Configuration method and device of DRU-MMC converter direct-current power transmission system
By calculating and configuring the parameters of each component in the DRU-MMC converter DC transmission system, the problem of poor system stability was solved, and the system achieved flexible adaptability and stability in different power transmission tasks, supporting black start and grid-connected operation of wind farms.
Patent Information
- Application Number
- CN202511302186.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-09-12
- Publication Date
- 2025-11-21
AI Technical Summary
The existing DRU-MMC converter DC transmission system has poor stability in offshore wind farms. Especially when the wind farm adopts grid-connected control, the control parameters between the auxiliary converter and the DRU-MMC converter are difficult to design independently, making it difficult for the system to adapt to different power transmission tasks.
By acquiring the DRU AC data, MMC inverter side operating condition data, and grid rated angular frequency of the DRU-MMC converter DC transmission system, the parameters of the DRU rectifier, MMC inverter side devices, bridge arm reactors, and auxiliary converters are calculated and configured to form an optimized DRU-MMC converter DC transmission system, ensuring the system maintains stability under different power transmission tasks.
The DRU-MMC converter DC transmission system has achieved flexible adaptability in different power transmission tasks, improved the system's stability and voltage support capability, and supported the black start and grid-connected operation of wind farms.
Smart Images
Figure CN120999729A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of DC power transmission technology, and in particular to a configuration method and apparatus for a DRU-MMC converter DC power transmission system. Background Technology
[0002] Among renewable energy sources, offshore wind power is gradually becoming a development focus due to its significant advantages such as abundant resources, stable wind speeds, and large grid connection capacity. However, because wind farms are often located offshore or far from load centers, their transmission distances are long and their power fluctuations are strong, placing higher demands on the power system. Among these, the DRU-MMC (Direct Current Unit) structure DC transmission system is one of the mainstream solutions for large-capacity offshore wind power transmission.
[0003] When wind farms adopt grid-connected control, auxiliary converters are often introduced to achieve black start, but this significantly increases control complexity and parameter design challenges. Because of the high coupling between the auxiliary converter and the DRU-MMC converter, its control parameters cannot be designed independently. Therefore, current DRU-MMC converter DC transmission systems are ill-suited to different transmission tasks and suffer from poor stability. Summary of the Invention
[0004] This invention provides a configuration method and apparatus for a DRU-MMC converter DC transmission system, which can solve the problem of poor stability in existing DC transmission systems.
[0005] To address the aforementioned technical problems, this invention provides a configuration method for a DRU-MMC converter DC transmission system, comprising: Acquire DRU AC data, MMC inverter-side operating condition data, grid rated angular frequency, and auxiliary converter electrical performance data of the DRU-MMC converter DC transmission system; Based on the electrical characteristics of the DRU rectifier and the AC data of the DRU, the parameters of the DRU rectifier are determined; wherein, the parameters of the DRU rectifier include the steady-state electrical characteristic parameters of the DRU rectifier and the number of diodes required for the DRU; Based on the DRU AC data and the MMC inverter-side operating condition data, the MMC inverter-side parameters are calculated; wherein, the MMC inverter-side parameters include the bridge arm submodule capacitance value; Based on the system negative sequence constraint of the DRU-MMC converter DC transmission system and the rated angular frequency of the power grid, the parameters of the bridge arm reactor are calculated; wherein, the parameters of the bridge arm reactor include the bridge arm reactance and the bridge arm reactor inductance value; The auxiliary converter parameters are calculated based on the electrical performance data of the auxiliary converter; wherein, the auxiliary converter parameters include the number of series power modules in the auxiliary single bridge arm, the auxiliary capacitor voltage constraint, and the auxiliary bridge arm inductance constraint; Based on the parameters of the DRU rectifier, the parameters of the MMC inverter side, the parameters of the bridge arm reactor, and the parameters of the auxiliary converter, the components in the DRU-MMC converter DC transmission system are configured to form an optimized DRU-MMC converter DC transmission system.
[0006] As a preferred embodiment, determining the DRU rectifier parameters based on the DRU electrical characteristics and the DRU AC data includes: Based on the DRU rectifier topology in the DRU-MMC converter DC transmission system, the DRU electrical characteristics of the DRU rectifier are determined. A steady-state mathematical model of the DRU rectifier is constructed based on the electrical characteristics of the DRU. Based on the active power, reactive power, and AC-side input fundamental frequency voltage of the DRU from the AC data of the DRU, the steady-state mathematical model is solved to obtain the steady-state electrical characteristic parameters of the DRU rectifier; wherein, the steady-state electrical characteristic parameters include the DC voltage of the DRU output side, the DC current of the DRU output side, the AC-side input fundamental frequency current of the DRU, the AC-side power factor angle of the DRU, and the commutation overlap angle. Based on the rated voltage of the DRU AC side in the DRU AC data, as well as the rated voltage and preset voltage safety margin factor of the preset diodes, calculate the number of diodes required for the DRU.
[0007] As a preferred embodiment, the steady-state mathematical model of the DRU rectifier is as follows: In the formula, This refers to the DC voltage on the output side of the DRU. The voltage transformation ratio of the converter transformer grid / valve side winding; Input base frequency voltage to the AC side of the DRU; This refers to the DC current on the output side of the DRU. For the commutation reactance on the AC side of the DRU; Input the base frequency current to the AC side of the DRU; The power factor angle on the AC side of the DRU; The reactive power input to the DRU on the AC bus; The active power input to the DRU for the AC bus; This refers to the commutation overlap angle; It is direct current; This refers to the leakage reactance of the converter transformer.
[0008] As a preferred embodiment, the calculation of the required number of diodes for the DRU based on the DRU AC side rated voltage in the DRU AC data, and the rated voltage and preset voltage safety margin factor of the preset diodes, includes: In the formula, The number of diodes required for the DRU; This refers to the rated voltage on the AC side of the DRU. This is the preset rated voltage of the diode; This is the preset voltage safety margin factor.
[0009] As a preferred embodiment, the calculation of MMC inverter-side parameters based on the DRU AC data and the MMC inverter-side operating condition data includes: The DC voltage on the DRU output side is divided by the preset number of bridge arm sub-modules on the MMC inverter side to calculate the capacitor voltage of the bridge arm module. Based on the active power and reactive power of the MMC inverter side in the MMC inverter side operating condition data, calculate the apparent power of the DRU AC side. Based on the preset MMC inverter-side capacitor voltage fluctuation rate, preset MMC modulation ratio, apparent power of the DRU AC side, preset number of bridge arm sub-modules of the MMC inverter side, MMC angular frequency on the power frequency side, and capacitor voltage of the bridge arm sub-module, the capacitance value of the bridge arm module is calculated, and the capacitance value of the bridge arm module is determined as the MMC inverter-side parameter. The capacitance value of the bridge arm submodule is calculated using the following formula: In the formula, The preset MMC inverter-side capacitor voltage fluctuation rate; The power rating is for the AC side of the DRU; The preset MMC modulation ratio; The preset number of MMC inverter-side bridge arm sub-modules; The MMC angular frequency on the power frequency side; This refers to the capacitor voltage of the bridge arm submodule; This refers to the capacitance value of the bridge arm submodule.
