Method and system for electromechanical transient simulation of extra-high voltage flexible topology direct current transmission system

Abstract

The invention discloses a method and a system for electromechanical transient simulation of an extra-high voltage flexible topology direct current transmission system, and belongs to the technical field of electromechanical transient simulation. The method comprises the following steps: acquiring simulation data for the extra-high voltage flexible topology direct current power transmission system, and constructing a converter simulation model for each converter in the extra-high voltage flexible topology direct current power transmission system by using a preset modeling method based on the simulation data; the simulation models are combined into a flexible topology direct current pole electromechanical transient model, and the flexible topology direct current pole electromechanical transient model is combined into a direct current power transmission system model through a lumped parameter dynamic direct current network; and performing electromechanical transient simulation calculation on the extra-high voltage flexible topology direct current power transmission system by using a preset simulation calculation method based on the direct current power transmission system model. According to the method, accurate simulation can be carried out on the direct-current project, and important reference values are provided for planning research, scheduling operation analysis, stability analysis and the like of a direct-current power transmission system access system with more complex topology possibly occurring.

Description

Technical Field

[0001] The present invention relates to the technical field of electromechanical transient simulation, and more particularly to a method for electromechanical transient simulation of an ultra-high voltage flexible topology direct current transmission system. Background Art

[0002] With the rapid and sustained development of China's economy, the State Grid Corporation of China has built a large-scale, complex power transmission system featuring ultra-high voltage (UHV), AC / DC hybrid transmission, and localized multiple DC feeds. On the one hand, ultra-high voltage DC (UHVDC) transmission technology based on line commutated converters (LCCs) has, after years of development, demonstrated advantages such as low losses and low construction costs, assuming the role of large-capacity, long-distance power transmission in my country's energy landscape. On the other hand, flexible direct current (HVDC) technology, a new generation of voltage source converter-based HVDC (VSC-HVDC) transmission technology with fully controlled devices, is an effective means of achieving high controllability and flexibility in transmission and distribution systems. Since the 1990s, it has developed rapidly. In my country, HVDC transmission projects based on modular multilevel converters (MMC-HVDC) have been widely deployed. In recent years, representative ultra-high voltage LCC-HVDC and various types of VSC-HVDC projects have been completed. The planning, construction and commissioning of DC projects and power grids with higher voltage levels, larger capacities and more diverse applications have resulted in power grids exhibiting increasingly strong AC / DC mutual coupling and complex and changeable transient processes.

[0003] In order to take advantage of the combined advantages of LCC and VSC, China's DC transmission projects have developed complex topologies. For example, the Jiansu (Baihetan-Jiangsu) DC adopts a hybrid cascade multi-terminal flexible DC solution, and the single-pole structure Figure 1 shown.

[0004] Figure 1 This is a schematic diagram of a single-pole structure for a flexible topology DC transmission system. The left side of this structure represents the sending end. The sending AC transmission system is simulated as a single transmission system. The AC transmission system power is connected to two LCCs via a converter transformer. The two LCCs are connected in series to the DC line, and after passing through the DC circuit, they reach the inverter-side converter. The inverter-side converter consists of the LCCs and three VSCs: VSC1, VSC2, and VSC3. VSC1, VSC2, and VSC3 are connected in parallel and then in series with the LCCs. VSC1, VSC2, VSC3, and LCCs are connected to the receiving AC transmission system, which is replaced by a single transmission system.

[0005] Although the monopole architecture is complex, it has obvious advantages, including but not limited to:

[0006] (1) Solve the problem of commutation failure:

[0007] Traditional LCCs are prone to commutation failures during AC system faults, impacting system stability. VSCs, on the other hand, are independent of AC system voltage and can provide dynamic reactive power support during faults, reducing the probability of LCC commutation failures and improving overall system stability.

[0008] (2) DC fault ride-through capability:

[0009] The hybrid cascaded DC system, through the unidirectional conductivity of LCC and the rapid recovery capability of VSC, can quickly clear the fault current and resume operation when a DC line fault occurs, avoiding the vulnerability of traditional flexible DC transmission systems under faults.

[0010] (3) Engineering economics:

[0011] The hybrid form of LCC and VSC can significantly reduce project costs and losses, while reducing floor space, taking into account both economic and technical performance.

[0012] With the development of China's direct current transmission (DC) system, DC transmission systems with more complex topologies are likely to emerge. While mature electromechanical transient simulation methods exist for DC transmission systems with a single VSC / MMC or one or more LCCs per pole, most commercially available electromechanical transient simulation software currently lacks the ability to freely build DC transmission systems with flexible topologies. This hinders the study of the safety of existing or future flexible-topology DC transmission systems in large power grids, hindering the development of safety and stability analysis technology for DC transmission systems in China's large power grids. Summary of the Invention

[0013] To address the above problems, the present invention proposes a method for electromechanical transient simulation of a UHV flexible topology DC transmission system, comprising:

[0014] Acquiring simulation data for an ultra-high voltage flexible topology direct current transmission system, and constructing a converter simulation model for each converter in the ultra-high voltage flexible topology direct current transmission system using a preset modeling method based on the simulation data;

[0015] Combining the simulation models into a flexible topology DC pole electromechanical transient model, and combining the flexible topology DC pole electromechanical transient model into a DC transmission system model through a lumped parameter dynamic DC network;

[0016] Based on the DC transmission system model, a preset simulation calculation method is used to perform electromechanical transient simulation calculation on the ultra-high voltage flexible topology DC transmission system.

[0017] Optional simulation data, including: topology data, parameter data, and power flow calculation data required for initialization of the ultra-high voltage flexible topology DC transmission system.

[0018] Optionally, a converter simulation model constructed using a preset modeling method includes: a converter primary system simulation model and a converter secondary system simulation model;

[0019] The preset modeling method includes: a converter primary part modeling method and a converter valve control system simulation method;

[0020] The converter primary part modeling method is used to construct a converter primary system simulation model;

[0021] The converter valve control system simulation method is used to construct a converter secondary system simulation model.

[0022] Optionally, the combination principle of combining the simulation models into a flexible topology DC pole electromechanical transient model is as follows:

[0023] Multiple strings of converters can be connected in parallel within a pole, each string of converters can have multiple layers connected in series, multiple converters can be connected in parallel on each layer, the converters in each layer must all be LCCs or VSCs, there are no restrictions on the types of converters between strings and layers, and long lines are allowed to connect the strings, layers, and converters, forming a de facto multi-terminal DC transmission system.

[0024] Optional, flexible-topology DC-pole electromechanical transient model, including various unipolar converter topology combinations.

