Networking control method of full-control composite converter based on droop control

Abstract

The invention provides a droop control-based network construction control method for a full-control composite converter. The converter comprises a port used for being connected to an alternating current power grid, a main body valve and a supporting valve. The method comprises the steps that power grid synchronization information, an alternating current dq axis component, an outer ring voltage reference value of the supporting valve and an inner ring active current reference value of the supporting valve are obtained; determining an inner loop reactive current reference value at least according to the outer loop voltage reference value; determining a first control signal according to the inner ring reactive current reference value, the inner ring active current reference value, the alternating current dq axis component and the power grid synchronization information, and performing inner ring control and outer ring control on the support valve by adopting the first control signal; and determining a second control signal at least according to the power grid synchronization information, and performing reactive power control on the main body valve by adopting the second control signal. According to the method, the operation stability of the converter can be improved.

Description

Technical Field

[0001] This application relates to the field of DC power transmission, and more specifically, to a grid control method for a fully controlled composite converter based on droop control, a grid control device for a fully controlled composite converter based on droop control, and a DC power transmission system. Background Technology

[0002] Ultra-high voltage direct current (UHVDC) transmission, with its unique advantages such as large-capacity transmission, long-distance coverage, low loss, and high utilization rate of transmission corridors, has become a key technology for balancing the contradiction between energy resource distribution and load demand. As a core component of high-voltage direct current (HVDC) transmission projects, the performance of UHVDC converters directly affects the efficiency of power transmission and the reliability of the system. However, traditional DC converters have revealed some significant limitations when facing large-scale integration of new energy sources. With the increasing penetration rate of new energy sources, the short-circuit ratio of the power grid gradually decreases, leading to a weakening of the grid's dynamic reactive power support capacity. Furthermore, in extreme cases, such as islanded operation, traditional converters struggle to independently establish stable AC voltage and frequency, thus affecting the feasibility of large-scale transmission and grid connection of new energy sources.

[0003] Therefore, there is an urgent need for a grid control method for fully controlled composite converters based on droop control to improve the stability of converter operation. Summary of the Invention

[0004] The main objective of this application is to provide a grid control method for a fully controlled composite converter based on droop control, a grid control device for a fully controlled composite converter based on droop control, and a DC transmission system, so as to at least solve the problem of how to improve the stability of converter operation in the prior art.

[0005] To achieve the above objectives, according to one aspect of this application, a grid control method for a fully controlled composite converter based on droop control is provided. The fully controlled composite converter includes a port for connecting to an AC power grid, a main valve, and a support valve. The method includes: acquiring grid synchronization information, the dq-axis component of the AC current, an outer-loop voltage reference value of the support valve, and an inner-loop active current reference value of the support valve. The grid synchronization information is the power synchronization phase angle of the AC power grid. The dq-axis component of the AC current includes the d-axis component and the q-axis component of the AC current in a two-phase rotating coordinate system. The outer-loop voltage reference value is a reference value of the bus AC voltage. The inner-loop active current reference value is... The reference value of the d-axis component of the alternating current in a two-phase rotating coordinate system; the reference value of the inner loop reactive current is determined based at least on the outer loop voltage reference value, wherein the reference value of the inner loop reactive current is the reference value of the q-axis component of the alternating current in a two-phase rotating coordinate system; a first control signal is determined based on the inner loop reactive current reference value, the inner loop active current reference value, the dq-axis component of the alternating current, and the grid synchronization information, and the first control signal is used to control the support valve to adjust the inner loop reactive current and inner loop active current of the support valve; a second control signal is determined based at least on the grid synchronization information, and the second control signal is used to control the main valve to adjust the active power and reactive power of the main valve.

[0006] Optionally, obtaining power grid synchronization information includes: obtaining a first active power, a first active power reference value, and the rated angular frequency of the AC power grid, wherein the first active power is the active power of the AC power grid, and the first active power reference value is the reference value of the first active power; calculating the difference between the first active power reference value and the first active power to obtain a first difference; performing low-pass filtering on the first difference to obtain a first filtered value, and calculating the product of the first filtered value and the active branch droop coefficient to obtain a first parameter; calculating the sum of the first parameter and the rated angular frequency to obtain a second parameter; and inputting the second parameter into an integrator to obtain the power synchronization phase.

[0007] Optionally, obtaining the outer loop voltage reference value of the aforementioned support valve includes: obtaining a first reactive power, a first reactive power reference value, and the rated voltage amplitude of the aforementioned AC power grid, wherein the first reactive power is the reactive power of the aforementioned AC power grid, and the first reactive power reference value is the reference value of the aforementioned first reactive power; calculating the difference between the aforementioned first reactive power reference value and the aforementioned first reactive power to obtain a second difference; performing low-pass filtering on the aforementioned second difference to obtain a second filtered value, and calculating the product of the aforementioned second filtered value and the reactive power branch droop coefficient to obtain a third parameter; and calculating the sum of the aforementioned third parameter and the aforementioned rated voltage amplitude to obtain the outer loop voltage reference value of the aforementioned support valve.

[0008] Optionally, obtaining the dq-axis component of the AC current includes: obtaining the three-phase AC current of the aforementioned support valve; performing coordinate inverse transformation on the aforementioned three-phase AC current to obtain the aforementioned dq-axis component of the AC current, wherein the aforementioned dq-axis component of the AC current is the dq-axis component of the aforementioned three-phase AC current in a two-phase rotating coordinate system.

[0009] Optionally, the inner loop reactive current reference value is determined based at least on the outer loop voltage reference value, including: obtaining the bus AC voltage and calculating the difference between the outer loop voltage reference value of the support valve and the bus AC voltage to obtain a third difference value; inputting the third difference value to the proportional-integral controller to obtain the inner loop reactive current reference value.

[0010] Optionally, obtaining the inner loop active current reference value of the aforementioned support valve includes: obtaining a second active power and a second active power reference value, wherein the second active power is the active power of the aforementioned support valve, and the second active power reference value is the reference value of the aforementioned second active power; calculating the difference between the aforementioned second active power reference value and the aforementioned second active power to obtain a fourth difference value; and inputting the aforementioned fourth difference value to a proportional-integral controller to obtain the inner loop active current reference value of the aforementioned support valve.

[0011] Optionally, based on the aforementioned inner-loop reactive current reference value, the aforementioned inner-loop active current reference value, the aforementioned dq-axis component of the AC current, and the aforementioned grid synchronization information, a first control signal is determined, including: calculating the difference between the aforementioned inner-loop reactive current reference value and the aforementioned q-axis component of the AC current in a two-phase rotating coordinate system to obtain a fifth difference value; inputting the aforementioned fifth difference value to a proportional-integral controller to obtain a first voltage modulation signal; calculating the difference between the aforementioned inner-loop active current reference value and the aforementioned d-axis component of the AC current in a two-phase rotating coordinate system to obtain a sixth difference value; inputting the aforementioned sixth difference value to a proportional-integral controller to obtain a second voltage modulation signal; performing coordinate inverse transformation processing on the aforementioned first voltage modulation signal and the aforementioned second voltage modulation signal to obtain a voltage sinusoidal modulation signal; and performing nearest-level approximation modulation processing on the aforementioned voltage sinusoidal modulation signal to obtain the aforementioned first control signal.

[0012] Optionally, at least based on the aforementioned power grid synchronization information, a second control signal is determined, including: acquiring the capacitor voltage and second reactive power of the submodule of the support valve, wherein the second reactive power is the reactive power of the support valve; performing negative feedback adjustment on the capacitor voltage of the submodule of the support valve to obtain a first current modulation signal; performing negative feedback adjustment on the second reactive power to obtain a second current modulation signal; performing coordinate inverse transformation on the first current modulation signal and the second current modulation signal to obtain a current sinusoidal modulation signal; and performing pulse width modulation on the current sinusoidal modulation signal to obtain the second control signal.

[0013] Optionally, the capacitor voltage is subjected to negative feedback regulation to obtain a first current modulation signal, including: obtaining a reference value of the capacitor voltage of the sub-module of the support valve, and calculating the difference between the reference value of the capacitor voltage of the sub-module of the support valve and the capacitor voltage of the sub-module of the support valve to obtain a seventh difference; inputting the seventh difference to a proportional-integral controller to obtain the first current modulation signal.

[0014] Optionally, the second reactive power is subjected to negative feedback regulation to obtain a second current modulation signal, including: obtaining a second reactive power reference value, wherein the second reactive power reference value is a reference value of the second reactive power, and calculating the difference between the second reactive power reference value and the second reactive power to obtain an eighth difference value; and inputting the eighth difference value to a proportional-integral controller to obtain the second current modulation signal.

