A control parameter adjustment method based on the stability domain of multi-grid-connected inverter system

Abstract

The present application provides a control parameter adjustment method based on the stability domain of a multi-grid-connected inverter system, including: obtaining a first proportional coefficient and a first current reference value of a current controller of a single-grid-connected inverter; obtaining an effective grid impedance matrix of the multi-grid-connected inverter system; determining a single-condition multi-grid-connected inverter system loop gain matrix eigenvalue Bode diagram corresponding to a single-grid-connected inverter based on the first proportional coefficient and the first current reference value, and the effective grid impedance matrix of the multi-grid-connected inverter system; determining a single-condition multi-grid-connected inverter system stability domain three-dimensional point based on the single-condition multi-grid-connected inverter system loop gain matrix eigenvalue Bode diagram; determining a multi-condition multi-grid-connected inverter system stability domain three-dimensional diagram corresponding to a single-grid-connected inverter based on the single-condition multi-grid-connected inverter system stability domain three-dimensional point; adjusting the first proportional coefficient and the first current reference value based on the multi-condition multi-grid-connected inverter system stability domain three-dimensional diagram. The adjustment process is simple to operate and easy to implement.

Description

Technical Field

[0001] The present application relates to the field of power grids, and in particular to the technical field of grid-connected inverters. Background Art

[0002] With the continuous increase in the installed capacity of new energy power generation systems, represented by photovoltaics and wind turbines, a new power system with "double high" characteristics has gradually taken shape, and the power grid has also shown increasingly weak characteristics, resulting in the influence of grid impedance on the stability of new energy power generation systems that cannot be ignored, especially when multiple distributed new energy grid-connected converters are connected to the grid. The existence of grid impedance will seriously affect the stability of multi-machine distributed photovoltaic grid-connected systems, restricting the high penetration rate access and local consumption of photovoltaic power generation.

[0003] With the formation of the "double-high" power system, in addition to the grid-connected instability problem caused by the interaction of the internal control links of the PGCI system, the stability problem caused by the interaction between photovoltaic inverters will be more serious. In response to the difficulty of improving stability under multi-machine parallel connection, existing research focuses on power adjustment, control loop parameter optimization, and additional auxiliary control loop improvement methods. At present, the stability improvement method of the inverter system using control loop parameter optimization requires analysis of the influence mechanism of control parameters on system stability, and the analysis process is relatively complicated; the stability improvement method using additional auxiliary control loops is very likely to add additional control variables and increase the difficulty of parameter design of the auxiliary control loop. Therefore, how to adjust the control parameters of the inverter more simply and quickly on the basis of retaining the original control loop of the inverter, thereby improving the adaptability of the grid-connected inverter multi-machine parallel system to the grid impedance is a problem that technicians in this field urgently need to solve. Summary of the invention

[0004] In order to overcome the above technical defects, the present application provides a control parameter adjustment method based on the stability domain of a multi-grid-connected inverter system, comprising:

[0005] Acquire a first proportional coefficient and a first current reference value of a current controller of a single grid-connected inverter;

[0006] Obtaining the effective grid impedance matrix of the multi-grid-connected inverter system;

[0007] Determine a Bode diagram of eigenvalues ​​of a loop gain matrix of a single-operating-state multi-grid-connected inverter system corresponding to a single grid-connected inverter based on the first proportionality coefficient and the first current reference value and the effective grid impedance matrix of the multi-grid-connected inverter system;

[0008] Determine the three-dimensional point of the stability domain of the single-operating-state multi-grid-connected inverter system based on the eigenvalue Bode diagram of the loop gain matrix of the single-operating-state multi-grid-connected inverter system;

[0009] Based on the three-dimensional point of the stability domain of the single-operating-state multi-grid-connected inverter system, determining a three-dimensional graph of the stability domain of the multi-operating-state multi-grid-connected inverter system corresponding to the single-grid-connected inverter;

[0010] Based on the three-dimensional diagram of the stability domain of the multi-operating-condition multi-grid-connected inverter system, the first proportional coefficient and the first current reference value are adjusted.

