Inverter and control method therefor, and energy storage system

Abstract

Provided in the present application are an inverter and a control method therefor, and an energy storage system. When an energy storage battery (400) is depleted and unable to establish a bus voltage for a direct current bus (200), the energy storage battery needs to be charged by means of an external power supply network. Before the external power supply network charges the energy storage battery, an auxiliary power supply circuit (500) is controlled to be activated for a set duration, so as to convert the alternating current voltage of the external power supply network into a direct current voltage, and then convert the direct current voltage into a target direct current voltage, thereby supplying power to the direct current bus to establish the bus voltage; subsequently, a grid-connected control circuit (300) is activated to establish a path from the external power supply network to the energy storage battery, thereby avoiding damage to the inverter when the external power supply network charges the energy storage battery and consequently prolonging the service life of the inverter and improving the reliability of the inverter.

Description

Inverter, control method thereof, and energy storage system

[0001] This application claims priority to the Chinese patent application filed with the China Patent Office on January 30, 2024, with application number 202410130469.0 and invention name “A kind of inverter, its control method and energy storage system”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present application relates to the field of energy storage technology, and more specifically, to an inverter and a control method thereof, and an energy storage system. Background Art

[0003] In existing energy storage systems, if the energy storage battery feeds power, the grid needs to charge the energy storage battery. Before the grid can charge the energy storage battery, it needs to establish a bus voltage on the DC bus. Otherwise, if there is insufficient voltage on the bus capacitor of the DC bus, when the grid-connected relay on the grid side is energized, the grid voltage will charge the bus capacitor through the inverter circuit. At the moment the grid-connected relay is energized, the bus capacitor is nearly short-circuited due to its characteristics, resulting in a very large current on the DC bus. This can cause damage to electronic components connected to the DC bus, preventing the energy storage battery from being charged and reducing the service life and reliability of the energy storage system.

[0004] Summary of the Invention

[0005] In view of this, the present application provides an inverter, a control method thereof, and an energy storage system, which can solve the technical problems existing in the prior art. By providing power to the DC bus through an auxiliary power supply circuit to establish a bus voltage, damage to the inverter is avoided when the energy storage battery is charged by an external power supply network, thereby improving the service life and reliability of the inverter.

[0006] To achieve the above objectives, the technical solutions provided by this application are as follows:

[0007] An inverter comprises: an inverter circuit, a DC bus, a grid-connected control circuit and an auxiliary power supply circuit;

[0008] The DC side of the inverter circuit is electrically connected to the energy storage battery through the DC bus, and the grid-connected side of the inverter circuit is electrically connected to the external power supply network through the grid-connected control circuit;

[0009] The auxiliary power supply circuit is electrically connected between the external power supply network and the DC bus. The auxiliary power supply circuit is used to be controlled to be turned on for a set time before the external power supply network charges the energy storage battery, so as to convert the AC voltage of the external power supply network into a DC voltage, and convert the DC voltage into a target DC voltage, so as to provide power for the DC bus and establish the bus voltage.

[0010] Optionally, the auxiliary power supply circuit includes: an AC switching power supply, an input side of the AC switching power supply is electrically connected to the external power supply network, and an output side of the AC switching power supply is electrically connected to the DC bus.

[0011] Optionally, the auxiliary power supply circuit further includes: a current limiting resistor, wherein the current limiting resistor is electrically connected between the DC bus and the output side of the AC switching power supply.

[0012] Optionally, the auxiliary power supply circuit further includes: a boost circuit, wherein the boost circuit is electrically connected between the DC bus and the output side of the AC switching power supply.

[0013] Optionally, the auxiliary power supply circuit further includes: a current limiting resistor and a boost circuit, the boost circuit is electrically connected between the DC bus and the current limiting resistor, and the current limiting resistor is electrically connected between the boost circuit and the output side of the AC switching power supply.

[0014] Optionally, the inverter further includes: a buck-boost circuit, wherein the buck-boost circuit is electrically connected between the energy storage battery and the DC bus.

[0015] Optionally, the boost circuit reuses the boost part of the buck-boost circuit.

[0016] Optionally, the inverter further includes: a pre-charging circuit, the pre-charging circuit being electrically connected between the DC bus and the energy storage battery, and being configured to provide a pre-charging source for establishing the bus voltage for the DC bus before the energy storage battery outputs power;

[0017] And / or, the inverter further includes a Boost circuit, and the Boost circuit is electrically connected between the photovoltaic power source and the DC bus.

