Inverter control method, inverter and energy storage system

Abstract

The invention provides an inverter control method, an inverter and an energy storage system, and the method comprises the steps: employing a first reference current instruction at an initial moment when the inverter is switched from a grid-connected control mode to an off-grid control mode, and enabling the first reference current instruction to be a first reference current instruction at a previous moment when the inverter is switched to the off-grid control mode; according to the invention, the voltage output by the inverter at the initial moment of the off-grid control mode and the voltage output by the power grid to the grid-connected port at the previous moment can be realized, so that when the power grid is in an abnormal state, the inverter is quickly switched to supply power to the load, and in the process of switching the grid-connected mode to the off-grid mode, the inverter quickly supplies power to the load with the same voltage as the power grid. And rapid grid-connected and off-grid switching of the inverter is realized. And when the inverter is in the off-grid control mode, a first reference current instruction is generated according to the real-time output voltage and the reference output voltage of the AC output port of the inverter, so that stable control of the inverter in the off-grid control mode is realized, and the steady-state performance of the inverter in the off-grid control mode is ensured.

Description

Technical Field

[0001] The present application relates to the technical field of energy storage equipment, and in particular to a control method of an inverter, an inverter and an energy storage system. Background Art

[0002] In an energy storage system, if the power grid connected to the energy storage system suddenly loses power, in order to ensure that the load does not lose power, the working state of the energy storage system needs to be quickly switched, and the load power supply from the power grid to the inverter in the energy storage system needs to be switched in time. Therefore, the inverter needs to be able to quickly respond to the power outage of the power grid and switch between the grid and the off-grid. When the energy storage system is switched between the grid and the off-grid, the control parameters of the inverter are generally adjusted to achieve a faster dynamic response, but the adjusted parameters may not be effective when the inverter is in the off-grid steady state. Summary of the invention

[0003] In view of this, the present application provides a control method of an inverter, an inverter and an energy storage system, so as to achieve rapid on-grid and off-grid switching of the inverter without affecting the steady-state performance of the inverter.

[0004] The first aspect of the present application provides a control method for an inverter, wherein the input port of the inverter is used to connect a DC power supply, the AC output port of the inverter is used to connect a load, the grid-connected port of the inverter is used for the power grid, and the load is powered by the inverter and / or the power grid; the control method comprises: in response to the power grid being in an abnormal state, controlling the inverter to switch from a grid-connected control mode to an off-grid control mode; when the inverter is in the off-grid control mode, obtaining a real-time output voltage and a real-time output current of the AC output port; generating a first reference current instruction according to the real-time output voltage and the reference output voltage; generating a drive signal according to the first reference current instruction and the real-time output current, the drive signal being used to drive the AC output port of the inverter to output a reference output voltage to power the load; wherein the first reference current instruction at the switching moment when the inverter switches to the off-grid control mode is the first reference current instruction at the previous moment when the inverter switches to the off-grid control mode.

[0005] In the above embodiment, when the power grid is in an abnormal state, the inverter is controlled to switch from the grid-connected control mode to the off-grid control mode, the real-time output voltage and the real-time output current of the inverter's AC output port are obtained, a first reference current instruction is generated according to the real-time output voltage and the reference output voltage, and a drive signal is generated according to the first reference current instruction and the real-time output current to drive the inverter's AC output port to output the reference output voltage to power the load, thereby achieving stable control of the inverter in the off-grid control mode and ensuring the steady-state performance of the inverter in the off-grid control mode. At the initial moment when the inverter switches from the grid-connected control mode to the off-grid control mode, the first reference current instruction used is the first reference current instruction at the previous moment when the inverter switches to the off-grid control mode, that is, the first reference current instruction at the last moment when the inverter is in the grid-connected control mode. By using the first reference current instruction and the real-time output current to generate a drive signal, the voltage output by the inverter at the initial moment of the off-grid control mode can be the same as the voltage output by the power grid to the grid-connected port at the previous moment, that is, the voltage output by the inverter at the initial moment of the off-grid control mode is the same as the voltage output to the grid-connected port before the grid is abnormal. Then, when the grid is in an abnormal state, the inverter is quickly switched to supply power to the load, and in the process of switching from the grid-connected control mode to the off-grid mode, the inverter quickly supplies power to the load at the same voltage as the grid, which can effectively prevent the load from losing power when the power supply is switched, shorten the dynamic adjustment process of the inverter switching from the grid-connected control mode to the off-grid control mode, and enable the inverter to enter the off-grid stable state faster.

[0006] In one embodiment, generating a first reference current instruction according to the real-time output voltage and the reference output voltage includes: obtaining a voltage deviation value according to the real-time output voltage and the reference output voltage; and performing deviation adjustment on the voltage deviation value to obtain the first reference current instruction.

[0007] In one embodiment, a drive signal is generated according to a first reference current instruction and a real-time output current, including: generating a real-time current instruction according to the real-time output current; obtaining a current deviation value according to the first reference current instruction and the real-time current instruction; and generating a drive signal according to the current deviation value.

[0008] In one embodiment, the real-time current instruction includes a first real-time instruction and a second real-time instruction; the real-time current instruction is generated according to the real-time output current, including: generating the first real-time instruction and the second real-time instruction according to the real-time output current; correspondingly, the current deviation value is obtained according to the first reference current instruction and the real-time current instruction, including: obtaining the first current deviation value according to the first reference current instruction and the first real-time instruction; obtaining the second current deviation value according to the second reference current instruction and the second real-time instruction; generating a drive signal according to the current deviation value, including: performing deviation adjustment on the first current deviation value to obtain a first voltage value; adjusting and controlling the second current deviation value to obtain a second voltage value; and obtaining a drive signal according to the first voltage value and the second voltage value.

