shutdown of the multi-inverter parallel system.

[0151] Optionally, before the master inverter sends the synchronization clock signal and reference current signal to each target slave inverter after the master-slave controller control switch, the fault linkage rule controller is also used for:

[0152] Based on the equipment status and derating power information of each target inverter, determine the expected value of target system faults, the number of target system faults, and the expected power of the target system.

[0153] Calculate the target downtime expectation of the multi-inverter parallel system based on the target system fault expectation value, the target system fault quantity value, and the target system power expectation value;

[0154] If the target shutdown expectation is greater than any preset expectation value within the preset expectation range, the multi-inverter parallel system after the main inverter is switched will shut down.

[0155] Correspondingly, the master-slave controller that controls the switched master inverter to send synchronous clock signals and reference current signals to each target slave inverter is also used to: if the target shutdown expectation is within the preset expectation range, switch the master inverter to the slave inverter to be switched.

[0156] Optionally, the fault linkage rule controller is also used for:

[0157] If the number of faults in the target system exceeds the preset fault threshold, the multi-inverter parallel system after the main inverter is switched will be shut down.

[0158] The various embodiments in this specification are described in a progressive manner. Similar or identical parts between embodiments can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. In particular, for system or system embodiments, since they are basically similar to method embodiments, the description is relatively simple, and relevant parts can be referred to the descriptions in the method embodiments. The systems and system embodiments described above are merely illustrative. 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 modules can be selected to achieve the purpose of this embodiment according to actual needs. Those skilled in the art can understand and implement this without creative effort.

[0159] Those skilled in the art will further recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of both. To clearly illustrate the interchangeability of hardware and software, the components and steps of the various examples have been generally described in terms of functionality in the foregoing description. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementations should not be considered beyond the scope of this invention.

[0160] 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 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. A power control method for a multi-inverter parallel system, characterized in that, Applied to a main inverter, the method includes: When the main inverter is determined to have failed, multiple target slave inverters that have not failed are identified from each slave inverter based on the device status of each slave inverter; wherein each slave inverter and the main inverter belong to the same multi-inverter parallel system. Based on the derating power information of each target slave inverter, a slave inverter that meets the master switchover rules is determined from each target slave inverter; wherein, the derating power information of the target slave inverter includes the derating operating power of the target slave inverter after the derating operation is performed; The switchable slave inverter is switched to master inverter, and the switched master inverter is controlled to send synchronous clock signal and reference current signal to each target slave inverter.

2. The method according to claim 1, characterized in that, Based on the derating power information of each target slave inverter, determine the slave inverters to be switched from each target slave inverter that meet the master switching rules, including: Control each of the aforementioned targets to perform a derating operation from the inverter; Based on the reduced operating power of each target inverter after the derating operation, the target inverters are sorted from largest to smallest to obtain an inverter sequence; The system derating expectation is calculated based on the derating power of the first target slave inverter and the derating power of the second target slave inverter; wherein the first target slave inverter and the second target slave inverter are the two target slave inverters at the end of the inverter sequence, and the derating power of the first target slave inverter is greater than the derating power of the second target slave inverter. If the system derating expectation meets the preset derating threshold, the first target slave inverter is determined to be the slave inverter to be switched, and the second target slave inverter is turned off; If the system's expected reduction does not meet the preset derating threshold, the second target inverter will be determined as the inverter to be switched to.

3. The method according to claim 2, characterized in that, Based on the first target of reduced operating power from the inverter and the second target of reduced operating power from the inverter, the expected system derating is calculated, including: Calculate the product of the first target inverter's dated operating power and a first coefficient, and the product of the second target inverter's dated operating power and a second coefficient; wherein the first coefficient is less than the second coefficient; The system derating power is obtained by calculating the difference between the product of the first target inverter's drated operating power and the first coefficient and the product of the second target inverter's drated operating power and the second coefficient.

4. The method according to claim 1, characterized in that, The process of determining whether the main inverter has malfunctioned includes: Obtain the device status of the main inverter and determine whether the device status of the main inverter is any of the preset fault states among a plurality of preset fault states; If the device status of the main inverter is any of the preset fault states among the plurality of preset fault states, it is determined that the main inverter has failed. If the device status of the main inverter is not any of the preset fault states among the plurality of preset fault states, it is determined that the main inverter has not malfunctioned.

