Inverter control method and device, computing equipment and machine readable storage medium

Abstract

The embodiment of the invention discloses an inverter control method and device, computing equipment and a machine readable storage medium, and belongs to the field of photovoltaic grid connection. The control method of the inverter comprises the following steps: determining a first projection component of a grid-connected current on a d axis and a second projection component of the grid-connected current on a q axis according to an output phase angle of a phase-locked loop; obtaining a first current reference value component and a second current reference value component; acquiring a first modulation signal output by the d-axis current regulator based on the first projection component, the first current reference value and the first control parameter; according to the voltage component of the access point voltage on the q axis and the disturbance transfer function of the phase-locked loop, a suppression feedback signal is obtained; acquiring a second modulation signal output by the q-axis current regulator based on the second projection component, the second current reference value component, the suppression feedback signal and the second control parameter; and controlling the switch tube according to the first modulation signal and the second modulation signal.

Description

Technical Field

[0001] The present invention relates to the field of photovoltaic grid-connected power generation, and in particular to a control method, device, computing equipment and machine-readable storage medium for an inverter. Background Art

[0002] With the rapid development of new energy technologies, the proportion of distributed photovoltaics connected to the grid is increasing, making the power electronics trend of the grid more and more significant. Grid-connected inverters have the advantages of high controllability and high efficiency. Photovoltaics convert direct current into alternating current through grid-connected inverters, and then the alternating current converted by photovoltaics is connected to the grid. The control loop of the grid-connected inverter has a wide time scale range, and the interaction between the inverter and the grid impedance will affect the stability of the grid-connected inverter.

[0003] After a large number of distributed photovoltaics are connected to the grid, the interaction between photovoltaics and grid impedance transmission can easily cause the grid-connected system to generate broadband oscillations, thereby threatening the security of the grid system. In order to suppress the broadband oscillation of the grid-connected inverter, the control loop structure of the grid-connected inverter is usually changed or an additional auxiliary control loop is added, which makes the control structure of the grid-connected inverter too complicated and makes the control of the grid-connected inverter too difficult. In addition, adding an additional auxiliary control loop also requires adding additional sensors to sample additional state variables, which further makes the control structure of the grid-connected inverter too complicated and makes the control of the grid-connected inverter too difficult. Summary of the invention

[0004] The purpose of the embodiments of the present invention is to provide a control method, device, computing equipment and machine-readable storage medium for an inverter, so as to solve the problem that the control structure of the inverter is too complicated.

[0005] In order to achieve the above-mentioned purpose, the first aspect of the present application provides a control method of an inverter, wherein the inverter includes a switch tube, a phase-locked loop, a d-axis current regulator and a q-axis current regulator, the switch tube is respectively connected to the input end of the d-axis current regulator and the input end of the q-axis current regulator through the phase-locked loop, the output end of the d-axis current regulator and the output end of the q-axis current regulator are both connected to the switch tube, the inverter is connected to the power grid through an access point, and the control method of the inverter includes:

[0006] Determine a first projection component of the grid-connected current on the d-axis and a second projection component on the q-axis according to an output phase angle of the phase-locked loop;

[0007] Obtaining a first current reference value component and a second current reference value component, wherein the first current reference value is a component of the grid-connected current reference value on the d-axis, and the second current reference value component is a component of the grid-connected current reference value on the q-axis;

[0008] Acquire a first modulation signal output by the d-axis current regulator based on the first projection component, the first current reference value and the first control parameter, wherein the first control parameter is a control parameter of the d-axis current regulator;

[0009] A suppression feedback signal is obtained according to a voltage component of the access point voltage on the q axis and a disturbance transfer function of the phase-locked loop;

[0010] Obtaining a second modulation signal output by the q-axis current regulator based on the second projection component, the second current reference value component, the suppression feedback signal and the second control parameter, wherein the second control parameter is a control parameter of the q-axis current regulator, and the first control parameter and the second control parameter are asymmetric control parameters;

[0011] The switch tube is controlled according to the first modulation signal and the second modulation signal.

[0012] The beneficial effects of this application are:

[0013] Without changing the control loop structure of the inverter or adding additional auxiliary control loops, the d-axis and q-axis adopt asymmetric control parameters to improve the system's oscillation suppression capability, avoiding the inverter's control structure from being too complicated. In addition, the q-axis adopts an asymmetric design that introduces a suppression feedback signal to offset the negative impact of the phase-locked loop on the inverter's broadband oscillation, further improving the system's oscillation suppression capability while simplifying the inverter's control structure.

[0014] Other features and advantages of the embodiments of the present invention will be described in detail in the subsequent detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The accompanying drawings are used to provide a further understanding of the embodiments of the present invention and constitute a part of the specification. Together with the following specific implementations, they are used to explain the embodiments of the present invention, but do not constitute a limitation on the embodiments of the present invention. In the accompanying drawings:

[0016] Figure 1 An example diagram showing a control structure of an inverter provided in an embodiment of the present application is shown;

[0017] Figure 2 A flow chart of a method for controlling an inverter provided in an embodiment of the present application is shown;

[0018] Figure 3 A control structure diagram of a phase-locked loop provided in an embodiment of the present application is shown;

[0019] Figure 4 A schematic diagram of the structure of the d-axis current control inner loop provided in an embodiment of the present application is shown;

[0020] Figure 5A schematic diagram of the structure of the q-axis current control inner loop provided in an embodiment of the present application is shown;

[0021] Figure 6 The transfer function model of the inverter provided in the embodiment of the present application is shown;

[0022] Figure 7 An example graph of a characteristic value curve of a grid impedance of 32 mH provided in an embodiment of the present application is shown;

[0023] Figure 8 An example graph of a characteristic value curve of a power grid impedance of 35 mH provided in an embodiment of the present application is shown;

[0024] Fig. 9 An example diagram of a grid-connected current waveform with a grid impedance of 32 mH provided in an embodiment of the present application is shown;

[0025] Fig.10 An example diagram of a grid-connected current waveform with a grid impedance of 35 mH provided in an embodiment of the present application is shown;

[0026] Fig.11 A schematic structural diagram of a control device for an inverter provided in an embodiment of the present application is shown. DETAILED DESCRIPTION

[0027] The specific implementation of the embodiment of the present invention will be described in detail below in conjunction with the accompanying drawings in the embodiment of the present invention. It should be understood that the specific implementation described here is only used to illustrate and explain the embodiment of the present invention, and is not used to limit the embodiment of the present invention.

