A design system and method for the main circuit and parameters of a flexible DC transmission project

Abstract

The present invention provides a design system and method for the main circuit and parameters of a flexible DC transmission project, including: a human-machine interface layer, an integrated tool layer, and a data management layer; wherein the human-machine interface layer is used to: determine the design process of the main circuit and parameters corresponding to each flexible DC transmission project and the input data based on the form of human-computer interaction, and display the results; the data management layer is used to: store the relevant information of the main circuit and parameters and the template information used in the design process; the integrated tool layer is used to: integrate the tools required for the design process, and perform calculations using the input data provided by the human-machine interface layer and the templates provided by the data management layer. The present invention integrates the single-line diagram design, system parameter calculation, equipment parameter calculation, and equipment inventory generation together, establishes an automatic data transfer relationship, avoids the problems of repeated parameter input, easy errors in manual calculation, and low efficiency, and greatly improves the efficiency and accuracy of the main wiring and main circuit parameter design.

Description

Technical Field

[0001] The present invention belongs to the field of flexible DC transmission engineering, and particularly relates to a design system and method for the main circuit and parameters of a flexible DC transmission project. Background Art

[0002] In the design of a flexible DC transmission system, the design of the main wiring and main circuit parameters is the prerequisite for a series of works such as insulation coordination design, control and protection design, and writing of equipment technical specifications. It is the most fundamental and complicated. The accuracy and efficiency of its design results directly affect the overall performance of the flexible DC system. A slight mistake will lead to serious mistakes in subsequent design and equipment manufacturing.

[0003] Patent ZL201210524468.1 discloses a grounding device for a modular multi-level flexible DC transmission system and its design method, which realizes the grounding of the modular multi-level flexible DC transmission system through a grounding transformer device.

[0004] Patent ZL201210524649.4 discloses a parameter design method for a smoothing reactor used in flexible DC transmission, and proposes a design method for a smoothing reactor that comprehensively limits the rising rate of fault current, prevents steep wave shock waves on the DC side from entering the valve hall, and smooths the DC current ripple.

[0005] Patent ZL201310601081.6 proposes a method for increasing the capacity of a flexible DC transmission system, and proposes to add a full-bridge sub-module capable of generating a negative voltage in the converter bridge arm to balance the DC output voltage of the converter and adjust the AC output voltage of the converter, thereby increasing the transmission capacity of the converter.

[0006] Patent ZL201210363393.3 proposes a regulation method and system for the on-load tap-changer of a flexible DC transmission connection transformer, which ensures that the ratio of the valve-side voltage to the DC voltage of the connection transformer remains unchanged under the condition of power grid voltage fluctuation, and maximally utilizes the reactive power output capacity of the converter.

[0007] The above-mentioned invention patents involve different aspects of the main circuit parameters of the flexible DC system, but the methods are scattered and do not form an integrated system; the main wiring is completely manually drawn, and the component symbols are not standardized; the parameter calculation depends on manual calculation. The entire design process has low efficiency, the calculation results of different designers are prone to deviation, and the output quality is uncontrollable. The repeated checking work generates a great deal of time cost and labor cost. Summary of the Invention

[0008] In view of the above deficiencies in the prior art, the present invention provides a design system for the main circuit and parameters of a flexible DC transmission project, including: a human-machine interface layer, an integrated tool layer, and a data management layer;

[0009] The human - machine interface layer is used for: determining the design process and input data of the main circuit and parameters corresponding to each flexible DC transmission project based on the form of human - machine interaction, and displaying the results;

[0010] The data management layer is used for: storing the relevant information of the main circuit and parameters and the template information used in the design process;

[0011] The integrated tool layer is used for: integrating the tools required for the design process, and performing calculations using the input data provided by the human - machine interface layer and the templates provided by the data management layer.

[0012] Preferably, the design of the main circuit and parameters corresponding to each flexible DC transmission project includes: engineering single - line diagram design, engineering main system parameter calculation, engineering key equipment parameter calculation, and equipment list generation.

[0013] Preferably, the human - machine interface layer includes:

[0014] The wiring diagram design interface, which is a human - machine interaction interface for supporting data input and display related to the engineering single - line diagram design;

[0015] The main system calculation interface, which is a human - machine interaction interface for supporting data input and display of the engineering main system parameter calculation;

[0016] The equipment parameter calculation interface, which is a human - machine interaction interface for supporting data input and display of the engineering key equipment parameter calculation;

[0017] The equipment list interface, which is a human - machine interaction interface for displaying the data generated by the equipment list generation.

