Control method of inverter circuit, power conversion device, and energy storage device

Abstract

This application provides a control method for an inverter circuit, a power conversion device, and an energy storage device. The method includes: when the load is a current-impact load to be started, controlling the actual output voltage of the AC terminal of the inverter circuit to increase from a first voltage to a rated output voltage in stages; wherein, in the first stage, controlling the actual output voltage to increase from the first voltage to a second voltage, the second voltage being greater than or equal to the lower limit of the inverter circuit's output voltage; in the second stage, controlling the actual output voltage to remain at the second voltage, the start time of the second stage being the end time of the first stage; the end time of the second stage being later than the time when the inverter circuit's output torque increases to its maximum torque; and in the third stage, controlling the actual output voltage to increase from the second voltage to the rated output voltage, the start time of the third stage being the end time of the second stage. The control method for the inverter circuit provided by this application can effectively suppress the inrush current during startup.

Description

Technical Field

[0001] This application relates to the field of power electronics technology, and in particular to a control method for an inverter circuit, a power conversion device, and an energy storage device. Background Technology

[0002] In related technologies, when the AC terminal of the inverter circuit is connected to a current-impact load, such as a large motor, air compressor, or power tool, the inverter circuit may stop working due to the overcurrent protection triggered by the starting inrush current, which in turn causes the load to fail to start. Summary of the Invention

[0003] In view of this, this application provides a control method for an inverter circuit, a power conversion device, and an energy storage device, which can meet the starting control requirements of current-impact loads and effectively suppress the inrush current during startup, thereby reducing the probability of the inverter circuit shutting down due to the current-impact load and causing the current-impact load to fail to start.

[0004] The first aspect of this application provides a control method for an inverter circuit, wherein the AC terminal of the inverter circuit is used to connect a load. The method includes: when the load is a current-impact load to be started, controlling the actual output voltage of the AC terminal of the inverter circuit to increase from a first voltage to a rated output voltage in stages; wherein, in the first stage, controlling the actual output voltage of the AC terminal of the inverter circuit to increase from the first voltage to a second voltage, wherein the second voltage is greater than or equal to a lower limit value of the output voltage of the inverter circuit; controlling the actual output voltage to remain at the second voltage in the second stage, wherein the start time of the second stage is the end time of the first stage; the end time of the second stage is later than the time when the output torque of the inverter circuit increases to the maximum torque; and controlling the actual output voltage to increase from the second voltage to the rated output voltage in a third stage, wherein the start time of the third stage is the end time of the second stage.

[0005] In one embodiment, before the step of controlling the actual output voltage of the AC terminal of the inverter circuit to increase from the first voltage to the second voltage in the first stage, the method further includes: obtaining the rated output power of the load and the rated output power of the inverter circuit; the step of controlling the actual output voltage of the AC terminal of the inverter circuit to increase from the first voltage to the second voltage in the first stage includes: when the rated output power of the load and the rated output power of the inverter circuit meet a first condition, simultaneously increasing the output constant voltage of the inverter circuit from the first voltage to the second voltage in the first stage while gradually increasing the frequency of the actual output voltage from the first frequency to the rated frequency; the first condition is the rated output power of the load. The deviation between the rated output power of the load and the rated output power of the inverter circuit is within a preset deviation range; and / or when the rated output power of the load and the rated output power of the inverter circuit meet the second condition, the output constant voltage of the inverter circuit is increased from the first voltage to the second voltage in the first stage; and / or when the relationship between the rated output power of the load and the rated output power of the inverter circuit does not meet the first and second conditions, the output voltage of the inverter voltage is increased from the first voltage to the second voltage in the first stage, or the output voltage of the inverter voltage is increased from the first voltage to the second voltage in the first stage while the frequency of the actual output voltage is gradually increased from the first frequency to the rated frequency.

[0006] In one embodiment, the method further includes: when the rated output power of the load and the rated output power of the inverter circuit satisfy a second condition, controlling the frequency of the actual output voltage of the inverter circuit to be the rated frequency.

[0007] In one embodiment, the duration of the first stage is less than the undervoltage protection trigger duration of the inverter circuit.

[0008] In one embodiment, before the actual output voltage of the AC terminal of the control inverter circuit is increased from a first voltage to a rated output voltage in stages, the method further includes: obtaining a start command, obtaining the type of load according to the start command; the type of load includes a current inrush load; and / or confirming that the load is a current inrush load when the absolute value of the actual output current at the AC terminal is greater than or equal to a preset current threshold.

[0009] In one embodiment, controlling the output voltage of the AC terminal of the inverter circuit to be increased from a first voltage to a rated output voltage in stages includes: acquiring the rated output voltage and rated frequency of the AC terminal; determining a corresponding voltage adjustment coefficient according to a preset first functional relationship, wherein the voltage adjustment coefficient is less than or equal to 1 and greater than 0; determining a reference voltage amplitude according to the voltage adjustment coefficient and the rated output voltage; determining an output voltage reference value according to the reference voltage amplitude and the rated frequency; adjusting the voltage deviation between the output voltage reference value and the actual output voltage to generate a control signal and output it to the inverter circuit, wherein the control signal is used to control the output voltage of the AC terminal to be increased from the first voltage to the rated output voltage in stages.

[0010] In one embodiment, controlling the output voltage of the AC terminal of the inverter circuit to be increased from a first voltage to a rated output voltage in stages includes: acquiring the rated output voltage and rated frequency of the AC terminal; determining the corresponding voltage adjustment coefficient and frequency adjustment coefficient according to a preset first functional relationship and a second functional relationship, respectively, wherein the voltage adjustment coefficient is less than or equal to 1 and greater than 0; the frequency adjustment coefficient is less than or equal to 1 and greater than 0; determining a reference voltage amplitude according to the voltage adjustment coefficient and the rated output voltage; determining a reference frequency according to the frequency adjustment coefficient and the rated frequency; determining an output voltage reference value according to the reference voltage amplitude and the reference frequency; adjusting the voltage deviation between the output voltage reference value and the actual output voltage to generate a control signal and output it to the inverter circuit, the control signal being used to control the output voltage of the AC terminal to be increased from the first voltage to the rated output voltage in stages.

[0011] In one embodiment, adjusting the voltage deviation between the output voltage reference value and the actual output voltage to generate a control signal and output it to the inverter circuit includes: adjusting the voltage deviation between the output voltage reference value and the actual output voltage to obtain an initial output voltage value; adjusting the current deviation between the absolute value of the actual output current and a preset current threshold to obtain a voltage adjustment amount, wherein the polarity of the voltage adjustment amount is the same as the polarity of the actual output current; determining a target output voltage based on the voltage adjustment amount and the initial output voltage value; and generating a control signal based on the target output voltage and outputting it to the inverter circuit.

[0012] A second aspect of this application provides a power conversion device, including an inverter circuit and a controller. The AC terminal of the inverter circuit is used to connect a load; the controller is used to execute the control method of the inverter circuit as described in any of the preceding claims.

[0013] A third aspect of this application provides an energy storage device, including an energy storage battery and a power conversion device as described above. The energy storage battery is connected to the DC terminal of the inverter circuit of the power conversion device.

[0014] The inverter circuit control method provided in this application, when the load to be started is a current-impact type load, controls the actual output voltage of the inverter circuit's AC terminal to be increased from a first voltage to the rated output voltage in stages. Specifically, in the first stage, the actual output voltage of the AC terminal is controlled to increase from the first voltage to a second voltage, wherein the second voltage is greater than or equal to the lower limit of the inverter circuit's output voltage. That is, in the first stage, by increasing the actual output voltage of the inverter circuit from a lower value, the corresponding output torque is reduced. Since the output torque is proportional to the output current, the output current during startup can be reduced by controlling the voltage to start below a preset voltage threshold. Then, in the second stage, the actual output voltage is controlled to be maintained at the second voltage, wherein the start time of the second stage is the end time of the first stage. Since the second voltage is greater than or equal to the lower limit of the inverter circuit's output voltage, and since there is a positive correlation between the actual output voltage and the output torque, when the actual output voltage of the inverter circuit remains above the output voltage limit during the second stage, sufficient time is provided to maintain the torque within a certain range. Because the end of the second stage is later than the moment the inverter circuit's output torque reaches its maximum, the output torque of the inverter circuit will first change to its maximum torque and then further decrease during the second stage. At this time, the current will also first increase and then gradually decrease, thus ending the inrush current stage. Simultaneously, the load speed will rapidly increase during this process. Then, in the third stage, the actual output voltage is controlled to increase from the second voltage to the rated output voltage. The start time of the third stage is the end time of the second stage. In this way, the upward trend of the load speed can be maintained, allowing the load to enter normal operating conditions after the third stage. In summary, the inverter circuit control method provided in this application increases the output voltage from a first voltage to the rated output voltage in stages. The three stages of increasing the first voltage to the rated output voltage are divided into three corresponding stages: reducing the actual output current, maintaining the motor torque, and increasing the motor speed. This satisfies the motor load starting control requirements, reduces the probability of the inverter circuit stopping due to the starting current impact of the load, and improves the load starting success rate. Attached Figure Description

[0015] To more clearly illustrate the technical solutions of this application, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of this application and should not be considered as a limitation on the scope of protection of this application. In the various drawings, similar components are numbered similarly.