[0028] The components of the embodiments of the present invention generally described and shown in the drawings herein may be arranged and designed in a variety of different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0029] Hereinafter, the terms "including", "having" and their cognates, which may be used in various embodiments of the present invention, are intended only to indicate specific features, numbers, steps, operations, elements, components or combinations of the foregoing items, and should not be understood as first excluding the existence of one or more other features, numbers, steps, operations, elements, components or combinations of the foregoing items or adding the possibility of one or more features, numbers, steps, operations, elements, components or combinations of the foregoing items.

[0030] Furthermore, the terms “first”, “second”, “third”, etc. are merely used for distinguishing descriptions and are not to be understood as indicating or implying relative importance.

[0031] Unless otherwise defined, all terms (including technical terms and scientific terms) used herein have the same meanings as those generally understood by those skilled in the art to which the various embodiments of the present invention belong. The terms (such as those defined in generally used dictionaries) will be interpreted as having the same meanings as the contextual meanings in the relevant technical field and will not be interpreted as having idealized meanings or overly formal meanings unless clearly defined in the various embodiments of the present invention.

[0032] Example 1

[0033] See also Figure 1 , Figure 1 An example diagram of a control structure of an inverter provided in an embodiment of the present application is shown.

[0034] The inverter includes a switch tube, a phase-locked loop, a d-axis current regulator and a q-axis current regulator. The switch tube is connected to the input end of the d-axis current regulator and the input end of the q-axis current regulator respectively through the phase-locked loop. The output end of the d-axis current regulator and the output end of the q-axis current regulator are both connected to the switch tube. The inverter is connected to the power grid through an access point. The control method of the inverter includes:

[0035] The inverter in this embodiment also includes other components, which are set according to actual needs and are not limited here. For ease of understanding, the other components in the embodiment of this application include DC side capacitors, first filter inductors, second filter inductors and filter capacitors, etc., which are not limited here. The switch tube is the inverter bridge of the inverter, I ds is the current source of the inverter, C dc is the DC side capacitance of the inverter, U dc is the DC bus voltage of the inverter, u inv is the output voltage of the inverter switch tube, i1 is the inductor current on the inverter side, L1 is the first filter inductor, L2 is the second filter inductor, C f For filter capacitors, L1, C f and L2 form an LCL (Inductor-Capacitor-Inductor) filter, R d is a passive damping resistor.

[0036] The inverter is connected to the grid through the access point, i2 is the inverter output grid current, Z g is the grid impedance; U pcc is the voltage at PCC point, U g is the grid voltage, wherein the PPC point is a point in the power system where multiple users or devices are connected together, which is the access point of the phase-locked loop in this embodiment. dcref is the given value of DC bus voltage, udc is the actual voltage across the DC capacitor; G v (s) is the control parameter of the current inner loop PI controller; I 2dref I is the d-axis reference value component of the grid-connected current reference value; 2qref is the q-axis reference value component of the grid-connected current reference value; i 2d 、i 2q are the projection components of the grid-connected current on the d and q axes respectively; G id (s) is the first control parameter of the d-axis current regulator, G iq (s) is the second control parameter of the q-axis current regulator; G PLL (s) represents the small signal disturbance transfer function model of the phase-locked loop; I 2d0 is the preset conversion coefficient, i.e., the steady-state value of the grid-connected current on the d-axis; K is the feedback gain; G g,c V is the equivalent conversion coefficient between the q-axis voltage in the grid dq coordinate system and the q-axis voltage in the controller dq coordinate system. Md is the first modulation signal output by the d-axis current regulator, V Mq is the second modulation signal output by the q-axis current regulator, K PWM is the pulse width modulation gain; θ is the output phase angle of the phase-locked loop (PLL).

[0037] See also Figure 2 , Figure 2 A flow chart of a method for controlling an inverter provided in an embodiment of the present application is shown.

[0038] S110, determining a first projection component of the grid-connected current on the d-axis and a second projection component on the q-axis according to an output phase angle of the phase-locked loop.

[0039] The grid-connected current refers to the current when the output current of the inverter is connected to the grid after the inverter is connected to the grid. Usually, the grid-connected current is represented by the ABC three-phase coordinate system, where A, B and C represent three phases with a phase difference of 120 degrees, to represent the phase and amplitude of physical quantities such as current and voltage. The dq coordinate system is also called the rotating coordinate system. The d-axis (direct axis) is the coordinate axis aligned with the direction of the rotating magnetic field, and the q-axis (quadrature axis) is the coordinate axis perpendicular to the d-axis, and is usually used to represent the part perpendicular to the magnetic field.

[0040] According to the output phase angle of the phase-locked loop, the first projection component of the grid-connected current on the d-axis and the second projection component on the q-axis are determined. The ABC three-phase coordinates of the grid-connected current are converted into dq coordinates, the output angle of the phase-locked loop is used as the dp-axis reference angle, the grid-connected current is decomposed into the dp-axis, and the three-phase signal is converted into a rotating DC coordinate system, thereby simplifying the complexity of analysis and control.

[0041] S120, obtaining a first current reference value component and a second current reference value component, wherein the first current reference value is a component of the grid-connected current reference value on the d-axis, and the second current reference value component is a component of the grid-connected current reference value on the q-axis.

[0042] The current reference value refers to the current value used to control the target in the electrical system. The grid-connected current reference value is decomposed into the dp axis to obtain the first current reference value component and the second current reference value component. The first current reference value is the component of the grid-connected current reference value on the d axis, and the second current reference value component is the component of the grid-connected current reference value on the q axis.

