Network configuration control method of full-controlled composite converter based on droop control

Abstract

The application provides a network construction control method of a full-control composite converter based on droop control. The converter comprises a port for accessing an alternating current power grid, a main valve, and a support valve. The method comprises: acquiring power grid synchronization information, alternating current dq-axis components, an outer loop voltage reference value of the support valve, and an inner loop active current reference value of the support valve; determining an inner loop reactive current reference value according to at least the outer loop voltage reference value; determining a first control signal according to the inner loop reactive current reference value, the inner loop active current reference value, the alternating current dq-axis components, and the power grid synchronization information, and performing inner loop control and outer loop control on the support valve by using the first control signal; and determining a second control signal according to at least the power grid synchronization information, and performing reactive power control on the main valve by using the second control signal. The method can improve the stability of the operation of the converter.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of direct current transmission, in particular to a network construction control method of a full-control composite converter based on droop control, a network construction control device of a full-control composite converter based on droop control and a direct current transmission system. BACKGROUND

[0002] UHVDC transmission has become a key technology to balance the contradiction between energy resource distribution and load demand due to its unique advantages, such as large capacity transmission, long distance coverage, low loss and high efficiency of transmission corridor utilization. As a core component of HVDC project, the performance of UHVDC converter directly affects the efficiency of power transmission and the reliability of the system. However, the traditional DC converter has exposed some obvious limitations when facing large-scale access of new energy. With the increase of new energy penetration rate, the short circuit ratio of the power grid gradually decreases, which leads to the weakening of the dynamic reactive power support capability of the power grid. In addition, in extreme cases such as island operation mode, the traditional converter is difficult to independently build stable AC voltage and frequency, thereby affecting the feasibility of large-scale sending and grid connection of new energy.

[0003] Therefore, there is an urgent need for a network construction control method of a full-control composite converter based on droop control to improve the stability of converter operation. SUMMARY

[0004] The main purpose of the present application is to provide a network construction control method of a full-control composite converter based on droop control, a network construction control device of a full-control composite converter based on droop control and a direct current transmission system, to at least solve the problem of how to improve the stability of converter operation in the prior art.

[0005] To achieve the above object, according to one aspect of the present application, a network configuration control method of a full-controlled composite converter based on droop control is provided, the full-controlled composite converter comprising a port for accessing an AC power grid, a main valve and a support valve, the method comprising: obtaining grid synchronization information, AC current dq-axis components, an outer-loop voltage reference value of the support valve and an inner-loop active current reference value of the support valve, wherein the grid synchronization information is a power synchronization phase angle of the AC power grid, the AC current dq-axis components comprise a d-axis component of an AC current in a two-phase rotating coordinate system and a q-axis component of the AC current in the two-phase rotating coordinate system, the outer-loop voltage reference value is a reference value of a bus AC voltage, and the inner-loop active current reference value is a reference value of the d-axis component of the AC current in the two-phase rotating coordinate system; determining an inner-loop reactive current reference value according to at least 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 the two-phase rotating coordinate system; determining a first control signal according to the inner-loop reactive current reference value, the inner-loop active current reference value, the AC current dq-axis components and the grid synchronization information, and controlling the support valve by using the first control signal to adjust an inner-loop reactive current and an inner-loop active current of the support valve; determining a second control signal according to at least the grid synchronization information, and controlling the main valve by using the second control signal to adjust an active power and a reactive power of the main valve.

[0006] Optionally, obtaining the grid synchronization information comprises: obtaining a first active power, a first active power reference value and a rated angular frequency of the AC power grid, the first active power being an active power of the AC power grid, and the first active power reference value being a reference value of the first active power; calculating a 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 a product of the first filtered value and an active branch droop coefficient to obtain a first parameter; calculating a 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, the outer loop voltage reference value of the support valve is obtained by: obtaining a first reactive power, a first reactive power reference value, and a rated voltage amplitude of the alternating current power grid; the first reactive power is a reactive power of the alternating current power grid; the first reactive power reference value is a reference value of the first reactive power; calculating a difference between the first reactive power reference value and the first reactive power to obtain a second difference; performing low-pass filtering on the second difference to obtain a second filtered value; and calculating a product of the second filtered value and a reactive branch droop coefficient to obtain a third parameter; and calculating a sum of the third parameter and the rated voltage amplitude to obtain the outer loop voltage reference value of the support valve.

[0008] Optionally, the alternating current dq-axis component is obtained by: obtaining three-phase alternating currents of the support valve; and performing coordinate inversion conversion on the three-phase alternating currents to obtain the alternating current dq-axis component, which is a dq-axis component of the three-phase alternating currents in a two-phase rotating coordinate system.