[0016] Figure 1 This is a schematic diagram of the application environment of a power conversion device according to an embodiment of this application.

[0017] Figure 2This is a structural block diagram of a power conversion device in one embodiment of this application.

[0018] Figure 3 A circuit diagram of an inverter circuit provided in one embodiment of this application.

[0019] Figure 4 This is a schematic diagram of the voltage curve of the actual output voltage of the inverter circuit at the AC terminal in one embodiment of the present application, showing the phased increase from the first voltage to the rated output voltage.

[0020] Figure 5 This is a schematic diagram of the equivalent circuit when one of the stator windings of a three-phase motor starts.

[0021] Figure 6 A schematic diagram of the torque-speed curve when the asynchronous motor is started with reduced voltage.

[0022] Figure 7 This is a schematic diagram of a partial step of the control method for an inverter circuit in one embodiment of the present application, prior to the step of controlling the actual output voltage of the AC terminal to increase from a first voltage to a second voltage in the first stage starting at the current moment.

[0023] Figure 8 This is a schematic diagram of the actual output voltage and the frequency of the actual output voltage during the remaining stages of the first stage in one embodiment of this application.

[0024] Figure 9 This application provides, in one embodiment, the torque-speed curves of a motor at different frequencies when the actual output voltage and frequency change remain linear as the frequency of the actual output voltage increases from a first frequency to the rated frequency.

[0025] Figure 10 This is a schematic diagram showing the actual output voltage and the frequency of the actual output voltage during the remaining stages of the first stage, provided for other embodiments of this application.

[0026] Figure 11 This is a schematic diagram illustrating the process of gradually increasing the output voltage of the control AC terminal from a first voltage to the rated output voltage according to an embodiment of this application.

[0027] Figure 12 This is a flowchart illustrating step S114 provided in an embodiment of this application.

[0028] Figure 13 This is a flowchart illustrating step S115 provided in an embodiment of this application.

[0029] Figure 14 This is a flowchart illustrating step S115 as provided in another embodiment of this application.

[0030] Figure 15This is a specific control block diagram of a control method for implementing an inverter circuit, provided as an embodiment of this application.

[0031] Figure 16 A specific control block diagram for implementing a control method for an inverter circuit is provided in another embodiment of this application.

[0032] Figure 17 A block diagram of an energy storage device provided in one embodiment of this application.

[0033] Figure 18 This is a block diagram of a control device provided in one embodiment of this application.

[0034] Figure 19 A functional block diagram of a computer-readable storage medium provided in an embodiment of this application. Detailed Implementation

[0035] The technical solutions of the embodiments of this application will be described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments.

[0036] It should be noted that when a component is considered to be "connected" to another component, it can be directly connected to the other component or may also have an intervening component. When a component is considered to be "placed" on another component, it can be directly placed on the other component or may also have an intervening component.

[0037] It should also be noted that the methods disclosed in the embodiments of this application or the methods shown in the flowcharts include one or more steps for implementing the method. Without departing from the scope of the claims, the execution order of multiple steps can be interchanged, and some steps can also be deleted.

[0038] 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 technical features indicated. Thus, a feature defined with "first" or "second" may explicitly or implicitly include one or more of that feature.

[0039] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0040] Some embodiments will now be described with reference to the accompanying drawings. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0041] In related technologies, when the AC terminal of an inverter circuit is connected to a current-impact load, such as a large motor, air compressor, or power tool, the inverter circuit may stop working due to the overcurrent protection triggered by the starting inrush current, which in turn causes the load to fail to start.

[0042] Therefore, this application provides a control method for an inverter circuit, a power conversion device, and an energy storage device, which can reduce the probability of the inverter circuit shutting down due to the starting current surge load, thus causing the current surge load to fail to start.

[0043] First, please refer to Figure 1 , Figure 1 This is a schematic diagram illustrating the application environment of a power conversion device 10 according to an embodiment of this application. The power conversion device 10 is connected between a DC power supply 20 and a load 30. The power conversion device 10 is used to convert the DC power output from the DC power supply 20 into AC power to supply power to the load 30. The DC power supply 20 can be a photovoltaic module, battery module, energy storage device, or other electronic device used to output DC power; this application does not limit the DC power supply. The load 30 can be a load that requires power. In this embodiment, the load 30 can include a load containing a motor. This type of load generates a large current for a short period during startup; once successfully started and operating normally, the current will quickly drop to the normal range. Specifically, the load 30 can be equipment such as air conditioners, large fans, air compressors, pumps, compressors, and conveyors. This type of equipment can be called a motor-type load or a current-inrush load. This document refers to it as a current-inrush load. This application does not limit the specific equipment included in current-inrush loads.

[0044] In some embodiments, the power conversion device 10 may also supply power to the load 30 via other power conversion devices, and this application does not limit this. In other embodiments, the DC power supply 20 may be an energy storage unit, and the power conversion device 10 and the DC power supply 20 may be integrated into the same device to form an energy storage converter, a mobile energy storage device, or a home energy storage device.

[0045] In some embodiments, the side of the power conversion device 10 connected to the load 30 can also be connected to the power grid to feed power into the grid or to receive power as a grid load.

[0046] Please see Figure 2 , Figure 2 This is a structural block diagram of a power conversion device 10 according to an embodiment of this application. The power conversion device 10 may include a controller 11, a memory 12, and an inverter circuit 13. The controller 11, the memory 12, and the inverter circuit 13 can be connected via a bus, which can be any suitable bus such as an Inter-integrated Circuit (I2C) bus.

[0047] The inverter circuit 13 is used to convert direct current (DC) to alternating current (AC). The inverter circuit 13 can be a single-phase or multi-phase circuit, and this application does not limit this. In some embodiments, when the power conversion device 10 is an energy storage converter, the inverter circuit 13 can be a bidirectional inverter circuit. When the inverter circuit 13 operates in inverter mode, it converts DC to AC; when the inverter circuit 13 operates in rectification mode, it converts AC to DC. The memory 12 can store the operating system and computer programs. The controller 11 provides computing and control capabilities to support the operation of the entire power conversion device 10. The computer program stored in the memory 12 includes program instructions, which, when executed, cause the controller 11 to perform the control method for the inverter circuit provided in this application.

[0048] Please continue reading. Figure 3 Specifically, in one embodiment, the inverter circuit 13 includes switching transistors Q1, Q2, Q3, and Q4, an inductor L1, a capacitor C1, and a capacitor C2. The first terminals of both switching transistors Q1 and Q3 are electrically connected to the positive DC bus BUS+. The second terminal of switching transistor Q1 is electrically connected to the first terminal of switching transistor Q2. The second terminal of switching transistor Q3 is electrically connected to the first terminal of switching transistor Q4. The second terminals of both switching transistors Q2 and Q4 are electrically connected to the negative DC bus BUS-. The controlled terminals of switching transistors Q1, Q2, Q3, and Q4 are all electrically connected to the processor 11 (not shown). The first terminal of inductor L1 is electrically connected between the second terminals of switching transistors Q3 and Q4, and the second terminal of inductor L1 is electrically connected to the positive output terminal OUT+ of the inverter circuit 13. The negative output terminal OUT- of the inverter circuit 13 is electrically connected between the second terminal of switching transistor Q1 and the first terminal of switching transistor Q2. Capacitor C1 is connected between the positive terminal OUT+ and the negative terminal OUT- of the output of inverter circuit 13. Capacitor C2 is connected between the positive DC bus BUS+ and the negative DC bus BUS-. It can be understood that switching transistors Q1, Q2, Q3, and Q4 can be controlled by processor 11, or they can be controlled by multiple processors separately; this invention does not impose any limitations on this.

[0049] Understandably, this application does not limit the specific circuit structure of the inverter circuit 13. Figure 3The following explanation uses a single-phase full-bridge inverter circuit as an example. In other embodiments, inverter circuit 13 can also be other inverter circuits, such as a T-type three-level inverter circuit or other multi-phase inverter circuits. Accordingly, when inverter circuit 13 is a single-phase inverter circuit, it can output single-phase AC power; when inverter circuit 13 is a multi-phase inverter circuit, it can output multi-phase AC power. The specific inverter circuit 13 needs to be matched with the type of load connected. For example, when starting a single-phase motor, a single-phase inverter circuit can be used; when starting a three-phase motor, a three-phase inverter circuit can be used.