[0043] In an embodiment of the present application, obtaining a first current reference value component and a second current reference value component includes:

[0044] Construct the equation relationship between the DC side and the AC side of the inverter;

[0045] Constructing a first small signal model between a voltage outer loop and a current inner loop reference value of the inverter;

[0046] According to the equation relationship and the first small signal model, a second small signal model of the current inner loop is obtained;

[0047] Based on the second small signal model, a first current reference value component and a second current reference value component are obtained.

[0048] The small-signal model is a linear approximation model used to describe and analyze nonlinear systems near a specific operating point. When the signal changes slightly, the small-signal model is used to simplify the analysis of complex nonlinear systems. For ease of understanding, the small-signal model is used for calculation in this embodiment to construct an equation relationship between the DC side and the AC side of the inverter, and the equation relationship between the DC side and the AC side is converted into a matrix form:

[0049]

[0050]

[0051] Among them, U dc is the DC side voltage of the inverter, I ds is the current source of the inverter, U cmis the AC side voltage of the inverter, i 1d is the steady-state value of the inductor current on the d-axis on the inverter side, i 1q is the steady-state value of the inductor current on the q axis on the inverter side, s is the state variable, V Md is the first modulation signal output by the d-axis current regulator, V Mq is the second modulation signal output by the q-axis current regulator, C dc is the DC side capacitance of the inverter, and Δ is a small signal quantity, that is, a variable with very small changes.

[0052] Construct the first small signal model between the voltage outer loop and the current inner loop reference value of the inverter:

[0053]

[0054] Among them, I 2dref is the d-axis reference value component of the grid-connected current reference value, U dc is the DC side voltage of the inverter, G v (s) is the control parameter of the current inner loop PI controller, s is the state variable, and Δ is a small signal variable, that is, a variable with very small changes.

[0055] According to the equation relationship and the first small signal model, the second small signal model of the current inner loop is obtained:

[0056]

[0057] Among them, I 2dref is the d-axis reference value component of the grid-connected current reference value, U dc is the DC side voltage of the inverter, I ds is the current source of the inverter, U cm is the AC side voltage of the inverter, i 1d is the current component of the inductor current on the inverter side on the d axis, i 1q is the current component of the inductor current on the inverter side on the q axis, s is the state variable, V Md is the first modulation signal output by the d-axis current regulator, V Mq is the second modulation signal output by the q-axis current regulator, C dc is the DC side capacitance of the inverter, V Md0 is the steady-state value of the first signal corresponding to the first modulation signal, V Mq0 is the steady-state value of the second signal corresponding to the second modulation signal, G v (s) is the control parameter of the current inner loop PI controller, s is the state variable, and Δ is a small signal variable, that is, a variable with very small changes.

[0058] i 1d 、i 1q 、VMd0 and V Mq0 All the calculated quantities of are constant values, which are not described in detail here. Based on the second small signal model, the first current reference value component and the second current reference value component are obtained. In this embodiment, the second current reference value component is zero, which is not described in detail here.

[0059] In the embodiment of the present application, constructing an equation relationship between the DC side and the AC side of the inverter includes:

[0060] Construct the second small signal model of the DC side of the inverter;

[0061] Construct the third smallest signal model of the output power of the switch tube;

[0062] Based on the second small signal model and the third small signal model, an equation relationship between the DC side and the AC side of the inverter is constructed.

[0063]

[0064] Among them, ΔP in is the output power of the inverter, ΔP Cdc is the output power of the DC side capacitor, I 2dref is the d-axis reference value component of the grid-connected current reference value, U dc is the DC side voltage of the inverter, C dc is the DC side capacitance of the inverter, and Δ is a small signal quantity, that is, a variable with very small changes.

[0065] Construct the third small signal model of the output power of the switch tube:

[0066]

[0067] Among them, P e is the third small signal model of the output power of the switch tube, u invd is the component of the inverter switch output voltage on the d-axis, u invq is the component of the inverter switch output voltage on the q axis, i 1d is the current component of the inductor current on the inverter side on the d axis, i 1q is the current component of the inductor current on the inverter side on the q axis, V Md is the first modulation signal output by the d-axis current regulator, V Mq is the second modulation signal output by the q-axis current regulator, U dc is the DC side voltage of the inverter, U cm is the AC side voltage of the inverter.

[0068] Based on the second small signal model and the third small signal model, an equation relationship between the DC side and the AC side of the inverter is constructed.

[0069] S130, obtaining a first modulation signal output by a d-axis current regulator based on a first projection component, a first current reference value, and a first control parameter, wherein the first control parameter is a control parameter of the d-axis current regulator.

[0070] A first modulation signal output by the d-axis current regulator based on the first projection component, the first current reference value and the first control parameter is obtained. For ease of understanding, in the embodiment of the present application, both the d-axis current regulator and the q-axis current regulator are differential controllers, and the control parameter of the d-axis current regulator is G id (s) = k pd +k id / s, where G id (s) is the first control parameter, k pd is the proportionality factor of the d-axis current regulator, k id is the integral coefficient of the d-axis current regulator, s is the state variable. The first projection component and the first current reference value are used as state variables and substituted into the first control parameter of the d-axis current regulator to obtain the first modulation signal output by the d-axis current regulator.

[0071] S140, obtaining a suppression feedback signal according to the voltage component of the access point voltage on the q-axis and the disturbance transfer function of the phase-locked loop.

[0072] In this embodiment, a PLL is introduced on the q-axis to affect the suppression feedback amount, offsetting the effect of the phase-locked loop on the q-axis. Specifically, according to the voltage component of the access point voltage on the q-axis and the disturbance transfer function of the phase-locked loop, the voltage component is used as the state variable of the disturbance transfer function to obtain the suppression feedback signal, where the access point is the PCC point in the figure. The q-axis adopts an asymmetric design that introduces a suppression feedback signal to offset the negative impact of the phase-locked loop on the broadband oscillation of the inverter, further improving the oscillation suppression capability of the system.

[0073] In an embodiment of the present application, a suppression feedback signal is obtained according to a voltage component of the access point voltage on the q-axis and a disturbance transfer function of a phase-locked loop, including:

[0074] According to the disturbance transfer function of the phase-locked loop, the current steady-state value of the grid-connected current on the d-axis, the preset conversion coefficient and the feedback gain of the phase-locked loop, the voltage component of the access point voltage on the q-axis is converted to obtain a suppressed feedback signal of the q-axis current regulator, wherein the preset conversion coefficient is a conversion coefficient between the grid voltage and the phase-locked loop voltage.

