A method, system, device and medium for virtual impedance regulation and parameter optimization setting of a network-constructed converter

Abstract

The application discloses a network-constructing type converter virtual impedance adjusting and parameter optimization setting method, system, equipment and medium, and belongs to the technical field of novel power systems, which comprises the following steps: according to the optimization selection of the generalized power coordinate transformation angle of the network-constructing type converter, the virtual impedance of the network-constructing type converter is decomposed, the maximum value of the selected virtual impedance is obtained, the maximum value of the fixed item and the variable item of the virtual impedance is calculated through the maximum value of the virtual impedance, and the basic parameters of the virtual impedance are formed; the partial derivative of the generalized reactive power sharing value to the line impedance parameter is obtained through the implicit function theory, the optimal value of the advanced parameter of the virtual impedance is obtained according to the principle of minimizing the absolute value of the partial derivative, the real-time virtual impedance modulus value is obtained, and the virtual resistance and the virtual inductance are obtained by combining the preset virtual impedance angle with the real-time virtual impedance modulus value to control. The application greatly increases the virtual impedance adjusting flexibility by adjusting the virtual impedance, and thus reduces the apparent power sharing error, and the reactive power sharing error can be greatly reduced as a special case.

Description

Technical Field

[0001] This invention relates to the field of novel power system technology, specifically to a method, system, device, and medium for virtual impedance regulation and parameter optimization tuning of a grid-type converter. Background Technology

[0002] The large-scale integration of new energy sources with power electronics interfaces into the grid reduces grid inertia, posing significant challenges to the safe and stable operation of the power system. Grid-based technology is a crucial technology supporting new power systems with a high proportion of new energy and power electronic equipment. It can autonomously construct voltage, improve inertia, provide frequency and voltage support, and act as a black-start power source to enhance the power system's disaster prevention and mitigation capabilities. The large number of grid-based converters integrated into new power systems requires parallel operation. A key objective of parallel operation control for grid-based converters is for each converter to handle active and reactive loads as expected; for example, larger-capacity grid-based converters should handle more active and reactive loads. Virtual impedance, through control algorithms, reshapes the output impedance of grid-based converters, improving load sharing efficiency. Currently, to improve power sharing accuracy in grid-type converters without communication, virtual impedance tuning methods mainly include virtual impedance-reactive power droop and constant virtual impedance. The main problem with existing tuning methods is the lack of a quantitative relationship between the power sharing error of the grid-type converter and the virtual impedance tuning value. The tuning results in excessively large sharing errors under specific reactive load rate operating conditions, and the sharing error increases as the reactive load rate decreases, making it difficult to adapt to the wide range of reactive load rate changes in grid-type converters. This invention addresses this problem by proposing a new virtual impedance adjustment method. Based on this, a virtual impedance control parameter tuning method is proposed using nonlinear equation perturbation theory. A quantitative relationship is established between the virtual impedance tuning value and the power sharing error. Based on this quantitative relationship and the load rate of the grid-type converter, the virtual impedance control parameter is optimized, achieving better load sharing. Summary of the Invention

[0003] In view of the above-mentioned problems, the present invention is proposed.

[0004] Therefore, the problem solved by this invention is to: construct a quantitative relationship between virtual impedance and reactive power sharing error using the existing concept of generalized reactive power; under the guidance of the above quantitative relationship, propose an optimized virtual impedance parameter tuning method, which can reduce the generalized reactive power sharing error under a specific generalized reactive load rate when there is no communication between grid-connected converters, thereby reducing the apparent power sharing error; under the guidance of the above quantitative relationship, the optimized virtual impedance parameter tuning method can ensure that the generalized reactive load rate varies within a certain range and that the generalized reactive power sharing error is minimized when the generalized reactive load rate is a certain value, thereby significantly reducing the apparent power sharing error. As a specific example, if generalized reactive power is taken to be equal to reactive power, applying this invention can reduce the reactive power sharing error under a specific reactive load rate and also ensure that the reactive power sharing error is minimized when the reactive load rate is a certain value.

[0005] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a method for virtual impedance adjustment and parameter optimization tuning of a grid-type converter, comprising,

[0006] Based on the unit length resistance and reactance ratio information of the grid-type converter connected line, the generalized power coordinate transformation angle is optimized to reduce the coupling between generalized active power and generalized reactive power.

[0007] The virtual impedance of the grid-type converter is decomposed into fixed terms and variable terms. The variable terms are arbitrary monotonically non-decreasing functions of the generalized reactive power, and the variable terms are also positive when the generalized reactive power is positive.

[0008] The maximum virtual impedance value is selected based on the requirement that the voltage quality meets the maximum generalized reactive load. The maximum virtual impedance value is used to calculate the maximum values ​​of the virtual impedance fixed terms and variable terms, which constitute the basic parameters of the virtual impedance.

[0009] The partial derivative of the reactive power sharing value with respect to the line impedance parameter is obtained by implicit function theory, and the optimal value of the advanced parameter of virtual impedance is obtained according to the principle of minimizing the absolute value of the partial derivative.

[0010] The real-time virtual impedance magnitude is obtained based on the basic parameters, advanced parameters, and generalized reactive power of the virtual impedance. The virtual resistance and virtual inductance are obtained by combining the preset virtual impedance angle with the real-time virtual impedance magnitude, and the grid-type converter is controlled.

[0011] As a preferred embodiment of the virtual impedance adjustment and parameter optimization tuning method for a grid-type converter described in this invention, the optimization selection of the generalized power coordinate transformation angle includes, by reasonably selecting the generalized power coordinate transformation angle... Reduce the coupling between generalized active power and generalized reactive power, i.e., when multiple circuits... When the ratios are not equal, follow the decreasing order. and Control coupling selection between Take all lines The average of the ratios or taking Median value of the ratio;

[0012] Active power of grid converter and no merit Perform a power coordinate transformation to obtain the generalized active power. and generalized no merit The power coordinate transformation is as follows:

[0013] ;

[0014] .