[0050] In the following embodiment, the control method of the inverter circuit is applied to Figure 3 The inverter circuit 13 shown is used as an example to illustrate the working principle and process of the control method for the inverter circuit provided in this application. It is worth noting that the control method for the inverter circuit provided in this application can also be applied to other inverter circuits, and this application does not specifically limit the circuit structure to which the control method for the inverter circuit is applied. This application will subsequently use a single-phase inverter circuit as an example for explanation.

[0051] Understandably, the control method for the inverter circuit provided in this application can be executed by the controller 11, or by a controller independent of the power conversion device 10. Please refer to [the relevant documentation / reference]. Figure 4 The control method for the inverter circuit provided in this application includes:

[0052] When the load is a current-impact type load to be started, the actual output voltage of the AC terminal of the control inverter circuit is increased from the first voltage to the rated output voltage in stages.

[0053] Specifically, in the first stage (i.e. Figure 4 During the time period from 0 to T1, the actual output voltage of the AC terminal of the inverter circuit is increased from the first voltage V1 to the second voltage V2. The second voltage V2 is greater than the lower limit of the inverter circuit's output voltage.

[0054] In the second stage (i.e.) Figure 4 During the time period from T1 to T2, the actual output voltage of the control inverter circuit is maintained at the second voltage V2. The start time of the second stage is the end time of the first stage, i.e., time T1. The end time T2 of the second stage is later than the time when the output torque of the inverter circuit increases to the maximum torque.

[0055] In the third stage (i.e.) Figure 4 During the time period from T2 to T3, the actual output voltage of the control inverter circuit is increased from the second voltage V2 to the rated output voltage V3. The start time of the third stage is the end time of the second stage, i.e., time T2.

[0056] "Pending startup" refers to a state where load 30 is connected to power conversion device 10 but has not yet started or is in the startup process but has not yet completed startup. That is, the control strategy of this application can be applied to scenarios where the inverter circuit switches from a load to a current-impact load, and also to scenarios where the inverter circuit is unloaded and needs to start a current-impact load. Understandably, after load 30 is connected to power conversion device 10, power conversion device 10 can output AC power to load 30 through the AC terminal of inverter circuit 13 to supply power to load 30. When the torque provided by the AC power output from the AC terminal of inverter circuit 13 meets the startup requirements of load 30, load 30 can successfully start and enter normal operation. However, the inrush current generated during the startup process of a current-impact load can easily trigger overcurrent protection, causing inverter circuit 13 to stop working, thus leading to load startup failure. Therefore, how to provide torque that meets the startup requirements of a current-impact load while reducing the inrush current becomes the key to whether the inverter circuit can successfully start a current-impact load.

[0057] Please refer to the following: Figures 4 to 6 The following content will be combined Figures 4 to 6 This application explains the working process of the control method for the inverter circuit provided in this application, and the working principle of the control method to enable the load 30 to start successfully.

[0058] First, please refer to Figure 4 , Figure 4 This is a schematic diagram showing the actual output voltage curve of the inverter circuit in the control method mentioned above. Please refer to the following: Figure 5 , Figure 5 This is a schematic diagram of the equivalent circuit of an asynchronous motor during startup. Essentially, starting a motor involves directly supplying the single-phase or three-phase output of the inverter circuit to the motor for starting. If the motor is single-phase, it starts by generating a pulsating magnetic field through the starting winding; if it is three-phase, it starts by generating a rotating magnetic field through the stator winding. Understandably, a three-phase motor has three stator windings, connected to the three phase lines of the AC terminal of a three-phase inverter circuit. In other words, it can be considered... Figure 5 It is a stator winding of a three-phase motor connected to one of the three-phase inverter circuits, such as... Figure 3 The diagram shows the equivalent circuit of the stator winding during startup on the two inverter bridge arms. It can be understood that... Figure 5 This can also be the equivalent circuit for a single-phase asynchronous motor during startup. When the motor is a three-phase asynchronous motor, each phase can be equivalent to... Figure 5 The circuit. In Figure 5In this diagram, R1 and X1 represent the stator resistance and stator inductance, respectively; R2 and X2 represent the rotor resistance and rotor inductance, respectively; Rm and Xm represent the corresponding magnetizing resistance and magnetizing inductance of the stator, respectively; and (1-S) / S*R2 is used to represent the equivalent load.

[0059] Understandably, in Figure 5 In the equivalent circuit diagram shown, when the motor just starts, the speed is zero, S=1, and the load is equivalent to a short circuit. Since no magnetic field is established, Rm and Xm can be ignored. At this time, the starting current is directly proportional to the input voltage and inversely proportional to the stator and rotor parameters of the motor. The calculation formula is as follows:

[0060]

[0061] Among them, I st U represents the starting current of the load; n represents the stator voltage; c represents the coefficient referred from the rotor side to the stator side. From the above formula (1), it can be seen that reducing the motor's input voltage can reduce the starting current. That is, when the load is connected to the inverter circuit 13, the starting current can be reduced by lowering the actual output voltage of the inverter circuit 13. Therefore, in this embodiment, when it is confirmed that the load 30 is a current-impact load to be started, the starting current is initially reduced by raising the actual output voltage of the inverter circuit 13 from the lower first voltage V1 in the first stage starting at the current moment. That is, if the inverter circuit 13 currently has a voltage output, the original voltage output will be adjusted to the first voltage V1 first, and then gradually increased from the first voltage V1 to the second voltage V2.

[0062] Please continue reading. Figure 6 , Figure 6 This is a schematic diagram of the torque-speed curve when an asynchronous motor starts. Figure 6 The graph contains three curves: L61, L62, and L63. L61 shows the relationship between torque Tem and speed n when the stator voltage Un (i.e., the input voltage of the asynchronous motor, or the output voltage of the inverter circuit) is constant. L62 shows the relationship between torque Tem and speed n when the voltage is reduced to 0.8Un. L63 shows the relationship between torque Tem and speed n when the voltage is reduced to 0.5Un. The graphs show that as the input voltage changes, the maximum torque Tm decreases by a square factor relative to the stator voltage Un. Specifically, when the stator voltage Un decreases to 0.8Un, the maximum torque Tm decreases to 0.64Tm; when the stator voltage Un decreases to 0.5Un, the maximum torque Tm decreases to 0.25Tm. The initial torque Tst also follows the same pattern.

[0063] That is, in Figure 6As can be seen from curves L61 to L63, as the stator voltage Un decreases, the maximum torque Tm and the starting torque Tst decrease proportionally to the square of the stator voltage Un, while the critical slip Sm remains unchanged regardless of the stator voltage Un. In other words, by reducing the actual output voltage of the inverter circuit 13 (i.e., the output voltage of the inverter circuit is less than the rated output voltage), the corresponding starting torque can be reduced. Figure 6 Curve L64 in the figure is used to represent the load torque required when the stator winding is in a stable operating state.

[0064] It is understandable that, in the first stage (0-T1), in order for load 30 to start successfully, the initial torque provided by inverter circuit 13 when outputting the first voltage V1 should be greater than or equal to the load torque required for load 30 to be in a stable operating state. In other words, corresponding to... Figure 6 The torque-speed curve shown should have the curve corresponding to the first voltage V1 located to the right of curve L64 to ensure that the first voltage V1 output by inverter circuit 13 can at least meet the starting requirements of the load. In one embodiment, the first voltage V1 can be 0.75 times the rated output voltage of the inverter circuit. In another embodiment, the first voltage V1 is greater than 0.5 times the rated output voltage.

[0065] Therefore, in the control method of the inverter circuit provided in this application, during the first stage 0 to T1, since the first voltage V1 is less than the second voltage V2, and the second voltage V2 is greater than or equal to the lower limit of the output voltage of the inverter circuit, the actual output voltage of the inverter circuit 13 can be increased from a lower value during the first stage 0 to T1, thereby reducing the output torque provided by the inverter circuit 13 during the first stage.

[0066] Furthermore, since motor torque is directly proportional to motor current, for example, the proportional relationship between motor torque and motor current can be expressed by the following formula:

[0067]

[0068] Where Tem is the motor torque, P is the output power, n is the speed, U is the stator voltage (i.e., the actual output voltage), and I is the motor current (i.e., the actual output current).

