Converter governance potential analysis method and device, computer equipment, readable storage medium and program product

Abstract

The invention relates to a governance potential analysis method and device of a converter, computer equipment, a computer readable storage medium and a computer program product. The method comprises the following steps: establishing a grid-connected converter system small disturbance model; establishing a transfer function model of the stability of the grid-connected converter system based on the small disturbance model of the grid-connected converter system; according to the transfer function model, traversing any group of working points in the grid-connected converter system, and determining a security domain of the system; the group of working points is a combination of an active power preset value and a reactive power preset value; and analyzing the position of the to-be-predicted working point in the security domain and the position relationship between the to-be-predicted working point and the boundary of the security domain to obtain the power margin of the converter, and taking the power margin as the governance potential of the converter. By adopting the method, the final analysis on the governance potential of the converter can be more accurate and simpler.

Description

Technical Field

[0001] The present application relates to the field of data analysis technology, and in particular to a method, device, computer equipment, computer-readable storage medium and computer program product for analyzing the governance potential of a converter. Background Art

[0002] With the access of a high proportion of renewable energy and power electronic equipment, power quality problems such as harmonic pollution and voltage deviation at the common coupling point of the power grid have become increasingly prominent, and multifunctional converters that integrate grid-connected power generation, harmonic control and voltage support have attracted widespread attention. Using multifunctional converters for power quality control not only improves the utilization rate of converters, but also reduces investment costs and maintenance costs.

[0003] However, existing technologies often only consider one factor, the converter capacity constraint, to optimize the remaining capacity, without considering that the converter output power is also limited by system stability, resulting in inaccurate analysis of the converter's remaining capacity, i.e., the converter's power quality management potential. Summary of the invention

[0004] Based on this, it is necessary to provide a method, device, computer equipment, computer-readable storage medium and computer program product for analyzing the governance potential of a converter, which can accurately calculate the governance potential of the converter, in order to address the above-mentioned technical problems.

[0005] In a first aspect, the present application provides a method for analyzing the governance potential of a converter, comprising:

[0006] Establish a small disturbance model of the grid-connected converter system;

[0007] Based on the small disturbance model of the grid-connected power conversion system, a transfer function model of the stability of the grid-connected power conversion system is established;

[0008] According to the transfer function model, traverse any set of operating points in the grid-connected converter system to determine the safety domain of the system; the set of operating points is a combination of active power preset values ​​and reactive power preset values;

[0009] The position of the working point to be predicted in the safety domain and its positional relationship with the boundary of the safety domain are analyzed to obtain the power margin of the converter, and the power margin is used as the control potential of the converter.

[0010] In one embodiment, the establishing of a small disturbance model of a grid-connected power conversion system includes:

[0011] Modeling is done based on the main circuit and control part of the grid-connected converter system, and the operating point variables are introduced using the dynamic characteristics of the phase-locked loop;

[0012] A small disturbance model of a grid-connected converter system including the operating point variables and under constant power control is established; the operating point variables are active power and reactive power input to the grid-connected converter system.

[0013] In one embodiment, the step of establishing a transfer function model of the stability of the grid-connected power conversion system based on the small disturbance model of the grid-connected power conversion system includes:

[0014] Based on the small disturbance model of the grid-connected power conversion system, in combination with the phase-locked loop and the grid strength, a first expression between the current disturbance value of the direct-axis output, the reference disturbance value of the active power and the reference disturbance value of the reactive power, and a second expression between the current disturbance value of the quadrature-axis output, the reference disturbance value of the active power and the reference disturbance value of the reactive power are determined;

[0015] According to the first expression and the second expression, a transfer function model of the stability of the grid-connected converter system is determined.

[0016] In one embodiment, traversing any set of operating points of the grid-connected converter system according to the transfer function model to determine the safety domain of the system includes:

[0017] Determine the working point to be analyzed;

[0018] Among the working points, the working points satisfying a first preset condition are screened to obtain a first working point set; the first preset condition is satisfying a topological constraint of a system voltage;

[0019] For the first working point set, screening working points that meet a second preset condition to obtain a second working point set; the second preset condition is to meet a power transmission limit of the system;

[0020] For the second working point set, screening working points that meet a third preset condition to obtain a third working point set;

[0021] A safety domain of the system is drawn according to the working points in the third working point set.

[0022] In one embodiment, the step of screening the working points satisfying a third preset condition for the second working point set to obtain a third working point set includes:

[0023] Substituting the operating points in the second operating point set into the common denominator polynomial to solve for the closed-loop poles;

[0024] If the pole with the largest real part in the closed-loop pole is located in the left half plane of the complex plane, the operating point is determined to be stable, and the corresponding operating point is added to the third operating point set; otherwise, the operating point is determined to be unstable; the common denominator polynomial is the denominator polynomial of the closed-loop transfer function in the transfer function, and the denominator polynomials of the closed-loop transfer functions are the same.

[0025] In one embodiment, analyzing the positional relationship between the position of the operating point to be predicted in the safety domain and the boundary of the safety domain to obtain the power margin of the converter, and using the power margin as the control potential of the converter includes:

[0026] According to the position of the working point to be predicted in the safety domain, the distance of the working point to be predicted from the boundary of the safety domain is measured as the power margin of the converter, and the power margin is used as the control potential of the converter.

