Grid-connection switching method for energy storage inverter and related device thereof

Abstract

The present application relates to a grid-connection switching method for an energy storage inverter and a related device thereof. The method comprises: when an energy storage inverter is in an off-grid state and supplies power to a load in a voltage source mode, obtaining a grid connection signal; in response to the grid connection signal, controlling the phase angle of an alternating-current output voltage of the energy storage inverter to lead the phase angle of a power grid voltage, and controlling the amplitude of the alternating-current output voltage of the energy storage inverter to be higher than the amplitude of the power grid voltage; controlling a power grid to supply power to the load; and when the power grid supplies power to the load, controlling the energy storage inverter to stop supplying power to the load. The present application at least solves the problem of important loads experiencing power failure or power supply abnormalities during the power supply switching process, thereby improving the stability and reliability of power supply to important loads.

Description

Grid-connected switching method of energy storage inverter and related equipment Technical Field

[0001] The present application relates to the technical field of energy storage inverters, and in particular to a grid-connected switching method of an energy storage inverter and related equipment. Background Art

[0002] This section is intended to provide a background or context to the embodiments of the invention recited in the claims. No admission is made that what is described herein is prior art by its inclusion in this section.

[0003] When the grid loses power, the energy storage inverter will enter off-grid working mode to supply power to important loads. When the grid returns to normal, the power supply to important loads needs to be switched from the energy storage inverter back to normal grid power supply.

[0004] In related technologies, after the power grid returns to normal, the relays in the path from the energy storage inverter to the critical loads are first disconnected, and then the relays in the path from the grid to the critical loads are closed. With this switching method, no matter how fast the relays respond, it is impossible to ensure that the critical loads do not experience any power outages or maintain stable power supply during the power switching process, resulting in power outages or power supply anomalies to the critical loads, causing economic losses.

[0005] Summary of the Invention

[0006] The grid-connected switching method of the energy storage inverter and related equipment provided by the embodiments of the present invention at least solve the problem of power failure or power supply abnormality of important loads during the power supply switching process.

[0007] A grid-connected switching method for an energy storage inverter, comprising:

[0008] When the energy storage inverter is in an off-grid state and supplies power to the load in voltage source mode, a grid-connected signal is obtained;

[0009] In response to the grid connection signal, controlling the phase angle of the AC output voltage of the energy storage inverter to be ahead of the phase angle of the grid voltage, and controlling the amplitude of the AC output voltage of the energy storage inverter to be higher than the amplitude of the grid voltage;

[0010] controlling the power grid to supply power to the load; and

[0011] After the power grid supplies power to the load, the energy storage inverter is controlled to stop supplying power to the load.

[0012] In some embodiments, obtaining a grid-connected signal includes:

[0013] Obtaining a grid connection signal triggered by a user; or

[0014] The grid voltage of the grid is detected, and the grid connection signal is generated when the frequency and amplitude of the grid voltage within a set time period meet set conditions.

[0015] In some embodiments, in response to the grid-connected signal, controlling the phase angle of the AC output voltage of the energy storage inverter to lead the phase angle of the grid voltage, and controlling the amplitude of the AC output voltage of the energy storage inverter to be higher than the amplitude of the grid voltage includes:

[0016] Phase-locking the grid voltage to obtain a phase angle of the grid voltage and collecting an amplitude of the grid voltage;

[0017] Based on the phase angle of the grid voltage and the set phase angle increment, as well as the amplitude of the grid voltage and the set amplitude increment, obtaining a tracking phase angle and a tracking amplitude of the AC output voltage of the energy storage inverter;

[0018] Based on the tracking phase angle and the tracking amplitude, the AC output voltage of the energy storage inverter is modulated so that the phase angle of the AC output voltage of the energy storage inverter leads the phase angle of the grid voltage, and the amplitude of the AC output voltage of the energy storage inverter is higher than the amplitude of the grid voltage.

[0019] In some embodiments, the phase angle increment is determined based on the leading phase angle required to make the current value of the inductor connected in series with the AC end of the energy storage inverter less than the rated current of the energy storage inverter and approaching 0 under the current frequency and amplitude of the grid voltage, wherein:

[0020] The current value of the inductor connected in series at the AC end of the energy storage inverter

[0021] E is the amplitude of the grid voltage, is the phase angle increment, w is the frequency of the grid voltage, and L is the inductance of the inductor.

