Inverter control method, control device, controller and photovoltaic energy storage system

Abstract

The invention discloses a control method, a control device, a controller and a photovoltaic energy storage system of an inverter, the inverter is connected with a non-linear load and is used for converting direct current into alternating current to supply power to the non-linear load, and the control method of the inverter comprises the following steps: acquiring peak current of the non-linear load in a previous cycle; determining the suppression voltage of the current cycle based on the peak current; performing voltage amplitude suppression on the reference voltage based on the suppression voltage to obtain a given voltage of the current cyclic wave; and controlling the inverter according to the given voltage so as to suppress the peak current of the nonlinear load. Therefore, according to the method, the suppression voltage is determined based on the peak current of the non-linear load in the last cycle, so that voltage amplitude suppression is carried out on the reference voltage, the peak current of the non-linear load is reduced, and overcurrent of the non-linear load under the condition that the inverter directly supplies power to the non-linear load is avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of photovoltaic energy storage systems, and in particular to a control method and control device of an inverter, a controller and a photovoltaic energy storage system. Background Art

[0002] The photovoltaic energy storage inverter includes photovoltaic MPPT (Maximum Power Point Tracking, maximum power point tracking control solar controller), battery energy storage and inverter parts. The output end of the inverter is connected to the local load or connected to the grid through a grid-connected switch.

[0003] In the related art, when the inverter is connected to the grid, the grid-connected switch is controlled to close, and the inverter, local load and grid are directly connected, and electric energy flows between the three. When the inverter is off-grid, the grid-connected switch is controlled to open, and the inverter directly supplies power to the local load. Among them, the local load includes many types. When the local load is a nonlinear load, the local load is prone to current pulses at the maximum and minimum values ​​of the sinusoidal voltage output by the inverter, thereby causing the local load to overcurrent and trigger the local load overcurrent protection shutdown. Summary of the invention

[0004] The present invention aims to solve one of the technical problems in the related art to at least a certain extent. To this end, the first object of the present invention is to provide a control method for an inverter, which determines a suppression voltage based on the peak current of the nonlinear load in the previous cycle to suppress the voltage amplitude of the reference voltage, thereby reducing the peak current of the nonlinear load and avoiding overcurrent of the nonlinear load when the inverter directly supplies power to the nonlinear load.

[0005] A second objective of the present invention is to provide a control device for an inverter.

[0006] The third object of the present invention is to provide a controller.

[0007] The fourth objective of the present invention is to provide a photovoltaic energy storage system.

[0008] A fifth objective of the present invention is to provide a photovoltaic energy storage system.

[0009] To achieve the above-mentioned purpose, a first embodiment of the present invention proposes a control method for an inverter, wherein the inverter is connected to a nonlinear load and is used to convert direct current into alternating current to power the nonlinear load. The control method for the inverter includes: obtaining the peak current of the nonlinear load in the previous cycle; determining the suppression voltage of the current cycle based on the peak current; suppressing the voltage amplitude of a reference voltage based on the suppression voltage to obtain a given voltage of the current cycle; and controlling the inverter according to the given voltage to suppress the peak current of the nonlinear load.

[0010] According to the control method of the inverter of the embodiment of the present invention, the peak current of the nonlinear load in the previous cycle is first obtained, and the suppression voltage of the current cycle is determined based on the peak current, and the voltage amplitude of the reference voltage is suppressed based on the suppression voltage to obtain the given voltage of the current cycle, and then the inverter is controlled according to the given voltage to suppress the peak current of the nonlinear load. Therefore, the method determines the suppression voltage based on the peak current of the nonlinear load in the previous cycle to suppress the voltage amplitude of the reference voltage, thereby reducing the peak current of the nonlinear load and avoiding overcurrent of the nonlinear load when the inverter directly supplies power to the nonlinear load.

[0011] In addition, the control method of the inverter according to the above embodiment of the present invention may also have the following additional technical features:

[0012] According to one embodiment of the present invention, determining the suppression voltage of the current cycle based on the peak current includes: determining the voltage suppression coefficient of the current cycle based on the peak current; obtaining the product of the voltage suppression coefficient and the reference suppression voltage to obtain the suppression voltage of the current cycle.

[0013] According to one embodiment of the present invention, the voltage suppression coefficient of the current cycle is determined based on the peak current, including: when the peak current is less than or equal to a first current threshold, determining the voltage suppression coefficient to be zero; when the peak current is greater than the first current threshold and less than or equal to a second current threshold, determining the voltage suppression coefficient based on the peak current and a linear mapping relationship between the peak current and the voltage suppression coefficient; when the peak current is greater than the second current threshold, determining the voltage suppression coefficient to be a preset value; wherein the preset value is greater than zero, and the second current threshold is greater than the first current threshold.

[0014] According to an embodiment of the present invention, the voltage suppression coefficient ranges from [0, 0.25].

[0015] According to one embodiment of the present invention, the voltage amplitude of the reference voltage is suppressed based on the suppression voltage to obtain the given voltage of the current cycle, including: obtaining the voltage difference between the reference voltage and the suppression voltage to obtain the given voltage of the current cycle.

[0016] According to an embodiment of the present invention, the reference voltage is a sinusoidal wave voltage, and the reference suppression voltage is a continuous alternating voltage or a discontinuous alternating voltage.

[0017] According to an embodiment of the present invention, the reference suppression voltage is one of a sine wave voltage, a square wave voltage, a trapezoidal wave voltage and a triangle wave voltage.

[0018] According to an embodiment of the present invention, when the reference suppression voltage is a continuous sinusoidal voltage, the frequency of the reference suppression voltage is 3*n times the frequency of the reference voltage, where n is a positive integer.

[0019] According to one embodiment of the present invention, controlling an inverter according to a given voltage includes: obtaining the output voltage of the previous cycle inverter; obtaining the voltage difference between the given voltage and the output voltage; determining a modulation signal of the inverter based on the voltage difference; and generating a PWM (Pulse width modulation) signal based on the modulation signal to control the inverter.