[0027] In a second aspect, the present application also provides a device for analyzing the governance potential of a converter, comprising:

[0028] Building module for building small disturbance model of grid-connected converter system;

[0029] The building module is further used to establish a transfer function model of the stability of the grid-connected power conversion system based on the small disturbance model of the grid-connected power conversion system;

[0030] A determination module, used to traverse any set of operating points in the grid-connected converter system according to the transfer function model to determine the safety domain of the system; the set of operating points is a combination of active power preset values ​​and reactive power preset values;

[0031] The analysis module is used to analyze the position of the working point to be predicted in the safety domain and the positional relationship between the working point to be predicted and the boundary of the safety domain, so as to obtain the power margin of the converter and use the power margin as the control potential of the converter.

[0032] In a third aspect, the present application further provides a computer device, including a memory and a processor, wherein the memory stores a computer program, and when the processor executes the computer program, the following steps are implemented:

[0033] Establish a small disturbance model of grid-connected converter system;

[0034] Based on the small disturbance model of the grid-connected power conversion system, a transfer function model of the stability of the grid-connected power conversion system is established;

[0035] According to the transfer function model, traverse any set of operating points in the grid-connected converter system to determine the safety domain of the system; the set of operating points is a combination of active power preset values ​​and reactive power preset values;

[0036] The position of the working point to be predicted in the safety domain and its positional relationship with the boundary of the safety domain are analyzed to obtain the power margin of the converter, and the power margin is used as the control potential of the converter.

[0037] In a fourth aspect, the present application further provides a computer-readable storage medium having a computer program stored thereon, wherein when the computer program is executed by a processor, the following steps are implemented:

[0038] Establish a small disturbance model of the grid-connected converter system;

[0039] Based on the small disturbance model of the grid-connected power conversion system, a transfer function model of the stability of the grid-connected power conversion system is established;

[0040] According to the transfer function model, traverse any set of operating points in the grid-connected converter system to determine the safety domain of the system; the set of operating points is a combination of active power preset values ​​and reactive power preset values;

[0041] The position of the working point to be predicted in the safety domain and its positional relationship with the boundary of the safety domain are analyzed to obtain the power margin of the converter, and the power margin is used as the control potential of the converter.

[0042] In a fifth aspect, the present application further provides a computer program product, including a computer program, which implements the following steps when executed by a processor:

[0043] Establish a small disturbance model of the grid-connected converter system;

[0044] Based on the small disturbance model of the grid-connected power conversion system, a transfer function model of the stability of the grid-connected power conversion system is established;

[0045] According to the transfer function model, traverse any set of operating points in the grid-connected converter system to determine the safety domain of the system; the set of operating points is a combination of active power preset values ​​and reactive power preset values;

[0046] The position of the working point to be predicted in the safety domain and its positional relationship with the boundary of the safety domain are analyzed to obtain the power margin of the converter, and the power margin is used as the control potential of the converter.

[0047] The above-mentioned converter governance potential analysis method, device, computer equipment, computer readable storage medium and computer program product, first, establish a small disturbance model of the grid-connected converter system, and establish a transfer function model of the stability of the grid-connected converter system based on the small disturbance model of the grid-connected converter system, so that the stability analysis of the grid-connected converter system is clearer. By continuously adjusting the active power and reactive power input by the grid-connected converter system, the safety domain of the grid-connected converter system is determined, and the area where the grid-connected converter system can operate stably can be more intuitively observed. By analyzing the position of the working point to be predicted in the safety domain and the position of the safety domain boundary, the power margin of the converter can be obtained, and the power margin of the converter is used as the governance potential of the converter. The power margin of the converter is used to represent the governance potential of the converter, making the governance potential of the converter more intuitive. In this way, by analyzing different influencing factors in the grid-connected converter system, drawing the safety domain, and intuitively showing the governance potential of the converter under different conditions, the final analysis of the governance potential of the converter is more accurate and concise. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] In order to more clearly illustrate the technical solutions in the embodiments of the present application or related technologies, the drawings required for use in the embodiments of the present application or related technical descriptions will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0049] FIG1 is an application environment diagram of a method for analyzing the governance potential of a converter in one embodiment;

[0050] FIG2 is a schematic flow chart of a method for analyzing the governance potential of a converter in one embodiment;

[0051] FIG3 is a schematic flow chart of a method for analyzing the governance potential of a converter in another embodiment;

[0052] FIG4 is a safety domain diagram drawn in a method for analyzing the governance potential of a converter in one embodiment;

[0053] FIG5 is a diagram of converter governance potential analysis based on a security domain in a converter governance potential analysis method in one embodiment;

[0054] FIG6 is a diagram showing the operation results of an actual current conversion test system in a method for analyzing the governance potential of a current converter in one embodiment;

[0055] FIG7 is a block diagram of a device for analyzing the governance potential of a converter in one embodiment;

[0056] FIG. 8 is a diagram showing the internal structure of a computer device in one embodiment. DETAILED DESCRIPTION

[0057] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0058] The converter governance potential analysis method provided in this embodiment can be applied in the application environment shown in FIG. 1 .

[0059] In one embodiment, as shown in FIG2 , a method for analyzing the governance potential of a converter is provided. This embodiment uses the method applied to a terminal as an example. It is understandable that the method can also be applied to a server, and can also be applied to a system including a terminal and a server, and is implemented through the interaction between the terminal and the server. In this embodiment, the method includes the following steps 202 to 208:

[0060] Step 202: Establish a small disturbance model of the grid-connected converter system.

