Quantitative characterization method for AHO-VOC output characteristics

Abstract

A quantitative characterization method for AHO-VOC output characteristics. The method comprises: step S1, establishing dynamic equations of an AHO-VOC output voltage and a phase angle in a three-phase grid-connected mode, and accordingly determining an AHO-VOC reactive power-voltage nonlinear relationship and an active power-frequency linear relationship when a grid-connected system is in steady-state operation; step S2, decoupling the dynamic equation of the AHO-VOC output voltage, so as to derive an explicit expression of the AHO-VOC output voltage; step S3, analyzing the impact of changes in intrinsic and extrinsic parameters of an AHO-VOC controller on AHO-VOC grid-connected output characteristics, and determining a dominant parameter affecting a change in the output voltage; step S4, designing key parameters of the grid-connected system in consideration of AHO-VOC three-phase grid-connected adaptability; and step S5, on the basis of the key parameters, drawing a relationship curve between the dominant parameter and the output voltage, and determining relational expressions between the dominant parameter and the output voltage in different sections.

Description

A quantitative characterization method for AHO-VOC output characteristics Technical Field

[0001] The present invention relates to the technical field, and in particular to a method for quantitatively characterizing AHO-VOC output characteristics. Background Art

[0002] With the large-scale installation of power electronic equipment, the transient stability of grid-connected inverters under large grid disturbances is crucial for the safe and stable operation of the grid. As an emerging method for achieving grid-connected inverter control, Andronov-Hopf Virtual Oscillator Control (AHO-VOC) has the advantage of being able to quickly respond to system requirements without the need for complex power calculations and dual-loop control. Existing research on AHO-VOC mainly focuses on small-signal stability. However, transient stability analysis of AHO-VOC under conditions such as voltage sag, phase angle jump, and frequency mutation is relatively lacking and has low accuracy. A major reason for this is that there is currently no good way to quantitatively characterize the output characteristics of AHO-VOC. In other words, it is impossible to explore the output characteristics of AHO-VOC under different grid voltage sag levels from a numerical analysis perspective, which has hindered the subsequent analysis of AHO-VOC transient stability.

[0003] Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide an effective method for quantitatively characterizing AHO-VOC output characteristics.

[0005] In order to solve the above technical problems, the present invention adopts the following technical methods: a quantitative characterization method of AHO-VOC output characteristics, comprising:

[0006] Step S1, establishing a dynamic equation for the AHO-VOC output voltage and phase angle in a three-phase grid-connected mode, and determining the nonlinear relationship between the AHO-VOC reactive power and voltage and the linear relationship between the active power and frequency when the grid-connected system enters steady-state operation based on the dynamic equation;

[0007] Step S2, decoupling the dynamic equation of the AHO-VOC output voltage and deriving an explicit expression of the AHO-VOC output voltage V;

[0008] Step S3, analyzing the impact of changes in various internal and external parameters of the AHO-VOC controller on the AHO-VOC grid-connected output characteristics, and determining the dominant parameters that affect the change in the output voltage V;

[0009] Step S4, designing the key parameters of the grid-connected system considering the adaptability of the AHO-VOC three-phase grid-connected system;

[0010] Step S5, based on the key parameters designed in step S4, draw a relationship curve between the dominant parameters and the output voltage V, and determine the relationship expression between the dominant parameters and the output voltage V in different sections.

[0011] Furthermore, the step S1 includes:

[0012] S101, based on the first-order nonlinear oscillator, construct an AHO-VOC oscillator model and determine the differential equation of the AHO-VOC oscillator model, which is:

[0013] Where ξ is the convergence coefficient of the oscillator; X nom is the amplitude of the output oscillation waveform; ω nom is the rated angular frequency of the oscillator; are the time-varying derivatives of x1 and x2 respectively; ||x|| is the Euclidean norm related to x1 and x2; x1 and x2 are both state variables, representing the oscillating capacitor voltage v C And the corrected oscillating inductor current εi L , ε is expressed as:

[0014] Where, L is the oscillation inductance; C is the oscillation capacitance;

[0015] S102: Build a three-phase grid-connected system based on the AHO-VOC oscillator model built in S101 and determine the reference value of the inverter α-axis output current. and β-axis output current reference value Controllable current source command signal u1 and controllable voltage source command signal u2, as well as inverter α axis output voltage v α and β-axis output voltage v β , respectively as follows:

[0016] Where, P * is the active output reference value; Q * is the reactive output reference value; i α is the inverter α-axis output current; i β is the inverter β-axis output current; k i is the current correction factor; k v is the voltage correction factor;

[0017] S103, based on equations (1)-(5), first determine the dynamic equation (6) of the AHO-VOC output voltage and the dynamic equation (7) of the phase angle in the three-phase grid-connected mode;

[0018] Where, is the time derivative of the inverter α-axis output voltage; The time derivative of the inverter axis β output voltage; V nom is the rated value of the inverter output voltage; P is the active power; Q is the reactive power; V nom =k v X nom ;

[0019] According to the dynamic equation (6) of the AHO-VOC output voltage, it is determined that the reactive power-voltage relationship of the AHO-VOC is nonlinear when the grid-connected system enters steady-state operation, and its expression is:

[0020] According to the dynamic equation (7) of the AHO-VOC phase angle, it is determined that when the grid-connected system enters steady-state operation, the active power of AHO-VOC and the frequency are in a linear relationship, and the expression is:

[0021] Furthermore, the step S2 includes:

[0022] S201, substitute the inverter output power based on the power angle relationship into the dynamic equation (6) of the AHO-VOC output voltage, and set the reactive reference value Q ref =0, we get:

[0023] S202, k v =V nom , k i =3V nom / S rated Substituting into equation (10) and solving, we obtain the explicit expression of the AHO-VOC output voltage V as follows:

[0024] Where V g represents the grid voltage; δ is the phase difference between the inverter output voltage and the grid connection point voltage; X T is the grid impedance; S rated is the rated apparent power of the inverter.

[0025] Furthermore, in step S3, the external parameter is V g 、k v , the internal parameters are C, X T ,ξ;

[0026] 1) Considering the adaptability of AHO-VOC three-phase grid connection, k v When the value is within the range of 120-240, Vg is the dominant parameter affecting the output voltage V;

[0027] 2) C, X T The change of V has little effect on the AHO-VOC grid-connected output characteristics, but affects V g k as the dominant parameter of the output voltage V v Value range;

[0028] 3) Considering the adaptability of AHO-VOC three-phase grid connection, when the value of ξ is less than 10, V g It is the dominant parameter affecting the output voltage V.

[0029] Furthermore, in step S4, the process of designing the key parameters of the grid-connected system considering the adaptability of the AHO-VOC three-phase grid-connected system is as follows:

[0030] First, normalize the following parameters:

[0031] Substituting formula (12) into formula (6) and (7) yields:

[0032] Next, consider the operating conditions of the AHO-VOC system with a maximum frequency deviation of Δf = 0.2 and a maximum amplitude deviation of ΔV = 5%, as shown in the following equation:

[0033] Arranging equations (13)-(15) and simplifying them, we obtain:

[0034] Finally, according to formulas (12), (16), and (17), the values ​​of the key parameters of the grid-connected system are calculated as follows:

[0035] Oscillation capacitance C = 0.7829F, convergence coefficient ξ = 1.299;

[0036] In formulas (12), (16), and (17), V nom is the rated value of the inverter output voltage RMS, which is 230V; V min is the minimum output voltage of the inverter, V min The per-unit value of Take 0.95pu; P rated is the rated active power of the inverter, which is 5500W; S rated is the rated apparent power of the inverter, which is 5590VA; nom is the rated angular frequency of the oscillator, and its value is 314.16Hz; ω minThe minimum angular frequency of the oscillator is 312.744 Hz.