[0015] As a preferred embodiment of the virtual impedance adjustment and parameter optimization method for a grid-type converter described in this invention, the virtual impedance includes adjustment of the virtual impedance through generalized reactive power, for the virtual impedance of the grid-type converter with index i. for:

[0016] ;

[0017] in, For the generalized reactive power output of the grid-type converter with index i. This is a generalized reactive power coefficient, a predetermined value used to adjust the expected reactive power ratio of grid-type converters. For virtual impedance fixed terms, This is a virtual impedance variation term. It is a control parameter for the virtual impedance variation term. It is the amplification parameter of the virtual impedance variation term; yes Any monotonically non-decreasing function, and when , ;

[0018] When the circuit is inductive, take ,but , The virtual impedance expression degenerates into a virtual inductance:

[0019] ;

[0020] in, For virtual inductance, For virtual inductance fixed terms, This refers to the reactive power output of the grid-type converter with index i. This is a virtual inductance variation term. yes Any monotonically non-decreasing function and when , ; i is the variable index.

[0021] As a preferred embodiment of the virtual impedance adjustment and parameter optimization method for a grid-type converter described in this invention, the decomposition into fixed and variable terms includes determining the maximum virtual impedance value of the grid-type converter under the maximum generalized reactive load condition, calculating the maximum values ​​of the virtual impedance fixed and variable terms through the maximum virtual impedance value, and forming the basic parameters of the virtual impedance.

[0022] For the virtual impedance of the network converter with index i Determine the maximum generalized reactive load. maximum virtual impedance under certain conditions Based on this, the basic parameters of the virtual impedance are determined, namely the virtual impedance fixed terms. and the maximum value of the variable item :

[0023] Based on all grid-type converters, denoted as N, the sum of the maximum generalized reactive loads is: ;

[0024] The maximum generalized reactive load of a single grid-type converter is calculated according to the following principles: For any grid-type converter with indices i and j, i and j are positive integers; the maximum generalized reactive load is recorded as follows. and The maximum generalized reactive load of a single grid-connected converter satisfies the following two equations:

[0025] ;

[0026] ;

[0027] The voltage quality is selected based on the requirement of meeting the maximum generalized reactive load condition, that is:

[0028] ;

[0029] in, It is the effective value of the internal potential of the grid-type converter, and the value is the same for all grid-type converters. In the interval choose, and These are the lower and upper voltage limits specified in the standard.

[0030] Further selection of virtual impedance basic parameters: Virtual impedance fixed term and the maximum value of the virtual impedance variation term , For fixed term coefficients, 0 < <1, For all grid-type converters operating in parallel, selecting the same value results in... , ;

[0031] When the circuit is inductive, take ,but , Then the formula can be degenerated into:

[0032] ;

[0033] ;

[0034] ;

[0035] Further selection of virtual inductor basic parameters: Virtual inductor fixed items and the maximum value of the virtual inductance variation term ,0< <1, Choose the same value for all grid-type converters operating in parallel.

[0036] As a preferred embodiment of the virtual impedance adjustment and parameter optimization tuning method for a grid-type converter described in this invention, the step of obtaining the optimal value of the advanced parameters of the virtual impedance includes optimizing the calculation of the advanced parameters of the virtual impedance, i.e., the virtual impedance variation term control parameters. and virtual impedance variation amplification parameters ;

[0037] The equations satisfied by the generalized reactive load and virtual impedance in steady state are:

[0038] ;

[0039] in, This represents the effective value of the internal electromotive force of the grid-connected converter. This refers to the effective value of the bus voltage connected to the grid-type converter. Line impedance;

[0040] When the circuit is inductive, take , in the expression Replace with , Replace with That's all, among which It is the electrical quantity angular frequency.

[0041] As a preferred embodiment of the virtual impedance adjustment and parameter optimization method for a grid-type converter described in this invention, the method for obtaining the optimal parameters of the virtual impedance includes taking into account the generalized reactive power sharing error caused by line impedance mismatch. The amount by which the line impedance deviates from the ideal value This leads to the discovery using implicit function theory. for The ratio of generalized reactive power For line impedance Partial derivative:

[0042] ;

[0043] in, It is a function For variables The first-order partial derivative of the virtual impedance parameter and Optimization tuning is regarded as minimizing partial derivatives Absolute value, i.e., maximizing the denominator:

[0044] ;

[0045] ;

[0046] Will use as well as This means, that is:

[0047] ;

[0048] Generalized minimum reactive load Using the minimum generalized reactive load factor and maximum generalized reactive load Indicates, that is Substitute The denominator of the expression is improved to obtain:

[0049]

[0050] The parameters that maximize the denominator will be calculated. As the optimal parameter;

[0051] When the circuit is inductive, take , in the expression Replace with , Replace with .

[0052] As a preferred embodiment of the virtual impedance adjustment and parameter optimization tuning method for a grid-type converter described in this invention, the control of the grid-type converter includes:

[0053] The obtained variable control parameters Substitution To be used as a variable to amplify parameters The optimal parameter values ​​should be determined for all grid-type converters. The calculation results are exactly the same, so we only need to calculate one of the grid-type converters. That's all;

[0054] Obtain the optimal value of the virtual impedance advanced parameter , Combined with virtual impedance fixed terms Grid-type converter generalized reactive power Substituting into the expression for virtual impedance yields the real-time virtual impedance magnitude. ;

[0055] The virtual resistance is obtained by using a preset virtual impedance angle and the obtained real-time virtual impedance magnitude. and virtual inductance :

[0056]

[0057]

[0058] The grid-type converter is controlled based on the virtual resistance and virtual inductance.

[0059] Another objective of this invention is to provide a virtual impedance regulation and parameter optimization tuning system for a grid-type converter.

