Inverter control method, inverter and power generation system

Abstract

The embodiment of the invention provides an inverter control method, an inverter and a power generation system, and the method comprises the steps: obtaining the aging data of each bridge arm in three-phase bridge arms in a current working period, and the load condition of each phase sequence in a power grid in a next working period; establishing a matching relationship between each bridge arm and each phase sequence in the next working period according to the aging data of each bridge arm in the three-phase bridge arms corresponding to the current working period and the load condition of each phase sequence in the next period; and based on the matching relationship, controlling the phase commutation relay group to connect each bridge arm to the corresponding phase sequence. Thus, by converting the connection relation between the bridge arms and the phase sequence, the aging degree of each bridge arm in the inverter can be balanced, and the service life of the inverter is prolonged.

Description

Technical Field

[0001] This application relates to the field of power generation technology, and to, but is not limited to, a control method for an inverter, an inverter, and a power generation system. Background Technology

[0002] With traditional energy sources becoming increasingly depleted, solar energy is emerging as the dominant new energy source for the future. Grid-connected power generation systems, based on photovoltaic (PV) power generation equipment, effectively utilize solar energy resources to generate electricity. The inverter is the core component of a PV grid-connected power generation system. It converts the direct current (DC) generated by the PV power generation equipment into alternating current (AC) and feeds it into the power grid.

[0003] However, the power grid contains a large number of single-phase and asymmetrical loads, and the operation of three-phase loads varies randomly. These loads can cause three-phase imbalance in the power grid. Long-term three-phase imbalance can lead to inconsistent aging of the power electronic components in the three-phase bridge arms of the inverter, reducing the overall service life of the inverter. Therefore, how to balance the aging of the three-phase bridge arms of the inverter is an urgent problem to be solved. Summary of the Invention

[0004] To address the problems existing in related technologies, embodiments of this application provide a control method for an inverter, an inverter, and a power generation system. Based on the aging data of each bridge arm in the inverter and the load conditions of each phase sequence in the power grid, the connection relationship between the bridge arms and the phase sequence is converted, the aging degree of each bridge arm in the inverter is balanced, and the service life of the inverter is extended.

[0005] In a first aspect, this application provides a control method for an inverter, applied to the commutation control unit of the inverter; the control method includes: acquiring aging data of each arm in the three-phase bridge arm during the current working period and the load status of each phase sequence in the power grid during the next working period; establishing a matching relationship between each arm and each phase sequence in the next working period based on the aging data of each arm in the three-phase bridge arm corresponding to the current working period and the load status of each phase sequence in the next period; and controlling the commutation relay group to connect each arm to the corresponding phase sequence based on the matching relationship.

[0006] By employing the aforementioned technical means, and by adjusting the output phase sequence of each bridge arm based on its aging data and the load conditions of each phase sequence in the power grid during the next operating period, the inverter's lifespan can be extended. This not only avoids overuse of some bridge arms with high aging levels, but also reduces the impact of thermal coupling on components in bridge arms with high aging levels, lowering their thermal resistance and extending their lifespan. Furthermore, this embodiment adjusts the output phase sequence according to the power grid's demand to adapt to changes in grid load, helping to maintain the quality of the inverter's output voltage and current, reduce harmonic interference, and improve the power quality connected to the grid. Finally, by adjusting the output phase sequence of the bridge arms, the inverter can adjust the matching strategy between the bridge arms and the phase sequence to cope with fluctuations in grid power consumption, improving the overall operating performance and stability of the power generation system.

[0007] In some embodiments, based on the aging data of each arm in the three-phase bridge arm corresponding to the current working time period and the load status of each phase sequence in the next working time period, a matching relationship between each bridge arm and each phase sequence in the next working time period is established, including: determining the aging order of the three-phase bridge arms based on the aging data of each bridge arm in the three-phase bridge arm corresponding to the current working time period; determining the load order of each phase sequence in the next working time period based on the load status of each phase sequence in the next working time period; and establishing a matching relationship between each bridge arm and each phase sequence in the next working time period based on the aging order and the load order.

[0008] By using the above-mentioned technical means, the output phase sequence of each bridge arm can be adjusted according to the aging degree of each bridge arm and the load of the power grid in the next working period. This can avoid overuse of some bridge arms with high aging degree, thereby extending the service life of the inverter.

[0009] In some embodiments, a matching relationship is established between each bridge arm and each phase sequence in the next working period according to the aging degree order and the load order. This includes: in the next working period, establishing a first matching relationship between bridge arms and phase sequences that both aging degree and load meet a first condition, a second matching relationship between bridge arms and phase sequences that both aging degree and load meet a second condition, and a third matching relationship between bridge arms and phase sequences that both aging degree and load meet a third condition; wherein the first condition represents the highest aging degree and the lowest load; the second condition represents the lowest aging degree and the highest load; and the third condition represents that both aging degree and load are between the highest and the lowest.

[0010] By using the above-mentioned technical means, the output phase sequence of each bridge arm of the inverter is adjusted so that the output phase sequence corresponding to the bridge arm with the highest degree of aging in the inverter is the phase sequence with the lowest power consumption, and the output phase sequence corresponding to the bridge arm with the lowest degree of aging is the phase sequence with the highest power consumption, so as to balance the aging degree of each bridge arm of the inverter and extend the service life of the inverter.

[0011] In some embodiments, the commutation relay group includes multiple commutation relays, each commutation relay including multiple relay switches, and each bridge arm is connected to each phase sequence of the power grid through multiple relay switches in a commutation relay; based on the matching relationship, controlling the commutation relay group to connect each bridge arm to the corresponding phase sequence includes: based on the first matching relationship, the second matching relationship and the third matching relationship, closing the relay switches in the commutation relays corresponding to each bridge arm that are connected to the corresponding phase sequence, so as to connect each bridge arm to the corresponding phase sequence.

[0012] By using the above-mentioned technical means, the output phase sequence of the inverter can be adjusted through the relay switches in the commutation relay group. While ensuring that the grid-connected phase sequence remains unchanged, the aging of power electronic components on the three-phase bridge arm can be balanced, thus extending the service life of the inverter.

[0013] In some embodiments, the control method further includes: acquiring historical usage data of components on each bridge arm of the inverter; the historical usage data includes the rated power conversion of each bridge arm and the cumulative power conversion of each bridge arm; determining a first aging value for each bridge arm based on the rated power conversion of each bridge arm and the cumulative power conversion of components on each bridge arm; comparing a first temperature of each bridge arm in a first state with a second temperature in a second state to obtain a second aging value for each bridge arm; wherein the first state is the initial usage state of the inverter, the second state is the current usage state of the inverter, and the inverter output power is the same when the inverter is in the first state or the second state; and performing a weighted calculation on the first aging value and the second aging value based on a preset first weighting parameter to obtain aging data for each bridge arm.

[0014] By using the above-mentioned technical means, the aging degree of each bridge arm can be calculated by measuring the power conversion and temperature changes of each bridge arm. This allows for a more comprehensive and accurate assessment of the aging degree of each bridge arm. Based on the calculated aging degree, commutation can be performed to more accurately protect the bridge arms with higher aging degrees, thus extending the service life of the inverter.

[0015] In some embodiments, obtaining the power load requirement of the power grid for the next working period to determine the load status of each phase sequence in the power grid for the next working period includes: obtaining historical load data of each phase sequence in the power grid; the historical load data includes the cumulative converted power of each phase sequence and the current converted power of each phase sequence in the current working period; based on the cumulative converted power and the current converted power of each phase sequence, predicting the converted power of each phase sequence in the power grid for the next working period to obtain the load status of each phase sequence in the next working period; the load status is used to characterize the power consumption of each phase sequence in the next working period.

[0016] By using the aforementioned technical means, the power consumption of each phase sequence in the next working period can be predicted using historical data of each phase sequence. This allows for the adjustment of the inverter's control strategy, which can not only extend the inverter's service life but also improve the overall efficiency and reliability of the power generation system.

[0017] In some embodiments, based on the cumulative and current conversion quantities of each phase sequence, the conversion quantities of each phase sequence in the power grid during the next working period are predicted to obtain the load status of each phase sequence in the next working period, including: determining the current three-phase imbalance rate of the power grid during the current working period based on the cumulative and current conversion quantities of each phase sequence; and predicting the load status of each phase sequence in the next working period based on a preset second weight parameter, the current three-phase imbalance rate, the cumulative and current conversion quantities of each phase sequence, to obtain the load status of each phase sequence in the next working period.

[0018] By using the aforementioned technical means and historical data from the power grid, the load of the power system in the next working period can be predicted, and the output phase sequence of the inverter can be adjusted more accurately based on the prediction results.

[0019] Secondly, embodiments of this application provide an inverter, which includes: an inverter circuit including multiple parallel bridge arms; a commutation relay group connected to each bridge arm in the inverter circuit and each phase sequence of the power grid; and a commutation coordination control unit connected to the commutation relay group, used to acquire aging data of each bridge arm in the three-phase bridge arm during the current working period and the load status of each phase sequence in the power grid during the next working period; establish a matching relationship between each bridge arm and each phase sequence in the next working period based on the aging data of each bridge arm in the three-phase bridge arm corresponding to the current working period and the load status of each phase sequence in the next period; and control the commutation relay group to connect each bridge arm to the corresponding phase sequence based on the matching relationship.