[0061] The grid-connected converter system is the system structure in the converter. The small disturbance model is a model established by the terminal to analyze the stability of the system.

[0062] Specifically, the terminal will perform small disturbance modeling based on the main circuit and control part of the grid-connected converter system, and at the same time use the dynamic characteristics of the phase-locked loop to introduce the operating point variable to establish a small disturbance model of the grid-connected converter system under constant power control.

[0063] Step 204: Establish a transfer function model of the stability of the grid-connected power conversion system based on the small disturbance model of the grid-connected power conversion system.

[0064] Among them, the transfer function model is a model used to describe the relationship between system input and output.

[0065] In some embodiments, the terminal will determine a first expression between the disturbance value of the direct-axis output, the reference disturbance value of the active power and the reference disturbance value of the reactive power, and a second expression between the current disturbance value of the quadrature-axis output, the reference disturbance value of the active power and the reference disturbance value of the reactive power based on the small disturbance model of the grid-connected power conversion system and in combination with the phase-locked loop and the grid strength, and then determine the transfer function model of the stability of the grid-connected power conversion system based on the first expression and the second expression.

[0066] Step 206, according to the transfer function model, traverse any set of operating points in the grid-connected converter system to determine the safety domain of the system; a set of operating points is a combination of active power preset values ​​and reactive power preset values.

[0067] In some embodiments, the terminal determines the operating points that need to be analyzed, and selects the operating points that meet the topological constraints of the system voltage from the operating points that need to be analyzed to obtain a first operating point set. The operating points that meet the power transmission constraints of the system are selected from the first operating point set to obtain a second operating point set. The operating points that meet the third preset condition are selected from the second operating point set to obtain a third operating point set. Finally, the safety domain of the grid-connected converter system is drawn based on the operating points in the third operating point set.

[0068] Step 208, analyzing the position of the to-be-predicted operating point in the safety domain and its positional relationship with the boundary of the safety domain, obtaining the power margin of the converter, and using the power margin as the control potential of the converter.

[0069] Among them, power margin refers to the additional power capacity reserved in the power system to ensure the stable operation of the system and cope with possible load changes.

[0070] In some embodiments, the terminal measures the distance of the working point to be predicted from the boundary of the safety domain according to the position of the working point to be predicted in the safety domain as the power margin of the converter, and uses the power margin as the governance potential of the converter.

[0071] In the above-mentioned converter governance potential analysis method, a small disturbance model of the grid-connected converter system is established. According to the small disturbance model of the grid-connected converter system, a transfer function model of the stability of the grid-connected converter system is established, so that the stability analysis of the grid-connected converter system is clearer. By continuously adjusting the active power and reactive power input to the grid-connected converter system and determining the safety domain of the grid-connected converter system, the area in which the grid-connected converter system can operate stably can be more intuitively observed. By analyzing the position of the working point to be predicted in the safety domain and the position of the safety domain boundary, the power margin of the converter can be obtained, and the power margin of the converter is used as the governance potential of the converter. The power margin of the converter is used to represent the governance potential of the converter, making the governance potential of the converter more intuitive. In this way, by analyzing different influencing factors in the grid-connected converter system, drawing the safety domain, and intuitively showing the governance potential of the converter under different circumstances, the final analysis of the governance potential of the converter is more accurate and concise.

[0072] Next, the analysis of the converter's governance potential and the specific implementation process are explained.

[0073] In some exemplary embodiments, a small disturbance model of a grid-connected converter system is established, including: modeling based on the main circuit and control part of the grid-connected converter system, and introducing an operating point variable using the dynamic characteristics of a phase-locked loop; establishing a small disturbance model of the grid-connected converter system that includes an operating point variable and is under constant power control; the operating point variables are the active power and reactive power input to the grid-connected converter system.

[0074] In actual implementation, due to the existence of SRF-PLL (phase-locked loop based on synchronous reference frame), the voltage disturbance at PCC (point of common coupling) will cause the actual PCC voltage phase angle Phase angle with the phase-locked loop output voltage difference To distinguish The corresponding synchronous coordinate system, in which the physical quantities are marked with superscript s; Corresponding to the control coordinate system, the physical quantities are marked with superscript c, and the variables with an * in the upper right corner are the complex numbers of the variables.

[0075] In the following formula, Indicates the amplitude of the grid phase voltage, are its d-axis and q-axis components respectively, represents the d and q axis components of the PCC point current, and . represents the d and q axis components of the PCC voltage, and .

[0076] The transformation relationship between the control coordinate system and the synchronous reference system is shown in formula (1).

[0077]

[0078] in, is the steady-state value of the variable x.

[0079] The dynamic characteristics of the converter side in the synchronous coordinate system are shown in formula (2).

[0080]

[0081] in, , is the equivalent impedance of the filter inductor, is the grid-connected current in the synchronous coordinate system, is the grid-connected voltage in the synchronous coordinate system, is the equivalent impedance of the power grid, is the grid voltage in the synchronous coordinate system, is the inductance of the filter, is the resistance of the filter, is the equivalent inductance of the power grid, is the equivalent resistance, is the rated angular frequency, is an imaginary unit.

[0082] In this embodiment, the converter adopts simplified PQ control (constant power control). In the coordinate transformation, the d-axis (direct axis) is selected to be in the same direction as the PCC voltage vector, so that the q-axis (quadrature axis) component of the PCC voltage is 0, and the power output expression is simplified, thereby obtaining the reference value of the current as shown in formula (3).