[0060] To solve the above technical problems, the present invention provides the following technical solution: a virtual impedance adjustment and parameter optimization tuning system for a grid-type converter, comprising: a virtual impedance construction module, a virtual impedance basic parameter determination module, and a virtual impedance advanced parameter determination module;

[0061] The virtual impedance construction module optimizes the selection of the generalized power coordinate transformation angle based on the unit length resistance and reactance ratio information of the grid-type converter's access line, reduces the coupling between generalized active power and generalized reactive power, and decomposes the virtual impedance of the grid-type converter into fixed terms and variable terms. The variable terms are arbitrary monotonically non-decreasing functions of generalized reactive power, and the variable terms are also positive when the generalized reactive power is positive.

[0062] The virtual impedance basic parameter determination module determines the virtual impedance basic parameters, namely the maximum values ​​of the virtual impedance fixed term and the virtual impedance variable term, according to the requirement that the output voltage quality of the grid-type converter meets the requirements when the generalized reactive load is at its maximum.

[0063] The virtual impedance advanced parameter determination module obtains the partial derivative of the reactive power sharing value with respect to the line impedance parameter through implicit function theory. It obtains the optimal parameters of the virtual impedance according to the principle of minimizing the absolute value of the partial derivative. Based on the optimal parameters of the virtual impedance, it obtains the real-time virtual impedance magnitude. It uses the preset virtual impedance angle combined with the real-time virtual impedance magnitude to obtain the virtual resistance and virtual inductance, and controls the grid-type converter.

[0064] The present invention provides a computer device, including a memory and a processor, wherein the memory stores a computer program, characterized in that the processor executes the computer program to implement the steps of the aforementioned method for virtual impedance regulation and parameter optimization tuning of a grid-type converter.

[0065] The present invention provides a computer-readable storage medium having a computer program stored thereon, characterized in that, when the computer program is executed by a processor, it implements the steps of the aforementioned method for virtual impedance regulation and parameter optimization tuning of a grid-type converter.

[0066] The beneficial effects of this invention: This invention proposes using a non-decreasing function of generalized reactive power. There are infinitely many functions that can adjust the virtual impedance to satisfy the above conditions, which greatly increases the flexibility of virtual impedance adjustment.

[0067] A quantitative relationship between the generalized reactive power sharing error and the virtual impedance parameter of a grid-type converter was established using implicit function theory. Based on this, a method for tuning the optimal control parameter of the virtual impedance was proposed. For operating conditions with a specific generalized reactive power load rate, this method can significantly reduce the generalized reactive power sharing error, thereby greatly reducing the apparent power sharing error. For operating conditions where the generalized reactive power load rate fluctuates within a large range, this method can significantly reduce the generalized reactive power sharing error at the minimum generalized reactive power load rate. Attached Figure Description

[0068] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0069] Figure 1 The above is a flowchart of a method for virtual impedance adjustment and parameter optimization tuning of a grid-type converter, provided as an embodiment of the present invention.

[0070] Figure 2 A schematic diagram of a grid-connected grid converter (after introducing virtual inductance) is provided for a method of virtual impedance adjustment and parameter optimization of a grid-connected converter according to an embodiment of the present invention.

[0071] Figure 3 This invention provides a method for virtual impedance regulation and parameter optimization tuning of a grid converter, which involves two grid converters operating in parallel.

[0072] Figure 4 This invention provides a method for virtual impedance regulation and parameter optimization tuning of a grid-type converter, which is used for parallel operation of grid-type converters.

[0073] Figure 5 The reactive power sharing result of virtual impedance parameter adjustment by virtual reactance-power droop is provided in an embodiment of the present invention.

[0074] Figure 6 The improved virtual inductance-power droop adjustment of the reactive power sharing result is provided by one embodiment of the present invention.

[0075] Figure 7 This is a reactive power sharing result provided by an embodiment of the present invention, which uses a constant virtual inductance as a virtual impedance.

[0076] Figure 8 The reactive power sharing result of the present invention, which provides a method for virtual impedance regulation and parameter optimization tuning of a grid-type converter according to an embodiment of the present invention. Using power functions . Detailed Implementation

[0077] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the protection scope of the present invention.

[0078] Example 1, referring to Figures 1-3 This is one embodiment of the present invention, which provides a method for virtual impedance adjustment and parameter optimization tuning of a grid-type converter, including:

[0079] Based on the unit length resistance and reactance ratio information of the grid-type converter connected line, the generalized power coordinate transformation angle is optimized to reduce the coupling between generalized active power and generalized reactive power.

[0080] The virtual impedance of the grid-type converter is decomposed into fixed terms and variable terms. The variable terms are arbitrary monotonically non-decreasing functions of the generalized reactive power, and the variable terms are also positive when the generalized reactive power is positive.

[0081] The maximum virtual impedance value is selected based on the requirement that the voltage quality meets the maximum generalized reactive load. The maximum virtual impedance value is used to calculate the maximum values ​​of the virtual impedance fixed terms and variable terms, which constitute the basic parameters of the virtual impedance.

[0082] The partial derivative of the reactive power sharing value with respect to the line impedance parameter is obtained by implicit function theory, and the optimal value of the advanced parameter of virtual impedance is obtained according to the principle of minimizing the partial derivative.

[0083] The real-time virtual impedance magnitude is obtained based on the basic parameters, advanced parameters, and generalized reactive power of the virtual impedance. The virtual resistance and virtual inductance are obtained by combining the preset virtual impedance angle with the real-time virtual impedance magnitude, and the grid-type converter is controlled.

