Control method and device of three-phase energy storage inverter and three-phase energy storage inverter

Abstract

This application provides a control method, apparatus, and three-phase energy storage inverter for a three-phase energy storage inverter. First, the current operating state of the energy storage system can be determined. Then, when the energy storage system is in a power-feeding state, based on the three-phase grid-connected total power limit, the three-phase inverter total power limit, and the standard bus voltage as reference values, closed-loop control is performed on the inverter power of each phase of the three-phase energy storage inverter using proportional-integral control, so as to feed power to the grid at a relatively consistent power through the point of common coupling. Conversely, when the energy storage system is in a power-receiving state, based on the three-phase average of the current three-phase total power consumption and the power consumption limit of each phase as reference values, closed-loop control is performed on the inverter power of each phase of the three-phase energy storage inverter using proportional-integral control, so as to draw power from the grid at a relatively consistent power through the point of common coupling to supply power to the load. This achieves three-phase power balance at the point of common coupling of the energy storage system.

Description

Technical Field

[0001] This application relates to the field of power electronics, and more specifically, to a control method, apparatus, and three-phase energy storage inverter. Background Technology

[0002] In power systems, due to various reasons (such as uneven load, line impedance differences, etc.), it is often difficult for the three-phase power to achieve complete balance. Among them, the load difference between different phases is one of the main reasons for the imbalance of three-phase power.

[0003] After installing an energy storage system, the power output of the photovoltaic modules, during grid connection via a three-phase energy storage inverter, may exacerbate the three-phase power imbalance at the point of common coupling (PCC) of the energy storage system. This can cause overheating or even damage to equipment such as switchboards and transformers. Therefore, ensuring the three-phase power balance at the PCC of the energy storage system is crucial for ensuring the normal operation of the power system. Summary of the Invention

[0004] This application provides a control method, device, and three-phase energy storage inverter for a three-phase energy storage inverter. The various aspects involved in this application will be described below.

[0005] Firstly, a control method for a three-phase energy storage inverter is provided, applied to a three-phase energy storage inverter in an energy storage system. The operating states of the energy storage system include a power supply state and a power extraction state. The power supply state is a state in which power is supplied to the load through the three-phase energy storage inverter while simultaneously feeding power to the grid. The power extraction state is a state in which power is extracted from the grid to simultaneously supply power to the load through the three-phase energy storage inverter and the grid. The method includes: determining the current operating state of the energy storage system; when the current operating state is the power supply state, determining the control method based on the three-phase grid-connected total power limit of the energy storage system, the three-phase inverter total power limit of the three-phase energy storage inverter, and a standard... Using the quasi-bus voltage as a reference value, proportional-integral control is performed based on feedback of the current grid-connected power of each phase, the current inverter power of each phase of the three-phase energy storage inverter, and the current bus voltage of the three-phase energy storage inverter to control the inverter power of each phase of the three-phase energy storage inverter. When the current operating state is the power extraction state, proportional-integral control is performed based on the three-phase average value of the current total power extraction of the three-phase energy storage system and the power extraction limit of each phase as reference values, and feedback of the current power extraction of each phase and the current inverter power of each phase of the three-phase energy storage inverter to control the inverter power of each phase of the three-phase energy storage inverter.

[0006] In one possible implementation, when the current operating state is the power-fed state, proportional-integral control is performed based on the feedback of the three-phase grid-connected total power limit of the energy storage system, the three-phase inverter total power limit of the three-phase energy storage inverter, and the standard bus voltage, using the current grid-connected power of each phase, the current inverter power of each phase of the three-phase energy storage inverter, and the current bus voltage of the three-phase energy storage inverter as reference values, to control the inverter power of each phase of the three-phase energy storage inverter. This includes: when the current operating state is the power-fed state, acquiring the three-phase grid-connected total power limit, the three-phase inverter total power limit, and the standard bus voltage respectively; and based on the feedback of the three-phase grid-connected total power limit, the three-phase inverter total power limit, and the standard bus voltage, performing proportional-integral control on each phase of the three-phase energy storage inverter. Using the total power limit and standard bus voltage as reference values, proportional-integral control is performed based on the feedback of the sum of the current grid-connected power of each phase, the sum of the current inverter power of each phase of the three-phase energy storage inverter, and the current bus voltage of the three-phase energy storage inverter to obtain the grid-connected power reference value for each phase. Based on the grid-connected power reference value for each phase, and based on the feedback of the current grid-connected power of each phase, proportional-integral control is performed on each phase to obtain the inverter power reference value for each phase. Based on the inverter power reference value for each phase, and based on the feedback of the current inverter power of each phase of the three-phase energy storage inverter, proportional-integral control is performed on each phase to control the inverter power of each phase of the three-phase energy storage inverter.

[0007] In one possible implementation, the grid-connected power reference value for each phase is obtained by using the three-phase grid-connected total power limit, the three-phase inverter total power limit, and the standard bus voltage as reference values, and by performing proportional-integral control based on feedback of the current sum of grid-connected power of each phase, the current sum of inverter power of each phase of the three-phase energy storage inverter, and the current bus voltage of the three-phase energy storage inverter. This includes: using the three-phase grid-connected total power limit as a reference value, performing proportional-integral control based on feedback of the current sum of grid-connected power of each phase to obtain a first grid-connected total power reference value. Using the total power limit of the three-phase inverter as a reference value, proportional-integral control is performed based on the feedback of the sum of the current inverter power of each phase of the three-phase energy storage inverter to obtain the second grid-connected total power reference value; using the standard bus voltage as a reference value, proportional-integral control is performed based on the feedback of the current bus voltage of the three-phase energy storage inverter to obtain the third grid-connected total power reference value; the three-phase average of the minimum value among the first, second, and third grid-connected total power reference values ​​is used as the grid-connected power reference value for each phase.