[0083]

[0084] in, is the input active power, is the input reactive power, is the steady-state value of the voltage on the d-axis at the PCC point, is the steady-state voltage value at PCC point, .

[0085] The modulation voltage of the converter is determined by the current controller, and the formula of the current controller is shown in (4).

[0086]

[0087] in, represents the controller of the current loop, represents the proportional parameter of the controller, Represents the controller integral parameter.

[0088] In the SRF-PLL link, the working variables are introduced, and the transformation relationship between the disturbance quantities of each voltage and current in different reference frames is shown in formula (5).

[0089]

[0090] in, Represents the grid-connected current steady-state value vector, is the steady-state value vector of the converter output voltage, is the steady-state value vector of the voltage at the PCC point. From the above formula, it can be seen that the dynamic characteristics of the converter side and the converter modulation voltage are shown in formula (6), and the small disturbance expression of the reference value of the current loop is shown in formula (7).

[0091]

[0092]

[0093] The expression of the phase-locked loop is shown in formula (8).

[0094]

[0095] in, , represents a phase-locked loop controller, represents the proportional parameter of the controller, Represents the controller integral parameter.

[0096] In summary, the expression of the modulation voltage disturbance of the converter after conversion from the control coordinate system to the synchronization coordinate system is shown in formula (9).

[0097]

[0098] In the synchronous coordinate system, the relationship between the voltage in the converter and the modulation voltage is shown in formula (10).

[0099]

[0100] in, is the PWM modulation (pulse width modulation) gain, represents delay. In this embodiment, modulation and delay are ignored, so .

[0101] Substituting the above formula (6) into formula (10), we obtain formula (11).

[0102]

[0103] Simplifying formula (11), the disturbance expression of PCC current is obtained as shown in formula (12).

[0104]

[0105] in, .

[0106] Furthermore, the perturbation relation of the phase-locked loop (8) is substituted into formula (12), eliminating We get formula (13).

[0107]

[0108] in, , and then eliminate the PCC voltage disturbance in the formula and its conjugation We get formula (14).

[0109]

[0110] make , Formula (15) is obtained. Formula (15) is the small disturbance model of the grid-connected converter system.

[0111]

[0112] In the above embodiment, by fully considering the changes of various factors in the grid-connected converter and combining the dynamic characteristics of the phase-locked loop, a small disturbance model of the grid-connected converter system is established, making the subsequent analysis of the stability of the system more convenient.

[0113] In some exemplary embodiments, based on the small disturbance model of the grid-connected power conversion system, a transfer function model of the stability of the grid-connected power conversion system is established, including: based on the small disturbance model of the grid-connected power conversion system, in combination with the phase-locked loop and the grid strength, determining a first expression between the disturbance value of the direct-axis output, the reference disturbance value of the active power and the reference disturbance value of the reactive power, and a second expression between the current disturbance value of the quadrature-axis output, the reference disturbance value of the active power and the reference disturbance value of the reactive power; according to the first expression and the second expression, determining the transfer function model of the stability of the grid-connected power conversion system.

[0114] In actual implementation, the terminal will derive the expressions between the d-axis and q-axis output current disturbance values ​​and the reference disturbance values ​​of active power and reactive power based on the small disturbance model of the grid-connected converter system and taking into account the influence of the phase-locked loop and grid strength.

[0115] Specifically, the first expression between the current disturbance value of the d-axis output, the reference disturbance value of the active power and the reference disturbance value of the reactive power and the second expression between the current disturbance value of the q-axis output, the reference disturbance value of the active power and the reference disturbance value of the reactive power are as shown in formula (16).

[0116]

[0117] in, .

[0118] The above formula (16) is the transfer function model of the grid-connected converter system stability.

[0119] In the above embodiment, the influence of the phase-locked loop and the grid strength is fully considered, and a grid-connected conversion system stability model of the converter is established, so that the subsequent analysis of the system stability is more accurate.

[0120] In some exemplary embodiments, a safety domain of a grid-connected power conversion system is determined by traversing any group of working points of the grid-connected power conversion system according to a transfer function model, including: determining the working point to be analyzed; among the working points, screening the working points that meet a first preset condition to obtain a first working point set; the first preset condition is to meet the topological constraint of the system voltage; for the first working point set, screening the working points that meet a second preset condition to obtain a second working point set; the second preset condition is to meet the power transmission limitation of the system; for the second working point set, screening the working points that meet a third preset condition to obtain a third working point set; and drawing the safety domain of the system according to the working points in the third working point set.

[0121] In some embodiments, the terminal determines the active power and reactive power of the input system to be analyzed, i.e., the operating point variable, according to the specific situation, and specifies its initial value, change step, and change range. For the specified operating point variable, when the stable state is reached, the output power of the device can be approximated to the reference power, as shown in formula (17).

[0122]

[0123] The grid voltage is , the voltage at the common coupling point and the grid are connected by an impedance Therefore, the topological constraint relationship between the d-axis component of the PCC point voltage and the grid voltage is shown in formula (18).

[0124]

[0125] The determined working points are substituted into the above topological constraint relationship to screen out the first working point set.

[0126] The power transfer limit formula of the system is shown in (19).

[0127]

[0128] in, , .

[0129] Substitute the working points in the first working point set into the power transfer limit formula to filter out the second working point set that meets the formula. If the power transfer limit is not met, there is no need to analyze its stability, and let symb = 2. Where symb represents the stability analysis result of the working point.