[0022] In some embodiments, the amplitude increment range includes: 1V to 5V.

[0023] In some embodiments, the phase angle increment has a value range of 0.5° to 3°.

[0024] In some embodiments, when the energy storage inverter is in an off-grid state and supplies power to the load, an inverter-side relay provided between the energy storage inverter and the load is energized, and a grid-side relay provided between the grid and the load is disconnected; and controlling the grid to supply power to the load includes:

[0025] The grid-side relay is controlled to be closed so that the grid supplies power to the load.

[0026] In some embodiments, after the power grid supplies power to the load, controlling the energy storage inverter to stop supplying power to the load includes:

[0027] After the grid-side relay is closed for a preset time, the inverter-side relay is controlled to be disconnected, so that the energy storage inverter stops supplying power to the load.

[0028] In some embodiments, the preset duration includes one to several grid voltage cycles of the grid.

[0029] In some embodiments, after controlling the energy storage inverter to stop supplying power to the load, the method further includes:

[0030] The energy storage inverter is controlled to operate in a current source mode.

[0031] In some embodiments, the energy storage inverter is a three-phase energy storage inverter, and the power grid is a three-phase power grid. In the steps of controlling the phase angle of the AC output voltage of the energy storage inverter to lead the phase angle of the power grid voltage, and controlling the amplitude of the AC output voltage of the energy storage inverter to be higher than the amplitude of the power grid voltage in response to the grid-connected signal, the phase angle of the AC output voltage of each phase of the energy storage inverter is controlled to lead the phase angle of the power grid voltage of that phase, and the amplitude of the AC output voltage of each phase of the energy storage inverter is controlled to be higher than the amplitude of the power grid voltage of that phase.

[0032] An energy storage inverter system includes: an energy storage inverter, an inverter-side relay, and a grid-side relay, wherein the inverter-side relay and the grid-side relay are connected in series between an AC terminal and a grid connection terminal of the energy storage inverter, and a connection node between the inverter-side relay and the grid-side relay is further connected to a load terminal, wherein the load terminal is used to connect a load; the energy storage inverter system is used to execute the above-mentioned grid-connected switching method for the energy storage inverter.

[0033] In some embodiments, the energy storage inverter is a three-phase energy storage inverter, and the inverter-side relay and the grid-side relay are respectively provided at the AC end of each phase of the energy storage inverter.

[0034] An electronic device includes: a processor and a memory storing a program, wherein the program includes instructions, and when the instructions are executed by the processor, the processor executes the above-mentioned grid-connected switching method of the energy storage inverter.

[0035] A non-transitory machine-readable medium storing computer instructions, wherein the computer instructions are used to enable the computer to execute the above-mentioned grid-connected switching method of the energy storage inverter.

[0036] The grid-connected switching method and related equipment of an energy storage inverter provided in an embodiment of the present invention obtain a grid-connected signal when the energy storage inverter is in an off-grid state and supplies power to a load in voltage source mode; in response to the grid-connected signal, control the phase angle of the AC output voltage of the energy storage inverter to lead the phase angle of the grid voltage, and control the amplitude of the AC output voltage of the energy storage inverter to be higher than the amplitude of the grid voltage; control the grid to supply power to the load; and control the energy storage inverter to stop supplying power to the load after the grid supplies power to the load. This method at least solves the problem of power failure or power supply anomaly to important loads during power supply switching, thereby improving the stability and reliability of power supply to important loads.

[0037] The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below so that other features, objects, and advantages of the invention are more readily apparent. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other embodiments can be derived from these drawings without inventive effort.

[0039] FIG1 is a schematic diagram of a power supply system according to this embodiment.

[0040] FIG2 is a flow chart of the grid-connected switching method of this embodiment.

[0041] FIG3 is a schematic structural diagram of the energy storage inverter system of this embodiment.

[0042] FIG4 is a schematic structural diagram of the electronic device of this embodiment. DETAILED DESCRIPTION

[0043] The following describes embodiments of the present invention in more detail with reference to the accompanying drawings. Although certain embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be construed as being limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the present invention. It should be understood that the accompanying drawings and embodiments of the present invention are for illustrative purposes only and are not intended to limit the scope of protection of the present invention.

