A method and device for calculating parameters of a passive damping device of a modular multilevel converter

Abstract

The application discloses a kind of modular multilevel converter passive damping device parameter calculation method and device, wherein the method comprises: obtaining converter ac port impedance transfer function and filter transfer function, and then obtaining the constant positive damping criterion function of converter ac port containing passive damping device;According to criterion function, the capacitance parameter value and inductance parameter value in passive damping are selected by combining preset parameter given method;The value interval of resistance parameter in passive damping is obtained by parameter projection domain method, and the resistance parameter value is selected according to the minimum loss principle.Through the constant positive damping criterion function of converter ac port containing passive damping device, the impedance remodeling frequency range and parameter selection requirement of passive damping device are clear, and the parameters of passive damping device elements are selected by parameter projection domain method, the impedance of converter ac port containing passive damping device is remodeled as constant positive damping, and the volume, cost and loss of equipment are reduced.

Description

Technical Field

[0001] This invention relates to the field of flexible DC transmission technology, and in particular to a method and apparatus for calculating parameters of a passive damping device for a modular multilevel converter. Background Technology

[0002] In recent years, flexible DC transmission technology has been increasingly used in large-scale renewable energy transmission and asynchronous grid interconnection due to its advantages such as independent control of active and reactive power and the ability to supply power to passive networks. However, with the increasing penetration of renewable energy generation in the power grid and the widespread application of flexible DC transmission technology in various scenarios, high-frequency oscillation problems have emerged in actual transmission projects. These harmonic resonance problems cause overvoltage and overcurrent phenomena in the AC system, damaging the primary equipment of the converter station and leading to system shutdowns, seriously affecting the safety and stability of the system.

[0003] To suppress high-frequency harmonic resonance and improve converter operational stability, strategies such as control parameter optimization and the addition of active damping can be employed to reshape the converter's impedance phase angle characteristics in the resonant frequency band, ensuring they meet harmonic stability requirements. The advantages of these strategies are their ease of modification and lack of the need for additional equipment; however, the disadvantages include the difficulty in adjusting the converter's impedance phase angle to within ±90 degrees across the entire mid-to-high frequency range, the existence of multiple resonance risk points, transient steady-state characteristic balancing issues, and multi-operating-condition adaptation problems when the converter is connected to a complex AC power grid, and the challenges in parameter optimization and damping strategy selection.

[0004] Besides active damping strategies, passive damping strategies can also be employed, involving parallel connection of passive filters on the AC side of the converter. The advantage is that it does not require changes to the converter's control parameters and architecture, thus preserving the converter's original metastable-state characteristic design. The disadvantage is the need for additional primary equipment, resulting in a large footprint, high cost, and high losses. In applicable scenarios, passive filters are a crucial component of traditional DC transmission systems based on grid-commutated converters, serving to filter out characteristic harmonics of specific frequencies while also providing reactive power compensation. In contrast, the passive damping of modular multilevel converters reshapes the converter's impedance phase angle, rather than targeting characteristic harmonics, and does not require reactive power compensation. Therefore, during parameter design, the device size and cost can be optimized to a level far smaller than traditional filters. Summary of the Invention

[0005] The purpose of this invention is to provide a method and apparatus for calculating the parameters of a passive damping device in a modular multilevel converter. For broadband harmonic resonance suppression in the mid-to-high frequency band, the method clarifies the impedance reshaping frequency range and parameter selection requirements of the passive damping device through the constant positive damping criterion of the AC port of the converter containing the passive damping device. Furthermore, it provides an intuitive graphical method for selecting the parameters of the passive damping device components through the parameter projection domain method, making it easier to understand and operate. The constraints of minimizing capacitance and damping resistance loss in parameter selection provide a direction for selecting the parameters of the passive damping device components, reducing the size, cost, and losses of the equipment, and facilitating its engineering application and promotion.

[0006] To address the aforementioned technical problems, a first aspect of this invention provides a method for calculating the parameters of a passive damping device in a modular multilevel converter, comprising the following steps:

[0007] Obtain the AC port impedance transfer function and filter transfer function of the converter, and then obtain the constant positive damping criterion function of the AC port of the converter including the passive damping device;

[0008] Based on the criterion function, and combined with the preset parameter setting method, the capacitance and inductance parameter values ​​in the passive damping device are selected.

[0009] The range of resistance parameters in the passive damping device is obtained by the parametric projection domain method, and the resistance parameter values ​​are selected based on the principle of minimizing losses.