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

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

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

[0012] Optionally, the second control signal is determined according to the grid synchronization information, comprising: obtaining a capacitor voltage of the sub-module of the support valve and a second reactive power, the second reactive power being a reactive power of the support valve; performing negative feedback adjustment processing on the capacitor voltage of the sub-module of the support valve to obtain a first current modulation signal; performing negative feedback adjustment processing on the second reactive power to obtain a second current modulation signal; performing coordinate inversion processing on the first current modulation signal and the second current modulation signal to obtain a current sinusoidal modulation signal; and performing pulse width modulation processing on the current sinusoidal modulation signal to obtain the second control signal.

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

[0014] Optionally, the negative feedback adjustment processing on the second reactive power to obtain the second current modulation signal comprises: obtaining a second reactive power reference value, the second reactive power reference value being a reference value of the second reactive power, and calculating a 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 into a proportional-integral controller to obtain the second current modulation signal.

[0015] To achieve the above object, according to one aspect of the present application, there is provided a network configuration control device of a full-controlled composite converter based on droop control, the full-controlled composite converter comprising a port for accessing an AC power grid, a main valve and a support valve, the device comprising: an acquisition unit configured to acquire grid synchronization information, AC current dq-axis components, an outer-loop voltage reference value of the support valve, and an inner-loop active current reference value of the support valve, wherein the grid synchronization information is a power synchronization phase angle of the AC power grid, the AC current dq-axis components comprise a d-axis component of an AC current in a two-phase rotating coordinate system and a q-axis component of the AC current in the two-phase rotating coordinate system, the outer-loop voltage reference value is a reference value of a bus AC voltage, and the inner-loop active current reference value is a reference value of the d-axis component of the AC current in the two-phase rotating coordinate system; a determination unit configured to determine an inner-loop reactive current reference value according to at least 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 the two-phase rotating coordinate system; a first control unit configured to determine a first control signal according to the inner-loop reactive current reference value, the inner-loop active current reference value, the AC current dq-axis components and the grid synchronization information, and to control the support valve by using the first control signal to adjust an inner-loop reactive current and an inner-loop active current of the support valve; and a second control unit configured to determine a second control signal according to at least the grid synchronization information, and to control the main valve by using the second control signal to adjust an active power of the main valve and a reactive power of the main valve.

[0016] According to another aspect of the present application, there is provided a DC power transmission system comprising a DC power transmission sending end and a DC power transmission receiving end, the DC power transmission sending end adopting any one of the network configuration control methods of the full-controlled composite converter based on droop control.

[0017] The technical scheme of the application provides a network construction control method of a full-control composite converter based on droop control, which is applied to the full-control composite converter, and the full-control composite converter comprises a port for connecting to an AC power grid, a main valve and a support valve. First, power grid synchronization information, AC current dq-axis components, an outer loop voltage reference value of the support valve and an inner loop active current reference value of the support valve are obtained. Then, the inner loop reactive current reference value is determined according to at least the outer loop voltage reference value. Then, a first control signal is determined according to the inner loop reactive current reference value, the inner loop active current reference value, the AC current dq-axis components and the power grid synchronization information, and the first control signal is used for inner loop control and outer loop control of the support valve. At the same time, a second control signal is determined according to at least the power grid synchronization information, and the second control signal is used for active power control and reactive power control of the main valve. The first control signal can realize double closed loop control of the voltage and current of the support valve, and ensure the stability of the capacitor voltage of the support valve sub-module and the effective control of the output current. The second control signal can be used for active control and reactive control of the main valve, and through the control of the turn-on and turn-off of each phase bridge arm in the main valve, large-capacity active power transmission and additional reactive power support for the power grid can be realized, and the stability of the converter operation can be improved. BRIEF DESCRIPTION OF DRAWINGS

[0018] The drawings constituting a part of the specification of the application are used to provide further understanding of the application, the illustrative embodiments of the application and the description thereof are used to explain the application, and do not constitute improper limitation on the application. In the drawings:

[0019] Figure 1 A hardware structure block diagram of a mobile terminal for executing a network construction control method of a full-control composite converter based on droop control is shown according to an embodiment provided by the application;

[0020] Figure 2 A structure schematic diagram of a full-control composite converter is shown according to an embodiment provided by the application;

[0021] Figure 3 A flow schematic diagram of a network construction control method of a full-control composite converter based on droop control is shown according to an embodiment provided by the application;

[0022] Figure 4 A specific flow schematic diagram of another network construction control method of a full-control composite converter based on droop control is shown according to an embodiment provided by the application;

[0023] Figure 5 A specific flow schematic diagram of power synchronization phase generation is shown according to an embodiment provided by the application;

[0024] Figure 6A specific flowchart diagram for generating an outer ring voltage reference value of a support valve is shown according to an embodiment of the present application;

[0025] Figure 7 A specific flowchart diagram for generating an alternating current dq axis component is shown according to an embodiment of the present application;

[0026] Figure 8 A specific flowchart diagram for generating an inner ring active current reference value of a support valve is shown according to an embodiment of the present application;

[0027] Figure 9 A specific flowchart diagram for generating an inner ring reactive current reference value is shown according to an embodiment of the present application;

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

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

[0030] Figure 12 A structural block diagram of a network construction control device of a full-control composite converter based on droop control is shown according to an embodiment of the present application.