[0010] As a preferred embodiment, the calculation of the arm reactor parameters based on the system negative sequence constraint of the DRU-MMC converter DC transmission system and the rated angular frequency of the power grid includes: Based on the system negative sequence constraint of the DRU-MMC converter DC transmission system, the range of negative sequence phase angle values is determined. Based on the MMC arm reactance phase correlation formula and the range of negative sequence phase angle values, the range of values for the MMC inverter side arm reactance is determined. Determine the series resonant angular frequency of the phase unit based on the rated angular frequency of the power grid; The inductance value of the bridge arm reactor is calculated based on the series resonant angular frequency of the phase unit, the preset number of bridge arm sub-modules on the MMC inverter side, and the capacitance value of the bridge arm module. The inductance value of the bridge arm reactor is calculated using the following formula: In the formula, The resonant angular frequency of the phase unit in series; The preset number of MMC inverter-side bridge arm sub-modules; The capacitance value of the bridge arm submodule; This represents the inductance value of the bridge arm reactor.
[0011] As a preferred embodiment, the calculation of auxiliary converter parameters based on the auxiliary converter electrical performance data includes: The number of auxiliary single-bridge arm series power modules is calculated by dividing the DC voltage on the output side of the DRU by the DC voltage level of the auxiliary single-bridge arm series power module in the electrical performance data of the auxiliary converter. The auxiliary capacitor voltage constraint is determined based on the converter rated capacity, power frequency angular frequency, DC side reference voltage, preset maximum voltage fluctuation rate, and the number of series power modules of the auxiliary single bridge arm in the auxiliary converter electrical performance data. The auxiliary capacitor voltage constraint is as follows: In the formula, For auxiliary capacitor voltage; To assist in increasing the number of series power modules in a single bridge arm; This refers to the rated capacity of the converter; It is the power frequency angular frequency; The preset maximum voltage fluctuation rate; This is the DC-side reference voltage; The auxiliary bridge arm inductance constraint is determined based on the number of series power modules in the auxiliary single bridge arm, the power frequency angular frequency, and the auxiliary capacitor voltage. The auxiliary bridge arm inductance constraint is as follows: In the formula, To assist the bridge arm inductor.
[0012] As a preferred embodiment, the DRU rectifier parameters also include the rated on-state current constraint of the diodes required by the DRU, which is determined using the following formula: Based on the rated DC-side current of the DRU and the alternating conduction characteristics of the DRU converter valve in the DRU rectifier, the maximum effective value of the bridge arm current of the DRU converter valve is calculated using the following formula: In the formula, This is the effective value of the maximum bridge arm current of the DRU converter valve; This refers to the rated current on the DC side of the DRU. Based on the maximum effective value of the bridge arm current and the preset current safety margin coefficient, the rated on-state current constraint of the diode required for the DRU is calculated using the following formula: In the formula, This is the rated on-state current; This is the preset current safety margin factor.
[0013] As a preferred embodiment, after configuring the various components within the DRU-MMC converter DC transmission system based on the DRU rectifier parameters, the MMC inverter-side parameters, the bridge arm reactor parameters, and the auxiliary converter parameters to form an optimized DRU-MMC converter DC transmission system, the system further includes: When the wind farm adopts grid-connected control, the auxiliary converter of the optimized DRU-MMC converter DC transmission system provides voltage support for the wind farm during the black start phase, controls the grid connection point voltage and frequency, and provides commutation AC voltage for the DRU rectifier. The DRU rectifier, which controls the optimized DRU-MMC converter DC transmission system, rectifies the AC power output from the wind farm into DC power based on the commutation AC voltage, and transmits the DC power to the MMC inverter side through a DC line. The optimized DRU-MMC converter DC transmission system controls the MMC inverter side to invert the DC power into standard AC power, and then connects the standard AC power into the onshore power grid.
[0014] Accordingly, the present invention provides a configuration device for a DRU-MMC converter DC transmission system, comprising: a data acquisition module, a DRU rectifier parameter determination module, an MMC inverter side parameter determination module, a bridge arm reactor parameter determination module, an auxiliary converter parameter determination module, and a device configuration module; The data acquisition module is used to acquire DRU AC data, MMC inverter side operating condition data, grid rated angular frequency and auxiliary converter electrical performance data of the DRU-MMC converter DC transmission system. The DRU rectifier parameter determination module is used to determine the DRU rectifier parameters based on the DRU electrical characteristics and the DRU AC data; wherein, the DRU rectifier parameters include the steady-state electrical characteristic parameters of the DRU rectifier and the number of diodes required for the DRU; The MMC inverter-side parameter determination module is used to calculate the MMC inverter-side parameters based on the DRU AC data and the MMC inverter-side operating condition data; wherein, the MMC inverter-side parameters include the bridge arm submodule capacitance value; The arm reactor parameter determination module is used to calculate the arm reactor parameters based on the system negative sequence constraint of the DRU-MMC converter DC transmission system and the rated angular frequency of the power grid; wherein, the arm reactor parameters include the arm reactor and the arm reactor inductance value; The auxiliary converter parameter determination module is used to calculate the auxiliary converter parameters based on the auxiliary converter electrical performance data; wherein, the auxiliary converter parameters include the number of series power modules in the auxiliary single bridge arm, the auxiliary capacitor voltage constraint, and the auxiliary bridge arm inductance constraint; The device configuration module is used to configure each device in the DRU-MMC converter DC transmission system based on the DRU rectifier parameters, the MMC inverter side parameters, the bridge arm reactor parameters, and the auxiliary converter parameters, to form an optimized DRU-MMC converter DC transmission system.