[0011] Optionally, before the step of obtaining the effective grid impedance matrix of the multi-grid-connected inverter system, the step includes:

[0012] Obtain the admittance matrix of power grid structure nodes;

[0013] Based on the grid structure node admittance matrix, an effective grid impedance matrix of a multi-grid-connected inverter system is determined.

[0014] Optionally, the grid-connected inverter further includes a main circuit LCL filter, and the determining of a single-operating-state multi-grid-connected inverter system loop gain matrix eigenvalue Bode diagram corresponding to a single grid-connected inverter based on the first proportionality coefficient and the first current reference value, and the multi-grid-connected inverter system effective grid impedance matrix includes:

[0015] Based on the first proportionality coefficient, determining a first transfer function of a current controller corresponding to a single grid-connected inverter;

[0016] Obtaining a main circuit LCL filter parameter corresponding to a single grid-connected inverter, and determining a main circuit second transfer function corresponding to the single grid-connected inverter;

[0017] Based on the first current reference value, determining a first conversion matrix of calculated angle parameters and actual angle parameters corresponding to a single grid-connected inverter;

[0018] Determine a single inverter output admittance matrix based on the first transfer function, the second transfer function, and the first conversion matrix;

[0019] Based on the single inverter output admittance matrix and the effective grid impedance matrix of the multi-grid-connected inverter system, a single-operating-state multi-grid-connected inverter system loop gain matrix eigenvalue Bode diagram corresponding to the single grid-connected inverter is determined.

[0020] Optionally, determining a single-operating-state multi-grid-connected inverter system loop gain matrix eigenvalue Bode diagram corresponding to a single grid-connected inverter based on the output admittance matrix of the single grid-connected inverter and the effective grid impedance matrix of the multi-grid-connected inverter system comprises:

[0021] Based on the output admittance matrix of the single grid-connected inverter, determining the admittance diagonal matrix of multiple grid-connected inverters;

[0022] Determine a loop gain matrix of a single-operating-state multi-grid-connected inverter system corresponding to a single grid-connected inverter based on the effective grid impedance matrix of the multi-grid-connected inverter system and the admittance diagonal matrix of the multiple grid-connected inverters;

[0023] Based on the single-operating-state multi-grid-connected inverter system loop gain matrix, a single-operating-state multi-grid-connected inverter system gain matrix eigenvalue Bode diagram corresponding to the single grid-connected inverter is determined.

[0024] Optionally, determining a single-operating-state multi-grid-connected inverter system gain matrix eigenvalue Bode diagram corresponding to a single-operating-state multi-grid-connected inverter based on the single-operating-state multi-grid-connected inverter system loop gain matrix includes:

[0025] Based on the single-operating-state multi-grid-connected inverter system loop gain matrix, determining a first numerical eigenvalue of the single-operating-state multi-inverter system loop gain matrix;

[0026] Based on the single-operating-condition first number eigenvalues ​​of the multi-inverter system loop gain matrix, a single-operating-condition multi-grid-connected inverter system gain matrix eigenvalue Bode diagram corresponding to a single grid-connected inverter is determined.

[0027] Optionally, determining the three-dimensional point of the stability domain of the single-operating-state multi-grid-connected inverter system based on the eigenvalue Bode diagram of the loop gain matrix of the single-operating-state multi-grid-connected inverter system comprises:

[0028] Determine the stability margin of the single-operating-state multi-grid-connected inverter system based on the eigenvalue Bode diagram of the loop gain matrix of the single-operating-state multi-grid-connected inverter system;

[0029] Based on the eigenvalue-based single-operating-state multi-grid-connected inverter system stability margin, a three-dimensional point of the single-operating-state multi-grid-connected inverter system stability domain is determined.