[0025] Optionally, the simulation models are combined into a flexible topology DC pole electromechanical transient model, including:

[0026] Based on the simulation model, DC topology information is input into the constructed flexible topology DC transmission system, and the input DC topology information is parsed. Based on the parsing results, the simulation model is combined into a flexible topology DC pole electromechanical transient model. During the combination process, a linked list of converters belonging to each pole is established, and pole voltage and current commands are distributed through the pole master controller.

[0027] After combining the flexible topology DC pole electromechanical transient model, the pole topology information is maintained. If a DC transmission system fault disturbance occurs, the topology analysis is performed again, and the converter link table of each pole is updated with the maximum value information of each row / column within the pole. Then, the pole voltage and current instructions are distributed again through the pole master controller.

[0028] Optional DC topology information, including:

[0029] All parameter information of the converters in the DC transmission system, connection relationship information between converters in a single pole, connection relationship information between the converter and the DC bus, and connection relationship information between DC buses.

[0030] Optionally, parse the input DC topology information, including:

[0031] Identify the port information of each converter and DC line;

[0032] Identify the pole, column within the pole, and row within the column where each converter is located.

[0033] Optionally, a linked list of converters belonging to each pole is established, including:

[0034] Search for converters starting from the DC line port, and use the first converter found for each pole as the entry of the converter linked list for that pole;

[0035] Establish transverse branches and longitudinal branches for each pole converter. The transverse branches are the entries of the converter chain list of each column, and the longitudinal branches are the entries of each row of converters in the column.

[0036] Optionally, the pole voltage and current instructions are distributed through the pole master controller, following the following distribution principles:

[0037] The voltage instructions of the parallel converters are the same;

[0038] The sum of the current commands of the converters in each row in the same column is the same;

[0039] The sum of the voltage commands of each row in the same column is the pole voltage command, which is proportional to the initial voltage control target of each row;

[0040] The sum of the current commands of each column in the same pole is the pole current command, which is proportional to the initial control target of each column current;

[0041] The controller controls the target within the limit. If it exceeds the limit, an error prompt will be given and it will indicate that the input data is incorrect.

[0042] Optionally, the preset simulation calculation method includes: a multi-rate simulation method;

[0043] Using the preset simulation calculation method, an electromechanical transient simulation calculation is performed on the ultra-high voltage flexible topology direct current transmission system, including:

[0044] Based on the multi-rate simulation method, the UHV flexible topology DC transmission system is alternately iteratively calculated and advanced in time steps to simulate electromechanical transients. During the simulation, the iterative calculation between the AC transmission system and the UHV flexible topology DC transmission system model is completed based on the AC / DC transmission system data interface.

[0045] In another aspect, the present invention further provides a system for electromechanical transient simulation of a UHV flexible topology DC transmission system, comprising:

[0046] a modeling unit configured to obtain simulation data for an ultra-high voltage flexible topology direct current transmission system, and construct a converter simulation model for each converter in the ultra-high voltage flexible topology direct current transmission system using a preset modeling method based on the simulation data;

[0047] a combining unit, configured to combine the simulation models into a flexible topology DC pole electromechanical transient model, and combine the flexible topology DC pole electromechanical transient model into a DC transmission system model through a lumped parameter dynamic DC network;

[0048] The simulation unit is used to perform electromechanical transient simulation calculation on the ultra-high voltage flexible topology direct current transmission system based on the direct current transmission system model using a preset simulation calculation method.

[0049] Optional simulation data, including: topology data, parameter data, and power flow calculation data required for initialization of the ultra-high voltage flexible topology DC transmission system.

[0050] Optionally, a converter simulation model constructed using a preset modeling method includes: a converter primary system simulation model and a converter secondary system simulation model;

[0051] The preset modeling method includes: a converter primary part modeling method and a converter valve control system simulation method;

[0052] The converter primary part modeling method is used to construct a converter primary system simulation model;

[0053] The converter valve control system simulation method is used to construct a converter secondary system simulation model.

[0054] Optionally, the combination principle of combining the simulation models into a flexible topology DC pole electromechanical transient model is as follows:

[0055] Multiple strings of converters can be connected in parallel within a pole, each string of converters can have multiple layers connected in series, multiple converters can be connected in parallel on each layer, the converters in each layer must all be LCCs or VSCs, there are no restrictions on the types of converters between strings and layers, and long lines are allowed to connect the strings, layers, and converters, forming a de facto multi-terminal DC transmission system.

[0056] Optional, flexible-topology DC-pole electromechanical transient model, including various unipolar converter topology combinations.

[0057] Optionally, the simulation models are combined into a flexible topology DC pole electromechanical transient model, including:

[0058] Based on the simulation model, DC topology information is input into the constructed flexible topology DC transmission system, and the input DC topology information is parsed. Based on the parsing results, the simulation model is combined into a flexible topology DC pole electromechanical transient model. During the combination process, a linked list of converters belonging to each pole is established, and pole voltage and current commands are distributed through the pole master controller.

[0059] After combining the flexible topology DC pole electromechanical transient model, the pole topology information is maintained. If a DC transmission system fault disturbance occurs, the topology analysis is performed again, and the converter link table of each pole is updated with the maximum value information of each row / column within the pole. Then, the pole voltage and current instructions are distributed again through the pole master controller.

[0060] Optional DC topology information, including:

[0061] All parameter information of the converters in the DC transmission system, connection relationship information between converters in a single pole, connection relationship information between the converter and the DC bus, and connection relationship information between DC buses.

[0062] Optionally, parse the input DC topology information, including:

[0063] Identify the port information of each converter and DC line;

[0064] Identify the pole, column within the pole, and row within the column where each converter is located.

[0065] Optionally, a linked list of converters belonging to each pole is established, including:

[0066] Search for converters starting from the DC line port, and use the first converter found for each pole as the entry of the converter linked list for that pole;

[0067] Establish transverse branches and longitudinal branches for each pole converter. The transverse branches are the entries of the converter chain list of each column, and the longitudinal branches are the entries of each row of converters in the column.

[0068] Optionally, the pole voltage and current instructions are distributed through the pole master controller, following the following distribution principles:

[0069] The voltage instructions of the parallel converters are the same;

[0070] The sum of the current commands of the converters in each row in the same column is the same;

[0071] The sum of the voltage commands of each row in the same column is the pole voltage command, which is proportional to the initial voltage control target of each row;

[0072] The sum of the current commands of each column in the same pole is the pole current command, which is proportional to the initial control target of each column current;

[0073] The controller controls the target within the limit. If it exceeds the limit, an error prompt will be given and it will indicate that the input data is incorrect.