[0015] Compared with the prior art, the embodiments of the present invention have the following beneficial effects: This invention provides a configuration method for a DRU-MMC converter DC transmission system. The method involves acquiring DRU AC data, MMC inverter-side operating condition data, grid rated angular frequency, and auxiliary converter electrical performance data of the DRU-MMC converter DC transmission system. Based on the DRU electrical characteristics and DRU AC data, DRU rectifier parameters are determined. MMC inverter-side parameters are calculated based on the DRU AC data and MMC inverter-side operating condition data. Arm reactor parameters are calculated based on the system negative sequence constraint and grid rated angular frequency of the DRU-MMC converter DC transmission system. Auxiliary converter parameters are calculated based on the auxiliary converter electrical performance data. Finally, based on the DRU rectifier parameters, MMC inverter-side parameters, arm reactor parameters, and auxiliary converter parameters, the various components within the DRU-MMC converter DC transmission system are configured to form an optimized DRU-MMC converter DC transmission system. This invention calculates the parameters of the DRU rectifier, MMC inverter side, bridge arm reactor, and auxiliary converter based on real-time system electrical parameter data of the DRU-MMC converter DC transmission system. This allows for the configuration of appropriate DRU rectifiers, MMC inverter side devices, bridge arm reactors, and auxiliary converters within the DRU-MMC converter DC transmission system. By adjusting the device parameters, the transmission system can flexibly adapt to different transmission tasks without requiring adjustments to control parameters, effectively improving the stability of the DC transmission system. Attached Figure Description
[0016] To more clearly illustrate the technical solution of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.
[0017] Figure 1 This is a flowchart illustrating an embodiment of the configuration method for a DRU-MMC converter DC transmission system provided by the present invention. Figure 2 This is a schematic diagram of one embodiment of the configuration device for the DRU-MMC converter DC transmission system provided by the present invention. Detailed Implementation
[0018] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.
[0019] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.
[0020] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.
[0021] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.
[0022] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.
[0023] In the description of the embodiments of this application, the term "multiple" refers to two or more (including two), similarly, "multiple sets" refers to two or more (including two sets), and "multiple pieces" refers to two or more (including two pieces).
[0024] In the description of the embodiments of this application, unless otherwise expressly specified and limited, technical terms such as "installation," "connection," "joining," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. For those skilled in the art, the specific meaning of the above terms in the embodiments of this application can be understood according to the specific circumstances.
[0025] See Figure 1To address the problem of poor stability in existing DC transmission systems, an embodiment of the present invention provides a configuration method for a DRU-MMC converter DC transmission system. This method includes steps 101 to 106, each step of which is detailed below: Step 101: Obtain DRU AC data, MMC inverter side operating condition data, grid rated angular frequency, and auxiliary converter electrical performance data of the DRU-MMC converter DC transmission system.
[0026] In this embodiment of the invention, the offshore side of the DRU-MMC converter DC transmission system employs a diode rectifier unit (DRU), while the onshore side uses a modular multilevel converter (MMC). This provides excellent waveform quality and scalability, enabling stable control of the AC power grid. The operating principle of the DRU-MMC converter DC transmission system is as follows: After passing through a step-up substation, the offshore wind turbines transmit power to the offshore platform via collector lines. On the platform, the power is uniformly connected to the DRU converter for rectification into DC, and then transmitted to the onshore substation via a high-voltage DC cable. The MMC converter then inverts the DC power to AC and connects it to the power grid.
[0027] Because the DRU structure of the DRU-MMC converter DC transmission system uses an uncontrolled diode bridge, it lacks parameter regulation capabilities, cannot control the DC voltage, and cannot provide reactive power or voltage support during grid connection faults. When offshore wind farms adopt grid-linked control, the voltage stability and dynamic response capability of the entire system depend entirely on the regulation capability of the onshore MMC, and offshore wind farms cannot perform black starts independently. Therefore, it is necessary to develop a configuration method for the DRU-MMC converter DC transmission system to flexibly adapt to different transmission tasks.
[0028] In this embodiment of the invention, by acquiring the structural parameters of the DRU-MMC converter DC transmission system, the parameters of each component in the DRU-MMC converter DC transmission system can be calculated. Specifically, by acquiring the DRU AC data, MMC inverter-side operating condition data, grid rated angular frequency, and auxiliary converter electrical performance data of the DRU-MMC converter DC transmission system, the parameters of the DRU rectifier can be determined based on the DRU AC data, the parameters of the MMC inverter side can be determined based on the preset number of MMC inverter-side bridge arm sub-modules, the parameters of the bridge arm reactors can be determined based on the grid rated angular frequency, and the parameters of the auxiliary converter can be determined based on the auxiliary converter electrical performance data. This allows for the configuration of appropriate DRU rectifiers, MMC inverter-side components, bridge arm reactors, and auxiliary converters into the DRU-MMC converter DC transmission system.
[0029] The DRU AC data includes the active power input to the DRU via the AC bus, the reactive power input to the DRU via the AC bus, and the DRU AC side input base frequency voltage. The MMC inverter side operating data includes the active power input to the MMC inverter and the reactive power input to the MMC inverter. The auxiliary converter electrical performance data includes the DC voltage level of the auxiliary single-bridge arm series power module, the rated capacity of the converter, the power frequency angular frequency, the DC side reference voltage, and the preset maximum voltage fluctuation rate.
[0030] Step 102: Determine the DRU rectifier parameters based on the DRU electrical characteristics of the DRU rectifier and the DRU AC data; wherein the DRU rectifier parameters include the steady-state electrical characteristic parameters of the DRU rectifier and the number of diodes required for the DRU.
[0031] As a preferred embodiment, the DRU rectifier parameters are determined based on the DRU electrical characteristics and the DRU AC data, including: Based on the DRU rectifier topology in the DRU-MMC converter DC transmission system, the DRU electrical characteristics of the DRU rectifier are determined. A steady-state mathematical model of the DRU rectifier is constructed based on the electrical characteristics of the DRU. Based on the active power, reactive power, and AC-side input fundamental frequency voltage of the DRU from the AC data of the DRU, the steady-state mathematical model is solved to obtain the steady-state electrical characteristic parameters of the DRU rectifier; wherein, the steady-state electrical characteristic parameters include the DC voltage of the DRU output side, the DC current of the DRU output side, the AC-side input fundamental frequency current of the DRU, the AC-side power factor angle of the DRU, and the commutation overlap angle. Based on the rated voltage of the DRU AC side in the DRU AC data, as well as the rated voltage and preset voltage safety margin factor of the preset diodes, calculate the number of diodes required for the DRU.
[0032] In this embodiment of the invention, by constructing a steady-state mathematical model of the DRU rectifier, a mapping relationship between DRU AC data and steady-state electrical characteristic parameters can be established. Therefore, by solving the steady-state mathematical model based on the DRU AC data, steady-state electrical characteristic parameters including the DRU output-side DC voltage, DRU output-side DC current, DRU AC-side input fundamental frequency current, DRU AC-side power factor angle, and commutation overlap angle can be obtained. The number of diodes required for the DRU is calculated based on the DRU AC-side rated voltage in the DRU AC data, as well as the rated voltage and preset voltage safety margin factor of the preset diodes in the specific power transmission task.