[0030] Optionally, determining the stability margin of the single-operating-state multi-grid-connected inverter system based on the eigenvalue Bode diagram of the loop gain matrix of the single-operating-state multi-grid-connected inverter system comprises:

[0031] Determine multiple stability margins corresponding to the eigenvalue Bode diagram of the loop gain matrix of the single-operating-state multi-grid-connected inverter system based on the eigenvalue Bode diagram of the loop gain matrix of the single-operating-state multi-grid-connected inverter system;

[0032] Based on the multiple stability margins, a stability margin of the single-operating-state multi-grid-connected inverter system based on characteristic values ​​is determined.

[0033] Optionally, based on the multiple stability margins, determining a stability margin of a single-operating-condition multi-grid-connected inverter system based on characteristic values ​​includes:

[0034] From the multiple stability margins, the smallest stability margin among the multiple stability margins corresponding to the single inverter is selected as the stability margin of the single-operating-mode multi-grid-connected inverter system based on the characteristic value.

[0035] This application has the following beneficial effects:

[0036] The parameter adjustment method proposed in the present application, without changing the original converter control structure, constructs a three-dimensional point of the stability domain of a single-condition multi-grid-connected system through a first proportional coefficient and a first current reference value, as well as an effective grid impedance matrix of a multi-grid-connected inverter system, and then constructs a three-dimensional diagram of the stability domain of a multi-condition multi-grid-connected inverter system corresponding to a single grid-connected inverter. The form is simple, and the entire process is simple and easy to operate. The actual operating condition of a single inverter is located through a three-dimensional operation diagram, and the corresponding parameters are changed in real time through the three-dimensional operation diagram to ensure high stability margin operation of the system.

[0037] In addition to the above-described purposes, features and advantages, the present application also has other purposes, features and advantages. The present application will be further described in detail below with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] The drawings constituting a part of the present application are used to provide a further understanding of the present application. The illustrative embodiments and descriptions of the present application are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0039] Figure 1 It is a flow chart of a control parameter adjustment method based on a multi-grid-connected inverter system stability domain provided in an embodiment of the present application.

[0040] Figure 2 It is a main circuit structure diagram of the grid-connected inverter control structure domain provided in an embodiment of the present application.

[0041] Figure 3 It is a Bode diagram of the eigenvalues ​​of the loop gain matrix of a single-operating-mode multi-grid-connected inverter system provided in an embodiment of the present application.

[0042] Figure 4 It is a three-dimensional diagram of the stability domain of a multi-operating-condition and multi-grid-connected inverter system provided in an embodiment of the present application.

[0043] Figure 5 This is a schematic diagram of the grid-connected point current of multiple inverters with single inverter parameters set at (7e-3, 35, 1) in the experimental verification provided by the embodiment of the present application.

[0044] Figure 6 This is a schematic diagram of the grid-connected point current of multiple inverters with single inverter parameters set at (7e-3, 20, 2) in the experimental verification provided by the embodiment of the present application. DETAILED DESCRIPTION

[0045] The embodiments of the present application are described in detail below with reference to the accompanying drawings; however, the present application can be implemented in many different ways as defined and covered by the claims.

[0046] Since there are multiple nouns in this application, in order to avoid deviations in understanding this document, the above nouns are explained in detail here.

[0047] Therefore, in order to solve the above problems, Figure 1 As shown, the present application proposes a control parameter adjustment method based on a multi-grid-connected inverter system stability domain, wherein the grid-connected inverter includes a current controller, including:

[0048] Step S101: obtaining a first proportional coefficient and a first current reference value of the current controller of the single grid-connected inverter;