[0074] Optionally, the preset simulation calculation method includes: a multi-rate simulation method;

[0075] Using the preset simulation calculation method, an electromechanical transient simulation calculation is performed on the ultra-high voltage flexible topology direct current transmission system, including:

[0076] Based on the multi-rate simulation method, the UHV flexible topology DC transmission system is alternately iteratively calculated and advanced in time steps to simulate electromechanical transients. During the simulation, the iterative calculation between the AC transmission system and the UHV flexible topology DC transmission system model is completed based on the AC / DC transmission system data interface.

[0077] In yet another aspect, the present invention further provides a computing device comprising: one or more processors;

[0078] a processor for executing one or more programs;

[0079] When the one or more programs are executed by the one or more processors, the above-described method is implemented.

[0080] In another aspect, the present invention further provides a computer-readable storage medium having a computer program stored thereon, wherein when the computer program is executed, the method described above is implemented.

[0081] Compared with the prior art, the present invention has the following beneficial effects:

[0082] The present invention proposes a method for electromechanical transient simulation of an ultra-high voltage flexible topology DC transmission system, comprising: obtaining simulation data for the ultra-high voltage flexible topology DC transmission system; constructing a converter simulation model for each converter in the ultra-high voltage flexible topology DC transmission system using a preset modeling method based on the simulation data; combining the simulation models into a flexible topology DC pole electromechanical transient model, and combining the flexible topology DC pole electromechanical transient models into a DC transmission system model through a lumped parameter dynamic DC network; and performing electromechanical transient simulation calculations on the ultra-high voltage flexible topology DC transmission system using a preset simulation calculation method based on the DC transmission system model. The present invention can accurately simulate DC engineering and provide important reference value for planning research, scheduling operation analysis, and stability analysis of DC transmission systems with more complex topologies. BRIEF DESCRIPTION OF THE DRAWINGS

[0083] Figure 1 This is an example diagram of a single-pole structure of a flexible topology DC transmission system;

[0084] Figure 2is a flow chart of the method of the present invention;

[0085] Figure 3 It is a flow chart of an AC time-step iteration of an embodiment of the method of the present invention;

[0086] Figure 4 This is a diagram of a fundamental average value model of a voltage source converter according to an embodiment of the method of the present invention;

[0087] Figure 5 A schematic diagram of a flexible topology DC pole structure according to an embodiment of the method of the present invention;

[0088] Figure 6 This is an AC / DC iteration relationship diagram of a multi-rate DC simulation model according to an embodiment of the method of the present invention;

[0089] Figure 7 This is a diagram of the sending-end LCC AC voltage of an embodiment of the method of the present invention;

[0090] Figure 8 This is a diagram of the sending-end LCC DC voltage of an embodiment of the method of the present invention;

[0091] Figure 9 This is a diagram of the sending-end LCC DC current of an embodiment of the method of the present invention;

[0092] Figure 10 This is a sending-end LCC DC power diagram of an embodiment of the method of the present invention;

[0093] Figure 11 This is a diagram of the AC voltage of the LCC at the receiving end of the method embodiment of the present invention;

[0094] Figure 12 This is a diagram of the receiving-end LCC DC voltage of an embodiment of the method of the present invention;

[0095] Figure 13 This is a diagram of the receiving-end LCC DC current of an embodiment of the method of the present invention;

[0096] Figure 14 This is a receiving-end LCC DC power diagram of an embodiment of the method of the present invention;

[0097] Figure 15 This is a DC voltage diagram of the receiving end VSC1 of an embodiment of the method of the present invention;

[0098] Figure 16 This is a DC current diagram of the receiving end VSC1 of the method embodiment of the present invention;

[0099] Figure 17 This is a DC active power diagram of the receiving end VSC1 of the method embodiment of the present invention;

[0100] Figure 18 This is a DC voltage diagram of the receiving end VSC2 in an embodiment of the method of the present invention;

[0101] Figure 19 This is a DC current diagram of the receiving end VSC2 in an embodiment of the method of the present invention;

[0102] Figure 20 This is a DC active power diagram of the receiving end VSC2 in an embodiment of the method of the present invention;

[0103] Figure 21 This is a DC voltage diagram of the receiving end VSC3 in an embodiment of the method of the present invention;

[0104] Figure 22 This is a DC current diagram of the receiving end VSC3 of the method embodiment of the present invention;

[0105] Figure 23 This is a DC active power diagram of the receiving-end VSC3 in an embodiment of the method of the present invention;

[0106] Figure 24 It is a structural diagram of the system of the present invention. DETAILED DESCRIPTION

[0107] Exemplary embodiments of the present invention will now be described with reference to the accompanying drawings. However, the present invention may be embodied in many different forms and is not limited to the embodiments described herein. These embodiments are provided to provide a thorough and complete disclosure of the present invention and to fully convey the scope of the present invention to those skilled in the art. The terminology used in the exemplary embodiments shown in the accompanying drawings is not intended to limit the present invention. In the accompanying drawings, identical elements are denoted by the same reference numerals.

[0108] Unless otherwise specified, the terms used herein (including technical terms) have the meanings commonly understood by those skilled in the art. In addition, it is understood that terms defined in commonly used dictionaries should be understood to have the same meanings as those in the context of the relevant fields, and should not be understood as idealized or overly formal meanings.

[0109] Example 1:

[0110] The present invention proposes a method for electromechanical transient simulation of ultra-high voltage flexible topology DC transmission system, such as Figure 1 Shown, including:

[0111] Step 1: Acquire simulation data for a UHV flexible topology DC transmission system, and construct a converter simulation model for each converter in the UHV flexible topology DC transmission system using a preset modeling method based on the simulation data;

[0112] Step 2: combining the simulation models into a flexible topology DC pole electromechanical transient model, and combining the flexible topology DC pole electromechanical transient model into a DC transmission system model through a lumped parameter dynamic DC network;

[0113] Step 3: Based on the DC transmission system model, a preset simulation calculation method is used to perform electromechanical transient simulation calculation on the ultra-high voltage flexible topology DC transmission system.

[0114] The simulation data includes: topology data, parameter data and power flow calculation data required for initialization of the ultra-high voltage flexible topology DC transmission system.

[0115] The converter simulation model constructed using the preset modeling method includes: a converter primary system simulation model and a converter secondary system simulation model;

[0116] The preset modeling method includes: a converter primary part modeling method and a converter valve control system simulation method;

[0117] The converter primary part modeling method is used to construct a converter primary system simulation model;

[0118] The converter valve control system simulation method is used to construct a converter secondary system simulation model.