[0031] Among the above figures, the following reference signs are included:

[0032] 102, processor; 104, memory; 106, transmission device; 108, input and output device; 110, alternating current power grid; 112, main valve; 114, support valve. DETAILED DESCRIPTION

[0033] It should be noted that the embodiments and features in the present application can be combined with each other without conflict. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0034] In order 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 described clearly and completely below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present application, not all. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor should be within the scope of protection of the present application.

[0035] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application and the above drawings are used to distinguish similar objects, and do not necessarily have to describe a specific order or sequence. It should be understood that the data thus used can be interchanged under appropriate circumstances, so that the embodiments of the present application described herein can be implemented. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion, for example, a process, method, system, product or device including a series of steps or units does not have to be limited to those steps or units clearly listed, but can include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0036] As introduced in the background, the operating stability of the converter in the prior art is not ideal. To solve the above problems, the embodiments of the present application provide a network construction control method of a full-control composite converter based on droop control, a network construction control device of a full-control composite converter based on droop control and a direct current power transmission system.

[0037] The technical solutions in the embodiments of the present application will be described clearly and completely in combination with the drawings in the embodiments of the present application.

[0038] The method embodiments provided in the embodiments of the present application can be executed in a mobile terminal, a computer terminal or similar computing devices. Taking the case of running on a mobile terminal, Figure 1 is a hardware structure block diagram of a mobile terminal of a network construction control method of a full-control composite converter based on droop control. As shown in Figure 1 , the mobile terminal can include one or more (only one is shown in Figure 1 ) processor 102 (the processor 102 can include but not limited to a processing device such as a microprocessor MCU or a programmable logic device FPGA) and a memory 104 for storing data, wherein the above mobile terminal can also include a transmission device 106 for communication function and an input and output device 108. Those skilled in the art can understand, Figure 1 The structure shown is only schematic, which does not limit the structure of the above mobile terminal. For example, the mobile terminal can also include more or less components than Figure 1 shown, or have a different configuration from Figure 1 shown.

[0039] The memory 104 can be used to store computer programs, such as software programs of application software and modules, such as the computer program corresponding to the network configuration control method of the full-controlled composite converter based on droop control in the embodiments of the present application. The processor 102 can execute various functional applications and data processing, i.e., implement the above method, by running the computer program stored in the memory 104. The memory 104 can include a high-speed random access memory, and can further include a non-volatile memory, such as one or more magnetic storage devices, flash memories, or other non-volatile solid-state memories. In some examples, the memory 104 can further include a memory remotely arranged with respect to the processor 102, which can be connected to the mobile terminal through a network. Examples of the above network include, but are not limited to, the Internet, an intranet, a local area network, a mobile communication network, and a combination thereof. The transmission device 106 is used to receive or send data via a network. The specific examples of the above network can include a wireless network provided by a communication provider of the mobile terminal. In one example, the transmission device 106 includes a network adapter (NIC), which can be connected to other network devices through a base station so as to communicate with the Internet. In one example, the transmission device 106 can be a radio frequency (RF) module, which is used to communicate with the Internet in a wireless manner.

[0040] In the embodiments of the present application, a network configuration control method of a full-controlled composite converter based on droop control running on a mobile terminal, a computer terminal or a similar computing device is provided. It should be noted that the steps shown in the flowchart of the accompanying drawings can be executed in a computer system such as a set of computer executable instructions, and although a logical order is shown in the flowchart, in some cases, the steps shown or described herein can be executed in an order different from that shown.

[0041] Figure 2 FIG. 1 is a structural schematic diagram of a full-controlled composite converter according to the embodiments of the present application. The full-controlled composite converter includes a port for accessing an AC power grid 110, a main valve 112 and a support valve 114. The main valve 112 includes three phases ABC, and each phase includes a plurality of sub-modules SM, dc The support valve 114 includes three phases ABC, and each phase includes a plurality of sub-modules SM, Figure 3 FIG. 2 is a flowchart of a network configuration control method of a full-controlled composite converter based on droop control according to the embodiments of the present application. As shown in FIG. 2, the method includes the following steps: Figure 3