[0130] In some exemplary embodiments, for the second working point set, working points that meet the third preset condition are screened to obtain the third working point set, including: substituting the working points in the second working point set into the common denominator polynomial to solve the closed-loop poles; if the pole with the largest real part in the closed-loop poles is located in the left half plane of the complex plane, then the working point is determined to be stable, and the corresponding working point is added to the third working point set; otherwise, the working point is determined to be unstable; the common denominator polynomial is the denominator polynomial of the closed-loop transfer function in the transfer function, and the denominator polynomials of the closed-loop transfer functions are the same.

[0131] In some embodiments, the working points in the second working point set are substituted into the common denominator polynomial, and the closed-loop poles are solved. The working points with the largest real part in the closed-loop points located in the left half plane of the complex plane are selected as the third working point set, and the working points in the working point set are set to have symb=1. The common denominator polynomial is: The denominator of The remaining operating points in the second operating point set are unstable, and their symb=0.

[0132] In the above embodiment, by further screening the working points, the safety domain finally divided is made more practical, and the analysis of the control potential of the converter is more accurate.

[0133] Furthermore, after screening the working points in different situations, the terminal obtains the stability result of each group of working points, namely, the symb value, divides the system into different areas, and draws a safety domain image of the system according to the stability results of the working points.

[0134] In the above embodiment, the safety domain of the system is finally determined by gradually screening the working points in various situations, so that the final stability range of the system is more intuitive and convenient for analyzing the governance potential of the converter.

[0135] In some exemplary embodiments, the positional relationship between the position of the operating point to be predicted in the safety domain and the boundary of the safety domain is analyzed to obtain the power margin of the converter, and the power margin is used as the governance potential of the converter, including: according to the position of the operating point to be predicted in the safety domain, measuring the distance between the operating point to be predicted and the boundary of the safety domain as the power margin of the converter, and using the power margin as the governance potential of the converter.

[0136] In actual implementation, the terminal determines the active power and reactive power of the working point to be predicted, thereby determining the position of the working point in the safety domain, measuring the distance from the working point to the boundary of the safety domain, and using the measured distance as the power margin of the converter, that is, the governance potential of the converter.

[0137] In the above embodiment, the control potential of the converter is represented by calculating the position of the working point in the safety domain and the distance from the boundary of the safety domain, so that in actual implementation, measuring the control potential of the converter is simpler and more convenient.

[0138] In another embodiment, the terminal can also verify the accuracy of the safety domain characterization. The PCC current of the working point in the safety domain is displayed. The current waveform is symmetrical, the active power output is stable, and the specified reference value can be accurately tracked; the working point in the unstable area has a three-phase current distortion of the system, and the active power oscillates or even diverges, and cannot run stably.

[0139] To explain in detail the governance potential analysis method of the converter in the present application, an embodiment is used for illustration below. The specific flow chart is shown in FIG3 . By way of example, the present application is described with a specific governance potential analysis method of the converter.

[0140] First, the terminal calculates the conversion formula between the control coordinate system and the synchronous reference system based on the relationship between the two. The specific formula is shown in (1). The various basic parameters in the system structure are measured by instruments, and the dynamic characteristics of the converter side in the synchronous coordinate system are calculated as shown in formula (2). The reference value of the current is calculated based on the active power and reactive power input to the system as shown in formula (3). The formula of the current controller is calculated based on the modulation voltage of the converter as shown in (4).

[0141] In the SRF-PLL link, the working variables are introduced to obtain the transformation relationship between the disturbance quantities of each voltage and current in different reference systems as shown in formula (5). According to formula (5), the dynamic characteristics of the converter side and the converter modulation voltage are obtained as shown in formula (6), and the small disturbance expression of the reference value of the current loop is shown in formula (7). The expression of the modulation voltage disturbance quantity of the converter after conversion from the control coordinate system to the synchronous coordinate system is shown in formula (9). In the synchronous coordinate system, the relationship between the voltage and the modulation voltage in the converter is shown in formula (10). Substituting the above formula (6) into formula (10), formula (11) is obtained. Formula (11) is simplified to obtain the disturbance expression of the PCC current as shown in formula (12). Further, the disturbance relationship (8) of the phase-locked loop is substituted into formula (12), and θ in the formula is eliminated to obtain formula (13), and then the PCC voltage disturbance quantity in the formula is eliminated. and its conjugation We get formula (14). Let , Formula (15) is obtained. Formula (15) is the small disturbance model of the grid-connected converter system.

[0142] Based on the small disturbance model of the grid-connected converter system, the terminal will consider the influence of the phase-locked loop and the grid strength, and derive the expressions between the d-axis and q-axis output current disturbance values ​​and the reference disturbance values ​​of the active power and the reactive power.

[0143] Specifically, the first expression between the current disturbance value of the d-axis output, the reference disturbance value of the active power and the reference disturbance value of the reactive power and the second expression between the current disturbance value of the q-axis output, the reference disturbance value of the active power and the reference disturbance value of the reactive power are as shown in formula (16). Formula (16) is the transfer function model of the stability of the grid-connected converter system.

[0144] The terminal will determine the active power and reactive power of the input system that need to be analyzed, that is, the operating point variables, according to the specific situation, and specify their initial values, change steps, and change ranges. For the specified operating point variables, when the stable state is reached, the device output power can be approximated to the reference power, as shown in formula (17). The grid voltage is , the voltage at the common coupling point and the grid are connected by an impedance Therefore, the topological constraint relationship between the d-axis component of the PCC point voltage and the grid voltage is shown in formula (18). Substitute the determined working point into the above topological constraint relationship to screen out the first working point set.