[0020] According to one embodiment of the present invention, a modulation signal of an inverter is determined based on a voltage difference, including: inputting the difference into a PR (Proportional Resonant) controller and a repetitive controller respectively to obtain a first control voltage and a second control voltage; obtaining the sum of the first control voltage and the second control voltage to obtain a modulation signal.

[0021] To achieve the above-mentioned purpose, a second embodiment of the present invention proposes a control device for an inverter, wherein the inverter is connected to a nonlinear load and is used to convert direct current into alternating current to power the nonlinear load. The control device for the inverter includes: an acquisition module, used to acquire the peak current of the nonlinear load in the previous cycle; a control module, used to determine the suppression voltage of the current cycle based on the peak current, and suppress the voltage amplitude of the reference voltage based on the suppression voltage to obtain a given voltage of the current cycle, and control the inverter according to the given voltage to suppress the peak current of the nonlinear load.

[0022] According to the control device of the inverter of the embodiment of the present invention, the peak current of the nonlinear load in the previous cycle is obtained by the acquisition module, the control module determines the suppression voltage of the current cycle based on the peak current, and suppresses the voltage amplitude of the reference voltage based on the suppression voltage to obtain the given voltage of the current cycle, and controls the inverter according to the given voltage to suppress the peak current of the nonlinear load. Thus, the device determines the suppression voltage based on the peak current of the nonlinear load in the previous cycle to suppress the voltage amplitude of the reference voltage, thereby reducing the peak current of the nonlinear load and avoiding the overcurrent of the nonlinear load when the inverter directly supplies power to the nonlinear load.

[0023] To achieve the above objectives, a third aspect of the present invention proposes a controller, including: a memory, a processor, and a program stored in the memory and executable on the processor. When the processor executes the program, the above inverter control method is implemented.

[0024] According to the controller of the embodiment of the present invention, when the processor executes the program, the control method of the inverter mentioned above is implemented. Based on the control method of the inverter mentioned above, the suppression voltage is determined based on the peak current of the nonlinear load in the previous cycle to suppress the voltage amplitude of the reference voltage, thereby reducing the peak current of the nonlinear load and avoiding overcurrent of the nonlinear load when the inverter directly supplies power to the nonlinear load.

[0025] To achieve the above-mentioned purpose, a fourth aspect of the present invention provides a photovoltaic energy storage system, including the above-mentioned inverter control device, or the above-mentioned controller.

[0026] According to the photovoltaic energy storage system of the embodiment of the present invention, based on the control device of the above-mentioned inverter or the above-mentioned controller, the suppression voltage is determined based on the peak current of the non-linear load in the previous cycle to suppress the voltage amplitude of the reference voltage, thereby reducing the peak current of the non-linear load and avoiding overcurrent of the non-linear load when the inverter directly supplies power to the non-linear load.

[0027] To achieve the above-mentioned purpose, the fifth aspect of the present invention proposes a photovoltaic energy storage system, comprising: a photovoltaic module; an inverter, the DC side of the inverter is connected to the photovoltaic module, and the AC side of the inverter is connected to the power grid and the load, and is used to convert the DC power of the photovoltaic module into AC power and feed it to the power grid and / or power the load, wherein the load includes a nonlinear load; a controller, the controller is connected to the inverter, and is used to obtain the peak current of the nonlinear load in the previous cycle when the inverter is off-grid, and determine the suppression voltage of the current cycle based on the peak current, and suppress the voltage amplitude of the reference voltage based on the suppression voltage to obtain a given voltage of the current cycle, and control the inverter according to the given voltage to suppress the peak current of the nonlinear load.

[0028] According to the photovoltaic energy storage system of the embodiment of the present invention, the DC side of the inverter is connected to the photovoltaic module, the AC side of the inverter is connected to the power grid and the load, and the controller is connected to the inverter, wherein the load includes a nonlinear load. The inverter converts the DC power of the photovoltaic module into AC power and feeds it to the power grid and / or supplies power to the load. When the inverter is off-grid, the controller obtains the peak current of the nonlinear load in the previous cycle, and determines the suppression voltage of the current cycle based on the peak current, and suppresses the voltage amplitude of the reference voltage based on the suppression voltage to obtain the given voltage of the current cycle, and controls the inverter according to the given voltage to suppress the peak current of the nonlinear load. The photovoltaic energy storage system determines the suppression voltage based on the peak current of the nonlinear load in the previous cycle to suppress the voltage amplitude of the reference voltage, thereby reducing the peak current of the nonlinear load and avoiding overcurrent of the nonlinear load when the inverter directly supplies power to the nonlinear load.

[0029] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 is a flow chart of a control method of an inverter according to an embodiment of the present invention;

[0031] Figure 2 A circuit diagram of an inverter application according to an embodiment of the present invention;

[0032] Figure 3 is a control block diagram of an inverter according to an embodiment of the present invention;

[0033] Figure 4 is a schematic diagram of peak current and voltage suppression coefficient according to an embodiment of the present invention;

[0034] Figure 5 is a flow chart of a method for controlling an inverter according to an embodiment of the present invention;

[0035] Figure 6 is a control block diagram of an inverter according to an embodiment of the present invention;

[0036] Figure 7 Based on Figure 6 A sampling schematic diagram of the control block diagram shown;

[0037] Figure 8 Based on Figure 6 The simulation waveform diagram of the control block diagram shown;

[0038] Fig. 9 Based on Figure 3 A sampling schematic diagram of the control block diagram shown;

[0039] Fig.10 Based on Figure 3 The simulation waveform diagram of the control block diagram shown;

[0040] Fig.11 A schematic diagram of simulation waveform comparison according to a specific embodiment of the present invention;

[0041] Fig.12 is a block diagram of a control device for an inverter according to an embodiment of the present invention;

[0042] Fig.13 is a block diagram of a controller according to an embodiment of the present invention;

[0043] Fig.14 is a block diagram of a photovoltaic energy storage system according to an embodiment of the present invention;

[0044] Fig.15 is a block diagram of a photovoltaic energy storage system according to an embodiment of the present invention;

[0045] Fig.16 Schematic diagram of the connection of a photovoltaic energy storage system according to an embodiment of the present invention. DETAILED DESCRIPTION

[0046] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and should not be construed as limiting the present invention.