[0075] See also Figure 3 , Figure 3 A control structure schematic diagram of a phase-locked loop provided in an embodiment of the present application is shown.

[0076] In this embodiment, the phase-locked loop adopts the control result of the PI (Proportional Integral) controller, ω g is the angular frequency of the power grid, ω0 is the output angular frequency of the phase-locked loop, and l / s represents the integral link, that is, the input l / s is integrated. The small signal disturbance transfer function excited by the phase-locked loop is:

[0077]

[0078] Among them, G PLL (s) is the disturbance transfer function of the phase-locked loop, H PI (s) is the control parameter of the PI controller of the phase-locked loop, s is the state variable, V m0 is the steady-state value of the grid voltage.

[0079] According to the disturbance transfer function of the phase-locked loop, the current steady-state value of the grid-connected current on the d-axis, the preset conversion coefficient and the feedback gain of the phase-locked loop, the voltage component of the access point voltage on the q-axis is converted. Specifically, the preset conversion coefficient is the conversion coefficient between the grid voltage and the phase-locked loop voltage. The voltage component is converted based on the feedback gain and the preset conversion coefficient to obtain the converted voltage component. The converted voltage component is substituted as the state component and multiplied with the current steady-state value of the grid-connected current on the d-axis to obtain the suppressed feedback signal of the q-axis current regulator. The q-axis adopts an asymmetric design that introduces a suppressed feedback signal to offset the negative impact of the phase-locked loop on the broadband oscillation of the inverter.

[0080] S150, obtaining a second modulation signal output by the q-axis current regulator based on the second projection component, the second current reference value component, the suppression feedback signal and the second control parameter, wherein the second control parameter is a control parameter of the q-axis current regulator, and the first control parameter and the second control parameter are asymmetric control parameters.

[0081] The second modulation signal output by the q-axis current regulator based on the second projection component, the second current reference value component, the suppression feedback signal and the second control parameter is obtained. In this embodiment, the control parameter of the q-axis current regulator is G iq (s) = k pq +k iq / s, where G iq (s) is the second control parameter, k pq is the proportional coefficient of the q-axis current regulator, k iq is the integral coefficient of the q-axis current regulator, and s is the state variable.

[0082] The second projection component, the second current reference value component, and the suppression feedback signal are used as state variables. The first projection component and the first current reference value are used as state variables and substituted into the second control parameter of the q-axis current regulator to obtain the second modulation signal output by the q-axis current regulator.

[0083] In this embodiment, the first control parameter and the second control parameter are asymmetric control parameters, that is, the proportional coefficient and the integral coefficient of the q-axis current regulator and the d-axis current regulator are asymmetric coefficients. The d-axis and the q-axis use asymmetric control parameters to suppress the negative impact of the phase-locked loop in the control loop, thereby improving the oscillation suppression capability of the system.

[0084] S160, controlling the switch tube according to the first modulation signal and the second modulation signal.

[0085] The pulse width modulation gain of the switch tube is obtained according to the first modulation signal and the second modulation signal, and the switch tube is controlled based on the pulse width modulation gain. Without changing the control loop structure of the inverter or adding an additional auxiliary control loop, the d-axis and the q-axis adopt asymmetric control parameters to improve the system's oscillation suppression capability, avoiding the inverter's control structure from being too complicated. In addition, the q-axis adopts an asymmetric design that introduces a suppression feedback signal to offset the negative impact of the phase-locked loop on the inverter's broadband oscillation, further improving the system's oscillation suppression capability on the basis of simplifying the inverter's control structure.

[0086] In an embodiment of the present application, the control method of the inverter further includes:

[0087] Obtaining a first current steady-state value and a second current steady-state value, wherein the first current steady-state value is the current steady-state value of the output current of the switch tube on the q-axis, and the second current steady-state value is the current steady-state value of the output current of the switch tube on the d-axis;

[0088] Acquiring a first modulation signal output by a d-axis current regulator based on a first projection component, a first current reference value, and a first control parameter, comprising:

[0089] Converting the voltage component according to the first current steady-state value and the disturbance transfer function of the phase-locked loop to obtain a first feedforward signal;

[0090] Adding a first component difference to a first feedforward signal to obtain a first control signal, wherein the first component difference is a difference between the first projection component and a first current reference value;

[0091] Acquire a first modulation signal output by the d-axis current regulator based on the first control signal and the first control parameter;

[0092] Acquiring a second modulation signal output by the q-axis current regulator based on the second projection component, the second current reference value component, the suppression feedback signal and the second control parameter, comprising:

[0093] Converting the voltage component according to the second current steady-state value and the disturbance transfer function of the phase-locked loop to obtain a second feedforward signal;

[0094] Adding the second component difference, the second feedforward signal and the suppression feedback signal to obtain a second control signal, wherein the second component difference is the difference between the second projection component and the second current reference value;

[0095] A first modulation signal output by the q-axis current regulator based on the second control signal and the second control parameter is obtained.

[0096] See also Figure 4 , Figure 4 A schematic diagram of the structure of the d-axis current control inner loop provided in an embodiment of the present application is shown.

[0097] See also Figure 5 , Figure 5 A schematic diagram of the structure of the q-axis current control inner loop provided in an embodiment of the present application is shown.

[0098] When the inverter is in steady-state operation, the output phase angle of the phase-locked loop is synchronized with the grid. When a small disturbance occurs in the grid voltage, due to the dynamic regulation characteristics of the phase-locked loop, the output angular frequency of the phase-locked loop is no longer equal to the grid angular frequency, resulting in a phase angle deviation between the dq coordinate system of the inverter and the dq coordinate system of the grid, and an equivalent control structure of the d-axis current control inner loop and the q-axis current control inner loop can be obtained. The first current steady-state value and the second current steady-state value are obtained, wherein the first current steady-state value is the current steady-state value of the output current of the switch tube on the q-axis, and the second current steady-state value is the current steady-state value of the output current of the switch tube on the d-axis.