[0018] Optionally, the inverter is a single-phase inverter or a three-phase inverter.

[0019] Accordingly, the present application also provides a method for controlling an inverter, for controlling the above-mentioned inverter, wherein the control method includes:

[0020] Before the external power supply network charges the energy storage battery, the auxiliary power supply circuit is controlled to be turned on, and the auxiliary power supply circuit converts the AC voltage of the external power supply network into a DC voltage, and then converts the DC voltage into a target DC voltage, providing power for the DC bus to establish the bus voltage;

[0021] After the bus voltage is established, performing a grid-connected self-test on the inverter;

[0022] After the inverter passes the grid-connected self-test, controlling to open the grid-connected control circuit and simultaneously controlling to close the auxiliary power supply circuit;

[0023] A path is established between the external power supply network and the energy storage battery, and the external power supply network charges the energy storage battery.

[0024] Correspondingly, the present application also provides an energy storage system, which includes the above-mentioned inverter.

[0025] Compared with the existing technology, the technical solution provided by this application has at least the following advantages:

[0026] The present application provides an inverter, a control method thereof, and an energy storage system, including: the DC side of the inverter circuit is electrically connected to the energy storage battery via the DC bus, and the grid-connected side of the inverter circuit is electrically connected to the external power supply network via the grid-connected control circuit; the auxiliary power supply circuit is electrically connected between the external power supply network and the DC bus, and the auxiliary power supply circuit is controlled to be turned on for a set time before the external power supply network charges the energy storage battery, so as to convert the AC voltage of the external power supply network into a DC voltage, and then convert the DC voltage into a target DC voltage, thereby providing power to the DC bus to establish the bus voltage.

[0027] As can be seen from the above, the technical solution provided by this application requires charging the energy storage battery through an external power supply network when the energy storage battery is not able to establish a bus voltage for the DC bus due to power supply failure. The auxiliary power supply circuit is controlled to be turned on for a set duration before the external power supply network charges the energy storage battery. This allows the auxiliary power supply circuit to convert the AC voltage of the external power supply network into a DC voltage, and then convert the DC voltage into a target DC voltage to provide power to the DC bus and establish the bus voltage. The grid-connected control circuit is then turned on to establish a path from the external power supply network to the energy storage battery. This prevents damage to the inverter when the external power supply network charges the energy storage battery, thereby improving the service life and reliability of the inverter. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the embodiments of the present application 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 merely embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without any creative work.

[0029] FIG1 is a schematic structural diagram of an inverter provided in an embodiment of the present application;

[0030] FIG2 is a schematic structural diagram of another inverter provided in an embodiment of the present application;

[0031] FIG3 is a schematic structural diagram of another inverter provided in an embodiment of the present application;

[0032] FIG4 is a schematic structural diagram of another inverter provided in an embodiment of the present application;

[0033] FIG5 is a schematic structural diagram of another inverter provided in an embodiment of the present application;

[0034] FIG6 is a schematic structural diagram of another inverter provided in an embodiment of the present application;

[0035] FIG7 is a schematic structural diagram of another inverter provided in an embodiment of the present application;

[0036] FIG8 is a schematic structural diagram of another inverter provided in an embodiment of the present application;

[0037] FIG9 is a schematic structural diagram of another inverter provided in an embodiment of the present application;

[0038] FIG10 is a schematic structural diagram of another inverter provided in an embodiment of the present application;

[0039] FIG11 is a flow chart of a method for controlling an inverter provided in an embodiment of the present application;

[0040] FIG12 is a schematic structural diagram of a photovoltaic storage system provided in an embodiment of the present application. DETAILED DESCRIPTION

[0041] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0042] As described in the background technology, before the power grid charges the energy storage battery, it is necessary to establish a bus voltage for the DC bus. Otherwise, if there is insufficient voltage on the bus capacitor of the DC bus, when the grid-connected relay on the grid side is energized, the grid voltage will charge the bus capacitor through the inverter circuit; and at the moment the grid-connected relay is energized, the bus capacitor is almost short-circuited due to its characteristics, resulting in a very large current on the DC bus, which may cause damage to electronic components connected to the DC bus, making it impossible to charge the energy storage battery and reducing the service life and reliability of the inverter.