[0009] In one embodiment, the inverter includes an inverter circuit, the output end of the inverter circuit is connected to the grid-connected port through a first relay and a second relay connected in series, and the output end of the inverter circuit is connected to the AC output port through the first relay; controlling the inverter to switch from a grid-connected control mode to an off-grid control mode includes: controlling the first relay to remain in an on state, and controlling the second relay to disconnect.

[0010] In one embodiment, the control method also includes: when the inverter is in a grid-connected control mode, obtaining a real-time input voltage and a real-time output current at the input end of the inverter; generating a first reference current instruction according to the real-time input voltage and a reference input voltage; generating a drive signal according to the first reference current instruction and the real-time output current, the drive signal being used to control the voltage of the input port of the inverter to be stable at the reference input voltage.

[0011] In one embodiment, the control method further includes: in response to the power grid returning to normal state, obtaining voltage information of the power grid; pre-synchronizing the voltage of the AC output port of the inverter with the power grid according to the voltage information so that the voltage of the AC output port of the inverter is synchronized with the voltage of the power grid; and controlling the inverter to switch from an off-grid control mode to a grid-connected control mode.

[0012] A second aspect of the present application provides an inverter, comprising an inverter circuit and a control circuit, wherein the input end of the inverter circuit is connected to a DC power supply through an input port of the inverter, the output end of the inverter circuit is connected to a load through an AC output port of the inverter, and the output end of the inverter circuit is also connected to a power grid through a grid-connected port of the inverter, and the load is powered by the inverter and / or the grid; the control circuit is used to: when the inverter switches from a grid-connected control mode to an off-grid control mode, use a first reference current instruction at a previous moment as a first reference current instruction at a current moment; obtain a real-time output current of the inverter circuit, and generate a drive signal based on the real-time output current and the first reference current instruction, the drive signal being used to drive the inverter circuit to output a voltage that is the same as the voltage of the grid-connected port at the previous moment.

[0013] In one embodiment, the output end of the inverter circuit is connected to the grid-connected port through a first relay and a second relay connected in series, and the output end of the inverter circuit is connected to the AC output port through the first relay; the control circuit is also used to: control the first relay to remain in the on state, and control the second relay to be disconnected, so as to control the inverter to switch from the grid-connected control mode to the off-grid control mode.

[0014] The third aspect of the present application provides an energy storage system, characterized in that the energy storage system includes an energy storage battery and an inverter, the inverter includes an inverter circuit and a control circuit, the input end of the inverter circuit is connected to the energy storage battery through the input port of the inverter, the output end of the inverter circuit is connected to the load through the AC output port of the inverter, the output end of the inverter circuit is also connected to the power grid through the grid-connected port of the inverter, and the load is powered by the inverter and / or the grid; the control circuit is used to: when the inverter switches from the grid-connected control mode to the off-grid control mode, use the first reference current instruction at the previous moment as the first reference current instruction at the current moment; obtain the real-time output current of the inverter circuit, and generate a drive signal according to the real-time output current and the first reference current instruction, the drive signal is used to drive the inverter circuit to output the same voltage as the grid-connected port at the previous moment. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a module schematic diagram of the inverter device provided in an embodiment of the present application.

[0016] Figure 2 It is a schematic diagram of the circuit structure of the inverter provided in an embodiment of the present application.

[0017] Figure 3 It is a flow chart of the inverter control method provided in the embodiment of the present application.

[0018] Figure 4 yes Figure 3 Detailed flowchart of step S300 in FIG.

[0019] Figure 5 yes Figure 3 Detailed flowchart of step S400 in FIG.

[0020] Figure 6 yes Figure 5 Detailed flowchart of step S430 in FIG.

[0021] Figure 7 It is a flow chart of a control method for an inverter provided in another embodiment of the present application.

[0022] Figure 8 It is a flowchart of a control method for an inverter provided in yet another embodiment of the present application.

[0023] Fig. 9It is a specific control block diagram of the inverter control method provided in the embodiment of the present application.

[0024] Fig.10 It is a module schematic diagram of the energy storage system provided in an embodiment of the present application. DETAILED DESCRIPTION

[0025] It should be noted that the terms "first" and "second" in the specification, claims and drawings of the present application are used to distinguish similar objects rather than to describe a specific order or sequence.

[0026] It should also be noted that the method disclosed in the embodiments of the present application or the method shown in the flowchart includes one or more steps for implementing the method. Without departing from the scope of the claims, the execution order of multiple steps can be interchangeable with each other, and some of the steps can also be deleted.

[0027] Some embodiments will be described below in conjunction with the accompanying drawings. In the absence of conflict, the following embodiments and features in the embodiments may be combined with each other.

[0028] In an energy storage system, if the power grid connected to the energy storage system suddenly loses power, in order to ensure that the load does not lose power, the working state of the energy storage system needs to be quickly switched, and the load power supply from the power grid to the inverter in the energy storage system needs to be switched in time. In order to ensure that the load power supply quickly returns to normal, the inverter needs to quickly output the same voltage as the power grid. However, when the related technology switches the working state of the energy storage system, it is difficult to ensure that the load does not lose power during the switching process.

[0029] To this end, the present application provides an inverter control method, an inverter, and an energy storage system, so as to achieve rapid on-grid and off-grid switching of the inverter without affecting the steady-state performance of the inverter.