[0008] In one possible implementation, when the current operating state is a power-feeding state, the total power limit of the three-phase inverter is obtained, including: obtaining the rated power of the three-phase energy storage inverter and the current inverter temperature; and determining the total power limit of the three-phase inverter based on the rated power and the current inverter temperature.

[0009] In one possible implementation, when the current operating state is the power-feeding state, proportional-integral control is performed based on the three-phase average of the current total three-phase power supply and the power supply limit of each phase, using these as reference values. This control is based on feedback of the current power supply of each phase and the current inverter power of each phase of the three-phase energy storage inverter. The process includes: when the current operating state is the power-feeding state, obtaining the current total three-phase power supply and the power supply limit of each phase; using the three-phase average of the current total three-phase power supply as the reference value, and based on feedback of the current power supply of each phase, performing proportional-integral control on each phase to obtain a reference value for the inverter power of each phase; and using the reference values ​​of the inverter power of each phase and the power supply limit of each phase as reference values, and based on feedback of the current inverter power of each phase of the three-phase energy storage inverter, performing proportional-integral control on each phase to control the inverter power of each phase of the three-phase energy storage inverter.

[0010] In one possible implementation, when the current operating state is the power extraction state, the power extraction limit of each phase is obtained, including: obtaining the mains power extraction limit of the energy storage system and the current inverter temperature of the three-phase energy storage inverter; and determining the power extraction limit of each phase based on the mains power extraction limit and the current inverter temperature.

[0011] In one possible implementation, the power draw limit for each phase is determined based on the mains power draw limit and the current inverter temperature, including: determining the total power draw limit based on the mains power draw limit and the current inverter temperature; and using the three-phase average of the total power draw limit as the power draw limit for each phase.

[0012] Secondly, a control device for a three-phase energy storage inverter is provided, applied to a three-phase energy storage inverter in an energy storage system. The energy storage system operates in two states: a power supply state and a power extraction state. The power supply state is characterized by simultaneously supplying power to the load and connecting to the grid through the three-phase energy storage inverter. The power extraction state is characterized by drawing power from the grid to simultaneously supply power to the load through both the three-phase energy storage inverter and the grid. The device includes: a determining module for determining the current operating state of the energy storage system; and a control module for, when the current operating state is the power supply state, controlling the inverter based on the three-phase grid-connected total power limit of the energy storage system and the three-phase inverter's power output. Using the total power limit and standard bus voltage as reference values, proportional-integral control is performed based on feedback of the current grid-connected power of each phase, the current inverter power of each phase of the three-phase energy storage inverter, and the current bus voltage of the three-phase energy storage inverter to control the inverter power of each phase of the three-phase energy storage inverter. When the current operating state is the power extraction state, proportional-integral control is performed based on the three-phase average value of the current total power extraction of the energy storage system and the power extraction limit of each phase as reference values, and feedback of the current power extraction of each phase and the current inverter power of each phase of the three-phase energy storage inverter to control the inverter power of each phase of the three-phase energy storage inverter.

[0013] In one possible implementation, the control module, specifically when the current operating state is the power feeding state, acquires the three-phase grid-connected total power limit, the three-phase inverter total power limit, and the standard bus voltage respectively; using the three-phase grid-connected total power limit, the three-phase inverter total power limit, and the standard bus voltage as reference values, performs proportional-integral control based on feedback of the current sum of the grid-connected power of each phase, the current sum of the inverter power of each phase of the three-phase energy storage inverter, and the current bus voltage of the three-phase energy storage inverter to obtain the grid-connected power reference value of each phase; based on the grid-connected power reference value of each phase and the feedback of the current grid-connected power of each phase, performs proportional-integral control on each phase respectively to obtain the inverter power reference value of each phase; based on the inverter power reference value of each phase and the feedback of the current inverter power of each phase of the three-phase energy storage inverter, performs proportional-integral control on each phase respectively to control the inverter power of each phase of the three-phase energy storage inverter.

[0014] In one possible implementation, the control module is specifically used to perform proportional-integral control based on the feedback of the sum of the current grid-connected power of each phase, using the three-phase grid-connected total power limit as a reference value, to obtain a first grid-connected total power reference value; to perform proportional-integral control based on the feedback of the sum of the current inverter power of each phase of the three-phase energy storage inverter, using the three-phase inverter total power limit as a reference value, to obtain a second grid-connected total power reference value; to perform proportional-integral control based on the feedback of the current bus voltage of the three-phase energy storage inverter, using the standard bus voltage as a reference value, to obtain a third grid-connected total power reference value; and to take the three-phase average of the minimum value among the first, second, and third grid-connected total power reference values ​​as the grid-connected power reference value for each phase.

[0015] In one possible implementation, the control module is specifically used to acquire the rated power and current inverter temperature of the three-phase energy storage inverter; and to determine the total power limit of the three-phase inverter based on the rated power and current inverter temperature.