[0037] Preferably, in step S5, based on the key parameters designed in step S4, V g As the dominant parameter affecting the output voltage V, plot V g The relationship curve between the dominant parameters and the output voltage V is determined to be:

[0038] Where V g The unit of V is volts.

[0039] This paper provides a method for quantitatively characterizing the output characteristics of an AHO-VOC. This method, based on the mechanism of the AHO-VOC oscillator model, specifically analyzes the adaptability of the AHO-VOC in a three-phase grid-connected mode. Based on the dynamic equations of the AHO-VOC in this three-phase grid-connected state, it analyzes the impact of changes in internal and external parameters on the output characteristics, resulting in a quantitative characterization of the output voltage in this state. This simple and effective method fills a gap in the quantitative characterization of AHO-VOC output characteristics and significantly aids in the analysis of AHO-VOC transient stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] FIG1 is a flow chart of a method for quantitatively characterizing AHO-VOC output characteristics according to the present invention;

[0041] FIG2 is a schematic diagram of a limit cycle curve of a first-order nonlinear oscillator in the present invention;

[0042] FIG3 is a topological diagram of the AHO-VOC oscillator model in the present invention;

[0043] FIG4 is a schematic diagram of a limit cycle curve of the AHO-VOC oscillator model of the present invention;

[0044] FIG5 is a topology diagram of a three-phase grid-connected system constructed based on the AHO-VOC oscillator model in the present invention;

[0045] FIG6 is a graph showing the AHO-VOC grid-connected output characteristic relationship in the present invention;

[0046] FIG7 is a graph showing the AHO-VOC grid-connected output characteristic relationship under changes in oscillation capacitance in the present invention;

[0047] FIG8 is a graph showing the relationship between the AHO-VOC grid-connected output characteristics under varying grid strength in the present invention;

[0048] FIG9 is a graph showing the AHO-VOC grid-connected output characteristic relationship curves at different convergence speeds in the present invention (wherein (a) is a graph showing the AHO-VOC grid-connected output characteristic relationship curve when ξ is 0.2; (b) is a graph showing the AHO-VOC grid-connected output characteristic relationship curve when ξ is 2; (c) is a graph showing the AHO-VOC grid-connected output characteristic relationship curve when ξ is 20; and (d) is a graph showing the AHO-VOC grid-connected output characteristic relationship curve when ξ is 50);

[0049] FIG10 is a graph showing the output voltage V and the grid voltage V in the present invention. g The relationship curve diagram;

[0050] FIG11 is a graph showing the output voltage V and the grid voltage V in the present invention. g Piecewise linearization curve of . DETAILED DESCRIPTION

[0051] In order to facilitate understanding by those skilled in the art, the present invention will be further described below with reference to embodiments and drawings. The contents mentioned in the embodiments are not intended to limit the present invention.

[0052] As shown in Figure 1, a quantitative characterization method for AHO-VOC output characteristics includes five steps, as follows.

[0053] Step S1: Analysis of three-phase grid-connected system based on AHO-VOC oscillator model

[0054] S101: constructing an AHO-VOC oscillator model based on a first-order nonlinear oscillator and determining a differential equation of the AHO-VOC oscillator model.

[0055] Before introducing the AHO-VOC oscillator model, the present invention first discusses the dynamic characteristics of the oscillator model based on a first-order nonlinear oscillator, whose differential equation is shown in Equation (19):

[0056] Where x1 and x2 are state variables; are the derivatives of x1 and x2 over time; ω nom is the rated angular frequency of the oscillator.

[0057] The limit cycle curve of the first-order nonlinear oscillator can be drawn from Equation (19) as shown in Figure 2. In Figure 2, A is the initial operating point of the system. As shown in Figure 2, the above-mentioned first-order nonlinear oscillator has the following problems:

[0058] 1) A stable closed limit cycle cannot be formed, and the output amplitude is difficult to control.