[0069] Thus, during the first stage (0-T1), the starting current can be reduced by decreasing the output torque. Furthermore, during the first stage (0-T1), although according to... Figure 6 As shown in the torque-speed curve, the starting current continues to increase with the increase of torque, but since the load 30 has already established its speed, the peak current of the motor in the load 30 is effectively suppressed. That is, the first stage 0 to T1 is the stage of reducing the actual output current.

[0070] Next, starting from the end of the first stage (T1), the actual output voltage is maintained at the second voltage (V2) during the second stage (T1-T2). The second voltage (V2) is greater than the lower limit of the inverter circuit's output voltage and less than the inverter circuit's rated output voltage. The lower limit of the output voltage is less than the rated voltage of the load (30V), and both the lower limit of the output voltage and the rated output voltage of the inverter circuit can be determined according to different loads and / or different regional safety regulations. For example, the rated voltage in some regions is 220V, while in others it is 110V. The lower limit of the output voltage also needs to be determined according to the lower limit voltage specified in the region where the inverter circuit is located. For example, in some countries, the lower limit of the output voltage is 85%Ue, where Ue is the rated output voltage of the inverter circuit. Both the rated output voltage and the lower limit of the output voltage can be configured according to the actual scenario.

[0071] This application does not limit the ratio of the lower limit of the output voltage to the rated output voltage of the inverter circuit. Taking an output voltage lower limit of 0.85 times the rated output voltage of inverter circuit 13 as an example, it can be understood that, based on the above formula (1), when the actual output voltage is 0.85Ue, the corresponding maximum torque is approximately 0.7225Tm (i.e., 0.85). 2 Tm). Where Ue is the rated output voltage of the inverter circuit, and Tm is the maximum torque that the inverter circuit can provide when the output voltage is Ue. At this time, from... Figure 6 As can be seen from the curves, such as curves L61 to L63, when the motor torque approaches its maximum torque Tm, it first changes relatively steadily to the maximum torque Tm, and then decreases further from the maximum torque Tm. During this process, the speed increases almost linearly upwards. Therefore, maintaining the actual output voltage at the second voltage V2 within the second stage T1 to T2 provides sufficient time to maintain the output torque within a certain range, thus ensuring a rapid increase in speed. Please refer to the following: Figure 4 and Figure 6 Since the end of the second stage T1-T2 is later than the moment when the output torque of the inverter circuit 13 increases to its maximum torque, maintaining the output voltage at the second voltage V2 during the second stage T1-T2 allows the torque of the load 30 to cross the corresponding maximum torque inflection point and continue its upward speed trend as the load 30's speed increases. Furthermore, after the load 30's torque crosses the corresponding maximum torque, as the speed increases, the motor torque begins to decrease, and the output current of the inverter circuit 13 will first increase and then gradually decrease, thus ending the inrush current stage. In other words, the second stage T1-T2 is the motor torque maintenance stage.

[0072] Starting from the end of the second stage T1-T2, during the third stage T2-T3, the actual output voltage is increased from the second voltage T2 to the rated output voltage, i.e., increased to the third voltage V3. This maintains the upward trend of the load speed and allows the load 30 to enter normal operating condition after the third stage T2-T3. During the third stage T2-T3, the torque gradually decreases until it reaches the load torque, i.e. Figure 6 The torque corresponding to curve L64. That is, the third stage, T2 to T3, is the stage of increasing motor speed.

[0073] In summary, the inverter circuit control method provided in this application divides the process of increasing the output voltage from the first voltage V1 to the rated output voltage, i.e., to the third voltage V3, into three stages. These three stages correspond to reducing the actual output current, maintaining the motor torque, and increasing the motor speed, in order to meet the motor load starting control requirements and effectively suppress the inrush current during startup. This reduces the probability that the inverter circuit 13 will experience overcurrent due to the inrush current impacting the load, thus causing the overcurrent protection to shut down. It can also improve the startup success rate of the current-impacting load.

[0074] It is understood that the specific durations of the first stage 0 to T1, the second stage T1 to T2, and the third stage T2 to T3 in this application can be configured based on different inverter circuits and / or loads. This application does not limit the specific durations of the first stage 0 to T1, the second stage T1 to T2, and the third stage T2 to T3.

[0075] For example, the duration of the first stage can be less than the undervoltage protection trigger duration of inverter circuit 13 and / or greater than the starting current suppression duration of inverter circuit 13. When the duration of the first stage is less than the undervoltage protection trigger duration of inverter circuit 13, the probability of the relay connecting the AC terminal of inverter circuit 13 and the input terminal of load 30 disconnecting due to undervoltage protection triggering can be reduced, ensuring continuous power supply from inverter circuit 13 to load 30. This reduces the probability of frequent start-stop cycles of inverter circuit 13 and improves its stability and reliability. When the duration of the first stage is greater than the starting current suppression duration of inverter circuit 13, since the first stage increases from a lower value to suppress the starting current, the suppression duration of the starting current can be extended beyond triggering overcurrent protection, enhancing the suppression effect. In other words, by increasing the output voltage of the inverter circuit from a lower value in the first stage, the starting torque can be reduced, and by reducing the starting torque, the starting current can be suppressed. The duration of the first phase should not be too long, so as not to affect the power consumption of other loads.

[0076] The second stage has a longer dwell time, exceeding the operating time of certain switches. Therefore, it's necessary to wait for the current rise to finish within the standard voltage range. In other words, the end time of the second stage should be greater than or equal to the time when the inverter circuit's output current begins to decrease. Specifically, the time T2 should be later than the time when the inverter circuit's output current begins to decrease.

[0077] The end time of the third stage T2-T3 is later than the time when the output torque of the inverter circuit drops to the load torque required for the load 30 to reach a stable operating state. In this way, the load 30 can enter the normal operating state after the third stage T2-T3 ends.

[0078] In some embodiments, when the load is a non-current-impact load, the controller 11, after detecting the connection of the load 30, can also execute a preset control strategy based on a preset control loop. The preset control loop may include at least one of a voltage loop, current loop, power loop, combined loop, or other control loops. This application does not limit the specific loop. The preset control loop may include one or more control loops / controllers, such as adders, subtractors, derivative controllers (D), proportional-integral (PI) controllers, proportional-integral-derivative (PI-DI) controllers, limiters, etc., and this application does not limit these. Thus, the inverter circuit control method provided by this application can meet the power supply requirements of various different loads 30.

[0079] However, in practical applications, since the first voltage V1 cannot be too small, if the load torque of the load 30 is large, the actual output voltage may be increased from the first voltage V1, which suppresses the starting current, but the output torque provided by the first voltage V1 is less than the load torque. In this case, the load 30 still cannot start.

[0080] Therefore, please continue reading. Figure 7 In some embodiments, before the step of controlling the actual output voltage of the AC terminal of the inverter circuit to increase from the first voltage to the second voltage in the first stage, the control method of the inverter circuit further includes the following steps S701-S702.

[0081] Step S701: Obtain the rated output power of the load and the rated output power of the inverter circuit.

[0082] The rated output power of a load can be obtained directly through communication with the load, or indirectly by obtaining the load's device type. In other words, the rated output power of the load is determined based on the obtained device type and the mapping relationship between device type and rated output power. The rated output power of the inverter circuit can be pre-stored in the device and can be configured by the user via an app according to the application scenario. The specific method of acquisition does not affect the actual data acquisition.

[0083] Step S702: When the rated output power of the load and the rated output power of the inverter circuit meet the first condition, in the first stage, while increasing the output constant voltage of the inverter circuit from the first voltage V1 to the second voltage V2, the frequency of the actual output voltage is gradually increased from the first frequency to the rated frequency.

[0084] When the deviation between the rated output power of the load and the rated output power of the inverter circuit is within a preset deviation range, the rated output power of the load, i.e., the current-inrush load, can be considered close to the rated output power of the inverter circuit, thus satisfying the first condition mentioned above. In this case, simply reducing the voltage in the first stage may not meet the load's starting requirements. Therefore, a frequency reduction operation needs to be performed simultaneously, that is, gradually increasing the frequency of the actual output voltage from the first frequency to the rated frequency, rather than starting directly at the rated frequency. The first frequency can be the minimum frequency that can meet the load's starting requirements.

[0085] Step S703: When the rated output power of the load and the rated output power of the inverter circuit meet the second condition, the output constant voltage of the inverter circuit is increased from the first voltage V1 to the second voltage V2 in the first stage.

[0086] The second condition can be considered satisfied when the rated output power of the load is less than n times the rated output power of the inverter circuit.

[0087] In this embodiment, n is a number less than 1 and greater than 0. That is, when the deviation between the rated output power of the load and the rated output power of the inverter circuit is large, only a step-down operation in the first stage is needed to meet the load's starting requirements, without the need for a frequency reduction operation. In one embodiment, n can be 0.5, or a number less than 0.5.