[0015] To achieve the above objectives, according to one aspect of this application, a grid control device for a fully controlled composite converter based on droop control is provided. The fully controlled composite converter includes a port for connecting to an AC power grid, a main valve, and a support valve. The device includes: an acquisition unit for acquiring grid synchronization information, the dq-axis component of the AC current, the outer loop voltage reference value of the support valve, and the inner loop active current reference value of the support valve. The grid synchronization information is the power synchronization phase angle of the AC power grid. The dq-axis component of the AC current includes the d-axis component and the q-axis component of the AC current in a two-phase rotating coordinate system. The outer loop voltage reference value is a reference value of the bus AC voltage. The inner loop active current reference value is the reference value of the AC current in a two-phase rotating coordinate system. The reference value of the d-axis component; the determining unit, used to determine the reference value of the inner loop reactive current based at least on the outer loop voltage reference value, wherein the reference value of the inner loop reactive current is the reference value of the q-axis component of the AC current in the two-phase rotating coordinate system; the first control unit, used to determine the first control signal based on the inner loop reactive current reference value, the inner loop active current reference value, the dq-axis component of the AC current and the grid synchronization information, and use the first control signal to control the support valve to adjust the inner loop reactive current and inner loop active current of the support valve; the second control unit, used to determine the second control signal based at least on the grid synchronization information, and use the second control signal to control the main valve to adjust the active power and reactive power of the main valve.

[0016] According to another aspect of this application, a DC transmission system is provided, including a DC transmission sending end and a DC transmission receiving end, wherein the DC transmission sending end adopts any of the above-mentioned grid control methods for a fully controlled composite converter based on droop control.

[0017] This application provides a grid control method for a fully controlled composite converter based on droop control. The method is applied to a fully controlled composite converter, which includes a port for connecting to the AC grid, a main valve, and a support valve. First, grid synchronization information, the dq-axis component of the AC current, the outer loop voltage reference value of the support valve, and the inner loop active current reference value of the support valve are acquired. Then, based at least on the outer loop voltage reference value, the inner loop reactive current reference value is determined. Next, based on the inner loop reactive current reference value, the inner loop active current reference value, the dq-axis component of the AC current, and the grid synchronization information, a first control signal is determined, and the first control signal is used to perform inner loop and outer loop control on the support valve. Simultaneously, based at least on the grid synchronization information, a second control signal is determined, and the second control signal is used to perform active power control and reactive power control on the main valve. The first control signal enables dual closed-loop control of the voltage and current of the support valve, ensuring the stability of the capacitor voltage of the support valve submodule and the effective control of the output current. The second control signal enables active and reactive power control of the main valve. By controlling the opening and closing of each phase arm in the main valve, large-capacity active power transmission and additional reactive power support to the grid can be achieved, thereby improving the stability of the converter operation. Attached Figure Description

[0018] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings:

[0019] Figure 1 A hardware block diagram of a mobile terminal that performs a grid control method for a fully controlled composite converter based on droop control, according to an embodiment of this application, is shown.

[0020] Figure 2 A schematic diagram of a fully controlled composite converter according to an embodiment of this application is shown;

[0021] Figure 3 A schematic flowchart of a grid control method for a fully controlled composite converter based on droop control, according to an embodiment of this application, is shown.

[0022] Figure 4 A schematic flowchart of another grid control method for a fully controlled composite converter based on droop control, according to an embodiment of this application, is shown.

[0023] Figure 5 A schematic diagram illustrating a specific process for generating a power synchronization phase according to an embodiment of this application is shown;

[0024] Figure 6A schematic diagram illustrating a specific process for generating a reference value for the outer loop voltage of a support valve according to an embodiment of this application is shown.

[0025] Figure 7 A schematic diagram illustrating the specific process for generating the dq-axis component of alternating current according to an embodiment of this application is shown.

[0026] Figure 8 A schematic diagram illustrating the specific process for generating a reference value for the inner loop active current of a support valve according to an embodiment of this application is shown.

[0027] Figure 9 A schematic diagram illustrating the specific process for generating inner-loop reactive current reference values ​​according to an embodiment of this application is shown.

[0028] Figure 10 A schematic diagram illustrating the specific process for generating a first control signal according to an embodiment of this application is shown;

[0029] Figure 11 A schematic diagram illustrating the specific process for generating a second control signal according to an embodiment of this application is shown;

[0030] Figure 12 A structural block diagram of a grid control device for a fully controlled composite converter based on droop control, according to an embodiment of this application, is shown.

[0031] The above figures include the following reference numerals:

[0032] 102. Processor; 104. Memory; 106. Transmission equipment; 108. Input / output device; 110. AC power grid; 112. Main valve; 114. Support valve. Detailed Implementation

[0033] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0034] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort should fall within the scope of protection of the present application.

[0035] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate for the embodiments of this application described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0036] As described in the background section, the operating stability of converters in the prior art is not ideal. To solve the above problems, the embodiments of this application provide a grid construction control method for a fully controlled composite converter based on droop control, a grid construction control device for a fully controlled composite converter based on droop control, and a DC transmission system.

[0037] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0038] The methods and embodiments provided in this application can be executed on a mobile terminal, computer terminal, or similar computing device. Taking running on a mobile terminal as an example, Figure 1 This is a hardware structure block diagram of a mobile terminal for a grid control method of a fully controlled composite converter based on droop control, according to an embodiment of the present invention. Figure 1 As shown, a mobile terminal may include one or more ( Figure 1 Only one is shown in the diagram. A processor 102 (which may include, but is not limited to, a microprocessor MCU or a programmable logic device FPGA, etc.) and a memory 104 for storing data are also shown. The mobile terminal may further include a transmission device 106 for communication functions and an input / output device 108. Those skilled in the art will understand that... Figure 1 The structure shown is for illustrative purposes only and does not limit the structure of the mobile terminal described above. For example, the mobile terminal may also include components that are more... Figure 1 The more or fewer components shown, or having the same Figure 1 The different configurations shown.

[0039] The memory 104 can be used to store computer programs, such as application software programs and modules, like the computer program corresponding to the network control method for the fully controlled composite converter based on droop control in this embodiment of the invention. The processor 102 executes various functional applications and data processing by running the computer program stored in the memory 104, thereby implementing the above-described method. The memory 104 may include high-speed random access memory and non-volatile memory, such as one or more magnetic storage devices, flash memory, or other non-volatile solid-state memory. In some instances, the memory 104 may further include memory remotely located relative to the processor 102, and these remote memories can be connected to the mobile terminal via a network. Examples of the aforementioned networks include, but are not limited to, the Internet, corporate intranets, local area networks, mobile communication networks, and combinations thereof. The transmission device 106 is used to receive or send data via a network. Specific examples of the aforementioned networks may include wireless networks provided by the mobile terminal's communication provider. In one example, the transmission device 106 includes a Network Interface Controller (NIC), which can be connected to other network devices via a base station to communicate with the Internet. In one example, the transmission device 106 may be a radio frequency (RF) module, which is used to communicate with the Internet wirelessly.

[0040] This embodiment provides a grid control method for a fully controlled composite converter based on droop control, which runs on a mobile terminal, computer terminal, or similar computing device. It should be noted that the steps shown in the flowchart in the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions. Also, although the logical order is shown in the flowchart, in some cases, the steps shown or described can be executed in a different order than that shown here.

[0041] Figure 2 This is a schematic diagram of a fully controlled composite converter according to an embodiment of this application. The fully controlled composite converter includes a port for connecting to the AC power grid 110, a main valve 112, and a support valve 114. The main valve 112 includes three phases ABC, with an output current I. dc The support valve 114 includes three phases ABC, each phase comprising multiple sub-modules SM. Figure 3 This is a flowchart of a grid control method for a fully controlled composite converter based on droop control, according to an embodiment of this application. Figure 3 As shown, the method includes the following steps:

[0042] Step S201: Obtain grid synchronization information, AC current dq-axis component, outer loop voltage reference value of the support valve, and inner loop active current reference value of the support valve. The grid synchronization information is the power synchronization phase angle of the AC grid. The AC current dq-axis component includes the d-axis component and q-axis component of the AC current in a two-phase rotating coordinate system. The outer loop voltage reference value is the reference value of the bus AC voltage. The inner loop active current reference value is the reference value of the d-axis component of the AC current in a two-phase rotating coordinate system.

[0043] Step S202: Determine the inner loop reactive current reference value based at least on the outer loop voltage reference value, wherein the inner loop reactive current reference value is the reference value of the q-axis component of the AC current in the two-phase rotating coordinate system.

[0044] Step S203: Based on the above inner loop reactive current reference value, the above inner loop active current reference value, the above AC current dq axis component and the above power grid synchronization information, determine the first control signal, and use the above first control signal to control the above support valve to adjust the inner loop reactive current and inner loop active current of the above support valve.