[0018] Preferably, the data management layer includes:

[0019] The component symbol library, which is used for storing the component information related to the engineering single - line diagram design;

[0020] The wiring diagram selection logic, which is used for storing the selection principles of each partition subsystem and equipment, including all possible equipment configurations in each partition and whether there is a mutually exclusive relationship between equipment configurations;

[0021] The system calculation template, which is a MathCAD file for calculating system parameters such as system capacity and transformer valve - side rated voltage threshold. Its input parameters are obtained through the system calculation interface. After being calculated by this template, the calculation results are returned to the system parameter calculation interface and passed to other equipment calculation templates that require this calculation result;

[0022] The system calculation parameters, which store the input and output parameters of the system calculation;

[0023] The device calculation template, which is a MathCAD file for calculating device parameters. Its input parameters are obtained through the device parameter calculation interface. After being calculated by this template, the calculation results are returned to the device parameter calculation interface.

[0024] Device calculation parameters, which store the input and output parameters of device calculations.

[0025] The inventory template is used to store the device inventory template file, which contains at least the header information of the device inventory table.

[0026] Preferably, the system calculation template and the device calculation template are specifically used for: combining according to power transmission and grid interconnection and engineering topology to obtain the following calculation templates:

[0027] Symmetrical monopole power transmission calculation template, symmetrical monopole grid interconnection calculation template, symmetrical bipolar power transmission calculation template, and symmetrical bipolar grid interconnection calculation template.

[0028] Preferably, the integrated tool layer includes: AutoCAD module, Mathcad module, Office module, and DXperience module;

[0029] The AutoCAD module is used for: receiving the information input by the wiring diagram design interface and the component information stored in the component symbol library to generate a single-line diagram;

[0030] The Mathcad module is used for: calculating the relevant main system parameters and device parameters of the project based on the input data obtained from the main system calculation interface and the device calculation interface in combination with the calculation methods stored in the system calculation template and the device calculation template, and feeding back the calculation results to the main system calculation interface and the device calculation interface for display;

[0031] The Office module includes: single-line diagram statistical table, option list, Chinese and English inventory template data, and parameter output template data.

[0032] Preferably, the key devices include converters, transformers, arm reactors, smoothing reactors, starting resistors, and transformer neutral point resistors.

[0033] Based on the same inventive concept, the present invention also provides a design method for the main circuit and parameters of a flexible DC transmission project, including:

[0034] Determining the corresponding design process of the main circuit and parameters based on different engineering requirements;

[0035] Selecting the relevant information and template information of the main circuit and parameters used in the design process from the data management layer;

[0036] Determine the input data of the main circuit and parameters in the form of human-computer interaction;

[0037] Based on the input data and template information, use the tools stored in the integrated tool layer for calculation and display.

[0038] Preferably, the design process of determining the corresponding main circuit and parameters according to different engineering requirements includes: engineering single-line diagram design, engineering main system parameter calculation, engineering key equipment parameter calculation, and equipment list generation.

[0039] Preferably, the engineering single-line diagram design includes:

[0040] Select the engineering topology form through the human-machine interface layer;

[0041] Partition the flexible DC transmission system through the human-machine interface layer;

[0042] Based on the selected engineering topology form and partition, select the device element symbols used in various engineering situations from the component symbol library;

[0043] Generate an engineering single-line diagram based on the selected device element symbols and engineering topology structure.

[0044] Preferably, the engineering main system parameter calculation includes:

[0045] Based on the calculation templates pre-divided according to the calculation situation, obtain the input data corresponding to the current calculation information from the human-computer interaction interface, and the input data includes: input conditions and parameters;

[0046] Call the calculation template to obtain the key parameter values in the current calculation situation, and display the key parameter values based on the human-machine interface;

[0047] Among them, the key parameter values include: the rated capacity, rated active power, rated valve-side voltage of the transformer, and per-unit value of the arm reactor at both ends of the project.