[0088] At this time, the frequency of the output voltage of the inverter circuit is the rated frequency. In this way, controlling the actual output voltage frequency of the inverter circuit 13 to be the rated frequency can reduce the switching losses of the inverter circuit 13 and reduce the occupation of computing resources caused by gradual frequency modulation, and improve the conversion efficiency of the inverter circuit 13.

[0089] Step S704: When the relationship between the rated output power of the load and the rated output power of the inverter circuit does not meet the first and second conditions mentioned above, the output voltage of the inverter voltage is increased from the first voltage V1 to the second voltage V2 in the first stage, or the frequency of the actual output voltage is gradually increased from the first frequency to the rated frequency while the output voltage of the inverter voltage is increased from the first voltage V1 to the second voltage V2 in the first stage.

[0090] In other words, when the rated output power of the load is between the first and second conditions, frequency reduction can be selectively performed when bucking the output.

[0091] Specifically, reducing the frequency of the actual output voltage changes the frequency of the stator power supply in load 30, thereby changing the synchronous speed of the stator winding. Simultaneously, the frequency reduction process has minimal impact on the maximum torque and starting torque corresponding to the first voltage V1. Thus, since the actual output voltage remains the first voltage, the theoretical torque corresponding to the first voltage remains almost unchanged, while the starting torque required by the load side decreases significantly due to the reduced speed. Therefore, the initial torque corresponding to the first voltage can now start load 30.

[0092] Please see Figure 8 In some embodiments, as the actual output voltage increases from a first voltage V1 to a second voltage V2, and the frequency of the actual output voltage increases from a first frequency f1 to a rated frequency fe, the changes in the actual output voltage and frequency remain linear, meaning the ratio of the actual output voltage to the frequency is always a constant. In this case, the motor's torque-speed curve is approximately as follows: Figure 9 The change is as follows: As the frequency of the actual output voltage increases, the motor speed rises, while the maximum torque and starting torque remain almost unchanged. Compared to simply increasing the output voltage from the first voltage V1 to the second voltage V2 in the first stage, adding frequency regulation while adjusting the voltage in the first stage provides a stiffer mechanical characteristic and better load-carrying capacity. Simultaneously, it offers high conversion efficiency, no additional losses during speed regulation, a wider speed range, and is more conducive to starting under load.

[0093] In other embodiments, during the implementation of variable frequency and variable voltage speed regulation, the actual output voltage and its frequency can also vary in other patterns and do not necessarily need to remain linear throughout the entire first stage. For example, please refer to... Figure 10 The relationship between the actual output voltage and its frequency, as shown in (a) to (d), can also be... Figure 10 Any of the variations or other variations shown in (a) to (d) are included.

[0094] In some embodiments, before the actual output voltage at the AC terminal of the inverter circuit is gradually increased from a first voltage to the rated output voltage, the method for the inverter circuit further includes:

[0095] Obtain the startup command, and determine the load type based on the startup command; the load type includes current inrush loads; and / or

[0096] When the absolute value of the actual output current at the AC end is greater than or equal to the preset current threshold, the load is confirmed to be a current surge load.

[0097] The start command is used to instruct the inverter circuit 13 to output AC power to supply power to the load 30. The triggering method of the start command can be set according to actual needs. For example, in some embodiments, the start command can be triggered by a start button on the peripheral of the power conversion device 10, and the controller 11 can obtain the start command when the user presses the start button. In other embodiments, the start command can also be sent to the controller 11 by other control devices or a host computer, so that the controller 11 can obtain the start command. In still other embodiments, the power conversion device 10 can trigger the start command and send it to the controller 11 when it detects the connected load 30 at the AC end. Other methods can also be used to trigger the start command in other embodiments, and this application does not limit this approach.

[0098] In some embodiments, after the load 30 is connected to the power conversion device 10, it can communicate with the power conversion device 10 based on a preset communication protocol and generate corresponding connection information. The triggered start command carries this connection information. Thus, after obtaining the start command, the controller 11 can parse the start command to obtain the connection information. The connection information may include at least the type of the load to be started. The type of load can be identified by at least one of the following methods: load icon, load name, preset string, etc. The type of load may include current-inrush loads, non-current-inrush loads, and other types of loads. It is understood that the connection information may also include other information, such as the operating status and quantity of the load, which is not limited in this application. Thus, after obtaining the start command, the type of load can be obtained according to the start command, and when the type of load includes a current-inrush load, the step of controlling the actual output voltage of the AC terminal of the inverter circuit to be increased from the first voltage to the rated output voltage in stages is executed.

[0099] In some embodiments, the AC terminal of the inverter circuit 13 is also provided with a current sampling circuit. Thus, after the load 30 is connected to the power conversion device 10, if the absolute value of the actual output current is detected to be greater than or equal to a preset current threshold, the load can be confirmed as a current-impact load to be started. The actual output current can be obtained by sampling the current at the AC terminal of the inverter circuit 13, or by sampling the current of the inductor L1 at the AC terminal.

[0100] In summary, based on the two methods described above, it is possible to quickly determine whether the load 30 connected to the inverter circuit 13 is a current-impact load to be started. When it is confirmed that the load 30 is a current-impact load to be started, the actual output voltage of the AC terminal of the inverter circuit is increased from the first voltage to the rated output voltage in stages to reduce the inrush current and enable the load 30 to start successfully.

[0101] Please see Figure 11 In some embodiments, the output voltage of the AC terminal of the control inverter circuit is increased from a first voltage to the rated output voltage in stages, including the following steps S111-S116.

[0102] Step S111: Obtain the rated output voltage and rated frequency of the AC terminal.

[0103] The rated output voltage and rated output frequency can be preset values ​​stored in memory 12 or other storage units.

[0104] Step S112: Determine the corresponding voltage adjustment coefficient according to the preset first functional relationship, wherein the voltage adjustment coefficient is less than or equal to 1 and the voltage adjustment coefficient is greater than 0.

[0105] The voltage adjustment coefficient represents the ratio of the actual output voltage to the rated output voltage. The first functional relationship represents the relationship between the voltage adjustment coefficient and the duration of the adjustment phase. Thus, by appropriately setting the first functional relationship, the voltage adjustment coefficient can be made to change according to a first preset rule from the first stage to the third stage.

[0106] Step S113: Determine the reference voltage amplitude based on the voltage adjustment coefficient and the rated output voltage.

[0107] In some embodiments, a voltage adjustment coefficient can be periodically obtained based on a first functional relationship and the duration of the adjustment phase, and the product of the obtained voltage adjustment coefficient and the rated output voltage can be calculated as a reference voltage amplitude. Since the voltage adjustment coefficient changes according to a first preset rule from the first to the third phase, and the reference voltage amplitude is proportional to the voltage adjustment coefficient, the reference voltage amplitude from the first to the third phase can also change according to the first preset rule. The first preset rule can be used to enable the reference voltage amplitude to be increased in stages from the voltage amplitude corresponding to the first voltage to the voltage amplitude corresponding to the rated output voltage from the first to the third phase.

[0108] Step S114: Determine the output voltage reference value based on the reference voltage amplitude and rated frequency.

[0109] In some embodiments, the angular velocity ω can be calculated based on the rated frequency, and then the angular velocity ω can be integrated to obtain the phase θ. The output voltage reference value can then be calculated based on a preset trigonometric function (e.g., sin function or cos function), the reference voltage amplitude, and the phase θ.

[0110] Since the reference voltage amplitude in step S113 needs to be increased from the voltage amplitude corresponding to the first voltage to the voltage amplitude corresponding to the rated output voltage in stages, the output voltage reference value can be increased from the first voltage to the rated output voltage in stages. Thus, when the actual output voltage of the inverter circuit 13 is controlled according to the output voltage reference value, the actual output voltage can also be increased from the first voltage to the rated output voltage in stages, thereby enabling the load 30 to start successfully.

[0111] Step S115: Adjust the voltage deviation between the output voltage reference value and the actual output voltage to generate a control signal and output it to the inverter circuit. The control signal is used to control the output voltage of the AC terminal of the inverter circuit to be increased from the first voltage to the rated output voltage in stages.

[0112] In some embodiments, the control signal may include a drive signal for driving the switching transistors on the inverter circuit 13, such as a PWM (Pulse Width Modulation) signal. Understandably, under the control of the control signal, the actual output voltage of the inverter circuit 13 can be made to gradually approach the output voltage reference value.