[0020] By employing the aforementioned technical means, and by adjusting the output phase sequence of each bridge arm based on its aging data and the load conditions of each phase sequence in the power grid during the next operating period, the inverter's lifespan can be extended. This not only avoids overuse of some bridge arms with high aging levels, but also reduces the impact of thermal coupling on components in bridge arms with high aging levels, lowering their thermal resistance and extending their lifespan. Furthermore, this embodiment adjusts the output phase sequence according to the power grid's demand to adapt to changes in grid load, helping to maintain the quality of the inverter's output voltage and current, reduce harmonic interference, and improve the power quality connected to the grid. Finally, by adjusting the output phase sequence of the bridge arms, the inverter can adjust the matching strategy between the bridge arms and the phase sequence to cope with fluctuations in grid power consumption, improving the overall operating performance and stability of the power generation system.

[0021] In some embodiments, the commutation relay group includes multiple commutation relays; each commutation relay includes multiple relay switches, and each arm of the inverter circuit is connected to each phase sequence of the power grid through the multiple relay switches in the commutation relays.

[0022] Thirdly, embodiments of this application provide an inverter, characterized in that the inverter includes: an acquisition module, used to acquire aging data of each arm in the three-phase bridge arm during the current working period and the load status of each phase sequence in the power grid during the next working period; an establishment module, used to establish a matching relationship between each arm and each phase sequence in the next working period based on the aging data of each arm in the three-phase bridge arm corresponding to the current working period and the load status of each phase sequence in the next period; and a control module, used to control the commutation relay group to connect each arm to the corresponding phase sequence based on the matching relationship.

[0023] Fourthly, embodiments of this application provide a power generation system, comprising: a photovoltaic array connected to an inverter for converting solar energy into direct current (DC); an inverter including an inverter circuit, a commutation relay group, and a commutation control unit, wherein the inverter circuit converts DC into alternating current (AC); the commutation control unit acquires aging data of each arm in the three-phase bridge arm during the current working period and the load status of each phase sequence in the power grid during the next working period; establishes a matching relationship between each arm and each phase sequence in the next working period based on the aging data of each arm in the three-phase bridge arm corresponding to the current working period and the load status of each phase sequence in the next period; and controls the commutation relay group to connect each arm to the corresponding phase sequence based on the matching relationship; and a power grid connected to the inverter for receiving AC.

[0024] By employing the aforementioned technical means and adjusting the output phase sequence of the bridge arms, the inverter can adjust the matching strategy between the bridge arms and the phase sequence to cope with fluctuations in grid power consumption, thereby improving the overall operating performance and stability of the power generation system.

[0025] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the hardware structure of a power generation network including an inverter, provided in an embodiment of this application.

[0027] Figure 2 This is an optional flowchart illustrating the inverter control method provided in the embodiments of this application. Figure 1 ;

[0028] Figure 3 This is an optional flowchart illustrating the inverter control method provided in the embodiments of this application. Figure 2 ;

[0029] Figure 4 This is an optional circuit diagram of the commutation relay group provided in an embodiment of this application;

[0030] Figure 5 This is a schematic diagram of the hardware structure of the inverter provided in the embodiments of this application;

[0031] Figure 6 This is a schematic flowchart of the aging balance control method provided in the embodiments of this application;

[0032] Figure 7 This is a schematic diagram of the power generation system provided in the embodiments of this application;

[0033] Figure 8 This is a schematic diagram of the inverter provided in the embodiment of this application. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of this application clearer, the application will be further described in detail below with reference to the accompanying drawings. The described embodiments should not be regarded as limitations on this application. All other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0035] In the following description, references to "some embodiments" refer to a subset of all possible embodiments. However, it is understood that "some embodiments" may be the same or different subsets of all possible embodiments and may be combined with each other without conflict. Unless otherwise defined, all technical and scientific terms used in the embodiments of this application have the same meaning as commonly understood by one of ordinary skill in the art to which the embodiments of this application pertain. The terminology used in the embodiments of this application is for the purpose of describing the embodiments of this application only and is not intended to limit the application.

[0036] Currently, there are a large number of single-phase and unbalanced loads in the power grid, and the operation of three-phase loads varies randomly. These loads can cause three-phase imbalance in the power grid, which has many harmful effects, such as increasing line losses, accelerating transformer aging, affecting power supply quality, and even affecting personal safety due to the increase in neutral line voltage.

[0037] Long-term three-phase imbalance can also lead to inconsistent aging of the power electronic components in the three-phase bridge arms of the inverter. That is, the bridge arm with higher grid load will age significantly more than the other two bridge arms. When the aging of this bridge arm reaches a certain threshold, the inverter will be taken out of service. Meanwhile, the power electronic components of the other two bridge arms have not yet reached the retirement aging threshold. The above reasons will reduce the overall service life of the inverter due to the lack of aging balance, and make the electronic power components that have not reached the aging threshold unusable, resulting in a waste of cost and resources.

[0038] Currently, the relevant technologies can solve the three-phase imbalance through power electronic equipment compensation and other methods. The three-phase imbalance of the power grid where the inverter is located can also be adjusted by adjusting the three-phase output power to the power grid. However, the methods provided by the relevant technologies can still cause the power electronic components of the three-phase bridge arms of the inverter to age inconsistently. When the power electronic components on one bridge arm age and fail first, the entire inverter will no longer be usable.

[0039] In order to alleviate the problems existing in the relevant technologies, the applicant believes that the degree of aging imbalance of the power electronic components of the three-phase bridge arm of the inverter can be calculated based on the historical usage data of the components on each bridge arm. Based on the degree of imbalance and the predicted power consumption of the three phases of the grid, the output phase sequence of the bridge arm can be adjusted to reduce the unevenness of the aging of the power electronic components of each bridge arm, thereby extending the life of the inverter as a whole.

[0040] Based on the above considerations, and after in-depth research, a control method for an inverter is provided. This method acquires the aging data of each arm in the three-phase bridge arm during the current operating period and the load status of each phase sequence in the power grid during the next operating period. Based on the aging data of each arm in the three-phase bridge arm corresponding to the current operating period and the load status of each phase sequence in the next period, a matching relationship between each arm and each phase sequence in the next operating period is established. Based on the matching relationship, the commutation relay group is controlled to connect each arm to the corresponding phase sequence.

[0041] Thus, this embodiment adjusts the output phase sequence of each bridge arm by using aging data of each bridge arm and the load conditions of each phase sequence in the power grid during the next working period. This not only avoids overuse of some bridge arms with high aging levels, thereby extending the service life of the inverter, but also reduces the degree of thermal coupling impact on components in bridge arms with high aging levels, lowers the thermal resistance of the components, and extends the service life of components in bridge arms with high aging levels. At the same time, this embodiment adjusts the output phase sequence according to the power demand of the power grid to adapt to changes in the power grid load, which helps maintain the quality of inverter output voltage and current, reduces harmonic interference, and improves the power quality of the power connected to the grid. Finally, by adjusting the output phase sequence of the bridge arms, the inverter can adjust the matching strategy between the bridge arms and the phase sequence to cope with fluctuations in power grid consumption, thereby improving the overall operating performance and stability of the power generation system.

[0042] In this embodiment, the inverter control method can also be used in other conversion devices such as energy storage converters that participate in three-phase imbalance mitigation. The energy storage converter converts the DC power in the DC energy storage system into AC power and feeds it into the grid, realizing the release of electrical energy from the DC energy storage system; or it converts the AC power from the grid into DC power and stores it in the DC energy storage system, realizing the storage of electrical energy. The DC energy storage system in the energy storage converter can be a new energy battery, realizing energy conversion and bidirectional flow between the energy storage battery and the grid.

[0043] The application of new energy batteries in daily life and industry is becoming increasingly widespread. New energy batteries are not only used in energy storage power systems such as hydropower, thermal power, wind power, and solar power plants, but also widely used in electric vehicles such as electric bicycles, electric motorcycles, and electric cars, as well as in aerospace and other fields. With the continuous expansion of the application fields of power batteries, the market demand is also constantly increasing. In the embodiments of this application, the battery involved can be a battery cell, also known as a battery unit. A battery cell refers to a basic unit that can realize the mutual conversion of chemical energy and electrical energy, and can be used to make battery modules or battery packs to supply power to electrical devices. A battery cell can be a rechargeable battery, which refers to a battery cell that can be recharged after discharge to activate the active materials and continue to be used. Battery cells can be lithium-ion batteries, sodium-ion batteries, sodium-lithium-ion batteries, lithium metal batteries, sodium metal batteries, lithium-sulfur batteries, magnesium-ion batteries, nickel-metal hydride batteries, nickel-cadmium batteries, lead-acid batteries, etc., and the embodiments of this application are not limited to these.