[0048] Preferably, the division of the calculation template includes:

[0049] Combine the calculation situation and engineering topology to obtain multiple calculation templates;

[0050] Among them, the calculation situation includes power transmission and grid interconnection; the calculation templates include: symmetrical monopolar power transmission calculation template, symmetrical monopolar grid interconnection calculation template, symmetrical bipolar power transmission calculation template, and symmetrical bipolar grid interconnection calculation template.

[0051] Preferably, the engineering key equipment parameter calculation includes:

[0052] Generate a list of key equipment according to the design result of the single-line diagram design module and display it on the human-machine interface;

[0053] Perform design calculations on the parameters of key equipment one by one according to the list of key equipment;

[0054] After equipment calculation, generate equipment parameters;

[0055] Return the equipment parameters to the human-machine interface for display, and at the same time form an equipment parameter document for storage with the parameter information of all equipment;

[0056] Among them, the key equipment includes converters, transformers, arm reactors, smoothing reactors, starting resistors, and transformer neutral point resistors.

[0057] Preferably, the generation of the equipment inventory includes:

[0058] Statistically calculate the parameters and quantities of all equipment according to equipment zoning or equipment type to form a primary equipment inventory;

[0059] At the same time, write the calculated equipment parameters into the single-line diagram of the equipment.

[0060] The beneficial effects of the present invention are as follows:

[0061] A design system and method for the main circuit and parameters of a flexible DC transmission project provided by the present invention includes: a human-machine interface layer, an integrated tool layer, and a data management layer; the human-machine interface layer is used for: determining the design process and input data of the main circuit and parameters corresponding to each flexible DC transmission project based on the form of human-machine interaction, and displaying the results; the data management layer is used for: storing the relevant information of the main circuit and parameters and the template information used in the design process; the integrated tool layer is used for: integrating the tools required for the design process, and performing calculations using the input data provided by the human-machine interface layer and the template provided by the data management layer. In the present invention, the single-line diagram design, system parameter calculation, equipment parameter calculation, and equipment inventory generation of the flexible DC transmission project are integrated together, an automatic data transfer relationship is established between each module, and the calculation method is standardized to form a calculation template file, avoiding the problems of repeated input of input parameters, easy errors and low efficiency in manual calculation, and greatly improving the efficiency and accuracy of the main wiring and main circuit parameter design. Description of the Drawings

[0062] Figure 1 is the architecture diagram of a design system for the main circuit and parameters of a flexible DC transmission project described in the present invention;

[0063] Figure 2 is the human-machine interface display page of the single-pole power transmission template of a design system for the main circuit and parameters of a flexible DC transmission project described in the present invention;

[0064] Figure 3 It is the human - machine interface display page of the transformer parameters of a design system for the main circuit and parameters of a flexible DC transmission project described in the present invention;

[0065] Figure 4 It is the flowchart of the design method for the main circuit and parameters of a flexible DC transmission project described in the present invention. Detailed implementation manners

[0066] The technical solution of the present invention will be further described below, but the claimed scope is not limited thereto.

[0067] Embodiment 1

[0068] As Figure 1 shown, the design system for the main circuit and parameters of a flexible DC transmission project includes a human - machine interface layer, an integrated tool layer, and a data management layer;

[0069] The human - machine interface layer, as Figure 2 and Figure 3 shown, conducts data interaction with designers during the design process, including the selection of the topology type of the flexible DC transmission project, equipment configuration, input of the conditions and parameters required for calculation, and output of the single - line diagram and calculation results; here, the design of the main circuit and parameters corresponding to each flexible DC transmission project includes: single - line diagram design of the project, calculation of the main system parameters of the project, calculation of the key equipment parameters of the project, and generation of the equipment inventory.

[0070] Specifically, the human - machine interface layer includes:

[0071] The wiring diagram design interface, which is a human - machine interaction interface for supporting data input and display related to the single - line diagram design of the project;

[0072] The main system calculation interface, which is a human - machine interaction interface for supporting data input and display for the calculation of the main system parameters of the project;

[0073] The equipment parameter calculation interface, which is a human - machine interaction interface for supporting data input and display for the calculation of the key equipment parameters of the project;

[0074] The equipment inventory interface, which is a human - machine interaction interface for displaying the data generated for the equipment inventory.