[0099] In the figure, is the component of the grid-connected current reference value on the d-axis in the dq coordinate system of the inverter, is the d-axis current projection component in the grid dq coordinate system, I q0 is the first current steady-state value, The voltage component of the access point voltage on the q-axis in the dq coordinate system of the power grid is converted according to the first current steady-state value and the disturbance transfer function of the phase-locked loop, that is, the voltage component is substituted into the disturbance transfer function of the phase-locked loop as a state component, and multiplied with the first current steady-state value to obtain a first feedforward signal. The first projection component is subtracted from the first current reference value to obtain a first component difference. The first component difference is added to the first feedforward signal to obtain a first control signal. The first control signal is substituted into the first control parameter as a state component to obtain a first modulation signal output by the d-axis current regulator based on the first control signal and the first control parameter.

[0100] In the figure, is the component of the grid-connected current reference value on the q axis in the dq coordinate system of the inverter, The q-axis current projection component in the dq coordinate system of the power grid is converted according to the second current steady-state value and the disturbance transfer function of the phase-locked loop, that is, the voltage component is substituted as a state component into the disturbance transfer function of the phase-locked loop, and multiplied with the second current steady-state value to obtain a second feedforward signal. The second projection component is subtracted from the second current reference value to obtain the second component difference. The second component difference, the second feedforward signal and the suppression feedback signal are added to obtain the second control signal. The second control signal is substituted as a state component into the second control parameter to obtain the first modulation signal output by the q-axis current regulator based on the second control signal and the second control parameter. By introducing the first feedforward signal and the second feedforward signal, the phase angle deviation between the dq coordinate system of the inverter and the dq coordinate system of the power grid is eliminated, and the negative impact of the phase-locked loop on the broadband oscillation of the inverter is further offset.

[0101] In an embodiment of the present application, controlling the switch tube according to the first modulation signal and the second modulation signal includes:

[0102] Acquire a first signal steady-state value corresponding to the first modulation signal and a second signal steady-state value corresponding to the second modulation signal;

[0103] Converting the voltage component according to the first signal stability value and the disturbance transfer function of the phase-locked loop to obtain a third feedforward signal;

[0104] Adding the third feedforward signal to the first modulation signal to obtain an updated first modulation signal;

[0105] Converting the voltage component according to the second signal stability value and the disturbance transfer function of the phase-locked loop to obtain a fourth feedforward signal;

[0106] Adding the fourth feedforward signal to the second modulation signal to obtain an updated second modulation signal;

[0107] Based on the updated first modulation signal and the updated second modulation signal, a pulse width modulation gain of the switch tube is obtained, and the switch tube is controlled based on the pulse width modulation gain.

[0108] Obtain a first signal steady-state value corresponding to the first modulation signal, and a second signal steady-state value corresponding to the second modulation signal. According to the first signal steady-state value and the disturbance transfer function of the phase-locked loop, convert the voltage component, that is, substitute the voltage component as a state component into the disturbance transfer function of the phase-locked loop, and multiply it with the first signal steady-state value to obtain a third feedforward signal. Add the third feedforward signal to the first modulation signal to obtain an updated first modulation signal;

[0109] According to the stable value of the second signal and the disturbance transfer function of the phase-locked loop, the voltage component is converted, that is, the voltage component is substituted into the disturbance transfer function of the phase-locked loop as a state component, and multiplied with the steady-state value of the second signal to obtain a fourth feedforward signal. The fourth feedforward signal is added to the second modulation signal to update the second modulation signal. Based on the updated first modulation signal and the updated second modulation signal, the pulse width modulation gain of the switch tube is obtained, and the switch tube is controlled based on the pulse width modulation gain. By introducing the third feedforward signal and the fourth feedforward signal, the phase angle deviation between the dq coordinate system of the inverter and the dq coordinate system of the power grid is eliminated, and the negative impact of the phase-locked loop on the broadband oscillation of the inverter is further offset.

[0110] In an embodiment of the present application, the control method of the inverter further includes:

[0111] Construct the impedance matrix model of the inverter;

[0112] Based on the impedance matrix model, the inverter's return rate matrix is ​​constructed;

[0113] According to the eigenvalue curve corresponding to the return rate matrix, the oscillation characteristic determination result of the inverter is generated.

[0114] See also Figure 6 , Figure 6 The transfer function model of the inverter provided in the embodiment of the present application is shown.

[0115] The transfer function model of the inverter includes multiple sub-transfer function models, and the sub-transfer function models in the figure are:

[0116]

[0117]

[0118] Among them, k pd is the proportionality factor of the d-axis current regulator, k id is the integral coefficient of the d-axis current regulator, k pq is the proportional coefficient of the q-axis current regulator, kiq is the integral coefficient of the q-axis current regulator, G PLL (s) is the disturbance transfer function of the phase-locked loop, H PI (s) is the control parameter of the PI controller of the phase-locked loop, s is the state variable, V m0 is the steady-state value of the grid voltage, i 2q0 is the steady-state value of the current component of the grid-connected current on the q axis, i 2d0 is the steady-state value of the current component of the grid-connected current on the d-axis, K is the feedback gain; G g,c is the preset conversion factor, T s is the sampling period, V Md0 is the steady-state value of the first signal corresponding to the first modulation signal, V Mq0 is the steady-state value of the second signal corresponding to the second modulation signal, L1 is the first filter inductor, L2 is the second filter inductor, C f is the filter capacitor, ω1 is the rated angular frequency of the power grid, R d is a passive damping resistor.

[0119] According to the sub-transfer function models in the figure, the impedance matrix model of the inverter can be constructed as follows:

[0120]

[0121] Among them, Y invdq is the impedance matrix model, I m is a 2*2 current matrix, is the pulse width modulation gain of the switch tube, G v (s) is the control parameter of the current inner loop PI controller.

[0122] See also Figure 7 , Figure 7 An example graph of a characteristic value curve of a grid impedance of 32 mH provided in an embodiment of the present application is shown.