[0047] The following describes an inverter control method, an inverter control device, a controller, and a photovoltaic energy storage system provided in embodiments of the present invention with reference to the accompanying drawings.

[0048] Figure 1 4 is a flow chart of a method for controlling an inverter according to an embodiment of the present invention.

[0049] In one embodiment of the present invention, the inverter is connected to the non-linear load and is used to convert direct current into alternating current to supply power to the non-linear load.

[0050] Specifically, an inverter is a converter that converts DC power (such as power from batteries or storage bottles) into constant frequency and voltage or frequency and voltage-regulated AC power. It can be composed of units such as an inverter bridge and a filter circuit, and is widely used in technical fields such as air conditioning and home theaters. The following uses the application of an inverter in a photovoltaic energy storage system as an example for illustration.

[0051] like Figure 2As shown, the inverter 30 includes three DC / DC BOOST (Direct Current-Direct CurrentBOOST, DC-DC boost) circuits 31 and a DC / AC (Direct Current-Alternating Current, DC-AC) single-phase inverter bridge 32, wherein the three DC / DC BOOST circuits 31 are respectively connected to the photovoltaic panel 10 and the battery pack 20. The photovoltaic panel 10 is a device that uses solar energy to convert light energy into electrical energy. Under normal working conditions, the photovoltaic panel 10 directly converts light energy into electrical energy by absorbing light from the sun, and outputs the electrical energy to the inverter 30. The battery pack 20 is used for storing electrical energy. During operation, the DC / DC BOOST circuit 31 can boost direct current, and send the boosted direct current to the DC / AC single-phase inverter bridge 32, and the boosted direct current is converted into alternating current for output through the DC / AC single-phase inverter bridge 32. That is, the DC side of the inverter 30 is connected to the photovoltaic panel 10 and the battery pack 20 , and the AC side of the inverter 30 is connected to the grid 50 through the grid switch 40 on the one hand, and to the load 60 on the other hand, wherein the load 60 includes a nonlinear load 61 .

[0052] During operation, when the inverter 30 is in the grid-connected mode, the grid-connected switch 40 is controlled to be closed, so that the inverter 30 is connected to the grid 50, and electric energy flows between the inverter 30, the grid 50 and the load 60. When the inverter 30 is in the off-grid mode, the grid-connected switch 40 is controlled to be opened, so that the inverter 30 is disconnected from the grid 50, and the AC power output by the inverter 30 supplies power to the load 60.

[0053] It is understandable that the inverter 30 may be provided with only an inverter circuit to convert direct current into alternating current, and the inverter circuit may also be a three-phase inverter circuit in addition to the DC / AC single-phase inverter bridge 32, and is not limited here. The load 60 may also be provided with a linear load or other equipment type in addition to the nonlinear load 61.

[0054] Furthermore, a linear load refers to a purely resistive load whose voltage and current are completely sinusoidal. A nonlinear load refers to a load in an electronic circuit whose voltage and current are not linearly related. Nonlinear loads include not only rectifier loads, but also other loads, such as motors, which must use sinusoidal voltages. Among them, a nonlinear rectifier load refers to a load that contains a rectifier device, such as a resistive load, a capacitive load, and an inductive load.

[0055] like Figure 1 As shown, the control method of the inverter according to the embodiment of the present invention may include:

[0056] S1, obtain the peak current Ipeak of the nonlinear load in the previous cycle;

[0057] S2, determine the suppression voltage Vref of the current cycle based on the peak current Ipeak * ;

[0058] S3, based on the suppression voltage Vref * The voltage amplitude of the reference voltage Vref is suppressed to obtain the given voltage Vin of the current cycle. * ;

[0059] S4, according to the given voltage Vin * The inverter is controlled to suppress the peak current of the non-linear load.

[0060] Specifically, one cycle is a period during which the alternating current completes a complete change, that is, a sinusoidal waveform. In this embodiment, the inverter directly supplies power to the nonlinear load, and the cycle is determined based on the alternating current output by the inverter.

[0061] Combine the following Figure 2 As shown, the control method of the present application is described in detail.

[0062] When the grid-connected switch 40 is controlled to be disconnected, the inverter 30 directly supplies power to the nonlinear load 61. During the control process, the current I1 of the nonlinear load 61 is obtained in real time, and the maximum current value of the current I1 in the previous cycle is determined to obtain the peak current Ipeak of the nonlinear load 61 in the previous cycle. Then, the current magnitude of the peak current Ipeak is determined to determine the suppression voltage Vref of the current cycle based on the peak current Ipeak. * , by suppressing the voltage Vref * The purpose of suppressing the voltage amplitude of the reference voltage Vref is to obtain the given voltage Vin of the current cycle. * . Set the given voltage Vin * The preset controller is input to obtain a corresponding PWM signal to control the switch tube in the inverter 30 so that the inverter 30 outputs a corresponding alternating current, thereby achieving the purpose of suppressing the peak current Ipeak of the nonlinear load. The preset controller may be PI (Proportional Integral) control, PID (Proportion Integration Differentiation) control, etc., which may be specifically selected based on the control requirements.

[0063] The overcurrent condition of the nonlinear load in the previous cycle is determined based on the peak current Ipeak of the nonlinear load in the previous cycle. For example, the corresponding overcurrent protection threshold can be determined based on the parameters of the nonlinear load, and the overcurrent condition of the nonlinear load in the previous cycle is determined according to the current difference between the overcurrent protection threshold and the peak current Ipeak. For example, when the current difference is large, it is considered that no overcurrent will occur, and the inverter 30 is continued to be controlled according to the current parameters, that is, the voltage amplitude of the reference voltage Vref is not suppressed; when the current difference is small, it is considered that the risk of overcurrent of the nonlinear device is large, and the suppression voltage Vref is determined based on the current difference. * , in order to reduce the peak current of the non-linear load to prevent the non-linear load from overcurrent. In addition, the peak current Ipeak and the suppression voltage Vref can also be established in advance. * In the control process, the corresponding suppression voltage Vref is obtained based on the peak current Ipeak of the previous cycle. * , with the suppression voltage Vref * The voltage amplitude of the reference voltage Vref of the current cycle is suppressed to achieve the purpose of reducing the peak current of the nonlinear load in the current cycle. In addition, the peak current Ipeak and the suppression voltage Vref can also be established in advance. * The corresponding relationship model of the corresponding parameters of the suppression voltage Vref is determined based on the preset model * , no restriction is made here.