[0075] The integrated tool layer integrates AutoCAD, Mathcad, and Office software. AutoCAD receives the topology type and device configuration input from the device configuration interface and automatically generates a single-line diagram. After the device calculation is completed, it receives the device parameters and displays them in the single-line diagram. Mathcad calculation templates receive the input data from the system calculation and device calculation interfaces, and after calculation, return the calculation results to the system calculation and device calculation interfaces. Office stores files such as single-line diagram statistical tables, option lists, Chinese and English catalog templates, and parameter output templates.

[0076] Among them, the AutoCAD module is used to: receive the information input from the wiring diagram design interface and the component information stored in the component symbol library to generate a single-line diagram;

[0077] The Mathcad module is used to: calculate the relevant engineering main system parameters and device parameters based on the input data obtained from the main system calculation interface and the device calculation interface in combination with the calculation methods stored in the system calculation template and the device calculation template, and feedback the calculation results to the main system calculation interface and the device calculation interface for display;

[0078] The Office module includes: single-line diagram statistical tables, option lists, Chinese and English catalog template data, and parameter output template data.

[0079] The data management layer stores a component symbol library, wiring diagram statistical tables, wiring diagram selection logic, system calculation templates, device calculation templates, parameter output templates, and Chinese and English catalog template data.

[0080] Specifically, the data management layer includes:

[0081] A component symbol library for storing component information related to the engineering single-line diagram design;

[0082] Wiring diagram selection logic for storing the selection principles of each partition subsystem and device, including all possible device configurations in each partition and whether there are mutually exclusive relationships between device configurations;

[0083] A system calculation template, a MathCAD file for calculating system parameters such as system capacity and transformer valve-side rated voltage threshold. Its input parameters are obtained through the system calculation interface. After calculation by this template, the calculation results are returned to the system parameter calculation interface and passed to other device calculation templates that require this calculation result;

[0084] System calculation parameters for storing the input and output parameters of system calculation;

[0085] The device calculation template, i.e., the MathCAD file for device parameter calculation, obtains its input parameters through the device parameter calculation interface. After being calculated by this template, the calculation results are returned to the device parameter calculation interface;

[0086] Device calculation parameters, which store the input and output parameters of device calculation;

[0087] The inventory template is used to store the device inventory template file, which contains at least the header information of the device inventory table.

[0088] The system calculation template and the device calculation template are specifically used for: combining according to power transmission and grid interconnection and engineering topology to obtain the following calculation templates:

[0089] Symmetrical monopolar power transmission calculation template, symmetrical monopolar grid interconnection calculation template, symmetrical bipolar power transmission calculation template, and symmetrical bipolar grid interconnection calculation template. The key devices in the present invention include converters, transformers, arm reactors, smoothing reactors, starting resistors, and transformer neutral point resistors.

[0090] Embodiment 2

[0091] Based on the same inventive concept, the present invention also provides a design method for the main circuit and parameters of a flexible DC project, as Figure 4 shown, including the following steps:

[0092] S1. Determine the corresponding design process of the main circuit and parameters based on different engineering requirements;

[0093] S2. Select the relevant information and template information of the main circuit and parameters used in the design process from the data management layer;

[0094] S3. Determine the input data of the main circuit and parameters in a human-computer interaction manner;

[0095] S4. Calculate based on the input data and template information using the tools stored in the integrated tool layer, and display the results.

[0096] In this embodiment, determining the corresponding design process of the main circuit and parameters according to different engineering requirements includes: engineering single-line diagram design, engineering main system parameter calculation, engineering key device parameter calculation, and device inventory generation.

[0097] The specific design process is as follows:

[0098] 1) Engineering single-line diagram design

[0099] ① First, select the engineering topology through the human-computer interface layer. The optional forms are: symmetrical monopolar, double symmetrical monopolar, and symmetrical bipolar;

[0100] ②Then, partition the flexible DC transmission system into three major areas: the AC area (Area A), the converter area (Area B), and the DC area (Area C). The AC area (Area A) is further divided into the transformer grid side (Area A1), the transformer area (Area A2), the transformer valve side (Area A3), and the transformer valve side bridge arm AC equipment area (Area A4);

[0101] ③Taking the converter area (Area B) as the center, select the equipment configuration for the AC side and the DC side; the equipment symbol library in the data management layer stores all the equipment element symbols that may be used in different engineering situations according to the partition. The design system automatically generates the engineering single-line diagram according to the designer's configuration;

[0102] 2) Calculation of the main system parameters of the project

[0103] The calculation of the main system parameters includes two cases: power transmission and grid interconnection;