[0123] Photovoltaic is connected to the grid through an inverter, and the oscillation characteristic determination result of the inverter is generated according to the eigenvalue curve corresponding to the rate matrix. In this embodiment, the oscillation analysis results are obtained when the grid impedance is 32mH and 35mH. When the grid impedance is 32mH, the eigenvalue curve corresponding to the rate matrix does not surround the (1, j0) point, and the photovoltaic can operate stably at this time.

[0124] See also Figure 8 , Figure 8 An example diagram of a characteristic value curve of a grid impedance of 35 mH provided in an embodiment of the present application is shown.

[0125] When the grid impedance increases to 35mH, the eigenvalue curve corresponding to the rate matrix surrounds the point (1, j0), at which point the photovoltaic loses stability and oscillates.

[0126] See also Fig. 9 , Fig. 9 An example diagram of a grid-connected current waveform with a grid impedance of 32 mH provided in an embodiment of the present application is shown.

[0127] See also Fig.10 , Fig.10 An example diagram of a grid-connected current waveform with a grid impedance of 35 mH provided in an embodiment of the present application is shown.

[0128] The figure shows the grid-connected current waveform when the grid impedance is 32mH and 35mH respectively. The inverter control method provided in this embodiment improves the stability of the photovoltaic grid-connected inverter and the correctness and effectiveness of oscillation suppression, significantly improves the adaptability of the photovoltaic grid-connected inverter to the grid impedance, and promotes the on-site consumption of photovoltaics.

[0129] The present application provides a control method for an inverter, including: determining the first projection component of the grid-connected current on the d-axis and the second projection component on the q-axis according to the output phase angle of the phase-locked loop; obtaining the first current reference value component and the second current reference value component; obtaining the first modulation signal output by the d-axis current regulator based on the first projection component, the first current reference value and the first control parameter; obtaining the suppression feedback signal according to the voltage component of the access point voltage on the q-axis and the disturbance transfer function of the phase-locked loop; obtaining the second modulation signal output by the q-axis current regulator based on the second projection component, the second current reference value component, the suppression feedback signal and the second control parameter; and controlling the switch tube according to the first modulation signal and the second modulation signal. Without changing the control loop structure of the inverter or adding an additional auxiliary control loop, the d-axis and the q-axis use asymmetric control parameters to improve the oscillation suppression capability of the system, avoiding the control structure of the inverter from being too complicated. In addition, the q-axis adopts an asymmetric design that introduces a suppression feedback signal to offset the negative impact of the phase-locked loop on the broadband oscillation of the inverter, and further improves the oscillation suppression capability of the system on the basis of simplifying the control structure of the inverter.

[0130] Example 2

[0131] See also Fig.11 , Fig.11 The schematic diagram of the structure of the control device of the inverter provided by the embodiment of the present application is shown. The inverter includes a switch tube, a phase-locked loop, a d-axis current regulator and a q-axis current regulator. The switch tube is connected to the input end of the d-axis current regulator and the input end of the q-axis current regulator respectively through the phase-locked loop. The output end of the d-axis current regulator and the output end of the q-axis current regulator are both connected to the switch tube. The inverter is connected to the power grid through an access point. Fig.11 The control device 200 of the inverter includes:

[0132] A projection component determination module 210, configured to determine a first projection component of the grid-connected current on the d-axis and a second projection component on the q-axis according to an output phase angle of the phase-locked loop;

[0133] A reference value component determination module 220, configured to obtain a first current reference value component and a second current reference value component, wherein the first current reference value is a component of the grid-connected current reference value on the d-axis, and the second current reference value component is a component of the grid-connected current reference value on the q-axis;

[0134] A first modulation signal obtaining module 230 is used to obtain a first modulation signal output by the d-axis current regulator based on the first projection component, the first current reference value and the first control parameter, wherein the first control parameter is a control parameter of the d-axis current regulator;

[0135] The suppression feedback signal obtaining module 240 is used to obtain the suppression feedback signal according to the voltage component of the access point voltage on the q-axis and the disturbance transfer function of the phase-locked loop;

[0136] A second modulation signal obtaining module 250 is used to obtain a second modulation signal output by the q-axis current regulator based on the second projection component, the second current reference value component, the suppression feedback signal and the second control parameter, wherein the second control parameter is a control parameter of the q-axis current regulator, and the first control parameter and the second control parameter are asymmetric control parameters;

[0137] The switch control module 260 is used to control the switch according to the first modulation signal and the second modulation signal.

[0138] In an embodiment of the present application, the feedback suppression signal obtaining module 240 is also used to convert the voltage component of the access point voltage on the q-axis according to the disturbance transfer function of the phase-locked loop, the current steady-state value of the grid-connected current on the d-axis, the preset conversion coefficient and the feedback gain of the phase-locked loop, so as to obtain a feedback suppression signal of the q-axis current regulator, wherein the preset conversion coefficient is the conversion coefficient between the grid voltage and the phase-locked loop voltage.

[0139] In the embodiment of the present application, the control device 200 of the inverter further includes:

[0140] A current steady-state value acquisition module, used to acquire a first current steady-state value and a second current steady-state value, wherein the first current steady-state value is the current steady-state value of the output current of the switch tube on the q-axis, and the second current steady-state value is the current steady-state value of the output current of the switch tube on the d-axis;

[0141] The first modulated signal obtaining module 230 includes:

[0142] A first feedforward signal obtaining submodule, used for converting a voltage component according to a first current steady-state value and a disturbance transfer function of a phase-locked loop to obtain a first feedforward signal;

[0143] A first control signal obtaining submodule, used for adding a first component difference to a first feedforward signal to obtain a first control signal, wherein the first component difference is a difference between a first projection component and a first current reference value;

[0144] A first modulation signal output submodule, used for obtaining a first modulation signal output by the d-axis current regulator based on the first control signal and the first control parameter;

[0145] The second modulated signal obtaining module 250 includes:

[0146] A second feedforward signal obtaining submodule, used for converting the voltage component according to the second current steady-state value and the disturbance transfer function of the phase-locked loop to obtain a second feedforward signal;

[0147] A second control signal obtaining submodule is used to add a second component difference, a second feedforward signal and a suppression feedback signal to obtain a second control signal, wherein the second component difference is a difference between a second projection component and a second current reference value;

[0148] The second modulation signal output submodule is used to obtain a first modulation signal output by the q-axis current regulator based on the second control signal and the second control parameter.