[0044] In power systems, electrical loads (also known as power loads) are classified into various levels based on their importance, such as critical loads and general loads. Compared to general loads, power systems must ensure stable and reliable power supply to critical loads to avoid significant economic and other losses. Critical loads are powered by two or more independent power sources to ensure that if one power source fails, the other can be switched to maintain power to the critical loads.

[0045] Figure 1 is a schematic diagram of the power supply system of this embodiment. As shown in Figure 1, two independent power sources, an energy storage system including an energy storage inverter and a grid, are used to ensure power supply to critical loads. When the grid loses power, the inverter-side relay 1 is closed, and the energy storage inverter operates in AC voltage source mode to supply power to critical load 3. The grid-side relay 2 is disconnected, and power to general load 4 is cut off. When the grid returns to normal, critical load 3 must switch to the grid for power supply. Because the AC output voltage of the energy storage inverter is highly uncertain when operating in an isolated, off-grid state, and the grid voltage itself fluctuates to a certain extent, this can lead to uncontrollable inconsistencies between the AC output voltage of the energy storage inverter and the grid voltage. Due to this inconsistency, to prevent grid energy from flowing back into the energy storage inverter, related art typically disconnects the inverter-side relay 1 before closing the grid-side relay 2 for grid-connected switching. During this switching process, the power supply to critical load 3 can experience significant fluctuations or even temporary power outages.

[0046] In order to solve the above problems, this embodiment provides a grid-connected switching method for an energy storage inverter. FIG2 is a flow chart of the grid-connected switching method of this embodiment. As shown in FIG2 , the process includes the following steps:

[0047] Step S201 : When the energy storage inverter is in an off-grid state and supplies power to a load in a voltage source mode, a grid-connected signal is obtained.

[0048] Step S202 , in response to the grid connection signal, controlling the phase angle of the AC output voltage of the energy storage inverter to be ahead of the phase angle of the grid voltage, and controlling the amplitude of the AC output voltage of the energy storage inverter to be higher than the amplitude of the grid voltage.

[0049] Step S203: Control the power grid to supply power to the load.

[0050] Step S204: After the power grid supplies power to the load, the energy storage inverter is controlled to stop supplying power to the load.

[0051] In an off-grid state, loads other than critical loads (e.g., general loads) are typically disconnected to ensure the energy storage inverter can provide a stable and reliable power supply to the critical loads. The loads powered by the energy storage inverter in off-grid voltage source mode in step S201 include the critical loads described above, i.e., loads requiring uninterrupted power supply.

[0052] In step S202, after receiving the grid-connection signal, the phase angle and amplitude of the AC output voltage are controlled so that the phase angle of the AC output voltage leads the phase angle of the grid voltage and the amplitude of the AC output voltage is higher than the amplitude of the grid voltage. This prevents grid energy from flowing back into the energy storage inverter when the grid and the energy storage inverter jointly power the load. After the grid and the energy storage inverter jointly power the load, the energy storage inverter is controlled to stop powering the load, thereby ensuring that the load is supplied with a reliable and stable power supply at any time during the grid-connection switching, thereby avoiding power supply fluctuations and load power outages.

[0053] The AC output voltage of the energy storage inverter has the same frequency as the grid voltage, for example, both are 50 Hz or 60 Hz.

[0054] The voltage source mode of the energy storage inverter refers to an inverter with voltage control as its output control. In this case, the energy storage inverter outputs a sinusoidal voltage with a certain frequency and amplitude. In voltage source mode, an inductor is connected in series with each AC terminal of the energy storage inverter to act as a buffer. The current source mode of the energy storage inverter refers to an inverter with current control as its output control. In this case, the energy storage inverter outputs a sinusoidal current with a certain frequency and amplitude. In current source mode, a capacitor is connected in parallel between each phase pin of the AC terminal of the energy storage inverter to act as a filter to improve the quality of the AC voltage waveform after grid connection.

[0055] In some embodiments, the grid-connected signal can be triggered by the user. For example, when the energy storage inverter is in an off-grid state and supplies power to the load in voltage source mode, if the user confirms that the grid power supply has been restored, the user triggers the grid-connected signal through a button on a host computer used to manage the energy storage inverter or an operation panel of the energy storage inverter. After receiving the grid-connected signal, the energy storage inverter starts to perform the grid-connected operation.