[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 inner loop current control module is connected to the outer loop reactive power control module and the outer loop active power control module. ac The outer loop AC voltage control module is connected to the outer loop voltage reference value U ac The inner loop current control module is connected to the outer loop reactive power control module and the outer loop active power control module. sq_ref The inner loop current control module is connected to the outer loop reactive power control module and the outer loop active power control module. sq_ref The inner loop current control module is connected to the outer loop reactive power control module and the outer loop active power control module. sd_ref The inner loop current control module is connected to the outer loop reactive power control module and the outer loop active power control module. sq_ref The inner loop current control module is connected to the outer loop reactive power control module and the outer loop active power control module. sd_ref The inner loop current control module is connected to the outer loop reactive power control module and the outer loop active power control module. sd The inner loop current control module is connected to the outer loop reactive power control module and the outer loop active power control module. sq The inner loop current control module is connected to the outer loop reactive power control module and the outer loop active power control module. sa The inner loop current control module is connected to the outer loop reactive power control module and the outer loop active power control module. sb The inner loop current control module is connected to the outer loop reactive power control module and the outer loop active power control module. sc The inner loop current control module is connected to the outer loop reactive power control module and the outer loop active power control module. sa The inner loop current control module is connected to the outer loop reactive power control module and the outer loop active power control module. sb The inner loop current control module is connected to the outer loop reactive power control module and the outer loop active power control module. sc The inner loop current control module is connected to the outer loop reactive power control module and the outer loop active power control module. c1-6 The inner loop current control module is connected to the outer loop reactive power control module and the outer loop active power control module. c1-6 The inner loop current control module is connected to the outer loop reactive power control module and the outer loop active power control module.

[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*The active current reference value i sd_ref of the inner loop can be obtained by comparing the second active power reference value U with the PI controller.

[0058] The step S202 can also be implemented in other ways, for example: step S2021, obtaining the bus AC voltage and calculating the difference between the outer loop voltage reference value U of the support valve and the bus AC voltage to obtain a third difference; step S2022, inputting the third difference into 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, as shown in Figure 9 , the AC voltage of the converter is controlled by the reactive control loop, wherein the outer loop voltage reference value U ac of the support valve is output by the reactive droop control link. ac The bus AC voltage U ac is compared with U ac to obtain the outer loop voltage reference value U sq_ref of the support valve.

[0060] In some embodiments, the step S203 can be implemented by the following steps: step S2031, calculating 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, inputting the fifth difference into the proportional-integral controller to obtain a first voltage modulation signal; step S2033, 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 to obtain a sixth difference; step S2034, inputting the sixth difference into the proportional-integral controller to obtain a second voltage modulation signal; step S2035, performing coordinate inverse conversion processing on the first voltage modulation signal and the second voltage modulation signal to obtain a voltage sinusoidal modulation signal; step S2036, performing nearest level approximation modulation processing on the voltage sinusoidal modulation signal to obtain the first control signal. The above method can further quickly generate the first control signal.

[0061] As shown in Figure 10 , the d-axis component i sd of the AC current is compared with the inner loop active current reference value i sd_ref , the q-axis component i sq of the AC current is compared with the inner loop reactive current reference value i sq_ref , and the PI control is performed to obtain the dq-axis modulation signal of the support valve output voltage, i.e. the first voltage modulation signal u sqwith the second voltage modulation signal u sd , the output voltage sinusoidal modulation signal u sa、 can be obtained through coordinate inverse transformation. sb and u sc . The voltage sinusoidal modulation signal u sj can be obtained through nearest level modulation to obtain the switching signals S sa , S sb , S sc supporting the valves of each sub-module. In each sub-module, four fully controlled IGBT devices are used. The switching signals of each device need to be sent, in which the triggering and turn-off of each device of the valve bridge arm are different, and the nearest level modulation algorithm is used to calculate the switching time of each device and send it to the device one by one. Since the three-phase modulation waves are 120° apart, and the nearest level modulation (NLM) depends on the output modulation wave signal to generate the switching signal of the corresponding phase, the expression is simplified as S sa , S sb , S sc , in which the A-phase switching signal S sa is taken as an example. S sa contains the switching signals of all power devices in the A-phase sub-module, which is equivalent to a four-dimensional array, which refers to the four devices in the full-bridge module. The length of the array represents the number of bridge arm sub-modules, and thus the power control of the supporting valve is completed.

[0062] The step S204 can be implemented by the following steps: in step S2041, the capacitor voltage of the sub-module of the supporting valve and the second reactive power are obtained, and the second reactive power is the reactive power of the supporting valve; in step S2042, the capacitor voltage of the sub-module of the supporting valve is negatively feedback adjusted to obtain a first current modulation signal; in step S2043, the second reactive power is negatively feedback adjusted to obtain a second current modulation signal; in step S2044, the first current modulation signal and the second current modulation signal are coordinate inverted to obtain a current sinusoidal modulation signal; and in step S2045, the current sinusoidal modulation signal is pulse width modulated to obtain the second control signal. When the main valve works in the PWM mode, the control of the reactive power of the main valve can be further implemented.