[0030] See also Figure 1 , Figure 1 Schematic diagram of a module of an inverter 100 provided in an embodiment of the present application. Figure 1 As shown, the inverter 100 includes an inverter circuit 110 and a control circuit 120. The input end of the inverter circuit 110 is connected to the DC power supply 20 through the input port 130 of the inverter 100, the output end of the inverter circuit 110 is connected to the load 30 through the AC output port 140 of the inverter 100, and the output end of the inverter circuit 110 is also connected to the power grid 40 through the grid-connected port 150 of the inverter 100. The load 30 is powered by the inverter 100 and / or the power grid 40. The control circuit 120 is used to control the operation of the inverter circuit 110, thereby realizing the control of the operation of the inverter 100. Specifically, the control circuit 120 is used to control the on and off of the switch tube in the inverter circuit 110, thereby controlling the operation of the inverter circuit 110.

[0031] The inverter circuit 110 can be used to convert the DC power input by the DC power source 20 into AC power and then output it to the AC output port 140 and / or the grid-connected port 150, that is, to invert the DC power into AC power and then supply power to the load 30 and / or to the grid 40. The inverter circuit 110 can also convert the AC power input from the grid 40 to the grid-connected port 150 into DC power and output it to the DC power source 20 to charge the DC power source 20, that is, to rectify the AC power into DC power and then charge the DC power source 20.

[0032] It is understandable that the output end of the inverter circuit 110 can be connected to the grid port 150 through the first relay K1 and the second relay K2 connected in series to connect to the grid 40. The output end of the inverter circuit 110 can be connected to the AC output port 140 through the first relay K1 to connect to the load 30.

[0033] When the grid 40 supplies power to the load 30, the control circuit 120 can control the first relay K1 and the second relay K2 to be turned on. When the grid 40 loses power, the control circuit 120 can control the first relay K1 to remain turned on and control the second relay K2 to be turned off, so that the inverter circuit 110 supplies power to the load 30.

[0034] It can be understood that in order to meet the safety requirements of the inverter 100, the first relay K1 and the second relay K2 are arranged outside the inverter 100, and the first relay K1 and the second relay K2 can be manually operated to be turned on and off.

[0035] In the embodiment of the present application, the DC power source 20 may be a storage battery or a photovoltaic module. It is understood that when the inverter 100 is capable of charging the DC power source 20, the DC power source 20 is a storage battery.

[0036] See also Figure 2 , Figure 2 FIG. 1 shows a circuit topology diagram of the inverter 100 according to an embodiment of the present application. Figure 2 As shown, the inverter circuit 110 includes a first bridge arm 111, a second bridge arm 112, a third bridge arm 113, a positive DC bus and a negative DC bus. Both ends of the first bridge arm 111, the second bridge arm 112 and the third bridge arm 113 are connected in parallel between the positive DC bus and the negative DC bus. The midpoints of the first bridge arm 111, the second bridge arm 112 and the third bridge arm 113 are connected to the three phase lines of the power grid 40 through three groups of first relays K1 and second relays K2 connected in series.

[0037] Furthermore, the first bridge arm 111, the second bridge arm 112 and the third bridge arm 113 respectively include connected upper switch tubes and lower switch tubes, and the midpoint is the connection node of the upper switch tube and the lower switch tube. The control circuit 120 can be used to control the on and off of the upper switch tube and the lower switch tube of each bridge arm, thereby controlling the operation of the inverter 100.

[0038] Specifically, the first bridge arm 111 includes a first upper switch tube S1 and a first lower switch tube S2, the first end of the first upper switch tube S1 is connected to the positive DC bus, the second end of the first upper switch tube S1 is connected to the first end of the first lower switch tube S2, and the second end of the first lower switch tube S2 is connected to the negative DC bus.

[0039] The second bridge arm 112 includes a second upper switch tube S3 and a second lower switch tube S4, wherein a first end of the second upper switch tube S3 is connected to the positive DC bus, a second end of the second upper switch tube S3 is connected to a first end of the second lower switch tube S4, and a second end of the second lower switch tube S4 is connected to the negative DC bus.

[0040] The third bridge arm 113 includes a third upper switch tube S5 and a third lower switch tube S6. The first end of the third upper switch tube S5 is connected to the positive DC bus, the second end of the third upper switch tube S5 is connected to the first end of the third lower switch tube S6, and the second end of the third lower switch tube S6 is connected to the negative DC bus.

[0041] In this example, the inverter 100 is a three-phase inverter. Of course, the inverter provided in this application is not limited to Figure 2 The three-phase inverter shown may also be an inverter of other circuit forms, such as a single-phase inverter.

[0042] The inverter control method provided in the embodiment of the present application can be applied to Figure 2 Of course, it can be understood that the control method of the inverter provided in the embodiment of the present application can be applied to inverters 100 of various circuit forms, not limited to Figure 2 The inverter 100 shown. In at least one implementation manner, the control method of the inverter provided in the embodiment of the present application can be executed by the control circuit 120 mentioned above.

[0043] See also Figure 3 , Figure 3 Flow chart of the control method of the inverter provided in the embodiment of the present application. Figure 3 As shown, the inverter control method includes the following steps S100-S400.

[0044] S100: In response to the power grid being in an abnormal state, control the inverter to switch from a grid-connected control mode to an off-grid control mode.

[0045] The abnormal state of the power grid 40 includes a power failure of the power grid 40, and the control circuit 120 can determine whether the power grid 40 is in an abnormal state by real-time detection of the voltage and frequency of the power grid 40. For example, when it is detected that the effective value of the voltage of the power grid 40 in a power frequency cycle is lower than a preset voltage threshold, it is confirmed that the power grid 40 is in an abnormal state.

[0046] It can be understood that the grid-connected control mode refers to the control mode of the inverter 100 when it is connected to the grid 40, and the off-grid control mode refers to the control mode of the inverter 100 when it is powered off and not connected to the grid 40.