[0010] Furthermore, after selecting the resistance parameter value based on the principle of minimum loss, the method further includes:

[0011] The capacitance parameter value is reduced, and the resistance parameter value is updated according to the parameter projection domain method to obtain the parameter values ​​of the passive damping device that meet the cost and loss requirements.

[0012] Further, the step of obtaining the AC port impedance transfer function and filter transfer function of the converter, and then obtaining the constant positive damping criterion function of the AC port of the converter, includes:

[0013] The AC port impedance model of the converter is obtained by impedance modeling method, and then the real part of the converter impedance and the impedance amplitude as a function of frequency are obtained.

[0014] The passive damping topology is selected, and its transfer function is obtained.

[0015] Obtain the constant positive damping criterion function for the AC port of the converter, which includes the passive damping device.

[0016] Furthermore, obtaining the range of resistance values ​​in the passive damping device using the parametric projection domain method includes:

[0017] Calculate the AC port output impedance of the converter including the passive damping device;

[0018] Given any initial values ​​for the capacitance and inductance parameters in the passive damping device, the output impedance transfer function containing two variables, resistance and frequency, is obtained.

[0019] By selecting non-negative values ​​for the resistance parameter and frequency in the output impedance transfer function, a three-dimensional image of the criterion function is obtained, and the criterion function is projected onto the resistance-frequency plane after taking non-positive values.

[0020] In the resistance-frequency plane, when the frequency value takes any value of f∈(0,∞), the set of values ​​of the resistance parameter that do not fall within the projection area is the range of values ​​of the resistance parameter, thereby determining the value of the resistance parameter.

[0021] By changing the capacitor and inductor parameter values ​​and performing iterative calculations, the resistance parameter value is obtained, thereby obtaining the parameter values ​​of the passive damping device that meet the various requirements of the project.

[0022] Furthermore, the method for giving the preset parameters is as follows:

[0023] Considering the engineering cost and manufacturing difficulty, the minimum value of the capacitor parameter is taken as the primary constraint condition. The value of the capacitor parameter is determined first, and then the value of the inductor parameter is determined.

[0024] After obtaining the range of values ​​of the resistance parameter projected onto the resistance-frequency plane, the resistance parameter value is determined with minimum loss as the constraint.

[0025] Accordingly, a second aspect of the present invention provides a parameter calculation device for a modular multilevel converter passive damping device, comprising:

[0026] The acquisition module is used to acquire the AC port impedance transfer function and filter transfer function of the converter, and then obtain the constant positive damping criterion function of the AC port of the converter including the passive damping device.

[0027] The first selection module selects the capacitance and inductance parameter values ​​in the passive damping device based on the criterion function and a preset parameter setting method.

[0028] The second selection module is used to obtain the range of resistance parameters in the passive damping device through the parameter projection domain method, and select the resistance parameter value according to the principle of minimum loss.

[0029] Furthermore, the parameter calculation device for the modular multilevel converter passive damping device also includes:

[0030] An iterative module is used to reduce the capacitance parameter value and update the resistance parameter value according to the parameter projection domain method to obtain the parameter values ​​of the passive damping device that meet the cost and loss requirements.

[0031] Furthermore, the first acquisition module includes:

[0032] The first acquisition unit is used to obtain the AC port impedance model of the converter through an impedance modeling method, and then obtain the real part of the converter impedance and the function of impedance amplitude as a function of frequency.

[0033] The second acquisition unit is used to select the passive damping topology and then obtain its topology transfer function;

[0034] The third acquisition unit is used to acquire the constant positive damping criterion function of the AC port of the converter, which includes the passive damping device.

[0035] Furthermore, the second selection module includes:

[0036] A calculation unit for calculating the AC port output impedance of the converter containing the passive damping device;

[0037] The assignment unit is used to arbitrarily give the initial values ​​of the capacitance and inductance parameters in the passive damping device to obtain the output impedance transfer function containing the two variables of resistance and frequency.

[0038] An image generation unit is used to select non-negative values ​​for the resistance parameter and frequency values ​​in the output impedance transfer function to obtain a three-dimensional image of the criterion function, and to project the criterion function onto the resistance-frequency plane after taking non-positive values.

[0039] A resistor selection unit is used to determine the value of the resistor parameter in the resistance-frequency plane such that, when the frequency value takes any value f∈(0,∞), the set of values ​​of the resistor parameter that do not fall within the projection area is the value range of the resistor parameter.