[0045] Step S204: At least based on the above-mentioned power grid synchronization information, determine the second control signal, and use the above-mentioned second control signal to control and adjust the active power and reactive power of the main valve.

[0046] In practical applications, the aforementioned support valve can be a three-phase chain-type full-bridge submodule structure, exhibiting an external characteristic of a voltage source, and participating in the regulation of the converter's reactive power. In some specific embodiments, the aforementioned main valve can be a fully controllable converter valve with a three-phase six-bridge arm structure, meaning that the opening and closing of each phase bridge arm can be controlled, and its external characteristic is that of a current source. The aforementioned first control signal S sa S sb S sc Second control signal S c1-6 The generation process is as follows Figure 4 As shown, it can be divided into a coordinate transformation module, an active power droop control module, a reactive power droop control module, an outer loop AC voltage control module, an outer loop active power control module, an inner loop current control module, and a reactive power control module. The active power droop control module is used to generate the aforementioned power synchronization phase angle θ, and inputs the aforementioned power synchronization phase angle θ and the three-phase AC current i. s_abc The coordinate transformation module, the reactive power control module, and the inner loop current control module are described above. The coordinate transformation module is used to generate the dq-axis component i of the AC current based at least on the power synchronization phase angle θ. sd and i sq , and enter i sd and i sqThe aforementioned inner loop current control module; the aforementioned reactive power droop control module is used to generate the aforementioned outer loop voltage reference value U for the support valve. ac * and input to the aforementioned outer loop AC voltage control module; the aforementioned outer loop AC voltage control module is used to at least determine the aforementioned outer loop voltage reference value U ac * Generate inner loop reactive current reference value i sq_ref , and enter i sq_ref The aforementioned inner-loop current control module; the aforementioned outer-loop active power control module is used to generate the inner-loop active current reference value i for the aforementioned support valve. sd_ref The data is input to the inner loop current control module; the inner loop current control module is used to input the inner loop reactive current reference value i. sq_ref The above-mentioned inner loop active current reference value i sd_ref The above AC current dq-axis components i sd and i sq And the aforementioned power synchronization phase angle θ, outputting the first control signal S sa S sb S sc And using the aforementioned first control signal S sa S sb S sc The aforementioned support valve is controlled; the aforementioned reactive power control module is used to output a second control signal S based at least on the aforementioned power synchronization phase angle θ. c1-6 And using the aforementioned second control signal S c1-6 Control the aforementioned main valves. An active power droop control module is used to implement active power droop control, while a reactive power droop control module is used to implement reactive power droop control. By combining active and reactive power droop control, the traditional phase-locked loop synchronization mechanism is eliminated, enabling the converter to actively establish frequency and bus voltage based on the actual load power.

[0047] This embodiment provides a grid control method for a fully controlled composite converter based on droop control. The method is applied to a converter including a port for connecting to the AC grid, a main valve, and a support valve. First, grid synchronization information, the dq-axis component of the AC current, the outer loop voltage reference value of the support valve, and the inner loop active current reference value of the support valve are acquired. Then, based at least on the outer loop voltage reference value, the inner loop reactive current reference value is determined. Next, based on the inner loop reactive current reference value, the inner loop active current reference value, the dq-axis component of the AC current, and the grid synchronization information, a first control signal is determined, and the first control signal is used to perform inner loop and outer loop control on the support valve. Simultaneously, based at least on the grid synchronization information, a second control signal is determined, and the second control signal is used to perform active power control and reactive power control on the main valve. The first control signal enables dual closed-loop control of the voltage and current of the support valve, ensuring the stability of the capacitor voltage of the support valve submodule and the effective control of the output current. The second control signal enables active and reactive power control of the main valve. By controlling the opening and closing of each phase arm in the main valve, large-capacity active power transmission and additional reactive power support to the grid can be achieved, thereby improving the stability of the converter operation.

[0048] In specific implementation, step S201 can be achieved through the following steps: Step S2011, obtain the first active power, the first active power reference value, and the rated angular frequency of the AC power grid, wherein the first active power is the active power of the AC power grid, and the first active power reference value is the reference value of the first active power; Step S2012, calculate the difference between the first active power reference value and the first active power to obtain the first difference; Step S2013, perform low-pass filtering on the first difference to obtain the first filtered value, and calculate the product of the first filtered value and the active power branch droop coefficient to obtain the first parameter; Step S2014, calculate the sum of the first parameter and the rated angular frequency to obtain the second parameter; Step S2015, input the second parameter into the integrator to obtain the power synchronization phase. This method adopts active power droop control, and by simulating the primary frequency regulation characteristics of the generator, further achieves precise control of the converter based on the active power-frequency characteristics.

[0049] Specifically, such as Figure 5 As shown, according to the formula: The second parameter mentioned above was calculated. For the second parameter mentioned above, The rated angular frequency, This is the droop coefficient of the active branch. Let be the transfer function of the low-pass filter. This is the scaling factor for the low-pass filter; This is the cutoff angular frequency of the low-pass filter. This is the first active power reference value. This is the first active power. Then, according to the formula... The above power synchronization phase was calculated. The second parameter is then input into the integrator 1 / s to obtain the power synchronization phase. Additionally, the initial value of the first active power reference value can be 1, and the formula for calculating the rated angular frequency is as follows: ,in, The above-mentioned rated angular frequency, The frequency of the alternating current can be 50Hz.

[0050] Step S201 of this application can also be implemented through the following steps: Step S2016, obtaining the first reactive power, the first reactive power reference value, and the rated voltage amplitude of the AC power grid, wherein the first reactive power is the reactive power of the AC power grid, and the first reactive power reference value is the reference value of the first reactive power; Step S2017, calculating the difference between the first reactive power reference value and the first reactive power to obtain a second difference; Step S2018, performing low-pass filtering on the second difference to obtain a second filtered value, and calculating the product of the second filtered value and the reactive power branch droop coefficient to obtain a third parameter; Step S2019, calculating the sum of the third parameter and the rated voltage amplitude to obtain the outer loop voltage reference value of the support valve. This method adopts a reactive power droop control approach, simulating the primary frequency regulation characteristics of a generator, and further realizing precise control of the converter based on the characteristics of reactive power-voltage droop.

[0051] Specifically, such as Figure 6 As shown, according to the formula like Figure 6 As shown, the above outer loop voltage reference value was calculated, where, The above refers to the outer loop voltage reference value. The rated voltage amplitude is as described above. This is the reactive branch droop coefficient. This is the first reactive power reference value. The first reactive power, Let be the transfer function of the low-pass filter. This is the scaling factor for the low-pass filter; This is the cutoff angular frequency of the low-pass filter. In practical applications, the initial value of the first reactive power reference value can be 0, and the initial value of the rated voltage amplitude can be 1. The control terminal maps the first reactive power reference value to a negative trigger angle modulation wave, causing the main valve to actively generate inductive reactive power; the support valve synchronously reduces the capacitive output, and the reactive power reverse overlap area of ​​the two is ≥0.3pu.

[0052] In other embodiments, steps S2013 and S2018 described above can be implemented through the following steps: obtaining a three-dimensional lookup table, which characterizes the mapping relationship between the junction temperature of the power semiconductor device supporting the valve, the reactive power branch droop coefficient, and the active power branch droop coefficient; and determining the reactive power branch droop coefficient and the active power branch droop coefficient based on the three-dimensional lookup table. This method can further and more quickly determine the reactive power branch droop coefficient and the active power branch droop coefficient.

[0053] For example: at junction temperature T j Automatically reduce the droop coefficient of active power branches at temperatures above 90℃. Increase the droop coefficient of reactive power branches. It prioritizes sacrificing active power and retaining reactive power; at the same time, it adopts an event-triggered mechanism to update the three-dimensional lookup table every 1ms to avoid frequent jitter.

[0054] To further accelerate the processing of the AC current dq-axis component, step S201 of this application can also be implemented through the following steps: step S20110, obtaining the three-phase AC current of the support valve; step S20111, performing coordinate transformation processing on the three-phase AC current to obtain the AC current dq-axis component, wherein the AC current dq-axis component is the dq-axis component of the three-phase AC current in a two-phase rotating coordinate system.

[0055] Specifically, such as Figure 7 As shown, the three-phase AC current i supporting the valve is... s_abc By performing a coordinate transformation, the actual value of the dq-axis current component i in the two-phase rotating coordinate system can be obtained. sd and i sq The power synchronization phase angle θ required for coordinate transformation is generated by the active power droop control module, which can complete the synchronization.