[0149] In the embodiment of the present application, the switch control module 260 includes:

[0150] A signal steady-state value acquisition submodule, used to acquire a first signal steady-state value corresponding to the first modulated signal, and a second signal steady-state value corresponding to the second modulated signal;

[0151] A third feedforward signal obtaining submodule is used to convert the voltage component according to the first signal stability value and the disturbance transfer function of the phase-locked loop to obtain a third feedforward signal;

[0152] A first modulation signal updating submodule, configured to add the third feedforward signal to the first modulation signal to obtain an updated first modulation signal;

[0153] A fourth feedforward signal obtaining submodule is used to convert the voltage component according to the second signal stability value and the disturbance transfer function of the phase-locked loop to obtain a fourth feedforward signal;

[0154] A second modulation signal updating submodule, used for adding the fourth feedforward signal to the second modulation signal to obtain an updated second modulation signal;

[0155] The pulse width modulation gain obtaining submodule is used to obtain the pulse width modulation gain of the switch tube based on the updated first modulation signal and the updated second modulation signal, and control the switch tube based on the pulse width modulation gain.

[0156] In an embodiment of the present application, the reference value component determination module 220 includes:

[0157] An equation building submodule, used to build an equation relationship between the DC side and the AC side of the inverter;

[0158] A first small signal model building submodule, used to build a first small signal model between a voltage outer loop and a current inner loop reference value of the inverter;

[0159] A second small signal model construction submodule is used to obtain a second small signal model of the current inner loop according to the equation relationship and the first small signal model;

[0160] The component determination submodule is used to obtain a first current reference value component and a second current reference value component based on a second small signal model.

[0161] In the embodiment of the present application, the equation construction submodule is also used to construct a second small signal model of the DC side of the inverter;

[0162] Construct the third smallest signal model of the output power of the switch tube;

[0163] Based on the second small signal model and the third small signal model, an equation relationship between the DC side and the AC side of the inverter is constructed.

[0164] In the embodiment of the present application, the control device 200 of the inverter further includes:

[0165] A matrix model building module, used to build an impedance matrix model of the inverter;

[0166] A rate matrix building module is used to build a rate matrix of the inverter based on an impedance matrix model;

[0167] The oscillation characteristic determination module is used to generate an oscillation characteristic determination result of the inverter according to the eigenvalue curve corresponding to the return rate matrix.

[0168] The present application also provides a computing device, including:

[0169] a memory configured to store instructions;

[0170] The processor is configured to call instructions from the memory and implement the above-mentioned inverter control method when executing the instructions.

[0171] The processor contains a kernel, which calls the corresponding program unit from the memory. One or more kernels can be set, and different behavior scenarios cannot be accurately identified by adjusting kernel parameters.

[0172] The memory may include non-permanent memory in a computer-readable medium, random access memory (RAM) and / or non-volatile memory, such as read-only memory (ROM) or flash RAM, and the memory includes at least one memory chip.

[0173] An embodiment of the present application also provides a machine-readable storage medium, on which instructions are stored, and the instructions are used to enable a machine to execute the above-mentioned inverter control method.

[0174] Those skilled in the art will appreciate that the embodiments of the present application may be provided as methods, systems, or computer program products. Therefore, the present application may adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment in combination with software and hardware. Moreover, the present application may adopt the form of a computer program product implemented in one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) that include computer-usable program code.

[0175] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0176] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0177] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0178] In a typical configuration, a computing device includes one or more processors (CPU), input / output interfaces, network interfaces, and memory.

[0179] The memory may include non-permanent memory in a computer-readable medium, random access memory (RAM) and / or non-volatile memory in the form of read-only memory (ROM) or flash RAM. The memory is an example of a computer-readable medium.

[0180] Machine-readable storage media include permanent and non-permanent, removable and non-removable media that can be implemented by any method or technology to store information. Information can be computer-readable instructions, data structures, program modules or other data. Examples of computer storage media include, but are not limited to, phase change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technology, compact disk read-only memory (CD-ROM), digital versatile disk (DVD) or other optical storage, magnetic cassettes, magnetic tape magnetic disk storage or other magnetic storage devices or any other non-transmission media that can be used to store information that can be accessed by a computing device. As defined herein, computer-readable media does not include temporary computer-readable media (transitory media), such as modulated data signals and carrier waves.

[0181] It should also be noted that the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, commodity or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, commodity or device. In the absence of more restrictions, the elements defined by the sentence "comprises a ..." do not exclude the existence of other identical elements in the process, method, commodity or device including the elements.

[0182] The above are only embodiments of the present application and are not intended to limit the present application. For those skilled in the art, the present application may have various changes and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included within the scope of the claims of the present application.

Claims

1. A control method for an inverter, characterized in that: The inverter includes a switch tube, a phase-locked loop, a d-axis current regulator, and a q-axis current regulator. The switch tube is connected to an input end of the d-axis current regulator and an input end of the q-axis current regulator respectively through the phase-locked loop. The output end of the d-axis current regulator and the output end of the q-axis current regulator are both connected to the switch tube. The inverter is connected to a power grid through an access point. The control method of the inverter includes: Determining a first projection component of the grid-connected current on the d-axis and a second projection component on the q-axis according to an output phase angle of the phase-locked loop; Obtaining a first current reference value component and a second current reference value component, wherein the first current reference value is a component of the grid-connected current reference value on the d-axis, and the second current reference value component is a component of the grid-connected current reference value on the q-axis; Acquire a first modulation signal output by the d-axis current regulator based on the first projection component, the first current reference value and a first control parameter, wherein the first control parameter is a control parameter of the d-axis current regulator; Obtaining a suppression feedback signal according to a voltage component of the access point voltage on the q-axis and a disturbance transfer function of the phase-locked loop; Acquire a second modulation signal output by the q-axis current regulator based on the second projection component, the second current reference value component, the suppression feedback signal and a second control parameter, wherein the second control parameter is a control parameter of the q-axis current regulator, and the first control parameter and the second control parameter are asymmetric control parameters; The switch tube is controlled according to the first modulation signal and the second modulation signal.