[0016] In one possible implementation, the control module is specifically used to, when the current operating state is power-taking state, acquire the current total three-phase power consumption and the power consumption limit of each phase; based on the three-phase average value of the current total three-phase power consumption as a reference value, and based on the feedback of the current power consumption of each phase, perform proportional-integral control on each phase to obtain the inverter power reference value of each phase; based on the inverter power reference value and the power consumption limit of each phase as reference values, and based on the feedback of the current inverter power of each phase of the three-phase energy storage inverter, perform proportional-integral control on each phase to control the inverter power of each phase of the three-phase energy storage inverter.

[0017] In one possible implementation, the control module is specifically used to acquire the mains power limit of the energy storage system and the current inverter temperature of the three-phase energy storage inverter; and to determine the power limit of each phase based on the mains power limit and the current inverter temperature.

[0018] In one possible implementation, the control module is specifically used to determine the total power draw limit based on the mains power draw limit and the current inverter temperature; and to use the three-phase average of the total power draw limit as the power draw limit for each phase.

[0019] Thirdly, a three-phase energy storage inverter is provided, comprising: a controller for performing the method described in the first aspect or any possible implementation thereof.

[0020] Fourthly, a computer-readable storage medium is provided having a computer program stored thereon, the computer program including program instructions that, when executed by a controller of a three-phase energy storage inverter, perform the method described in the first aspect or any possible implementation thereof.

[0021] In this embodiment, the current operating state of the energy storage system is first determined. Therefore, when the energy storage system is in a power-feeding state, based on the three-phase grid-connected total power limit, the three-phase inverter total power limit, and the standard bus voltage as reference values, closed-loop control is performed on the inverter power of each phase of the three-phase energy storage inverter using proportional-integral control. This ensures that after the power output from each phase of the three-phase energy storage inverter is output to the load, it is fed back to the grid through the point of common coupling (PCC) at a relatively consistent power, achieving three-phase power balance at the PCC. Conversely, when the energy storage system is in a power-receiving state, based on the three-phase average of the current three-phase power-receiving total power and the power-receiving limit of each phase as reference values, closed-loop control is performed on the inverter power of each phase of the three-phase energy storage inverter using proportional-integral control. This ensures that after the power output from each phase of the three-phase energy storage inverter is output to the load, the energy storage system draws power from the grid through the PCC at a relatively consistent power to supply power to the load, achieving three-phase power balance at the PCC. Attached Figure Description

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

[0023] Figure 1 This is a schematic diagram of the energy storage system provided in the embodiments of this application.

[0024] Figure 2 This is a flowchart illustrating the control method for a three-phase energy storage inverter provided in an embodiment of this application.

[0025] Figure 3 This is a schematic diagram of proportional-integral control for controlling a three-phase energy storage inverter under power-feeding conditions, provided in an embodiment of this application.

[0026] Figure 4 This is a schematic diagram of proportional-integral control for controlling a three-phase energy storage inverter under power-supply conditions, provided in an embodiment of this application.

[0027] Figure 5 This is a schematic diagram of the control device for the three-phase energy storage inverter provided in the embodiments of this application. Detailed Implementation

[0028] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art based on the embodiments of this application are within the scope of protection of this application.

[0029] In power systems, due to various reasons (such as uneven load, line impedance differences, etc.), it is often difficult for the three-phase power to achieve complete balance. Among them, the load difference between different phases is one of the main reasons for the imbalance of three-phase power.

[0030] After installing an energy storage system, the power output of the photovoltaic modules, during grid connection via a three-phase energy storage inverter, may exacerbate the three-phase power imbalance at the point of common coupling (PCC) of the energy storage system. This can cause overheating or even damage to equipment such as switchboards and transformers. Therefore, ensuring the three-phase power balance at the PCC of the energy storage system is crucial for ensuring the normal operation of the power system.

[0031] Therefore, this application provides a control method for a three-phase energy storage inverter. The method first determines the current operating state of the energy storage system. Then, when the energy storage system is in a power-feeding state, the method uses the three-phase grid-connected total power limit, the three-phase inverter total power limit, and the standard bus voltage as reference values. Based on proportional-integral control, the method performs closed-loop control on the inverter power of each phase of the three-phase energy storage inverter. This ensures that after the power output of each phase of the three-phase energy storage inverter is output to the load, it is fed back to the grid through the point of common coupling with relatively consistent power, thereby achieving three-phase power balance at the point of common coupling of the energy storage system. Furthermore, when the energy storage system is in power-drawing mode, based on the three-phase average of the current three-phase total power draw and the power draw limit of each phase as reference values, the inverter power of each phase of the three-phase energy storage inverter is controlled in a closed loop using proportional-integral control. This ensures that after the power output of each phase of the three-phase energy storage inverter is output to the load, the energy storage system draws power from the grid at a relatively consistent power through the point of common coupling to supply power to the load, thereby achieving three-phase power balance at the point of common coupling of the energy storage system.

[0032] In this embodiment, the control method for a three-phase energy storage inverter can be applied to a three-phase energy storage inverter in an energy storage system. The energy storage system may include a three-phase energy storage inverter, and energy storage components (such as battery packs) or power generation components (such as photovoltaic modules, wind power modules, etc.) directly or indirectly connected to the DC side of the three-phase energy storage inverter. The AC side of the three-phase energy storage inverter can be connected to a load to supply power, and can also be connected to the grid through a point of common coupling for grid-connected power supply. The operating states of the energy storage system may include a power supply state and a power extraction state. The power supply state is the state where power is supplied to the load through the three-phase energy storage inverter while simultaneously feeding power to the grid; the power extraction state is the state where power is extracted from the grid to simultaneously supply power to the load through both the three-phase energy storage inverter and the grid.