[0056] Step S201 above can also be implemented through the following steps: Step S20112, obtain the second active power and the second active power reference value, wherein the second active power is the active power of the support valve, and the second active power reference value is the reference value of the second active power; Step S20113, calculate the difference between the second active power reference value and the second active power to obtain the fourth difference value; Step S20114, input the fourth difference value to the proportional-integral controller to obtain the inner loop active current reference value of the support valve. The above method can further improve the accuracy of the calculation of the inner loop active current reference value.

[0057] Specifically, such as Figure 8 As shown, the second active power P collected will be... svg Compared with the second active power reference value P svg*By comparing these values, the inner loop active current reference value i can be obtained through a PI controller. sd_ref The initial value of the second active power reference value can be 0.

[0058] Step S202 above can also be implemented in other ways, for example: step S2021, obtain the AC voltage of the bus and calculate the difference between the outer loop voltage reference value of the support valve and the AC voltage of the bus to obtain a third difference; step S2022, input the third difference to the proportional-integral controller to obtain the inner loop reactive current reference value. The above method can further improve the calculation accuracy of the inner loop reactive current reference value.

[0059] Specifically, such as Figure 9 As shown, the AC voltage of the converter is essentially controlled by the reactive power control loop, where the outer loop voltage reference value U of the support valve is... ac *The output from the reactive power droop control circuit will be the collected bus AC voltage U. ac with U ac *Reference value U for the outer loop voltage of the support valve ac *By comparison, the inner loop reactive current reference value i can be obtained through the PI controller. sq_ref .

[0060] In some embodiments, step S203 can be implemented through the following steps: Step S2031, calculate the difference between the inner loop reactive current reference value and the q-axis component of the AC current in the two-phase rotating coordinate system to obtain a fifth difference; Step S2032, input the fifth difference to the proportional-integral controller to obtain a first voltage modulation signal; Step S2033, calculate the difference between the inner loop active current reference value and the d-axis component of the AC current in the two-phase rotating coordinate system to obtain a sixth difference; Step S2034, input the sixth difference to the proportional-integral controller to obtain a second voltage modulation signal; Step S2035, perform coordinate inverse transformation on the first and second voltage modulation signals to obtain a voltage sinusoidal modulation signal; Step S2036, perform nearest-level approximation modulation on the voltage sinusoidal modulation signal to obtain the first control signal. This method can further generate the first control signal quickly.

[0061] like Figure 10 As shown, the d-axis component i of the alternating current is... sd Compared with the inner loop active current reference value i sd_ref Comparison, i of the q-axis component of the alternating current sq Compared with the inner loop reactive current reference value i sq_ref By comparing the signals and performing PI control, the dq-axis modulation signal of the support valve output voltage, i.e., the first voltage modulation signal u, can be obtained. sqWith the second voltage modulation signal u sd The sinusoidal modulation signal u of the output voltage can be obtained by inverse coordinate transformation. sa、 u sb and u sc Voltage sinusoidal modulation signal u sj The switching signals S supporting each device in the valve submodule can be obtained by near-nearest level approximation modulation. sa S sb S sc Taking a single-phase bridge arm of a support valve where each bridge arm is cascaded with submodules, and each submodule contains four fully controlled IGBT devices as an example, each device needs to send a switching signal. Since the triggering and turn-off times of each device in the support valve bridge arm are different, the nearest-level approximation algorithm is needed to calculate the switching timing of each device and send it to each device individually. Because the three-phase modulation waves are 120° apart, and Nearest-Level Modulation (NLM) relies on the output modulation wave signal to generate the corresponding phase's switching signal, it is simplified as S... sa S sb S sc Among them, the A-phase switch signal S sa For example, S sa It contains the switching signals of the power devices in all sub-modules of phase A, which is equivalent to a four-dimensional array, referring to the four devices in the full-bridge module. The length of the array represents the number of bridge arm sub-modules, thus completing the power control of the support valve.

[0062] Step S204 above can be implemented through the following steps: Step S2041, obtain the capacitor voltage and second reactive power of the submodule of the support valve, wherein the second reactive power is the reactive power of the support valve; Step S2042, perform negative feedback adjustment on the capacitor voltage of the submodule of the support valve to obtain a first current modulation signal; Step S2043, perform negative feedback adjustment on the second reactive power to obtain a second current modulation signal; Step S2044, perform coordinate inverse transformation on the first current modulation signal and the second current modulation signal to obtain a current sinusoidal modulation signal; Step S2045, perform pulse width modulation on the current sinusoidal modulation signal to obtain the second control signal. By operating the main valve in PWM mode, the reactive power of the main valve can be further controlled.

[0063] In other embodiments, step S204 can also be implemented by: determining whether the firing angle of the main valve is within a predetermined range; and controlling the power semiconductor device of the main valve to remain off when the firing angle of the main valve is within the predetermined range. In practical applications, the predetermined range can be α∈[-15°,0°].

[0064] In other embodiments, step S2042 can be implemented through the following steps: Step S20421, obtaining the reference value of the capacitor voltage of the sub-module of the support valve, and calculating the difference between the reference value of the capacitor voltage of the sub-module of the support valve and the capacitor voltage of the sub-module of the support valve to obtain a seventh difference; Step S20422, inputting the seventh difference to the proportional-integral controller to obtain the first current modulation signal. The above method can further improve the accuracy of determining the first current modulation signal.

[0065] In some embodiments, step S2043 can be implemented through the following steps: Step S20431, obtaining a second reactive power reference value, wherein the second reactive power reference value is a reference value of the second reactive power, and calculating the difference between the second reactive power reference value and the second reactive power to obtain an eighth difference value; Step S20432, inputting the eighth difference value to a proportional-integral controller to obtain the second current modulation signal. The above method can further improve the accuracy of determining the second current modulation signal.

[0066] Specifically, such as Figure 11 As shown, due to the active component of the main valve, i is the first current modulation signal i cd With the capacitor voltage U of the supporting valve submodule dcn There is a proportional relationship, therefore it can be controlled by the capacitor voltage U of the supporting valve submodule. dcn The negative feedback loop controls the d-axis component of the modulated current output wave of the main valve. This involves calculating the reference value U of the capacitor voltage of the submodule supporting the valve. dcn_ref The capacitor voltage U of the submodule supporting the valve mentioned above dcn The difference is used to obtain the seventh difference; then the seventh difference is input to the proportional-integral controller PI to obtain the first current modulation signal i. cd Because the reactive component of the main valve output current, i.e., the second current modulation signal i cq With the reactive power Q of the support valve csc There is a proportional relationship, therefore it can be determined through Q. csc The negative feedback loop controls the q-axis component of the output current modulation wave of the main valve. This involves calculating the aforementioned second reactive power reference value Q. csc_ref With the aforementioned second reactive power Q csc The difference is used to obtain the eighth difference; the eighth difference is then input to the proportional-integral controller PI to obtain the second current modulation signal i. cq The first current modulation signal i cd Second current modulation signal i cq The sinusoidal modulation signal i of the output current can be obtained by inverse coordinate transformation. cj(j=a, b, c). The switching signals S for each phase arm of the main valve can be obtained by pulse width modulation (PWM) of the sinusoidal current modulation signal. c1-6 Taking the example of each bridge arm of the main valve using a direct-connection device configuration, all devices in the bridge arm are triggered or turned off simultaneously. The main valve contains a total of three phases and six bridge arms, which means that six trigger signals are required. Among them, the power synchronization phase angle θ required for coordinate transformation is generated by the active power droop control module, which can complete the synchronization.

[0067] This application also provides a grid control device for a fully controlled hybrid converter based on droop control. It should be noted that this grid control device can be used to execute the grid control method for a fully controlled hybrid converter based on droop control provided in this application. This device is used to implement the above embodiments and preferred embodiments; details already described will not be repeated. As used below, the term "module" can refer to a combination of software and / or hardware that performs a predetermined function. Although the device described in the following embodiments is preferably implemented in software, hardware implementation, or a combination of software and hardware, is also possible and contemplated.

[0068] The following describes the grid control device for a fully controlled composite converter based on droop control provided in the embodiments of this application.

[0069] Figure 12 This is a schematic diagram of a grid control device for a fully controlled composite converter based on droop control, according to an embodiment of this application. Figure 12 As shown, the device includes:

[0070] The acquisition unit 10 is used to acquire grid synchronization information, AC current dq-axis components, outer loop voltage reference value of the support valve, and inner loop active current reference value of the support valve. The grid synchronization information is the power synchronization phase angle of the AC grid. The AC current dq-axis components include the d-axis component and the q-axis component of the AC current in a two-phase rotating coordinate system. The outer loop voltage reference value is the reference value of the bus AC voltage. The inner loop active current reference value is the reference value of the d-axis component of the AC current in a two-phase rotating coordinate system.

[0071] The determining unit 20 is used to determine the inner loop reactive current reference value based at least on the outer loop voltage reference value, wherein the inner loop reactive current reference value is the reference value of the q-axis component of the AC current in the two-phase rotating coordinate system.