[0063] In some other embodiments, the step S204 can also be implemented by the following method: determining whether the triggering angle of the main valve is in a predetermined range; and in the case that the triggering angle of the main valve is in the predetermined range, controlling the power semiconductor devices of the main valve to maintain turn-off. 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 current sinusoidal modulation signal is subjected to pulse width modulation (PWM) to obtain the switching signal S of each phase bridge arm of the main valve c1-6 . Taking the case of using the device direct series mode for each bridge arm of the single phase of the main valve, all devices of the bridge arm are triggered or turned off at the same time, and the main valve contains six bridge arms in total, which means that six trigger signals are needed, wherein the power synchronous phase angle θ required for coordinate transformation is generated by the active droop control module, and synchronization can be completed.

[0067] The embodiment of the present application also provides a network construction control device of a droop control based fully-controlled composite converter. It should be noted that the network construction control device of the droop control based fully-controlled composite converter of the embodiment of the present application can be used to execute the network construction control method for the droop control based fully-controlled composite converter provided by the embodiment of the present application. The device is used to realize the above-mentioned embodiment and preferred embodiment, and details are not repeated. As used below, the term "module" can be a combination of software and / or hardware that realizes a predetermined function. Although the device described in the following embodiment is preferably realized in software, hardware, or a combination of software and hardware is also possible and is conceived.

[0068] The network construction control device of the droop control based fully-controlled composite converter provided by the embodiment of the present application is introduced below.

[0069] Figure 12 is a schematic diagram of the network construction control device of the droop control based fully-controlled composite converter according to the embodiment of the present application. As Figure 12 shown, the device includes:

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

[0071] The determination unit 20 is used to determine an inner loop reactive current reference value according to at least 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 alternating 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 component i sd and i sqand the power synchronization phase angle θ, output a first control signal S sa , S sb , S sc and the first control signal S sa , S sb , S sc controls the support valve; the reactive power control module is configured to output a second control signal S c1-6 and the second control signal S c1-6 controls the main valve. The active power droop control module is configured to implement active power droop control, and the reactive power droop control module is configured to implement reactive power droop control. The method combines active power droop control and reactive power droop control, eliminates a traditional phase-locked loop, and enables the converter to actively build a frequency and bus voltage according to an actual load power.

[0075] The embodiment provides a network construction control device of a full-control composite converter based on droop control. The method is applied to a converter, and the converter comprises a port for accessing an alternating current power grid, a main valve, and a support valve. An acquisition unit acquires power grid synchronization information, alternating current dq-axis components, an outer loop voltage reference value of the support valve, and an inner loop active current reference value of the support valve. A determination unit determines an inner loop reactive current reference value according to at least the outer loop voltage reference value. A first control unit determines a first control signal according to the inner loop reactive current reference value, the inner loop active current reference value, the alternating current dq-axis components, and the power grid synchronization information, and performs inner loop control and outer loop control on the support valve by using the first control signal. A second control unit determines a second control signal according to at least the power grid synchronization information, and performs active power control and reactive power control on the main valve by using the second control signal. The first control signal can be used for double closed loop control of voltage and current of the support valve, ensuring stability of a capacitor voltage of a support valve sub-module and effective control of an output current. The second control signal can be used for active control and reactive control of the main valve. By controlling turn-on and turn-off of each phase bridge arm in the main valve, large-capacity active power transmission and additional reactive power support for the power grid can be achieved, and stability of converter operation can be improved.

[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 jIn the case of >90℃, automatically reduce the active branch droop coefficient , raise the reactive branch droop coefficient , preferentially sacrifice active power and retain reactive power; at the same time, an event triggering mechanism is adopted, and a three-dimensional lookup table is updated once every 1ms to avoid frequent jitter.

[0082] In order to further quickly obtain the above-mentioned alternating current dq axis component, the above-mentioned acquisition unit further comprises a third acquisition module and a third processing module, wherein the third acquisition module is configured to acquire the three-phase alternating current of the support valve; the third processing module is configured to perform coordinate conversion processing on the three-phase alternating current to obtain the alternating current dq axis component, and the alternating current dq axis component is the dq axis component of the three-phase alternating current in a two-phase rotating coordinate system.

[0083] Specifically, as shown in Figure 7 , the three-phase alternating current i s_abc of the support valve is subjected to coordinate transformation to obtain the dq axis current component actual value i sd and i sq in the two-phase rotating coordinate system. Wherein, the power synchronization phase angle θ required for coordinate transformation is generated by the active droop control module, and synchronization can be completed.

[0084] The above-mentioned acquisition unit further comprises a fourth acquisition module, a fifth calculation module and a second input module, wherein the fourth acquisition module is configured to acquire the second active power and the second active power reference value, 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; the fifth calculation module is configured to calculate the difference between the second active power reference value and the second active power to obtain a fourth difference value; and the second input module is configured to input the fourth difference value to a proportional-integral controller to obtain the inner loop active current reference value of the support valve. The above-mentioned device can further improve the accuracy of the inner loop active current reference value calculation.