[0033] For example, energy storage systems such as Figure 1 As shown, the system can include a three-phase energy storage inverter. The DC side of the inverter is connected to the photovoltaic modules via a boost converter and to the battery pack via a DC / DC converter. The AC side of the inverter can be connected to the AC-coupled photovoltaic unit, the load, and the point of common coupling (PCC) via a distribution panel. An electricity meter can be installed at the PCC, and the system is connected to the grid via a transformer. In the power-feeding state, the power output from the photovoltaic modules and / or battery pack can be converted by the three-phase energy storage inverter and then output to the load and the grid via the distribution panel. The power output to the grid is the grid-connected power, and each phase has a corresponding grid-connected power. In the power-taking state, the system can draw power from the grid and output it to the load via the distribution panel, thus simultaneously supplying power to the load through both the power output from the three-phase energy storage inverter and the power drawn from the grid. The power drawn from the grid is the power taken from the grid, and each phase has a corresponding power taken from the grid.

[0034] It should be noted that in practical applications, based on relevant technologies, energy storage systems may also include other necessary or required structures besides those listed above, and no restrictions are imposed here.

[0035] For example, in the energy storage system of this application embodiment, the controller of the three-phase energy storage inverter can be connected to the electricity meter at the point of common coupling to obtain the grid-connected power supply or power extraction power of each phase, thereby facilitating the execution of the method provided in this application embodiment through the controller of the three-phase energy storage inverter. In some possible implementations, the method provided in this application embodiment can be executed through an Energy Management System (EMS) that operates in the controller of the three-phase energy storage inverter.

[0036] The following will refer to the accompanying drawings, Figure 1Taking the energy storage system shown as an example, a control method for a three-phase energy storage inverter provided in this application embodiment will be described in detail.

[0037] like Figure 2 As shown in the embodiments of this application, a control method for a three-phase energy storage inverter may include the following steps S201-S203.

[0038] S201. Determine the current operating status of the energy storage system.

[0039] For example, the current operating state of an energy storage system can be determined by the power direction at its point of common coupling (PCC). For instance, if the power direction at PCC is flowing towards the energy storage system, the current operating state is determined to be a power-feeding state. If the power direction at PCC is flowing towards the grid, the current operating state is determined to be a power-feeding state. The power direction at PCC can be determined based on the phase difference between the current and voltage measured by the installed electricity meter. Specific determination methods can be found in relevant technical implementations and will not be elaborated here.

[0040] S202. When the current operating state is the power feeding state, the proportional-integral control is performed based on the feedback of the current grid-connected power of the energy storage system, the current inverter power of the three-phase energy storage inverter, and the standard bus voltage, using the three-phase grid-connected power of each phase, the current inverter power of each phase of the three-phase energy storage inverter, and the current bus voltage of the three-phase energy storage inverter as reference values, in order to control the inverter power of each phase of the three-phase energy storage inverter.

[0041] For example, when the current operating state is the power supply state, the three-phase grid-connected total power limit, the three-phase inverter total power limit, and the standard bus voltage can be obtained separately.

[0042] The three-phase grid-connected total power limit is the limit for the total three-phase power fed from the energy storage system to the grid, which can be pre-configured as needed. The standard bus voltage of the three-phase energy storage inverter is the standard voltage of its DC bus, which can also be pre-configured as needed.

[0043] The three-phase total inverter power limit of a three-phase energy storage inverter is the limit of its total three-phase output power on the AC side. For example, the rated power and current inverter temperature of the three-phase energy storage inverter can be obtained, and the three-phase total inverter power limit can be determined based on these two parameters. Alternatively, the operating frequency of the three-phase energy storage inverter can be determined based on the relationship between the inverter temperature and the operating frequency, and then the three-phase total inverter power limit can be calculated based on the operating frequency and rated power. Of course, other possible implementation methods can also be used to determine the three-phase total inverter power limit based on related technologies; no limitations are imposed here.

[0044] After obtaining the total grid-connected power limit, the total inverter power limit, and the standard bus voltage, for example, the following steps can be taken: First, using these three-phase total grid-connected power limits, the total inverter power limit, and the standard bus voltage as reference values, proportional-integral (PI) control can be performed based on feedback from the sum of the current grid-connected power of each phase, the sum of the current inverter power of each phase of the three-phase energy storage inverter, and the current bus voltage of the three-phase energy storage inverter, to obtain the grid-connected power reference value for each phase. Then, based on the grid-connected power reference values ​​for each phase and the feedback from the current grid-connected power of each phase, PI control can be performed on each phase separately to obtain the inverter power reference value for each phase. Finally, based on the inverter power reference values ​​for each phase and the feedback from the current inverter power of each phase of the three-phase energy storage inverter, PI control can be performed on each phase separately to control the inverter power of each phase of the three-phase energy storage inverter.