[0040] The iterative unit changes the capacitor parameter value and the inductor parameter value, and performs iterative calculations to obtain the resistance parameter value, thereby obtaining the passive damping device parameter value that meets various requirements in the project.

[0041] Furthermore, the method for giving the preset parameters is as follows:

[0042] Considering the engineering cost and manufacturing difficulty, the minimum value of the capacitor parameter is taken as the primary constraint condition. The value of the capacitor parameter is determined first, and then the value of the inductor parameter is determined.

[0043] After obtaining the range of values ​​of the resistance parameter projected onto the resistance-frequency plane, the resistance parameter value is determined with minimum loss as the constraint.

[0044] Accordingly, a third aspect of the present invention also provides an electronic device, comprising: at least one processor; and a memory connected to the at least one processor; wherein the memory stores instructions executable by the processor, the instructions being executed by the processor to cause the at least one processor to perform the above-described method for calculating the parameters of passive damping of a modular multilevel converter.

[0045] Furthermore, a fourth aspect of the present invention provides a computer-readable storage medium storing computer instructions that, when executed by a processor, implement the above-described method for calculating the parameters of a passive damping device for a modular multilevel converter.

[0046] The above-described technical solutions of the embodiments of the present invention have the following beneficial technical effects:

[0047] To address broadband harmonic resonance suppression in the mid-to-high frequency band, the constant positive damping criterion for the AC port of a converter with a passive damping device clarifies the impedance reshaping frequency range and parameter selection requirements for passive damping. Furthermore, the parameter projection domain method provides an intuitive graphical approach for selecting the parameters of the passive damping device components, making it easier to understand and operate. The constraints of minimizing capacitance and damping resistance loss in parameter selection provide a direction for selecting the parameters of the passive damping device components, reducing the size, cost, and losses of the equipment, and facilitating its engineering application and promotion. Attached Figure Description

[0048] Figure 1 This is a schematic diagram of a converter with a passive damping device connected to an AC power grid, provided in an embodiment of the present invention.

[0049] Figure 2 This is a schematic diagram of the main circuit and sub-module topology of the flexible DC converter provided in an embodiment of the present invention;

[0050] Figure 3 This is a flowchart of the parameter calculation method for the passive damping device of the modular multilevel converter provided in this embodiment of the invention;

[0051] Figure 4 This is a schematic diagram of the parameter calculation method for the passive damping device of the modular multilevel converter provided in this embodiment of the invention;

[0052] Figure 5 This is a schematic diagram of the passive damping filter topology provided in an embodiment of the present invention;

[0053] Figure 6 This is a schematic diagram showing the parameter value range of the resistor in the passive damping filter provided in this embodiment of the invention;

[0054] Figure 7 This is a block diagram of the modular multilevel converter passive damping device parameter calculation device module provided in the embodiment of the present invention;

[0055] Figure 8 This is a schematic diagram of the acquisition module provided in an embodiment of the present invention;

[0056] Figure 9 This is a schematic diagram of the second selection module provided in an embodiment of the present invention.

[0057] Figure label:

[0058] 1. Acquisition Module; 11. First Acquisition Unit; 12. Second Acquisition Unit; 13. Third Acquisition Unit; 2. First Selection Module; 3. Second Selection Module; 31. Calculation Unit; 32. Assignment Unit; 33. Image Generation Unit; 34. Resistance Selection Unit; 35. Iteration Unit; 4. Iteration Module. Detailed Implementation

[0059] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments and the accompanying drawings. It should be understood that these descriptions are merely exemplary and not intended to limit the scope of the invention. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concept of the invention.

[0060] Figure 1 This is a schematic diagram of a converter with a passive damping device connected to an AC power grid, provided in an embodiment of the present invention.

[0061] Figure 2 This is a schematic diagram of the main circuit and sub-module topology of the flexible DC converter provided in an embodiment of the present invention.

[0062] Figure 3 This is a flowchart of the parameter calculation method for the passive damping device of the modular multilevel converter provided in the embodiment of the present invention.

[0063] Figure 4 This is a schematic diagram of the parameter calculation method for the passive damping device of the modular multilevel converter provided in this embodiment of the invention;

[0064] Please refer to Figure 1 , Figure 2 , Figure 3 and Figure 4 The first aspect of this invention provides a method for calculating the parameters of a passive damping device for a modular multilevel converter, comprising the following steps:

[0065] S100, obtain the AC port impedance transfer function and filter transfer function of the converter, and then obtain the constant positive damping criterion function of the AC port of the converter including the passive damping device.