[0119] The principle for combining the simulation models into a flexible topology DC pole electromechanical transient model is as follows:

[0120] Multiple strings of converters can be connected in parallel within a pole, each string of converters can have multiple layers connected in series, multiple converters can be connected in parallel on each layer, the converters in each layer must all be LCCs or VSCs, there are no restrictions on the types of converters between strings and layers, and long lines are allowed to connect the strings, layers, and converters, forming a de facto multi-terminal DC transmission system.

[0121] Among them, the flexible topology DC pole electromechanical transient model includes: multiple unipolar converter topology combinations.

[0122] The simulation models are combined into a flexible topology DC pole electromechanical transient model, including:

[0123] Based on the simulation model, DC topology information is input into the constructed flexible topology DC transmission system, and the input DC topology information is parsed. Based on the parsing results, the simulation model is combined into a flexible topology DC pole electromechanical transient model. During the combination process, a linked list of converters belonging to each pole is established, and pole voltage and current commands are distributed through the pole master controller.

[0124] After combining the flexible topology DC pole electromechanical transient model, the pole topology information is maintained. If a DC transmission system fault disturbance occurs, the topology analysis is performed again, and the converter link table of each pole is updated with the maximum value information of each row / column within the pole. Then, the pole voltage and current instructions are distributed again through the pole master controller.

[0125] The DC topology information includes:

[0126] All parameter information of the converters in the DC transmission system, connection relationship information between converters in a single pole, connection relationship information between the converter and the DC bus, and connection relationship information between DC buses.

[0127] The input DC topology information is parsed, including:

[0128] Identify the port information of each converter and DC line;

[0129] Identify the pole, column within the pole, and row within the column where each converter is located.

[0130] Among them, the establishment of the converter link list of each pole includes:

[0131] Search for converters starting from the DC line port, and use the first converter found for each pole as the entry of the converter linked list for that pole;

[0132] Establish transverse branches and longitudinal branches for each pole converter. The transverse branches are the entries of the converter chain list of each column, and the longitudinal branches are the entries of each row of converters in the column.

[0133] The pole voltage and current instructions are distributed through the pole master controller, following the following distribution principles:

[0134] The voltage instructions of the parallel converters are the same;

[0135] The sum of the current commands of the converters in each row in the same column is the same;

[0136] The sum of the voltage commands of each row in the same column is the pole voltage command, which is proportional to the initial voltage control target of each row;

[0137] The sum of the current commands of each column in the same pole is the pole current command, which is proportional to the initial control target of each column current;

[0138] The controller controls the target within the limit. If it exceeds the limit, an error prompt will be given and it will indicate that the input data is incorrect.

[0139] Optionally, the preset simulation calculation method includes: a multi-rate simulation method;

[0140] Using the preset simulation calculation method, an electromechanical transient simulation calculation is performed on the ultra-high voltage flexible topology direct current transmission system, including:

[0141] Based on the multi-rate simulation method, the UHV flexible topology DC transmission system is alternately iteratively calculated and advanced in time steps to simulate electromechanical transients. During the simulation, the iterative calculation between the AC transmission system and the UHV flexible topology DC transmission system model is completed based on the AC / DC transmission system data interface.

[0142] The present invention will be further described below with reference to specific embodiments:

[0143] The specific steps include:

[0144] Read in the topology data, parameter data, and power flow calculation data required for initialization of the UHV flexible topology DC transmission system.

[0145] Each converter in the DC transmission system adopts the converter primary part modeling method and the converter valve control system simulation method to form a complete converter primary and secondary system simulation model.

[0146] Flexible topology DC pole modeling is adopted to combine converter simulation models into flexible topology DC poles;

[0147] A lumped parameter dynamic HVDC system is adopted to combine flexible topology HVDC poles to form a complete HVDC system model.

[0148] The multi-rate simulation method is used to realize the alternating iterative calculation and advancement time step of the AC / DC transmission system to complete the simulation process of the entire simulation system. Among them, the data exchange between the DC transmission system and the AC transmission system is realized through the AC / DC transmission system data interface. The iterative calculation process between the Nth AC power grid and the UHV flexible topology DC transmission system model is as follows Figure 2 shown.

[0149] The technical means involved in the above simulation can be further described as:

[0150] Modeling method of the primary part of the converter:

[0151] (1) VSC converter:

[0152] The VSC converter electromechanical transient program uses a fundamental quasi-steady-state phasor model to describe the AC transmission system. From the perspective of computational efficiency and model accuracy, the VSC converter uses a fundamental average model to describe the external characteristics that best matches the AC transmission system. The fundamental average model ignores the details of the converter valve group and assumes that all valve switches are ideally controlled and the capacitor voltages of all submodules are completely consistent. This model treats the AC side of the converter as an ideal voltage source without harmonic components, and the DC side as an ideal current source in parallel with concentrated capacitors, such as Figure 4 In the figure, the subscript dc represents the DC side, the overline represents the vector, and isc is the DC equivalent current source.

[0153] Attachment Figure 4 Voltage source provided by the AC transmission system on the middle left side The internal potential source provided by the VSC converter in the DC transmission system is connected through the equivalent resistance and inductance of the commutation transformer and the bridge arm Attachment Figure 4 The right half of the figure is the DC equivalent of the internal potential source. The current source controlled by the current source and the equivalent capacitance C of all submodules eq The entire figure constitutes the primary side model of the VSC converter.

[0154] Attachment Figure 5 In the d and q coordinates, the AC side equation is as shown in equation (1).

[0155]

[0156] (2)LCC converter:

[0157] In electromechanical transient simulation, the LCC primary system typically uses a quasi-steady-state model with high accuracy. The calculation formula for the quasi-steady-state model of the rectifier-side converter corresponds to that of the inverter side and is usually described by a delayed trigger angle. The quasi-steady-state model is described using the inverter calculation formula as an example. The DC no-load open-circuit voltage is calculated as shown in Equation (2):

[0158]

[0159] The calculation method of commutation voltage drop is as shown in formula (2-2):

[0160]

[0161] The DC line terminal voltage calculation method is as shown in formula (2-3):

[0162] V dc =V d0 cosβ+ΔV dc (4)

[0163] The commutation angle calculation method is as shown in formula (2-4):

[0164]

[0165] The calculation method of the turn-off angle is as shown in formula (2-5):

[0166] γ=β-μ (6)

[0167] The power factor calculation method is as shown in formula (2-6):

[0168]

[0169] The calculation method of DC active power is as shown in formula (2-7):

[0170] P dc =V dc I dc (8)

[0171] The calculation method of DC reactive power is as shown in formula (2-8):

[0172]

[0173] In formulas (2)-(9), V ac is the line voltage of the AC busbar of the converter valve, X c is the equivalent commutation resistance, proportional to the impedance of the commutation transformer, and β is the inverter-side triggering lead angle. In the converter's electromagnetic transient model, the time scale must be accurately determined down to the state of a single valve. Therefore, once the mathematical model of a single valve is determined, the mathematical models of the rectifier and inverter can be derived.