[0049] In order to understand the content of this application, Figure 2 As shown, the structure of the grid-connected inverter of the present application is briefly introduced. The grid-connected inverter includes an inverter control system and an inverter main circuit, wherein the control system includes: a phase-locked loop PLL, a current loop and a PWM modulation sampling module, wherein the inverter main circuit includes: a DC voltage source Vdc, a three-bridge arm inverter, and an LCL filter. The grid-connected inverter single-machine system obtains the actual value of the grid-connected current and the PCC grid-connected point phase angle by the current controller PI, compares the grid-connected current after the PCC grid-connected point phase angle transformation with the controller circuit reference value, and then outputs a voltage control signal after passing through the current controller PI, and obtains the inverter bridge arm control signal after PWM modulation, and the current controller includes: a d-axis PI controller, a q-axis PI controller, a d-axis current control loop, and a q-axis current control loop.

[0050] The d-axis current control loop and the q-axis current control loop each include a PI controller. The first proportional coefficient in this application is the proportional coefficient of the d-axis PI controller. and the proportional coefficient of the q-axis PI controller The first current reference value in this application is the current reference value of the d-axis Or the current reference value of the q axis . When the inverter is connected to the grid, the proportional coefficient can be used to adjust the match between the inverter output and the grid parameters. For example, in some application scenarios that need to meet specific power factor requirements, the output ratio of reactive power and active power is controlled by adjusting the proportional coefficient, thereby improving the power quality after the inverter is connected to the grid, ensuring that the inverter can better interact with the grid, and reducing adverse effects such as harmonic pollution on the grid. At the macro-dispatching level of the grid, the current reference value is an important means to achieve a balance between power supply and demand. The grid dispatching center can allocate current reference values ​​to each power generation unit (including traditional power plants and distributed power sources) based on the power generation plan and load forecast. The power generation unit adjusts its output according to these reference values ​​to ensure that the power supply and demand of the grid can be balanced at any time to avoid power shortages or surpluses. For example, during peak hours, by increasing the current reference value of the power generation unit, the power supply is increased to meet the power demand of users.

[0051] Step S102: Obtaining an effective grid impedance matrix of a multi-grid-connected inverter system;

[0052] The effective grid impedance matrix of a multi-grid-connected inverter system is a matrix used to describe the electrical characteristics of the mutual coupling between multiple grid-connected inverters and the grid. It reflects the equivalent impedance of the grid seen from each inverter port, as well as the coupling impedance between different inverter ports through the grid. The specific acquisition process is shown in formula (1). First, the grid structure node admittance matrix is ​​obtained: Then, based on the grid architecture node admittance matrix, the key nodes of the inverter access are located, so that the key node elements in the grid architecture impedance are selected and combined to obtain the effective grid impedance matrix of the multi-grid-connected inverter system. lg is generally used to refer to the large grid impedance of a multi-grid-connected inverter system:

[0053] (1)

[0054] Step S103: determining a Bode diagram of the loop gain matrix eigenvalues ​​of the single-operating-state multi-grid-connected inverter system corresponding to a single grid-connected inverter based on the first proportionality coefficient and the first current reference value and the effective grid impedance matrix of the multi-grid-connected inverter system;

[0055] Single operating condition refers to the analysis of the system under specific, single operating conditions. The working conditions corresponding to the single operating condition in this application include the first proportional coefficient and the first current reference value of the single inverter current controller, and the effective grid impedance matrix of the multi-grid-connected inverter system. In other words, the single operating condition in this application refers to the specific operating condition when the single inverter in the system is determined and fixed one by one when the first proportional coefficient and the first current reference value, as well as the values ​​in the effective grid impedance matrix of the multi-grid-connected inverter system.

[0056] After obtaining the above first proportional coefficient, the first transfer function of the current controller corresponding to the single grid-connected inverter can be calculated according to formula (2): , that is d Axis control loops and d Transfer function of the PI controller in the axis control loop for:

[0057] (2)

[0058] In the formula, Respectively d Proportional and integral coefficients of the axis PI controller; Respectively q Proportional and integral coefficients of the axis PI controller, is the Laplace operator.