[0113] For example, in step S115, the target duty cycle is obtained by dividing the output voltage reference value by the bus voltage (i.e., the voltage across capacitor C2). Furthermore, based on the PWM modulator ( Figure 2 (Not shown) and a control signal including the target duty cycle is modulated using the target duty cycle. In this way, by controlling the duty cycle and conduction logic of the switching transistors on the inverter circuit 13 through the control signal, the actual output voltage can be made close to or even equal to the output voltage reference value, thereby enabling the actual output voltage of the inverter circuit 13 to be increased from the first voltage value to the rated output voltage in stages, thereby realizing the safe start-up of the load 30.

[0114] Understandably, the deviation adjustment mentioned in this application can be based on at least one of the following algorithms: PID (Proportion-Integration-Differential Control) and PI (Proportional-Integral Control). Of course, other adjustment algorithms can also be used. This application does not limit the specific algorithm used for deviation adjustment.

[0115] Please see Figure 12 In some embodiments, when it is determined, based on the relationship between the rated output power of the load and the rated output power of the inverter circuit, that it is necessary to perform frequency reduction while performing voltage reduction in the first stage to ensure normal load startup, the following steps are also required. The specific determination process is described in the foregoing embodiments.

[0116] Step S114 includes the following steps S121-S123.

[0117] Step S121: Determine the corresponding frequency adjustment coefficient according to the preset second function relationship, wherein the frequency adjustment coefficient is less than or equal to 1 and the frequency adjustment coefficient is greater than 0.

[0118] The frequency adjustment coefficient represents the ratio of the actual output voltage frequency to the rated frequency. The second functional relationship represents the relationship between the frequency adjustment coefficient and the duration of the adjustment phase. Thus, by appropriately setting the second functional relationship, the frequency adjustment coefficient in the first phase can change according to the second preset rule, while the frequency adjustment coefficient in the second and third phases remains at 1.

[0119] Step S122: Determine the reference frequency based on the frequency adjustment coefficient and the rated frequency.

[0120] In some embodiments, the frequency adjustment coefficient can be periodically obtained based on the second functional relationship and the duration of the adjustment phase, and the product of the obtained frequency adjustment coefficient and the rated frequency can be calculated as the reference frequency. Similarly, since the frequency adjustment coefficient changes according to the second preset rule from the first stage to the third stage, and the reference frequency is proportional to the frequency adjustment coefficient, the reference frequency from the first stage to the third stage can also change according to the second preset rule. The second preset rule is used to raise the reference frequency from the first frequency to the rated frequency in the first stage, and the reference frequency and the reference voltage amplitude satisfy a preset relationship (e.g., ...). Figure 8 , Figure 10 The preset relationship shown in any of the curves (a)-(d) and the reference frequency used to keep the reference frequency at the rated frequency in the second and third stages.

[0121] In other embodiments, the second functional relationship can also be used to represent the relationship between the reference voltage amplitude and the frequency adjustment coefficient. Thus, in step S122, the frequency adjustment coefficient can be periodically obtained based on the second functional relationship and the reference voltage amplitude, and the product of the obtained frequency adjustment coefficient and the rated frequency can be calculated as the reference frequency. This ensures that the relationship between the reference frequency and the reference voltage amplitude satisfies a preset relationship in the first stage, for example... Figure 8 , Figure 10 The preset relationship shown by any curve in (a)-(d).

[0122] Understandably, this application does not limit the specific functional expressions of the first and second functional relationships. For example, in some embodiments, both the first and second functional relationships can be based on the relationship between the duration represented by the Ramp function and the corresponding coefficient. That is, the preset functional relationship uses the Ramp function to output different values ​​as corresponding coefficients according to different times, and the coefficient increases with the increase of time. In this way, the coefficient can gradually increase from a lower value.

[0123] Step S123: Determine the output voltage reference value based on the reference voltage amplitude and reference frequency.

[0124] In step S123, the phase angle can be calculated based on the reference frequency, and then the phase angle can be integrated to obtain the phase. The output voltage reference value can then be calculated based on the product of the reference voltage amplitude and the phase.

[0125] Since the reference frequency in step S121 is increased from the first frequency to the rated frequency in the first stage and remains at the rated frequency in the second and third stages, the frequency of the output voltage reference value can be increased from the first frequency to the rated frequency in the first stage and remains at the rated frequency in the second and third stages. Therefore, when the actual output voltage of the inverter circuit 13 is controlled according to the output voltage reference value, the frequency of the actual output voltage can also be increased from the first frequency to the rated frequency in the first stage and remains at the rated frequency in the second and third stages. Thus, the probability of successful start-up of the load 30 can be improved by frequency modulation.

[0126] In summary, by executing steps S121 to S124, when it is confirmed that the theoretical torque is less than the load torque, the frequency of the actual output voltage can be reduced to the first frequency, and during the remaining stages of the first stage 0 to T1, the frequency of the actual output voltage can be increased from the first frequency to the rated frequency, and the actual output voltage of the AC terminal can be increased from the first voltage to the second voltage. Thus, by adjusting the speed through frequency conversion and voltage conversion, it is beneficial to enable the load 30 to start successfully.

[0127] Please continue reading. Figure 13 In some embodiments, step S115 includes the following steps S131-S134.

[0128] Step S131: Adjust the voltage deviation between the output voltage reference value and the actual output voltage to obtain the first output current reference value.

[0129] In some embodiments, the difference between the output voltage reference value and the actual output voltage can be calculated as the voltage deviation value.

[0130] Step S132: Limit the first output current reference value to obtain the second output current reference value.

[0131] In some embodiments, limiting the first output current reference value may include:

[0132] When the first output current reference value is greater than or equal to the first current threshold and less than or equal to the second current threshold, the first output current reference value is used as the second output current reference value; when the first output current reference value is less than the first current threshold, the first current threshold is used as the second output current reference value; when the first output current reference value is greater than the second current threshold, the second current threshold is used as the second output current reference value. Here, the first current threshold is negative, the second current threshold is positive, and the first and second current thresholds are opposites of each other. Thus, through the limiting process in step S132, the obtained second output current reference value can be limited to a certain range, reducing overshoot caused by an excessively large absolute value of the second output current reference value.

[0133] Step S133: Adjust the deviation between the second output current reference value and the actual output current to obtain the target output voltage.

[0134] In some embodiments, the difference between the second output current reference value and the actual output current can be calculated as the current deviation value.

[0135] Step S134: Generate a control signal based on the target output voltage and output it to the inverter circuit.

[0136] In summary, by executing steps S131 to S132, the first output current reference value can be bidirectionally limited in both positive and negative directions, so that the second output current reference value after the limiting process is limited to the shape of a trapezoidal wave, which is beneficial to the output current limitation of the entire control system, thereby better suppressing the current rise of the current surge load at the moment of startup.

[0137] Please continue reading. Figure 14 In some other embodiments, step S115 includes steps S141-S144 as follows.

[0138] Step S141: Adjust the voltage deviation between the output voltage reference value and the actual output voltage to obtain the initial value of the output voltage.

[0139] In some embodiments, the difference between the output voltage reference value and the actual output voltage can be used as the voltage deviation value.

[0140] Step S142: Adjust the deviation between the absolute value of the actual output current and the preset current threshold to obtain the voltage adjustment amount, and the polarity of the voltage adjustment amount is the same as the polarity of the actual output current.

[0141] The preset current threshold represents the current limit that triggers current limiting protection. Therefore, if the absolute value of the actual output current exceeds the preset current threshold, it indicates that the actual output current of the inverter circuit is at risk of overcurrent.

[0142] In some embodiments, after determining that the absolute value of the actual output current is greater than a preset current threshold, the difference between the absolute value of the actual output current and the preset current threshold can be obtained as the current deviation.

[0143] In other embodiments, the peak value of the actual output current can be obtained. When the absolute value of the peak value of the actual output current is greater than a preset current threshold, it is determined that the peak value of the actual output current is greater than the preset current threshold. Accordingly, the difference between the absolute value of the peak value of the actual output current and the preset current threshold can be calculated as the current deviation. In this way, the probability of false positives and false negatives can be reduced, and the response speed can be improved.

[0144] In other embodiments, the absolute value of the average actual output current or the absolute value of the effective actual output current can be compared with a preset current threshold to determine whether the absolute value of the actual output current is greater than the preset current threshold. Correspondingly, in other embodiments, the current deviation can be determined based on the absolute value of the corresponding average actual output current and the preset current threshold, or based on the absolute value of the corresponding effective actual output current and the preset current threshold. This application does not limit the method for determining the current deviation between the absolute value of the actual output current and the preset current threshold in step S142.

[0145] In step S142, the voltage regulation amount is used to characterize the influence of the current deviation on the actual output voltage. In other words, the voltage regulation amount can be considered as the feedforward value obtained by feedforward control of the actual output voltage through the actual output current.