[0174] Converter valve control simulation system:

[0175] VSC / MMC valve controller simulation system:

[0176] The conventional control system of the VSC / MMC DC system includes an inner loop control system and an outer loop control system.

[0177] The outer control loop is responsible for providing reference values ​​(Isdref and Isqref) for the model's dq-axis currents Id and Iq. Outer control is divided into active power control and reactive power control, with the former determining Isdref and the latter determining Isqref. The most commonly used active power control is master-slave control, where the master station controls the DC voltage and the slave station controls the AC active power. Reactive power control typically uses fixed AC reactive power and fixed AC voltage. When a fixed DC station reaches its maximum power position or the DC voltage deviates, the master station is considered to have lost its control capability. DC systems with real-time inter-station communication capabilities will automatically switch between master and slave stations.

[0178] DC systems with weak communication capabilities can employ two other active power control modes: DC voltage deviation control and droop control. The former operates as constant power control during normal operation and automatically switches to constant DC voltage control when the DC voltage at the converter station reaches its limit. The latter combines DC voltage deviation and AC active power deviation as active power control information. Both modes enable automatic coordination of power between stations without inter-station communication.

[0179] The function of the inner loop controller is to give the valve side voltage The target values ​​are set so that the actual currents Id and Iq flowing through the converter valve follow the reference values ​​Isdref and Isqref. The inner-loop control can be considered the "inverse" model of the converter valve's AC circuit. The former calculates the valve-side voltage based on the d- and q-axis currents, while the latter calculates the d- and q-axis currents based on the valve-side voltage. Both have similar structures, and when appropriate parameters are used, the d- and q-axis currents can track effectively.

[0180] LCC valve controller simulation system:

[0181] The main function of the LCC converter valve controller is to output the trigger control angle of the converter. The controller includes: voltage control, closed-loop current control, inverter side Amax control, commutation failure prediction control, rectifier side minimum trigger angle control, Gamma0 control, inverter side minimum commutation margin control, low-voltage current limiting control, low-voltage current limiting controller, etc.

[0182] Flexible topology DC pole modeling:

[0183] To adapt to different possible UHVDC transmission topologies, a general flexible-topology DC pole electromechanical transient model construction method is proposed. A flexible-topology DC pole refers to a system in which the number, type, and connection method of converters within a single pole can be flexibly specified based on permitted combinations.

[0184] Flexible topology DC pole structure Figure 5 As shown, the combination principles are as follows:

[0185] 1. Multiple converters can be connected in parallel in one pole.

[0186] 2. Each string of converters can be connected in series in multiple layers.

[0187] 3. Multiple converters can be connected in parallel on each layer.

[0188] 4. The converters connected in parallel on each layer must be LCC or VSC.

[0189] 5. There is no restriction on the type of inter-string and inter-layer converters.

[0190] 6. Long lines are allowed to connect each string, layer and converter, forming a de facto multi-terminal DC transmission system.

[0191] Since flexible topology DC poles include all possible unipolar converter topology combinations, all DC projects currently in operation or under planning, design, and construction can be described using flexible topology DC poles.

[0192] The flexible topology DC pole model construction includes the following steps:

[0193] 1. Input DC topology information into the constructed flexible topology DC transmission system. This information should include all converter parameter information in the DC transmission system, the connection relationship between converters within a single pole, and the connection relationship between the converter and the DC bus, and between the DC buses.

[0194] 2. Input data analysis: The port information of each converter, DC line and other components is integrated to identify the pole, column and row of each converter.

[0195] 3. Establish a linked list of converters for each pole: Search for converters starting from the DC line port. The first converter found for each pole is the entry to the linked list of converters for that pole. Establish horizontal and vertical branches for each pole converter. The horizontal branches are the entries to the linked list of converters for each column, and the vertical branches are the entries to each row of converters in the column. The branches are selected based on the topology search results without any other special information. Figure 5 In the figure, bold fonts indicate branches, and bold borders indicate entrances.

[0196] 4. The pole master controller distributes pole voltage and current instructions:

[0197] At each simulation time step, the pole voltage and current instructions are calculated based on the active power and voltage control targets of the pole master controller, and then distributed to each converter according to the linked list, following the following distribution principles:

[0198] (1) The voltage instructions of the parallel converters are the same;

[0199] (2) The sum of the current instructions of each row of converters in the same column is the same;

[0200] (3) The sum of the voltage commands of each row in the same column is the pole voltage command, which is proportional to the initial voltage control target of each row;

[0201] (4) The sum of the current commands of each column in the same pole is the pole current command, which is proportional to the initial control target of each column current;

[0202] (6) The controller’s control target does not exceed the limit. If it exceeds the limit, an error prompt will be given to indicate that the input data is incorrect.

[0203] (7) After obtaining the current and voltage instructions of each valve according to the above rules, the control reference target of each controller (such as the constant power control reference value) is inferred based on the valve control type. For VSC / MMC controllers with two control targets, the master controller only affects its related control targets and does not intervene in the reference values ​​of the additional control targets.

[0204] 5. Maintaining topological information:

[0205] After a fault disturbance occurs in the DC transmission system (for example, a converter within a pole is locked / invalid), return to step 3 to perform a new topology analysis, update the converter link table for each pole, and update the maximum value information for each row and column within the pole. Then, proceed to step 4 to continue the simulation.

[0206] Lumped parameter dynamic DC network:

[0207] The DC link of a UHVDC flexible transmission system with cascaded high- and low-end valve groups uses a lumped parameter model that accounts for the dynamics of inductance, capacitance, and resistance. The current injected into the DC link by each converter is the sole source of power on the DC side. Its value is proportional to the algebraic sum of the AC power and conversion losses, and inversely proportional to the DC voltage. If multiple DC links form a DC transmission system, standard solutions for electromagnetic transient networks, such as the historical current source method, can be used. Solutions for DC transmission systems should avoid numerical oscillations caused by DC faults or disturbances.