[0047] When the control circuit 120 controls the inverter 100 to switch from the grid-connected control mode to the off-grid control mode, the control circuit 120 can control the first relay K1 to remain in the on state and control the second relay K2 to be disconnected, so that the load 30 is disconnected from the grid 40, and the load 30 is powered only by the inverter 100.

[0048] When the inverter 100 is in the grid-connected control mode, the control circuit 120 needs to control the first relay K1 and the second relay K2 to remain in the on state.

[0049] S200 . When the inverter is in an off-grid control mode, obtain a real-time output voltage and a real-time output current of the AC output port 140 of the inverter.

[0050] The real-time output voltage and real-time output current of the AC output port 140 of the inverter 100 can be obtained by sampling the voltage and current of the AC output port 140 of the inverter 100. The control circuit 120 can be provided with a sampling circuit for sampling the voltage and current of the AC output port 140 of the inverter 100.

[0051] The real-time output voltage is the voltage that the inverter circuit 110 outputs to the AC output port 140 in real time, and the real-time output current is the current that the inverter circuit 110 outputs in real time.

[0052] S300 , generating a first reference current instruction according to the real-time output voltage and the reference output voltage.

[0053] The reference output voltage can be set according to the safety voltage regulations of the AC power grid in different regions and countries. For example, when the effective value of the voltage of the AC power grid is 220V, the reference output voltage can be set to 311V.

[0054] S400 , generating a driving signal according to a first reference current instruction and a real-time output current.

[0055] The driving signal is used to drive the AC output port 140 of the inverter 100 to output a reference output voltage to supply power to the load 30 .

[0056] It can be understood that the driving signal can be used as a signal to control the on-off of each switch tube in the inverter circuit 110, and the output voltage of the AC output port 140 is regulated by controlling the on-off of each switch tube.

[0057] The first reference current instruction at the switching moment when the inverter 100 switches to the off-grid control mode is the first reference current instruction at the previous moment when the inverter 100 switches to the off-grid control mode. It can be understood that the switching moment of the inverter 100 is the initial moment when the inverter 100 is in the off-grid control mode, and the previous moment is the last moment when the inverter 100 is in the grid-connected control mode.

[0058] Therefore, in the control method of the embodiment of the present application, when the power grid 40 is in an abnormal state, the inverter 100 is controlled to switch from the grid-connected control mode to the off-grid control mode, the real-time output voltage and the real-time output current of the AC output port 140 of the inverter 100 are obtained, and a first reference current instruction is generated according to the real-time output voltage and the reference output voltage. A drive signal is generated according to the first reference current instruction and the real-time output current to drive the AC output port 140 of the inverter 100 to output the reference output voltage to power the load 30, thereby achieving stable control of the inverter 100 in the off-grid control mode and ensuring the steady-state performance of the inverter 100 in the off-grid control mode. At the initial moment when the inverter 100 switches from the grid-connected control mode to the off-grid control mode, the first reference current instruction used is the first reference current instruction at the moment before the inverter 100 switches to the off-grid control mode, that is, the first reference current instruction at the last moment when the inverter 100 is in the grid-connected control mode. By using the first reference current instruction and the real-time output current to generate a drive signal, the drive signal can make the voltage output by the inverter 100 at the initial moment of the off-grid control mode the same as the voltage output by the power grid 40 to the grid-connected port 150 at the last moment, that is, the inverter 100 is The voltage output by the inverter 100 at the initial moment of the off-grid control mode is the same as the voltage output to the grid-connected port 150 before the grid 40 becomes abnormal. Then, when the grid 40 is in an abnormal state, the inverter 100 is quickly switched to supply power to the load 30. In the process of switching from the grid-connected state to the off-grid state, the inverter 100 quickly supplies power to the load 30 at the same voltage as the grid 40, which can effectively prevent the load 30 from losing power during the power supply switching, shorten the dynamic adjustment process of the inverter 100 switching from the grid-connected control mode to the off-grid control mode, and enable the inverter 100 to enter the off-grid stable state faster.

[0059] Therefore, the control method of the embodiment of the present application can achieve rapid on-grid and off-grid switching of the inverter 100 without affecting the steady-state performance of the inverter 100.

[0060] It is understandable that after the initial moment of the off-grid control mode, the control circuit 120 executes steps S100 to S400 to control the inverter 100 to continuously output voltage to power the load 30 .

[0061] See also Figure 4 , Figure 4 for Figure 3 The detailed flow chart of step S300 in FIG. Figure 4 As shown, in some embodiments, step S300 may include:

[0062] S310 , obtaining a voltage deviation value according to the real-time output voltage and the reference output voltage.

[0063] In step S310, the real-time output voltage and the reference output voltage may be input into a subtractor, and the voltage deviation value may be calculated and output by the subtractor. Specifically, the voltage deviation value may be obtained by subtracting the real-time output voltage from the reference output voltage.

[0064] S320, performing deviation adjustment on the voltage deviation value to obtain a first reference current instruction.

[0065] Deviation regulation may refer to proportional-integral regulation or proportional regulation. Specifically, the voltage deviation value may be input into a proportional-integral regulator, and the proportional-integral regulator performs proportional-integral regulation to obtain a first reference current instruction.

[0066] See also Figure 5 , Figure 5 for Figure 3 The detailed flow chart of step S400 in FIG. Figure 5 As shown, in some embodiments, step S400 may include:

[0067] S410 , generating a real-time current instruction according to the real-time output current.

[0068] The control circuit 120 may perform Clark transformation and Park transformation on the real-time output current to obtain the real-time current instruction.