[0084] Example 2, refer to Figures 1-3 As an embodiment of the present invention, based on the previous embodiment, a method for virtual impedance adjustment and parameter optimization tuning of a grid-type converter is provided, including:

[0085] This invention is based on a multi-machine parallel grid-connected converter. For the grid-connected converter using this invention, the specific control algorithm implementation process is as follows:

[0086] Step 1: By appropriately selecting the transformation angle of the generalized power coordinates (Determined by the resistance and reactance ratio per unit length of the line) Reduce the coupling between generalized active power and generalized reactive power;

[0087] Based on the resistance per unit length of the line and reactance per unit length ratio When multiple lines When the ratios are not equal, follow the decreasing order. and Control coupling selection between Take all lines The average of the ratios or taking Median value of the ratio. Active power for grid-type converters. and no merit Perform a power coordinate transformation to obtain the generalized active power. and generalized no merit The power coordinate transformation is as follows:

[0088]

[0089]

[0090] Step 2: Adjust the virtual impedance using generalized reactive power. For the virtual impedance of the grid-type converter with index i... for:

[0091]

[0092] in, For the generalized reactive power output of the grid-type converter with index i. This is a generalized reactive power coefficient, a predetermined value used to adjust the expected reactive power ratio of grid-type converters. For virtual impedance fixed terms, This is a virtual impedance variation term. It is a control parameter for the virtual impedance variation term. It is the amplification parameter of the virtual impedance variation term; yes Any monotonically non-decreasing function, and when , ;

[0093] When the circuit is inductive, take ,but , The virtual impedance expression degenerates into a virtual inductance:

[0094]

[0095] in, For virtual inductance, For virtual inductance fixed terms, This refers to the reactive power output of the grid-type converter with index i. This is a virtual inductance variation term. yes Any monotonically non-decreasing function and when , ; i is the variable index.

[0096] Step 3: Determine the maximum virtual impedance of the grid-type converter under the maximum generalized reactive load condition, and calculate the maximum values ​​of the virtual impedance fixed terms and variable terms through the maximum virtual impedance to form the basic parameters of virtual impedance;

[0097] For the virtual impedance of the network converter with index i Determine the maximum generalized reactive load. maximum virtual impedance under certain conditions Based on this, the basic parameters of the virtual impedance are determined, namely the virtual impedance fixed terms. The value of the variable term when the maximum generalized reactive load is reached. :

[0098] Based on all grid-type converters, the number is denoted as N, and the maximum generalized reactive load is... The maximum generalized reactive load of a single grid-type converter is calculated according to the following principles: For any grid-type converter with indices i and j, i and j are positive integers; the maximum generalized reactive load is recorded as follows. and The maximum generalized reactive load of a single grid-connected converter satisfies the following two equations:

[0099]

[0100]

[0101] The voltage quality is selected based on the requirement of meeting the maximum generalized reactive load condition, that is:

[0102]

[0103] in, It is the effective value of the internal potential of the grid-type converter, and the value is the same for all grid-type converters. and These are the lower and upper voltage limits specified in the standard, which can be a national standard or a power industry standard. In the interval choose;

[0104] Further selection of virtual impedance basic parameters: Virtual impedance fixed term and the maximum value of the virtual impedance variation term , For fixed term coefficients, 0 < <1, For all grid-type converters operating in parallel, selecting the same value results in... , ;

[0105] When the circuit is inductive, take ,but , Then the formula can be degenerated into:

[0106]

[0107]

[0108]

[0109] Further selection of virtual inductor basic parameters: Virtual inductor fixed items and the maximum value of the virtual inductance variation term ,0< <1, Choose the same value for all grid-type converters operating in parallel.

[0110] Step 4: Optimize the calculation of the virtual impedance advanced parameters, i.e., the virtual impedance variation term control parameters. and virtual impedance variation amplification parameters ;

[0111] The equations satisfied by the generalized reactive load and virtual impedance in steady state are:

[0112]

[0113] in, This represents the effective value of the internal electromotive force of the grid-connected converter. This refers to the effective value of the bus voltage connected to the grid-type converter. Line impedance;

[0114] When the circuit is inductive, take , in the expression Replace with , Replace with That's all, among which It is the electrical quantity angular frequency.

[0115] Step 5: Calculate the generalized reactive power sharing error caused by line impedance mismatch. The amount by which the line impedance deviates from the ideal value This leads to the discovery using implicit function theory. for The ratio of generalized reactive power For line impedance Partial derivative:

[0116]

[0117] in, It is a function For variables The first-order partial derivative.

[0118] Step 6: Set the virtual impedance parameters and Optimization tuning is regarded as minimizing partial derivatives Absolute value, i.e., maximizing the denominator:

[0119]

[0120]

[0121] Will use as well as This means, that is:

[0122]

[0123] Generalized minimum reactive load Using the minimum generalized reactive load factor and maximum generalized reactive load Indicates, that is Substitute The denominator of the expression is improved to obtain:

[0124] .

[0125] Step 7: Calculate the parameters that maximize the denominator. As the optimal parameter;

[0126] Step 8: Transfer the variable control parameters obtained in Step 8 Substitution To be used as a variable to amplify parameters The optimal parameter values.

[0127] Step 9: Obtain the optimal values ​​of the virtual impedance advanced parameters , Combined with virtual impedance fixed terms Grid-type converter generalized reactive power Substituting into the expression for virtual impedance yields the real-time virtual impedance magnitude. .

[0128] Step 10: Obtain the virtual resistance using the preset virtual impedance angle and the obtained real-time virtual impedance magnitude. and virtual inductance (When the line is inductive, take) The expressions in steps 6 and 9 Replace with , Replace with ):

[0129]

[0130]

[0131] The grid-type converter is controlled based on the virtual resistance and virtual inductance.

[0132] In summary, this invention employs a non-decreasing function of generalized reactive power to adjust virtual impedance. The generalized reactive power sharing error caused by line impedance mismatch is equated to a change in the solution of the nonlinear equation system due to the deviation of line impedance parameters from the ideal value. The partial derivative of the generalized reactive power sharing error with respect to line impedance is obtained through implicit function theory. The virtual impedance control parameter in the expression of the partial derivative of the reactive power sharing error with respect to line impedance is treated as the independent variable. Reducing the generalized reactive power sharing error is equivalent to finding the minimum absolute value of the partial derivative of the reactive power sharing error with respect to line impedance, thereby obtaining the optimal value of the virtual impedance parameter. Commonly used types of non-decreasing functions for generalized reactive power include arctangent functions, power functions, and exponential functions.

[0133] Example 3, referring to Figures 4-8 This invention provides a method for virtual impedance adjustment and parameter optimization tuning of a grid-type converter. To verify the beneficial effects of this invention, scientific demonstration is carried out through experiments.