[0208] Multi-rate simulation method:

[0209] The control cycle of DC equipment is usually 100-200us, which is much smaller than the usual electromechanical transient simulation step size (10ms). If the latter is too small, the calculation time will be long, and the accuracy improvement will be limited because the AC transmission system does not consider harmonics. If the VSC adopts the electromechanical transient simulation step size, the control cycle will be extended, which will easily cause DC overvoltage and overcurrent problems and large simulation errors. Multi-rate simulation is an effective solution. The iteration relationship between the AC and DC sides is shown in the attached figure. Figure 6 The AC side is simulated in one step, and the DC side is simulated in multiple steps; the DC side follows the AC side in multiple iterations within one AC time step; the two sides exchange variables at the end of each AC iteration.

[0210] Attachment Figure 6 Description: Attached Figure 6 The figure shows the AC / DC iteration relationship of the multi-rate DC simulation model. The dotted backward arrow indicates that since the electromechanical transient state of the alternating iteration method requires multiple iterations in one time step, this model needs to follow the changes in the information provided by the AC side, retrieve the state multiple time steps ago, and re-simulate within one AC step.

[0211] AC / DC transmission system interface:

[0212] The node admittance matrix is ​​used to solve the voltage of the electromechanical transient network. It is necessary to calculate the current injected into the AC transmission system by each dynamic component at each iteration step. The AC side currents isd and isq of the converter are the currents injected into the AC transmission system by the converter and naturally become interface variables. The interface location is the PCC point, that is, the busbar on the AC transmission system side. In multi-rate simulation, isd and isq may change in each DC time step, and a comprehensive analysis is required to determine the current injected into the AC transmission system at each AC time step. The power interface is usually used to ensure that the average power of the AC and DC sides of the converter is equal within an AC time step. The current injected into the AC transmission system by the converter in a single AC time step is shown in Equation (10). n is the ratio of the AC simulation step to the DC simulation step, and k is the DC time step. (When the multi-rate model is not used, n = 1, and k is the same as the AC transmission system time step)

[0213]

[0214] In formula (10):

[0215]

[0216] Existing electromechanical transient simulation systems lack the ability to simulate flexible topology DC systems. They can only simulate DC transmission systems with one VSC / MMC per pole, or one or more LCCs per pole. They lack the ability to freely simulate flexible topology DC transmission systems.

[0217] To demonstrate the accuracy of the present invention, the simulation data of the manufacturer's RTDS electromagnetic model is compared with the simulation data of the manufacturer's RTDS electromagnetic model. The simulation results of the topological structure built by the present invention and the manufacturer's RTDS electromagnetic model are as follows: Figures 7 to 23 As shown in the figure, all boxed lines represent simulation results from the manufacturer's RTDS, while dotted lines represent simulation results obtained using the simulation system proposed in this patent. During the simulation, a three-phase metallic instantaneous ground fault with a fault duration of 0.1s was set at the outlet of the receiving LCC AC transmission system. The simulation results show that the error between the simulation results of the constructed simulation system and the manufacturer's RTDS electromagnetic model is small.

[0218] The manufacturer's RTDS electromagnetic model requires a lot of computing power and is not suitable for security analysis of ultra-large-scale power grids. This patent provides an electromechanical transient simulation system for ultra-high voltage flexible topology DC transmission systems that can quickly analyze the safety and stability performance of large power grids while ensuring sufficient accuracy.

[0219] The Jiansu (Baihetan-Jiangsu) DC transmission system currently in operation in China utilizes a hybrid cascaded multi-terminal flexible direct current access system. This patent enables accurate simulation of the Jiansu (Baihetan-Jiangsu) DC transmission project, providing valuable insights into planning, scheduling, and stability analysis for DC transmission system access systems with potentially more complex topologies.

[0220] Example 2:

[0221] The present invention also proposes a system 200 for electromechanical transient simulation of a UHV flexible topology DC transmission system, such as Figure 24 Shown, including:

[0222] A modeling unit 201 is configured to obtain simulation data for a UHV flexible topology DC transmission system, and based on the simulation data, construct a converter simulation model for each converter in the UHV flexible topology DC transmission system using a preset modeling method;

[0223] A combining unit 202 is configured to combine the simulation models into a flexible topology DC pole electromechanical transient model, and combine the flexible topology DC pole electromechanical transient model into a DC transmission system model through a lumped parameter dynamic DC network;

[0224] The simulation unit 203 is configured to perform electromechanical transient simulation calculations on the ultra-high voltage flexible topology direct current transmission system based on the direct current transmission system model and using a preset simulation calculation method.

[0225] The simulation data includes: topology data, parameter data and power flow calculation data required for initialization of the ultra-high voltage flexible topology DC transmission system.

[0226] The converter simulation model constructed using the preset modeling method includes: a converter primary system simulation model and a converter secondary system simulation model;

[0227] The preset modeling method includes: a converter primary part modeling method and a converter valve control system simulation method;

[0228] The converter primary part modeling method is used to construct a converter primary system simulation model;

[0229] The converter valve control system simulation method is used to construct a converter secondary system simulation model.

[0230] The principle for combining the simulation models into a flexible topology DC pole electromechanical transient model is as follows:

[0231] Multiple strings of converters can be connected in parallel within a pole, each string of converters can have multiple layers connected in series, multiple converters can be connected in parallel on each layer, the converters in each layer must all be LCCs or VSCs, there are no restrictions on the types of converters between strings and layers, and long lines are allowed to connect the strings, layers, and converters, forming a de facto multi-terminal DC transmission system.

[0232] Among them, the flexible topology DC pole electromechanical transient model includes: multiple unipolar converter topology combinations.

[0233] The simulation models are combined into a flexible topology DC pole electromechanical transient model, including:

[0234] Based on the simulation model, DC topology information is input into the constructed flexible topology DC transmission system, and the input DC topology information is parsed. Based on the parsing results, the simulation model is combined into a flexible topology DC pole electromechanical transient model. During the combination process, a linked list of converters belonging to each pole is established, and pole voltage and current commands are distributed through the pole master controller.

[0235] After combining the flexible topology DC pole electromechanical transient model, the pole topology information is maintained. If a DC transmission system fault disturbance occurs, the topology analysis is performed again, and the converter link table of each pole is updated with the maximum value information of each row / column within the pole. Then, the pole voltage and current instructions are distributed again through the pole master controller.

[0236] The DC topology information includes:

[0237] All parameter information of the converters in the DC transmission system, connection relationship information between converters in a single pole, connection relationship information between the converter and the DC bus, and connection relationship information between DC buses.