[0033] Specifically, when constructing the steady-state mathematical model of the DRU rectifier, only the influence of the AC side fundamental frequency component and the DC side DC component is considered. In this case, the DRU rectifier on the DC side can be equivalently represented as a controlled voltage source with internal resistance, and its DC side external characteristics can be expressed as: In the formula, This refers to the DC voltage on the output side of the DRU. The voltage transformation ratio of the converter transformer grid / valve side winding; Input base frequency voltage to the AC side of the DRU; This refers to the DC current on the output side of the DRU. This refers to the AC-side commutation reactor of the DRU.
[0034] Ignoring converter and converter transformer operating losses, the active power input to the DRU from the AC bus is... With the active power output of the DRU DC side Since they are equal, the base frequency current I input on the AC side of the DRU can be obtained. ac for: The commutation process of a DRU rectifier consumes reactive power, and the power factor angle on the AC side of the DRU is... Size and commutation overlap angle The relationship between the two can be expressed as follows: In the formula, The power factor angle on the AC side of the DRU; The reactive power input to the DRU on the AC bus; The active power input to the DRU for the AC bus; This refers to the commutation overlap angle; The commutation overlap angle is: In the formula, It is direct current; This refers to the leakage reactance of the converter transformer.
[0035] Based on the above formula, a steady-state mathematical model of the DRU suitable for analyzing the operating characteristics of AC / DC transmission systems was constructed. By obtaining the AC data of the DRU and solving the above model, steady-state electrical characteristic parameters including the DC voltage on the output side of the DRU, the DC current on the output side of the DRU, the input fundamental frequency current on the AC side of the DRU, the power factor angle on the AC side of the DRU, and the commutation overlap angle can be calculated.
[0036] As a preferred embodiment, based on the DRU AC side rated voltage in the DRU AC data, and the rated voltage and preset voltage safety margin factor of the preset diodes, the required number of diodes for the DRU is calculated, including: In the formula, The number of diodes required for the DRU; This refers to the rated voltage on the AC side of the DRU. This is the preset rated voltage of the diode; This is the preset voltage safety margin factor. Among them, the rated reverse voltage peak value of the DRU converter valve... DRU AC side rated voltage and DC side rated voltage There is a relationship between them: .
[0037] As a preferred embodiment, the DRU rectifier parameters also include the rated on-state current constraint of the diodes required by the DRU, which is determined using the following formula: Based on the alternating conduction characteristics of the DRU converter valve, the maximum effective value of the bridge arm current flowing through the DRU converter valve during normal operation is... It can be calculated based on the rated current of the DC side of the DRU: In the formula, This is the effective value of the maximum bridge arm current of the DRU converter valve; This refers to the rated current on the DC side of the DRU. When selecting high-power diodes for series connection, the constraint of bridge arm current stress needs to be considered. Therefore, based on the effective value of the maximum bridge arm current and the preset current safety margin coefficient, the rated on-state current constraint of the diode required for the DRU can be determined as follows: In the formula, This is the rated on-state current; This is the preset current safety margin factor.
[0038] Step 103: Calculate the MMC inverter-side parameters based on the DRU AC data and the MMC inverter-side operating condition data; wherein the MMC inverter-side parameters include the bridge arm submodule capacitance value.
[0039] As a preferred embodiment, the MMC inverter-side parameters are calculated based on the DRU AC data and the MMC inverter-side operating condition data, including: The DC voltage on the DRU output side is divided by the preset number of bridge arm sub-modules on the MMC inverter side to calculate the capacitor voltage of the bridge arm module. Based on the active power and reactive power of the MMC inverter side in the MMC inverter side operating condition data, calculate the apparent power of the DRU AC side. Based on the preset MMC inverter-side capacitor voltage fluctuation rate, preset MMC modulation ratio, apparent power of the DRU AC side, preset number of bridge arm sub-modules of the MMC inverter side, MMC angular frequency on the power frequency side, and capacitor voltage of the bridge arm sub-module, the capacitance value of the bridge arm module is calculated, and the capacitance value of the bridge arm module is determined as the MMC inverter-side parameter. The capacitance value of the bridge arm submodule is calculated using the following formula: In the formula, The preset MMC inverter-side capacitor voltage fluctuation rate; The power rating is for the AC side of the DRU; The preset MMC modulation ratio; The preset number of MMC inverter-side bridge arm sub-modules; The MMC angular frequency on the power frequency side; This refers to the capacitor voltage of the bridge arm submodule; This refers to the capacitance value of the bridge arm submodule.
[0040] In this embodiment of the invention, the MMC inverter-side parameters include the bridge arm submodule capacitance values. Only after determining the bridge arm submodule capacitance values can the bridge arm submodules on the MMC inverter side be configured. Calculating the bridge arm submodule capacitance values first requires calculating the bridge arm submodule capacitor voltage. The bridge arm submodule capacitor voltage is calculated based on the DRU output side DC voltage in the calculated DRU rectifier parameters and the preset number of MMC inverter-side bridge arm submodules. Specifically: In the formula, This refers to the capacitor voltage of the bridge arm submodule; This refers to the DC voltage on the output side of the DRU. The preset number of MMC inverter side bridge arm sub-modules.
[0041] In this embodiment of the invention, the expression for the change of the average capacitor voltage of all bridge arm submodules over time is as follows: In the formula, Let be the capacitor voltage of the bridge arm submodule at time t; This represents the DC component of the capacitor voltage of the bridge arm submodule; This represents the fluctuation component of the capacitor voltage of the bridge arm submodule.
[0042] To calculate the deviation of the capacitor voltage of the bridge arm submodule from its DC component The fluctuation range, using Indicates the amplitude of the fluctuation component and The ratio of the two is called the capacitor voltage fluctuation rate, that is: in, It is related to system parameters and operating conditions, because when the MMC generates reactive power at full capacity... The maximum value is obtained, therefore the calculation is performed. The operating condition should meet the full-capacity reactive power generation condition, that is... Operating conditions. Reference bridge arm submodule capacitor. The relationship between energy storage and voltage, according to The maximum change in energy storage can be used to deduce the fluctuation rate of capacitor voltage.
[0043] In the derivation, the simplified conditions of the bridge arm voltage and bridge arm current being the DC component plus the fundamental component are used. Under these simplified conditions, the following can be derived: The expression for the maximum change in energy storage is: In the formula, for The maximum change in energy storage; The power rating is for the AC side of the DRU; The preset MMC modulation ratio; The preset number of MMC inverter-side bridge arm sub-modules; The MMC angular frequency on the power frequency side; This is the power factor angle on the AC side of the DRU.