[0134] To verify the effectiveness of this invention, simulations were performed. It is emphasized again that this invention addresses the power sharing problem in grid-connected converters without communication; the conventional method used in comparison is also a non-communication control method. The system employed is as follows: Figure 4 As shown, it includes two three-phase, three-wire grid converters with a rated line voltage of 380V (phase voltage of 220V) and a rated frequency of 50Hz. They are connected to each other via an RL (resistor-inductor series) line. Since there are two grid converters, in this embodiment, for variables with the subscript "i", the value of "i" is 1 or 2.

[0135] (1) Inductive circuit - specific load rate

[0136] In this embodiment, it is expected that grid-type converter 1 and grid-type converter 2 will share reactive power in a 2:1 ratio. The control objective is to reduce the reactive power sharing error at a specific load rate level of 14700Var reactive power. Ideally, the reactive power load shared by grid-type converter 1 and grid-type converter 2 should be 9800Var and 4900Var, respectively. To make the calculation more accurate, reactive power losses on the line are considered, and estimated at a reactive power loss rate of 2%. The maximum reactive power load of grid-type converter 1 and grid-type converter 2 is then calculated. and Estimated as and It is used in the calculation process of optimizing virtual impedance control parameters.

[0137] In this simulation, active power is controlled by Pf droop control, while reactive power is controlled by the present invention through a virtual inductor.

[0138] Line impedance parameters are , , , At this point, the reactance per unit length of the line is much greater than the resistance, therefore it is an inductive line environment; the load parameters are: , .

[0139] This simulation applies the existing method's virtual reactance-power droop formula (for a grid-type converter with index i, the virtual reactance is...). ), Improved virtual inductance-power droop formula (for a grid-type converter with index i, the virtual reactance is Simulations were performed using the constant virtual inductance formula and the present invention, wherein the monotonic non-decreasing function of the present invention is a power function, i.e. .

[0140] In both the conventional method and the method of this invention, the effective values ​​of the internal potential and voltage of the two grid-type converters are set to... To compensate for the voltage drop on the virtual inductor and ensure the load-side voltage is 220V.

[0141] Following the implementation process in Example 2, the following can be obtained: The optimal value equals the maximum value. of Because this scenario involves a specific reactive load rate, therefore , The larger the reactive power sharing error, the smaller the error. The optimal value is At this point, the reactive power sharing error is 0.

[0142] Select For example, the maximum virtual inductance values ​​for grid-type converter 1 and grid-type converter 2 are respectively =2.75mH, =5.50mH, fixed term coefficient The fixed values ​​are respectively , At this point, the maximum value of the virtual reactance variation term is reached. mH, mH can be calculated according to the method of the present invention. Under maximum reactive load, the phase voltage at the load end is .

[0143] For a fair comparison, the virtual inductance fixed term remains the same for both the traditional virtual reactance-power droop formula and the improved virtual inductance-power droop formula. Its control parameters are based on the phase voltage at the load end. It is confirmed that, for the traditional constant virtual inductance formula, the constant reactance is also based on the load-side phase voltage. The method is determined. The reactive load sharing results are as follows: Figure 5 , Figure 6 , Figure 7 and Figure 8 And as shown in Table 1.

[0144] exist Figures 5-8 In order to facilitate comparison of whether the reactive power sharing result has achieved the expected 2:1, the reactive power of grid-type converter 2 is multiplied by 2, while the reactive power of grid-type converter 1 remains unchanged. This is reflected on the vertical axis as follows: (i=1,2). If the reactive power sharing error is zero, then the two lines coincide.

[0145] Depend on Figures 5-7 It can be seen that in the traditional method, the two curves differ significantly; while Figure 8 The results show that the two curves are extremely close after using the method of this invention, and the reactive power sharing accuracy is significantly higher than that of the traditional method. Table 1 shows that the reactive power sharing error using the traditional virtual inductance-reactive power droop formula and the improved formula based on it is close to 25%. Although the reactive power sharing error of the improved formula is smaller than that of the traditional virtual inductance-reactive power droop formula, its improvement in reactive power sharing accuracy is extremely limited. Although the reactive power sharing error of the traditional constant virtual inductance formula is significantly reduced, it still exceeds 10%. In contrast, the reactive power sharing error of this invention is only 2.71%, significantly lower than that of the traditional method. Note that because the reactive power expected value base of the grid-type converters is different (reactive power expected value of grid-type converter 1: reactive power expected value of grid-type converter 2 = 2:1), the same amount of reactive power error results in different error percentages; the error percentage values ​​in Table 1 are calculated for grid-type converter 2, and the absolute value of the reactive power sharing error percentage of grid-type converter 1 is half of the value in Table 1. Note that in Table 1, due to reactive power losses, the sum of reactive power of the two grid-connected converters is slightly higher than 14700MVar.

[0146] Table 1 Comparison of reactive power sharing errors using different methods

[0147]

[0148] (2) Hybrid characteristic line - specific reactive load rate

[0149] Based on the preceding text, the nonlinear function in this invention When using a power function to adjust the virtual inductance, The optimal value is the expression When the maximum value is obtained, the corresponding Value, with Increased reactive power sharing reduces error. The optimal value is This embodiment will further verify the correctness of this conclusion. It is expected that grid-type converter 1 and grid-type converter 2 will share reactive power in a 2:1 ratio. The control objective is to reduce the reactive power sharing error (when the reactive power sharing error is 0, the reactive power sharing values ​​of grid-type converter 1 and grid-type converter 2 are 9800Var and 4900Var, respectively) under the maximum reactive power load level of 14700Var. To make the calculation more accurate, reactive power losses on the line are considered, and estimated at a reactive power loss rate of 2%. Therefore, the maximum reactive power load of grid-type converter 1 and grid-type converter 2 is... and Estimated as and It is used in the calculation process of optimizing virtual impedance control parameters.

[0150] The line parameters are R1=0.16Ω, L1=0.33mH, R2=0.2Ω, L2=0.4mH. The load is a specific value, and the load parameters are... , .