[0238] The input DC topology information is parsed, including:

[0239] Identify the port information of each converter and DC line;

[0240] Identify the pole, column within the pole, and row within the column where each converter is located.

[0241] Among them, the establishment of the converter link list of each pole includes:

[0242] Search for converters starting from the DC line port, and use the first converter found for each pole as the entry of the converter linked list for that pole;

[0243] Establish transverse branches and longitudinal branches for each pole converter. The transverse branches are the entries of the converter chain list of each column, and the longitudinal branches are the entries of each row of converters in the column.

[0244] The pole voltage and current instructions are distributed through the pole master controller, following the following distribution principles:

[0245] The voltage instructions of the parallel converters are the same;

[0246] The sum of the current commands of the converters in each row in the same column is the same;

[0247] The sum of the voltage commands of each row in the same column is the pole voltage command, which is proportional to the initial voltage control target of each row;

[0248] The sum of the current commands of each column in the same pole is the pole current command, which is proportional to the initial control target of each column current;

[0249] The controller controls the target within the limit. If it exceeds the limit, an error prompt will be given and it will indicate that the input data is incorrect.

[0250] Among them, the preset simulation calculation method includes: a multi-rate simulation method;

[0251] Using the preset simulation calculation method, an electromechanical transient simulation calculation is performed on the ultra-high voltage flexible topology direct current transmission system, including:

[0252] Based on the multi-rate simulation method, the UHV flexible topology DC transmission system is alternately iteratively calculated and advanced in time steps to simulate electromechanical transients. During the simulation, the iterative calculation between the AC transmission system and the UHV flexible topology DC transmission system model is completed based on the AC / DC transmission system data interface.

[0253] The present invention can accurately simulate DC projects and provide important reference value for planning research, scheduling operation analysis, stability analysis, etc. of DC transmission system access systems with more complex topologies.

[0254] Example 3:

[0255] Based on the same inventive concept, the present invention also provides a computer device, which includes a processor and a memory, wherein the memory is used to store a computer program, the computer program includes program instructions, and the processor is used to execute the program instructions stored in the computer storage medium. The processor may be a central processing unit (CPU), or may be other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA) or other programmable logic devices, discrete gates or transistor logic devices, discrete hardware components, etc. It is the computing core and control core of the terminal, which is suitable for implementing one or more instructions, specifically suitable for loading and executing one or more instructions in the computer storage medium to implement the corresponding method flow or corresponding function, so as to implement the steps of the method in the above embodiment.

[0256] Example 4:

[0257] Based on the same inventive concept, the present invention also provides a storage medium, specifically a computer-readable storage medium (Memory), which is a memory device in a computer device for storing programs and data. It can be understood that the computer-readable storage medium here can include both built-in storage media in the computer device and, of course, extended storage media supported by the computer device. The computer-readable storage medium provides a storage space that stores the operating system of the terminal. In addition, one or more instructions suitable for being loaded and executed by the processor are also stored in the storage space. These instructions can be one or more computer programs (including program codes). It should be noted that the computer-readable storage medium here can be a high-speed RAM memory or a non-volatile memory, such as at least one disk memory. The processor can load and execute one or more instructions stored in the computer-readable storage medium to implement the steps of the method in the above embodiment.

[0258] It will be understood by those skilled in the art that the embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Furthermore, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code. The solutions in the embodiments of the present invention may be implemented in various computer languages, for example, the object-oriented programming language Java and the interpreted scripting language JavaScript.

[0259] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowcharts and / or block diagrams, as well as combinations of processes and / or blocks in the flowcharts and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowcharts and / or block diagrams. Figure 1 a process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0260] These computer program instructions may also be stored in a computer readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 a process or multiple processes and / or boxes Figure 1 The function specified in one or more boxes.

[0261] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operational steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing the instructions executed on the computer or other programmable device for implementing the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0262] Although the preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0263] Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if such changes and modifications fall within the scope of the claims and their equivalents, the present invention is intended to include such changes and modifications.

Claims

1. A method for electromechanical transient simulation of ultra-high voltage flexible topology direct current transmission system, characterized in that: include: Acquiring simulation data for an ultra-high voltage flexible topology direct current transmission system, and constructing a converter simulation model for each converter in the ultra-high voltage flexible topology direct current transmission system using a preset modeling method based on the simulation data; Combining the simulation models into a flexible topology DC pole electromechanical transient model, and combining the flexible topology DC pole electromechanical transient model into a DC transmission system model through a lumped parameter dynamic DC network; Based on the DC transmission system model, a preset simulation calculation method is used to perform electromechanical transient simulation calculation on the ultra-high voltage flexible topology DC transmission system.

2. The method according to claim 1, characterized in that The simulation data includes: topology data, parameter data and power flow calculation data required for initialization of the ultra-high voltage flexible topology direct current transmission system.

3. The method according to claim 1, characterized in that A converter simulation model constructed using a preset modeling method includes: a converter primary system simulation model and a converter secondary system simulation model; The preset modeling method includes: a converter primary part modeling method and a converter valve control system simulation method; The converter primary part modeling method is used to construct a converter primary system simulation model; The converter valve control system simulation method is used to construct a converter secondary system simulation model.

4. The method according to claim 1, wherein The combination principle of combining the simulation models into a flexible topology DC pole electromechanical transient model is as follows: Multiple strings of converters can be connected in parallel within a pole, each string of converters can have multiple layers connected in series, multiple converters can be connected in parallel on each layer, the converters in each layer must all be LCCs or VSCs, there are no restrictions on the types of converters between strings and layers, and long lines are allowed to connect the strings, layers, and converters, forming a de facto multi-terminal DC transmission system.

5. The method according to claim 1, characterized in that The flexible topology DC pole electromechanical transient model includes: a plurality of unipolar converter topology combinations.

6. The method according to claim 1, characterized in that Combining the simulation models into a flexible topology DC pole electromechanical transient model includes: Based on the simulation model, DC topology information is input into the constructed flexible topology DC transmission system, and the input DC topology information is parsed. Based on the parsing results, the simulation model is combined into a flexible topology DC pole electromechanical transient model. During the combination process, a linked list of converters belonging to each pole is established, and pole voltage and current commands are distributed through the pole master controller. After combining the flexible topology DC pole electromechanical transient model, the pole topology information is maintained. If a DC transmission system fault disturbance occurs, the topology analysis is performed again, and the converter link table of each pole is updated with the maximum value information of each row / column within the pole. Then, the pole voltage and current instructions are distributed again through the pole master controller.