[0043] Based on this, the embodiments of the present application provide an inverter, a control method thereof, and an energy storage system, which can solve the technical problems existing in the prior art. By providing power to the DC bus through an auxiliary power supply circuit to establish a bus voltage, damage to the inverter is avoided when the energy storage battery is charged by an external power supply network, thereby improving the service life and reliability of the inverter.

[0044] To achieve the above-mentioned objectives, the technical solutions provided in the embodiments of the present application are as follows, which are described in detail with reference to Figures 1 to 12. It should be noted that the external power supply network provided in the embodiments of the present application is a power supply network that provides AC power, which can be a power grid, a generator, etc. This application does not impose any specific restrictions on this, and the following embodiments are all described using the power grid as an example.

[0045] Referring to Figure 1, which is a structural diagram of an inverter provided in an embodiment of the present application, the inverter provided in the embodiment of the present application includes: an inverter circuit 100, a DC bus 200, a grid-connected control circuit 300 and an auxiliary power supply circuit 500.

[0046] The DC side of the inverter circuit 100 is electrically connected to the energy storage battery 400 via the DC bus 200, and the grid-connected side of the inverter circuit 100 is electrically connected to the external power supply network via the grid-connected control circuit 300. Furthermore, the DC side of the inverter circuit 100 provided in the embodiment of the present application can also be electrically connected to a photovoltaic power source PV via the DC bus 200.

[0047] The auxiliary power supply circuit 500 is electrically connected between the external power supply network and the DC bus 200. The auxiliary power supply circuit 500 is controlled to be turned on for a set period of time before the external power supply network charges the energy storage battery 400, so as to convert the AC voltage of the external power supply network into a DC voltage, and convert the DC voltage into a target DC voltage (such as chopping the DC voltage to output the target DC voltage), providing power for the DC bus 200 to establish the bus voltage.

[0048] In one embodiment of the present application, the inverter provided in this embodiment of the present application can be applied to a battery energy storage system or a photovoltaic energy storage system, and this embodiment of the present application does not impose any specific limitations on this. Furthermore, when the inverter circuit provided in this embodiment of the present application is electrically connected to a photovoltaic power source, the photovoltaic power source can be a photovoltaic cell module or a photovoltaic cell string, and this embodiment of the present application does not impose any specific limitations on this.

[0049] It can be understood that the technical solution provided by the embodiment of the present application is that when the energy storage battery is fed and the bus voltage cannot be established for the DC bus, the energy storage battery needs to be charged through the external power supply network. Among them, the auxiliary power supply circuit is controlled to be turned on for a set time before the external power supply network charges the energy storage battery to convert the AC voltage of the external power supply network into a DC voltage, and convert the DC voltage into a target DC voltage, provide power for the DC bus to establish the bus voltage, and then turn on the grid control circuit to establish a path from the external power supply network to the energy storage battery, avoiding damage to the inverter when the external power supply network charges the energy storage battery, thereby improving the service life and reliability of the inverter. Specifically, the bus voltage can be raised to a preset multiple of the AC voltage (the AC voltage is the output side voltage of the inverter circuit, and the bus voltage can be optionally raised to 1.4 times the AC voltage, which needs to be specifically designed according to the actual application) through the auxiliary power supply circuit, so that the grid voltage is basically consistent with the bus voltage, avoiding the problem of current shock.

[0050] Referring to FIG. 2 , which is a schematic diagram of the structure of another inverter provided in an embodiment of the present application, the DC side of the inverter provided in an embodiment of the present application includes a positive circuit and a negative circuit, that is, a DC bus 200 includes a positive DC bus, a negative DC bus, and a bus capacitor C electrically connected between the positive DC bus and the negative DC bus. The positive DC bus is electrically connected to the positive electrode of the photovoltaic power source PV, the positive electrode of the inverter circuit 100, the positive electrode of the energy storage battery 400, and the positive electrode of the auxiliary power circuit 500. The negative DC bus is electrically connected to the negative electrode of the photovoltaic module PV, the negative electrode of the inverter circuit 100, the negative electrode of the energy storage battery 400, and the negative electrode of the auxiliary power circuit 500.