[0044] In this application embodiment, the battery cell can refer to any shape, such as a square cell or a round cell. The battery cell typically refers to a battery cell, which is one of the basic units constituting a battery. The battery cell is the core component of a battery, responsible for storing and releasing electrical energy. A battery cell can be a lithium-ion battery cell (Li-ion Cell), a lithium-polymer battery cell (Li-polymer Cell), a nickel-metal hydride battery cell (NiMH Cell), etc. This application embodiment does not limit the type of battery cell; it can be selected according to the actual application scenario. In this application embodiment, the battery cell is the core component of a battery pack. A battery pack typically includes multiple battery cells, which are combined together to provide the required electrical capacity and voltage. The components of a battery pack include at least: individual battery cells, a battery management system (BMS), a casing, connecting harnesses, connectors, and interfaces. These components work together to combine the individual battery cells into a fully functional battery pack for various application scenarios. For example, battery packs can be used in electric vehicles, energy storage systems, portable electronic devices, solar energy systems, wind energy systems, emergency backup power supplies, power tools, or electric bicycles, etc. This application does not impose any limitations on these applications; specific applications can be selected based on actual usage scenarios.

[0045] It should be noted that the battery pack can use different types of battery cells, such as lithium-ion batteries, nickel-metal hydride batteries, lithium polymer batteries, etc., depending on the specific application requirements and performance specifications.

[0046] In this embodiment, the battery may also be a single physical module comprising one or more battery cells to provide higher voltage and capacity. When there are multiple battery cells, the multiple battery cells are connected in series, parallel, or mixed via a busbar.

[0047] In this embodiment, the inverter control method can be applied to the inverter. Figure 1 This is a schematic diagram of the hardware structure of a power generation system including an inverter, provided in an embodiment of this application. Figure 1 As shown, the inverter 10 may include an inverter circuit 101, a commutation relay group 102, and a commutation control unit 103. The inverter circuit 101 includes multiple parallel bridge arms (e.g., three-phase bridge arms composed of V1-V2, V3-V4, and V5-V6 respectively), connected to the photovoltaic array 20. The inverter circuit 101 is used to convert the direct current generated by the photovoltaic array into alternating current. The commutation relay group 102 is connected to each bridge arm in the inverter circuit 101 and the power grid 30.

[0048] The commutation control unit 103 is used to acquire the aging data of each bridge arm in the three-phase bridge arm during the current working period and the load status of each phase sequence in the power grid during the next working period; based on the aging data of each bridge arm in the three-phase bridge arm corresponding to the current working period and the load status of each phase sequence in the next working period, it establishes the matching relationship between each bridge arm and each phase sequence in the next working period; based on the matching relationship, it controls the commutation relay group to connect each bridge arm to the corresponding phase sequence.

[0049] The commutation control unit 103 can be an independent chip. When the commutation control unit 103 is an independent chip, it is connected to the inverter's control chip. The commutation control unit 103 can also use the remaining computing power of the inverter's original core control chip. That is, the commutation control unit 103 is a functional module of the inverter chip.

[0050] The commutation control unit 103 can be an integrated circuit chip with signal processing capabilities, such as a general-purpose processor, a digital signal processor (DSP), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor can be a microprocessor or any conventional processor, etc.

[0051] In this embodiment, the commutation relay group includes multiple commutation relays, and each commutation relay includes multiple relay switches. Each bridge arm of the inverter circuit is connected to each phase sequence of the power grid through the multiple relay switches in the commutation relays. The number of commutation relays, relay switches, bridge arms of the inverter and phase sequence in the power grid may be the same or different.

[0052] It should be noted that the description of the inverter in the embodiments of this application is similar to the description of the inverter control method below, and has similar beneficial effects as the inverter control method. These will be described in detail in the following embodiments, and therefore will not be repeated here. For technical details not disclosed in the embodiments, please refer to the description of the inverter control method in this application for understanding.

[0053] In the embodiments of this application, the main body executing the inverter control method is the inverter's commutation control unit. The technical solution of this application will be described in detail below with reference to the accompanying drawings.

[0054] Figure 2 This is an optional flowchart illustrating the inverter control method provided in the embodiments of this application. Figure 1 ,like Figure 2 As shown, the inverter control method provided in this application embodiment can be implemented through steps S201 to S203:

[0055] Step S201: Obtain the aging data of each bridge arm in the three-phase bridge arm during the current working period and the load status of each phase sequence in the power grid during the next working period.

[0056] In this embodiment, the three-phase imbalance rate of the power grid is used to measure the degree of inconsistency in amplitude between the three phases of the power grid, that is, the difference in amplitude of voltage or current of each phase exceeds a preset range, such as 2%. If the three-phase imbalance rate of the power grid exceeds 2%, it indicates that the power grid has been in a state of three-phase imbalance for a long time. The aging degree of the bridge arm with high grid load in the three-phase bridge arm of the inverter connected to the power grid will be significantly higher than that of the other two bridge arms. At this time, it is necessary to balance the aging of the bridge arms to slow down the aging degree of the bridge arm with high load.

[0057] In this embodiment, the components on each bridge arm may include insulated-gate bipolar transistors (IGBTs) and diodes, with current conversion achieved through the on and off states of the IGBTs. The causes of IGBT aging mainly include thermal aging, electrical aging, mechanical aging, differences in component materials, inverter topology, differences in operating environment, thermal management design, manufacturing processes, maintenance, and operating habits. These factors include both internal and external causes within the inverter. However, for components on different bridge arms within the same inverter, the three-phase imbalance of the power grid where the inverter is located is relatively fixed, and the circuit principles and the processes, principles, and materials of the components themselves are similar across different bridge arms. Therefore, the aging degree of each bridge arm component can be assessed solely by measurable external characteristics such as the cumulative energy conversion of each bridge arm in the three-phase bridge arms of the inverter and the difference in equipment temperature rise under the same power. This simplifies the assessment of the aging degree of components on different bridge arms within a single inverter.

[0058] In this embodiment of the application, the aging degree of each bridge arm can be determined by the historical usage data of each bridge arm. The historical usage data can be the cumulative power conversion of each bridge arm and the temperature rise difference of each bridge arm under the same power. The temperature rise difference can refer to the temperature change value between the temperature of each bridge arm at a certain power (e.g., the rated power) when the inverter is in its initial state, that is, when the inverter is first used, and the temperature of the current inverter at that power.

[0059] In this embodiment, the influence of the cumulative power conversion of each bridge arm on the aging degree of each bridge arm can be obtained based on the cumulative power conversion amount of each bridge arm. For example, the bridge arm with a higher cumulative power conversion amount has a higher aging degree. The influence of temperature on the aging degree of each bridge arm can be determined based on the temperature rise difference of each bridge arm under the same power. For example, if the temperature difference of one bridge arm is 10 degrees Celsius (°C) and the temperature difference of another bridge arm is 15°C, the bridge arm with the higher temperature difference will have more severe thermal aging, which will lead to increased thermal expansion and thermal stress of the components in that bridge arm, resulting in a higher aging degree.

[0060] After determining the impact of energy conversion on the aging degree of each bridge arm and the impact of temperature on the aging degree of each bridge arm, aging data for each bridge arm can be obtained by weighting calculations using different coefficients to measure the aging degree.

[0061] Here, the aging data can be a dimensionless value, ranging from 0 (new) to 1 (fully aged). The working environment of different bridge arms of the same inverter is similar, and the parameters related to the degree of aging, such as operating temperature, switching frequency, number of thermal cycles, and voltage stress, are also similar. Therefore, in this embodiment, the degree of aging of the bridge arm can be calculated by the influence of the power conversion on the degree of aging of each bridge arm and the influence of temperature on the degree of aging of each bridge arm.

[0062] Therefore, in this embodiment of the application, when the three-phase imbalance rate of the power grid meets the adjustment conditions, historical usage data of the components on the bridge arm can be obtained, such as the cumulative power conversion of each bridge arm and the temperature rise difference of each bridge arm under the same power, and the aging data of each bridge arm can be calculated based on the historical usage data.

[0063] In some embodiments, the inverter can be a photovoltaic inverter, and the operating period can be the time of day when the sun is shining. After sunset each day, when the voltage output by the photovoltaic array falls below a preset threshold, the inverter will shut down. At this time, the connection between the bridge arms and the grid phase sequence can be adjusted to achieve aging balance of the inverter's bridge arms. The next operating period can be the following day. The period between today's operating period and tomorrow's operating period is the inverter's shutdown phase. During the shutdown phase, the output phase sequence of each bridge arm in the inverter can be adjusted so that it can be connected to the grid with the adjusted connection relationship in the next operating period, thus achieving aging balance of the inverter.

[0064] In some embodiments, the inverter can be a photovoltaic inverter, and the operating period can be the time of day when the sun is shining. After sunset each day, when the voltage output of the photovoltaic array falls below a preset threshold, the inverter will shut down. At this time, the connection between the bridge arms and the grid phase sequence can be adjusted to achieve aging balance of each bridge arm of the inverter. The next operating period can be the following day. During the shutdown phase of today, the output phase sequence of each bridge arm in the inverter is adjusted, and in the next operating period, the inverter is connected to the grid with the adjusted connection relationship to achieve aging balance of the inverter.