[0066] S200 selects the capacitance and inductance parameters in the passive damping device based on the criterion function and the preset parameter setting method.

[0067] S300 obtains the range of resistance parameters in the passive damping device through the parametric projection domain method, and selects the resistance parameter values ​​based on the principle of minimizing losses.

[0068] The above method targets broadband harmonic resonance suppression in the mid-to-high frequency band. It clarifies the impedance reshaping frequency range and parameter selection requirements of passive damping by using the constant positive damping criterion of the AC port of the converter with passive damping device. Furthermore, it provides an intuitive graphical method for selecting the component parameters of the passive damping device through the parameter projection domain method.

[0069] like Figure 1 As shown, a converter including a passive damping device is connected to the AC power grid. The converter valve and the connecting transformer form the converter. After the passive damping device is connected in parallel to the transformer grid side of the converter, it is connected to the AC power grid. The AC impedance of the converter is the input impedance seen from the transformer grid side. The AC port impedance of the converter containing the passive damping device is the input impedance seen from the parallel connection point of the passive damping device towards the converter.

[0070] like Figure 2 As shown, in the main circuit and sub-module topology of the modular multilevel converter, the converter valve consists of six bridge arms, each of which is composed of multiple cascaded sub-modules. The sub-modules within each bridge arm can be of various types, such as half-bridge or full-bridge sub-modules. Each bridge arm can contain only one type of sub-module or a mixture of multiple types. The AC impedance of the converter is typically established using small-signal analysis in the frequency domain. Once the AC impedance of the converter is determined, the AC port constant positive damping design criterion proposed in this invention can be applied. Therefore, this invention is applicable to all types of sub-module topologies and all types of converters constructed from their combinations.

[0071] This invention proposes a design criterion for constant positive damping of the AC port of a converter with a passive damping device: In the mid-to-high frequency band, if the sum of the ratio of the real part of the converter impedance to the square of the impedance magnitude and the ratio of the real part of the passive damping device impedance to the square of the impedance magnitude is greater than zero in the negative damping frequency band of the converter, then the AC port of the converter with the passive damping device is always positively damped in the entire mid-to-high frequency band.

[0072] Furthermore, in step S300, after selecting the resistance parameter value based on the principle of minimum loss, the following steps are also included:

[0073] S400, reduce the capacitor parameter value, and update the resistor parameter value according to the parameter projection domain method to obtain the parameter value of the passive damping device that meets the cost and loss requirements.

[0074] Further, in step S100, the impedance transfer function of the converter AC port and the filter transfer function are obtained, thereby obtaining the constant positive damping criterion function of the converter AC port, including:

[0075] S110, by using the impedance modeling method, the AC port impedance model of the converter is obtained, and then the real part of the converter impedance and the impedance amplitude as a function of frequency are obtained.

[0076] S120, select a passive damping topology, and then obtain its transfer function.

[0077] S130, obtain the constant positive damping criterion function for the AC port of the converter containing the passive damping device.

[0078] Figure 5 This is a schematic diagram of the passive damping filter topology provided in an embodiment of the present invention.

[0079] Figure 6 This is a schematic diagram showing the parameter range of the resistor in the passive damping filter provided in this embodiment of the invention.

[0080] like Figure 5 As shown in the diagram, in the passive filter topology of the grid-commutated converter, to eliminate the output harmonics of the grid-commutated converter, as shown in part (a), the earliest application was a single-tuned filter with a damping resistor in series to suppress the resonance risk between the filter and the AC system; as shown in part (b), to reduce the loss of the damping resistor, a second-order high-pass filter was proposed; as shown in part (c), to further reduce the loss of the damping resistor, a third-order high-pass filter was subsequently proposed; as shown in part (d), the parameter selection and impedance-frequency characteristics of the third-order filter were not satisfactory, so a C-type filter was proposed in the Anglo-French submarine DC project to solve the loss problem when filtering low-order harmonics. In engineering applications, one or a combination of filters is usually used depending on the harmonic suppression requirements. Because the cutoff frequency of the passive damping filter can be selected to be relatively high and the power frequency current flowing through the damping resistor is relatively small, the passive damping can use a simpler topology, such as a single-tuned filter or a second-order high-pass filter.

[0081] Further, please refer to Figure 5 and Figure 6 In step S300, the range of values ​​for the resistance in the passive damper is obtained using the parametric projection domain method, specifically including the following steps:

[0082] S310, calculate the AC port output impedance of the converter including the passive damping device.