[0059] 2) The dynamic trajectory of state variables x1 and x2 is an oscillating amplified sinusoidal waveform that cannot converge and stabilize, making it difficult to apply to the control of grid-connected inverters.

[0060] In order to solve the above problems, the present invention expands the first-order nonlinear oscillator of formula (19) and constructs the AHO-VOC oscillator model as shown in Figure 3. In Figure 3, L and C are the oscillation inductance and oscillation capacitance, respectively, which are used to control the oscillation frequency of the oscillator; i m and V m are controllable current source and controllable voltage source, respectively, used to control the amplitude of the oscillator output waveform, which are specifically expressed as follows:

[0061] Where, X nom is the amplitude of the output oscillation waveform; ξ is the convergence coefficient of the oscillator.

[0062] From this, the differential equation of the AHO-VOC oscillator model can be obtained, as shown in formula (1):

[0063] Where ξ is the convergence coefficient of the oscillator; X nom is the amplitude of the output oscillation waveform; ω nom is the rated angular frequency of the oscillator; are the time-varying derivatives of x1 and x2 respectively; ||x|| is the Euclidean norm related to x1 and x2; x1 and x2 are both state variables, representing the oscillating capacitor voltage v C And the corrected oscillating inductor current εi L , ε is expressed as:

[0064] Where L is the oscillation inductance; C is the oscillation capacitance.

[0065] Based on Equation (1), the limit cycle curve of the AHO-VOC oscillator model can be plotted as shown in Figure 4, where A and B are two different initial operating points. As shown in Figure 4, the AHO-VOC oscillator model can control the output of the state variables x1 and x2 under arbitrary initial conditions to be a stable sinusoidal signal with controllable amplitude and frequency, showing potential for application in grid-connected systems.

[0066] S102, constructing a three-phase grid-connected system based on the AHO-VOC oscillator model.

[0067] As shown in Figure 5, a three-phase grid-connected system is first constructed based on the differential equation of the AHO-VOC oscillator model of formula (1) (it should be noted that in order to achieve accurate coordination between the operating parameters and the AHO-VOC oscillator controller, the parameter analysis and control of the present invention are all carried out in a two-phase stationary coordinate system (αβ axis)). The core oscillation module of the three-phase grid-connected system is different from that of Figure 3 in that a controllable voltage source and a controllable current source that interact with the physical structure of the grid-connected system are added to achieve interaction with the power grid. As can be seen from Figure 5, the upper half is the physical structure of the three-phase inverter grid-connected system, where L f 、R f 、C f are the filter inductor, filter resistor and filter capacitor of the inverter respectively; L g 、R g are line inductance and line resistance respectively, V g , I g Represent the grid voltage and line current respectively.

[0068] In FIG5 , the output current of the inverter is compared with the output current reference value, and the difference signal obtained is used as feedback to participate in the control of the AHO-VOC output.

[0069] 1) Based on the instantaneous power calculation method, the inverter α-axis output current reference value and β-axis output current reference value The expression is:

[0070] 2) The expressions of the controllable current source command signal u1 and the controllable voltage source command signal u2 are:

[0071] 3) State variables x1 and x2 are corrected by voltage correction coefficient k v Generate α-axis output voltage v α and β-axis output voltage v β , whose expression is:

[0072] Where, P * is the active output reference value; Q * is the reactive output reference value; i α is the inverter α-axis output current; i β is the inverter β-axis output current; k i is the current correction factor; The rotation angle can be customized. Its value depends on the three-phase grid-connected system. Since the three-phase grid-connected system of the present invention is inductive, the value is selected. k v is the voltage correction factor.

[0073] S103, analysis of the AHO-VOC dynamic equation under three-phase grid-connected mode.