[0051] In order to improve the performance of the inverter, the embodiment of the present application can also design more components for the inverter. Referring to Figure 3, there is a structural diagram of another inverter provided in the embodiment of the present application, wherein the inverter provided in the embodiment of the present application also includes: a buck-boost circuit 600, the buck-boost circuit 600 is electrically connected between the energy storage battery 400 and the DC bus 200. And, the inverter provided in the embodiment of the present application also includes: a pre-charge circuit 700, the pre-charge circuit 700 is electrically connected between the DC bus 200 and the energy storage battery 400, and is used to provide a pre-charge power source when establishing a bus voltage for the DC bus 200 before the energy storage battery 400 outputs. And / or, the inverter provided in the embodiment of the present application also includes: a Boost circuit 800, the Boost circuit 800 is electrically connected between the photovoltaic power supply PV and the DC bus 200.

[0052] It is understandable that the positive and negative poles on the first side of the buck-boost circuit provided in the embodiment of the present application are electrically connected to the positive and negative poles of the energy storage battery, respectively, and the positive and negative poles on the second side of the buck-boost circuit are electrically connected to the positive DC bus and the negative DC bus, respectively. Also, the positive and negative poles on the first side of the pre-charging circuit provided in the embodiment of the present application are electrically connected to the positive and negative poles of the energy storage battery, respectively, and the positive and negative poles on the second side of the pre-charging circuit are electrically connected to the positive and negative poles of the DC bus, respectively. Also, when the inverter includes a buck-boost circuit, the pre-charging circuit is electrically connected between the energy storage battery and the buck-boost circuit, and the positive and negative poles on the second side of the pre-charging circuit are electrically connected to the positive and negative poles on the first side of the buck-boost circuit, respectively. Wherein, the pre-charging circuit is used when the energy storage battery is able to establish a bus voltage for the DC bus, and provides a pre-charging source for the DC bus before the energy storage battery outputs, thereby improving the efficiency of establishing the bus voltage and improving the performance of the inverter.

[0053] In addition, the positive and negative electrodes on the first side of the Boost circuit provided in the embodiments of the present application are electrically connected to the positive and negative electrodes of the photovoltaic power source, respectively, and the positive and negative electrodes on the second side of the Boost circuit are electrically connected to the positive and negative DC bus, respectively. The Boost circuit is used to boost the output voltage of the photovoltaic power source and output it to the DC bus, thereby increasing the applicability of the inverter and further improving the performance of the inverter.

[0054] Referring to Figure 4, which is a structural diagram of another inverter provided in an embodiment of the present application, the auxiliary power supply circuit 500 provided in the embodiment of the present application includes: an AC switching power supply AC-SPS, the input side of the AC switching power supply AC-SPS is electrically connected to the external power supply network, and the output side of the AC switching power supply AC-SPS is electrically connected to the DC bus.

[0055] Among them, the AC switching power supply AC-SPS is used to be controlled to be turned on for a set time before the external power supply network charges the energy storage battery 400. The AC switching power supply AC-SPS converts the AC voltage of the external power supply network into a DC voltage, and converts the DC voltage into a target DC voltage, providing power to the DC bus 200 to establish the bus voltage until the grid-connected control circuit 300 is turned on and the AC switching power supply AC-SPS is controlled to be turned off.

[0056] It can be understood that, on the output side of the AC switching power supply provided in the embodiment of the present application, the positive pole of the AC switching power supply is electrically connected to the positive DC bus, and the negative pole of the AC switching power supply is electrically connected to the negative DC bus. During the operation of the photovoltaic power supply and / or when the energy storage battery is able to establish a bus voltage for the DC bus, the auxiliary power supply circuit can be turned off (i.e., the AC switching power supply is turned off) to ensure the normal operation of the inverter. When charging the energy storage battery, such as when the photovoltaic power supply stops working and the energy storage battery cannot establish a bus voltage, specifically when the photovoltaic power supply stops working at night and the energy storage battery feed cannot establish a bus voltage, the AC switching power supply is controlled to provide power to the DC bus to ensure that the bus voltage of the DC bus is successfully established. Among them, the AC switching power supply provided in the embodiment of the present application includes but is not limited to isolation circuits such as flyback, forward, LLC (resonant circuit), and full bridge.

[0057] Referring to Figure 5, which is a structural diagram of another inverter provided in an embodiment of the present application, the auxiliary power supply circuit 500 provided in the embodiment of the present application further includes: a current limiting resistor R, which is electrically connected between the DC bus 200 and the output side of the AC switching power supply AC-SPS.