[0065] In some embodiments, the commutation control unit can communicate with the upper-level master station (i.e., the energy management system (EMS) or supervisory control and data acquisition (SCADA) system of the power generation network where the inverter is located) to obtain the power load requirements of each phase sequence in the power grid for the next day. The power load requirements of the power grid for the next day can also be obtained by the commutation control unit predicting the possible imbalance of the three-phase power in the system for the next day based on the historical load data of each phase sequence in the power grid, thus obtaining the predicted conversion power (i.e., load status) of each phase sequence for the next day. Here, the load status of each phase sequence in the next working period can refer to the predicted power consumption of each phase sequence in the power grid for the next day.

[0066] Step S202: Based on the aging data of each bridge arm in the three-phase bridge arm corresponding to the current working period and the load status of each phase sequence in the next working period, establish the matching relationship between each bridge arm and each phase sequence in the next working period.

[0067] In this embodiment of the application, when the three-phase imbalance rate of the power grid meets the adjustment conditions, historical usage data of the components on the bridge arms can be obtained, such as the cumulative energy conversion of each bridge arm and the temperature rise difference of each bridge arm under the same power. Based on the historical usage data, the aging data of each bridge arm can be calculated. After determining the aging data of each bridge arm, the bridge arms with the highest and lowest aging degree can be identified. Based on the load conditions of each phase sequence of the power grid, the predicted power consumption of each phase sequence in the power grid for the next day can be determined, that is, the power consumption of the loads connected to each phase sequence. The phase sequences with the highest and lowest power consumption in the power grid for the next day can be identified.

[0068] The inverter can adjust the output phase sequence of each arm during the daily shutdown phase, and output AC power the next day using the adjusted output phase sequence. Here, the adjustment can be to match the arm with the highest degree of aging to the phase sequence with the lowest grid power consumption the next day, and vice versa.

[0069] It should be noted that when adjusting the output phase sequence of each arm in the inverter, it is done on the premise of keeping the phase sequence of the grid connection point unchanged, that is, ensuring that the phase sequence of the inverter is consistent with the phase sequence of the grid, that is, the order in which the three-phase AC voltage or current of the inverter and the grid reaches their maximum values ​​is the same.

[0070] Step S203: Based on the matching relationship, control the commutation relay group to connect each bridge arm to the corresponding phase sequence.

[0071] In some embodiments, a controllable commutation relay group can be added at the power outlet of the inverter, i.e. before the connection node with the grid. The commutation relay group can be a set of relays connected to each bridge arm and each phase sequence respectively. The commutation relay group is used to adjust the output phase sequence of each bridge arm in the inverter and connect each bridge arm to the corresponding phase sequence.

[0072] This application embodiment adjusts the output phase sequence of each bridge arm by using aging data of each bridge arm and the load conditions of each phase sequence in the power grid during the next working period. This not only avoids overuse of some bridge arms with high aging levels, thereby extending the service life of the inverter, but also reduces the degree of thermal coupling impact on components in bridge arms with high aging levels, lowers the thermal resistance of the components, and extends the service life of components in bridge arms with high aging levels. At the same time, this application embodiment adjusts the output phase sequence according to the power demand of the power grid to adapt to changes in the power grid load, which helps maintain the quality of inverter output voltage and current, reduces harmonic interference, and improves the power quality of the power connected to the grid. Finally, by adjusting the output phase sequence of the bridge arms, the inverter can adjust the matching strategy between the bridge arms and the phase sequence to cope with fluctuations in power grid consumption, thereby improving the overall operating performance and stability of the power generation system.

[0073] Figure 3 This is an optional flowchart illustrating the inverter control method provided in the embodiments of this application. Figure 2 ,like Figure 3 As shown, step S202 in the inverter control method provided in this application embodiment can be implemented through steps S301 to S303:

[0074] Step S301: Determine the order of aging degree of the three-phase bridge arms based on the aging data of each bridge arm in the three-phase bridge arm corresponding to the current working period.

[0075] In this embodiment of the application, the aging data is calculated based on the historical usage data of the components on each bridge arm of the inverter. The aging data is a dimensionless value between 0 and 1. Based on the calculated aging data of each bridge arm, the degree of aging in each bridge arm of the inverter can be determined, thereby obtaining the aging order of the three-phase bridge arms.

[0076] Step S302: In each phase sequence of the power grid, determine the load sequence of each phase sequence in the next working period based on the load status of each phase sequence in the next time period.

[0077] In this embodiment of the application, after determining the load status of each phase sequence in the power grid in the next working period, the load status of each phase sequence in the power grid in the next working period can be determined to obtain the load order of each phase sequence in the next working period.

[0078] Step S303: Based on the aging degree sequence and load sequence, establish the matching relationship between each bridge arm and each phase sequence in the next working period.

[0079] In the embodiments of this application, after determining the aging degree sequence and load sequence, a matching relationship between each bridge arm and each phase sequence can be established in the next working period. For example, the bridge arm with the highest aging degree can be matched with the phase sequence with the lowest load on the next day, and the bridge arm with the lowest aging degree can be matched with the phase sequence with the highest load. This can avoid overuse of bridge arms with high aging degree, thereby extending the service life of the inverter.

[0080] In some embodiments, step S303 can be implemented by step S3031:

[0081] Step S3031: Based on the aging degree order and load order, establish a first matching relationship between bridge arms and phase sequences that meet the first condition in both aging degree and load during the next working period; a second matching relationship between bridge arms and phase sequences that meet the second condition in both aging degree and load; and a third matching relationship between bridge arms and phase sequences that meet the third condition in both aging degree and load. Wherein, the first condition represents the highest aging degree and the lowest load; the second condition represents the lowest aging degree and the highest load; and the third condition represents that both aging degree and load are between the highest and the lowest.

[0082] In this embodiment of the application, based on the aging degree order and load order, the bridge arm with the highest and lowest aging degree among the three-phase bridge arms, as well as the phase sequence with the highest and lowest load in the power grid the next day, can be determined. In the next working period, the bridge arm with the highest aging degree can be assigned to the phase sequence with the lowest load the next day, the bridge arm with the lowest aging degree can be assigned to the phase sequence with the highest load, and the bridge arm with the middle aging degree can be assigned to the phase sequence with the middle load.

[0083] This application embodiment adjusts the output phase sequence of each bridge arm of the inverter so that the output phase sequence corresponding to the bridge arm with the highest degree of aging in the inverter is the phase sequence with the lowest power consumption, and the output phase sequence corresponding to the bridge arm with the lowest degree of aging is the phase sequence with the highest power consumption, so as to balance the aging degree of each bridge arm of the inverter and extend the service life of the inverter.

[0084] In some embodiments, Figure 4 This is an optional circuit diagram of the commutation relay group provided in an embodiment of this application, such as... Figure 4 As shown, the commutation relay group 401 includes multiple commutation relays (such as...). Figure 4 (402, 403, and 404 in the text), each commutation relay includes multiple relay switches (such as...) Figure 4 The phase-commutation relay 402 includes multiple relay switches 4021, 4022, and 4023. Each bridge arm is connected to the corresponding phase sequence of the power grid through the multiple relay switches in the phase-commutation relay. For example, bridge arm #1 is connected to each phase sequence ABC through the phase-commutation relay 402. Based on Figure 4 The provided commutation relay group can also be implemented via step S2031:

[0085] Step S2031: Based on the first matching relationship, the second matching relationship and the third matching relationship, close the relay switch in the commutation relay corresponding to each bridge arm that is connected to the corresponding phase sequence, so as to connect each bridge arm to the corresponding phase sequence.

[0086] In the embodiments of this application, the first matching relationship is the bridge arm with the highest degree of aging connected to the phase sequence with the lowest load, the second matching relationship is the bridge arm with the lowest degree of aging connected to the phase sequence with the highest load, and the third matching relationship is the bridge arm with a moderate degree of aging connected to the phase sequence with a moderate load.

[0087] based on Figure 4 Based on the first matching relationship, assuming that the first bridge arm with the highest aging degree is #1 and the second phase sequence with the lowest power consumption in the next working period is B, then in the commutation relay 402 corresponding to the first bridge arm #1, the relay switch connecting the first bridge arm #1 and the second phase sequence B is 4022. At this time, 4022 can be closed and 4021 and 4023 can be opened, so that the first bridge arm #1 and the second phase sequence B are connected.

[0088] In this embodiment of the application, based on the second matching relationship, assuming that the third bridge arm with the lowest aging degree is #3, and the first phase sequence with the highest power consumption in the next working period is A, then in the commutation relay 404 corresponding to the third bridge arm #3, the relay switch connecting the third bridge arm #3 and the first phase sequence A is 4041. At this time, 4041 can be closed and 4042 and 4033 can be opened, so that the second bridge arm #3 and the first phase sequence A are connected.