[0056] In other embodiments, the grid-connection signal is obtained by the energy storage inverter through real-time detection of the power grid. When the energy storage inverter is in an off-grid state and supplies power to the load in voltage source mode, the grid voltage is continuously detected and compared with pre-set conditions, such as a preset frequency and a preset amplitude. If the frequency and amplitude of the grid voltage meet these conditions and reach a certain duration (e.g., multiple preset grid voltage cycles), the energy storage inverter automatically triggers the grid-connection signal and executes the grid-connection process.

[0057] In this embodiment, the grid voltage is phase-locked and the AC output voltage of the energy storage inverter is modulated, so that the phase angle of the AC output voltage of the energy storage inverter leads the phase angle of the grid voltage, and the amplitude of the AC output voltage of the energy storage inverter is higher than the amplitude of the grid voltage.

[0058] The phase angle of the grid voltage is obtained by phase-locking the grid voltage. The phase angle obtained by the phase-locked loop is the phase angle of the grid voltage. The amplitude of the grid voltage is collected at the output end of the grid by the current sensor. In order to make the phase angle of the AC output voltage of the energy storage inverter lead the grid voltage, and the amplitude of the AC output voltage of the energy storage inverter higher than the grid voltage, in this embodiment, a phase angle increment is added to the phase angle of the grid voltage. The tracking phase angle of the AC output voltage of the energy storage inverter is obtained; the tracking amplitude of the AC output voltage of the energy storage inverter is obtained by adding an amplitude increment ΔV to the amplitude of the grid voltage. Finally, based on the tracking phase angle and the tracking amplitude, the AC output voltage of the energy storage inverter is modulated so that the phase angle of the AC output voltage of the energy storage inverter leads the phase angle of the grid voltage and the amplitude of the AC output voltage of the energy storage inverter is higher than the amplitude of the grid voltage.

[0059] For example, the modulation process of the AC output voltage of the energy storage inverter of this embodiment includes the following steps:

[0060] Step 1: Sample the grid voltage and phase-lock to obtain the grid voltage phase angle cos(wt), where w is the grid frequency and t is time; collect the grid voltage amplitude V G .

[0061] Step 2: Add the phase angle increment to the grid voltage phase angle cos(wt) Get the tracking phase angle The magnitude of the grid voltage E G Add the amplitude increment ΔE to obtain the tracking amplitude E G +ΔE.

[0062] Step 3: Use the modulated signal The AC output voltage of the energy storage inverter is modulated, and the AC output voltage of the energy storage inverter reaches the tracking amplitude E by changing the amplitude M of the modulation signal. G +ΔE.

[0063] Through the above steps, the phase angle of the AC output voltage of the energy storage inverter is ahead of the phase angle of the grid voltage, and the amplitude of the AC output voltage of the energy storage inverter is higher than the amplitude of the grid voltage.

[0064] The phase angle increment is determined based on the leading phase angle required to make the current value of the inductor connected in series with the AC end of the energy storage inverter, which acts as a buffer, less than the rated current of the energy storage inverter and approaching 0 under the current frequency and amplitude of the grid voltage.

[0065] In this embodiment, ΔE is sufficiently small compared to the grid voltage E. To illustrate the relationship between the inductor's inductance and the phase angle increment, taking the example of a case where there is only a phase difference but no voltage difference between the energy storage inverter and the grid, the current flowing through the inductor connected in series with the AC end of the energy storage inverter, which acts as a buffer, is simplified to the following formula:

[0066] Where, E is the amplitude of the grid voltage, is the phase angle increment, w is the grid voltage frequency, and L is the inductor's inductance. The grid voltage amplitude and frequency are constants, so a larger inductor's inductance allows for a larger phase angle increment.

[0067] The minimum value of the phase angle increment is determined by the PWM interruption period of the energy storage inverter. For example, for an energy storage inverter with a PWM interruption period of 20 kHz, the minimum value of the phase angle increment is 0.9°.