[0058] It is understandable that the current-limiting resistor provided in the embodiments of the present application can limit the current output by the AC switching power supply to the DC bus, thereby avoiding current shock to the DC bus and its electrically connected electrical components, and improving the reliability of the inverter. Optionally, the current-limiting resistor provided in the embodiments of the present application can be electrically connected between the positive DC bus and the positive pole of the AC switching power supply, or can be electrically connected between the negative DC bus and the negative pole of the AC switching power supply; in addition, this application does not impose specific restrictions on the resistance value of the current-limiting resistor, and it needs to be selected according to the actual application.

[0059] Referring to Figure 6, which is a structural diagram of another inverter provided in an embodiment of the present application, the auxiliary power supply circuit 500 provided in the embodiment of the present application further includes: a boost circuit 510, and the boost circuit 510 is electrically connected between the DC bus 200 and the output side of the AC switching power supply AC-SPS.

[0060] It is understood that when the AC switching power supply provided in the embodiments of the present application is unable to establish a higher bus voltage, a boost circuit is electrically connected between the AC switching power supply and the DC bus. The output of the AC switching power supply is boosted by the boost circuit and then transmitted to the DC bus, ensuring the successful establishment of the bus voltage. The positive electrode on the output side of the boost circuit is electrically connected to the positive DC bus, and the negative electrode on the output side of the boost circuit is electrically connected to the negative DC bus; and the positive electrode on the input side of the boost circuit is electrically connected to the positive electrode on the output side of the AC switching power supply, and the negative electrode on the input side of the boost circuit is electrically connected to the negative electrode on the output side of the AC switching power supply.

[0061] It should be noted that in the inverter provided in the embodiment of the present application, whether the output side of the AC switching power supply is connected to a boost circuit needs to be specifically analyzed based on the circuit design requirements and the actual application scenario. For example, the maximum output voltage of the AC switching power supply can be 400V, but the actual bus voltage to be established needs to reach 1600V. At this time, the output voltage of the AC switching power supply cannot meet the establishment of the bus voltage, and a boost circuit needs to be connected for boosting; if the bus voltage to be established is not greater than 400V, then there is no need to connect the boost circuit, and the AC switching power supply is directly electrically connected to the bus. The above-mentioned example of determining whether the switching power supply needs to be connected to a boost circuit based on the bus voltage requirement is only one of many reference factors. In actual applications, there are many factors that need to be considered, such as whether the size of the selected device matches the circuit, the type of AC switching power supply, etc. This application does not make specific restrictions on this. Whether it is necessary to connect a boost circuit to the output side of the AC switching power supply is determined based on actual needs.

[0062] In one embodiment of the present application, the auxiliary power supply circuit provided herein may also include a current-limiting resistor and a boost circuit to ensure the successful establishment of the bus voltage while preventing damage to electrical components caused by inrush current. Referring to FIG7 , which is a schematic structural diagram of another inverter provided in an embodiment of the present application, the auxiliary power supply circuit provided in an embodiment of the present application further includes: a current-limiting resistor R and a boost circuit 510 . The boost circuit 510 is electrically connected between the DC bus 200 and the current-limiting resistor R, and the current-limiting resistor R is electrically connected between the boost circuit 510 and the output side of the AC switching power supply (AC-SPS).

[0063] It is understandable that when the AC switching power supply provided in the embodiment of the present application is unable to establish a higher bus voltage, a boost circuit is electrically connected between the AC switching power supply and the DC bus, and the output of the AC switching power supply is boosted by the boost circuit and transmitted to the DC bus to ensure the successful establishment of the bus voltage. At the same time, a current limiting resistor is electrically connected between the boost circuit and the output side of the AC switching power supply to limit the output current of the AC switching power supply, thereby avoiding current shock to the electrical components electrically connected to the output side of the AC switching power supply and improving the reliability of the inverter. Optionally, the current limiting resistor provided in the embodiment of the present application can be electrically connected between the positive pole of the boost circuit input side and the positive pole of the AC switching power supply output side, or electrically connected between the negative pole of the boost circuit input side and the negative pole of the AC switching power supply output side; in addition, the resistance value of the current limiting resistor is not specifically limited in this application and needs to be specifically selected according to the actual application.

[0064] As shown in FIG. 3 to FIG. 7 , the inverter provided in the embodiment of the present application further includes: a buck-boost circuit 600 , which is electrically connected between the energy storage battery 400 and the DC bus 200 .