[0104] In the case of power transmission, only one-way power transmission is required. The known condition is the active power at the sending end, and the DC voltage point is set at the DC port of the receiving-end converter station. When calculating the rated capacity of the converter station in this case, it is carried out according to the principle of minimum loss, so as to obtain the maximum capacity in all working conditions at the receiving end as the rated capacity;

[0105] In the case of grid interconnection, two-way power transmission is required. The known condition is the active power at the inverter side, and the DC voltage point is set at the DC port of the rectifier side. When calculating the rated capacity of the converter station in this case, it is carried out according to the principle of maximum loss, so as to obtain the maximum capacity in all working conditions at the rectifier side as the rated capacity;

[0106] Combining power transmission and grid interconnection with the project topology includes four cases, namely symmetric monopolar power transmission, symmetric monopolar grid interconnection, symmetric bipolar power transmission, and symmetric bipolar grid interconnection; sort out the calculation methods for the above four cases to form four independent calculation templates;

[0107] The input and output parameters of each calculation template correspond to the calculation interface; input the input conditions and parameters required for the calculation from the calculation interface, including the nominal voltage of the AC system, the frequency of the AC system, the losses of the converter station, the reactive power requirements, the DC line parameters, and whether to use third-harmonic injection modulation. Through the calculation of the calculation template, key parameters such as the rated capacity, rated active power, rated voltage on the transformer valve side, and per-unit value of the arm reactor at the two ends of the project can be obtained in any case, and the calculation results are output to the man-machine interface;

[0108] 3) Calculation of the parameters of key equipment for the project

[0109] The calculation module for the parameters of key equipment in the project dynamically generates a list of key equipment according to the design results of the single-line diagram design module and displays it on the man-machine interface; carry out the design calculation of the parameters of key equipment one by one according to the list of key equipment;

[0110] The input parameters of each key device come from two parts. One is the parameters transferred from the main system parameter calculation, and the other is the manual input parameters of the designer received by the device calculation human-machine interface. After these two parts of parameters are input and calculated and processed by the integration tool layer and the data management layer, the output data is transferred to the device human-machine interface.

[0111] After the device calculation, the device parameters in the interface are generated, and the parameters of all devices are automatically output to a document uniformly to form a total device parameter document.

[0112] 4) Generation of equipment inventory

[0113] In this functional module, the parameters and quantities of all devices are counted according to the equipment partition or according to the equipment type to form a primary equipment inventory.

[0114] In addition, the calculated equipment parameters can be written back to the single-line diagram of the equipment.

[0115] Furthermore, the key devices include converters, transformers, arm reactors, smoothing reactors, starting resistors, and transformer neutral point resistors.

Claims

1. A design system for the main circuit and parameters of a flexible DC transmission project, characterized in that It includes: a human - machine interface layer, an integration tool layer, and a data management layer; The human - machine interface layer is used for: determining the design process of the main circuit and parameters corresponding to each flexible DC transmission project and the input data based on the form of human - machine interaction, and displaying the results; The data management layer is used for: storing the relevant information of the main circuit and parameters and the template information used in the design process; The integration tool layer is used for: integrating the tools required for the design process, and performing calculations using the input data provided by the human - machine interface layer and the templates provided by the data management layer; The design of the main circuit and parameters corresponding to each flexible DC transmission project includes: engineering single - line diagram design, engineering main system parameter calculation, engineering key equipment parameter calculation, and equipment list generation; The human - machine interface layer includes: a wiring diagram design interface, a human - machine interaction interface for supporting data input and display related to the engineering single - line diagram design; a main system calculation interface, a human - machine interaction interface for supporting data input and display of the engineering main system parameter calculation; an equipment parameter calculation interface, a human - machine interaction interface for supporting data input and display of the engineering key equipment parameter calculation; an equipment list interface, a human - machine interaction interface for displaying the data generated by the equipment list generation; The data management layer includes: a component symbol library, used for storing the component information related to the engineering single - line diagram design; a wiring diagram selection logic, used for storing the selection principles of each partition subsystem and equipment, including all possible equipment configurations in each partition and whether there is a mutually exclusive relationship between equipment configurations; a system calculation template, a MathCAD file for calculating system parameters such as system capacity and transformer valve - side rated voltage threshold. Its input parameters are obtained through the system calculation interface. After being calculated by this template, the calculation results are returned to the system calculation interface and passed to other equipment calculation templates that require this calculation result; system calculation parameters, storing the input and output parameters of system calculation; an equipment calculation template, that is, a MathCAD file for performing equipment parameter calculation. Its input parameters are obtained through the equipment parameter calculation interface. After being calculated by this template, the calculation results are returned to the equipment parameter calculation interface; equipment calculation parameters, storing the input and output parameters of equipment calculation; a list template, used for storing the equipment list template file, which at least contains the header information of the equipment list table; The integration tool layer includes: an AutoCAD module, a Mathcad module, an Office module, and a DXperience module; The AutoCAD module is used for: receiving the information input by the wiring diagram design interface and the component information stored in the component symbol library to generate a single - line diagram; The Mathcad module is used for: calculating the relevant engineering main system parameters and equipment parameters based on the input data obtained from the main system calculation interface and the equipment calculation interface, combined with the calculation methods stored in the system calculation template and the equipment calculation template, and feeding back the calculation results to the main system calculation interface and the equipment calculation interface for display; The Office module includes: single-line diagram statistical table, option list, Chinese-English inventory template data, and parameter output template data.