[0044] Among them, the DRU AC side is viewed in terms of power. Active power of MMC inverter side based on operating condition data of MMC inverter side and reactive power of MMC inverter side calculate: In the formula, The power rating is for the AC side of the DRU; This refers to the active power on the MMC inverter side. This refers to the reactive power on the MMC inverter side.
[0045] The maximum energy storage of the bridge hip module capacitor voltage and minimum energy storage The capacitor voltage can be represented by its maximum and minimum values. Assuming that the fluctuations in the capacitor voltage from its average value are equal, then: Another expression for the maximum change in energy storage of the bridge hip module is: Therefore, the voltage fluctuation rate of the inverter-side capacitor in the MMC can be obtained. The expression is: Due to calculation The operating condition should meet the full-capacity reactive power generation condition, that is... Under these operating conditions, the voltage fluctuation rate of the inverter-side capacitor in the aforementioned MMC is... The expression can be modified as follows: Based on the above MMC inverter-side capacitor voltage fluctuation rate The revised expression, after obtaining the preset MMC inverter-side capacitor voltage fluctuation rate, can calculate the bridge arm submodule capacitance value by combining the known preset MMC modulation ratio, DRU AC-side apparent power, preset number of MMC inverter-side bridge arm submodules, power frequency-side MMC angular frequency, and bridge arm submodule capacitor voltage. Therefore, the bridge arm submodules on the MMC inverter side can be configured based on the calculated bridge arm submodule capacitance values.
[0046] Step 104: Based on the system negative sequence constraint of the DRU-MMC converter DC transmission system and the rated angular frequency of the power grid, calculate the arm reactor parameters; wherein, the arm reactor parameters include the arm reactance and the arm reactor inductance value.
[0047] As a preferred embodiment, based on the system negative sequence constraint of the DRU-MMC converter DC transmission system and the rated angular frequency of the power grid, the parameters of the bridge arm reactor are calculated, including: Based on the system negative sequence constraint of the DRU-MMC converter DC transmission system, the range of negative sequence phase angle values is determined. Based on the MMC arm reactance phase correlation formula and the range of negative sequence phase angle values, the range of values for the MMC inverter side arm reactance is determined. Determine the series resonant angular frequency of the phase unit based on the rated angular frequency of the power grid; The inductance value of the bridge arm reactor is calculated based on the series resonant angular frequency of the phase unit, the preset number of bridge arm sub-modules on the MMC inverter side, and the capacitance value of the bridge arm module. The inductance value of the bridge arm reactor is calculated using the following formula: In the formula, The resonant angular frequency of the phase unit in series; The preset number of MMC inverter-side bridge arm sub-modules; The capacitance value of the bridge arm submodule; This represents the inductance value of the bridge arm reactor.
[0048] In this embodiment of the invention, the bridge arm reactor is a part of the connecting reactor. Primarily based on the MMC's ability to suppress fundamental negative sequence current, and considering the constraint between the grid background fundamental negative sequence voltage and the rated voltage (e.g., the grid background fundamental negative sequence voltage is 1.5% of the rated voltage), the system negative sequence constraint of the DRU-MMC converter DC transmission system can be determined (e.g., the negative sequence current flowing through the connector is no greater than 5%-10% of the MMC's rated current). Based on the above formula, the negative sequence phase angle can be determined. The range of values for: .
[0049] By analyzing the equivalent circuit of the MMC topology and establishing the power transfer relationship, the phase correlation formula of the MMC arm reactance can be derived: Combining the above negative sequence phase angle From the range of values, we can derive the range of values for the arm reactance on the MMC inverter side: .
[0050] In this embodiment of the invention, the inductance value of the bridge arm reactor plays a decisive role in determining its value. The bridge arm reactor must avoid the second harmonic circulating current resonant frequency. The principle for selecting the bridge arm reactor value is to keep the series resonant frequency of the phase unit as far away as possible from the second harmonic circulating current resonant frequency. Typically, the series resonant frequency of the phase unit... The economically reasonable value is one times the rated angular frequency of the power grid. It is nearby, so it can be considered as the series resonant angular frequency. The value is equivalent to the rated angular frequency of the power grid. Therefore, when obtaining the rated angular frequency of the power grid, the series resonant angular frequency can be derived. The value of . Given the known series resonant angular frequency of the phase unit. Preset the number N of MMC inverter-side bridge arm sub-modules and the capacitance value of the bridge arm modules. Under the premise that it can be done through formula Calculate the inductance value of the bridge arm reactor .
[0051] Step 105: Calculate the auxiliary converter parameters based on the auxiliary converter electrical performance data; wherein, the auxiliary converter parameters include the number of series power modules in the auxiliary single-arm bridge, the auxiliary capacitor voltage constraint, and the auxiliary arm inductance constraint.
[0052] As a preferred embodiment, the auxiliary converter parameters are calculated based on the auxiliary converter electrical performance data, including: The number of auxiliary single-bridge arm series power modules is calculated by dividing the DC voltage on the output side of the DRU by the DC voltage level of the auxiliary single-bridge arm series power module in the electrical performance data of the auxiliary converter. The auxiliary capacitor voltage constraint is determined based on the converter rated capacity, power frequency angular frequency, DC side reference voltage, preset maximum voltage fluctuation rate, and the number of series power modules of the auxiliary single bridge arm in the auxiliary converter electrical performance data. The auxiliary capacitor voltage constraint is as follows: In the formula, For auxiliary capacitor voltage; To assist in increasing the number of series power modules in a single bridge arm; This refers to the rated capacity of the converter; It is the power frequency angular frequency; The preset maximum voltage fluctuation rate; This is the DC-side reference voltage; The auxiliary bridge arm inductance constraint is determined based on the number of series power modules in the auxiliary single bridge arm, the power frequency angular frequency, and the auxiliary capacitor voltage. The auxiliary bridge arm inductance constraint is as follows: In the formula, To assist the bridge arm inductor.
[0053] In this embodiment of the invention, for a series-type auxiliary converter, the DC voltage level of the auxiliary single-arm series power module needs to match the selected IGBT voltage level, thereby determining the required number of auxiliary single-arm series power modules: In the formula, To assist in increasing the number of series power modules in a single bridge arm; This refers to the DC voltage on the output side of the DRU. To assist the DC voltage level of the single-bridge arm series power module.
[0054] Since the DC capacitor of the power module carries AC current, voltage fluctuations will occur. In order to suppress voltage fluctuations, it is necessary to determine the voltage constraint of the auxiliary capacitor and thus select a suitable capacitor.
[0055] First, the maximum change in energy of the submodule capacitor is: In the formula, This represents the maximum change in the energy of the submodule capacitor. This refers to the rated capacity of the converter; The preset MMC modulation ratio; It is the power frequency angular frequency; The power factor.