[0059] The grid-connected inverter also includes a main circuit LCL filter. The main circuit LCL filter parameters corresponding to the single grid-connected inverter are obtained. According to formulas (3) and (4), the second transfer function of the main circuit corresponding to the single grid-connected inverter can be determined: and :

[0060] (3)

[0061] (4)

[0062] in, They represent the capacitance transfer function impedance matrix of the LCL filter, the inductance transfer function admittance matrix of the inverter output port, and the inductance transfer function admittance matrix of the grid-connected point side. represents the unit diagonal matrix, and its expressions are:

[0063] (5)

[0064] (6)

[0065] (7)

[0066] (8)

[0067] In the formula They represent the inductance parameters of the inverter output port and the grid-connected point side in the LCL filter respectively; Indicates the filter capacitor parameters in the LCL filter; represents the series resistance of the filter capacitor in the LCL filter, Indicates that the power grid frequency is 50H, represents the unit diagonal matrix.

[0068] After obtaining the first current reference value, the first conversion matrix of the calculated angle parameter and the actual angle parameter corresponding to the single grid-connected inverter can be determined according to the first current reference value. That is, after obtaining the first current reference value, it can be input into the inverter control circuit through dq decomposition for feedback control. During the dq decomposition process, the first conversion matrix of the calculated angle parameter and the actual angle parameter introduced by the PLL structure is:

[0069] (9)

[0070] (10)

[0071] Where HPI is the PI controller transfer function in the PLL phase-locked loop, ; and They are the steady-state values ​​of the output modulation quantity of the current loop PI regulator; and The inverter output current is d axis, q Steady-state value of axis component; The grid-connected inverter grid-connected point voltage d Steady-state value of the axis component.

[0072] After obtaining the first transfer function, the second transfer function, and the first conversion matrix, the output admittance matrix of the single inverter can be calculated and determined, as shown in formula (11):

[0073] (11)

[0074] In the formula, Usually refers to the gain factor of the PWM controller (or modulator). This factor plays an important role in the control circuit of the inverter.

[0075] After obtaining the output admittance matrix of the single grid-connected inverter and the effective grid impedance matrix of the multi-grid-connected inverter system, the eigenvalue Bode diagram of the loop gain matrix of the single-operating-state multi-grid-connected inverter system corresponding to the single grid-connected inverter can be determined. The specific process is as follows:

[0076] Since the application selects a single inverter with the weakest stability, after obtaining the output admittance matrix of the single grid-connected inverter, the output admittance matrices of multiple other grid-connected inverters can also be calculated according to the above calculation formulas (2)-(11), and then the admittance matrices of multiple grid-connected inverters can be combined to obtain the admittance diagonal matrix of multiple grid-connected inverters: :

[0077] (12)

[0078] After obtaining the admittance matrix of multiple grid-connected inverters, based on the admittance diagonal matrix of multiple grid-connected inverters and the effective grid impedance matrix of the multi-grid-connected inverter system obtained previously, the loop gain matrix of the single-operating-state multi-grid-connected inverter system corresponding to the single grid-connected inverter can be obtained. , as shown in the following formula (13):

[0079] (13)

[0080] After obtaining the loop gain matrix of the single-operating-state multi-grid-connected inverter system, the specific calculation process can be as follows based on the eigenvalue Bode diagram of the loop gain matrix of the single-operating-state multi-grid-connected inverter system:

[0081] The loop gain matrix of the single-operating-condition multi-grid-connected inverter system is calculated to obtain a first numerical eigenvalue of the loop gain matrix of the single-operating-condition multi-inverter system corresponding to the single grid-connected inverter. The first number is generally related to the connected inverter. For example, if n inverters are connected, the first number corresponding to the single operating condition is 2n.