[0146] In some embodiments, after adjusting the current deviation to determine the absolute value of the voltage regulation, the sign of the actual output current is extracted using a sign function, such as using the sign function to extract the sign of the peak, effective, or average value of the actual output current. Then, the voltage regulation is determined based on the product of the absolute value and the sign of the voltage regulation.

[0147] In other embodiments, when it is determined in step S142 that the absolute value of the actual output current is less than or equal to a preset current threshold, the voltage regulation amount is determined to be 0.

[0148] Step S143: Determine the target output voltage based on the voltage adjustment amount and the initial value of the output voltage.

[0149] In some embodiments, the difference between the initial value of the output voltage and the voltage regulation amount can be used as the target output voltage.

[0150] Step S144: Generate a control signal based on the target output voltage and output it to the inverter circuit.

[0151] Thus, by executing steps S141-S144, feedforward control based on the actual output current can be introduced to combine with feedback control of the actual output voltage, thereby achieving faster suppression of the starting current.

[0152] Please see Figure 15 , Figure 15 This is a specific control block diagram of a control method for implementing an inverter circuit, provided as an embodiment of this application.

[0153] First, the Energy Management System (EMS) 501 loaded on the controller 11 receives a start command. When it confirms that the load 30 is a current-impact load to be started, or when the comparator 503 outputs a result indicating that the absolute value of the actual output current Iout_fdb1 obtained after processing by the first absolute value extractor 502 is greater than the preset current threshold Ith, the selector SW1 is triggered to enable the first timer 504 to start timing, and the selector SW2 is enabled to acquire the reference voltage amplitude Vamp. The first timer 504 stops timing at the end of the third stage. In one embodiment, the actual output current can be the output current of the inverter circuit or the inductor current of the inverter circuit.

[0154] In this process, when the EMS determines that frequency reduction is not required based on the rated output power of the load and the rated output power of the inverter circuit, the enable selector SW3 selects the rated frequency fe and outputs it to the first multiplier 508. Simultaneously, after the first timer 504 starts timing, it outputs the corresponding timing value to the voltage adjustment coefficient generator 505. The voltage adjustment coefficient generator 505, based on a preset first function relationship, calculates the corresponding reference voltage amplitude Vamp according to the timing value output by the first timer 504 and the rated output voltage Ve, and this value is selected by selector SW2 and output to the reference voltage generator 510. When the inverter circuit is controlled according to the reference voltage amplitude Vamp generated based on the first function relationship, the actual output voltage of the inverter circuit 13 can be gradually increased from the first voltage to the rated output voltage. Then, the first multiplier 508 calculates the angular velocity ω based on the rated frequency fe and 2π and outputs it to the integrator 509. The integrator 509 integrates ω and outputs the phase θ to the reference voltage generator 510. The reference voltage generator 510 calculates the output voltage reference value Vref based on the reference voltage amplitude Vamp and phase θ.

[0155] Subsequently, in the voltage control loop, the first subtractor 511 calculates the voltage deviation value Vdev based on the output voltage reference value Vref and the actual output voltage V_fdb. The first PI controller 512 adjusts the voltage deviation value to obtain the first output current reference value I_ref1.

[0156] Next, in the current control loop, limiter 513 limits the first output current reference value I_ref1 to obtain the second output current reference value I_ref2. Second subtractor 514 calculates the current deviation value Idev based on the second output current reference value I_ref2 and the actual output current Iout_fdb1. Then, second PI controller 515 adjusts the current deviation value Idev to calculate the target output voltage V_aim. Finally, PWM controller 516 generates a PWM signal based on the target output voltage V_aim and sends it to the inverter circuit 13 in the power conversion device 10.

[0157] exist Figure 15In the control block diagram shown, when the EMS confirms the need to enable frequency reduction regulation, in addition to enabling selector SW3 to select the reference frequency f_ref and output it to the first multiplier 508, it also enables the second timer 506 to start timing. The second timer 506 stops timing at the end of the first stage. After the second timer 506 starts timing, it outputs the corresponding timing value to the frequency adjustment coefficient generator 507. The frequency adjustment coefficient generator 507 calculates the corresponding reference frequency f_ref based on a preset second function relationship, according to the timing value output by the second timer 506 and the rated frequency fe. This reference frequency f_ref is then selected by selector SW3 and output to the first multiplier 508. Understandably, after selector SW3 selects the reference frequency f_ref and outputs it to the first multiplier 508, the subsequent process is roughly the same as when the theoretical torque corresponding to the first voltage is greater than or equal to the load torque. Please refer to the above for details; further elaboration is omitted here.

[0158] exist Figure 15 In the control block diagram shown, when the EMS confirms that the load 30 is a non-current impulse load, and the result output by comparator 503 indicates that the absolute value of the actual output current Iout_fdb1 obtained after processing by the first absolute value extractor 502 is less than or equal to the preset current threshold Ith, selector SW1 is triggered to enable selector SW2 to select the rated output voltage Ve and output it to the reference voltage generator 610, and selector SW3 to select the rated frequency Fe and output it to the first multiplier 608. At the same time, the first timer 504 and the second timer 506 are disabled. Thus, when the load 30 is a non-current impulse load, the inverter circuit 13 can be controlled based on the rated output voltage Ve and the rated frequency Fe.

[0159] In summary, through Figure 15 The specific control block diagram shown allows the inverter circuit 13 to control the actual output voltage of the AC terminal to be increased from the first voltage to the rated output voltage in stages when the load 30 is a current-impact load to be started, thereby enabling the load 30 to start successfully.

[0160] Please see Figure 16 , Figure 16 A specific control block diagram for implementing a control method for an inverter circuit is provided in another embodiment of this application. Figure 16 The specific control block diagram shown is consistent with Figure 15 The specific control block diagrams shown are largely the same, the difference being... Figure 16 The specific control block diagram also includes a feedforward control loop.

[0161] In the feedforward control loop, the second absolute value extractor 608 processes the actual output current Iout_fdb1 to obtain the absolute value of the actual output current Iout_fdb2. Next, the third adder 618 calculates the current deviation I_dev based on the absolute value of the actual output current Iout_fdb2 and a preset current threshold Ith. Then, the third PI controller 619 adjusts the current deviation I_dev to obtain the absolute value of the voltage regulation Vreg. Simultaneously, the sign extractor 620 extracts the sign of the actual output current. Then, the second multiplier 621 calculates the voltage regulation ΔV based on the sign of the actual output current and the absolute value of the voltage regulation Vreg.

[0162] exist Figure 16 In the specific control block diagram shown, the second PI controller 615 outputs the initial value of the output voltage V_ini. Subsequently, the fourth subtractor 622 calculates the target output voltage V_aim based on the initial value of the output voltage V_ini and the voltage adjustment amount ΔV. Finally, the PWM controller 616 generates a PWM signal based on the target output voltage V_aim and sends it to the inverter circuit 13 in the power conversion device 10.

[0163] In summary, through Figure 16 The specific control block diagram shown can more effectively suppress inrush current based on the feedforward control loop during the start-up process of load 30.

[0164] Understandably, the first PI controller 612 / 512, the second PI controller 514 / 614, and the third PI controller 619 mentioned above are examples of existing controllers in related technologies, such as PI controllers (proportional-integral controllers). In other embodiments, other controllers may also be used, such as PID controllers (proportional-integral-derivative controllers), repetitive controllers, etc., and this application does not limit this. Correspondingly, the deviation adjustment algorithm may also be a PID adjustment algorithm (proportional-integral-derivative control), a PI adjustment algorithm (proportional-integral control), etc., or of course, other adjustment algorithms.

[0165] Understandable. Figure 15 and Figure 16The control process shown in the control block diagram can be implemented by a computer program stored in the controller 11 of the power conversion device 10. Specific implementation details will not be elaborated here.

[0166] Please refer to it again. Figure 2 One embodiment of this application also provides a power conversion device 10, including an inverter circuit 13 and a controller 11. The AC terminal of the inverter circuit 13 is used to connect a load 30. The controller 11 is used to execute the control method of the inverter circuit provided in any of the above embodiments.

[0167] Please see Figure 17 This application also provides an energy storage device 100, including an energy storage battery 101 and a power conversion device 10. The energy storage battery 101 is connected to the DC terminal of the inverter circuit 13 of the power conversion device 10. Understandably, the energy storage device 100 can be a simple energy storage and release device, or it can be any electronic device including the energy storage battery 101, such as a self-moving device, air conditioner, refrigerator, etc. This application does not limit the specific type of the energy storage device 100.