[0056] Assuming the average submodule voltage fluctuation rate is ε, and we calculate this with m=1, the following relationship holds: In the formula, The average voltage of the submodule; This is the voltage of the auxiliary capacitor.
[0057] Combining the above two equations, we get: Considering that the voltage fluctuation of the submodule capacitor is the largest under a unit power factor, the maximum voltage fluctuation rate is: According to the above formula, since the DC side voltage is N times the average value of the submodule capacitor voltage, the auxiliary capacitor voltage constraint can be determined as follows: In the formula, For auxiliary capacitor voltage; The preset maximum voltage fluctuation rate; This is the DC-side reference voltage.
[0058] In this embodiment of the invention, the selection of the parameters of the arm reactor affects the converter's response speed, the harmonic level at the grid connection point, the converter's reactive power input capability, and the internal circulating current value of the converter. Furthermore, the selection of the arm reactor's reactance should be coordinated with the selection of the connecting transformer's leakage reactance to ensure that the transformer's leakage reactance is within a reasonable range. For the arm reactor parameters, a larger valve reactance results in a smaller maximum reactive power output. Under the condition of satisfying the corresponding reactive power output, the upper limit value of the valve reactance can be calculated. The arm circulating current (around 30%) has little impact on the arm current, mainly affecting the distortion and peak value of the arm current. Moreover, there are usually circulating current suppression control algorithms to weaken the influence of the circulating current. The lower limit value of the valve reactance can be calculated. The upper limit value of the valve reactance can be calculated based on the current dynamic response tracking speed; however, this upper limit value is usually quite large, so it has little impact on the selection of the valve reactance. The main consideration is that each circulating current of the MMC has a resonant point, and the frequency of the resonant point decreases as the harmonic order k increases. To ensure stable converter operation, the system frequency ω should be as far away as possible from the resonant frequencies of the circulating currents in each arm. It is easy to deduce that as long as the system's rated operating frequency is greater than the characteristic frequency of the second harmonic circulating current resonance when the modulation ratio m equals 1, all resonant points can be avoided. The resonant points can be calculated using the following formula: In the formula, The resonant angular frequency of the bridge arm circulating current; The number of power modules connected in series to assist a single bridge arm; m is the preset MMC modulation ratio; For harmonic order; For auxiliary capacitor voltage; To assist the bridge arm inductor.
[0059] ω s >ω resh Substituting m=1 into the above equation, we can obtain the auxiliary bridge arm inductance constraint: .
[0060] Step 106: Based on the DRU rectifier parameters, the MMC inverter side parameters, the bridge arm reactor parameters, and the auxiliary converter parameters, configure each device in the DRU-MMC converter DC transmission system to form an optimized DRU-MMC converter DC transmission system.
[0061] In this embodiment of the invention, after obtaining the DRU rectifier parameters, MMC inverter-side parameters, bridge arm reactor parameters, and auxiliary converter parameters according to the above parameter calculation method, the DRU rectifier is configured in the DRU-MMC converter DC transmission system based on the DRU rectifier parameters, the MMC inverter-side devices are configured in the DRU-MMC converter DC transmission system based on the MMC inverter-side parameters, the bridge arm reactors are configured in the DRU-MMC converter DC transmission system based on the bridge arm reactor parameters, and the auxiliary converters are configured in the DRU-MMC converter DC transmission system based on the auxiliary converter parameters, thereby forming an optimized DRU-MMC converter DC transmission system so that the optimized DRU-MMC converter DC transmission system can flexibly adapt to different power transmission tasks.
[0062] As a preferred embodiment, after configuring the various components within the DRU-MMC converter DC transmission system based on the DRU rectifier parameters, the MMC inverter-side parameters, the bridge arm reactor parameters, and the auxiliary converter parameters to form an optimized DRU-MMC converter DC transmission system, the system further includes: When the wind farm adopts grid-connected control, the auxiliary converter of the optimized DRU-MMC converter DC transmission system provides voltage support for the wind farm during the black start phase, controls the grid connection point voltage and frequency, and provides commutation AC voltage for the DRU rectifier. The DRU rectifier, which controls the optimized DRU-MMC converter DC transmission system, rectifies the AC power output from the wind farm into DC power based on the commutation AC voltage, and transmits the DC power to the MMC inverter side through a DC line. The optimized DRU-MMC converter DC transmission system controls the MMC inverter side to invert the DC power into standard AC power, and then connects the standard AC power into the onshore power grid.
[0063] In this embodiment of the invention, after the optimized DRU-MMC converter DC transmission system is formed, grid-connected control is adopted at the wind farm, i.e., active / reactive power is controlled. Control of the grid connection point is achieved by controlling the active and reactive power at the wind farm's grid connection point. The auxiliary converter provides voltage support for the wind farm during the black start phase, controls the grid connection point voltage and frequency, and provides commutated AC voltage to the DRU rectifier. The DRU rectifier rectifies the AC output from the wind farm into DC based on the commutated AC voltage and transmits the DC to the MMC inverter side via a DC line. The MMC inverter side inverts the DC into standard AC and connects the standard AC to the onshore power grid. The DRU rectifier, the MMC inverter side, and the auxiliary converter work together to maintain system power balance.
[0064] Implementing the above embodiments has the following effects: This invention provides a configuration method for a DRU-MMC converter DC transmission system. The method involves acquiring DRU AC data, MMC inverter-side operating condition data, grid rated angular frequency, and auxiliary converter electrical performance data of the DRU-MMC converter DC transmission system. Based on the DRU electrical characteristics and DRU AC data, DRU rectifier parameters are determined. MMC inverter-side parameters are calculated based on the DRU AC data and MMC inverter-side operating condition data. Arm reactor parameters are calculated based on the system negative sequence constraint and grid rated angular frequency of the DRU-MMC converter DC transmission system. Auxiliary converter parameters are calculated based on the auxiliary converter electrical performance data. Finally, based on the DRU rectifier parameters, MMC inverter-side parameters, arm reactor parameters, and auxiliary converter parameters, the various components within the DRU-MMC converter DC transmission system are configured to form an optimized DRU-MMC converter DC transmission system. This invention calculates the parameters of the DRU rectifier, MMC inverter side, bridge arm reactor, and auxiliary converter based on real-time system electrical parameter data of the DRU-MMC converter DC transmission system. This allows for the configuration of appropriate DRU rectifiers, MMC inverter side devices, bridge arm reactors, and auxiliary converters within the DRU-MMC converter DC transmission system. By adjusting the device parameters, the transmission system can flexibly adapt to different transmission tasks without requiring adjustments to control parameters, effectively improving the stability of the DC transmission system.