[0069] Specifically, the real-time current instruction may include a first real-time instruction and a second real-time instruction. The control circuit 120 obtains the first real-time instruction and the second real-time instruction by performing Clark transformation and Park transformation on the real-time output current of the inverter 100. The first real-time instruction is the direct-axis feedback current I d , the second real-time instruction is the quadrature-axis feedback current I of the inverter 100 qWhen the inverter 100 is a three-phase inverter 100, the real-time output current is the three-phase output current of the inverter 100, and the three-phase output current is subjected to Clark transformation and Park transformation to obtain the first real-time instruction and the second real-time instruction. It can be understood that when the inverter 100 is a single-phase inverter 100, the single-phase output current of the inverter 100 can be subjected to phase-locked processing using a phase-locked loop to obtain a current orthogonal to the single-phase output current, and then the single-phase output current and the orthogonal current obtained by the phase-locked processing are subjected to Clark transformation and Park transformation to obtain the first real-time instruction and the second real-time instruction.

[0070] S420. Obtain a current deviation value according to the first reference current instruction and the real-time current instruction.

[0071] Specifically, the first reference current instruction may be a direct-axis reference instruction of the inverter 100, and the control parameters of the inverter 100 may also include a second reference current instruction, and the second reference current instruction is a quadrature-axis reference instruction of the inverter 100. Correspondingly, the current deviation value may include a first current deviation value and a second current deviation value. The control circuit 120 obtains the first current deviation value according to the first reference current instruction and the first real-time instruction, and obtains the second current deviation value according to the second reference current instruction and the second real-time instruction. Among them, a parameter comparison table of the second reference current instruction of the inverter 100 can be obtained by performing relevant tests on the inverter 100 in advance, and a suitable value is found in the parameter comparison table as the current second reference current instruction according to the current demand of the inverter 100. In some specific examples, the quadrature-axis reference instruction of the inverter 100 can be set to zero.

[0072] It can be understood that the first reference current instruction and the first real-time instruction can be input into a subtractor to obtain the first current deviation value, and the second reference current instruction and the second real-time instruction can be input into another subtractor to obtain the second current deviation value. Specifically, the first reference current instruction is subtracted from the first real-time instruction to obtain the first current deviation value, and the second reference current instruction is subtracted from the second real-time instruction to obtain the second current deviation value.

[0073] S430 , generating a driving signal according to the current deviation value.

[0074] In some embodiments, Figure 6 As shown, step S430 may include:

[0075] S431. Perform deviation adjustment on the first current deviation value to obtain a first voltage value.

[0076] The first current deviation value can be input into a proportional integral regulator, and the proportional integral regulator performs proportional integral regulation to obtain a first voltage value. It can be understood that the first voltage value is the direct axis voltage U of the inverter 100. d .

[0077] S432: Adjust and control the second current deviation value to obtain a second voltage value.

[0078] The second current deviation value can be input into a proportional integral regulator, and the proportional integral regulator performs proportional integral regulation to obtain a second voltage value. It can be understood that the second voltage value is the quadrature axis voltage U of the inverter 100. q .

[0079] S433, obtaining a driving signal according to the first voltage value and the second voltage value.

[0080] The control circuit 120 can perform sinusoidal pulse width modulation (SPWM) on the first voltage value and the second voltage value to generate a drive signal, and the drive signal can be a PWM signal. It can be understood that the control circuit 120 generates a drive signal with a specific duty cycle through the first voltage value and the second voltage value, and the drive signal is used to control the on and off of the upper switch tube and the lower switch tube of each bridge arm of the inverter 100, so that the inverter 100 supplies power to the load 30.

[0081] In some embodiments, the inverter 100 can also operate in a grid-connected control mode. Figure 7 , Figure 7 FIG. 1 is a flow chart of a control method for the inverter 100 in a grid-connected control mode. Figure 7 As shown, the control method may also include:

[0082] S710: When the inverter is in a grid-connected control mode, obtain a real-time input voltage and a real-time output current of an input port of the inverter.

[0083] The real-time input voltage of the inverter 100 can be obtained by sampling the voltage of the input port 130 of the inverter 100 , and the real-time output current can be obtained by sampling the current of the AC output port 140 of the inverter 100 .

[0084] S720: Generate a first reference current instruction according to the real-time input voltage and the reference input voltage.

[0085] Similar to the generation of the first reference current instruction in step S300, the real-time input voltage and the reference input voltage can be input into a subtractor to obtain a voltage deviation value, and the voltage deviation value can be input into a proportional integral regulator for deviation adjustment to obtain the first reference current instruction. For details, please refer to the aforementioned Figure 4 The relevant description of obtaining the first reference current instruction in the steps shown will not be repeated here.

[0086] S730 , generating a driving signal according to the first reference current instruction and the real-time output current, wherein the driving signal is used to control the voltage of the input port 130 of the inverter 100 to be stable at the reference input voltage.

[0087] Similar to the generation of the drive signal in step S400, a real-time current instruction may be generated according to the real-time output current, a current deviation value may be obtained according to the first reference current instruction and the real-time current instruction, and then a drive signal may be generated according to the current deviation value. It is understood that at this time, the inverter 100 may also include a second reference current instruction, and the real-time current instruction may include two real-time instructions, and two current deviation values ​​may be obtained according to the two reference current instructions and the two real-time instructions, respectively, and then the two current deviation values ​​are respectively adjusted to obtain two voltage values, and then a drive signal is obtained according to the two voltage values. For details, please refer to the aforementioned Figure 6 The description of generating the driving signal in the steps shown will not be repeated here.