[0089] Based on the third matching relationship, the second bridge arm #2 with the moderate aging degree is connected to the third phase sequence C with the moderate aging degree. At this time, the relay switch 4033 in the commutation relay 403 can be closed, and 4031 and 4032 can be opened to realize the connection between the second bridge arm #2 and the third phase sequence C. The inverter outputs AC power with this output phase sequence in the next working period.

[0090] In this embodiment, the connection relationship between the output phase sequence of the inverter and the three-phase bridge arms of the inverter can be shown in Table 1 below:

[0091] Table 1

[0092]

[0093] In some embodiments, the inverter can be a photovoltaic inverter. After sunset each day, the intensity of sunlight drops sharply, the direct current generated by the photovoltaic array decreases, and the voltage delivered by the photovoltaic array to the inverter decreases. When the voltage is lower than the voltage threshold, that is, when the input voltage of the inverter is less than the voltage threshold, the inverter will stop operating and will no longer perform inversion conversion (i.e., DC to AC). At this time, the inverter is in a shutdown state.

[0094] In this embodiment, the current working period can be the time period during which the inverter is in operation today, and the next working period can be the time period during which the inverter is in operation tomorrow. Therefore, there is a shutdown phase between today and tomorrow. In this embodiment, the output phase sequence of the inverter can be adjusted during the shutdown phase so that the output phase sequence corresponding to the bridge arm with the highest degree of aging in the inverter tomorrow is the phase sequence with the least load, and the output phase sequence corresponding to the bridge arm with the lowest degree of aging is the phase sequence with the most load, so as to balance the aging degree of each phase sequence of the inverter and extend the service life of the inverter.

[0095] This application embodiment achieves the adjustment of the inverter's output phase sequence through various opening and closing states of the commutation relay group. While ensuring that the grid-connected phase sequence remains unchanged, it can balance the aging of power electronic components on the three-phase bridge arm and extend the inverter's service life.

[0096] In this embodiment, the aging data of the three-phase bridge arm can be calculated from the historical usage data of the three-phase bridge arm. Correspondingly, the inverter control method provided in this embodiment may further include steps S1 to S4:

[0097] Step S1: Obtain historical usage data of components on each bridge arm of the inverter; historical usage data includes the rated power conversion of each bridge arm of the inverter and the cumulative power conversion of each bridge arm.

[0098] In some embodiments, the historical usage data for the three-phase arms includes the rated energy conversion of each arm of the inverter and the cumulative energy conversion of each arm. Here, the rated energy conversion of each arm is the total rated energy conversion of each arm at the time of inverter design, expressed in kilowatt-hours (kWh). The rated energy conversion of each arm may be the same or different. The cumulative energy conversion of each arm is the cumulative energy converted by each arm from the start of its operation to the present.

[0099] Step S2: Determine the first aging value of each bridge arm based on the rated power conversion of each bridge arm and the cumulative power conversion of each bridge arm.

[0100] In some embodiments, the aging of inverter arms is usually caused by long-term use and high temperature. Therefore, the embodiments of this application combine the effects of these two aspects on the aging of the arms to obtain the aging degree of each arm.

[0101] Here, the rated power conversion of each bridge arm is the rated total power conversion of each bridge arm when the inverter is designed, the cumulative power conversion of each bridge arm is the power converted by each bridge arm from the start of use to the present, and the first aging value of the bridge arm is used to characterize the effect of the power conversion of each bridge arm on the aging of the bridge arm. Here, the first aging value A1 can be realized by formula (1):

[0102] A1 = E rated / E total (1);

[0103] Among them, E total Total power conversion capacity designed for each bridge arm; E rated The cumulative electrical energy conversion amount for each bridge arm is the cumulative electrical energy converted from the initial use state to the current state of each bridge arm.

[0104] Step S3: Compare the first temperature of each bridge arm in the first state with the second temperature in the second state to obtain the second aging value of each bridge arm; wherein, the first state is the initial use state of the inverter, the second state is the current use state of the inverter, and the output power of the inverter is the same when the inverter is in the first state or the second state.

[0105] In some embodiments, the second aging value ΔT rated The value used to characterize the effect of temperature change on the aging of each bridge arm under a fixed output power can be the temperature change at the rated power, i.e., the second aging value ΔT. rated It is the difference between the temperature of the bridge arm under its initial operating condition (i.e., the first temperature) and the temperature under its current operating condition (i.e., the second temperature) at its rated output power.

[0106] Step S4: Based on the preset first weight parameter, the first aging value and the second aging value are weighted and calculated to obtain the aging data of each bridge arm.

[0107] In this embodiment of the application, by simulating historical usage data, the influence weights of energy conversion and temperature change on the degree of aging can be obtained, thereby obtaining the first weight parameter. The first weight parameter includes k1 and k2, which represent the influence coefficients of energy conversion and temperature change on the degree of aging, respectively. The weighted calculation of the first aging value and the second aging value through the first weight parameter can be achieved by formula (2):

[0108] Aging Index = k1·(E rated / E total )+k2·ΔT rated (2);

[0109] Wherein, Aging Index is the aging data of the bridge arm; k1 and k2 can be empirical parameters or parameters obtained through training, and this application embodiment does not impose any restrictions.

[0110] This application embodiment calculates the aging degree of each bridge arm by measuring the power conversion amount and temperature change of each bridge arm. This allows for a more comprehensive and accurate assessment of the aging degree of each bridge arm. Based on the calculated aging degree, commutation is performed, which can more accurately protect the bridge arms with higher aging degrees and extend the service life of the inverter.

[0111] In some embodiments, the commutation control unit can obtain the load status of each phase sequence in the power grid on the next day by communicating with the upper master station (i.e., EMS or SCADA system), or the commutation control unit can predict the possible unbalanced power of the three phases of the system on the next day based on the historical load data of each phase sequence in the power grid, and obtain the load status of each phase sequence on the next day.

[0112] Therefore, the inverter control method provided in this application embodiment can also be implemented through steps S1 and S2:

[0113] Step S1: Obtain historical load data for each phase sequence in the power grid; historical load data includes the cumulative converted power of each phase sequence and the current converted power of each phase sequence during the current working period.

[0114] In some embodiments, the power grid can be connected to the inverter via three phase sequences (A, B, and C). Historical load data can include the cumulative converted power of each phase sequence and the current converted power during the current operating period. The cumulative converted power of each phase sequence is the cumulative power consumption of that phase sequence. The current operating period can be today, and the current converted power consumption during the current operating period can be the power consumption of each phase sequence today. This embodiment of the application can predict the power consumption of each phase sequence in the next operating period (e.g., tomorrow) by using today's and historical power consumption. During the inverter's shutdown phase today, the output phase sequence of each bridge arm is adjusted so that tomorrow, the power converted by the inverter will be fed into the power grid based on the adjusted output phase sequence.

[0115] Here, P t，A P t，B P t，C P represents the current converted electrical quantity of each phase sequence in the power grid during the current working period; cum，A P cum，B P cum，CThese represent the cumulative converted electrical quantities for each phase sequence of the power grid.

[0116] Step S2: Based on the cumulative and current conversion power of each phase sequence, predict the conversion power of each phase sequence in the power grid during the next working period to obtain the load status of each phase sequence in the next working period; the load status is used to characterize the power consumption of each phase sequence in the next working period.

[0117] In this embodiment of the application, a regression prediction model based on historical data can be pre-trained. Based on this model, the load status of each phase sequence in the power grid in the next working period can be predicted to obtain the power consumption of each phase sequence in the power grid in the next working period.

[0118] This application embodiment can optimize the inverter control strategy by predicting the conversion power in the next working period of each phase sequence. This can not only extend the service life of the inverter, but also improve the overall efficiency and reliability of the power generation system.

[0119] In some embodiments, step S2 can be implemented by steps S21 and S22:

[0120] Step S21: Based on the cumulative converted power and current converted power of each phase sequence, determine the current three-phase imbalance rate of the power grid during the current working period.

[0121] In some embodiments, the current three-phase imbalance rate characterizes the degree of three-phase imbalance of the power grid during the current operating period, and the current three-phase imbalance rate U t This can be achieved using formula (3):

[0122]

[0123] Step S22: Based on the preset second weight parameter, the current three-phase imbalance rate, the cumulative conversion power of each phase sequence and the current conversion power, predict the load status of each phase sequence in the next working period, and obtain the load status of each phase sequence in the next working period.

[0124] In some embodiments, the second weight parameter may be obtained through pre-training and can be estimated from historical data using the least squares method when training the regression prediction model.

[0125] Here, based on the preset second weighting parameter, the current three-phase imbalance rate, the cumulative conversion power of each phase sequence, and the current conversion power, the load status of each phase sequence in the next working period can be predicted by formula (4):

[0126] P t+1，i =β 0i +β 1i P t，i +βi2 P cum，i +β 3i U t +∈ t+1，i (4);

[0127] Where i∈{A, B, C} represents one of the three phases; β 0i β 1i β i2 β 3i It is the second weight parameter; ∈ t+1，i It is the error term, which can be normally distributed.