[0064] This embodiment determines the overcurrent condition of the nonlinear load based on the peak current Ipeak of the nonlinear load in the previous cycle to determine the suppression voltage Vref of the current cycle. * , by setting the suppression voltage Vref of the current cycle * It is superimposed on the reference voltage Vref to reduce the voltage amplitude of the reference voltage Vref, thereby achieving the purpose of suppressing the peak current of the non-linear load and avoiding the occurrence of non-linear load overcurrent.

[0065] According to one embodiment of the present invention, the suppression voltage of the current cycle is determined based on the peak current Ipeak, including: determining the voltage suppression coefficient B of the current cycle based on the peak current Ipeak; obtaining the product of the voltage suppression coefficient B and the reference suppression voltage to obtain the suppression voltage Vref of the current cycle * .

[0066] Specifically, the corresponding relationship between the voltage threshold coefficient B and the peak current Ipeak may be established in advance, for example, in a table form or in a formula form, which is not limited here.

[0067] In the control process, the voltage suppression coefficient B is determined by looking up the table according to the peak current Ipeak of the nonlinear load in the previous cycle, and the product of the voltage suppression coefficient B and the reference suppression voltage is used as the suppression voltage Vref of the current cycle. * Therefore, this embodiment determines the voltage suppression coefficient B based on the peak current Ipeak, and adjusts the voltage suppression coefficient B to adjust the proportion of the injected reference suppression voltage to obtain the corresponding suppression voltage Vref * .

[0068] It should be noted that the reference suppression voltage can be selected according to actual conditions, as long as the purpose of weakening the voltage amplitude of the reference signal Vref can be achieved. For example, according to one embodiment of the present invention, the reference voltage Vref is a sine wave voltage, and the reference suppression voltage is a continuous alternating voltage or an intermittent alternating voltage. For example, the reference suppression voltage is one of a sine wave voltage, a square wave voltage, a trapezoidal wave voltage, and a triangular wave voltage.

[0069] According to an embodiment of the present invention, when the reference suppression voltage is a continuous sinusoidal voltage, the frequency of the reference suppression voltage is 3*n times the frequency of the reference voltage, where n is a positive integer.

[0070] Specifically, assuming that the reference voltage Vref = Asin(ωt), where A is the amplitude of the reference voltage and ω is the angular frequency, the reference suppression voltage is A*sin(3*n*ωt), and the suppression voltage Vref * =A*B*sin(3*n*ωt) where A is the amplitude of the reference voltage, B is the voltage threshold coefficient, ω is the angular frequency of the reference voltage, and 3*n*ω is the angular frequency of the reference suppression voltage.

[0071] Therefore, the control method of this embodiment adds a frequency-multiplied component of multiples of 3 to the reference voltage Vref, and adjusts the amplitude of the 3-times-frequency component by adjusting the voltage threshold coefficient B, thereby suppressing the peak current Ipeak of the nonlinear load by adjusting the size of the frequency-multiplied component of multiples of 3.

[0072] According to one embodiment of the present invention, the voltage suppression coefficient B of the current cycle is determined based on the peak current Ipeak, including: when the peak current Ipeak is less than or equal to the first current threshold Imin, the voltage suppression coefficient B is determined to be zero; when the peak current Ipeak is greater than the first current threshold Imin and less than or equal to the second current threshold Imax, the voltage suppression coefficient B is determined according to the peak current Ipeak and the linear mapping relationship between the peak current and the voltage suppression coefficient; when the peak current Ipeak is greater than the second current threshold Imax, the voltage suppression coefficient B is determined to be a preset value; wherein the preset value is greater than zero, and the second current threshold Imax is greater than the first current threshold Imin. The range of the voltage suppression coefficient B is [0,0.25].

[0073] Specifically, refer to Figure 4 As shown, when the peak current Ipeak is less than or equal to the first current threshold Imin, the voltage suppression coefficient B is equal to 0, the suppression voltage is 0, and no suppression operation is performed on the peak current Ipeak of the nonlinear load; when the peak current Ipeak is greater than the first current threshold Imin and less than the second current threshold Imax, the voltage suppression coefficient B increases with the increase of the peak current Ipeak; when the peak current Ipeak is greater than the second current threshold Imax, the voltage suppression coefficient B is constant at a maximum value of 0.25.

[0074] According to one embodiment of the present invention, based on the suppression voltage Vref * The voltage amplitude of the reference voltage Vref is suppressed to obtain the given voltage Vin of the current cycle. * , including: obtaining the reference voltage Vref and the suppression voltage Vref * The voltage difference between the two is used to obtain the given voltage Vin of the current cycle. * .

[0075] Continue with reference voltage Vref = Asin(ωt), suppress voltage Vref * =A*B*sin(3*n*ωt), where A is the amplitude of the reference voltage, B is the voltage suppression coefficient, ω is the angular frequency of the reference voltage, and 3*n*ω is the angular frequency of the suppression voltage. For example, the given voltage Vin * =Asin(ωt)-A*B*sin(3*n*ωt), where Asin(ωt) is the reference voltage Vref, and A*B*sin(3*n*ωt) is the superimposed suppression voltage Vref * .

[0076] Therefore, this embodiment determines the voltage suppression coefficient B according to the peak current Ipeak of the nonlinear load in the previous cycle to adjust the superimposed suppression voltage Vref. *Specifically, when the peak current Ipeak is less than or equal to the first current threshold Imin, the voltage suppression coefficient B is equal to 0, and the suppression voltage Vref * is zero, given voltage Vin * is the reference voltage Vref; when the peak current Ipeak is greater than the first current threshold Imin and less than the second current threshold Imax, the given voltage Vin * The reference voltage Vref and the suppression voltage Vref * The voltage difference between the two is calculated, and the voltage suppression coefficient B is determined in real time to suppress the given voltage Vin. * Adjustments are made to suppress the peak current Ipeak of the nonlinear load and reduce the peak current Ipeak.