[0088] When the inverter 100 is in the grid-connected control mode, the load 30 is powered by the grid 40. By generating a first reference current instruction according to the real-time input voltage and the reference input voltage of the inverter 100, and then generating a drive signal according to the first reference current instruction and the real-time output current, the voltage of the input port 130 of the inverter 100 is maintained stable, that is, the voltage of the positive DC bus and the negative DC bus of the inverter 100 is maintained stable. At this time, the inverter 100 only controls the on and off of the upper switch tube and the lower switch tube of each bridge arm in the inverter circuit 110 according to the drive signal. Whether the inverter 100 converts the DC power of the DC power supply 20 into AC power output, or rectifies the AC power of the grid 40 into DC power and provides it to the DC power supply 20, is determined according to the requirements of the load 30 or the requirements of the DC power supply 20.

[0089] In some embodiments, Figure 8 As shown, the control method may also include:

[0090] S810. In response to the power grid returning to a normal state, obtain voltage information of the power grid.

[0091] The control circuit 120 can always keep detecting the state of the power grid 40. When the control circuit 120 detects that the effective value of the voltage of the power grid 40 in a power frequency cycle is greater than a preset threshold, it can determine that the power grid 40 has returned to a normal state. When it is detected that the power grid 40 has returned to a normal state, the control circuit 120 obtains the voltage information of the power grid 40. The voltage information of the power grid 40 may include the voltage, frequency, phase, etc. of the power grid 40.

[0092] S820: Pre-synchronize the voltage at the output end of the inverter with the grid according to the voltage information, so that the voltage at the output end of the inverter is synchronized with the voltage of the grid.

[0093] The control circuit 120 performs pre-synchronization processing on the voltage of the AC output port 140 of the inverter 100 and the grid 40 according to the voltage information of the grid 40 , so that the magnitude and phase of the output voltage of the inverter 100 are synchronized with the voltage of the grid 40 .

[0094] S830, controlling the inverter to switch from an off-grid control mode to a grid-connected control mode.

[0095] It is understood that step S830 may include: controlling the first relay K1 to remain in the on state, and controlling the second relay K2 to be turned on. Since the control circuit 120 has controlled the output voltage of the inverter 100 to be synchronized with the voltage of the grid 40 in step S820, it is possible to prevent the output voltage of the inverter 100 from fluctuating when switching from the off-grid control mode to the grid-connected control mode.

[0096] In some embodiments, the first reference current instruction used when the inverter 100 switches from the off-grid control mode to the grid-connected control mode may be the first reference current instruction at the previous moment, that is, the first reference current instruction at the last moment when the inverter 100 is in the off-grid control mode.

[0097] It should be noted that, for the aforementioned method embodiments, for the sake of simplicity of description, they are all expressed as a series of action combinations, but those skilled in the art should know that the present application is not limited by the described order of actions, because according to the present application, certain steps can be performed in other orders or simultaneously.

[0098] See also Fig. 9 , Fig. 9 FIG. 2 shows a specific control block diagram of the control method of the inverter in the embodiment of the present application. Fig. 9 As shown, in this embodiment, the output of the inverter 100 is controlled mainly through the interaction of the first voltage control loop, the second voltage control loop and the current control loop. When the inverter 100 is in the off-grid control mode, the output of the inverter 100 is jointly controlled by the first voltage control loop and the current control loop. When the inverter 100 is in the grid-connected control mode, the output of the inverter 100 is jointly controlled by the second voltage control loop and the current control loop.

[0099] Specifically, the first voltage control loop includes a first subtractor 121 and a first PI (Proportional Integral) controller 122. The second voltage control loop includes a second subtractor 123 and a second PI controller 124. The current control loop includes a state selector 125, a third subtractor 126, a third PI controller 127, a fourth subtractor 128, a fourth PI controller 129 and a pulse width modulator 130. The control method for the inverter 100 can be implemented by using the first voltage control loop, the second voltage control loop and the current control loop to perform together. Figure 2 The specific circuit topology diagram and Fig. 9 The specific control block diagram shown illustrates the specific working process of the control method of the inverter provided in the embodiment of the present application:

[0100] When the inverter 100 switches from the grid-connected control mode to the off-grid control mode, the second PI controller 124 converts the direct axis reference instruction I dref (i.e., the first reference current command output by the second PI controller 124 at the last moment of the grid-connected control mode) is sent to the first PI controller 122, and the first PI controller 122 uses the direct axis reference command I dref The direct axis reference command (first reference current command) is sent to the state selector 125 at this time, and the state selector 125 selects the direct axis reference command I output by the first PI controller 122. dref Sent to the third subtractor 126.

[0101] The third subtractor 126 converts the direct axis reference command (first reference current command) I dref and direct-axis feedback current (first real-time instruction) I d The first current deviation value is input to the third PI controller 127, and the third PI controller 127 performs proportional-integral regulation on the first current deviation value to obtain a direct-axis voltage (first voltage value) U d .

[0102] The fourth subtractor 128 obtains the quadrature axis reference command (second reference current command) I by looking up the table. qref and quadrature-axis feedback current (second real-time instruction) I q The second current deviation value is input to the fourth PI controller 129, and the fourth PI controller 129 performs proportional-integral regulation on the second current deviation value to obtain the quadrature-axis voltage (second voltage value) U q Among them, the direct-axis feedback current (first real-time instruction) I qref and quadrature-axis feedback current (second real-time instruction) I qIt is obtained by performing Clark transformation and Park transformation on the real-time output current of the inverter 100 .

[0103] The pulse width modulator 130 is used to adjust the direct axis voltage (first voltage value) U d and the quadrature axis voltage (second voltage value) U q The drive signal is modulated to control the on / off of each upper switch tube and lower switch tube in the first bridge arm 111, the second bridge arm 112 and the third bridge arm 113 of the inverter 100, so that the output voltage of the inverter 100 is the same as the voltage of the power grid 40, and the inverter 100 is quickly switched from the grid-connected control mode to the off-grid control mode.