[0045] In some possible implementations, the reference value for the grid-connected power of each phase is obtained by performing proportional-integral control based on feedback from the sum of the current grid-connected power of each phase, the sum of the current inverter power of each phase of the three-phase energy storage inverter, and the current bus voltage of the three-phase energy storage inverter, using the three-phase total grid-connected power limit, the three-phase inverter total power limit, and the standard bus voltage as reference values. This can be achieved by using the three-phase total grid-connected power limit as a reference value and performing proportional-integral control based on feedback from the sum of the current grid-connected power of each phase to obtain a first reference value for the total grid-connected power. Alternatively, a second reference value for the total grid-connected power can be obtained by using the three-phase inverter total power limit as a reference value and performing proportional-integral control based on feedback from the sum of the current inverter power of each phase of the three-phase energy storage inverter. Using the standard bus voltage as a reference value, proportional-integral control is performed based on the feedback of the current bus voltage of the three-phase energy storage inverter to obtain the third grid-connected total power reference value; the three-phase average of the minimum value among the first, second, and third grid-connected total power reference values ​​(i.e., 1 / 3 of the minimum value among all grid-connected total power reference values) is used as the grid-connected power reference value for each phase.

[0046] For example, based on the aforementioned implementation method, taking three phases U, V, and W as an example, such as Figure 3As shown, proportional-integral (PI) control can be performed based on the feedback of the current sum of the grid-connected power of each phase (GridPwrSum), using the three-phase grid-connected total power limit (TotalExportPwrCtlRef) as a reference value. Similarly, proportional-integral (PI) control can be performed based on the feedback of the current sum of the inverter power of each phase (InvPwrSum) of the three-phase energy storage inverter, using the standard bus voltage (InvStandBusRef) as a reference value, and the current bus voltage (BusVolt) of the three-phase energy storage inverter. Therefore, the three-phase average of the minimum (min) values ​​of each PI control output is used as the grid-connected power reference value for each phase, i.e., the equal U-phase grid-connected power reference values ​​(ExportPwrRefU), V-phase grid-connected power reference values ​​(ExportPwrRefV), and W-phase grid-connected power reference values ​​(ExportPwrRefW).

[0047] Subsequently, for phase U, proportional-integral (PI) control is performed based on the feedback of the current phase U grid-connected power (GridPwrU) and the reference value of phase U grid-connected power, to obtain the phase U inverter power reference value (InvPowrRefU); for phase V, proportional-integral (PI) control is performed based on the feedback of the current phase V grid-connected power (GridPwrV) and the reference value of phase V inverter power (InvPowrRefV); for phase W, proportional-integral (PI) control is performed based on the feedback of the current phase W grid-connected power (GridPwrW) and the reference value of phase W inverter power (InvPowrRefW).

[0048] Finally, for phase U, proportional-integral (PI) control is performed based on the feedback of the current phase U inverter power (InvtPwrU) according to the phase U inverter power reference value, to obtain the phase U inverter power output value (InvtPwrOutU), so as to control the phase U inverter power of the three-phase energy storage inverter according to this phase U inverter power output value. For phase V, proportional-integral (PI) control is performed based on the feedback of the current phase V inverter power (InvtPwrV) according to the phase V inverter power reference value, to obtain the phase V inverter power output value (InvtPwrOutV), so as to control the phase V inverter power of the three-phase energy storage inverter according to this phase V inverter power output value. For phase W, proportional-integral (PI) control is performed based on the feedback of the current phase W inverter power (InvtPwrW) according to the phase W inverter power reference value, to obtain the phase W inverter power output value (InvtPwrOutW), so as to control the phase W inverter power of the three-phase energy storage inverter according to this phase W inverter power output value.

[0049] S203. When the current working state is the power-taking state, the three-phase average value of the current three-phase total power taking of the energy storage system and the power taking limit of each phase are used as reference values. Based on the feedback of the current power taking of each phase and the current inverter power of each phase of the three-phase energy storage inverter, proportional-integral control is performed to control the inverter power of each phase of the three-phase energy storage inverter.

[0050] For example, when the current working state is power-taking state, the current total power of the three phases and the power limit of each phase can be obtained separately.

[0051] The current total three-phase power draw is the total three-phase power that the energy storage system is currently drawing from the grid, which can be obtained through the electricity meter installed at the point of common coupling.

[0052] For example, the current inverter temperature of the three-phase energy storage inverter and the pre-configured mains power drawdown limit of the energy storage system can be obtained. The power drawdown limit for each phase can then be determined based on the mains power drawdown limit and the current inverter temperature. For instance, the operating frequency of the three-phase energy storage inverter can be determined first based on the relationship between the inverter temperature and the operating frequency of the three-phase inverter, and then the power drawdown limit for each phase can be calculated based on the operating frequency and the mains power drawdown limit. In some possible implementations, the total power drawdown limit can be calculated first based on the operating frequency and the mains power drawdown limit, and then the three-phase average of the total power drawdown limit (i.e., 1 / 3 of the total power drawdown limit) can be used as the power drawdown limit for each phase, resulting in equal power drawdown limits for each phase. Of course, based on related technologies, other possible implementations can also be used to determine the power drawdown limit for each phase, and this is not limited here.

[0053] After obtaining the current total three-phase power output and the power output limit of each phase, for example, the average value of the current total three-phase power output (i.e., 1 / 3 of the current total three-phase power output) can be used as a reference value. Based on the feedback of the current power output of each phase, proportional-integral control can be performed on each phase to obtain the inverter power reference value for each phase. Then, based on the inverter power reference value and the power output limit of each phase as reference values, proportional-integral control can be performed on each phase based on the feedback of the current inverter power of each phase of the three-phase energy storage inverter to control the inverter power of each phase of the three-phase energy storage inverter.