[0151] Virtual inductance fixed item is , Maximum value of virtual inductance variation term mH, mH. Table 2 shows the reactive power output and reactive power sharing errors of the grid-type converter when the values ​​are 8, 16, and 24. The error percentage values ​​are calculated for grid-type converter 2. As shown in Table 2, with... Increased reactive power sharing reduces the error. When the reactive power sharing error percentage is 16, it is approximately = half of 8, =24 hours, the reactive power sharing error percentage is approximately =One-third of the time, which almost perfectly matches the theoretical derivation.

[0152] Table 2 shows the reactive power sharing error of the present invention using different control parameters at specific reactive load rates.

[0153]

[0154] (3) Hybrid characteristic line - reactive load rate varies within a certain range

[0155] This embodiment aims to have grid-type converter 1 and grid-type converter 2 share reactive power in a 2:1 ratio. The control objective is to reduce the reactive power sharing error at the maximum reactive load rate (100% reactive load rate) of 14700 Var and minimize the reactive power sharing error at the minimum reactive load rate (50% reactive load rate) of 7350 Var. The line parameters are R1=0.16Ω, L1=0.33mH, R2=0.2Ω, and L2=0.4mH. Note that the 100% reactive load rate in this invention refers to a percentage relative to the maximum reactive power, not a percentage relative to the rated reactive power. Therefore, a 50% reactive load rate means that the reactive load is only half of the maximum reactive load, and other percentages follow the same logic. To make the calculation more accurate, reactive power losses on the line are considered, estimated at a 2% reactive power loss rate. The maximum reactive load of grid-type converter 1 and grid-type converter 2 is then... and Estimated as and It is used in the calculation process of optimizing virtual impedance control parameters.

[0156] The load parameters are: under maximum reactive load (i.e., 100% reactive load rate). , At a 50% reactive load rate, , Because the control accuracy of the improved formula using the traditional virtual inductance-reactive power droop method is higher than that of the traditional virtual inductance-reactive power droop method, this section compares and simulates the improved formula, the traditional constant virtual inductance, and the method of this invention. Under 100% reactive load conditions, the effective values ​​of the internal potential and voltage of the two grid-type converters in both the traditional method and the method of this invention are set to... To compensate for the voltage drop on the virtual reactor and ensure the load-side voltage is 220V; when the reactive load rate is 50%, the virtual reactor control parameters remain unchanged, and the effective value of the internal potential is reduced to ensure the load-side phase voltage is 220V.

[0157] According to the implementation process in Example 2, the monotonic non-decreasing function is a power function, that is... ,but The optimal value is ,in =0.5 is the minimum reactive load rate. The virtual inductance fixed terms for grid-type converter 1 and grid-type converter 2 are respectively... The maximum values ​​of the variable terms are respectively , According to the implementation process in Example 2, Under maximum reactive load, the phase voltage at the load end is 220V.

[0158] For a fair comparison, when using the traditional formula improved by virtual inductance-reactive droop, the virtual inductance fixed term is also chosen as... , Its virtual inductance adjustment coefficient Assuming a 100% reactive load rate, the load terminal phase voltage is... After tuning, the virtual inductance regulation coefficients of grid-connected converter 1 and grid-connected converter 2 are respectively... , When the reactive load rate is 50%, the virtual reactance control parameters remain unchanged, and the effective value of the internal potential is reduced to ensure a load-side phase voltage of 220V. When using a traditional constant virtual inductance, the same principle applies to ensure a load-side phase voltage of 100% reactive load rate. After selection, the virtual inductances of grid-connected converter 1 and grid-connected converter 2 are respectively... , When the reactive load rate is 50%, the virtual reactor control parameters remain unchanged, and the effective value of the internal potential is reduced to ensure that the phase voltage at the load end is 220V.

[0159] Simulation results are shown in Table 3. Note that the total reactive load of 14700Var is an ideal case. The reactive power in Table 3 also includes reactive power losses on the line. Therefore, the sum of reactive power from the two grid-type converters is greater than 14700Var, and the sum of reactive power varies slightly for different methods. As shown in the table, the reactive load sharing error of the improved virtual inductor-droop control is greatly affected by the reactive load rate. At a reactive load rate of 100%, the reactive load sharing error is 26.24%. When the reactive load rate decreases to 50%, the reactive load sharing error increases to 27.60%. The constant inductance method has a sharing error of 12.90% at a 100% reactive load rate, significantly greater than the 10.38% sharing error of this invention. At a 50% reactive load rate, the sharing error is 13.50%. Although its sharing error is significantly smaller than that of the traditional virtual inductor-droop control method, it is still greater than the result after parameter optimization of this method. =1.4427). In this invention, the reactive power sharing errors at reactive load rates of 100% and 50% are 10.38% and 13.25%, respectively, which is the smallest among all methods. Furthermore, to further verify this invention, Table 3 also provides the results of optimizing the control parameters using this invention but without considering variations in the reactive load rate, i.e., the parameter values ​​are tuned for a reactive load rate of 100%. As mentioned above, The bigger the better, but in this case, we take... The results show that when the reactive load rate is 100%, the reactive power sharing error is much smaller than that of other methods. However, when the reactive load rate drops to 50%, the reactive power sharing error rises sharply to 25.20%, which is much greater than the reactive power sharing error of 13.25% after parameter optimization considering the minimum reactive load rate of 50%.

[0160] Table 3 Reactive power sharing results when reactive power load rate varies between 50% and 100%.

[0161]

[0162] (4) Hybrid characteristic circuit - based on generalized active power and generalized reactive power

[0163] When the line exhibits mixed characteristics, the line impedance angle information can also be used to perform power coordinate transformation on active and reactive power to obtain generalized active and generalized reactive power. This part of the simulation verifies the control effect of the present invention under a specific generalized reactive load rate. The impedance parameters of lines 1 and 2 are the same as those in the previous simulation. Therefore, the reactance corresponding to line 1 is... The reactance corresponding to line 2 is , Therefore, the line impedance angle used for power coordinate transformation can be taken as the average of the two, 1.55. , .