2. The system according to claim 1, wherein The system calculation template and the equipment calculation template are specifically used for: combining power transmission and grid interconnection with engineering topology to obtain the following calculation templates: Symmetrical monopolar power transmission calculation template, symmetrical monopolar grid interconnection calculation template, symmetrical bipolar power transmission calculation template, and symmetrical bipolar grid interconnection calculation template.

3. The system according to claim 1, characterized in that, The key equipment includes converters, transformers, arm reactors, smoothing reactors, starting resistors, and transformer neutral point resistors.

4. A design method for the main circuit and parameters of a flexible DC transmission project, characterized in that It includes: The design process of determining the corresponding main circuit and parameters based on different engineering requirements; Selecting relevant information and template information of the main circuit and parameters used in the design process from the data management layer; Determining the input data of the main circuit and parameters in the form of human-computer interaction; Calculating based on the input data and template information using the tools stored in the integrated tool layer, and displaying the results; The design process of determining the corresponding main circuit and parameters according to different engineering requirements includes: engineering single-line diagram design, engineering main system parameter calculation, engineering key equipment parameter calculation, and equipment inventory generation; The engineering single-line diagram design includes: Selecting the engineering topology form through the human-machine interface layer; Partitioning the flexible DC transmission system through the human-machine interface layer; Selecting the device component symbols used in various engineering situations from the component symbol library based on the selected engineering topology form and partition; Generating an engineering single-line diagram based on the selected device component symbols and engineering topology structure; The engineering main system parameter calculation includes: Based on the calculation templates pre-divided according to the calculation situation, obtaining the input data corresponding to the current calculation information from the human-computer interaction interface, where the input data includes input conditions and parameters; Invoking the calculation template to obtain the key parameter values in the current calculation situation, and displaying the key parameter values based on the human-machine interface; Among them, the key parameter values include: the rated capacity, rated active power, rated valve-side voltage of the transformer, and per-unit value of the arm reactor at both ends of the project; The engineering key equipment parameter calculation includes: Generating a key equipment list according to the design results of the single-line diagram design module and displaying it on the human-machine interface; Carrying out key equipment parameter design calculations one by one according to the key equipment list; After equipment calculation, generating equipment parameters; Returning the equipment parameters to the human-machine interface for display, and at the same time forming an equipment parameter document to store the parameter information of all equipment; Among them, the key equipment includes converters, transformers, arm reactors, smoothing reactors, starting resistors, and transformer neutral point resistors; The equipment inventory generation includes: Counting the parameters and quantities of all equipment according to equipment partitions or equipment types to form a primary equipment inventory; At the same time, writing the calculated equipment parameters into the equipment single-line diagram.

5. The design method according to claim 4, characterized in that The division of the calculation template includes: Combining the calculation situation with the engineering topology to obtain multiple calculation templates; Among them, the calculation scenarios include power transmission and grid interconnection; the calculation templates include: symmetric monopole power transmission calculation template, symmetric monopole grid interconnection calculation template, symmetric bipolar power transmission calculation template, and symmetric bipolar grid interconnection calculation template.

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