[0054] For example, based on the aforementioned implementation method, taking three phases U, V, and W as an example, such as Figure 4As shown, one-third of the current total three-phase power input (GridPwrSum) can be used as the corresponding reference value for each phase. For phase U, proportional-integral (PI) control is performed based on the feedback of the current phase U power input (GridPwrU) to obtain the phase U inverter power reference value (ImportPwrOutU); for phase V, proportional-integral (PI) control is performed based on the feedback of the current phase V power input (GridPwrV) to obtain the phase V inverter power reference value (ImportPwrOutV); and for phase W, proportional-integral (PI) control is performed based on the feedback of the current phase W power input (GridPwrW) to obtain the phase W inverter power reference value (ImportPwrOutW).

[0055] Subsequently, for phase U, proportional-integral (PI) control is performed based on the feedback of the current phase U inverter power (InvtpwrU), using the phase U inverter power reference value and the phase U power draw limit (InvPowrRefU) as reference values, to obtain the phase U inverter power output value (InvtPwrOutU). This output value is then used to control the phase U inverter power of the three-phase energy storage inverter. For phase V, proportional-integral (PI) control is performed based on the feedback of the current phase V inverter power (InvtpwrV), using the phase V inverter power reference value and the phase V power draw limit (InvPowrRefV) as reference values, to obtain the phase V inverter power output value (InvtPwrOutV). This output value is then used to control the phase V inverter power of the three-phase energy storage inverter. For phase W, the inverter power reference value and the power draw limit value (InvPowrRefW) of phase W are used as reference values. Based on the feedback of the current inverter power (InvtpwrW) of phase W, proportional-integral (PI) control is performed to obtain the inverter power output value (InvtPwrOutW) of phase W, so as to control the inverter power of phase W of the three-phase energy storage inverter according to the inverter power output value of phase W.

[0056] In this embodiment, based on the aforementioned control method for a three-phase energy storage inverter, closed-loop control based on proportional-integral control can be used to control the inverter power of each phase of the three-phase energy storage inverter. In the power-feeding state, the power output of each phase of the three-phase energy storage inverter is distributed to the load and then fed to the grid with a relatively consistent power, achieving three-phase power balance at the point of common coupling. Similarly, in the power-taking state, after the power output of each phase of the three-phase energy storage inverter is distributed to the load, the energy storage system draws power from the grid with a relatively consistent power to supplement the load, achieving three-phase power balance at the point of common coupling. This avoids overheating or damage to components such as the switchboard and transformer due to three-phase power imbalance.

[0057] The method embodiments of this application have been described in detail above with reference to the accompanying drawings. The apparatus embodiments of this application will now be described in detail. It should be understood that the descriptions of the apparatus embodiments correspond to the descriptions of the method embodiments; therefore, any parts not described in detail can be referred to the foregoing method embodiments.

[0058] This application also provides a control device for a three-phase energy storage inverter. (Refer to...) Figure 5 As shown, the device includes: a determining module 501, used to determine the current operating state of the energy storage system; and a control module 502, used to perform proportional-integral control, based on feedback of the current grid-connected power of each phase, the current inverter power of each phase of the three-phase energy storage inverter, and the current bus voltage of the three-phase energy storage inverter, when the current operating state is a power supply state, to control the inverter power of each phase of the three-phase energy storage inverter; and to perform proportional-integral control, based on feedback of the current grid-connected power of each phase, the current inverter power of each phase of the three-phase energy storage inverter, and the current bus voltage of the three-phase energy storage inverter, when the current operating state is a power extraction state, using the three-phase average value of the current three-phase power extraction of the energy storage system and the power extraction limit of each phase as reference values, to control the inverter power of each phase of the three-phase energy storage inverter, based on feedback of the current power extraction power of each phase and the current inverter power of each phase of the three-phase energy storage inverter.

[0059] In one possible implementation, the control module 502 is specifically used to, when the current operating state is the power feeding state, acquire the three-phase grid-connected total power limit, the three-phase inverter total power limit, and the standard bus voltage respectively; based on the three-phase grid-connected total power limit, the three-phase inverter total power limit, and the standard bus voltage as reference values, perform proportional-integral control based on the feedback of the current sum of the grid-connected power of each phase, the current sum of the inverter power of each phase of the three-phase energy storage inverter, and the current bus voltage of the three-phase energy storage inverter to obtain the grid-connected power reference value of each phase; based on the grid-connected power reference value of each phase, and based on the feedback of the current grid-connected power of each phase, perform proportional-integral control on each phase respectively to obtain the inverter power reference value of each phase; based on the inverter power reference value of each phase, and based on the feedback of the current inverter power of each phase of the three-phase energy storage inverter, perform proportional-integral control on each phase respectively to control the inverter power of each phase of the three-phase energy storage inverter.

[0060] In one possible implementation, the control module 502 is specifically used to perform proportional-integral control based on the feedback of the sum of the current grid-connected power of each phase, using the three-phase grid-connected total power limit as a reference value, to obtain a first grid-connected total power reference value; to perform proportional-integral control based on the feedback of the sum of the current inverter power of each phase of the three-phase energy storage inverter, using the three-phase inverter total power limit as a reference value, to obtain a second grid-connected total power reference value; to perform proportional-integral control based on the feedback of the current bus voltage of the three-phase energy storage inverter, using the standard bus voltage as a reference value, to obtain a third grid-connected total power reference value; and to take the three-phase average of the minimum value among the first, second, and third grid-connected total power reference values ​​as the grid-connected power reference value for each phase.