7. The method according to claim 6, characterized in that The DC topology information includes: All parameter information of the converters in the DC transmission system, connection relationship information between converters in a single pole, connection relationship information between the converter and the DC bus, and connection relationship information between DC buses.

8. The method according to claim 6, characterized in that The step of parsing the input DC topology information includes: Identify the port information of each converter and DC line; Identify the pole, column within the pole, and row within the column where each converter is located.

9. The method according to claim 6, characterized in that The step of establishing a linked list of converters belonging to each pole includes: Search for converters starting from the DC line port, and use the first converter found for each pole as the entry of the converter linked list for that pole; Establish transverse and longitudinal branches for each pole converter. The transverse branches are the entries of the converter chain list of each column, and the longitudinal branches are the entries of each row of converters in the column.

10. The method according to claim 6, characterized in that The pole voltage and current instructions are distributed by the pole master controller according to the following distribution principles: The voltage instructions of the parallel converters are the same; The sum of the current commands of the converters in each row in the same column is the same; The sum of the voltage commands of each row in the same column is the pole voltage command, which is proportional to the initial voltage control target of each row; The sum of the current commands of each column in the same pole is the pole current command, which is proportional to the initial control target of each column current; The controller controls the target within the limit. If it exceeds the limit, an error prompt will be given and it will indicate that the input data is incorrect.

11. The method according to claim 1, characterized in that The preset simulation calculation method includes: a multi-rate simulation method; Using the preset simulation calculation method, an electromechanical transient simulation calculation is performed on the ultra-high voltage flexible topology direct current transmission system, including: Based on the multi-rate simulation method, the UHV flexible topology DC transmission system is alternately iteratively calculated and advanced in time steps to simulate electromechanical transients. During the simulation, the iterative calculation between the AC transmission system and the UHV flexible topology DC transmission system model is completed based on the AC / DC transmission system data interface.

12. A system for electromechanical transient simulation of ultra-high voltage flexible topology direct current transmission system, characterized in that: include: a modeling unit configured to obtain simulation data for an ultra-high voltage flexible topology direct current transmission system, and construct a converter simulation model for each converter in the ultra-high voltage flexible topology direct current transmission system using a preset modeling method based on the simulation data; a combining unit, configured to combine the simulation models into a flexible topology DC pole electromechanical transient model, and combine the flexible topology DC pole electromechanical transient model into a DC transmission system model through a lumped parameter dynamic DC network; The simulation unit is used to perform electromechanical transient simulation calculation on the ultra-high voltage flexible topology direct current transmission system based on the direct current transmission system model using a preset simulation calculation method.

13. The system according to claim 12, wherein: The simulation data includes: topology data, parameter data and power flow calculation data required for initialization of the ultra-high voltage flexible topology direct current transmission system.

14. The system according to claim 12, wherein: A converter simulation model constructed using a preset modeling method includes: a converter primary system simulation model and a converter secondary system simulation model; The preset modeling method includes: a converter primary part modeling method and a converter valve control system simulation method; The converter primary part modeling method is used to construct a converter primary system simulation model; The converter valve control system simulation method is used to construct a converter secondary system simulation model.

15. The system according to claim 12, wherein: The combination principle of combining the simulation models into a flexible topology DC pole electromechanical transient model is as follows: Multiple strings of converters can be connected in parallel within a pole, each string of converters can have multiple layers connected in series, multiple converters can be connected in parallel on each layer, the converters in each layer must all be LCCs or VSCs, there are no restrictions on the types of converters between strings and layers, and long lines are allowed to connect the strings, layers, and converters, forming a de facto multi-terminal DC transmission system.

16. The system according to claim 12, wherein: The flexible topology DC pole electromechanical transient model includes: a plurality of unipolar converter topology combinations.

17. The system according to claim 12, wherein: Combining the simulation models into a flexible topology DC pole electromechanical transient model includes: Based on the simulation model, DC topology information is input into the constructed flexible topology DC transmission system, and the input DC topology information is parsed. Based on the parsing results, the simulation model is combined into a flexible topology DC pole electromechanical transient model. During the combination process, a linked list of converters belonging to each pole is established, and pole voltage and current commands are distributed through the pole master controller. After combining the flexible topology DC pole electromechanical transient model, the pole topology information is maintained. If a DC transmission system fault disturbance occurs, the topology analysis is performed again, and the converter link table of each pole is updated with the maximum value information of each row / column within the pole. Then, the pole voltage and current instructions are distributed again through the pole master controller.

18. The system according to claim 17, wherein: The DC topology information includes: All parameter information of the converters in the DC transmission system, connection relationship information between converters in a single pole, connection relationship information between the converter and the DC bus, and connection relationship information between DC buses.

19. The system according to claim 17, wherein: The step of parsing the input DC topology information includes: Identify the port information of each converter and DC line; Identify the pole, column within the pole, and row within the column where each converter is located.

20. The system according to claim 17, wherein: The step of establishing a linked list of converters belonging to each pole includes: Search for converters starting from the DC line port, and use the first converter found for each pole as the entry of the converter linked list for that pole; Establish transverse and longitudinal branches for each pole converter. The transverse branches are the entries of the converter chain list of each column, and the longitudinal branches are the entries of each row of converters in the column.

21. The system according to claim 17, wherein: The pole voltage and current instructions are distributed by the pole master controller according to the following distribution principles: The voltage instructions of the parallel converters are the same; The sum of the current commands of the converters in each row in the same column is the same; The sum of the voltage commands of each row in the same column is the pole voltage command, which is proportional to the initial voltage control target of each row; The sum of the current commands of each column in the same pole is the pole current command, which is proportional to the initial control target of each column current; The controller controls the target within the limit. If it exceeds the limit, an error prompt will be given and it will indicate that the input data is incorrect.

22. The system according to claim 17, wherein: The preset simulation calculation method includes: a multi-rate simulation method; Using the preset simulation calculation method, an electromechanical transient simulation calculation is performed on the ultra-high voltage flexible topology direct current transmission system, including: Based on the multi-rate simulation method, the UHV flexible topology DC transmission system is alternately iteratively calculated and advanced in time steps to simulate electromechanical transients. During the simulation, the iterative calculation between the AC transmission system and the UHV flexible topology DC transmission system model is completed based on the AC / DC transmission system data interface.

23. A computer device, characterized in that: include: one or more processors; a processor for executing one or more programs; When the one or more programs are executed by the one or more processors, the method according to any one of claims 1 to 11 is implemented.

24. A computer-readable storage medium, characterized in that A computer program is stored thereon, and when the computer program is executed, the method according to any one of claims 1 to 11 is implemented.

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