[0065] like Figure 2 As shown, based on the above method embodiments, corresponding apparatus embodiments are provided; One embodiment of the present invention provides a configuration device for a DRU-MMC converter DC transmission system, comprising: a data acquisition module, a DRU rectifier parameter determination module, an MMC inverter side parameter determination module, a bridge arm reactor parameter determination module, an auxiliary converter parameter determination module, and a device configuration module; The data acquisition module is used to acquire DRU AC data, MMC inverter side operating condition data, grid rated angular frequency, and auxiliary converter electrical performance data of the DRU-MMC converter DC transmission system. The DRU rectifier parameter determination module is used to determine the DRU rectifier parameters based on the DRU electrical characteristics and the DRU AC data; wherein, the DRU rectifier parameters include the steady-state electrical characteristic parameters of the DRU rectifier and the number of diodes required for the DRU; The MMC inverter-side parameter determination module is used to calculate the MMC inverter-side parameters based on the DRU AC data and the MMC inverter-side operating condition data; wherein, the MMC inverter-side parameters include the bridge arm submodule capacitance value; The arm reactor parameter determination module is used to calculate the arm reactor parameters based on the system negative sequence constraint of the DRU-MMC converter DC transmission system and the rated angular frequency of the power grid; wherein, the arm reactor parameters include the arm reactor and the arm reactor inductance value; The auxiliary converter parameter determination module is used to calculate the auxiliary converter parameters based on the auxiliary converter electrical performance data; wherein, the auxiliary converter parameters include the number of series power modules in the auxiliary single bridge arm, the auxiliary capacitor voltage constraint, and the auxiliary bridge arm inductance constraint; The device configuration module is used to configure each device in the DRU-MMC converter DC transmission system based on the parameters of the DRU rectifier, the parameters of the MMC inverter side, the parameters of the bridge arm reactor, and the parameters of the auxiliary converter, so as to form an optimized DRU-MMC converter DC transmission system.
[0066] It is understood that the above-described device embodiments correspond to the method embodiments of the present invention, and can implement the configuration method of the DRU-MMC converter DC transmission system provided by any of the above-described method embodiments of the present invention.
[0067] It should be noted that the device embodiments described above are merely illustrative, and some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs. Furthermore, in the accompanying drawings of the device embodiments provided by this invention, the connection relationships between modules indicate that they have communication connections, which can specifically be implemented as one or more communication buses or signal lines. Those skilled in the art can understand and implement this without any creative effort.
[0068] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the scope of protection of the present invention. In particular, it should be noted that any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention for those skilled in the art.
Claims
1. A configuration method for a DRU-MMC converter DC transmission system, characterized in that, include: Acquire DRU AC data, MMC inverter-side operating condition data, grid rated angular frequency, and auxiliary converter electrical performance data of the DRU-MMC converter DC transmission system; Based on the electrical characteristics of the DRU rectifier and the AC data of the DRU, the parameters of the DRU rectifier are determined; wherein, the parameters of the DRU rectifier include the steady-state electrical characteristic parameters of the DRU rectifier and the number of diodes required for the DRU; Based on the DRU AC data and the MMC inverter-side operating condition data, the MMC inverter-side parameters are calculated; wherein, the MMC inverter-side parameters include the bridge arm submodule capacitance value; Based on the system negative sequence constraint of the DRU-MMC converter DC transmission system and the rated angular frequency of the power grid, the parameters of the bridge arm reactor are calculated; wherein, the parameters of the bridge arm reactor include the bridge arm reactance and the bridge arm reactor inductance value; The auxiliary converter parameters are calculated based on the electrical performance data of the auxiliary converter; wherein, the auxiliary converter parameters include the number of series power modules in the auxiliary single bridge arm, the auxiliary capacitor voltage constraint, and the auxiliary bridge arm inductance constraint; Based on the parameters of the DRU rectifier, the parameters of the MMC inverter side, the parameters of the bridge arm reactor, and the parameters of the auxiliary converter, the components in the DRU-MMC converter DC transmission system are configured to form an optimized DRU-MMC converter DC transmission system.
2. The configuration method of the DRU-MMC converter DC transmission system according to claim 1, characterized in that, The step of determining the DRU rectifier parameters based on the DRU electrical characteristics and the DRU AC data includes: Based on the DRU rectifier topology in the DRU-MMC converter DC transmission system, the DRU electrical characteristics of the DRU rectifier are determined. A steady-state mathematical model of the DRU rectifier is constructed based on the electrical characteristics of the DRU. Based on the active power, reactive power, and AC-side input fundamental frequency voltage of the DRU from the AC data of the DRU, the steady-state mathematical model is solved to obtain the steady-state electrical characteristic parameters of the DRU rectifier; wherein, the steady-state electrical characteristic parameters include the DC voltage of the DRU output side, the DC current of the DRU output side, the AC-side input fundamental frequency current of the DRU, the AC-side power factor angle of the DRU, and the commutation overlap angle. Based on the rated voltage of the DRU AC side in the DRU AC data, as well as the rated voltage and preset voltage safety margin factor of the preset diodes, calculate the number of diodes required for the DRU.
3. The configuration method of the DRU-MMC converter DC transmission system according to claim 2, characterized in that, The steady-state mathematical model of the DRU rectifier is as follows: In the formula, This refers to the DC voltage on the output side of the DRU. The voltage transformation ratio of the converter transformer grid / valve side winding; Input base frequency voltage to the AC side of the DRU; This refers to the DC current on the output side of the DRU. For the commutation reactance on the AC side of the DRU; Input the base frequency current to the AC side of the DRU; The power factor angle on the AC side of the DRU; The reactive power input to the DRU on the AC bus; The active power input to the DRU for the AC bus; This refers to the commutation overlap angle; It is direct current; This refers to the leakage reactance of the converter transformer.
4. The configuration method of the DRU-MMC converter DC transmission system according to claim 3, characterized in that, The calculation of the required number of diodes for the DRU based on the DRU AC side rated voltage in the DRU AC data, and the preset diode rated voltage and preset voltage safety margin factor, includes: In the formula, The number of diodes required for the DRU; This refers to the rated voltage on the AC side of the DRU. This is the preset rated voltage of the diode; This is the preset voltage safety margin factor.