[0061] In one possible implementation, the control module 502 is specifically used to obtain the rated power and current inverter temperature of the three-phase energy storage inverter; and to determine the total power limit of the three-phase inverter based on the rated power and current inverter temperature.

[0062] In one possible implementation, the control module 502 is specifically used to, when the current operating state is power-taking state, acquire the current total three-phase power consumption and the power consumption limit of each phase respectively; based on the three-phase average value of the current total three-phase power consumption as a reference value, and based on the feedback of the current power consumption of each phase, perform proportional-integral control on each phase respectively to obtain the inverter power reference value of each phase; based on the inverter power reference value of each phase and the power consumption limit of each phase as reference values, and based on the feedback of the current inverter power of each phase of the three-phase energy storage inverter, perform proportional-integral control on each phase respectively to control the inverter power of each phase of the three-phase energy storage inverter.

[0063] In one possible implementation, the control module 502 is specifically used to obtain the mains power limit of the energy storage system and the current inverter temperature of the three-phase energy storage inverter; and to determine the power limit of each phase based on the mains power limit and the current inverter temperature.

[0064] In one possible implementation, the control module 502 is specifically used to determine the total power extraction limit based on the mains power extraction limit and the current inverter temperature; and to use the three-phase average of the total power extraction limit as the power extraction limit for each phase.

[0065] This application also provides a three-phase energy storage inverter, including: a controller, which is used to execute the method described in any of the preceding embodiments.

[0066] This application also provides a computer-readable storage medium storing a computer program thereon. The computer program includes program instructions, which, when executed by the controller of a three-phase energy storage inverter, perform the methods described in any of the preceding embodiments.

[0067] It should be understood that, in the embodiments of this application, determining B based on A does not mean determining B solely based on A; B can also be determined based on A and / or other information.

[0068] It should be understood that in the embodiments of this application, "B corresponding to A" means that B is associated with A, and B can be determined based on A. However, it should also be understood that determining B based on A does not mean that B is determined solely based on A; B can also be determined based on A and / or other information.

[0069] It should be understood that the term "and / or" in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. Additionally, the character " / " in this article generally indicates that the preceding and following related objects have an "or" relationship.

[0070] It should be understood that in the various embodiments of this application, the order of the above-mentioned processes does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0071] In the several embodiments provided in this application, it should be understood that the disclosed systems, apparatuses, and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection between apparatuses or units may be electrical, mechanical, or other forms.

[0072] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0073] In addition, the functional units in the various embodiments of this application can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit.

[0074] In the above embodiments, implementation can be achieved, in whole or in part, through software, hardware, firmware, or any combination thereof. When implemented in software, it can be implemented, in whole or in part, as a computer program product. A computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, all or part of the flow or function according to the embodiments of this application is generated. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions can be stored in a computer-readable storage medium or transmitted from one computer-readable storage medium to another. For example, computer instructions can be transmitted from one website, computer, server, or data center to another website, computer, server, or data center via wired (e.g., coaxial cable, fiber optic, digital subscriber line (DSL)) or wireless (e.g., infrared, wireless, microwave, etc.) means. The computer-readable storage medium can be any available medium that a computer can read or a data storage device such as a server or data center that integrates one or more available media. The available media can be magnetic media (e.g., floppy disks, hard disks, magnetic tapes), optical media (e.g., digital video discs, DVDs) or semiconductor media (e.g., solid-state disks, SSDs), etc.

[0075] The above are merely specific embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A control method for a three-phase energy storage inverter, characterized in that, A three-phase energy storage inverter is applied in an energy storage system. The energy storage system operates in two states: a power supply state and a power extraction state. The power supply state is a state in which the three-phase energy storage inverter supplies power to the load while simultaneously feeding power to the grid. The power extraction state is a state in which power is extracted from the grid to simultaneously supply power to the load through both the three-phase energy storage inverter and the grid. The method includes: Determine the current operating status of the energy storage system; When the current operating state is the power supply state, proportional-integral control is performed based on the feedback of the current grid-connected power of each phase, the current inverter power of each phase of the three-phase energy storage inverter, and the current bus voltage of the three-phase energy storage inverter, using the three-phase grid-connected power limit of the energy storage system, the three-phase inverter power limit of the three-phase energy storage inverter, and the standard bus voltage of the three-phase energy storage inverter as reference values, in order to control the inverter power of each phase of the three-phase energy storage inverter. When the current operating state is the power extraction state, the three-phase average value of the current three-phase total power extraction of the energy storage system and the power extraction limit of each phase are used as reference values. Based on the feedback of the current power extraction of each phase and the current inverter power of each phase of the three-phase energy storage inverter, proportional-integral control is performed to control the inverter power of each phase of the three-phase energy storage inverter.