[0077] Furthermore, in the process of adjusting the voltage suppression coefficient B according to the peak current Ipeak, the adjustment speed can be constrained as follows: in the process of increasing the peak current Ipeak, the voltage suppression coefficient B needs to respond quickly, for example, the voltage suppression coefficient B changes quickly at the ms level to match the increase speed of the peak current Ipeak to prevent the occurrence of overcurrent; in the process of decreasing the peak current Ipeak, the voltage suppression coefficient B can be reduced at a speed of 100 ms or even s.

[0078] The control process of the control method is described in detail below with reference to the accompanying drawings.

[0079] According to one embodiment of the present invention, according to a given voltage Vin * Control the inverter, including: obtaining the output voltage Vin of the previous cycle inverter; obtaining the given voltage Vin * and the output voltage Vin; determining a modulation signal Vout of the inverter based on the voltage difference; and generating a PWM signal based on the modulation signal Vout to control the inverter.

[0080] Specifically, the output voltage Vin of the inverter is sampled in real time by a voltage sampling unit to obtain the output voltage Vin of the previous cycle inverter, obtain the voltage difference between the given voltage Vin* and the output voltage Vin, perform PID control on the voltage difference to obtain the modulation signal Vout of the inverter, generate a PWM signal based on the modulation signal Vout and a preset carrier signal, and control the switch tube in the inverter by the PWM signal to output corresponding alternating current.

[0081] According to one embodiment of the present invention, a modulation signal of an inverter is determined based on a voltage difference, including: inputting the difference into a PR controller and a repetitive controller respectively to obtain a first control voltage and a second control voltage; obtaining the sum of the first control voltage and the second control voltage to obtain a modulation signal Vout.

[0082] Specifically, Figure 3 As shown, given voltage Vin * The voltage difference between the output voltage Vin is calculated by the PR controller to output the first control voltage, given voltage Vin * The voltage difference between the first control voltage and the output voltage Vin is calculated by a repetitive controller to output a second control voltage, and the sum of the first control voltage and the second control voltage is used as the modulation signal Vout.

[0083] It should be noted that the modulation signal Vout obtained based on the PR controller and the repetitive controller is only one possible implementation method of the present application. For example, PID control, PI controller, etc. can be used to obtain the modulation signal Vout based on the given voltage Vin. * The voltage difference between the output voltage Vin and the modulation signal Vout is calculated.

[0084] As a specific embodiment of the present application, the reference voltage Vref = Asin (ωt), the reference suppression voltage is A*sin (3*ωt), and the relationship between the voltage suppression coefficient B and the peak current Ipeak is: Figure 3 As shown in the figure, the control method of the inverter of the present application is as follows Figure 5 As shown, the following steps may be included:

[0085] S201, obtaining the peak current Ipeak of the nonlinear load and the output voltage Vin of the inverter in the previous cycle.

[0086] S202, determine whether the peak current Ipeak is less than the first current threshold Imin. If so, execute step S203; if not, execute step S204.

[0087] S203, voltage suppression coefficient B = 0. Execute step S207.

[0088] S204, determining whether the peak current Ipeak is greater than the second current threshold Imax. If so, executing step S205; if not, executing step S206.

[0089] S205, voltage suppression coefficient B = 0.25. Execute step S207.

[0090] S206 , determining a voltage suppression coefficient B according to the peak current Ipeak and a linear mapping relationship between the peak current and the voltage suppression coefficient.

[0091] S207, calculate the suppression voltage Vref * =A*B*sin(3*n*ωt).

[0092] S208, calculate the given voltage Vin of the current cycle * =Vref-Vref * .

[0093] S209, obtain the given voltage Vin * The voltage difference △V between the output voltage Vin.

[0094] S210, input the voltage difference △V into the PR controller to obtain a first control voltage V1; input the voltage difference △V into the repetitive controller to obtain a second control voltage V2.

[0095] S211, calculate the modulation signal Vout=V1+V2.

[0096] S212, generating a PWM signal based on the modulation signal Vout to control the inverter.

[0097] Therefore, this embodiment adjusts the voltage suppression coefficient B based on the peak current Ipeak to adjust the suppression voltage to Vref * , thereby adjusting the suppression effect on the reference voltage Vref, thereby achieving the effect of reducing the peak current of the non-linear load.

[0098] For example, Figure 6 , Figure 7 For example, when the inverter 30 is controlled by only a given reference voltage Vref, the output voltage of the inverter 30, the current of the nonlinear load 61, and the voltage of the nonlinear load 61 obtained by simulation are as follows: Figure 8 As shown, Vin * is the output voltage of the inverter, I1 * is the current of the nonlinear load, V0 * It is the voltage of the nonlinear load, where the output voltage of the inverter is a sine wave. The current of the nonlinear load will have a pulse current at the maximum and minimum moments of the output voltage of the inverter, which may easily cause the nonlinear load to overcurrent and trigger the overcurrent protection.

[0099] Based on the technical solution disclosed in this application, the voltage suppression coefficient B is determined by the peak current Ipeak of the nonlinear load to adjust the suppression voltage Vref * The magnitude of the suppression voltage Vref * And the reference voltage Vref controls the inverter, such as Figure 3 and Fig. 9Assume that the voltage suppression coefficient B = 0.15, then the simulation waveform is as follows Fig.10 As shown, Vin is the output voltage of the inverter after suppression, I1 is the current of the nonlinear load after suppression, and V0 is the voltage of the nonlinear load after suppression. Fig.10 and Figure 8 Put them in the same coordinate system, such as Fig.11 As shown, before and after the suppression, the voltage of the nonlinear load is basically unchanged, and the current peak of the nonlinear load after the suppression is reduced. Therefore, the present application injects an adjustable suppression voltage Vref * , forming a saddle wave waveform, thereby reducing the current of the nonlinear load and preventing the occurrence of overcurrent.