[0083] S320: Given any initial values ​​for the capacitance and inductance parameters in a passive damping device, obtain the output impedance transfer function containing two variables: resistance and frequency.

[0084] S330: Select non-negative values ​​for the resistance parameter and frequency to obtain a three-dimensional image of the criterion function, and then project the non-positive values ​​of the criterion function onto the resistance-frequency plane.

[0085] S340, In the resistance-frequency plane, when the frequency value takes any value f∈(0,∞), the set of resistance parameter values ​​that do not fall within the projection area is the range of resistance parameter values, and thus the value of the resistance parameter is determined.

[0086] S350, by changing the capacitor and inductor parameter values ​​and performing iterative calculations, obtains the resistance parameter value, and then obtains the parameter values ​​of the passive damping device that meet the various requirements of the project.

[0087] Specifically, the parametric projection domain method is used to select the component parameters of the passive damping device. The implementation method of the parametric projection domain method is as follows:

[0088] A. Let the equivalent impedance of the AC side of the converter be Z. m (f) The equivalent impedance of the passive damping device is Z. f (f) Let the constant positive damping criterion function of the AC port be... First, calculate the AC output impedance of the converter, so that the positive damping criterion function M... ac It contains only four variables: R, L, C, and f, where R, L, and C are the equivalent resistance, equivalent capacitance, and equivalent inductance parameters of the passive damping device, respectively.

[0089] B. Based on a certain parameter setting method, first give the values ​​of two variables among R, L, and C, so that M... ac (f,Z fx It contains only two variables, where Z is the variable. fx Represents variables not given in R, L, C;

[0090] C, Z fx And f takes non-negative values, plot M ac (f,Z fx ) 3D image, M ac After taking non-positive values, project them onto fZ fx On a plane;

[0091] D, in fZ fx In a plane, when the frequency takes any value f∈(0,∞), Z fx The set of values ​​that do not fall within the projection area is the value interval; then, Z is determined according to a certain parameter selection method. fx The possible values ​​of ;

[0092] E. After completing the above round of parameter selection, the values ​​of the parameters given in step B can be changed, and the above calculations can be performed again. This process can be repeated until the parameter values ​​of the passive damping device that meet the various requirements of the project are obtained.

[0093] The calculation principle of the above design criteria is as follows:

[0094] Let the equivalent AC output impedance Z of the transformer grid side of the converter be... m (f)=X(f)+Y(f)i, where X(f) and Y(f) are the real and imaginary parts of its equivalent impedance, respectively; the equivalent impedance Z of the passive damping device f (f)=A(f)+B(f)i, where A(f) and B(f) are the real and imaginary parts of its equivalent impedance, respectively.

[0095] When the filter is connected in parallel to the transformer grid side of the converter, the overall AC port impedance Z ac for

[0096]

[0097] make but

[0098]

[0099] To ensure that the AC port is always positively damped, it is necessary to make Due to Re(Z) ac If the denominator is not negative, then when M > 0, the AC port damping is always positive.

[0100] In the expression for M, A is the real part of the impedance of the passive damping device, which is always non-negative. Therefore, when X > 0, M > 0 always holds true; when X < 0, the output of M is uncertain. Therefore, considering only the case when X < 0, the constant positive damping criterion for the AC port is obtained as follows:

[0101]

[0102] Since the impedance magnitude is more intuitive in the graphical method, equation (3) can be expressed in the following form:

[0103]

[0104] In a specific embodiment of the present invention, the parameter calculation method for the passive damping device of the modular multilevel converter is as follows:

[0105] (1) Using various impedance modeling methods, the AC port impedance model of the converter is obtained, and the real part of the converter impedance and the impedance amplitude as a function of frequency are derived. The simplified transfer function of the converter in the high-frequency range using the half-bridge submodule topology is shown in Equation (5).

[0106]

[0107] In the formula: L m This is the sum of the transformer leakage reactance and half of the bridge arm reactance referred to the transformer grid side; T dc To control link delay; k pi and k ii These are the proportional and integral parameters of the inner loop, respectively; f is the frequency.

[0108] (2) Select the passive damping device topology and take the single-tuned filter as an example to obtain the filter transfer function, as shown in equation (6).

[0109]

[0110] In the formula: R is the filter resistor; L is the filter inductance; C is the filter capacitor.