2. The method according to claim 1, characterized in that, When the current operating state is the power-feeding state, proportional-integral control is performed based on the feedback of the current grid-connected power of each phase, the current inverter power of each phase of the three-phase energy storage inverter, and the current bus voltage of the three-phase energy storage inverter, using the three-phase grid-connected total power limit of the energy storage system, the three-phase inverter total power limit of the three-phase energy storage inverter, and the standard bus voltage of the three-phase energy storage inverter as reference values, to control the inverter power of each phase of the three-phase energy storage inverter, including: When the current working state is the power supply state, the three-phase grid-connected total power limit, the three-phase inverter total power limit, and the standard bus voltage are obtained respectively. Based on the three-phase grid-connected total power limit, the three-phase inverter total power limit, and the standard bus voltage as reference values, proportional-integral control is performed based on the feedback of the current sum of grid-connected power of each phase, the current sum of inverter power of each phase of the three-phase energy storage inverter, and the current bus voltage of the three-phase energy storage inverter to obtain the grid-connected power reference value of each phase. Based on the grid-connected power reference values ​​of each phase, and based on the feedback of the current grid-connected power of each phase, proportional-integral control is performed on each phase to obtain the inverter power reference values ​​of each phase. Based on the inverter power reference value of each phase, and based on the feedback of the current inverter power of each phase of the three-phase energy storage inverter, proportional-integral control is performed on each phase to control the inverter power of each phase of the three-phase energy storage inverter.

3. The method according to claim 2, characterized in that, The method involves using the three-phase grid-connected total power limit, the three-phase inverter total power limit, and the standard bus voltage as reference values, and performing proportional-integral control based on feedback from the sum of the current grid-connected power of each phase, the sum of the current inverter power of each phase of the three-phase energy storage inverter, and the current bus voltage of the three-phase energy storage inverter to obtain the grid-connected power reference value for each phase, including: Using the three-phase grid-connected total power limit as a reference value, proportional-integral control is performed based on the feedback of the sum of the current grid-connected power of each phase to obtain the first grid-connected total power reference value; Using the total power limit of the three-phase inverter as a reference value, proportional-integral control is performed based on the feedback of the sum of the current inverter power of each phase of the three-phase energy storage inverter to obtain the second grid-connected total power reference value. Based on the standard bus voltage as a reference value, proportional-integral control is performed based on the feedback of the current bus voltage of the three-phase energy storage inverter to obtain the third grid-connected total power reference value. The average of the minimum values ​​among the first, second, and third total grid-connected power reference values ​​is taken as the grid-connected power reference value for each phase.

4. The method according to claim 2 or 3, characterized in that, When the current operating state is the power supply state, the three-phase inverter total power limit is obtained, including: Obtain the rated power and current inverter temperature of the three-phase energy storage inverter; The total power limit of the three-phase inverter is determined based on the rated power and the current inverter temperature.

5. The method according to claim 1, characterized in that, When the current operating state is the power extraction state, based on the three-phase average of the current total three-phase power extraction of the energy storage system and the power extraction limit of each phase as reference values, proportional-integral control is performed based on the feedback of the current power extraction of each phase and the current inverter power of each phase of the three-phase energy storage inverter to control the inverter power of each phase of the three-phase energy storage inverter, including: When the current working state is the power-taking state, the current total power of the three phases and the power-taking limit of each phase are obtained respectively; Using the three-phase average value of the current total three-phase power as a reference value, and based on the feedback of the current power of each phase, proportional-integral control is performed on each phase to obtain the inverter power reference value of each phase. Based on the inverter power reference value and the power draw limit of each phase as reference values, and based on the feedback of the current inverter power of each phase of the three-phase energy storage inverter, proportional-integral control is performed on each phase to control the inverter power of each phase of the three-phase energy storage inverter.

6. The method according to claim 5, characterized in that, When the current operating state is the power-taking state, the power-taking limit value of each phase is obtained, including: Obtain the maximum AC power drawdown limit of the energy storage system and the current inverter temperature of the three-phase energy storage inverter; The power draw limit for each phase is determined based on the mains power draw limit and the current inverter temperature.

7. The method according to claim 6, characterized in that, The step of determining the power extraction limit for each phase based on the mains power extraction limit and the current inverter temperature includes: The total power draw limit is determined based on the mains power draw limit and the current inverter temperature; The three-phase average of the total power extraction limit is used as the power extraction limit for each phase.

8. A control device for a three-phase energy storage inverter, characterized in that, A three-phase energy storage inverter is applied in an energy storage system. The energy storage system operates in two states: a power supply state and a power extraction state. The power supply state is characterized by simultaneously supplying power to the load and connecting to the grid through the three-phase energy storage inverter. The power extraction state is characterized by drawing power from the grid to simultaneously supply power to the load through both the three-phase energy storage inverter and the grid. The device includes: The determination module is used to determine the current operating status of the energy storage system; The control module is configured to, when the current operating state is the power supply state, perform proportional-integral control based on the feedback of the current grid-connected power limit of the energy storage system, the three-phase inverter power limit of the three-phase energy storage inverter, and the standard bus voltage, using the current grid-connected power of each phase, the current inverter power of each phase of the three-phase energy storage inverter, and the current bus voltage of the three-phase energy storage inverter as reference values, to control the inverter power of each phase of the three-phase energy storage inverter; and when the current operating state is the power extraction state, perform proportional-integral control based on the feedback of the current three-phase power extraction average of the current three-phase power extraction of the energy storage system and the power extraction limit of each phase, using the current power extraction power of each phase and the current inverter power of each phase of the three-phase energy storage inverter as reference values, to control the inverter power of each phase of the three-phase energy storage inverter.

9. A three-phase energy storage inverter, characterized in that, Includes a controller for performing the method as described in any one of claims 1 to 7.

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

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