[0068] In a power system with a grid voltage amplitude of 220V and a grid frequency of 50Hz, the aforementioned amplitude increment and phase angle increment ranges can be obtained based on the different selections of the switching devices and snubber inductors used in the energy storage inverter. For example, in this embodiment, the aforementioned amplitude increment ranges from 1V to 5V, and the aforementioned phase angle increment ranges from 0.5° to 3°.

[0069] Taking the energy storage inverter with a buffer inductance of 2mH and a PWM interruption period of 20kHz as an example, the current flowing through the inductor calculated based on the above formula (1) is 5.5A, which is lower than the rated output current of the energy storage inverter.

[0070] In some embodiments, when the energy storage inverter is a three-phase energy storage inverter and the power grid is a three-phase power grid, in the steps of controlling the phase angle of the AC output voltage of the energy storage inverter to lead the phase angle of the grid voltage and controlling the amplitude of the AC output voltage of the energy storage inverter to be higher than the amplitude of the grid voltage in response to the grid connection signal, the phase angle of the AC output voltage of each phase of the energy storage inverter is controlled to lead the phase angle of the grid voltage of that phase, and the amplitude of the AC output voltage of each phase of the energy storage inverter is controlled to be higher than the amplitude of the grid voltage of that phase, so as to achieve grid connection switching of each phase line. Each phase line is grid-connected and switched at the same time.

[0071] This embodiment also provides an energy storage inverter system. FIG3 is a schematic structural diagram of the energy storage inverter system of this embodiment. As shown in FIG3 , the energy storage inverter system includes: an energy storage inverter 31, an inverter-side relay 32, and a grid-side relay 33. The inverter-side relay 32 and the grid-side relay 33 are connected in series between the AC terminal 40 and the grid connection terminal 50 of the energy storage inverter 31. The connection node between the inverter-side relay 32 and the grid-side relay 33 is also connected to a load terminal 60, which is used to connect a load 70. The energy storage inverter system is used to execute the above-mentioned grid-connected switching method of the energy storage inverter to ensure that the load 70 has no power outages and stable power supply during the grid-connected switching process.

[0072] In the power system, the grid connection terminal 60 can also be connected to another load 80. In the event of a grid fault, the inverter-side relay 32 between the energy storage inverter 31 and the load 70 closes, and the grid-side relay 33 between the grid and the load 70 opens. The energy storage inverter 31 switches to voltage source mode to supply power to the load 70. Due to the grid fault and the disconnection of the grid-side relay 33, power to the load 80 is cut off. The energy storage inverter 31 now operates in an off-grid state, outputting the voltage required by the load 70 in voltage source mode.

[0073] After receiving the grid-connection signal, the energy storage inverter 31 modulates its AC output voltage so that its phase angle leads the grid voltage and its amplitude exceeds the grid voltage. It then controls the grid-side relay 33 to close, allowing the grid to supply power to the load 70. After the grid-side relay 33 has been closed for a preset duration, the inverter-side relay 32 is controlled to open, causing the energy storage inverter 31 to stop supplying power to the load 70. The preset duration can be, for example, one to several grid voltage cycles to ensure that the grid can stably supply power to the load 70.

[0074] Since the power grid is considered to be an infinite AC voltage source, long-term phase-locked control is required to achieve the same frequency and phase of the output voltages of the two for the energy storage inverter to be connected to the power grid. However, the phase-locked response is slow, and the AC output voltage of the energy storage inverter is difficult to accurately control for a long time, which will cause circulating current to damage the equipment. Therefore, after the grid connection switch, the energy storage inverter 31 cannot be connected to the power grid for a long time. After controlling the energy storage inverter 31 to stop supplying power to the load 70, the energy storage inverter 31 switches the working mode to the current source mode, and then controls the inverter side relay 32 to be re-engaged, thereby controlling the energy storage inverter to connect to the power grid in the current source mode. In the current source mode, the output control of the energy storage inverter 31 adopts the current control method, outputting a stable and efficient sinusoidal current, and the output sinusoidal current is the same frequency and phase as the grid voltage, and can remain connected to the grid for a long time.