[0100] Therefore, in the related art, when the inverter outputs a sinusoidal voltage and supplies power to a nonlinear load through the sinusoidal voltage, at the peak and valley moments of the inverter output voltage (i.e., the maximum and minimum moments), due to the circuit characteristics of low impedance and high voltage difference between the power supply and the load, pulse overcurrent is very likely to occur, which can easily trigger the nonlinear load overcurrent protection shutdown. The control strategy of superimposed suppression voltage proposed in this application can reduce the voltage value of the inverter output voltage at the peak and valley moments, thereby achieving the effect of reducing the peak current of the nonlinear load.

[0101] In summary, according to the control method of the inverter of the embodiment of the present invention, the peak current of the nonlinear load in the previous cycle is first obtained, and the suppression voltage of the current cycle is determined based on the peak current, and the voltage amplitude of the reference voltage is suppressed based on the suppression voltage to obtain the given voltage of the current cycle, and then the inverter is controlled according to the given voltage to suppress the peak current of the nonlinear load. Therefore, the method determines the suppression voltage based on the peak current of the nonlinear load in the previous cycle to suppress the voltage amplitude of the reference voltage, thereby reducing the peak current of the nonlinear load and avoiding overcurrent of the nonlinear load when the inverter directly supplies power to the nonlinear load.

[0102] Corresponding to the above embodiment, the present invention further proposes a control device for an inverter.

[0103] In one embodiment of the present invention, the inverter is connected to the non-linear load and is used to convert direct current into alternating current to supply power to the non-linear load.

[0104] Specifically, an inverter is a converter that converts DC power (such as power from batteries or storage bottles) into constant frequency and voltage or frequency and voltage regulated AC power. It can be composed of units such as inverter bridges and filter circuits, and is widely used in technical fields such as air conditioning and home theaters.

[0105] exist Figure 2In the illustrated embodiment, the inverter 30 is applied to a photovoltaic energy storage system, and the connection between the inverter 30 and the nonlinear load 61 is shown in the figure. During operation, when the inverter 30 is in the grid-connected mode, the grid-connected switch 40 is controlled to be closed so that the inverter 30 is connected to the grid 50, and electric energy flows between the inverter 30, the grid 50 and the nonlinear load 61. When the inverter 30 is in the off-grid mode, the grid-connected switch 40 is controlled to be opened so that the inverter 30 is disconnected from the grid 50, and the AC power output by the inverter 30 supplies power to the nonlinear load 61.

[0106] It is understandable that the inverter 30 may be provided with only an inverter circuit to convert direct current into alternating current. In addition to the DC / AC single-phase inverter bridge 32, the inverter circuit may also adopt a three-phase inverter circuit, etc., which is not limited here. The nonlinear load 61 is only a type of device 60. In addition to the nonlinear load 61, the device 60 may also be provided with a linear load and other device types. Among them, a linear load refers to a pure resistive load whose voltage and current are completely sinusoidal curves. A nonlinear load refers to a load in an electronic circuit whose voltage and current are not in a linear relationship. The nonlinear load includes not only a rectifier load, but also other loads, such as a motor, and the motor must use a sinusoidal voltage, etc. Among them, a nonlinear rectifier load refers to a load containing a rectifier device, such as a resistive load, a capacitive load, and an inductive load.

[0107] like Fig.12 As shown, the inverter control device according to the embodiment of the present invention includes: an acquisition module 80 and a control module 90 .

[0108] The acquisition module 80 is used to acquire the peak current of the nonlinear load in the previous cycle. The control module 90 is used to determine the suppression voltage of the current cycle based on the peak current, and suppress the voltage amplitude of the reference voltage based on the suppression voltage to obtain the given voltage of the current cycle, and control the inverter according to the given voltage to suppress the peak current of the nonlinear load.

[0109] According to one embodiment of the present invention, the control module 90 determines the suppression voltage of the current cycle based on the peak current, and is specifically used to: determine the voltage suppression coefficient of the current cycle based on the peak current; obtain the product of the voltage suppression coefficient and the reference suppression voltage to obtain the suppression voltage of the current cycle.

[0110] According to one embodiment of the present invention, the control module 90 determines the voltage suppression coefficient of the current cycle based on the peak current, and is specifically used for: when the peak current is less than or equal to the first current threshold, determining the voltage suppression coefficient to be zero; when the peak current is greater than the first current threshold and less than or equal to the second current threshold, determining the voltage suppression coefficient based on the peak current and the linear mapping relationship between the peak current and the voltage suppression coefficient; when the peak current is greater than the second current threshold, determining the voltage suppression coefficient to be a preset value; wherein the preset value is greater than zero, and the second current threshold is greater than the first current threshold.

[0111] According to an embodiment of the present invention, the voltage suppression coefficient ranges from [0, 0.25].

[0112] According to one embodiment of the present invention, the control module 90 suppresses the voltage amplitude of the reference voltage based on the suppression voltage to obtain a given voltage of the current cycle, and is specifically used to: obtain the voltage difference between the reference voltage and the suppression voltage to obtain the given voltage of the current cycle.

[0113] According to an embodiment of the present invention, the reference voltage is a sinusoidal wave voltage, and the reference suppression voltage is a continuous alternating voltage or a discontinuous alternating voltage.

[0114] According to an embodiment of the present invention, the reference suppression voltage is one of a sine wave voltage, a square wave voltage, a trapezoidal wave voltage and a triangle wave voltage.

[0115] According to an embodiment of the present invention, when the reference suppression voltage is a continuous sinusoidal voltage, the frequency of the reference suppression voltage is 3*n times the frequency of the reference voltage, where n is a positive integer.

[0116] According to one embodiment of the present invention, the control module 90 controls the inverter according to a given voltage, and is specifically used to: obtain the output voltage of the previous cycle inverter; obtain the voltage difference between the given voltage and the output voltage; determine the modulation signal of the inverter based on the voltage difference; and generate a PWM signal based on the modulation signal to control the inverter.