[0164] Pick , , The parameter tuning and control of the generalized reactive load in Example 2 are performed, where the nonlinear function... Using a power function, following the steps of this invention The optimal value is Considering the feasibility of the project, this example takes... =8. The results are shown in Table 4, where S represents apparent power. Since only generalized active power can be achieved... The precise allocation of reactive power results in errors in both active and reactive power allocation. Table 4 provides both active and reactive power allocation results, with the allocation error expressed as apparent power. Table 4 shows that the apparent power allocation errors for grid-type converter 1 and grid-type converter 2 are -1.5% and 3%, respectively, achieving good results.

[0165] Table 4. Results of Active Power Sharing and Reactive Power Sharing

[0166]

[0167] The simulation of the generalized reactive load rate varying within a certain range is similar to that described above and will not be repeated here.

[0168] Example 4 is an embodiment of the present invention. This embodiment provides a virtual impedance adjustment and parameter optimization tuning system for a grid-type converter, including: a virtual impedance construction module, a virtual impedance basic parameter determination module, and a virtual impedance advanced parameter determination module;

[0169] The virtual impedance construction module optimizes the selection of the generalized power coordinate transformation angle based on the unit length resistance and reactance ratio information of the grid-type converter's access line, reduces the coupling between generalized active power and generalized reactive power, and decomposes the virtual impedance of the grid-type converter into fixed terms and variable terms.

[0170] The virtual impedance basic parameter determination module determines the virtual impedance basic parameters, namely the maximum values ​​of the virtual impedance fixed term and the virtual impedance variable term, according to the requirement that the output voltage quality of the grid-type converter meets the requirements when the generalized reactive load is at its maximum.

[0171] The virtual impedance advanced parameter determination module obtains the partial derivative of the reactive power sharing value with respect to the line impedance parameter through implicit function theory, obtains the optimal value of the virtual impedance advanced parameter according to the principle of minimizing the absolute value of the partial derivative, obtains the real-time virtual impedance magnitude based on the optimal virtual impedance parameter, and obtains the virtual resistance and virtual inductance by combining the preset virtual impedance angle with the real-time virtual impedance magnitude, and controls the grid-type converter.

[0172] This embodiment also provides an electronic device applicable to a method for virtual impedance adjustment and parameter optimization tuning of a grid-type converter, comprising: a memory and a processor; the memory is used to store computer-executable instructions, and the processor is used to execute the computer-executable instructions to implement the method for virtual impedance adjustment and parameter optimization tuning of a grid-type converter as proposed in the above embodiment.

[0173] This embodiment also provides a storage medium storing a computer program that, when executed by a processor, implements a method for virtual impedance regulation and parameter optimization tuning of a grid-type converter as proposed in the above embodiments.

[0174] The storage medium proposed in this embodiment belongs to the same inventive concept as the method for virtual impedance adjustment and parameter optimization of a grid-type converter proposed in the above embodiments. Technical details not described in detail in this embodiment can be found in the above embodiments, and this embodiment has the same beneficial effects as the above embodiments.

[0175] Based on the above description of the implementation methods, those skilled in the art can clearly understand that the present invention can be implemented using software and necessary general-purpose hardware, and of course, it can also be implemented using hardware, but in many cases the former is a better implementation method. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product can be stored in a computer-readable storage medium, such as a computer floppy disk, read-only memory (ROM), random access memory (RAM), flash memory, hard disk, or optical disk, etc., including several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute the methods of the various embodiments of the present invention.

[0176] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for virtual impedance regulation and parameter optimization tuning of a grid-type converter, characterized in that: include, Based on the unit length resistance and reactance ratio information of the grid-type converter connected line, the generalized power coordinate transformation angle is optimized to reduce the coupling between generalized active power and generalized reactive power. The virtual impedance of the grid-type converter is decomposed into fixed terms and variable terms. The variable terms are arbitrary monotonically non-decreasing functions of the generalized reactive power, and the variable terms are also positive when the generalized reactive power is positive. The maximum virtual impedance value is selected based on the requirement that the voltage quality meets the maximum generalized reactive load. The maximum virtual impedance value is used to calculate the maximum values ​​of the virtual impedance fixed terms and variable terms, which constitute the basic parameters of the virtual impedance. By obtaining the partial derivative of the generalized reactive power sharing value with respect to the line impedance parameter through implicit function theory, the optimal value of the advanced parameter of virtual impedance can be obtained. The real-time virtual impedance magnitude is obtained based on the basic parameters, advanced parameters and generalized reactive power of virtual impedance. Virtual resistance and virtual inductance are obtained by combining the preset virtual impedance angle with the real-time virtual impedance magnitude, and the grid-type converter is controlled. The optimized selection of the generalized power coordinate transformation angle includes, by reasonably selecting the generalized power coordinate transformation angle. Reduce the coupling between generalized active power and generalized reactive power, i.e., when multiple circuits... When the ratios are not equal, follow the decreasing order. and Control coupling selection between Take all lines The average of the ratios or taking Median value of the ratio; Active power of grid converter and no merit Perform a power coordinate transformation to obtain the generalized active power. and generalized no merit The power coordinate transformation is as follows: The virtual impedance includes the virtual impedance adjusted by generalized reactive power, for the virtual impedance of the grid-type converter numbered i. for: in, Let i be the generalized reactive power output of the grid-type converter. This is a generalized reactive power coefficient, a predetermined value used to adjust the expected reactive power ratio of grid-type converters. For virtual impedance fixed terms, This is a virtual impedance variation term. It is a control parameter for the virtual impedance variation term. It is the amplification parameter of the virtual impedance variation term; yes Any monotonically non-decreasing function, and when , ; When the circuit is inductive, take ,but , The virtual impedance expression degenerates into a virtual inductance: in, For virtual inductance, For virtual inductance fixed terms, This refers to the reactive power output of the grid-type converter numbered i. This is a virtual inductance variation term. yes Any monotonically non-decreasing function and when , ; i is the variable index.