[0065] It will be appreciated that the positive and negative electrodes on the first side of the buck-boost circuit provided in the embodiments of the present application are electrically connected to the positive and negative electrodes of the energy storage battery, respectively, and the positive and negative electrodes on the second side of the buck-boost circuit are electrically connected to the positive and negative DC bus, respectively. The buck-boost circuit is configured to boost the output voltage of the energy storage battery when the energy storage battery establishes a bus voltage for the DC bus, ensuring successful establishment of the bus voltage; and to step down the voltage output from the power grid to the energy storage battery when the power grid is charging the energy storage battery, thereby improving the reliability of the inverter.

[0066] Furthermore, the boost circuit provided in the embodiment of the present application can reuse the boost part of the buck-boost circuit to reduce the number of components of the inverter and reduce the cost of the inverter. Referring to Figure 8, there is shown a structural schematic diagram of another inverter provided in the embodiment of the present application, wherein the boost circuit 510 provided in the embodiment of the present application reuses the boost part of the buck-boost circuit 600. That is, the positive pole on the output side of the AC switching power supply AC-SPS is electrically connected to the positive pole on the first side of the buck-boost circuit 600, and the negative pole on the output side of the AC switching power supply AC-SPS is electrically connected to the negative pole on the first side of the buck-boost circuit 600. In addition, when the auxiliary power supply circuit 500 includes a current limiting resistor R, the current limiting resistor R can be electrically connected between the positive pole on the output side of the AC switching power supply AC-SPS and the positive pole on the first side of the buck-boost circuit 600, or, electrically connected between the negative pole on the output side of the AC switching power supply AC-SPS and the negative pole on the first side of the buck-boost circuit 600.

[0067] It is understandable that the inverter provided in the embodiments of the present application turns off the AC switching power supply when the photovoltaic power supply and the energy storage battery are operating normally, and the buck-boost circuit operates normally according to the actual scenario. When the photovoltaic power supply stops working and the energy storage battery feed is unable to establish a bus voltage for the DC bus, the AC switching power supply is turned on, and the buck-boost circuit is simultaneously turned into boost mode. The output of the AC switching power supply is boosted by the buck-boost circuit and then output to the DC bus, successfully establishing the bus voltage.

[0068] In one embodiment of the present application, the inverter provided in the embodiment of the present application is a single-phase inverter or a three-phase inverter, and the specific inverter may be a split-phase topology inverter.

[0069] Referring to FIG9 , which is a schematic diagram of the structure of another inverter provided in an embodiment of the present application, the inverter may be a single-phase inverter, and the grid-connected control circuit 300 includes a DC switching power supply 310, a relay control circuit 320, a phase branch 301, and a neutral branch 302. Furthermore, on the output side of the inverter circuit 100, a capacitor is connected between the phase branch 301 and the neutral branch 302. Either the phase branch 301 or the neutral branch 302 includes two relay switches connected in series between the inverter circuit 100 and the grid. In addition, the positive pole on the input side of the DC switching power supply 310 is electrically connected to the positive DC bus of the DC bus 200, and the negative pole on the input side of the DC switching power supply 310 is electrically connected to the negative DC bus of the DC bus 200; the positive pole on the output side of the DC switching power supply 310 is electrically connected to the positive pole of the relay control circuit 320, and the negative pole on the output side of the DC switching power supply 310 is electrically connected to the negative pole of the relay control circuit 320, and the control side of the relay control circuit 320 is electrically connected to the relay switches of the phase branch 301 and the neutral branch 302.

[0070] Referring to Figure 10, a schematic diagram of the structure of another inverter provided in an embodiment of the present application is shown, wherein the inverter can be a split-phase topology inverter. The grid-connected control circuit 300 includes a DC switching power supply 310, a relay control circuit 320, a phase branch 303, a phase branch 304, and a neutral branch 305. On the output side of the inverter circuit 100, a capacitor is connected between the phase branch 303 and the neutral branch 305, and a capacitor is connected between the phase branch 304 and the neutral branch 305. Similarly, on the grid side, a capacitor is connected between the phase branch 303 and the neutral branch 305, and a capacitor is connected between the phase branch 304 and the neutral branch 305. Among them, any one of the phase branch 303, the phase branch 304, and the neutral branch 305 includes two relay switches connected in series between the inverter circuit 100 and the grid. In addition, the positive pole on the input side of the DC switching power supply 310 is electrically connected to the positive DC bus of the DC bus 200, and the negative pole on the input side of the DC switching power supply 310 is electrically connected to the negative DC bus of the DC bus 200; the positive pole on the output side of the DC switching power supply 310 is electrically connected to the positive pole of the relay control circuit 320, and the negative pole on the output side of the DC switching power supply 310 is electrically connected to the negative pole of the relay control circuit 320, and the control side of the relay control circuit 320 is electrically connected to the relay switches of the phase branch 301 and the neutral branch 302.