[0074] Based on equations (1)-(5), the dynamic model of the AHO-VOC oscillator in the three-phase grid-connected mode can be obtained as follows:

[0075] Substituting formula (5) into formula (22), the integrated formula (22) is simplified to:

[0076] In formula (23), is the time derivative of the inverter α-axis output voltage; The time derivative of the inverter axis β output voltage; V nom is the rated value of the inverter output voltage, V nom =k v X nom , in the three-phase grid-connected mode, the value can be set to the rated value of the grid-connected voltage, and v α 、v β It is an orthogonal sinusoidal signal, and its output voltage amplitude and phase angle can be expressed by equations (24) and (25) respectively:

[0077] By summarizing and integrating equations (23)-(25), we can obtain the dynamic equation (6) of the AHO-VOC output voltage and the dynamic equation (7) of the phase angle in the three-phase grid-connected mode;

[0078] Where, is the time derivative of the inverter α-axis output voltage; The time derivative of the inverter axis β output voltage; V nom is the rated value of the inverter output voltage RMS; P is the active power; Q is the reactive power.

[0079] In order to observe the relationship between each parameter and the output voltage more intuitively, considering that the system enters steady-state operation, the output voltage and phase angle no longer change (i.e., the voltage amplitude change rate dV / dt = 0, the output phase angle dθ / dt = ω nom ) Equations (6)-(7) can be further simplified to obtain:

[0080] It can be seen from formula (9) that the output frequency of the inverter in the three-phase grid-connected mode is locked to the grid frequency. At this time, the active power-frequency curve is linear. However, the reactive power-voltage relationship curve in formula (8) has obvious nonlinear characteristics and is affected by multiple parameters. The change law of the grid-connected characteristics is difficult to capture.

[0081] Step S2: Decoupling the dynamic equation of the AHO-VOC output voltage to derive an explicit expression of the AHO-VOC output voltage V.

[0082] As can be seen from the foregoing, the AHO-VOC reactive power-voltage relationship is unclear and is influenced by numerous internal and external parameters, making analysis difficult. Therefore, this paper decouples the dynamic equations for the AHO-VOC output voltage, derives an explicit expression for the AHO-VOC output voltage V, and analyzes and identifies the dominant parameters influencing the grid-connected output V.

[0083] S201, from formula (8), we can know that the output voltage V in steady state is affected by k v , k i ,ξ,V nom , Q * , Q and many other parameters have a common influence, and the dominant ability of each parameter cannot be directly obtained through the formula. Therefore, it is necessary to simplify and decouple the voltage-reactive dynamic equation first.

[0084] Based on the power angle relationship, the inverter output power is shown in formula (26):

[0085] Substituting formula (26) into formula (6) and (7), we can obtain:

[0086] Where δ is the phase difference between the inverter output voltage and the grid connection point voltage.

[0087] Set the reactive power reference value Q ref =0, formula (27) can be rewritten as:

[0088] S202, k v =V nom , k i =3V nom / S rated Substituting into equation (10) and solving, we obtain the explicit expression of the AHO-VOC output voltage V as follows:

[0089] Where, X T is the grid impedance; S rated is the rated apparent power of the inverter.

[0090] Although an explicit expression for the output voltage V is obtained from Equation (11), its variation pattern remains unclear. To address this issue, we will use data fitting to plot the relationship between various internal and external parameters and the system output voltage V, thereby clarifying the dominant parameters that affect the variation of the grid-connected output V.

[0091] Step S3 , analyzing the impact of changes in various internal and external parameters of the AHO-VOC controller on the AHO-VOC grid-connected output characteristics, and determining the dominant parameters that affect the change in the output voltage V.

[0092] S301, the impact of external parameter changes on the AHO-VOC grid-connected output characteristics

[0093] In the AHO-VOC controller design, k v It is often accompanied by changes in regulatory needs, so k v and V g are considered together as external parameters.

[0094] Based on this, the output voltage V is drawn, the grid voltage V g And the voltage correction factor k v The AHO-VOC grid-connected characteristic curve composed of the three is shown in Figure 6. As shown in Figure 6, the AHO-VOC output voltage V is affected by V g and k v However, in different value ranges, the dominant parameters affecting the output voltage V will be different. v When the value is within the range of 120-240, V g This is the dominant parameter that affects the output voltage V, which is conducive to achieving adaptive communication-free tracking of grid fluctuations.