5. The method according to claim 4, characterized in that, When a fault is determined in the master inverter, at least one target slave inverter that has not experienced a fault is determined from among the slave inverters based on the device status of each slave inverter, including: For each slave inverter, when it is determined that the master inverter has failed, it is determined whether the device status of the slave inverter is any of the preset fault states among a plurality of preset fault states; If the device status of the slave inverter is any of the preset fault states among the plurality of preset fault states, it is determined that the slave inverter has failed. If the device status of the slave inverter is not any of the preset fault states among the plurality of preset fault states, it is determined that the slave inverter has not failed, and the inverter that has not failed is identified as the target slave inverter.

6. The method according to claim 5, characterized in that, The method further includes: When a fault is detected in the slave inverter, the slave inverter is shut down.

7. The method according to claim 4, characterized in that, The method further includes: When it is determined that the main inverter has not failed, the expected value of system fault, the number of system faults, and the expected value of system power are determined based on the equipment status and power information of each inverter; wherein, each inverter includes each slave inverter and the main inverter; Based on the expected system fault value, the number of system faults, and the expected system power value, calculate the downtime expectation of the multi-inverter parallel system; Accordingly, when a fault is determined in the master inverter, at least one target slave inverter that has not experienced a fault is determined from among the slave inverters based on the device status of each slave inverter, including: When it is determined that the main inverter has failed, or when it is determined that the main inverter has not failed and the shutdown expectation is within the preset expectation range, at least one target slave inverter that has not failed is determined from each of the slave inverters based on the equipment status of each slave inverter.

8. The method according to claim 7, characterized in that, Based on the expected system fault value, the number of system faults, and the expected system power, calculate the downtime expectation of the multi-inverter parallel system, including: The downtime expectation of the multi-inverter parallel system is determined based on the expected system fault value and its corresponding weight, the number of system faults and their corresponding weight, and the expected system power value and its corresponding weight.

9. The method according to claim 8, characterized in that, The method further includes: If the shutdown expectation is greater than any preset expectation value within the preset expectation range, the multi-inverter parallel system is controlled to shut down.

10. The method according to claim 1, characterized in that, Before the main inverter sends the synchronization clock signal and reference current signal to each of the target slave inverters after the control switch, the method further includes: Based on the equipment status and derating power information of each target inverter, the expected value of target system faults, the number of target system faults, and the expected value of target system power are determined; wherein, each target inverter includes the slave inverter to be switched to become the master inverter and each target slave inverter; Based on the expected value of the target system fault, the number of target system faults, and the expected value of the target system power, calculate the expected downtime of the multi-inverter parallel system; If the target shutdown expectation is greater than any preset expectation value within the preset expectation range, control the shutdown of the multi-inverter parallel system after switching the main inverter; Accordingly, before the main inverter sends the synchronization clock signal reference current signal to each of the target slave inverters after the control switch, the process includes: If the target shutdown expectation is within the preset expectation range, the main inverter after control switching sends a synchronous clock signal and a reference current signal to each of the target slave inverters.

11. The method according to claim 10, characterized in that, The method further includes: If the number of faults in the target system exceeds a preset fault threshold, the multi-inverter parallel system after the main inverter is switched off will be shut down.

12. A main inverter, characterized in that, The main inverter includes a master-slave controller and a fault linkage rule controller; The fault linkage rule controller is used to, when it is determined that the main inverter has failed, determine at least one target slave inverter that has not failed from among the slave inverters based on the equipment status of each slave inverter; wherein, each slave inverter and the main inverter belong to the same multi-inverter parallel system; and determine the slave inverter to be switched from among the target slave inverters that meets the master switching rules based on the derating power information of each target slave inverter; wherein, the derating power information of the target slave inverter includes the derating operating power of the target slave inverter after the derating operation; The master-slave controller is used to switch the master inverter to the slave inverter to be switched, and to control the switched master inverter to send a synchronization clock signal and a reference current signal to each of the target slave inverters.

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