[0085] Specifically, as shown in Figure 8 , the acquired second active power P svg is compared with the second active power reference value P svg , and the inner loop active current reference value i sd_ref can be obtained through the PI controller. The initial value of the second active power reference value can be 0.

[0086] The determining unit comprises a fifth acquisition module and a third input module. The fifth acquisition module is configured to acquire the bus AC voltage and calculate a difference between the outer loop voltage reference value of the support valve and the bus AC voltage to obtain a third difference value. The third input module is configured to input the third difference value into a proportional-integral controller to obtain the inner loop reactive current reference value. The device can further improve the calculation accuracy of the inner loop reactive current reference value.

[0087] Specifically, as shown in Figure 9 , the AC voltage of the essential converter is controlled by a reactive control loop, wherein the outer loop voltage reference value U ac * of the support valve is output by a reactive droop control link, and the acquired bus AC voltage U ac is compared with U ac * to obtain the outer loop voltage reference value U ac * of the support valve, and the inner loop reactive current reference value i sq_ref is obtained through a PI controller.

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

[0089] As shown in Figure 10 , the d-axis component i sd of the AC current is compared with the inner loop active current reference value i sd_ref , the q-axis component i sq of the AC current is compared with the inner loop reactive current reference value i sq_ref , and PI control is performed to obtain the dq-axis modulation signal of the support valve output voltage, i.e., the first voltage modulation signal u sq and the second voltage modulation signal u sd , and coordinate inverse conversion is performed to obtain the output voltage sinusoidal modulation signal usj (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 current sine modulation signal is subjected to carrier modulation to obtain the switching signal S of each phase bridge arm of the main valve c1-6 For example, in the case of using the device direct series mode for each bridge arm of the single phase of the main valve, all the devices of the bridge arm are triggered or turned off at the same time, and the main valve includes six bridge arms in total, which means that six trigger signals are needed, wherein the power synchronous phase angle θ required for coordinate transformation is generated by the active droop control module, and synchronization can be completed.

[0095] The application also provides a direct current transmission system, including a direct current transmission sending end and a direct current transmission receiving end, and the direct current transmission sending end adopts any one of the network construction control methods of the full-control composite converter based on droop control.

[0096] Therefore, the converter has a voltage source external characteristic, and can realize reliable grid connection and external transmission in an extremely low short-circuit ratio or even an island scenario.

[0097] The network construction control device of the full-control composite converter based on droop control includes a processor and a memory, and the acquisition unit, the determination unit, the first control unit and the second control unit are all stored in the memory as program units, and the corresponding functions are realized by the processor executing the program units stored in the memory. The modules are located in the same processor; or the modules are located in different processors in any combination.

[0098] The processor includes a core, and the core retrieves the corresponding program unit from the memory. The core can be one or more, and the converter is controlled by adjusting the core parameters.

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

[0100] The embodiment of the application provides a computer readable storage medium, and the computer readable storage medium includes a stored program, wherein when the program runs, the device where the computer readable storage medium is located executes the network construction control method of the full-control composite converter based on droop control.

[0101] Specifically, the network construction control method of the full-control composite converter based on droop control includes:

[0102] Step S201, obtaining grid synchronization information, alternating current dq axis component, outer ring voltage reference value of the support valve, and inner ring active current reference value of the support valve, wherein the grid synchronization information is a power synchronization phase angle of the alternating current grid, the alternating current dq axis component includes a d-axis component of the alternating current in a two-phase rotating coordinate system and a q-axis component of the alternating current in the two-phase rotating coordinate system, the outer ring voltage reference value is a reference value of a bus alternating current voltage, and the inner ring active current reference value is a reference value of the d-axis component of the alternating current in the two-phase rotating coordinate system;

[0103] Step S202, determining an inner ring reactive current reference value according to at least the outer ring voltage reference value, wherein the inner ring reactive current reference value is a reference value of a q-axis component of the alternating current in the two-phase rotating coordinate system;

[0104] Step S203, 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 grid synchronization information, and controlling the support valve by using the first control signal to adjust the inner ring reactive current and the inner ring active current of the support valve;

[0105] Step S204, determining a second control signal according to at least the grid synchronization information, and controlling the main valve by using the second control signal to adjust the active power and the reactive power of the main valve.

[0106] An embodiment of the present application provides a processor, which is used for running a program, wherein the program performs the grid-forming control method of the full-control composite converter based on droop control when running.