[0128] This application embodiment trains a prediction model for the power consumption of each phase sequence of the power grid using historical data of the power grid. Based on the prediction model, the power consumption of the power system in the next working period is predicted, and the output phase sequence of the inverter is adjusted more accurately based on the prediction results.

[0129] In some embodiments, after obtaining the aging degree of each bridge arm and the predicted power consumption of each phase sequence of the power grid for the next day, the bridge arm with the highest aging degree can be assigned to the phase sequence with the lowest corresponding system load for the next day, and the bridge arm with the lowest aging degree can be assigned to the phase sequence with the highest system load for the next day, so as to achieve aging balance of the three-phase bridge arms.

[0130] The following will describe an exemplary application of the embodiments of this application in a real-world application scenario.

[0131] As a power source for distribution networks, distributed photovoltaic (PV) systems can adjust the three-phase output power by controlling the switching angle and conduction time of the power electronic components on the three-phase bridge arms of the PV inverter, thereby reducing the three-phase imbalance rate of the system. However, this method can lead to differences in the aging degree of the power electronic components on the inverter bridge arms. Specifically, the bridge arm with the higher load among the three-phase bridge arms participating in three-phase imbalance mitigation will show a significantly higher aging degree than the other two phases. When the aging degree reaches a certain threshold, the entire inverter will be taken out of service, while the power electronic equipment of the other two bridge arms has not yet reached the retirement aging threshold. This means that when inverters without aging balancing capabilities participate in three-phase imbalance mitigation, the overall service life of the inverter will be reduced. Therefore, aging balancing technology is needed for inverters participating in three-phase imbalance mitigation.

[0132] Based on the problems existing in the related technologies, this application proposes that the service life of the inverter shortened due to the aging of a certain phase bridge arm can be extended by aging balancing means, namely, balancing commutation technology.

[0133] In this embodiment, only a three-phase commutation device and a commutation coordination control unit need to be added at the inverter output end, before the grid connection point, i.e., after the inverter body and the DC power input from the photovoltaic modules have completed AC / DC conversion in the main electrical topology and power electronic equipment. By statistically analyzing the temperature and output power of the power electronic devices and predicting the three-phase imbalance for the next day, the commutation coordination control unit adjusts the output phase (i.e., phase sequence) of the three-phase bridge arm power electronic devices during the daily photovoltaic inverter shutdown phase, and simultaneously adjusts the opening and closing state of the relay group inside the commutation device. While ensuring that the grid connection phase sequence remains unchanged, the aging of the power electronic components on the three-phase bridge arm is balanced, which can extend the service life of the inverter. It can be applied to relays of any electrical topology configuration, and can also be used in energy storage converters and other types of equipment that can participate in three-phase imbalance management, thus having versatility.

[0134] This application embodiment calculates the degree of aging imbalance of the power electronic devices on the three-phase bridge arms by measuring the operating temperature and cumulative output power of the power electronic devices on the three-phase bridge arms of the inverter. By synchronously adjusting the output phase of the bridge arms and the opening and closing state of the commutator relay group through the main controller, while keeping the phase sequence at the grid connection point unchanged, the output phase sequence of the bridge arms is adjusted to reduce the unevenness of the aging of the power electronic components of each bridge arm and extend the overall life of the photovoltaic inverter.

[0135] Meanwhile, photovoltaic (PV) inverters are key components of PV systems, responsible for converting direct current (DC) generated by solar panels into alternating current (AC) for grid or load use. The aging process of power electronic components in PV inverters is affected by various factors, such as differences in component materials, inverter topology, operating environment, thermal management design, manufacturing processes, maintenance, and operating habits. These factors include both internal and external causes. Due to the complexity and interrelationships of these factors, accurately calculating the aging degree of power electronic components in PV inverters is a pressing issue. Related technologies typically employ experimental testing, condition monitoring, and lifetime prediction models to assess the aging status and remaining lifespan of components.

[0136] Based on this, this application provides another method for calculating the aging degree of power electronic units in the three-phase bridge arm of an inverter. This method is applied to power electronic devices on different bridge arms within the same inverter, and the three-phase imbalance of the power system in which the inverter is located is relatively fixed. Therefore, this application does not delve into complex circuit principles and the differences in the processes, principles, and materials of different types of power electronic devices. Instead, it assesses the aging degree of power electronic devices solely through measurable external characteristics such as the cumulative power conversion of the three-phase bridge arm power electronic devices and the difference in temperature rise of the devices under the same power. This simplifies the assessment of the aging degree of power electronic components in different bridge arms within a single inverter.

[0137] In some embodiments, the commutation control unit can communicate with the host computer to obtain the host computer's prediction of the three-phase imbalance of the power grid where the inverter is located. Combined with the assessment of the aging degree of the power electronic equipment of the three-phase bridge arm of the inverter, the unit can adjust the phase sequence of the bridge arm with a lighter aging degree to correspond to the phase sequence of the heavier load, and the bridge arm with a heavier aging degree to correspond to the phase sequence of the lighter load, so as to reduce the uneven aging degree of the power electronic components of each bridge arm and extend the overall life of the photovoltaic inverter.

[0138] This application provides an optimized design scheme for an inverter. Compared with the original photovoltaic inverters in related technologies, it adds a set of commutation relays, a commutation coordination control unit, and an algorithm program, a three-phase imbalance prediction program, and an aging balance control program running on the commutation coordination control unit for estimating the aging degree of the three-phase bridge arms of the inverter.

[0139] Figure 5 This is a schematic diagram of the hardware structure of the inverter provided in the embodiments of this application, as shown below. Figure 5 As shown, from a hardware perspective, this embodiment of the application adds a commutation coordination control unit 501 after the inverter core energy (DC / AC) conversion electrical topology. The commutation coordination control unit 501 can be an independent chip (in this case, the independent chip is connected to the inverter's control chip), or it can use the remaining computing power of the inverter's original core control chip (i.e., the commutation coordination control unit 501 is a functional module of the inverter chip). Furthermore, a set of controllable commutation relay groups 502 is added at the inverter power outlet, i.e., before the connection node with the grid.

[0140] Figure 5 A simplified circuit diagram of a photovoltaic inverter in the related technology is also shown. In the photovoltaic inverter circuit 503 shown in the figure, only a three-phase bridge arm composed of insulated gate bipolar transistors (IGBTs) such as V1-V2, V3-V4, and V5-V6 is shown to realize the DC to three-phase AC power conversion capability. Here, V1-V2, V3-V4, and V5-V6 are the power electronic devices 504 of the inverter.

[0141] In this embodiment, the commutation control unit 501 is mainly responsible for communicating with the existing core control program of the inverter to obtain relevant data for calculating the aging of the three-phase bridge arms of the inverter, such as the total power conversion of the inverter design, the temperature change of the inverter at different power levels, and the accumulated power conversion of each bridge arm in the inverter. The commutation control unit 501 also has storage capacity, which can store historical data to improve the accuracy of aging calculation. It can also calculate the aging degree of the three-phase bridge arms in the inverter based on the above data; predict the imbalance of the three-phase power output the next day; and control the commutation relay group to switch the correspondence between the three-phase bridge arms and the grid.

[0142] The commutation control unit 501 can communicate with the existing core control program of the inverter to obtain data such as the temperature change of the three-phase bridge arm power electronic components under different output power and the cumulative electrical energy converted by each bridge arm from the initial state in real time. It can also periodically call the three-phase bridge arm aging degree estimation program to estimate the aging degree of the power electronics of each bridge arm.

[0143] The commutation control unit 501 can communicate with the upper master station (i.e., the energy management system (EMS) or supervisory control and data acquisition (SCADA) system of the power distribution network where the inverter is located) to determine the three-phase imbalance of the power grid, or predict the possible imbalance of the three-phase power of the system the next day through its own three-phase imbalance prediction program.

[0144] Based on the predicted results of the unbalanced power supply the next day and the estimated results of the aging degree of the power electronics of each bridge arm of the inverter, the commutation coordination control unit 501 can call the three-phase bridge arm aging control program to control the commutation relay group 502 to switch the system phase sequence corresponding to each bridge arm. The next day, the inverter directly starts the bridge arm electronic equipment to perform DC / AC conversion according to the system phase sequence connected to the bridge arm.

[0145] Figure 6 This is a flowchart illustrating the aging balance control method provided in this application embodiment, with the commutation coordination control unit as the executing entity. Figure 6 As shown, the aging balance control method can be implemented through steps S601 to S605:

[0146] Step S601: Obtain the temperature change of each bridge arm power electronic component under different power levels.

[0147] In this embodiment, the temperature change of each bridge arm power electronic component at different power refers to the temperature change between the initial state, i.e., when the inverter just started to be used, and the current temperature of the inverter at different power.

[0148] Step S602: Obtain the cumulative electrical energy converted by each bridge arm.

[0149] Here, the cumulative electrical energy converted by each bridge arm can refer to the cumulative electrical energy converted by each bridge arm from the start of its use to the present.