[0071] It can be understood that in the inverter provided in the embodiment of the present application, after the auxiliary power supply circuit successfully establishes the bus voltage for the DC bus, the DC switching power supply powers on the relay control circuit, and the relay control circuit controls the relay switches of the phase branch and the neutral branch to be attracted, so that the voltage of the power grid can be transmitted to the energy storage battery for charging.

[0072] Accordingly, an embodiment of the present application further provides a method for controlling an inverter, which is used to control the inverter provided by any of the above embodiments. Referring to FIG11 , which is a flow chart of a method for controlling an inverter provided by an embodiment of the present application, the control method includes:

[0073] S1. Before the external power supply network charges the energy storage battery, the auxiliary power supply circuit is controlled to turn on. The auxiliary power supply circuit converts the AC voltage of the external power supply network into a DC voltage, and then converts the DC voltage into a target DC voltage to provide power for the DC bus and establish the bus voltage.

[0074] S2. After the bus voltage is established, the inverter is subjected to a grid-connected self-test. The grid-connected self-test determines whether the output parameters of the inverter circuit are consistent with the parameters of the grid, such as current and voltage, to avoid the grid current impacting the inverter and causing damage to the components when the parameters are inconsistent.

[0075] S3. After the inverter passes the grid-connected self-test, the grid-connected control circuit is controlled to be turned on and the auxiliary power supply circuit is controlled to be turned off.

[0076] S4. Establish a path between the external power supply network and the energy storage battery, and the external power supply network charges the energy storage battery.

[0077] Correspondingly, an embodiment of the present application further provides an energy storage system, which includes the inverter provided by any one of the above embodiments.

[0078] Optionally, the energy storage system provided in the embodiments of the present application may be a battery energy storage system or a photovoltaic energy storage system, and the embodiments of the present application do not impose any specific restrictions on this. Specifically, FIG12 is a schematic diagram of the structure of a photovoltaic energy storage system provided in the embodiments of the present application, wherein the photovoltaic energy storage system includes the inverter 10 provided in any of the above embodiments.

[0079] In addition, an energy storage battery 400 and a photovoltaic power source PV are electrically connected to the DC bus of the inverter 10, and the inverter 10 is electrically connected to an external power supply network (such as the power grid shown in the figure).

[0080] An embodiment of the present application provides an inverter, a control method thereof, and an energy storage system, including: a DC side of an inverter circuit electrically connected to an energy storage battery via a DC bus, and a grid-connected side of the inverter circuit electrically connected to an external power supply network via a grid-connected control circuit; an auxiliary power supply circuit electrically connected between the external power supply network and the DC bus, the auxiliary power supply circuit being controlled to be turned on for a set time before the external power supply network charges the energy storage battery, so as to convert the AC voltage of the external power supply network into a DC voltage, and then convert the DC voltage into a target DC voltage, thereby providing power to the DC bus and establishing a bus voltage.

[0081] As can be seen from the foregoing, the technical solution provided by the embodiments of the present application requires charging the energy storage battery through an external power supply network when the energy storage battery is not able to establish a bus voltage for the DC bus due to power supply failure. The auxiliary power supply circuit is controlled to be turned on for a set duration before the external power supply network charges the energy storage battery. This allows the auxiliary power supply circuit to convert the AC voltage of the external power supply network into a DC voltage, and then convert the DC voltage into a target DC voltage, providing power to the DC bus to establish the bus voltage. The grid-connected control circuit is then turned on to establish a path from the external power supply network to the energy storage battery. This prevents damage to the inverter when the external power supply network charges the energy storage battery, thereby improving the service life and reliability of the inverter.

[0082] In the description of this application, it should be understood that the orientation or position relationship indicated by terms such as "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. is based on the orientation or position relationship shown in the accompanying drawings, and is only for the convenience of describing this application and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on this application.