[0111] (3) Calculate M ac Criterion function;

[0112] (4) Select the initial value of the capacitor based on the voltage level and existing equipment manufacturing capabilities; then select the inductor parameters so that the initial cutoff frequency falls within the negative damping range of the converter. Because the converter impedance model contains delay and other components, the analytical solutions for the real part and amplitude are difficult to obtain. Mathematical tools can be used to discretize it, obtaining the M value containing the resistance R and frequency f variables at 1Hz frequency intervals. ac (f,R) function;

[0113] (5) Based on the engineering design requirements, given the parameter selection ranges for R and f, use mathematical tools to plot M. ac The three-dimensional graph of the function (f,R); take M ac For values ​​of (f,R)≤0, project them onto the fR plane;

[0114] (6) Avoid the projection region when selecting R parameters; since M needs to be at any frequency ac Since the criterion function values ​​are all greater than zero, we can draw horizontal lines along the upper and lower edges of the projection region parallel to the f-coordinate axis to obtain the range of values ​​for R, such as... Figure 6 As shown;

[0115] (7) Based on the relationship between the filter resistance and the loss, select an appropriate value for R from the range of values ​​in the previous step. Taking a single-tuned filter as an example, its power frequency loss is approximately calculated as shown in equation (7).

[0116]

[0117] In the formula: V sω1 is the mains voltage at the filter connection point; ω1 is the power frequency angular velocity. When the capacitor is fixed, it can be approximated that the larger the resistance, the higher the filter loss. Therefore, the minimum value of the aforementioned range of R values ​​can be selected.

[0118] (8) Reduce the value of capacitor C and repeat steps 5 to 7, iterating until the filter parameters that meet the cost and loss requirements of the project are obtained. Taking a single-tuned filter as an example, when capacitor C is reduced to a certain extent, the projection area of ​​the fR plane will cross the R coordinate, which will not yield the required R value; at this time, the value of inductor L can be appropriately increased to lower the cutoff frequency and expand the lower limit of the capacitor value. In actual engineering, the final set of filter parameters will be determined after comparing factors such as cost and long-term loss according to the project requirements.

[0119] Specifically, the method for setting the preset parameters is as follows: considering the engineering cost and manufacturing difficulty, the minimum value of the capacitor parameter is taken as the priority constraint condition, the capacitor parameter value is determined first, and then the inductor parameter value is determined; after obtaining the range of values ​​of the resistor parameter value projected on the resistance-frequency plane, the minimum loss is taken as the constraint condition to determine the resistor parameter value.

[0120] Figure 7 This is a block diagram of the modular multilevel converter passive damping device parameter calculation device module provided in the embodiment of the present invention.

[0121] Accordingly, please refer to Figure 7 The second aspect of the present invention provides a parameter calculation device for a modular multilevel converter passive damping device, comprising: an acquisition module 1, a first selection module 2, and a second selection module 3.

[0122] The acquisition module 1 is used to acquire the AC port impedance transfer function and filter transfer function of the converter, and then obtain the constant positive damping criterion function of the AC port of the converter. The first selection module 2 is used to select the capacitor and inductor parameter values ​​in the passive damping device based on the criterion function and a preset parameter setting method. The second selection module 3 is used to obtain the value range of the resistance parameter in the passive damping device through the parameter projection domain method, and select the resistance parameter value based on the principle of minimum loss.

[0123] Furthermore, the parameter calculation device for the passive damping device of the modular multilevel converter also includes: an iteration module 4. The iteration module 4 is used to reduce the capacitor parameter value and update the resistor parameter value according to the parameter projection domain method to obtain the passive damping device parameter values ​​that meet the cost and loss requirements.

[0124] Figure 8 This is a schematic diagram of the acquisition module provided in an embodiment of the present invention.

[0125] Further, please refer to Figure 8The first acquisition module 1 includes a first acquisition unit 11, a second acquisition unit 12, and a third acquisition unit 13. The first acquisition unit 11 is used to obtain the AC port impedance model of the converter through impedance modeling methods, and then obtain the real part of the converter impedance and the function of impedance amplitude as a function of frequency. The second acquisition unit 12 is used to select a passive damping topology, and then obtain its topology transfer function. The third acquisition unit 13 is used to obtain the constant positive damping criterion function of the AC port of the converter containing the passive damping device.

[0126] Figure 9 This is a schematic diagram of the second selection module provided in an embodiment of the present invention.