[0075] In some embodiments, the energy storage inverter 31 is a three-phase energy storage inverter, with each phase of the energy storage inverter 31 being provided with an inverter-side relay 32 and a grid-side relay 33 at the AC end. In related art, zero-crossing grid-connected switching is also employed to minimize damage to the relays from the grid's inrush current at the moment of grid connection. This approach is limited by the switching time control accuracy of the relays used for grid-connected switching. Furthermore, for a three-phase grid system, since the same set of relays on each phase line typically operates simultaneously, there is no single time point at which the grid voltage on all three phases can be guaranteed to be near zero. In contrast, in this embodiment, the aforementioned grid-connected switching method is employed for each phase line. Since the phase and amplitude of the energy storage inverter's AC output voltage are modulated, the difference between the grid voltage and the energy storage inverter's AC output voltage is minimal. Therefore, the current amplitude flowing through the relays at the moment of grid-connected switching is significantly reduced, thus preventing damage to the relays. Furthermore, each set of relays on the three-phase line does not need to be controlled separately, instead using a unified control signal, reducing control complexity.

[0076] Furthermore, using the aforementioned grid-connected switching method, during the grid-connected switching and grid-connected operation process, the AC output voltage amplitude of the energy storage inverter is always higher than that of the grid, and the phase angle of the AC output voltage of the energy storage inverter is always ahead of that of the grid, ensuring that grid energy does not flow back into the energy storage inverter during the grid-connected switching and grid-connected operation process. If grid energy flows back into the energy storage inverter, the energy storage inverter may shut down due to the backflow of energy, causing the energy storage inverter to exit prematurely before the grid can provide stable power to important loads, resulting in power loss or unstable power supply to important loads. In addition, the backflow of energy may also cause damage to the power semiconductors inside the energy storage inverter, causing the bus capacitor voltage to surge, causing damage to the capacitor or even explosion, resulting in damage to the energy storage inverter.

[0077] An embodiment of the present invention further provides an electronic device. This electronic device can be a DSP with independent functions or a controller for an energy storage inverter. The electronic device includes: at least one processor; and a memory communicatively connected to the at least one processor. The memory stores a computer program executable by the at least one processor. When executed by the at least one processor, the computer program causes the electronic device to perform the grid-connected switching method according to an embodiment of the present invention.

[0078] An embodiment of the present invention further provides a non-transitory machine-readable medium storing a computer program, wherein the computer program, when executed by a processor of a computer, is used to enable the computer to execute the grid-connected switching method of an embodiment of the present invention.

[0079] With reference to Figure 4, a block diagram of an electronic device that can be used as a server or client of an embodiment of the present invention will now be described, which is an example of a hardware device that can be applied to various aspects of the present invention. The electronic device is intended to represent various forms of digital electronic computer equipment, such as laptop computers, desktop computers, workstations, personal digital assistants, servers, blade servers, mainframe computers, and other suitable computers. The electronic device can also represent various forms of mobile devices, such as personal digital processing, cellular phones, smart phones, wearable devices and other similar computing devices. The components shown herein, their connections and relationships, and their functions are merely examples and are not intended to limit the implementation of the present invention described and / or required herein.

[0080] As shown in Figure 4, the electronic device includes a computing unit 401, which can perform various appropriate actions and processes according to a computer program stored in a read-only memory (ROM) 402 or a computer program loaded from a storage unit 408 into a random access memory (RAM) 403. In RAM 403, various programs and data required for the operation of the electronic device can also be stored. The computing unit 401, ROM 402, and RAM 403 are connected to each other via a bus 404. An input / output (I / O) interface 405 is also connected to the bus 404.

[0081] Multiple components within the electronic device are connected to the I / O interface 405, including an input unit 406, an output unit 407, a storage unit 408, and a communication unit 409. The input unit 406 can be any type of device capable of inputting information into the electronic device. The input unit 406 can receive input numeric or character information and generate key signal inputs related to user settings and / or function control of the electronic device. The output unit 407 can be any type of device capable of presenting information and can include, but is not limited to, a display, a speaker, a video / audio output terminal, a vibrator, and / or a printer. The storage unit 408 can include, but is not limited to, a magnetic disk or an optical disk. The communication unit 409 allows the electronic device to exchange information / data with other devices via a computer network such as the Internet and / or various telecommunication networks, and can include, but is not limited to, a modem, a network card, an infrared communication device, a wireless communication transceiver, and / or a chipset, such as a Bluetooth device, a WiFi device, a WiMax device, a cellular communication device, and / or the like.