[0150] Step S603: Estimate the aging degree of each bridge arm based on the temperature change and cumulative converted electrical energy of the power electronic components of each bridge arm under different power levels.

[0151] In some embodiments, after obtaining the temperature changes and cumulative converted electrical energy of the power electronic components of each bridge arm at different power levels, the aging degree of each bridge arm can be calculated using formula (5):

[0152] Aging Index = k1·(E rated / E total )+k2·ΔT rated (5);

[0153] Among them, the Aging Index is used to characterize the degree of aging; E total The total electrical energy conversion capacity of the design (usually expressed in kilowatt-hours, kWh); ΔT rated Temperature change at rated power (usually expressed in degrees Celsius °C); E rated k1 represents the cumulative electrical energy conversion of each bridge arm; k2 and k1 are aging coefficients used to adjust the weight of the influence of electrical energy conversion and temperature changes on the degree of aging.

[0154] In this embodiment, the degree of aging can be defined as a dimensionless value ranging from 0 (new) to 1 (completely aged). The operating environment of different bridge arms of the same inverter is similar, and the parameters related to the degree of aging, such as operating temperature, switching frequency, number of thermal cycles, and voltage stress, are also similar. Therefore, in this embodiment, the degree of aging of each bridge arm can be represented by formula (6).

[0155] Step S604: Predict the three-phase power imbalance of the power grid connected to the inverter the next day.

[0156] In some embodiments, the forecasting program may employ a regression model based on historical data, such as a linear regression model, an autoregressive model, and a moving average model.

[0157] In some embodiments, P t，A P t，B P t，C These represent the electrical quantities converted in each phase of the power grid today; P cum，A P cum，B P cum，C These represent the cumulative electricity consumption of each phase of the power grid. The three-phase power imbalance rate for today can be calculated using formula (6):

[0158]

[0159] Based on today's three-phase conversion power imbalance rate, the three-phase conversion power P for the next day can be calculated. t+1，A P t+1，B P t+1，C Establish a multiple linear regression model as shown in formula (7):

[0160] Pt+1，i =β 0i +β 1i P t，i +β i2 P cum，i +β 3i U t +∈ t+1，i (7);

[0161] Where i∈{A, B, C} represents one of the three phases; β 0i β 1i β i2 β 3i These are the model parameters (i.e., the parameters for weight adjustment), which can be estimated from historical data using the least squares method; ∈ t+1，i This is the error term, assumed to be normally distributed.

[0162] The commutation control unit can use this model to predict the demand for unbalanced power in each phase of the system the following day.

[0163] Step S605: Switch the phase sequence of the bridge arm corresponding to the system by using the phase switching relay group.

[0164] The commutation control unit can calculate the correspondence between the bridge arm and the system phase sequence for the next day and control the operating group number of the commutation relay group. For example, the bridge arm with the highest calculated aging degree will be assigned to the phase sequence with the lowest corresponding system power consumption for the next day, and the bridge arm with the lowest aging degree will be assigned to the phase sequence with the highest system power consumption for the next day.

[0165] In some embodiments, the commutation relay group is used to connect the output terminal of the bridge arm and the power grid, and is controlled by the commutation coordination control unit. The phase sequence relationship between the inverter bridge arm and the power grid is switched by switching the operating group number of the relay group.

[0166] As in the foregoing embodiments Figure 4 As shown, the commutation relay group is controlled by the commutation coordination unit through the opening and closing of multiple relay switches in the three relay groups 402, 403 and 404, so as to realize the switching of the inverter output terminals #1, #2 and #3 corresponding to the three phases A, B and C of the power grid. The input and output correspondence in Table 2 below can be realized.

[0167] Table 2

[0168]

[0169] like Figure 4As shown, in this embodiment of the application, by changing the opening and closing states of multiple relay switches in the three relay groups 402, 403, and 404 in the commutation relay group, the inverter output terminals #1, #2, and #3 can be switched to the three phases A, B, and C of the power grid. For example, the bridge arm with the highest calculated aging degree can be assigned to the phase sequence with the lowest system power consumption the next day, and the bridge arm with the lowest aging degree can be assigned to the phase sequence with the highest system power consumption the next day.

[0170] Based on the foregoing embodiments, this application further provides a power generation system. Figure 7 This is a schematic diagram of the power generation system provided in the embodiments of this application, such as... Figure 7 As shown, the power generation system includes a photovoltaic array 701, an inverter 702, and a power grid 703 connected in sequence.

[0171] The photovoltaic array 701 is connected to the inverter 702 to convert solar energy into direct current (DC). The inverter 702 includes an inverter circuit, a commutation relay group, and a commutation control unit. The inverter circuit converts DC into alternating current (AC). The commutation control unit acquires the aging data of each arm in the three-phase bridge arm during the current working period and the load status of each phase sequence in the power grid during the next working period. Based on the aging data of each arm in the three-phase bridge arm during the current working period and the load status of each phase sequence in the next working period, it establishes a matching relationship between each arm and each phase sequence in the next working period. Based on the matching relationship, it controls the commutation relay group to connect each arm to the corresponding phase sequence. The commutation relay group is connected to each arm in the inverter and each phase in the power grid. The power grid 703 is connected to the inverter 702 to receive AC power.

[0172] It should be noted that the description of the power generation system in this embodiment is similar to the description of the inverter control method described above, and has similar beneficial effects as the inverter control method; therefore, it will not be repeated here. For technical details not disclosed in the embodiments, please refer to the description of the inverter control method in this application for understanding.

[0173] Based on the foregoing embodiments, this application further provides an inverter. Figure 8 This is a schematic diagram of the inverter provided in the embodiments of this application, as shown below. Figure 8 As shown, the inverter 800 includes an acquisition module 801, an establishment module 802, and a control module 803.

[0174] The acquisition module 801 is used to acquire the aging data of each bridge arm in the three-phase bridge arm during the current working period and the load status of each phase sequence in the power grid during the next working period; the establishment module 802 is used to establish the matching relationship between each bridge arm and each phase sequence in the next working period based on the aging data of each bridge arm in the three-phase bridge arm corresponding to the current working period and the load status of each phase sequence in the next period; the control module 803 is used to control the commutation relay group to connect each bridge arm to the corresponding phase sequence based on the matching relationship.

[0175] In some embodiments, the establishing module 802 is further configured to determine the aging order of the three-phase bridge arms based on the aging data of each bridge arm in the three-phase bridge arm corresponding to the current working period; determine the load order of each phase sequence in the next working period based on the load status of each phase sequence in the next working period; and establish a matching relationship between each bridge arm and each phase sequence in the next working period based on the aging order and the load order.

[0176] In some embodiments, the establishing module 802 is further configured to establish, based on the aging degree order and load order, a first matching relationship between bridge arms and phase sequences that both aging degree and load meet the first condition, a second matching relationship between bridge arms and phase sequences that both aging degree and load meet the second condition, and a third matching relationship between bridge arms and phase sequences that both aging degree and load meet the third condition; wherein, the first condition represents the highest aging degree and the lowest load; the second condition represents the lowest aging degree and the highest load; and the third condition represents that both aging degree and load are between the highest and the lowest.

[0177] In some embodiments, the commutation relay group includes multiple commutation relays, each commutation relay includes multiple relay switches, and each bridge arm is connected to each phase sequence of the power grid through multiple relay switches in a commutation relay; the establishment module 803 is also used to close the relay switches in the commutation relays corresponding to each bridge arm that are connected to the corresponding phase sequence based on the first matching relationship, the second matching relationship and the third matching relationship, so as to connect each bridge arm to the corresponding phase sequence.

[0178] In some embodiments, the inverter further includes: a first acquisition module, configured to acquire historical usage data of components on each bridge arm of the inverter; the historical usage data includes the rated power conversion of each bridge arm and the cumulative power conversion of each bridge arm; a determination module, configured to determine a first aging value of each bridge arm based on the rated power conversion of each bridge arm and the cumulative power conversion of components on each bridge arm; a comparison module, configured to compare a first temperature of each bridge arm in a first state with a second temperature in a second state to obtain a second aging value of each bridge arm; wherein the first state is the initial usage state of the inverter, the second state is the current usage state of the inverter, and the inverter output power is the same when the inverter is in the first state or the second state; and a calculation module, configured to perform weighted calculation on the first aging value and the second aging value based on a preset first weight parameter to obtain aging data of each bridge arm.

[0179] In some embodiments, the inverter further includes: a second acquisition module, configured to acquire historical load data of each phase sequence in the power grid; the historical load data includes the cumulative converted power of each phase sequence and the current converted power of each phase sequence in the current working period; and a prediction module, configured to predict the converted power of each phase sequence in the power grid in the next working period based on the cumulative converted power and the current converted power of each phase sequence, to obtain the load status of each phase sequence in the next working period; the load status is used to characterize the power consumption of each phase sequence in the next working period.