[0145] Substitute the working points in the first working point set into the power transfer limit formula (19) to select the second working point set that meets the formula. If the power transfer limit is not met, there is no need to analyze its stability, and let symb = 2. Where symb represents the stability analysis result of the working point.

[0146] Substitute the working points in the second working point set into the common denominator polynomial, solve its closed-loop poles, and select the working points with the largest real part in the closed-loop points located in the left half plane of the complex plane as the third working point set, and set the working point symb=1 in the working point set. Among them, the common denominator polynomial is The denominator of The denominator of is the same. The remaining working points in the second working point set are unstable, and their symb=0. Further, after screening the working points in different situations, the terminal obtains the stability result of each group of working points, that is, the symb value, divides different areas, and draws the safety domain image of the system according to the stability results of the working points. The specific safety domain image is shown in Figure 4.

[0147] The terminal determines the active power and reactive power of the working point to be predicted, thereby determining the position of the working point in the safety domain, measuring the distance from the working point to the boundary of the safety domain, and using the measured distance as the power margin of the converter, that is, the control potential of the converter. The specific analysis diagram is shown in Figure 5.

[0148] The terminal can also verify the accuracy of the safety domain characterization. The PCC current at the working point in the safety domain is displayed. The current waveform is symmetrical, the active power output is stable, and it can accurately track the specified reference value. At the working point in the unstable area, the system three-phase current is distorted, the active power oscillates or even diverges, and it cannot run stably. The specific operation results are shown in Figure 6.

[0149] In terms of analysis factors, this application not only considers capacity constraints when analyzing the power quality management potential of the converter, but also considers the impact of the control strategy on the remaining capacity. This makes the final analysis results more accurate. In terms of analysis efficiency, the safety domain-based grid-connected converter power quality management potential analysis method can obtain the maximum safe management remaining capacity of the converter under different working conditions at one time, making the prediction of the converter's management potential more rapid during actual implementation. In terms of improving management potential, the safety domain can intuitively characterize the impact of different control parameters and impedance parameters on the converter's management potential, and can maximize the auxiliary management potential of the converter during actual implementation.

[0150] It should be understood that, although the various steps in the flowcharts involved in the above-mentioned embodiments are displayed in sequence according to the indication of the arrows, these steps are not necessarily executed in sequence according to the order indicated by the arrows. Unless there is a clear explanation in this article, the execution of these steps does not have a strict order restriction, and these steps can be executed in other orders. Moreover, at least a part of the steps in the flowcharts involved in the above-mentioned embodiments can include multiple steps or multiple stages, and these steps or stages are not necessarily executed at the same time, but can be executed at different times, and the execution order of these steps or stages is not necessarily to be carried out in sequence, but can be executed in turn or alternately with other steps or at least a part of the steps or stages in other steps.

[0151] Based on the same inventive concept, the embodiment of the present application also provides a converter governance potential analysis device for implementing the converter governance potential analysis method involved above. The implementation scheme for solving the problem provided by the device is similar to the implementation scheme recorded in the above method, so the specific limitations in the embodiments of the converter governance potential analysis device provided below can refer to the limitations of the converter governance potential analysis method above, and will not be repeated here.

[0152] In an exemplary embodiment, as shown in FIG7 , a device for analyzing the governance potential of a converter is provided, comprising: a construction module, a determination module and an analysis module, wherein:

[0153] The construction module 701 is used to establish a small disturbance model of the grid-connected converter system.

[0154] The construction module 701 is also used to establish a transfer function model of the stability of the grid-connected power conversion system based on the small disturbance model of the grid-connected power conversion system.

[0155] The determination module 702 is used to traverse any set of operating points in the grid-connected converter system according to the transfer function model to determine the safety domain of the system; the set of operating points is a combination of active power preset values ​​and reactive power preset values.

[0156] The analysis module 703 is used to analyze the position of the operating point to be predicted in the safety domain and its positional relationship with the boundary of the safety domain, obtain the power margin of the converter, and use the power margin as the control potential of the converter.

[0157] In some embodiments, the above-mentioned building module is also used to model the main circuit and control part of the grid-connected converter system, introduce the operating point variable by using the dynamic characteristics of the phase-locked loop; establish a small disturbance model of the grid-connected converter system containing the operating point variable and under constant power control; the operating point variables are the active power and reactive power input to the grid-connected converter system.

[0158] In some embodiments, the above-mentioned building module is also used to determine a first expression between the current disturbance value of the direct-axis output, the reference disturbance value of the active power and the reference disturbance value of the reactive power, and a second expression between the current disturbance value of the quadrature-axis output, the reference disturbance value of the active power and the reference disturbance value of the reactive power based on the small disturbance model of the grid-connected power conversion system, combined with the phase-locked loop and the grid strength; and determine the transfer function model of the stability of the grid-connected power conversion system based on the first expression and the second expression.

[0159] In some embodiments, the above-mentioned determination module is also used to determine the working points to be analyzed; among the working points, the working points that meet the first preset condition are screened to obtain a first working point set; the first preset condition is to meet the topological constraint of the system voltage; for the first working point set, the working points that meet the second preset condition are screened to obtain a second working point set; the second preset condition is to meet the power transmission limit of the system; for the second working point set, the working points that meet the third preset condition are screened to obtain a third working point set; based on the working points in the third working point set, the safety domain of the system is drawn.