[0082] The computing unit 401 may be a variety of general and / or special processing components with processing and computing capabilities. Some examples of the computing unit 401 include, but are not limited to, a CPU, a graphics processing unit (GPU), various dedicated artificial intelligence (AI) computing chips, various computing units that run machine learning model algorithms, digital signal processors (DSPs), and any appropriate processors, controllers, microcontrollers, etc. The computing unit 401 performs the various methods and processes described above. For example, in some embodiments, the method embodiments of the present invention may be implemented as a computer program, which is tangibly contained in a machine-readable medium, such as a storage unit 408. In some embodiments, part or all of the computer program may be loaded and / or installed on an electronic device via ROM 402 and / or communication unit 409. In some embodiments, the computing unit 401 may be configured to perform the above-described method in any other appropriate manner (e.g., by means of firmware).

[0083] The computer programs for implementing the methods of the embodiments of the present invention may be written in any combination of one or more programming languages. These computer programs may be provided to a processor or controller of a general-purpose computer, a special-purpose computer, or other programmable data processing device, so that when the computer programs are executed by the processor or controller, the functions / operations specified in the flowcharts and / or block diagrams are implemented. The computer programs may be executed entirely on the machine, partially on the machine, as a stand-alone software package, partially on the machine and partially on a remote machine, or entirely on a remote machine or server.

[0084] In the context of an embodiment of the present invention, a machine-readable medium can be a tangible medium that can contain or store a program for use by an instruction execution system, device or equipment or used in combination with an instruction execution system, device or equipment. A machine-readable medium can be a machine-readable signal medium or a machine-readable storage medium. A machine-readable signal medium can include, but is not limited to, an electronic, magnetic, optical, electromagnetic, infrared or semiconductor system, device or equipment, or any suitable combination of the foregoing. A more specific example of a machine-readable storage medium can include an electrical connection based on one or more lines, a portable computer disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a portable compact disk read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing.

[0085] It should be noted that the term "including" and its variations used in the embodiments of the present invention are open-ended, i.e., "including but not limited to." The term "based on" means "based at least in part on." The term "one embodiment" means "at least one embodiment"; the term "another embodiment" means "at least one other embodiment"; and the term "some embodiments" means "at least some embodiments." The modifications of "one" and "a plurality of" mentioned in the embodiments of the present invention are illustrative and non-restrictive. Those skilled in the art should understand that, unless the context clearly indicates otherwise, they should be understood as "one or more."

[0086] The various steps described in the method implementation scheme provided in the embodiments of the present invention may be performed in different orders and / or in parallel. In addition, the method implementation scheme may include additional steps and / or omit the steps shown. The scope of protection of the present invention is not limited in this respect.

[0087] The term "embodiment" as used in this specification refers to specific features, structures, or characteristics described in conjunction with the embodiment that may be included in at least one embodiment of the present invention. The appearance of this phrase in various locations in the specification does not necessarily imply the same embodiment, nor does it imply independence or selectability from other embodiments that are mutually exclusive. The various embodiments in this specification are described in a related manner, and reference is made to the same or similar parts between the various embodiments. In particular, for device, equipment, and system embodiments, since they are generally similar to method embodiments, the description is relatively simple, and reference is made to the description of the method embodiments for related details.

[0088] The above-described embodiments merely illustrate several implementations of the present invention. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, all of which fall within the scope of the present invention. Therefore, the scope of the present invention shall be determined by the appended claims.

Claims

1. A grid-connected switching method for an energy storage inverter, comprising: When the energy storage inverter is in an off-grid state and supplies power to the load in voltage source mode, a grid-connected signal is obtained; In response to the grid-connected signal, controlling the phase angle of the AC output voltage of the energy storage inverter to be ahead of the phase angle of the grid voltage, and controlling the amplitude of the AC output voltage of the energy storage inverter to be higher than the amplitude of the grid voltage; controlling the power grid to supply power to the load; and After the power grid supplies power to the load, the energy storage inverter is controlled to stop supplying power to the load.

2. The method according to claim 1, wherein: Obtaining grid-connected signals includes: Obtain a grid connection signal triggered by a user; or The grid voltage of the grid is detected, and when the frequency and amplitude of the grid voltage within a set time period meet set conditions, the grid connection signal is generated.