2. The inverter control method according to claim 1, characterized in that: The step of obtaining a suppression feedback signal according to a voltage component of the access point voltage on the q-axis and a disturbance transfer function of the phase-locked loop comprises: According to the disturbance transfer function of the phase-locked loop, the current steady-state value of the grid-connected current on the d-axis, the preset conversion coefficient and the feedback gain of the phase-locked loop, the voltage component of the access point voltage on the q-axis is converted to obtain the suppressed feedback signal of the q-axis current regulator, wherein the preset conversion coefficient is the conversion coefficient between the grid voltage and the phase-locked loop voltage.

3. The inverter control method according to claim 1, characterized in that: The control method of the inverter further includes: Acquire a first current steady-state value and a second current steady-state value, wherein the first current steady-state value is a current steady-state value of the output current of the switch tube on the q-axis, and the second current steady-state value is a current steady-state value of the output current of the switch tube on the d-axis; The obtaining of a first modulation signal output by the d-axis current regulator based on the first projection component, the first current reference value and the first control parameter comprises: Converting the voltage component according to the first current steady-state value and the disturbance transfer function of the phase-locked loop to obtain a first feedforward signal; Adding a first component difference to the first feedforward signal to obtain the first control signal, wherein the first component difference is a difference between the first projection component and the first current reference value; Acquire a first modulation signal output by the d-axis current regulator based on the first control signal and the first control parameter; The step of obtaining a second modulation signal output by the q-axis current regulator based on the second projection component, the second current reference value component, the suppression feedback signal and the second control parameter comprises: converting the voltage component according to the second current steady-state value and the disturbance transfer function of the phase-locked loop to obtain a second feedforward signal; Adding a second component difference, the second feedforward signal and the suppression feedback signal to obtain the second control signal, wherein the second component difference is a difference between the second projection component and the second current reference value; A first modulation signal output by the q-axis current regulator based on the second control signal and the second control parameter is obtained.

4. The control method of the inverter according to claim 1, characterized in that: The step of controlling the switch tube according to the first modulation signal and the second modulation signal includes: Acquire a first signal steady-state value corresponding to the first modulation signal, and a second signal steady-state value corresponding to the second modulation signal; converting the voltage component according to the first signal stability value and the disturbance transfer function of the phase-locked loop to obtain a third feedforward signal; Adding the third feedforward signal to the first modulation signal to obtain an updated first modulation signal; converting the voltage component according to the second signal stability value and the disturbance transfer function of the phase-locked loop to obtain a fourth feedforward signal; Adding the fourth feedforward signal to the second modulation signal to obtain an updated second modulation signal; Based on the updated first modulation signal and the updated second modulation signal, a pulse width modulation gain of the switch tube is obtained, and the switch tube is controlled based on the pulse width modulation gain.

5. The control method of the inverter according to claim 1, characterized in that: The obtaining of the first current reference value component and the second current reference value component comprises: Constructing an equation relationship between the DC side and the AC side of the inverter; Constructing a first small signal model between a voltage outer loop and a current inner loop reference value of the inverter; According to the equation relationship and the first small signal model, a second small signal model of the current inner loop is obtained; Based on the second small signal model, the first current reference value component and the second current reference value component are obtained.

6. The control method of the inverter according to claim 5, characterized in that: The constructing of an equation relationship between the DC side and the AC side of the inverter includes: Constructing a second small signal model of the DC side of the inverter; Constructing a third small signal model of the output power of the switch tube; Based on the second small signal model and the third small signal model, an equation relationship between the DC side and the AC side of the inverter is constructed.

7. The inverter control method according to claim 1, characterized in that: The control method of the inverter further includes: Constructing an impedance matrix model of the inverter; Based on the impedance matrix model, constructing a rate matrix of the inverter; The oscillation characteristic determination result of the inverter is generated according to the eigenvalue curve corresponding to the rate matrix.

8. A control device for an inverter, characterized in that: The inverter includes a switch tube, a phase-locked loop, a d-axis current regulator and a q-axis current regulator. The switch tube is connected to the input end of the d-axis current regulator and the input end of the q-axis current regulator respectively through the phase-locked loop. The output end of the axis current regulator and the output end of the q-axis current regulator are both connected to the switch tube. The inverter is connected to the power grid through an access point. The control device of the inverter includes: A projection component determination module, used to determine a first projection component of the grid-connected current on the d-axis and a second projection component on the q-axis according to an output phase angle of the phase-locked loop; A reference value component determination module, used to obtain a first current reference value component and a second current reference value component, wherein the first current reference value is a component of the grid-connected current reference value on the d-axis, and the second current reference value component is a component of the grid-connected current reference value on the q-axis; a first modulation signal obtaining module, configured to obtain a first modulation signal output by the d-axis current regulator based on the first projection component, the first current reference value and a first control parameter, wherein the first control parameter is a control parameter of the d-axis current regulator; A suppression feedback signal obtaining module, used for obtaining a suppression feedback signal according to a voltage component of the access point voltage on the q-axis and a disturbance transfer function of the phase-locked loop; A second modulation signal obtaining module, used for obtaining a second modulation signal output by the q-axis current regulator based on the second projection component, the second current reference value component, the suppression feedback signal and a second control parameter, wherein the second control parameter is a control parameter of the q-axis current regulator, and the first control parameter and the second control parameter are asymmetric control parameters; A switch tube control module is used to control the switch tube according to the first modulation signal and the second modulation signal.

9. A computing device, characterized in that include: a memory configured to store instructions; A processor is configured to call the instruction from the memory and implement the inverter control method according to any one of claims 1 to 7 when executing the instruction.

10. A machine-readable storage medium, characterized in that: The machine-readable storage medium stores instructions, and the instructions are used to enable a machine to execute the inverter control method according to any one of claims 1 to 7.

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