[0160] In some embodiments, the device also includes a screening module for substituting the operating points in the second operating point set into the common denominator polynomial to solve the closed-loop poles; if the pole with the largest real part in the closed-loop poles is located in the left half plane of the complex plane, the operating point is determined to be stable, and the corresponding operating point is added to the third operating point set; otherwise, the operating point is determined to be unstable; the common denominator polynomial is the denominator polynomial of the closed-loop transfer function in the transfer function, and the denominator polynomials of the closed-loop transfer functions are the same.

[0161] In some embodiments, the above-mentioned analysis module is also used to measure the distance of the operating point to be predicted from the boundary of the safety domain according to the position of the operating point to be predicted in the safety domain as the power margin of the converter, and use the power margin as the governance potential of the converter.

[0162] Each module in the above-mentioned converter governance potential analysis device can be implemented in whole or in part by software, hardware, or a combination thereof. Each of the above-mentioned modules can be embedded in or independent of a processor in a computer device in the form of hardware, or can be stored in a memory in a computer device in the form of software, so that the processor can call and execute operations corresponding to each of the above modules.

[0163] In an exemplary embodiment, a computer device is provided, which may be a terminal, and its internal structure diagram may be shown in FIG8. The computer device includes a processor, a memory, an input / output interface, a communication interface, a display unit, and an input device. The processor, the memory, and the input / output interface are connected via a system bus, and the communication interface, the display unit, and the input device are connected to the system bus via the input / output interface. The processor of the computer device is used to provide computing and control capabilities. The memory of the computer device includes a non-volatile storage medium and an internal memory. The non-volatile storage medium stores an operating system and a computer program. The internal memory provides an environment for the operation of the operating system and the computer program in the non-volatile storage medium. The input / output interface of the computer device is used to exchange information between the processor and an external device. The communication interface of the computer device is used to communicate with an external terminal in a wired or wireless manner, and the wireless manner may be implemented through WIFI, a mobile cellular network, near field communication (NFC) or other technologies. When the computer program is executed by the processor, a method for analyzing the governance potential of a converter is implemented. The display unit of the computer device is used to form a visually visible picture, which may be a display screen, a projection device, or a virtual reality imaging device. The display screen can be a liquid crystal display screen or an electronic ink display screen, and the input device of the computer device can be a touch layer covering the display screen, or a button, trackball or touchpad set on the computer device shell, or an external keyboard, touchpad or mouse.

[0164] Those skilled in the art will understand that the structure shown in FIG. 8 is merely a block diagram of a partial structure related to the solution of the present application, and does not constitute a limitation on the computer device to which the solution of the present application is applied. The specific computer device may include more or fewer components than shown in the figure, or combine certain components, or have a different arrangement of components.

[0165] In an exemplary embodiment, a computer device is provided, including a memory and a processor, wherein a computer program is stored in the memory, and when the processor executes the computer program, the following steps are implemented:

[0166] Establish a small disturbance model of the grid-connected converter system;

[0167] Based on the small disturbance model of the grid-connected power conversion system, a transfer function model of the stability of the grid-connected power conversion system is established;

[0168] According to the transfer function model, traverse any set of operating points in the grid-connected converter system to determine the safety domain of the system; the set of operating points is a combination of active power preset values ​​and reactive power preset values;

[0169] The position of the working point to be predicted in the safety domain and its positional relationship with the boundary of the safety domain are analyzed to obtain the power margin of the converter, and the power margin is used as the control potential of the converter.

[0170] In one embodiment, a computer readable storage medium is provided, on which a computer program is stored, and when the computer program is executed by a processor, the following steps are implemented:

[0171] Establish a small disturbance model of grid-connected converter system;

[0172] Based on the small disturbance model of the grid-connected power conversion system, a transfer function model of the stability of the grid-connected power conversion system is established;

[0173] According to the transfer function model, traverse any set of operating points in the grid-connected converter system to determine the safety domain of the system; the set of operating points is a combination of active power preset values ​​and reactive power preset values;

[0174] The position of the working point to be predicted in the safety domain and its positional relationship with the boundary of the safety domain are analyzed to obtain the power margin of the converter, and the power margin is used as the control potential of the converter.

[0175] In one embodiment, a computer program product is provided, comprising a computer program, which, when executed by a processor, implements the following steps:

[0176] Establish a small disturbance model of grid-connected converter system;

[0177] Based on the small disturbance model of the grid-connected power conversion system, a transfer function model of the stability of the grid-connected power conversion system is established;

[0178] According to the transfer function model, traverse any set of operating points in the grid-connected converter system to determine the safety domain of the system; the set of operating points is a combination of active power preset values ​​and reactive power preset values;

[0179] The position of the working point to be predicted in the safety domain and its positional relationship with the boundary of the safety domain are analyzed to obtain the power margin of the converter, and the power margin is used as the control potential of the converter.

[0180] It should be noted that the user information (including but not limited to user device information, user personal information, etc.) and data (including but not limited to data used for analysis, stored data, displayed data, etc.) involved in this application are all information and data authorized by the user or fully authorized by all parties, and the collection, use and processing of relevant data must comply with relevant regulations.