3. The method according to claim 1, wherein: In response to the grid-connected signal, controlling the phase angle of the AC output voltage of the energy storage inverter to be ahead of the phase angle of the grid voltage, and controlling the amplitude of the AC output voltage of the energy storage inverter to be higher than the amplitude of the grid voltage includes: Phase-locking the grid voltage to obtain a phase angle of the grid voltage and collecting an amplitude of the grid voltage; Based on the phase angle of the grid voltage and the set phase angle increment, as well as the amplitude of the grid voltage and the set amplitude increment, obtaining a tracking phase angle and a tracking amplitude of the AC output voltage of the energy storage inverter; Based on the tracking phase angle and the tracking amplitude, the AC output voltage of the energy storage inverter is modulated so that the phase angle of the AC output voltage of the energy storage inverter leads the phase angle of the grid voltage, and the amplitude of the AC output voltage of the energy storage inverter is higher than the amplitude of the grid voltage.

4. The method according to claim 3, wherein: The phase angle increment is determined based on the leading phase angle required to make the current value of the inductor connected in series at the AC end of the energy storage inverter less than the rated current of the energy storage inverter and close to 0 under the current frequency and amplitude of the grid voltage, wherein: The current value of the inductor connected in series at the AC end of the energy storage inverter E is the amplitude of the grid voltage, is the phase angle increment, w is the frequency of the grid voltage, and L is the inductance of the inductor.

5. The method according to claim 3, wherein: The value range of the amplitude increment includes: 1V~5V.

6. The method according to claim 3, wherein: The phase angle increment has a value range of 0.5° to 3°.

7. The method according to claim 1, wherein: When the energy storage inverter is in an off-grid state to supply power to the load, the inverter-side relay disposed between the energy storage inverter and the load is energized, and the grid-side relay disposed between the grid and the load is disconnected; Controlling the power grid to supply power to the load includes: The grid-side relay is controlled to be closed so that the grid supplies power to the load.

8. The method according to claim 7, wherein: After the power grid supplies power to the load, controlling the energy storage inverter to stop supplying power to the load includes: After the grid-side relay is energized for a preset time, the inverter-side relay is controlled to be disconnected so that the energy storage inverter stops supplying power to the load.

9. The method according to claim 8, wherein: The preset duration includes the duration of one to several grid voltage cycles of the grid.

10. The method according to claim 1, wherein: After controlling the energy storage inverter to stop supplying power to the load, the method further includes: The energy storage inverter is controlled to operate in a current source mode.

11. The method according to claim 1, wherein: The energy storage inverter is a three-phase energy storage inverter, and the power grid is a three-phase power grid. In the steps of controlling the phase angle of the AC output voltage of the energy storage inverter to be ahead of the phase angle of the power grid voltage, and controlling the amplitude of the AC output voltage of the energy storage inverter to be higher than the amplitude of the power grid voltage in response to the grid-connected signal, the phase angle of the AC output voltage of each phase of the energy storage inverter is controlled to be ahead of the phase angle of the power grid voltage of that phase, and the amplitude of the AC output voltage of each phase of the energy storage inverter is controlled to be higher than the amplitude of the power grid voltage of that phase.

12. An energy storage inverter system, comprising: An energy storage inverter, an inverter-side relay and a grid-side relay, wherein the inverter-side relay and the grid-side relay are connected in series between the AC end and the grid connection end of the energy storage inverter, and the connection node between the inverter-side relay and the grid-side relay is also connected to a load end, and the load end is used to connect a load; the energy storage inverter system is used to execute the grid-connected switching method of the energy storage inverter described in any one of claims 1 to 11.

13. The energy storage inverter system according to claim 12, wherein: The energy storage inverter is a three-phase energy storage inverter, and the inverter-side relay and the grid-side relay are respectively provided at the AC end of each phase of the energy storage inverter.

14. An electronic device comprising: A processor, and a memory storing a program, wherein the program includes instructions, and when the instructions are executed by the processor, the processor executes the grid-connected switching method of the energy storage inverter according to any one of claims 1 to 11.

15. A non-transitory machine-readable medium storing computer instructions, wherein: The computer instructions are used to enable the computer to execute the grid-connected switching method of the energy storage inverter according to any one of claims 1 to 11.

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