5. The configuration method of the DRU-MMC converter DC transmission system according to claim 4, characterized in that, The calculation of MMC inverter-side parameters based on the DRU AC data and the MMC inverter-side operating condition data includes: The DC voltage on the DRU output side is divided by the preset number of bridge arm sub-modules on the MMC inverter side to calculate the capacitor voltage of the bridge arm module. Based on the active power and reactive power of the MMC inverter side in the MMC inverter side operating condition data, calculate the apparent power of the DRU AC side. Based on the preset MMC inverter-side capacitor voltage fluctuation rate, preset MMC modulation ratio, apparent power of the DRU AC side, preset number of bridge arm sub-modules of the MMC inverter side, MMC angular frequency on the power frequency side, and capacitor voltage of the bridge arm sub-module, the capacitance value of the bridge arm module is calculated, and the capacitance value of the bridge arm module is determined as the MMC inverter-side parameter. The capacitance value of the bridge arm submodule is calculated using the following formula: In the formula, The preset MMC inverter-side capacitor voltage fluctuation rate; The power rating is for the AC side of the DRU; The preset MMC modulation ratio; The preset number of MMC inverter-side bridge arm sub-modules; The MMC angular frequency on the power frequency side; This refers to the capacitor voltage of the bridge arm submodule; This refers to the capacitance value of the bridge arm submodule.
6. The configuration method of the DRU-MMC converter DC transmission system according to claim 5, characterized in that, The calculation of bridge arm reactor parameters based on the system negative sequence constraints of the DRU-MMC converter DC transmission system and the rated angular frequency of the power grid includes: Based on the system negative sequence constraint of the DRU-MMC converter DC transmission system, the range of negative sequence phase angle values is determined. Based on the MMC arm reactance phase correlation formula and the range of negative sequence phase angle values, the range of values for the MMC inverter side arm reactance is determined. Determine the series resonant angular frequency of the phase unit based on the rated angular frequency of the power grid; The inductance value of the bridge arm reactor is calculated based on the series resonant angular frequency of the phase unit, the preset number of bridge arm sub-modules on the MMC inverter side, and the capacitance value of the bridge arm module. The inductance value of the bridge arm reactor is calculated using the following formula: In the formula, The resonant angular frequency of the phase unit in series; The preset number of MMC inverter-side bridge arm sub-modules; The capacitance value of the bridge arm submodule; This represents the inductance value of the bridge arm reactor.
7. The configuration method of the DRU-MMC converter DC transmission system according to claim 6, characterized in that, The calculation of auxiliary converter parameters based on the auxiliary converter electrical performance data includes: The number of auxiliary single-bridge arm series power modules is calculated by dividing the DC voltage on the output side of the DRU by the DC voltage level of the auxiliary single-bridge arm series power module in the electrical performance data of the auxiliary converter. The auxiliary capacitor voltage constraint is determined based on the converter rated capacity, power frequency angular frequency, DC side reference voltage, preset maximum voltage fluctuation rate, and the number of series power modules of the auxiliary single bridge arm in the auxiliary converter electrical performance data. The auxiliary capacitor voltage constraint is as follows: In the formula, For auxiliary capacitor voltage; To assist in increasing the number of series power modules in a single bridge arm; This refers to the rated capacity of the converter; It is the power frequency angular frequency; The preset maximum voltage fluctuation rate; This is the DC-side reference voltage; The auxiliary bridge arm inductance constraint is determined based on the number of series power modules in the auxiliary single bridge arm, the power frequency angular frequency, and the auxiliary capacitor voltage. The auxiliary bridge arm inductance constraint is as follows: In the formula, To assist the bridge arm inductor.
8. The configuration method of the DRU-MMC converter DC transmission system according to claim 7, characterized in that, The DRU rectifier parameters also include the rated on-state current constraint of the diodes required by the DRU, which is determined using the following formula: Based on the rated DC-side current of the DRU and the alternating conduction characteristics of the DRU converter valve in the DRU rectifier, the maximum effective value of the bridge arm current of the DRU converter valve is calculated using the following formula: In the formula, This is the effective value of the maximum bridge arm current of the DRU converter valve; This refers to the rated current on the DC side of the DRU. Based on the maximum effective value of the bridge arm current and the preset current safety margin coefficient, the rated on-state current constraint of the diode required for the DRU is calculated using the following formula: In the formula, This is the rated on-state current; This is the preset current safety margin factor.
9. The configuration method of the DRU-MMC converter DC transmission system according to claim 8, characterized in that, After configuring the various components within the DRU-MMC converter DC transmission system based on the DRU rectifier parameters, the MMC inverter-side parameters, the bridge arm reactor parameters, and the auxiliary converter parameters to form an optimized DRU-MMC converter DC transmission system, the process further includes: When the wind farm adopts grid-connected control, the auxiliary converter of the optimized DRU-MMC converter DC transmission system provides voltage support for the wind farm during the black start phase, controls the grid connection point voltage and frequency, and provides commutation AC voltage for the DRU rectifier. The DRU rectifier, which controls the optimized DRU-MMC converter DC transmission system, rectifies the AC power output from the wind farm into DC power based on the commutation AC voltage, and transmits the DC power to the MMC inverter side through a DC line. The optimized DRU-MMC converter DC transmission system controls the MMC inverter side to invert the DC power into standard AC power, and then connects the standard AC power into the onshore power grid.
10. A configuration device for a DRU-MMC converter DC transmission system, characterized in that, include: Data acquisition module, DRU rectifier parameter determination module, MMC inverter side parameter determination module, bridge arm reactor parameter determination module, auxiliary converter parameter determination module and device configuration module; The data acquisition module is used to acquire DRU AC data, MMC inverter side operating condition data, grid rated angular frequency and auxiliary converter electrical performance data of the DRU-MMC converter DC transmission system. The DRU rectifier parameter determination module is used to determine the DRU rectifier parameters based on the DRU electrical characteristics and the DRU AC data; wherein, the DRU rectifier parameters include the steady-state electrical characteristic parameters of the DRU rectifier and the number of diodes required for the DRU; The MMC inverter-side parameter determination module is used to calculate the MMC inverter-side parameters based on the DRU AC data and the MMC inverter-side operating condition data; wherein, the MMC inverter-side parameters include the bridge arm submodule capacitance value; The arm reactor parameter determination module is used to calculate the arm reactor parameters based on the system negative sequence constraint of the DRU-MMC converter DC transmission system and the rated angular frequency of the power grid; wherein, the arm reactor parameters include the arm reactor and the arm reactor inductance value; The auxiliary converter parameter determination module is used to calculate the auxiliary converter parameters based on the auxiliary converter electrical performance data; wherein, the auxiliary converter parameters include the number of series power modules in the auxiliary single bridge arm, the auxiliary capacitor voltage constraint, and the auxiliary bridge arm inductance constraint; The device configuration module is used to configure each device in the DRU-MMC converter DC transmission system based on the DRU rectifier parameters, the MMC inverter side parameters, the bridge arm reactor parameters, and the auxiliary converter parameters, to form an optimized DRU-MMC converter DC transmission system.