[0095] S302, the impact of internal parameter changes on AHO-VOC grid-connected output characteristics

[0096] V g With k v As the dominant parameter affecting the system output, its interaction with the output has been analyzed in S301, but ξ, C, X T The impact of internal parameters such as is still unknown. Based on this, the impact of internal parameter changes on the grid-connected output characteristics of AHO-VOC will be discussed in detail here.

[0097] (1) Oscillation capacitor C

[0098] From the basic properties of the oscillator, we know that the oscillation capacitor C is used to determine the output oscillation frequency of AHO-VOC, and its value must meet the following requirements:

[0099] The grid-connected system is simulated with the oscillation capacitor C being 0.5 times, 1 times, and 2 times the reference value (the simulation parameters refer to the relevant parameter specifications of the power system). The AHO-VOC grid-connected output characteristic curve with the change of the oscillation capacitor C is plotted as shown in Figure 7. As can be seen from Figure 7, the change of the oscillation capacitor C has little effect on the AHO-VOC grid-connected output characteristic, and only slightly changes the V gk as the dominant parameter of the output voltage V v Value range.

[0100] (2) Changes in grid strength

[0101] The integration of large-scale renewable energy into the power grid affects the strength of the grid. The short circuit ratio (SCR) is a physical quantity that characterizes the strength of the system, and its expression is as shown in Equation (30):

[0102] Where U N is the rated voltage of the grid connection point, P N In order to fully consider the influence of different grid strength on the grid-connected output characteristics of AHO-VOC, the grid-connected system is simulated by changing the line resistance to simulate the three cases when SCR is 3, 2, and 1 (the simulation parameters refer to the relevant parameter specifications of the power system), and the AHO-VOC grid-connected output characteristic curve is drawn as shown in Figure 8. It can be seen from Figure 8 that the change of grid strength (i.e. the internal parameter X T The change of V also has little impact on the overall trend of the AHO-VOC grid-connected output characteristic curve. However, as the power grid strength weakens, maintaining V g k is the dominant parameter v The value range will be further narrowed.

[0103] (3) Convergence coefficient ξ

[0104] [Corrected 28.02.2024 according to Rule 91] From formula (20), it can be seen that the larger the value of ξ, the shorter the time required for AHO-VOC to reach steady state. When ξ is selected as 0.2, 2, 20, and 50, the AHO-VOC grid-connected output characteristic curve is plotted as shown in Figure 9. From the comparative analysis of Figures 9(a)-(d), it can be seen that the AHO-VOC grid-connected output characteristic curve is significantly changed by the change of ξ. When the convergence coefficient ξ is small, V g It can still maintain the dominant position of influencing the output voltage V. Specifically, when the value of ξ is less than 10, V g is the dominant parameter affecting the output voltage V. However, when ξ increases further, k v The dominant force on the output voltage V gradually increases. When ξ reaches a certain value, such as when ξ = 50 in Figure 9(d), k v Gaining complete dominance is not conducive to AHO-VOC's real-time tracking of system voltage.

[0105] Step S4 , designing key parameters of the grid-connected system considering the adaptability of the AHO-VOC three-phase grid-connected system.

[0106] From the above analysis, we can see that when V gWhen it is the dominant parameter affecting the system output voltage V, it is beneficial for the inverter to follow the grid. However, its dominant position is greatly affected by the change of the convergence coefficient ξ, so it is necessary to reasonably design ξ:

[0107] First, the relevant parameters need to be normalized as shown below:

[0108] Substituting formula (12) into formula (6) and (7) yields:

[0109] In order to achieve the adaptability of the designed parameters under extreme working conditions, the working conditions of the AHO-VOC system with the maximum frequency deviation and the maximum amplitude deviation are considered as shown in formula (15):

[0110] Arranging equations (13)-(15) and simplifying them, we can obtain the calculation formula related to the convergence coefficient ξ:

[0111] From formula (17), we can see that the value of the oscillation capacitor C is mainly related to the rated active reference P rated and the maximum frequency deviation value Δf (usually 0.2Hz in design). According to formulas (12), (16), (17), and (29), the values ​​of the key parameters of the grid-connected system are calculated as follows: oscillation capacitance C = 0.7829F, convergence coefficient ξ = 1.299, and oscillation inductance L = 12.94e-6H. The simulation parameters of the AHO-VOC grid-connected system in this calculation process refer to the relevant parameter specifications of the power system, as shown in Table 1 below:

[0112] Table 1 Simulation parameters

[0113] Step S5: determining the relationship expressions between the dominant parameters and the output voltage V in different sections.

[0114] In order to analyze whether AHO-VOC can achieve output voltage tracking with grid voltage under the condition of grid voltage drop, the present invention needs to determine the segmented quantization of AHO-VOC output voltage under different grid voltage drop levels. The grid voltage V can be adjusted by the key parameters of the grid-connected system determined above and the simulation parameters in Table 1. g The grid voltage V under these parameters is plotted as AHO-VOC grid connection. g The relationship curve between the output voltage V and the grid voltage V is shown in Figure 10. g It is nonlinear, and based on this, a piecewise linearization curve as shown in Figure 11 can be drawn, and V in different sectionsg The relationship between V and γ can be accurately expressed as shown in the following formula (18):

[0115] Where V g The unit of V is volts.

[0116] The above embodiments are preferred implementation schemes of the present invention. In addition, the present invention can also be implemented in other ways. Any obvious replacement without departing from the concept of the present technical solution is within the scope of protection of the present invention.

[0117] In order to make it easier for ordinary technicians in this field to understand the improvements of the present invention over the prior art, some drawings and descriptions of the present invention have been simplified, and for the sake of clarity, some other elements are omitted in this application document. Ordinary technicians in this field should realize that these omitted elements may also constitute the content of the present invention.

Claims

1. A method for quantitatively characterizing AHO-VOC output characteristics, characterized in that: include: Step S1, establishing a dynamic equation of the AHO-VOC output voltage and phase angle in the three-phase grid-connected mode, and determining the nonlinear relationship between the AHO-VOC reactive power and voltage and the linear relationship between the active power and frequency when the grid-connected system enters steady-state operation according to the dynamic equation; Step S2, decoupling the dynamic equation of the AHO-VOC output voltage, and deriving an explicit expression of the AHO-VOC output voltage V; Step S3, analyzing the influence of changes in various internal and external parameters of the AHO-VOC controller on the AHO-VOC grid-connected output characteristics, and determining the dominant parameters that affect the change in the output voltage V; Step S4, designing the key parameters of the grid-connected system considering the adaptability of the AHO-VOC three-phase grid-connected system; Step S5, based on the key parameters designed in step S4, draw a relationship curve between the dominant parameters and the output voltage V, and determine the relationship expression between the dominant parameters and the output voltage V in different sections.