[0117] According to one embodiment of the present invention, the control module 90 determines the modulation signal of the inverter based on the voltage difference, and is specifically used to: input the difference into the PR controller and the repetitive controller respectively to obtain the first control voltage and the second control voltage; obtain the sum of the first control voltage and the second control voltage to obtain the modulation signal.

[0118] It should be noted that for details not disclosed in the inverter control device of the embodiment of the present invention, please refer to the details disclosed in the inverter control method of the above embodiment of the present invention, and the details will not be repeated here.

[0119] According to the control device of the inverter of the embodiment of the present invention, the peak current of the nonlinear load in the previous cycle is obtained by the acquisition module, the control module determines the suppression voltage of the current cycle based on the peak current, and suppresses the voltage amplitude of the reference voltage based on the suppression voltage to obtain the given voltage of the current cycle, and controls the inverter according to the given voltage to suppress the peak current of the nonlinear load. Thus, the device determines the suppression voltage based on the peak current of the nonlinear load in the previous cycle to suppress the voltage amplitude of the reference voltage, thereby reducing the peak current of the nonlinear load and avoiding the overcurrent of the nonlinear load when the inverter directly supplies power to the nonlinear load.

[0120] Corresponding to the above embodiment, the present invention also proposes a controller.

[0121] like Fig.13 As shown, the controller 100 of the embodiment of the present invention includes: a memory 110, a processor 120, and a program stored in the memory 110 and executable on the processor 120. When the processor 120 executes the program, the above-mentioned inverter control method is implemented. The controller 100 is the control center of the system, which is used to command various parts of the system to work in a coordinated manner and ensure that the system operates and processes in an orderly manner according to pre-defined goals and steps.

[0122] According to the controller of the embodiment of the present invention, when the processor executes the control program of the inverter, the above-mentioned control method of the inverter is implemented. Based on the above-mentioned control method of the inverter, the suppression voltage is determined according to the peak current of the nonlinear load in the previous cycle to suppress the voltage amplitude of the reference voltage, thereby reducing the peak current of the nonlinear load and avoiding overcurrent of the nonlinear load when the inverter directly supplies power to the nonlinear load.

[0123] Corresponding to the above embodiment, the present invention also proposes a photovoltaic energy storage system.

[0124] like Fig.14 As shown, the photovoltaic energy storage system 200 of the embodiment of the present invention may include the inverter control device 210 described above, or, as shown in FIG. Fig.15 As shown, the photovoltaic energy storage system 200 of the embodiment of the present invention includes the above-mentioned controller 100. The photovoltaic energy storage system 200 is also called a solar photovoltaic energy storage power generation system, which is a power generation system composed of photovoltaic equipment and energy storage equipment.

[0125] According to the photovoltaic energy storage system of the embodiment of the present invention, based on the control device of the above-mentioned inverter or the above-mentioned controller, the suppression voltage is determined according to the peak current of the non-linear load in the previous cycle to suppress the voltage amplitude of the reference voltage, thereby reducing the peak current of the non-linear load and avoiding overcurrent of the non-linear load when the inverter directly supplies power to the non-linear load.

[0126] Corresponding to the above embodiment, the present invention also proposes a photovoltaic energy storage system.

[0127] like Fig.16 As shown, the photovoltaic energy storage system of the embodiment of the present invention includes: a photovoltaic component 220, an inverter 30 and a controller 100.

[0128] The DC side of the inverter 30 is connected to the photovoltaic module 220, and the AC side of the inverter 30 is connected to the power grid 50 and the load 60. The inverter 30 is used to convert the DC power of the photovoltaic module 220 into AC power and feed it to the power grid 50 and / or supply power to the load 60, wherein the load 60 includes a nonlinear load 61. The controller 100 is connected to the inverter 30. The controller 30 is used to obtain the peak current of the nonlinear load 61 in the previous cycle when the inverter 30 is off-grid, and determine the suppression voltage of the current cycle based on the peak current, and suppress the voltage amplitude of the reference voltage based on the suppression voltage to obtain a given voltage of the current cycle, and control the inverter 30 according to the given voltage to suppress the peak current of the nonlinear load.

[0129] Specifically, the photovoltaic energy storage system, also known as the solar photovoltaic energy storage power generation system, is a power generation system composed of photovoltaic equipment and energy storage equipment. Photovoltaic assembly 220, also known as solar panel, is the core part of the photovoltaic energy storage system, and its function is to convert solar energy into electrical energy. Inverter 30 is a converter that converts DC power into constant frequency and voltage or frequency and voltage regulated AC power. The power grid 50 is a whole composed of substations and transmission and distribution lines of various voltages in the power system. It includes three units: substation, transmission, and distribution. Its task is to transmit and distribute electrical energy and change the voltage. Load 60 is a device for converting electrical energy into other forms of energy, and may include resistors, motors, etc. Among them, the connection between inverter 30 and photovoltaic assembly 220, power grid 50 and load 60 can refer to Figure 2 As shown, the photovoltaic assembly 220 includes two photovoltaic panels. Figure 2 The content will not be repeated here.

[0130] According to the photovoltaic energy storage system of the embodiment of the present invention, the DC side of the inverter is connected to the photovoltaic module, the AC side of the inverter is connected to the power grid and the load, and the controller is connected to the inverter, wherein the load includes a nonlinear load. The inverter converts the DC power of the photovoltaic module into AC power and feeds it to the power grid and / or supplies power to the load. When the inverter is off-grid, the controller obtains the peak current of the nonlinear load in the previous cycle, and determines the suppression voltage of the current cycle based on the peak current, and suppresses the voltage amplitude of the reference voltage based on the suppression voltage to obtain the given voltage of the current cycle, and controls the inverter according to the given voltage to suppress the peak current of the nonlinear load. The photovoltaic energy storage system determines the suppression voltage based on the peak current of the nonlinear load in the previous cycle to suppress the voltage amplitude of the reference voltage, thereby reducing the peak current of the nonlinear load and avoiding overcurrent of the nonlinear load when the inverter directly supplies power to the nonlinear load.