[0072] The first control unit 30 is used to determine a first control signal based on the above-mentioned inner loop reactive current reference value, the above-mentioned inner loop active current reference value, the above-mentioned AC current dq axis component and the above-mentioned power grid synchronization information, and use the above-mentioned first control signal to control the above-mentioned support valve to adjust the inner loop reactive current and inner loop active current of the above-mentioned support valve.

[0073] The second control unit 40 is used to determine a second control signal based at least on the above-mentioned power grid synchronization information, and to use the second control signal to control and adjust the active power and reactive power of the main valve.

[0074] In practical applications, the aforementioned support valve can be a three-phase chain-type full-bridge submodule structure, exhibiting an external characteristic of a voltage source, and participating in the regulation of the converter's reactive power. In some specific embodiments, the aforementioned main valve can be a fully controllable converter valve with a three-phase six-bridge arm structure, meaning that the opening and closing of each phase bridge arm can be controlled, and its external characteristic is that of a current source. The aforementioned first control signal S sa S sb S sc Second control signal S c1-6 The generation process is as follows Figure 4 As shown, it can be divided into a coordinate transformation module, an active power droop control module, a reactive power droop control module, an outer loop AC voltage control module, an outer loop active power control module, an inner loop current control module, and a reactive power control module. The active power droop control module is used to generate the aforementioned power synchronization phase angle θ and input the aforementioned power synchronization phase angle θ to the aforementioned coordinate transformation module, the aforementioned reactive power control module, and the aforementioned inner loop current control module. The coordinate transformation module is used to generate the AC current dq axis component i based at least on the aforementioned power synchronization phase angle θ. sd and i sq , and enter i sd and i sq The aforementioned inner loop current control module; the aforementioned reactive power droop control module is used to generate the aforementioned outer loop voltage reference value U for the support valve. ac * and input to the aforementioned outer loop AC voltage control module; the aforementioned outer loop AC voltage control module is used to at least determine the aforementioned outer loop voltage reference value U ac * Generate inner loop reactive current reference value i sq_ref , and enter i sq_ref The aforementioned inner-loop current control module; the aforementioned outer-loop active power control module is used to generate the inner-loop active current reference value i for the aforementioned support valve. sd_ref The data is input to the inner loop current control module; the inner loop current control module is used to input the inner loop reactive current reference value i. sq_ref The above-mentioned inner loop active current reference value i sd_ref The above AC current dq-axis components i sd and i sqAnd the aforementioned power synchronization phase angle θ, outputting the first control signal S sa S sb S sc And using the aforementioned first control signal S sa S sb S sc The aforementioned support valve is controlled; the aforementioned reactive power control module is used to output a second control signal S based at least on the aforementioned power synchronization phase angle θ. c1-6 And using the aforementioned second control signal S c1-6 Control the aforementioned main valves. An active power droop control module is used to implement active power droop control, while a reactive power droop control module is used to implement reactive power droop control. By combining active and reactive power droop control, the traditional phase-locked loop synchronization mechanism is eliminated, enabling the converter to actively establish frequency and bus voltage based on the actual load power.

[0075] This embodiment provides a grid control device for a fully controlled composite converter based on droop control. The method is applied to a converter, which includes a port for connecting to the AC grid, a main valve, and a support valve. An acquisition unit acquires grid synchronization information, the dq-axis component of the AC current, the outer loop voltage reference value of the support valve, and the inner loop active current reference value of the support valve. A determination unit determines the inner loop reactive current reference value based at least on the outer loop voltage reference value. A first control unit determines a first control signal based on the inner loop reactive current reference value, the inner loop active current reference value, the dq-axis component of the AC current, and the grid synchronization information, and uses the first control signal to perform inner loop and outer loop control on the support valve. A second control unit determines a second control signal based at least on the grid synchronization information, and uses the second control signal to perform active power control and reactive power control on the main valve. The first control signal enables dual closed-loop control of the voltage and current of the support valve, ensuring the stability of the capacitor voltage of the support valve submodule and the effective control of the output current. The second control signal enables active and reactive power control of the main valve. By controlling the opening and closing of each phase arm in the main valve, large-capacity active power transmission and additional reactive power support to the grid can be achieved, thereby improving the stability of the converter operation.

[0076] In specific implementation, the aforementioned acquisition unit includes a first acquisition module, a first calculation module, a first processing module, a second calculation module, and a first input module. The first acquisition module acquires a first active power, a first active power reference value, and the rated angular frequency of the AC power grid. The first active power is the active power of the AC power grid, and the first active power reference value is the reference value of the first active power. The first calculation module calculates the difference between the first active power reference value and the first active power to obtain a first difference. The first processing module performs low-pass filtering on the first difference to obtain a first filtered value and calculates the product of the first filtered value and the active power branch droop coefficient to obtain a first parameter. The second calculation module calculates the sum of the first parameter and the rated angular frequency to obtain a second parameter. The first input module inputs the second parameter into an integrator to obtain the power synchronization phase. This device employs active power droop control, simulating the primary frequency regulation characteristics of a generator, and further achieves precise control of the converter based on the active power-frequency characteristics.

[0077] Specifically, such as Figure 5 As shown, according to the formula: The second parameter mentioned above was calculated. For the second parameter mentioned above, The rated angular frequency, This is the droop coefficient of the active branch. Let be the transfer function of the low-pass filter. This is the scaling factor for the low-pass filter; This is the cutoff angular frequency of the low-pass filter. This is the first active power reference value. This is the first active power. Then, according to the formula... The above power synchronization phase was calculated. The second parameter is then input into the integrator 1 / s to obtain the power synchronization phase. Additionally, the initial value of the first active power reference value can be 1, and the formula for calculating the rated angular frequency is as follows: ,in, The above-mentioned rated angular frequency, The frequency of the alternating current can be 50Hz.

[0078] The aforementioned acquisition unit of this application further includes: a second acquisition module, a third calculation module, a second processing module, and a fourth calculation module. The second acquisition module acquires a first reactive power, a first reactive power reference value, and the rated voltage amplitude of the AC power grid. The first reactive power is the reactive power of the AC power grid, and the first reactive power reference value is the reference value of the first reactive power. The third calculation module calculates the difference between the first reactive power reference value and the first reactive power to obtain a second difference. The second processing module performs low-pass filtering on the second difference to obtain a second filtered value and calculates the product of the second filtered value and the reactive power branch droop coefficient to obtain a third parameter. The fourth calculation module calculates the sum of the third parameter and the rated voltage amplitude to obtain the outer loop voltage reference value of the support valve. This device employs reactive power droop control, simulating the primary frequency regulation characteristics of a generator, and further achieves precise control of the converter based on the characteristics of reactive power-voltage droop.

[0079] Specifically, such as Figure 6 As shown, according to the formula like Figure 6 As shown, the above outer loop voltage reference value was calculated, where, The above refers to the outer loop voltage reference value. The rated voltage amplitude is as described above. This is the reactive branch droop coefficient. This is the first reactive power reference value. The first reactive power, Let be the transfer function of the low-pass filter. This is the scaling factor for the low-pass filter; This is the cutoff angular frequency of the low-pass filter. In practical applications, the initial value of the first reactive power reference value can be 0, and the initial value of the rated voltage amplitude can be 1. The control terminal maps the first reactive power reference value to a negative trigger angle modulation wave, causing the main valve to actively generate inductive reactive power; the support valve synchronously reduces the capacitive output, and the reactive power reverse overlap area of ​​the two is ≥0.3pu.

[0080] In other embodiments, the first processing module and the second processing module further include a first acquisition submodule and a determination submodule. The first acquisition submodule acquires a three-dimensional lookup table, which characterizes the mapping relationship between the junction temperature of the power semiconductor device supporting the valve, the reactive power branch droop coefficient, and the active power branch droop coefficient. The determination submodule determines the reactive power branch droop coefficient and the active power branch droop coefficient based on the three-dimensional lookup table. The device can further quickly determine the reactive power branch droop coefficient and the active power branch droop coefficient.

[0081] For example: at junction temperature T jAutomatically reduce the droop coefficient of active power branches at temperatures above 90℃. Increase the droop coefficient of reactive power branches. It prioritizes sacrificing active power and retaining reactive power; at the same time, it adopts an event-triggered mechanism to update the three-dimensional lookup table every 1ms to avoid frequent jitter.

[0082] To further accelerate the acquisition of the dq-axis component of the AC current, the acquisition unit of this application further includes a third acquisition module and a third processing module. The third acquisition module is used to acquire the three-phase AC current of the support valve. The third processing module is used to perform coordinate transformation processing on the three-phase AC current to obtain the dq-axis component of the AC current, which is the dq-axis component of the three-phase AC current in a two-phase rotating coordinate system.