2. The method for virtual impedance adjustment and parameter optimization tuning of a grid-type converter as described in claim 1, characterized in that: The decomposition is divided into fixed terms and variable terms. The maximum virtual impedance of the grid-type converter under the maximum generalized reactive load is determined. The maximum values ​​of the fixed and variable virtual impedance terms are calculated through the maximum virtual impedance value to form the basic parameters of virtual impedance. For the virtual impedance of the network type numbered i Determine the maximum generalized reactive load. maximum virtual impedance under certain conditions Based on this, the basic parameters of the virtual impedance, i.e., the fixed terms, are determined. and the maximum value of the variable item : Based on all grid-type converters, denoted as N, the sum of the maximum generalized reactive loads is: The maximum generalized reactive load of a single grid-type converter is calculated according to the following principles: For any grid-type converter numbered i and j, where i and j are variable indices and are positive integers, the maximum generalized reactive load is recorded as follows: and The generalized reactive load of a single grid-connected converter satisfies the following two equations: The voltage quality is selected based on the requirement of meeting the maximum generalized reactive load condition, that is: in, It is the effective value of the internal potential of the grid-type converter, and the value is the same for all grid-type converters. and The standard specifies the lower and upper voltage limits. In the interval choose; Further selection of virtual impedance basic parameters: Virtual impedance fixed term and the maximum value of the virtual impedance variation term , For fixed term coefficients, 0 < <1, For all grid-type converters operating in parallel, selecting the same value results in... , ; When the circuit is inductive, take ,but , Then the formula can be degenerated into: Further selection of virtual inductor basic parameters: Virtual inductor fixed items and the maximum value of the virtual inductance variation term ,0< <1, Choose the same value for all grid-type converters operating in parallel.

3. The method for virtual impedance adjustment and parameter optimization tuning of a grid-type converter as described in claim 2, characterized in that: The process of obtaining the optimal value of the advanced parameters of the virtual impedance includes optimizing the calculation of the advanced parameters of the virtual impedance, namely the virtual impedance variation term control parameters. and virtual impedance variation amplification parameters ; The equations satisfied by the generalized reactive load and virtual impedance in steady state are: in, This represents the effective value of the internal electromotive force of the grid-connected converter. This refers to the effective value of the bus voltage connected to the grid-type converter. Line impedance; When the circuit is inductive, take , in the expression Replace with , Replace with That's all, among which It is the electrical quantity angular frequency.

4. The method for virtual impedance adjustment and parameter optimization tuning of a grid-type converter as described in claim 3, characterized in that: The process of obtaining the optimal value of the advanced parameters for virtual impedance includes taking into account the generalized reactive power sharing error caused by line impedance mismatch. The amount by which the line impedance deviates from the ideal value This leads to the discovery using implicit function theory. for The ratio, i.e., generalized reactive power For line impedance Partial derivative: in, It is a function For variables The first-order partial derivative of the virtual impedance parameter and Optimization tuning is regarded as minimizing partial derivatives Absolute value, i.e., maximizing the denominator: Will use as well as This means, that is: Generalized minimum reactive load Using the minimum generalized reactive load factor and maximum generalized reactive load It means, that is Substitute The denominator of the expression is improved to obtain: The parameters that maximize the denominator will be calculated. As the optimal parameter; When the circuit is inductive, take , in the expression Replace with , Replace with .

5. The method for virtual impedance adjustment and parameter optimization tuning of a grid-type converter as described in claim 4, characterized in that: The control of the grid-type converter includes... The obtained variable control parameters Substitution To be used as a variable to amplify parameters The optimal parameter values; Obtain the optimal value of the virtual impedance advanced parameter , Combined with virtual impedance fixed terms Grid-type converter generalized reactive power Substituting into the expression for virtual impedance yields the real-time virtual impedance magnitude. ; The virtual resistance is obtained by using a preset virtual impedance angle and the obtained real-time virtual impedance magnitude. and virtual inductance : The grid-type converter is controlled based on the virtual resistance and virtual reactance.

6. A virtual impedance adjustment and parameter optimization system for a grid-type converter, employing the virtual impedance adjustment and parameter optimization method for a grid-type converter as described in any one of claims 1 to 5, characterized in that, include: Virtual impedance construction module, virtual impedance basic parameter determination module, virtual impedance advanced parameter determination module; The virtual impedance construction module optimizes the selection of the generalized power coordinate transformation angle based on the unit length resistance and reactance ratio information of the grid-type converter's access line, reduces the coupling between generalized active power and generalized reactive power, and decomposes the virtual impedance of the grid-type converter into fixed terms and variable terms. The advanced term is an arbitrary monotonically non-decreasing function of generalized reactive power, and the variable term is also positive when the generalized reactive power is positive. The virtual impedance basic parameter determination module determines the virtual impedance basic parameters, namely the maximum values ​​of the virtual impedance fixed term and the virtual impedance variable term, according to the requirement that the output voltage quality of the grid-type converter meets the requirements when the generalized reactive load is at its maximum. The virtual impedance advanced parameter determination module obtains the partial derivative of the generalized reactive power sharing value with respect to the line impedance parameter through implicit function theory. It obtains the optimal value of the virtual impedance advanced parameter according to the principle of minimizing the absolute value of the partial derivative. Based on the basic parameters, the optimal value of the advanced parameter and the generalized reactive power, it obtains the real-time virtual impedance magnitude. It uses the preset virtual impedance angle combined with the real-time virtual impedance magnitude to obtain the virtual resistance and virtual inductance, and controls the grid-type converter.

7. A computer device comprising a memory and a processor, wherein the memory stores a computer program, characterized in that, When the processor executes the computer program, it implements the steps of the virtual impedance regulation and parameter optimization tuning method for a grid-type converter according to any one of claims 1 to 5.

8. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the steps of the virtual impedance regulation and parameter optimization tuning method for a grid-type converter as described in any one of claims 1 to 5.

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