[0107] Specifically, the grid-forming control method of the full-control composite converter based on droop control comprises:

[0108] Step S201, obtaining grid synchronization information, alternating current dq axis component, outer ring voltage reference value of the support valve, and inner ring active current reference value of the support valve, wherein the grid synchronization information is a power synchronization phase angle of the alternating current grid, the alternating current dq axis component includes a d-axis component of the alternating current in a two-phase rotating coordinate system and a q-axis component of the alternating current in the two-phase rotating coordinate system, the outer ring voltage reference value is a reference value of a bus alternating current voltage, and the inner ring active current reference value is a reference value of the d-axis component of the alternating current in the two-phase rotating coordinate system;

[0109] Step S202, determining an inner ring reactive current reference value according to at least the outer ring voltage reference value, wherein the inner ring reactive current reference value is a reference value of a q-axis component of the alternating current in the two-phase rotating coordinate system;

[0110] Step S203, determining a first control signal according to the inner loop reactive current reference value, the inner loop active current reference value, the AC current dq axis component and the grid synchronization information, and controlling the support valve by using the first control signal to adjust the inner loop reactive current and the inner loop active current of the support valve;

[0111] Step S204, determining a second control signal according to at least the grid synchronization information, and controlling the main valve by using the second control signal to adjust the active power and the reactive power of the main valve.

[0112] The device provided by the embodiment of the present application comprises a processor, a memory and a program stored in the memory and executable on the processor, and the processor implements at least the following steps when executing the program:

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

[0114] Step S202, determining an inner loop reactive current reference value according to at least 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 the two-phase rotating coordinate system;

[0115] Step S203, determining a first control signal according to the inner loop reactive current reference value, the inner loop active current reference value, the AC current dq axis component and the grid synchronization information, and controlling the support valve by using the first control signal to adjust the inner loop reactive current and the inner loop active current of the support valve;

[0116] Step S204, determining a second control signal according to at least the grid synchronization information, and controlling the main valve by using the second control signal to adjust the active power and the reactive power of the main valve.

[0117] The device herein can be a server, a PC, a PAD, a mobile phone or the like.

[0118] The present application further provides a computer program product adapted to execute a program which initializes at least the following method steps when executed on a data processing device:

[0119] In step S201, grid synchronization information, alternating current dq-axis components, an outer loop voltage reference value of the support valve, and an inner loop active current reference value of the support valve are obtained, wherein the grid synchronization information is a power synchronization phase angle of the alternating current grid, the alternating current dq-axis components include a d-axis component of the alternating current in a two-phase rotating coordinate system and a q-axis component of the alternating current in the two-phase rotating coordinate system, the outer loop voltage reference value is a reference value of a bus alternating current voltage, and the inner loop active current reference value is a reference value of the d-axis component of the alternating current in the two-phase rotating coordinate system;

[0120] In step S202, an inner loop reactive current reference value is determined according to at least 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 alternating current in the two-phase rotating coordinate system;

[0121] In step S203, a first control signal is determined according to the inner loop reactive current reference value, the inner loop active current reference value, the alternating current dq-axis components, and the grid synchronization information, and the support valve is controlled by using the first control signal to adjust the inner loop reactive current and the inner loop active current of the support valve;

[0122] In step S204, a second control signal is determined according to at least the grid synchronization information, and the main valve is controlled by using the second control signal to adjust the active power and the reactive power of the main valve.

[0123] Obviously, those skilled in the art should understand that the modules or steps of the present application can be realized by a general computing device, which can be concentrated on a single computing device or distributed on a network composed of multiple computing devices, and can be realized by program codes executable by the computing device, so that they can be stored in a storage device and executed by the computing device, and in some cases, the steps shown or described can be executed in different order, or they can be manufactured into individual integrated circuit modules or a single integrated circuit module. Therefore, the present application is not limited to any specific combination of hardware and software.

[0124] Those skilled in the art should understand that the embodiments of the present application can be provided as a method, a system, or a computer program product. Therefore, the present application can be in the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present application can be in the form of a computer program product implemented on one or more computer usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer usable program codes.

[0125] The computer program instructions can also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer-implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart block or blocks. Figure 1 one or more flow or blocks Figure 1 means for functionally implementing the steps listed in the flowchart block or blocks.

[0126] These computer program instructions can also be stored in a computer readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer readable memory produce an article of manufacture including instructions which implement the function specified in the flowchart block or blocks. Figure 1 one or more flow or blocks Figure 1 means for functionally implementing the steps listed in the flowchart block or blocks.

[0127] The computer program instructions can also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer-implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart block or blocks. Figure 1 one or more flow or blocks Figure 1 means for functionally implementing the steps listed in the flowchart block or blocks.

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

[0129] The memory can include non-persistent memory and / or volatile memory, such as random access memory (RAM) and / or cache memory, for storing, in general, data and / or program instructions. The memory can also include non-volatile memory, such as read only memory (ROM) and / or flash memory, for storing, in general, static data and / or instructions that are not very likely to ever change. The memory is an example of computer readable media.