[0082] Then, according to the first number eigenvalue of the gain matrix of the single-operating-state multi-grid-connected inverter system, the eigenvalue Bode diagram of the gain matrix of the single-operating-state multi-grid-connected inverter system corresponding to the single-grid-connected inverter is determined. That is to say, if the number of connected inverters is n, for each single operating condition, 2n eigenvalue Bode diagrams of the gain matrix of the single-operating-state multi-grid-connected inverter system can be obtained. Figure 3 As shown, this is one of the eigenvalue Bode diagrams corresponding to the operating point (7e-3,35,1).

[0083] Step S104: determining a three-dimensional point in the stability domain of the single-operating-state multi-grid-connected inverter system based on the Bode diagram of the eigenvalues ​​of the loop gain matrix of the single-operating-state multi-grid-connected inverter system;

[0084] The three-dimensional point of the stability domain of the multi-grid-connected inverter system refers to a point in the three-dimensional parameter space composed of the first proportional coefficient, the first current reference value and the effective grid impedance matrix of the multi-grid-connected inverter system. Under the parameter combination corresponding to this point, the multi-grid-connected inverter system can operate stably, that is, the output of the system (such as voltage, current, etc.) can remain bounded within a certain range, and there will be no continuous oscillation, loss of control and other unstable phenomena. The collection of these three-dimensional points constitutes the stability domain of the multi-grid-connected inverter system, which is used to evaluate and predict the stability of the system under different parameter values.

[0085] After obtaining the Bode diagram of the eigenvalue of the loop gain matrix of the single-operating-state multi-grid-connected inverter system, the three-dimensional point of the stability domain of the single-operating-state multi-grid-connected inverter system can be determined. The specific calculation method is as follows:

[0086] Based on the Bode diagram of the loop gain matrix eigenvalue of the single-operating-state multi-grid-connected inverter system, multiple stability margins (phase margin Phase, amplitude margin Mg) based on eigenvalues ​​are defined, and the calculation formula is (14):

[0087] (14)

[0088] in, is the nth eigenvalue vector; angle(Mg_location) and Mg(angle_location) represent the phase and amplitude margins of the nth eigenvalue, respectively.

[0089] It should be noted that if the system is connected to n inverters, each eigenvalue of the system loop gain matrix corresponds to multiple different stability margins, and then 2n eigenvalues ​​under a single operating condition are calculated, and two stability margins are corresponding to each eigenvalue. Then, the stability margin of the single-operating-condition multi-grid-connected inverter system based on the eigenvalue is determined from the multiple stability margins of the multiple eigenvalues. That is, from the multiple stability margins calculated, the one with the smallest stability margin value is selected as the stability margin of the single-operating-condition multi-inverter system based on the eigenvalue.

[0090] After calculating the stability margin of the single-operating-condition multi-inverter system, the three-dimensional points of the stability domain of the single-operating-condition multi-grid-connected inverter system corresponding to the single inverter can be drawn according to the stability system of the multi-inverter system. The three-dimensional point information includes the inverter stability and stability margin information under the operating condition.

[0091] Step S105: Based on the three-dimensional point of the stability domain of the single-operating-condition multi-grid-connected inverter system, determine a three-dimensional graph of the stability domain of the multi-operating-condition multi-grid-connected inverter system corresponding to the single grid-connected inverter;

[0092] After obtaining the three-dimensional point of the stability domain of the single-operating-condition multi-grid-connected inverter system, the three-dimensional diagram of the stability domain of the single inverter and the multi-grid-connected inverter system under multiple operating conditions can be obtained by adjusting the first current reference value, the first proportional coefficient, and the value of the effective grid impedance matrix of the multi-grid-connected inverter system.

[0093] It should be noted that, since the calculation will also obtain the corresponding three-dimensional points of some systems in an unstable state, which will also be reflected in the three-dimensional diagram of the stability domain of the multi-condition multi-grid-connected inverter system, in order to distinguish them, three-dimensional points of different colors are generally used to represent them. Figure 4As shown, the blue points in the figure are the corresponding single operating conditions when the multi-grid-connected inverter system is stable, and the red points are the corresponding single operating conditions when the multi-grid-connected inverter system is unstable.