[0181] A person of ordinary skill in the art can understand that all or part of the processes in the above-mentioned embodiment method can be completed by instructing the relevant hardware through a computer program, and the computer program can be stored in a non-volatile computer-readable storage medium. When the computer program is executed, it can include the processes of the embodiments of the above-mentioned methods. Among them, any reference to the memory, database or other medium used in the embodiments provided in the present application can include at least one of non-volatile memory and volatile memory. Non-volatile memory can include read-only memory (ROM), magnetic tape, floppy disk, flash memory, optical memory, high-density embedded non-volatile memory, resistive random access memory (ReRAM), magnetic random access memory (MRAM), ferroelectric random access memory (FRAM), phase change memory (PCM), graphene memory, etc. Volatile memory can include random access memory (RAM) or external cache memory, etc. As an illustration and not limitation, RAM can be in various forms, such as static random access memory (SRAM) or dynamic random access memory (DRAM). The database involved in each embodiment provided in this application may include at least one of a relational database and a non-relational database. Non-relational databases may include distributed databases based on blockchains, etc., but are not limited to this. The processor involved in each embodiment provided in this application may be a general-purpose processor, a central processing unit, a graphics processor, a digital signal processor, a programmable logic device, a data processing logic device based on quantum computing, an artificial intelligence (AI) processor, etc., but are not limited to this.

[0182] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this application.

[0183] The above-described embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the present application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the attached claims.

Claims

1. A method for analyzing the governance potential of a converter, characterized in that: The method comprises: Establish a small disturbance model of the grid-connected converter system; Based on the small disturbance model of the grid-connected power conversion system, a transfer function model of the stability of the grid-connected power conversion system is established; According to the transfer function model, traverse any set of operating points in the grid-connected converter system to determine the safety domain of the system; the set of operating points is a combination of active power preset values ​​and reactive power preset values; The position of the working point to be predicted in the safety domain and its positional relationship with the boundary of the safety domain are analyzed to obtain the power margin of the converter, and the power margin is used as the control potential of the converter.

2. The method according to claim 1, characterized in that The establishing of a small disturbance model of a grid-connected converter system comprises: Modeling is done based on the main circuit and control part of the grid-connected converter system, and the operating point variables are introduced using the dynamic characteristics of the phase-locked loop; A small disturbance model of a grid-connected converter system including the operating point variables and under constant power control is established; the operating point variables are active power and reactive power input to the grid-connected converter system.

3. The method according to claim 1, characterized in that The transfer function model of the stability of the grid-connected converter system is established based on the small disturbance model of the grid-connected converter system, including: Based on the small disturbance model of the grid-connected power conversion system, in combination with the phase-locked loop and the grid strength, a first expression between the current disturbance value of the direct-axis output, the reference disturbance value of the active power and the reference disturbance value of the reactive power, and a second expression between the current disturbance value of the quadrature-axis output, the reference disturbance value of the active power and the reference disturbance value of the reactive power are determined; According to the first expression and the second expression, a transfer function model of the stability of the grid-connected converter system is determined.

4. The method according to claim 1, characterized in that: The step of traversing any set of working points of the grid-connected converter system according to the transfer function model to determine the safety domain of the system includes: Determine the working point to be analyzed; Among the working points, the working points satisfying a first preset condition are screened to obtain a first working point set; the first preset condition is satisfying a topological constraint of a system voltage; For the first working point set, screening working points that meet a second preset condition to obtain a second working point set; the second preset condition is to meet a power transmission limit of the system; For the second working point set, screening working points that meet a third preset condition to obtain a third working point set; A safety domain of the system is drawn according to the working points in the third working point set.

5. The method according to claim 4, characterized in that The step of screening the working points satisfying a third preset condition for the second working point set to obtain a third working point set includes: Substituting the operating points in the second operating point set into the common denominator polynomial to solve for the closed-loop poles; If the pole with the largest real part in the closed-loop pole is located in the left half plane of the complex plane, the operating point is determined to be stable, and the corresponding operating point is added to the third operating point set; otherwise, the operating point is determined to be unstable; the common denominator polynomial is the denominator polynomial of the closed-loop transfer function in the transfer function, and the denominator polynomials of the closed-loop transfer functions are the same.

6. The method according to claim 1, characterized in that The analyzing the positional relationship between the position of the working point to be predicted in the safety domain and the boundary of the safety domain to obtain the power margin of the converter, and using the power margin as the control potential of the converter, includes: According to the position of the working point to be predicted in the safety domain, the distance of the working point to be predicted from the boundary of the safety domain is measured as the power margin of the converter, and the power margin is used as the control potential of the converter.

7. A device for analyzing the governance potential of a converter, characterized in that: The device comprises: Building module for building small disturbance model of grid-connected converter system; The building module is further used to establish a transfer function model of the stability of the grid-connected power conversion system based on the small disturbance model of the grid-connected power conversion system; A determination module, used to traverse any set of operating points in the grid-connected converter system according to the transfer function model to determine the safety domain of the system; the set of operating points is a combination of active power preset values ​​and reactive power preset values; The analysis module is used to analyze the position of the working point to be predicted in the safety domain and the positional relationship between the working point to be predicted and the boundary of the safety domain, so as to obtain the power margin of the converter and use the power margin as the control potential of the converter.

8. A computer device comprising a memory and a processor, wherein the memory stores a computer program, wherein: When the processor executes the computer program, the steps of the method according to any one of claims 1 to 6 are implemented.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 6 are implemented.

10. A computer program product, comprising a computer program, characterized in that When the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 6 are implemented.

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