[0104] Then, the inverter 100 operates in the off-grid control mode, and the first subtractor 121 converts the reference output voltage Vac of the inverter 100 into ref The voltage deviation value is obtained by subtracting the obtained real-time output voltage Vac, and the first PI controller 122 performs deviation adjustment on the voltage deviation value to obtain the direct axis reference instruction (first reference current instruction) I at this time. dref The state selector 125 converts the direct axis reference command I output by the first PI controller 122 into dref The third subtractor 126 generates the direct axis reference command (first reference current command) I dref and direct-axis feedback current (first real-time instruction) I d The first current deviation value is input to the third PI controller 127, and the third PI controller 127 performs proportional-integral regulation on the first current deviation value to obtain a direct-axis voltage (first voltage value) U d The steps performed by the fourth subtractor 128, the fourth PI controller 129 and the pulse width modulator 130 are the same as those described above and will not be further described herein.

[0105] That is, at the initial moment when the inverter 100 is switched from the grid-connected control mode to the off-grid control mode, the direct axis reference command (first reference current command) I dref is the direct axis reference command output by the second PI controller 124 at the previous moment. dref Both are generated according to the difference between the reference output voltage and the real-time output voltage of the inverter 100 .

[0106] When the inverter 100 is in the grid-connected control mode, the second subtractor 123 converts the reference input voltage Vdc of the inverter 100 into refThe voltage deviation value is obtained by subtracting the real-time input voltage Vdc. The second PI controller 124 performs deviation adjustment on the voltage deviation value to obtain a direct axis reference command (first reference current command) I dref The state selector 125 converts the direct axis reference command I output by the second PI controller 124 into dref The steps performed by the third subtractor 126, the third PI controller 127, the fourth subtractor 128, the fourth PI controller 129 and the pulse width modulator 130 are the same as those when the inverter 100 is in the off-grid control mode, and are not further described here.

[0107] In this example, the state selector 125 selects the output value of the first PI controller 122 or the output value of the second PI controller 124 according to the state of the inverter 100 to output to the third subtractor 126 .

[0108] Understandably, Fig. 9 The first subtractor 121, the first PI controller 122, the second subtractor 123, the second PI controller 124, the state selector 125, the third subtractor 126, the third PI controller 127, the fourth subtractor 128, the fourth PI controller 129 and the pulse width modulator 130 in the control block diagram shown can be integrated in the control circuit 120.

[0109] See also Fig.10 The embodiment of the present application also provides an energy storage system 10, including an inverter 100 and an energy storage battery 200. The inverter 100 includes an inverter circuit 110 and a control circuit 120. The input end of the inverter circuit 110 is connected to the energy storage battery 200 through the input port 130 of the inverter 100. The output end of the inverter circuit 110 is connected to the load 30 through the AC output port 140 of the inverter 100. The output end of the inverter circuit 110 is also connected to the grid 40 through the grid-connected port 150 of the inverter 100. The load 30 is powered by the inverter 100 and / or the grid 40.

[0110] When the inverter 100 switches from the grid-connected control mode to the off-grid control mode, the control circuit 120 is used to use the first reference current instruction at the previous moment as the first reference current instruction at the current moment, and the control circuit 120 then obtains the real-time output current of the inverter circuit 110, and generates a drive signal according to the real-time output current and the first reference current instruction. The drive signal is used to drive the inverter circuit 110 to output the same voltage as the grid-connected port 150 at the previous moment.

[0111] It can be understood that the beneficial effects and specific implementation methods that can be achieved by the energy storage system 10 provided in the embodiment of the present application can refer to the beneficial effects of the corresponding inverter 100 and its control method provided above, and will not be repeated here.

[0112] The present application also provides a computer-readable storage medium on which a computer program is stored. When the computer program is executed by a processor, the control method as described above is implemented.

[0113] The processor may be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor may be a microprocessor or the processor may be any conventional processor, etc.

[0114] The memory can be used to store computer programs and / or modules. The processor implements various functions of the inverter device 10 by running or acquiring computer programs and / or modules stored in the memory, and calling data stored in the memory. The memory can mainly include a program storage area and a data storage area, wherein the program storage area can store an operating system, an application required for at least one function (such as a power on / off function, a key processing function, etc.), etc.; the data storage area can store data created according to the use of the inverter device 10, etc. In addition, the memory can include a non-volatile memory, such as a hard disk, a memory, a plug-in hard disk, a smart memory card (Smart Media Card, SMC), a secure digital (Secure Digital, SD) card, a flash card (Flash Card), at least one disk storage device, a flash memory device, or other non-volatile solid-state storage devices.

[0115] The memory may be an external memory and / or an internal memory of the inverter device 10 and / or the control circuit 120. Furthermore, the memory may be a memory in a physical form, such as a memory stick, a TF card (Trans-flash Card), and the like.

[0116] If the program code and various data in the memory are implemented in the form of software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the present application implements all or part of the processes in the above-mentioned embodiment method, such as the control method of the inverter, and can also be completed by instructing the relevant hardware through a computer program. The computer program can be stored in a computer-readable storage medium. When the computer program is executed by the processor, the steps of the above-mentioned method embodiments can be implemented. Among them, the computer program includes computer program code, and the computer program code can be in source code form, object code form, executable file or some intermediate form, etc. Computer-readable media may include: any entity or device capable of carrying computer program code, recording medium, U disk, mobile hard disk, disk, optical disk, computer memory, read-only memory (ROM, Read-Only Memory), etc.