[0094] Step S106: Based on the three-dimensional diagram of the stability domain of the multi-operating-condition and multi-grid-connected inverter system, adjust the first proportional coefficient and the first current reference value.

[0095] After obtaining the three-dimensional diagram of the stability domain of the multi-working condition multi-grid-connected inverter system, it can be clearly obtained that the corresponding system stability of the single inverter under different working conditions, when the system is unstable, select to adjust the first current reference value and the first proportional coefficient of the corresponding single working condition, and make corresponding adjustments. Since the impedance of the effective grid matrix of the multi-grid-connected inverter system is not easy to adjust, it is generally sufficient to adjust the first proportional number and the first current reference value.

[0096] Experimental verification phase:

[0097] In this embodiment, a three-phase LCL type distributed grid-connected inverter interconnection system is built in MATLAB / Simulink, and the three inverters use the same type of LCL filter device. The main parameters of the system are shown in Table 1:

[0098] ,

[0099] In order to verify the validity of the three-dimensional operating domain disclosed in the present invention, Figure 4 A three-dimensional operating domain of the multi-grid-connected inverter interconnection system disclosed in the present invention is provided.

[0100] observe Figure 4 , when the inverter 1 parameters are set to (7e-3,35,1), the three-dimensional operation domain shows that the multi-machine interconnected system will be unstable but the instability is not large, and it can return to a stable state by adjusting the parameters. At this time, under the same grid impedance of 7mH, the controller parameter kp and the grid-connected inverter operating current reference value Id0 are adjusted to make inverter 1 operate in the (7e-3,20,2) working condition. The three-dimensional operation domain shows that the multi-machine interconnected system will operate stably, and the system stability margin is high.

[0101] observe Figure 5 It can be seen that when the operating parameters of inverter 1 are set to (7e-3, 35, 1), the output current of the multi-machine interconnection system oscillates significantly when Lg is 7mH, which verifies the correctness of the parameter adjustment method proposed in this application.

[0102] observe Figure 6 It can be seen that when the operating parameters of inverter 1 are set to (7e-3, 20, 2), the output current of the multi-machine interconnection system is smoothly output when Lg is 7mH, which verifies the correctness of the parameter adjustment method proposed in this application.

[0103] The parameter adjustment method proposed in the present application, without changing the original converter control structure, constructs a three-dimensional point of the stability domain of a single-condition multi-grid-connected system through a first proportional coefficient and a first current reference value, as well as an effective grid impedance matrix of a multi-grid-connected inverter system, and then constructs a three-dimensional diagram of the stability domain of a multi-condition multi-grid-connected inverter system corresponding to a single grid-connected inverter. The form is simple, and the entire process is simple and easy to operate. The actual operating condition of a single inverter is located through a three-dimensional operation diagram, and the corresponding parameters are changed in real time through the three-dimensional operation diagram to ensure high stability margin operation of the system.

[0104] The above description is only the preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A control parameter adjustment method based on a multi-grid-connected inverter system stability domain, wherein the grid-connected inverter includes a current controller, characterized in that: include: Acquire a first proportional coefficient and a first current reference value of a current controller of a single grid-connected inverter; Obtaining the effective grid impedance matrix of the multi-grid-connected inverter system; Determine a Bode diagram of eigenvalues ​​of a loop gain matrix of a single-operating-state multi-grid-connected inverter system corresponding to a single grid-connected inverter based on the first proportionality coefficient and the first current reference value and the effective grid impedance matrix of the multi-grid-connected inverter system; Determine multiple stability margins corresponding to the eigenvalue Bode diagram of the loop gain matrix of the single-operating-state multi-grid-connected inverter system based on the eigenvalue Bode diagram of the loop gain matrix of the single-operating-state multi-grid-connected inverter system; From the multiple stability margins, select the smallest stability margin among the multiple stability margins corresponding to the single inverter as the stability margin of the single-operating-condition multi-grid-connected inverter system based on the characteristic value; Determining a three-dimensional point in the stability domain of the single-operating-state multi-grid-connected inverter system based on the eigenvalue-based single-operating-state multi-grid-connected inverter system stability margin; Based on the three-dimensional point of the stability domain of the single-operating-state multi-grid-connected inverter system, determining a three-dimensional graph of the stability domain of the multi-operating-state multi-grid-connected inverter system corresponding to the single-grid-connected inverter; Based on the three-dimensional diagram of the stability domain of the multi-operating-condition multi-grid-connected inverter system, the first proportional coefficient and the first current reference value are adjusted.