[0083] Specifically, such as Figure 7 As shown, the three-phase AC current i supporting the valve is... s_abc By performing a coordinate transformation, the actual value of the dq-axis current component i in the two-phase rotating coordinate system can be obtained. sd and i sq The power synchronization phase angle θ required for coordinate transformation is generated by the active power droop control module, which can complete the synchronization.

[0084] The aforementioned acquisition unit further includes: a fourth acquisition module, a fifth calculation module, and a second input module. The fourth acquisition module acquires a second active power and a second active power reference value, where the second active power is the active power of the supporting valve, and the second active power reference value is the reference value of the second active power. The fifth calculation module calculates the difference between the second active power reference value and the second active power to obtain a fourth difference value. The second input module inputs the fourth difference value to a proportional-integral controller to obtain the inner-loop active current reference value of the supporting valve. This device can further improve the accuracy of the inner-loop active current reference value calculation.

[0085] Specifically, such as Figure 8 As shown, the second active power P collected will be... svg Compared with the second active power reference value P svg *By comparing these values, the inner loop active current reference value i can be obtained through a PI controller. sd_ref The initial value of the second active power reference value can be 0.

[0086] The aforementioned determining unit includes a fifth acquisition module and a third input module. The fifth acquisition module acquires the AC voltage of the aforementioned bus and calculates the difference between the outer-loop voltage reference value of the aforementioned support valve and the AC voltage of the aforementioned bus, obtaining a third difference value. The third input module inputs the third difference value to the proportional-integral controller to obtain the inner-loop reactive current reference value. This device can further improve the accuracy of the calculation of the inner-loop reactive current reference value.

[0087] Specifically, such as Figure 9 As shown, the AC voltage of the converter is essentially controlled by the reactive power control loop, where the outer loop voltage reference value U of the support valve is... ac *The output from the reactive power droop control circuit will be the collected bus AC voltage U. ac with U ac *Reference value U for the outer loop voltage of the support valve ac *By comparison, the inner loop reactive current reference value i can be obtained through the PI controller. sq_ref .

[0088] In some embodiments, the first control unit includes a sixth calculation module, a fourth input module, a seventh calculation module, a fifth input module, a fourth processing module, and a fifth processing module. The sixth calculation module calculates the difference between the inner-loop reactive current reference value and the q-axis component of the AC current in a two-phase rotating coordinate system to obtain a fifth difference value. The fourth input module inputs the fifth difference value to a proportional-integral controller to obtain a first voltage modulation signal. The seventh calculation module calculates the difference between the inner-loop active current reference value and the d-axis component of the AC current in a two-phase rotating coordinate system to obtain a sixth difference value. The fifth input module inputs the sixth difference value to a proportional-integral controller to obtain a second voltage modulation signal. The fourth processing module performs coordinate inverse transformation on the first and second voltage modulation signals to obtain a voltage sinusoidal modulation signal. The fifth processing module performs near-level approximation modulation on the voltage sinusoidal modulation signal to obtain the first control signal. This device can further generate the first control signal quickly.

[0089] like Figure 10 As shown, the d-axis component i of the alternating current is... sd Compared with the inner loop active current reference value i sd_ref Comparison, i of the q-axis component of the alternating current sq Compared with the inner loop reactive current reference value i sq_ref By comparing the signals and performing PI control, the dq-axis modulation signal of the support valve output voltage, i.e., the first voltage modulation signal u, can be obtained. sq With the second voltage modulation signal u sd The sinusoidal modulation signal u of the output voltage can be obtained by inverse coordinate transformation.sj (j=a, b, c). Voltage sinusoidal modulation signal u sj The switching signals S supporting each device in the valve submodule can be obtained by near-nearest level approximation modulation. sa S sb S sc Taking a single-phase bridge arm of a support valve where each bridge arm is cascaded with submodules, and each submodule contains four fully controlled IGBT devices as an example, each device needs to send a switching signal. Since the triggering and turn-off times of each device in the support valve bridge arm are different, the nearest-level approximation algorithm is needed to calculate the switching timing of each device and send it to each device individually. Because the three-phase modulation waves are 120° apart, and Nearest-Level Modulation (NLM) relies on the output modulation wave signal to generate the corresponding phase's switching signal, it is simplified as S... sa S sb S sc Among them, the A-phase switch signal S sa For example, S sa It contains the switching signals of the power devices in all sub-modules of phase A, which is equivalent to a four-dimensional array, referring to the four devices in the full-bridge module. The length of the array represents the number of bridge arm sub-modules, thus completing the power control of the support valve.

[0090] The aforementioned second control unit includes a sixth acquisition module, a sixth processing module, a seventh processing module, an eighth processing module, and a ninth processing module. The sixth acquisition module acquires the capacitor voltage and second reactive power of the sub-module of the support valve, where the second reactive power is the reactive power of the support valve. The sixth processing module performs negative feedback regulation on the capacitor voltage of the sub-module of the support valve to obtain a first current modulation signal. The seventh processing module performs negative feedback regulation on the second reactive power to obtain a second current modulation signal. The eighth processing module performs coordinate inverse transformation on the first and second current modulation signals to obtain a sinusoidal current modulation signal. The ninth processing module performs pulse width modulation on the sinusoidal current modulation signal to obtain the second control signal. By operating the main valve in PWM mode, further control of the reactive power of the main valve can be achieved.

[0091] In other embodiments, the second control unit is further configured to determine whether the firing angle of the main valve is within a predetermined range; if the firing angle of the main valve is within the predetermined range, the power semiconductor device of the main valve is controlled to remain off. In practical applications, the predetermined range can be α∈[-15°,0°].

[0092] The sixth processing module includes a second acquisition submodule and a first input submodule. The second acquisition submodule acquires a reference value for the capacitor voltage of the submodule supporting the valve and calculates the difference between the reference value and the capacitor voltage of the submodule, obtaining a seventh difference. The first input submodule inputs this seventh difference to a proportional-integral controller to obtain the first current modulation signal. This device can further improve the accuracy of determining the first current modulation signal.

[0093] The seventh processing module includes a third acquisition submodule and a second input submodule. The third acquisition submodule acquires a second reactive power reference value, which is a reference value for the second reactive power, and calculates the difference between the second reactive power reference value and the second reactive power to obtain an eighth difference value. The second input submodule inputs the eighth difference value to a proportional-integral controller to obtain the second current modulation signal. This device can further improve the accuracy of determining the second current modulation signal.

[0094] Specifically, such as Figure 11 As shown, due to the active component of the main valve, i is the first current modulation signal i cd With the capacitor voltage U of the supporting valve submodule dcn There is a proportional relationship, therefore it can be controlled by the capacitor voltage U of the supporting valve submodule. dcn The negative feedback loop controls the d-axis component of the modulated current output wave of the main valve. This involves calculating the reference value U of the capacitor voltage of the submodule supporting the valve. dcn_ref The capacitor voltage U of the submodule supporting the valve mentioned above dcn The difference is used to obtain the seventh difference; then the seventh difference is input to the proportional-integral controller PI to obtain the first current modulation signal i. cd Because the reactive component of the main valve output current, i.e., the second current modulation signal i cq With the reactive power Q of the support valve csc There is a proportional relationship, therefore it can be determined through Q. csc The negative feedback loop controls the q-axis component of the output current modulation wave of the main valve. This involves calculating the aforementioned second reactive power reference value Q. csc_ref With the aforementioned second reactive power Q csc The difference is used to obtain the eighth difference; the eighth difference is then input to the proportional-integral controller PI to obtain the second current modulation signal i. cq The first current modulation signal i cd Second current modulation signal i cq The sinusoidal modulation signal i of the output current can be obtained by inverse coordinate transformation. cj(j=a, b, c). The switching signals S for each phase arm of the main valve can be obtained by carrier modulation of the sinusoidal current modulation signal. c1-6 Taking the example of each bridge arm of the main valve using a direct-connection device configuration, all devices in the bridge arm are triggered or turned off simultaneously. The main valve contains a total of three phases and six bridge arms, which means that six trigger signals are required. Among them, the power synchronization phase angle θ required for coordinate transformation is generated by the active power droop control module, which can complete the synchronization.

[0095] This application also provides a DC transmission system, including a DC transmission sending end and a DC transmission receiving end, wherein the DC transmission sending end adopts any of the above-mentioned grid control methods based on droop control of the fully controlled composite converter.

[0096] This enables the aforementioned converter to possess external voltage source characteristics, allowing for reliable grid connection and power transmission even in scenarios with extremely low short-circuit ratios or islanding.