[0127] Further, please refer to Figure 9 The second selection module 3 includes: a calculation unit 31, an assignment unit 32, an image generation unit 33, a resistance selection unit 34, and an iteration unit 35. The calculation unit 31 calculates the AC output impedance of the converter. The assignment unit 32 arbitrarily assigns initial values ​​to the capacitor and inductor parameters in the passive damping device to obtain an output impedance transfer function containing two variables: resistance and frequency. The image generation unit 33 selects non-negative values ​​for the resistance and frequency values ​​in the output impedance transfer function to obtain a three-dimensional image of the criterion function, and projects the non-positive values ​​of the criterion function onto the resistance-frequency plane. The resistance selection unit 34 determines the resistance parameter range by identifying the set of resistance parameter values ​​that do not fall within the projection area when the frequency value is any value f∈(0,∞) in the resistance-frequency plane. The iteration unit 35 changes the capacitor and inductor parameter values ​​and performs iterative calculations to obtain the resistance parameter values, thereby obtaining the passive damping device parameter values ​​that meet various engineering requirements.

[0128] Furthermore, the method for setting the preset parameters is as follows: considering the engineering cost and manufacturing difficulty, the minimum value of the capacitor parameter is taken as the priority constraint condition, the capacitor parameter value is determined first, and then the inductor parameter value is determined; after obtaining the range of values ​​of the resistor parameter value projected on the resistance-frequency plane, the minimum loss is taken as the constraint condition to determine the resistor parameter value.

[0129] Accordingly, a third aspect of the present invention also provides an electronic device, comprising: at least one processor; and a memory connected to the at least one processor. The memory stores instructions executable by a processor, which, when executed by the processor, cause the at least one processor to perform the aforementioned method for calculating the parameters of a modular multilevel converter passive damping device.

[0130] Furthermore, a fourth aspect of the present invention provides a computer-readable storage medium storing computer instructions that, when executed by a processor, implement the above-described method for calculating the parameters of a passive damping device for a modular multilevel converter.

[0131] This invention aims to protect a method and apparatus for calculating parameters of a passive damping device in a modular multilevel converter. The method includes the following steps: obtaining the AC port impedance transfer function and filter transfer function of the converter, and then obtaining the constant positive damping criterion function of the AC port of the converter; selecting the capacitance and inductance parameter values ​​in the passive damping based on the criterion function and a preset parameter setting method, so that the filter cutoff frequency of the passive damping is located in the negative damping range of the converter; obtaining the value range of the resistance parameter values ​​in the passive damping through the parameter projection domain method, and selecting the resistance parameter values ​​according to the principle of minimum loss. The above technical solution has the following effects:

[0132] To address broadband harmonic resonance suppression in the mid-to-high frequency band, the constant positive damping criterion for the AC port of a converter with a passive damping device clarifies the impedance reshaping frequency range and parameter selection requirements for passive damping. Furthermore, the parameter projection domain method provides an intuitive graphical approach for selecting the parameters of the passive damping device components, making it easier to understand and operate. The constraints of minimizing capacitance and damping resistance loss in parameter selection provide a direction for selecting the parameters of the passive damping device components, reducing the size, cost, and losses of the equipment, and facilitating its engineering application and promotion.

[0133] It should be understood that the specific embodiments described above are merely illustrative or explanatory of the principles of the invention and do not constitute a limitation thereof. Therefore, any modifications, equivalent substitutions, improvements, etc., made without departing from the spirit and scope of the invention should be included within the protection scope of the invention. Furthermore, the appended claims are intended to cover all variations and modifications falling within the scope and boundaries of the appended claims, or equivalent forms of such scope and boundaries.

Claims

1. A method for calculating parameters of a passive damping device in a modular multilevel converter, characterized in that, Includes the following steps: Obtain the AC port impedance transfer function and filter transfer function of the converter, and then obtain the constant positive damping criterion function of the AC port of the converter including the passive damping device; Based on the criterion function, and combined with the preset parameter setting method, the capacitance and inductance parameter values ​​in the passive damping device are selected. The range of resistance parameters in the passive damping device is obtained by the parametric projection domain method, and the resistance parameter values ​​are selected based on the principle of minimum loss. The method of obtaining the range of values ​​for the resistance parameters in the passive damping device using the parametric projection domain method includes: Calculate the AC port output impedance of the converter including the passive damping device; Given any initial values ​​for the capacitance and inductance parameters in the passive damping device, the output impedance transfer function containing two variables, resistance and frequency, is obtained. By selecting non-negative values ​​for the resistance parameter and frequency in the output impedance transfer function, a three-dimensional image of the criterion function is obtained, and the criterion function is projected onto the resistance-frequency plane after taking non-positive values. In the resistance-frequency plane, when the frequency value is taken For any value of the resistance parameter, the set of values ​​that do not fall within the projection area is the range of values ​​for the resistance parameter, thereby determining the value of the resistance parameter. By changing the capacitor and inductor parameter values ​​and performing iterative calculations, the resistance parameter value is obtained, thereby obtaining the parameter values ​​of the passive damping device that meet the various requirements of the project.