2. The method according to claim 1, characterized in that The step of obtaining the effective grid impedance matrix of the multi-grid-connected inverter system includes: Obtain the admittance matrix of power grid structure nodes; Based on the grid structure node admittance matrix, an effective grid impedance matrix of a multi-grid-connected inverter system is determined.

3. The method according to claim 1, wherein the grid-connected inverter further comprises a main circuit LCL filter, characterized in that: The determining of the loop gain matrix eigenvalue Bode diagram of the single-operating-state multi-grid-connected inverter system corresponding to the single grid-connected inverter based on the first proportionality coefficient and the first current reference value and the effective grid impedance matrix of the multi-grid-connected inverter system comprises: Based on the first proportionality coefficient, determining a first transfer function of a current controller corresponding to a single grid-connected inverter; Obtaining a main circuit LCL filter parameter corresponding to a single grid-connected inverter, and determining a main circuit second transfer function corresponding to the single grid-connected inverter; Based on the first current reference value, determining a first conversion matrix of calculated angle parameters and actual angle parameters corresponding to a single grid-connected inverter; Determine a single inverter output admittance matrix based on the first transfer function, the second transfer function, and the first conversion matrix; Based on the single inverter output admittance matrix and the effective grid impedance matrix of the multi-grid-connected inverter system, a single-operating-state multi-grid-connected inverter system loop gain matrix eigenvalue Bode diagram corresponding to the single grid-connected inverter is determined.

4. The method according to claim 3, characterized in that The determining of the eigenvalue Bode diagram of the loop gain matrix of the single-operating-condition multi-grid-connected inverter system corresponding to the single-grid-connected inverter based on the output admittance matrix of the single-grid-connected inverter and the effective grid impedance matrix of the multi-grid-connected inverter system comprises: Based on the output admittance matrix of the single grid-connected inverter, determining the admittance diagonal matrix of multiple grid-connected inverters; Determine a loop gain matrix of a single-operating-state multi-grid-connected inverter system corresponding to a single grid-connected inverter based on the effective grid impedance matrix of the multi-grid-connected inverter system and the admittance diagonal matrix of the multiple grid-connected inverters; Based on the single-operating-state multi-grid-connected inverter system loop gain matrix, a single-operating-state multi-grid-connected inverter system gain matrix eigenvalue Bode diagram corresponding to the single grid-connected inverter is determined.

5. The method according to claim 4, characterized in that The step of determining a single-operating-state multi-grid-connected inverter system gain matrix eigenvalue Bode diagram corresponding to a single-operating-state multi-grid-connected inverter based on the single-operating-state multi-grid-connected inverter system loop gain matrix includes: Based on the single-operating-state multi-grid-connected inverter system loop gain matrix, determining a first numerical eigenvalue of the single-operating-state multi-inverter system loop gain matrix; Based on the single-operating-condition first number eigenvalues ​​of the multi-inverter system loop gain matrix, a single-operating-condition multi-grid-connected inverter system loop gain matrix eigenvalue Bode diagram corresponding to a single grid-connected inverter is determined.

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