[0097] The aforementioned grid control device for a fully controlled hybrid converter based on droop control includes a processor and a memory. The acquisition unit, determination unit, first control unit, and second control unit are all stored as program units in the memory, and the processor executes these program units to achieve the corresponding functions. All of the above modules reside in the same processor; alternatively, the modules may be located in different processors in any combination.

[0098] The processor contains a kernel, which retrieves the corresponding program unit from memory. One or more kernels can be configured, and the inverter is controlled by adjusting kernel parameters.

[0099] The memory may include non-permanent memory in computer-readable media, such as random access memory (RAM) and / or non-volatile memory, such as read-only memory (ROM) or flash RAM, and the memory includes at least one memory chip.

[0100] This invention provides a computer-readable storage medium including a stored program, wherein, when the program is executed, it controls the device containing the computer-readable storage medium to perform the grid control method for a fully controlled composite converter based on droop control.

[0101] Specifically, the grid control method for fully controlled hybrid converters based on droop control includes:

[0102] Step S201: Obtain grid synchronization information, AC current dq-axis component, outer loop voltage reference value of the support valve, and inner loop active current reference value of the support valve. The grid synchronization information is the power synchronization phase angle of the AC grid. The AC current dq-axis component includes the d-axis component and q-axis component of the AC current in a two-phase rotating coordinate system. The outer loop voltage reference value is the reference value of the bus AC voltage. The inner loop active current reference value is the reference value of the d-axis component of the AC current in a two-phase rotating coordinate system.

[0103] Step S202: Determine the inner loop reactive current reference value based at least on the outer loop voltage reference value, wherein the inner loop reactive current reference value is the reference value of the q-axis component of the AC current in the two-phase rotating coordinate system.

[0104] Step S203: Based on the above inner loop reactive current reference value, the above inner loop active current reference value, the above AC current dq axis component and the above power grid synchronization information, determine the first control signal, and use the above first control signal to control the above support valve to adjust the inner loop reactive current and inner loop active current of the above support valve.

[0105] Step S204: At least based on the above-mentioned power grid synchronization information, determine the second control signal, and use the above-mentioned second control signal to control and adjust the active power and reactive power of the main valve.

[0106] This invention provides a processor for running a program, wherein the program executes the above-described grid control method for a fully controlled composite converter based on droop control.

[0107] Specifically, the grid control method for fully controlled hybrid converters based on droop control includes:

[0108] Step S201: Obtain grid synchronization information, AC current dq-axis component, outer loop voltage reference value of the support valve, and inner loop active current reference value of the support valve. The grid synchronization information is the power synchronization phase angle of the AC grid. The AC current dq-axis component includes the d-axis component and q-axis component of the AC current in a two-phase rotating coordinate system. The outer loop voltage reference value is the reference value of the bus AC voltage. The inner loop active current reference value is the reference value of the d-axis component of the AC current in a two-phase rotating coordinate system.

[0109] Step S202: Determine the inner loop reactive current reference value based at least on the outer loop voltage reference value, wherein the inner loop reactive current reference value is the reference value of the q-axis component of the AC current in the two-phase rotating coordinate system.

[0110] Step S203: Based on the above inner loop reactive current reference value, the above inner loop active current reference value, the above AC current dq axis component and the above power grid synchronization information, determine the first control signal, and use the above first control signal to control the above support valve to adjust the inner loop reactive current and inner loop active current of the above support valve.

[0111] Step S204: At least based on the above-mentioned power grid synchronization information, determine the second control signal, and use the above-mentioned second control signal to control and adjust the active power and reactive power of the main valve.

[0112] This invention provides a device including a processor, a memory, and a program stored in the memory and executable on the processor. When the processor executes the program, it performs at least the following steps:

[0113] Step S201: Obtain grid synchronization information, AC current dq-axis component, outer loop voltage reference value of the support valve, and inner loop active current reference value of the support valve. The grid synchronization information is the power synchronization phase angle of the AC grid. The AC current dq-axis component includes the d-axis component and q-axis component of the AC current in a two-phase rotating coordinate system. The outer loop voltage reference value is the reference value of the bus AC voltage. The inner loop active current reference value is the reference value of the d-axis component of the AC current in a two-phase rotating coordinate system.

[0114] Step S202: Determine the inner loop reactive current reference value based at least on the outer loop voltage reference value, wherein the inner loop reactive current reference value is the reference value of the q-axis component of the AC current in the two-phase rotating coordinate system.

[0115] Step S203: Based on the above inner loop reactive current reference value, the above inner loop active current reference value, the above AC current dq axis component and the above power grid synchronization information, determine the first control signal, and use the above first control signal to control the above support valve to adjust the inner loop reactive current and inner loop active current of the above support valve.

[0116] Step S204: At least based on the above-mentioned power grid synchronization information, determine the second control signal, and use the above-mentioned second control signal to control and adjust the active power and reactive power of the main valve.

[0117] The devices mentioned in this article can be servers, PCs, tablets, mobile phones, etc.

[0118] This application also provides a computer program product, which, when executed on a data processing device, is suitable for executing an initialization program having at least the following method steps:

[0119] Step S201: Obtain grid synchronization information, AC current dq-axis component, outer loop voltage reference value of the support valve, and inner loop active current reference value of the support valve. The grid synchronization information is the power synchronization phase angle of the AC grid. The AC current dq-axis component includes the d-axis component and q-axis component of the AC current in a two-phase rotating coordinate system. The outer loop voltage reference value is the reference value of the bus AC voltage. The inner loop active current reference value is the reference value of the d-axis component of the AC current in a two-phase rotating coordinate system.

[0120] Step S202: Determine the inner loop reactive current reference value based at least on the outer loop voltage reference value, wherein the inner loop reactive current reference value is the reference value of the q-axis component of the AC current in the two-phase rotating coordinate system.

[0121] Step S203: Based on the above inner loop reactive current reference value, the above inner loop active current reference value, the above AC current dq axis component and the above power grid synchronization information, determine the first control signal, and use the above first control signal to control the above support valve to adjust the inner loop reactive current and inner loop active current of the above support valve.

[0122] Step S204: At least based on the above-mentioned power grid synchronization information, determine the second control signal, and use the above-mentioned second control signal to control and adjust the active power and reactive power of the main valve.

[0123] It is obvious to those skilled in the art that the modules or steps of the present invention described above can be implemented using general-purpose computing devices. They can be centralized on a single computing device or distributed across a network of multiple computing devices. They can be implemented using computer-executable program code, and thus can be stored in a storage device for execution by a computing device. In some cases, the steps shown or described can be performed in a different order than those described herein, or they can be fabricated as separate integrated circuit modules, or multiple modules or steps can be fabricated as a single integrated circuit module. Thus, the present invention is not limited to any particular combination of hardware and software.

[0124] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product embodied 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.

[0125] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations 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, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0126] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0127] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0128] In a typical configuration, a computing device includes one or more processors (CPU), input / output ports, network ports, and memory.

[0129] Memory may include non-persistent memory in computer-readable media, such as random access memory (RAM) and / or non-volatile memory, such as read-only memory (ROM) or flash RAM. Memory is an example of computer-readable media.

[0130] Computer-readable media include both permanent and non-permanent, removable and non-removable media that can store information by any method or technology. Information can be computer-readable instructions, data structures, modules of programs, or other data. Examples of computer storage media include, but are not limited to, phase-change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technologies, CD-ROM, digital versatile optical disc (DVD) or other optical storage, magnetic tape, disk storage or other magnetic storage devices, or any other non-transferable medium that can be used to store information accessible by a computing device. As defined herein, computer-readable media does not include transient computer-readable media, such as modulated data signals and carrier waves.

[0131] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0132] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element.

[0133] As can be seen from the above description, the embodiments of this application achieve the following technical effects:

[0134] 1) The grid control method for a fully controlled composite converter based on droop control in this application is applied to a fully controlled composite converter, which includes a port for connecting to the AC grid, a main valve, and a support valve. First, grid synchronization information, the dq-axis component of the AC current, the outer loop voltage reference value of the support valve, and the inner loop active current reference value of the support valve are acquired. Then, at least based on the outer loop voltage reference value, the inner loop reactive current reference value is determined. Next, based on the inner loop reactive current reference value, the inner loop active current reference value, the dq-axis component of the AC current, and the grid synchronization information, a first control signal is determined, and the first control signal is used to perform inner loop control and outer loop control on the support valve. Simultaneously, at least based on the grid synchronization information, a second control signal is determined, and the second control signal is used to perform active power control and reactive power control on the main valve. The first control signal enables dual closed-loop control of the voltage and current of the support valve, ensuring the stability of the capacitor voltage of the support valve submodule and the effective control of the output current. The second control signal enables active and reactive power control of the main valve. By controlling the opening and closing of each phase arm in the main valve, large-capacity active power transmission and additional reactive power support to the grid can be achieved, thereby improving the stability of the converter operation.