[0131] It should be noted that the logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as a sequenced list of executable instructions for implementing logical functions, and can be specifically implemented in any computer-readable medium for use by an instruction execution system, device or apparatus (such as a computer-based system, a system including a processor, or other system that can fetch instructions from an instruction execution system, device or apparatus and execute instructions), or in combination with these instruction execution systems, devices or apparatuses. For the purposes of this specification, "computer-readable medium" can be any device that can contain, store, communicate, propagate or transmit a program for use by an instruction execution system, device or apparatus, or in combination with these instruction execution systems, devices or apparatuses. More specific examples of computer-readable media (a non-exhaustive list) include the following: an electrical connection portion with one or more wirings (electronic device), a portable computer disk box (magnetic device), a random access memory (RAM), a read-only memory (ROM), an erasable and programmable read-only memory (EPROM or flash memory), an optical fiber device, and a portable compact disk read-only memory (CDROM). In addition, the computer-readable medium may even be paper or other suitable medium on which the program is printed, since the program may be obtained electronically, for example, by optically scanning the paper or other medium and then editing, interpreting or processing in other suitable ways if necessary, and then stored in a computer memory.

[0132] It should be understood that the various parts of the present invention can be implemented by hardware, software, firmware or a combination thereof. In the above-mentioned embodiments, a plurality of steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented by hardware, as in another embodiment, it can be implemented by any one of the following technologies known in the art or their combination: a discrete logic circuit having a logic gate circuit for implementing a logic function for a data signal, a dedicated integrated circuit having a suitable combination of logic gate circuits, a programmable gate array (PGA), a field programmable gate array (FPGA), etc.

[0133] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0134] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0135] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0136] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A control method for an inverter, characterized in that: The inverter is connected to a nonlinear load and is used to convert direct current into alternating current to supply power to the nonlinear load. The method includes: Obtaining the peak current of the nonlinear load in the previous cycle; determining a suppression voltage of the current cycle based on the peak current; Based on the suppression voltage, the reference voltage is suppressed in voltage amplitude to obtain a given voltage of the current cycle; The inverter is controlled according to the given voltage to suppress the peak current of the nonlinear load.

2. The method according to claim 1, characterized in that The step of determining the suppression voltage of the current cycle based on the peak current comprises: Determining a voltage suppression coefficient of the current cycle based on the peak current; The product of the voltage suppression coefficient and the reference suppression voltage is obtained to obtain the suppression voltage of the current cycle.

3. The method according to claim 2, characterized in that The step of determining the voltage suppression coefficient of the current cycle based on the peak current includes: When the peak current is less than or equal to a first current threshold, determining that the voltage suppression coefficient is zero; When the peak current is greater than the first current threshold and less than or equal to the second current threshold, determining the voltage suppression coefficient according to the peak current and a linear mapping relationship between the peak current and the voltage suppression coefficient; When the peak current is greater than the second current threshold, the voltage suppression coefficient is determined to be a preset value; wherein the preset value is greater than zero, and the second current threshold is greater than the first current threshold.

4. The method according to claim 2, characterized in that: The voltage suppression coefficient ranges from [0, 0.25].

5. The method according to claim 1, characterized in that The step of suppressing the voltage amplitude of the reference voltage based on the suppression voltage to obtain a given voltage of the current cycle includes: The voltage difference between the reference voltage and the suppression voltage is obtained to obtain the given voltage of the current cycle.

6. The method according to any one of claims 2 to 5, characterized in that: The reference voltage is a sinusoidal wave voltage, and the reference suppression voltage is a continuous alternating voltage or a discontinuous alternating voltage.

7. The method according to claim 6, characterized in that The reference suppression voltage is one of a sine wave voltage, a square wave voltage, a trapezoidal wave voltage and a triangle wave voltage.

8. The method according to claim 7, characterized in that When the reference suppression voltage is a continuous sinusoidal voltage, the frequency of the reference suppression voltage is 3*n times the frequency of the reference voltage, where n is a positive integer.

9. The method according to claim 1, characterized in that: The controlling the inverter according to the given voltage includes: Obtain the output voltage of the inverter in the previous cycle; Obtaining a voltage difference between the given voltage and the output voltage; determining a modulation signal for the inverter based on the voltage difference; A PWM signal is generated based on the modulation signal to control the inverter.

10. The method according to claim 9, characterized in that The step of determining a modulation signal of the inverter based on the voltage difference comprises: Inputting the difference into the PR controller and the repetitive controller respectively to obtain a first control voltage and a second control voltage; The sum of the first control voltage and the second control voltage is obtained to obtain the modulation signal.

11. A control device for an inverter, characterized in that: The inverter is connected to a non-linear load and is used to convert direct current into alternating current to supply power to the non-linear load. The device comprises: An acquisition module, used for acquiring the peak current of the nonlinear load in the previous cycle; A control module is used to determine the suppression voltage of the current cycle based on the peak current, and to suppress the voltage amplitude of the reference voltage based on the suppression voltage to obtain a given voltage of the current cycle, and to control the inverter according to the given voltage to suppress the peak current of the nonlinear load.

12. A controller, characterized in that: include: A memory, a processor, and a program stored in the memory and executable on the processor, wherein when the processor executes the program, the control method for the inverter according to any one of claims 1 to 10 is implemented.

13. A photovoltaic energy storage system, characterized in that: The invention comprises the control device of the inverter according to claim 11, or the controller according to claim 12.

14. A photovoltaic energy storage system, characterized in that: include: Photovoltaic panels; An inverter, wherein the DC side of the inverter is connected to the photovoltaic module, and the AC side of the inverter is connected to the power grid and the load, and is used to convert the DC power of the photovoltaic module into AC power and feed it to the power grid and / or supply power to the load, wherein the load includes a nonlinear load; A controller is connected to the inverter and is used to obtain the peak current of the nonlinear load in the previous cycle when the inverter is off-grid, determine the suppression voltage of the current cycle based on the peak current, and suppress the voltage amplitude of the reference voltage based on the suppression voltage to obtain a given voltage of the current cycle, and control the inverter according to the given voltage to suppress the peak current of the nonlinear load.

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