2. The AHO-VOC output characteristic quantitative characterization method according to claim 1, characterized in that: The step S1 comprises: S101, based on the first-order nonlinear oscillator, construct an AHO-VOC oscillator model, and determine the differential equation of the AHO-VOC oscillator model, which is: Where ξ is the convergence coefficient of the oscillator; X nom is the amplitude of the output oscillation waveform; ω nom is the rated angular frequency of the oscillator; are the time-varying derivatives of x1 and x2 respectively; ||x|| is the Euclidean norm related to x1 and x2; x1 and x2 are both state variables, representing the oscillating capacitor voltage v C And the corrected oscillating inductor current εi L , the ε expression is: In the formula, L is the oscillation inductance; C is the oscillation capacitance; S102, build a three-phase grid-connected system based on the AHO-VOC oscillator model built in S101, and determine the reference value of the inverter α-axis output current and β-axis output current reference value The controllable current source command signal u1 and the controllable voltage source command signal u2, as well as the inverter α-axis output voltage v α With β axis output voltage v β , respectively as follows: Where P * is the active output reference value; Q * is the reactive output reference value; i α is the inverter α-axis output current; i β is the inverter β-axis output current; k i is the current correction factor; k v is the voltage correction factor; S103, based on equations (1)-(5), first determine the dynamic equation (6) of the AHO-VOC output voltage and the dynamic equation (7) of the phase angle in the three-phase grid-connected mode; In the formula, is the time derivative of the inverter α-axis output voltage; The derivative of the inverter axis β output voltage over time; V nom is the rated value of the inverter output voltage RMS; P is the active power; Q is the reactive power; V nom =k v X nom ; According to the dynamic equation (6) of the AHO-VOC output voltage, it is determined that when the grid-connected system enters steady-state operation, the reactive power-voltage relationship of AHO-VOC is nonlinear, and its expression is: According to the dynamic equation (7) of the AHO-VOC phase angle, it is determined that when the grid-connected system enters steady-state operation, the active power of AHO-VOC and the frequency are in a linear relationship, and the expression is:

3. The AHO-VOC output characteristic quantitative characterization method according to claim 2, characterized in that: The step S2 comprises: S201, substitute the inverter output power based on the power angle relationship into the dynamic equation (6) of the AHO-VOC output voltage, and set the reactive power reference value Q ref =0, we get: S202, k v =V nom , k i =3V nom / S rated Substituting into equation (10) and solving, we get the explicit expression of the AHO-VOC output voltage V as follows: Where V g represents the grid voltage; δ is the phase difference between the inverter output voltage and the grid connection point voltage; X T is the grid impedance; S rated is the rated apparent power of the inverter.

4. The AHO-VOC output characteristic quantitative characterization method according to claim 3, characterized in that: In step S3, the external parameter is V g , k v , the internal parameters are C, X T , ξ; 1) Considering the adaptability of AHO-VOC three-phase grid connection, k v When the value is in the range of 120-240, V g is the dominant parameter affecting the output voltage V; 2) C, X T The change of V has little effect on the grid-connected output characteristics of AHO-VOC, but affects V g k as the dominant parameter of the output voltage V v Value range; 3) Considering the adaptability of AHO-VOC three-phase grid connection, when the value of ξ is less than 10, V g It is the dominant parameter affecting the output voltage V.

5. The AHO-VOC output characteristic quantitative characterization method according to claim 4, characterized in that: In step S4, the process of designing the key parameters of the grid-connected system considering the adaptability of the AHO-VOC three-phase grid-connected system is as follows: First, normalize the following parameters: Substituting equation (12) into equations (6) and (7), we obtain: Next, consider the AHO-VOC system with a maximum frequency deviation of Δf = 0.2 and a maximum amplitude deviation of ΔV = 5% as shown in the following equation: Arranging equations (13)-(15) and simplifying them, we obtain: Finally, according to formulas (12), (16), and (17), the values ​​of the key parameters of the grid-connected system are calculated as follows: Oscillation capacitance C = 0.7829F, convergence coefficient ξ = 1.299; In formulas (12), (16), and (17), V nom is the rated value of the inverter output voltage RMS, which is 230V; V min is the minimum output voltage of the inverter, V min The per unit value of Take 0.95pu; P rated is the rated active power of the inverter, which is 5500W; S rated is the rated apparent power of the inverter, which is 5590VA; nom is the rated angular frequency of the oscillator, and its value is 314.16Hz; ω min It is the minimum angular frequency of the oscillator, and its value is 312.744Hz.

6. The AHO-VOC output characteristic quantitative characterization method according to claim 5, characterized in that: In step S5, based on the key parameters designed in step S4, V g As the dominant parameter affecting the output voltage V, plotting V g The relationship curve between the output voltage V and the output voltage V is used to determine the V g The relationship between the output voltage V is: Where V g The unit of V is volts.

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