[0168] Please see Figure 18 An embodiment of this application also provides a control device 200, including a memory 12 and a processor 201. The memory 12 stores a computer program so that when the processor 201 executes the computer program, it implements the control method for the inverter circuit as described in any of the above embodiments. It is understood that the control device 200 can be integrated into the power conversion device 10, or the control device 200 can be separately configured from the power conversion device 10.

[0169] Please see Figure 19 This application also provides a computer-readable storage medium 300, including a computer program 301. When executed by a processor, the computer program 301 implements the control method for the inverter circuit as described in the above technical solutions. The computer-readable storage medium may be a portable compact disc read-only memory (CD-ROM) and include program code, and can run on a terminal device, such as a personal computer. However, the program product of this invention is not limited thereto. In this document, the readable storage medium can be any tangible medium containing or storing a program that can be used by or in conjunction with an instruction execution system, apparatus, or device.

[0170] It is understood that the controller 11 and processor 201 mentioned in this application may include at least one of a microcontroller unit (MCU), a central processing unit (CPU), other general-purpose processors, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or other programmable logic devices, discrete gate or transistor logic devices.

[0171] The above-described program product may employ any combination of one or more readable media. A readable medium may be a readable signal medium or a readable storage medium. A readable storage medium may be, for example, but not limited to, an electrical, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any combination thereof. More specific examples of readable storage media (a non-exhaustive list) include: electrical connections having one or more wires, portable disks, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), optical fiber, portable compact disk read-only memory (CD-ROM), optical storage devices, magnetic storage devices, or any suitable combination thereof.

[0172] Computer-readable signal media may include data signals propagated in baseband or as part of a carrier wave, carrying readable program code. Such propagated data signals may take various forms, including but not limited to electromagnetic signals, optical signals, or any suitable combination thereof. A readable signal medium may also be any readable medium other than a readable storage medium, capable of sending, propagating, or transmitting programs for use by or in conjunction with an instruction execution system, apparatus, or device.

[0173] The program code contained on the readable medium may be transmitted using any suitable medium, including but not limited to wireless, wired, optical fiber, RF, etc., or any suitable combination thereof.

[0174] Program code for performing the operations of this invention can be written in any combination of one or more programming languages, including object-oriented programming languages ​​such as Java and C++, and conventional procedural programming languages ​​such as C or similar languages. The program code can execute entirely on the user's computing device, partially on the user's device, as a standalone software package, partially on the user's computing device and partially on a remote computing device, or entirely on a remote computing device or server. In cases involving remote computing devices, the remote computing device can be connected to the user's computing device via any type of network, including a local area network (LAN) or a wide area network (WAN), or it can be connected to an external computing device (e.g., via the Internet using an Internet service provider).

[0175] Furthermore, the above figures are merely illustrative of the processes included in the method according to exemplary embodiments of the present invention, and are not intended to be limiting. It is readily understood that the processes shown in the above figures do not indicate or limit the temporal order of these processes. Additionally, it is readily understood that these processes may be executed synchronously or asynchronously, for example, in multiple modules.

[0176] The above are merely specific embodiments of this application, but the scope of protection of this application is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in this application, and these modifications or substitutions should all be covered within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A control method for an inverter circuit, wherein the AC terminal of the inverter circuit is used to connect a load, characterized in that, The method includes: When the load is a current-impact type load to be started, the actual output voltage of the AC terminal of the inverter circuit is controlled to be increased from a first voltage to the rated output voltage in stages; wherein, In the first stage, the actual output voltage of the AC terminal of the inverter circuit is increased from the first voltage to the second voltage, wherein the second voltage is greater than or equal to the lower limit of the output voltage of the inverter circuit; During the second stage, the actual output voltage is controlled to be maintained at the second voltage, wherein the start time of the second stage is the end time of the first stage; the end time of the second stage is later than the time when the output torque of the inverter circuit increases to the maximum torque; In the third stage, the actual output voltage is controlled to increase from the second voltage to the rated output voltage, wherein the start time of the third stage is the end time of the second stage.

2. The method of claim 1, wherein, Before the step of controlling the actual output voltage of the AC terminal of the inverter circuit to increase from the first voltage to the second voltage in the first stage, the method further includes: obtaining the rated output power of the load and the rated output power of the inverter circuit; The step of controlling the actual output voltage of the AC terminal of the inverter circuit to increase from the first voltage to the second voltage during the first stage includes: When the rated output power of the load and the rated output power of the inverter circuit meet a first condition, in the first stage, while raising the output constant voltage of the inverter circuit from a first voltage to a second voltage, the frequency of the actual output voltage is gradually raised from a first frequency to the rated frequency; the first condition is that the deviation between the rated output power of the load and the rated output power of the inverter circuit is within a preset deviation range; and / or When the rated output power of the load and the rated output power of the inverter circuit satisfy the second condition, the output constant voltage of the inverter circuit is boosted from the first voltage to the second voltage in the first stage; and / or When the relationship between the rated output power of the load and the rated output power of the inverter circuit does not satisfy the first and second conditions, the output voltage of the inverter voltage is increased from the first voltage to the second voltage in the first stage, or the output voltage of the inverter voltage is increased from the first voltage to the second voltage in the first stage while the frequency of the actual output voltage is gradually increased from the first frequency to the rated frequency.

3. The method of claim 2, wherein, The method further includes: When the rated output power of the load and the rated output power of the inverter circuit satisfy the second condition, the frequency of the actual output voltage of the inverter circuit is controlled to be the rated frequency.

4. The method of claim 1, wherein, The duration of the first stage is less than the undervoltage protection trigger duration of the inverter circuit.

5. The method of claim 1, wherein, Before controlling the actual output voltage of the AC terminal of the inverter circuit to be increased from the first voltage to the rated output voltage in stages, the method further includes: Obtain a startup command, and determine the type of the load based on the startup command; the type of the load includes a current inrush load; and / or When the absolute value of the actual output current at the AC terminal is greater than or equal to a preset current threshold, the load is confirmed to be a current surge load.

6. The method of claim 1, wherein, The control of the output voltage of the AC terminal of the inverter circuit is to increase from the first voltage to the rated output voltage in stages, including: Obtain the rated output voltage and rated frequency of the AC terminal; The corresponding voltage adjustment coefficient is determined according to a preset first functional relationship, wherein the voltage adjustment coefficient is less than or equal to 1 and the voltage adjustment coefficient is greater than 0; The reference voltage amplitude is determined based on the voltage adjustment coefficient and the rated output voltage. The output voltage reference value is determined based on the reference voltage amplitude and the rated frequency; The voltage deviation between the reference output voltage value and the actual output voltage is adjusted to generate a control signal and output to the inverter circuit. The control signal is used to control the output voltage of the AC terminal to be increased from the first voltage to the rated output voltage in stages.

7. The method of claim 1, wherein, The control of the output voltage of the AC terminal of the inverter circuit is to increase from the first voltage to the rated output voltage in stages, including: Obtain the rated output voltage and rated frequency of the AC terminal; The voltage adjustment coefficient and frequency adjustment coefficient are determined according to the preset first functional relationship and second functional relationship, respectively, wherein the voltage adjustment coefficient is less than or equal to 1 and the voltage adjustment coefficient is greater than 0; the frequency adjustment coefficient is less than or equal to 1 and the frequency adjustment coefficient is greater than 0. The reference voltage amplitude is determined based on the voltage adjustment coefficient and the rated output voltage. The reference frequency is determined based on the frequency adjustment factor and the rated frequency; The output voltage reference value is determined based on the reference voltage amplitude and the reference frequency; The voltage deviation between the reference output voltage value and the actual output voltage is adjusted to generate a control signal and output to the inverter circuit. The control signal is used to control the output voltage of the AC terminal to be increased from the first voltage to the rated output voltage in stages.

8. The method of claim 6, wherein, The step of adjusting the voltage deviation between the output voltage reference value and the actual output voltage to generate a control signal and output it to the inverter circuit includes: The voltage deviation between the reference output voltage value and the actual output voltage is adjusted to obtain the initial output voltage value; The deviation between the absolute value of the actual output current and the preset current threshold is adjusted to obtain the voltage adjustment amount, and the polarity of the voltage adjustment amount is the same as the polarity of the actual output current. The target output voltage is determined based on the voltage adjustment amount and the initial value of the output voltage. The control signal is generated based on the target output voltage and output to the inverter circuit.

9. A power conversion apparatus comprising an inverter circuit and a controller, an alternating current terminal of the inverter circuit being for connecting a load; characterized in that, The controller is used to execute the control method for the inverter circuit as described in any one of claims 1 to 8.

10. An energy storage device, characterized by, The energy storage device includes an energy storage battery and a power conversion device as described in claim 9, wherein the energy storage battery is connected to the DC terminal of the inverter circuit of the power conversion device.

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