[0117] The embodiments of the present application are described in detail above in conjunction with the accompanying drawings, but the present application is not limited to the above embodiments, and various changes can be made within the knowledge scope of ordinary technicians in the relevant technical field without departing from the purpose of the present application.

Claims

1. A control method for an inverter, wherein the input port of the inverter is used to connect a DC power supply, the AC output port of the inverter is used to connect a load, the grid-connected port of the inverter is used for a power grid, and the load is powered by the inverter and / or the power grid; characterized in that: The control method comprises: In response to the power grid being in an abnormal state, controlling the inverter to switch from a grid-connected control mode to an off-grid control mode; When the inverter is in the off-grid control mode, obtaining the real-time output voltage and the real-time output current of the AC output port; Generate a first reference current instruction according to the real-time output voltage and the reference output voltage; generating a driving signal according to the first reference current instruction and the real-time output current, wherein the driving signal is used to drive the AC output port of the inverter to output the reference output voltage to supply power to the load; The first reference current instruction at the switching moment when the inverter switches to the off-grid control mode is the first reference current instruction at a previous moment when the inverter switches to the off-grid control mode.

2. The control method according to claim 1, characterized in that: The step of generating a first reference current instruction according to the real-time output voltage and the reference output voltage comprises: Obtaining a voltage deviation value according to the real-time output voltage and the reference output voltage; The voltage deviation value is deviation-adjusted to obtain the first reference current instruction.

3. The control method according to claim 1 or 2, characterized in that: The generating a driving signal according to the first reference current instruction and the real-time output current comprises: generating a real-time current instruction according to the real-time output current; Obtaining a current deviation value according to the first reference current instruction and the real-time current instruction; The driving signal is generated according to the current deviation value.

4. The control method according to claim 3, characterized in that: The real-time current instruction includes a first real-time instruction and a second real-time instruction; and generating the real-time current instruction according to the real-time output current includes: generating the first real-time instruction and the second real-time instruction according to the real-time output current; Correspondingly, obtaining the current deviation value according to the first reference current instruction and the real-time current instruction includes: Obtaining a first current deviation value according to the first reference current instruction and the first real-time instruction; Obtaining the second current deviation value according to a second reference current instruction and the second real-time instruction; The step of generating the driving signal according to the current deviation value comprises: performing deviation adjustment on the first current deviation value to obtain a first voltage value; Adjusting and controlling the second current deviation value to obtain a second voltage value; The driving signal is obtained according to the first voltage value and the second voltage value.

5. The control method according to claim 1, characterized in that: The inverter comprises an inverter circuit, the output end of the inverter circuit is connected to the grid-connected port via a first relay and a second relay connected in series, and the output end of the inverter circuit is connected to the AC output port via the first relay; The controlling the inverter to switch from a grid-connected control mode to an off-grid control mode includes: The first relay is controlled to maintain a conducting state, and the second relay is controlled to be disconnected.

6. The control method according to claim 1, characterized in that: The control method further comprises: When the inverter is in a grid-connected control mode, obtaining a real-time input voltage and a real-time output current of an input port of the inverter; Generate the first reference current instruction according to the real-time input voltage and the reference input voltage; A drive signal is generated according to the first reference current instruction and the real-time output current, and the drive signal is used to control the voltage of the input port of the inverter to be stable at the reference input voltage.

7. The control method according to claim 6, characterized in that: The control method further comprises: In response to the power grid returning to a normal state, acquiring voltage information of the power grid; Pre-synchronizing the voltage of the AC output port of the inverter with the power grid according to the voltage information, so that the voltage of the AC output port of the inverter is synchronized with the voltage of the power grid; The inverter is controlled to switch from the off-grid control mode to the grid-connected control mode.

8. An inverter, comprising an inverter circuit and a control circuit, wherein the input end of the inverter circuit is connected to a DC power supply through an input port of the inverter, the output end of the inverter circuit is connected to a load through an AC output port of the inverter, the output end of the inverter circuit is also connected to a power grid through a grid-connected port of the inverter, and the load is powered by the inverter and / or the power grid; characterized in that: The control circuit is used for: When the inverter switches from the grid-connected control mode to the off-grid control mode, the first reference current instruction at the previous moment is used as the first reference current instruction at the current moment; The real-time output current of the inverter circuit is obtained, and a drive signal is generated according to the real-time output current and the first reference current instruction, wherein the drive signal is used to drive the inverter circuit to output the same voltage as the grid-connected port at the previous moment.

9. The inverter according to claim 8, characterized in that: The output end of the inverter circuit is connected to the grid-connected port through a first relay and a second relay connected in series, and the output end of the inverter circuit is connected to the AC output port through the first relay; the control circuit is also used for: The first relay is controlled to remain in an on state, and the second relay is controlled to be disconnected, so as to control the inverter to switch from the grid-connected control mode to the off-grid control mode.

10. An energy storage system, characterized in that: The energy storage system includes an energy storage battery and an inverter. The inverter includes an inverter circuit and a control circuit. The input end of the inverter circuit is connected to the energy storage battery through the input port of the inverter. The output end of the inverter circuit is connected to the load through the AC output port of the inverter. The output end of the inverter circuit is also connected to the grid through the grid-connected port of the inverter. The load is powered by the inverter and / or the grid. The control circuit is used for: When the inverter switches from the grid-connected control mode to the off-grid control mode, the first reference current instruction at the previous moment is used as the first reference current instruction at the current moment; The real-time output current of the inverter circuit is obtained, and a drive signal is generated according to the real-time output current and the first reference current instruction, wherein the drive signal is used to drive the inverter circuit to output the same voltage as the grid-connected port at the previous moment.

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