[0135] 2) The grid control device for a fully controlled composite converter based on droop control of this application is applied to a fully controlled composite converter, which includes a port for connecting to the AC grid, a main valve, and a support valve. The acquisition unit acquires grid synchronization information, the dq-axis component of the AC current, the outer loop voltage reference value of the support valve, and the inner loop active current reference value of the support valve. The determination unit determines the inner loop reactive current reference value based at least on the outer loop voltage reference value. The first control unit determines a first control signal based on the inner loop reactive current reference value, the inner loop active current reference value, the dq-axis component of the AC current, and the grid synchronization information, and uses the first control signal to perform inner loop control and outer loop control on the support valve. The second control unit determines a second control signal based at least on the grid synchronization information, and uses the second control signal to perform active power control and reactive power control on the main valve. The first control signal enables dual closed-loop control of the voltage and current of the support valve, ensuring the stability of the capacitor voltage of the support valve submodule and the effective control of the output current. The second control signal enables active and reactive power control of the main valve. By controlling the opening and closing of each phase arm in the main valve, large-capacity active power transmission and additional reactive power support to the grid can be achieved, thereby improving the stability of the converter operation.

[0136] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A grid control method for a fully controlled composite converter based on droop control, characterized in that, The fully controlled composite converter includes a port for connecting to the AC power grid, a main valve, and a support valve. The method includes: The system acquires grid synchronization information, the dq-axis component of AC current, the outer loop voltage reference value of the support valve, and the inner loop active current reference value of the support valve. The grid synchronization information is the power synchronization phase angle of the AC grid. The dq-axis component of AC current includes the d-axis component and the q-axis component of AC current in a two-phase rotating coordinate system. The outer loop voltage reference value is the reference value of the bus AC voltage, and the inner loop active current reference value is the reference value of the d-axis component of AC current in a two-phase rotating coordinate system. The inner loop reactive current reference value is determined at least based on the outer loop voltage reference value, wherein the inner loop reactive current reference value is the reference value of the q-axis component of the AC current in the two-phase rotating coordinate system. Based on the inner loop reactive current reference value, the inner loop active current reference value, the AC current dq axis component, and the power grid synchronization information, a first control signal is determined, and the first control signal is used to control the support valve to adjust the inner loop reactive current and inner loop active current of the support valve. Based at least on the power grid synchronization information, a second control signal is determined, and the second control signal is used to control and adjust the active and reactive power of the main valve.

2. The method according to claim 1, characterized in that, Obtain power grid synchronization information, including: Obtain the first active power, the first active power reference value, and the rated angular frequency of the AC power grid, wherein the first active power is the active power of the AC power grid, and the first active power reference value is the reference value of the first active power. Calculate the difference between the first active power reference value and the first active power to obtain the first difference; The first difference is subjected to low-pass filtering to obtain a first filtered value, and the product of the first filtered value and the active branch droop coefficient is calculated to obtain the first parameter. The second parameter is obtained by summing the first parameter with the rated angular frequency. The second parameter is input into the integrator to obtain the power synchronization phase.

3. The method according to claim 1, characterized in that, Obtaining the outer loop voltage reference value of the support valve includes: Obtain the first reactive power, the first reactive power reference value, and the rated voltage amplitude of the AC power grid, wherein the first reactive power is the reactive power of the AC power grid, and the first reactive power reference value is the reference value of the first reactive power. Calculate the difference between the first reactive power reference value and the first reactive power to obtain the second difference; The second difference is subjected to low-pass filtering to obtain the second filtered value, and the product of the second filtered value and the reactive branch droop coefficient is calculated to obtain the third parameter. The sum of the third parameter and the rated voltage amplitude is calculated to obtain the reference value of the outer loop voltage of the support valve.

4. The method according to claim 1, characterized in that, Obtaining the dq-axis components of the alternating current includes: Obtain the three-phase AC current of the support valve; The three-phase alternating current is subjected to coordinate transformation to obtain the dq-axis component of the alternating current. The dq-axis component of the alternating current is the dq-axis component of the three-phase alternating current in a two-phase rotating coordinate system.

5. The method according to claim 1, characterized in that, Determine the inner loop reactive current reference value based at least on the outer loop voltage reference value, including: Obtain the AC voltage of the busbar, and calculate the difference between the outer loop voltage reference value of the support valve and the AC voltage of the busbar to obtain the third difference value; The third difference is input to the proportional-integral controller to obtain the inner loop reactive current reference value.

6. The method according to claim 1, characterized in that, Obtaining the reference value of the inner loop active current of the support valve includes: Obtain the second active power and the second active power reference value, wherein the second active power is the active power of the support valve, and the second active power reference value is the reference value of the second active power. Calculate the difference between the second active power reference value and the second active power to obtain the fourth difference value; The fourth difference is input to the proportional-integral controller to obtain the reference value of the inner loop active current of the support valve.

7. The method according to claim 1, characterized in that, Based on the inner loop reactive current reference value, the inner loop active current reference value, the dq-axis component of the AC current, and the grid synchronization information, a first control signal is determined, including: The difference between the inner loop reactive current reference value and the q-axis component of the AC current in the two-phase rotating coordinate system is calculated to obtain the fifth difference value; The fifth difference is input to the proportional-integral controller to obtain the first voltage modulation signal; The sixth difference is obtained by calculating the difference between the inner loop active current reference value and the d-axis component of the AC current in the two-phase rotating coordinate system. The sixth difference is input to the proportional-integral controller to obtain the second voltage modulation signal; The first voltage modulation signal and the second voltage modulation signal are subjected to coordinate inverse transformation to obtain a voltage sinusoidal modulation signal; The voltage sinusoidal modulation signal is subjected to near-level approximation modulation processing to obtain the first control signal.

8. The method according to claim 1, characterized in that, Determine the second control signal based at least on the power grid synchronization information, including: Obtain the capacitor voltage and second reactive power of the submodule of the support valve, wherein the second reactive power is the reactive power of the support valve; The capacitor voltage of the submodule of the support valve is subjected to negative feedback regulation to obtain the first current modulation signal; The second reactive power is subjected to negative feedback regulation to obtain the second current modulation signal; The first current modulation signal and the second current modulation signal are subjected to coordinate inverse transformation to obtain a current sinusoidal modulation signal. The current sinusoidal modulation signal is subjected to pulse width modulation processing to obtain the second control signal.

9. The method according to claim 8, characterized in that, The capacitor voltage is subjected to negative feedback regulation to obtain a first current modulation signal, including: Obtain the reference value of the capacitor voltage of the sub-module of the support valve, and calculate the difference between the reference value of the capacitor voltage of the sub-module of the support valve and the capacitor voltage of the sub-module of the support valve to obtain the seventh difference value. The seventh difference is input to the proportional-integral controller to obtain the first current modulation signal.

10. The method according to claim 8, characterized in that, The second reactive power is subjected to negative feedback regulation to obtain a second current modulation signal, including: Obtain a second reactive power reference value, which is a reference value for the second reactive power, and calculate the difference between the second reactive power reference value and the second reactive power to obtain an eighth difference value; The eighth difference is input to the proportional-integral controller to obtain the second current modulation signal.

11. A grid control device for a fully controlled composite converter based on droop control, characterized in that, The fully controlled composite converter includes a port for connecting to the AC power grid, a main valve, and a support valve. The device includes: The acquisition unit is used to acquire grid synchronization information, the dq-axis component of AC current, the outer loop voltage reference value of the support valve, and the inner loop active current reference value of the support valve. The grid synchronization information is the power synchronization phase angle of the AC grid. The dq-axis component of AC current includes the d-axis component and the q-axis component of AC current in a two-phase rotating coordinate system. The outer loop voltage reference value is the reference value of the bus AC voltage, and the inner loop active current reference value is the reference value of the d-axis component of AC current in a two-phase rotating coordinate system. The determining unit is used to determine the inner loop reactive current reference value based at least on the outer loop voltage reference value, wherein the inner loop reactive current reference value is a reference value of the q-axis component of the AC current in a two-phase rotating coordinate system. The first control unit is used to determine a first control signal based on the inner loop reactive current reference value, the inner loop active current reference value, the AC current dq axis component and the power grid synchronization information, and use the first control signal to control the support valve to adjust the inner loop reactive current and inner loop active current of the support valve. The second control unit is configured to determine a second control signal based at least on the power grid synchronization information, and use the second control signal to control the main valve to adjust the active power and reactive power of the main valve.

12. A DC transmission system, characterized in that, include: DC power transmission terminal; The DC power receiving end is electrically connected to the DC power sending end; A controller is communicatively connected to the DC transmission end, wherein the controller is used to execute the grid control method for a fully controlled composite converter based on droop control as described in any one of claims 1 to 10.

Images