[0180] In some embodiments, the prediction module is further configured to determine the current three-phase imbalance rate of the power grid during the current working period based on the cumulative conversion power and the current conversion power of each phase sequence; and to predict the load status of each phase sequence in the next working period based on the preset second weight parameter, the current three-phase imbalance rate, the cumulative conversion power and the current conversion power of each phase sequence, so as to obtain the load status of each phase sequence in the next working period.

[0181] The description of the inverter in this embodiment is similar to the description of the inverter control method described above, and has similar beneficial effects as the inverter control method; therefore, it will not be repeated here. For technical details not disclosed in the embodiments, please refer to the description of the inverter control method in this application for understanding.

[0182] It should be understood that the phrase "one embodiment" or "an embodiment" throughout the specification means that a specific feature, structure, or characteristic related to the embodiment is included in at least one embodiment of this application. Therefore, "in one embodiment" or "in an embodiment" appearing throughout the specification does not necessarily refer to the same embodiment. Furthermore, these specific features, structures, or characteristics can be combined in any suitable manner in one or more embodiments. It should be understood that in the various embodiments of this application, the sequence numbers of the above steps / processes do not imply a sequential order of execution; the execution order of each step / 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. The sequence numbers of the above embodiments of this application are merely descriptive and do not represent the superiority or inferiority of the embodiments.

[0183] This application uses terms such as "upper," "lower," "top," "bottom," "front," "back," "inner," and "outer" to indicate orientation or positional relationships. This is only for the convenience of describing this application and is not intended to indicate or imply that the device referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation on the scope of protection of this application.

[0184] In the description of this application, it should also be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this application depending on the specific circumstances.

[0185] It should be noted that, 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 that element.

[0186] In the several embodiments provided in this application, it should be understood that the disclosed systems, devices, and methods can be implemented in other ways. The device embodiments described above are merely illustrative. For example, the division of units is only a logical functional division, and in actual implementation, there may be other division methods, such as: multiple units or components may be combined, or integrated into another system, or some features may be ignored or not executed. In addition, the coupling, direct coupling, or communication connection between the various components shown or discussed may be through some interfaces, and the indirect coupling or communication connection between devices or units may be electrical, mechanical, or other forms.

[0187] The units described above as separate components may or may not be physically separate, and the components shown as units may or may not be physical units; they may be located in one place or distributed across multiple network units; some or all of the units may be selected to achieve the purpose of this embodiment according to actual needs. Furthermore, the functional units in the embodiments of this application may all be integrated into one processing unit, or each unit may be a separate unit, or two or more units may be integrated into one unit; the integrated unit may be implemented in hardware or in a combination of hardware and software functional units.

[0188] The above are merely embodiments of this application and are not intended to limit the scope of protection of this application. Any modifications, equivalent substitutions, and improvements made within the spirit and scope of this application are included within the scope of protection of this application.

Claims

1. A control method for an inverter, characterized in that, The control method includes: Obtain the aging data of each arm in the three-phase bridge arm during the current working period and the load status of each phase sequence in the power grid during the next working period; Based on the aging data of each arm in the three-phase bridge arm corresponding to the current working period and the load status of each phase sequence in the next working period, establish the matching relationship between each arm and each phase sequence in the next working period. Based on the matching relationship, the control commutation relay group connects each bridge arm to the corresponding phase sequence.

2. The control method for the inverter according to claim 1, characterized in that, The step of establishing a matching relationship between each bridge arm and each phase sequence in the next working period based on the aging data of each bridge arm in the three-phase bridge arm corresponding to the current working period and the load status of each phase sequence in the next working period includes: Based on the aging data of each arm in the three-phase bridge arm corresponding to the current working period, the aging order of the three-phase bridge arms is determined. In the power grid, the load sequence of each phase sequence in the next working period is determined according to the load status of each phase sequence in the next time period. Based on the aging degree sequence and the load sequence, establish the matching relationship between each bridge arm and each phase sequence in the next working period.

3. The control method for the inverter according to claim 2, characterized in that, The step of establishing the matching relationship between each bridge arm and each phase sequence in the next working period based on the aging degree sequence and the load sequence includes: Based on the aging degree order and the load order, establish a first matching relationship between bridge arms and phase sequences that meet the first condition in the next working period, a second matching relationship between bridge arms and phase sequences that meet the second condition in both aging degree and load, and a third matching relationship between bridge arms and phase sequences that meet the third condition in both aging degree and load. Among them, the first condition represents the highest degree of aging and the lowest load; the second condition represents the lowest degree of aging and the highest load; and the third condition represents both the highest degree of aging and the lowest load.

4. The control method for the inverter according to claim 3, characterized in that, The commutation relay group includes multiple commutation relays, and each commutation relay includes multiple relay switches. Each bridge arm is connected to each phase sequence of the power grid through multiple relay switches in a commutation relay. Based on the matching relationship, controlling the commutation relay group to connect each bridge arm to the corresponding phase sequence includes: Based on the first matching relationship, the second matching relationship, and the third matching relationship, the relay switch in the commutation relay corresponding to each bridge arm and connected to the corresponding phase sequence is closed to connect each bridge arm to the corresponding phase sequence.

5. The control method for the inverter according to any one of claims 1 to 4, characterized in that, The control method further includes: Obtain historical usage data of components on each bridge arm of the inverter; the historical usage data includes the rated power conversion of each bridge arm of the inverter and the cumulative power conversion of each bridge arm; Based on the rated power conversion of each arm of the inverter and the cumulative power conversion of the components on each arm, the first aging value of each arm is determined. The first temperature of each bridge arm in the inverter under the first state and the second temperature under the second state are compared to obtain the second aging value of each bridge arm; wherein, the first state is the initial use state of the inverter, the second state is the current use state of the inverter, and the output power of the inverter is the same when the inverter is in the first state or the second state; Based on a preset first weighting parameter, the first aging value and the second aging value are weighted and calculated to obtain the aging data of each bridge arm.

6. The control method for the inverter according to any one of claims 1 to 5, characterized in that, The control method further includes: Obtain historical load data for each phase sequence in the power grid; the historical load data includes the cumulative converted power of each phase sequence and the current converted power of each phase sequence during the current working period; Based on the cumulative and current conversion power of each phase sequence, the conversion power of each phase sequence in the power grid in the next working period is predicted to obtain the load status of each phase sequence in the next working period; the load status is used to characterize the power consumption of each phase sequence in the next working period.

7. The control method for the inverter according to claim 6, characterized in that, The method of predicting the conversion power of each phase sequence in the power grid during the next working period based on the cumulative conversion power and the current conversion power of each phase sequence, and obtaining the load status of each phase sequence during the next working period, includes: Based on the cumulative converted power and current converted power of each phase sequence, the current three-phase imbalance rate of the power grid during the current working period is determined; Based on the preset second weighting parameter, the current three-phase imbalance rate, the cumulative conversion power of each phase sequence and the current conversion power, the load status of each phase sequence in the next working period is predicted, and the load status of each phase sequence in the next working period is obtained.

8. An inverter, characterized in that, The inverter includes: Inverter circuit, comprising multiple parallel bridge arms; The commutation relay group is connected to each arm of the inverter circuit and each phase sequence of the power grid, respectively. The commutation control unit, connected to the commutation relay group, is used to acquire the aging data of each bridge arm in the three-phase bridge arm during the current working period and the load status of each phase sequence in the power grid during the next working period; based on the aging data of each bridge arm in the three-phase bridge arm corresponding to the current working period and the load status of each phase sequence in the next working period, it establishes a matching relationship between each bridge arm and each phase sequence in the next working period; based on the matching relationship, it controls the commutation relay group to connect each bridge arm to the corresponding phase sequence.

9. The inverter according to claim 8, characterized in that, The commutation relay group includes multiple commutation relays; Each commutation relay includes multiple relay switches, and each arm of the inverter circuit is connected to the corresponding phase sequence of the power grid through the multiple relay switches in the commutation relay.

10. An inverter, characterized in that, The inverter includes: The acquisition module is used to acquire the aging data of each arm in the three-phase bridge arm during the current working period and the load status of each phase sequence in the power grid during the next working period. A module is established to establish a matching relationship between each bridge arm and each phase sequence in the next working period based on the aging data of each bridge arm in the three-phase bridge arm corresponding to the current working period and the load status of each phase sequence in the next working period. The control module is used to control the commutation relay group to connect each bridge arm to the corresponding phase sequence based on the matching relationship.

11. A power generation system, characterized in that, The power generation system includes: A photovoltaic array, connected to an inverter, is used to convert solar energy into direct current. The inverter includes an inverter circuit, a commutation relay group, and a commutation control unit. The inverter circuit converts the direct current (DC) to alternating current (AC). The commutation control unit acquires the aging data of each arm in the three-phase bridge arm during the current operating period and the load status of each phase sequence in the power grid during the next operating period. Based on the aging data of each arm in the three-phase bridge arm corresponding to the current operating period and the load status of each phase sequence in the next period, it establishes a matching relationship between each arm and each phase sequence in the next operating period. Based on the matching relationship, it controls the commutation relay group to connect each arm to the corresponding phase sequence. The power grid is connected to the inverter to receive the alternating current.

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