2. The method for calculating the parameters of the passive damping device of the modular multilevel converter according to claim 1, characterized in that, After selecting the resistance parameter value based on the principle of minimum loss, the method further includes: The capacitance parameter value is reduced, and the resistance parameter value is updated according to the parameter projection domain method to obtain the parameter values ​​of the passive damping device that meet the cost and loss requirements.

3. The method for calculating the parameters of the passive damping device of the modular multilevel converter according to claim 1, characterized in that, The process of obtaining the AC port impedance transfer function and filter transfer function of the converter, and then obtaining the constant positive damping criterion function of the AC port of the converter, includes: The AC port impedance model of the converter is obtained by impedance modeling method, and then the real part of the converter impedance and the impedance amplitude as a function of frequency are obtained. The passive damping topology is selected, and its transfer function is obtained. Obtain the constant positive damping criterion function for the AC port of the converter, which includes the passive damping device.

4. The method for calculating the parameters of the passive damping device of the modular multilevel converter according to claim 1, characterized in that, The method for giving the preset parameters is as follows: Considering the engineering cost and manufacturing difficulty, the minimum value of the capacitor parameter is taken as the primary constraint condition. The value of the capacitor parameter is determined first, and then the value of the inductor parameter is determined. After obtaining the range of values ​​of the resistance parameter projected onto the resistance-frequency plane, the resistance parameter value is determined with minimum loss as the constraint.

5. A parameter calculation device for a modular multilevel converter passive damping device, characterized in that, include: The acquisition module is used to acquire the AC port impedance transfer function and filter transfer function of the converter, and then obtain the constant positive damping criterion function of the AC port of the converter including the passive damping device. The first selection module selects the capacitance and inductance parameter values ​​in the passive damping device based on the criterion function and a preset parameter setting method. The second selection module is used to obtain the range of resistance parameters in the passive damping device through the parameter projection domain method, and select the resistance parameter value according to the principle of minimum loss. The second selection module includes: A calculation unit for calculating the AC port output impedance of the converter containing the passive damping device; The assignment unit is used to arbitrarily give the initial values ​​of the capacitance and inductance parameters in the passive damping device to obtain the output impedance transfer function containing the two variables of resistance and frequency. An image generation unit is used to select non-negative values ​​for the resistance parameter and frequency values ​​in the output impedance transfer function, obtain a three-dimensional image of the criterion function, and project the non-positive values ​​of the criterion function onto the resistance-frequency plane. A resistor selection unit is used in the resistor-frequency plane to select a frequency value when the frequency value is... For any value of the resistance parameter, the set of values ​​that do not fall within the projection area is the range of values ​​for the resistance parameter, thereby determining the value of the resistance parameter. An iterative unit is used to change the capacitance parameter value and the inductance parameter value, and perform iterative calculations to obtain the resistance parameter value, thereby obtaining the passive damping device parameter value that meets various requirements in the project.

6. The parameter calculation device for the modular multilevel converter passive damping device according to claim 5, characterized in that, Also includes: An iterative module is used to reduce the capacitance parameter value and update the resistance parameter value according to the parameter projection domain method to obtain the passive damping parameter value that meets the cost and loss requirements.

7. The parameter calculation device for the modular multilevel converter passive damping device according to claim 5, characterized in that, The first selection module includes: The first acquisition unit is used to obtain the AC port impedance model of the converter through an impedance modeling method, and then obtain the real part of the converter impedance and the function of impedance amplitude as a function of frequency. The second acquisition unit is used to select the passive damping topology and then obtain its topology transfer function; The third acquisition unit is used to acquire the constant positive damping criterion function of the AC port of the converter, which includes the passive damping device.

8. The parameter calculation device for the modular multilevel converter passive damping device according to claim 5, characterized in that, The method for giving the preset parameters is as follows: Considering the engineering cost and manufacturing difficulty, the minimum value of the capacitor parameter is taken as the primary constraint condition. The value of the capacitor parameter is determined first, and then the value of the inductor parameter is determined. After obtaining the range of values ​​of the resistance parameter projected onto the resistance-frequency plane, the resistance parameter value is determined with minimum loss as the constraint.

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