[0083] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature specified as "first" or "second" may explicitly or implicitly include at least one such feature. Throughout the description of this application, "plurality" means at least two, for example, two, three, etc., unless otherwise specifically defined.

[0084] In this application, unless otherwise specified or limited, terms such as "installed," "connected," "connect," and "fixed" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integration; mechanical connections, electrical connections, or communication between them; direct connections or indirect connections through an intermediate medium; internal communication between two elements, or interaction between two elements, unless otherwise specified. Those skilled in the art will understand the specific meanings of the above terms in this application based on specific circumstances.

[0085] In this application, unless otherwise expressly specified or limited, when a first feature is "above" or "below" a second feature, it may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Furthermore, when a first feature is "above," "above," or "above" a second feature, it may mean that the first feature is directly above or diagonally above the second feature, or simply means that the first feature is at a higher level than the second feature. When a first feature is "below," "below," or "below" a second feature, it may mean that the first feature is directly below or diagonally below the second feature, or simply means that the first feature is at a lower level than the second feature.

[0086] In this application, the use of the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine different embodiments or examples described in this specification and features of different embodiments or examples, unless they are mutually inconsistent.

[0087] Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limitations on the present application. Ordinary technicians in this field can change, modify, replace and modify the above embodiments within the scope of the present application.

Claims

1. An inverter, characterized in that: include: Inverter circuit, DC bus, grid-connected control circuit and auxiliary power supply circuit; The DC side of the inverter circuit is electrically connected to the energy storage battery through the DC bus, and the grid-connected side of the inverter circuit is electrically connected to the external power supply network through the grid-connected control circuit; The auxiliary power supply circuit is electrically connected between the external power supply network and the DC bus. The auxiliary power supply circuit is used to be controlled to be turned on for a set time before the external power supply network charges the energy storage battery, so as to convert the AC voltage of the external power supply network into a DC voltage, and convert the DC voltage into a target DC voltage, so as to provide power for the DC bus and establish the bus voltage.

2. The inverter according to claim 1, characterized in that The auxiliary power supply circuit includes an AC switching power supply, an input side of the AC switching power supply is electrically connected to the external power supply network, and an output side of the AC switching power supply is electrically connected to the DC bus.

3. The inverter according to claim 2, characterized in that: The auxiliary power supply circuit further includes a current limiting resistor electrically connected between the DC bus and the output side of the AC switching power supply.

4. The inverter according to claim 2, characterized in that: The auxiliary power supply circuit further includes a boost circuit electrically connected between the DC bus and the output side of the AC switching power supply.

5. The inverter according to claim 2, characterized in that: The auxiliary power supply circuit further includes: a current limiting resistor and a boost circuit, wherein the boost circuit is electrically connected between the DC bus and the current limiting resistor, and the current limiting resistor is electrically connected between the boost circuit and the output side of the AC switching power supply.

6. The inverter according to claim 4 or 5, characterized in that: The inverter further includes a buck-boost circuit electrically connected between the energy storage battery and the DC bus.

7. The inverter according to claim 6, characterized in that: The boost circuit reuses the boost part of the boost-buck circuit.

8. The inverter according to claim 1, characterized in that The inverter further includes: a pre-charging circuit, the pre-charging circuit being electrically connected between the DC bus and the energy storage battery, and being configured to provide a pre-charging source for establishing the bus voltage for the DC bus before the energy storage battery outputs power; And / or, the inverter further includes: a Boost circuit, wherein the Boost circuit is electrically connected between the photovoltaic power source and the DC bus.

9. The inverter according to claim 1, characterized in that: The inverter is a single-phase inverter or a three-phase inverter.

10. A method for controlling an inverter, characterized in that: Used to control the inverter according to any one of claims 1 to 9, wherein the control method includes: Before the external power supply network charges the energy storage battery, the auxiliary power supply circuit is controlled to be turned on, and the auxiliary power supply circuit converts the AC voltage of the external power supply network into a DC voltage, and then converts the DC voltage into a target DC voltage, providing power for the DC bus to establish the bus voltage; After the bus voltage is established, performing a grid-connected self-test on the inverter; After the inverter passes the grid-connected self-test, controlling to open the grid-connected control circuit and simultaneously controlling to close the auxiliary power supply circuit; A path is established between the external power supply network and the energy storage battery, and the external power supply network charges the energy storage battery.

11. An energy storage system, characterized in that: The energy storage system includes the inverter according to any one of claims 1 to 9.

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