[0130] Computer-readable media includes permanent and non-permanent, movable and non-movable media that can be implemented by any method or technology to store information. The information can be computer-readable instructions, data structures, program modules 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, compact disc read-only memory (CD-ROM), digital versatile disc (DVD) or other optical storage, magnetic cassette, magnetic disk storage or other magnetic storage devices, or any other non-transmission medium that can be used to store information accessible by a computing device. According to the definition herein, computer-readable media does not include transitory media such as modulated data signals and carriers.

[0131] The technical features of the above-described embodiments can be combined in any manner. In order to make the description concise, not all possible combinations of the technical features in the above-described embodiments are described, but as long as the combinations of the technical features do not exist contradictions, it should be considered as the scope of the present disclosure.

[0132] It should also be noted that the terms "comprising", "including", or any other variant thereof are intended to cover non-exclusive inclusion, so that processes, methods, articles or devices including a series of elements not only include those elements, but also include other elements not explicitly listed, or inherent to such processes, methods, articles or devices. Without more limitations, the element defined by the statement "comprising a" does not exclude the presence of other identical elements in the process, method, article or device including the element.

[0133] From the above description, it can be seen that the above-described embodiments of the present application achieve the following technical effects:

[0134] 1) The network construction control method of the full-control composite converter based on droop control of the application, which is applied to the full-control composite converter, and the full-control composite converter comprises a port for accessing an AC power grid, a main valve and a support valve. First, the grid synchronization information, the AC current dq-axis component, the outer loop voltage reference value of the support valve and the inner loop active current reference value of the support valve are obtained; then, the inner loop reactive current reference value is determined according to at least the outer loop voltage reference value; then, the first control signal is determined according to the inner loop reactive current reference value, the inner loop active current reference value, the AC current dq-axis component and the grid synchronization information, and the first control signal is used for inner loop control and outer loop control of the support valve; at the same time, the second control signal is determined according to at least the grid synchronization information, and the second control signal is used for active power control and reactive power control of the main valve. The voltage and current double-loop control of the support valve can be realized through the first control signal, the stability of the capacitor voltage of the support valve sub-module and the effective control of the output current are ensured, the active control and the reactive control of the main valve can be realized through the second control signal, the large-capacity active power transmission and the additional reactive power support for the power grid are realized by controlling the turn-on and turn-off of each phase bridge arm in the main valve, and the stability of the converter operation can be improved.

[0135] 2) The network construction control device of the full-control composite converter based on droop control of the application, which is applied to the full-control composite converter, and the full-control composite converter comprises a port for accessing an AC power grid, a main valve and a support valve. An obtaining unit obtains the grid synchronization information, the AC current dq-axis component, the outer loop voltage reference value of the support valve and the inner loop active current reference value of the support valve; a determining unit determines the inner loop reactive current reference value according to at least the outer loop voltage reference value; a first control unit determines the first control signal according to the inner loop reactive current reference value, the inner loop active current reference value, the AC current dq-axis component and the grid synchronization information, and the first control signal is used for inner loop control and outer loop control of the support valve; a second control unit determines the second control signal according to at least the grid synchronization information, and the second control signal is used for active power control and reactive power control of the main valve. The voltage and current double-loop control of the support valve can be realized through the first control signal, the stability of the capacitor voltage of the support valve sub-module and the effective control of the output current are ensured, the active control and the reactive control of the main valve can be realized through the second control signal, the large-capacity active power transmission and the additional reactive power support for the power grid are realized by controlling the turn-on and turn-off of each phase bridge arm in the main valve, and the stability of the converter operation can be improved.

[0136] The above only describes the preferred embodiments of the application and is not used to limit the application. Various modifications and changes can be made by those skilled in the art based on the principles and spirit of the application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the application shall be included in the protection scope of the application.

Claims

1. A network configuration control method of a full-controlled composite converter based on droop control, characterized in that, The full-control composite converter comprises a port for accessing an alternating current power grid, a main valve and a support valve, and the method comprises: obtaining grid synchronization information, alternating current dq-axis components, outer loop voltage reference values of the support valve, and inner loop active current reference values of the support valve, wherein the grid synchronization information is a power synchronization phase angle of the alternating current power grid, the alternating current dq-axis components comprise a d-axis component of alternating current in a two-phase rotating coordinate system and a q-axis component of the alternating current in the two-phase rotating coordinate system, the outer loop voltage reference values are reference values of bus alternating current voltage, and the inner loop active current reference values are reference values of the d-axis component of the alternating current in the two-phase rotating coordinate system; determining an inner loop reactive current reference value according to at least the outer loop voltage reference values, wherein the inner loop reactive current reference value is a reference value of the q-axis component of the alternating current in the two-phase rotating coordinate system; determining a first control signal according to the inner loop reactive current reference value, the inner loop active current reference value, the alternating current dq-axis components and the grid synchronization information, and controlling the support valve by using the first control signal to adjust inner loop reactive current and inner loop active current of the support valve; determining a second control signal according to at least the grid synchronization information, and controlling the main valve by using the second control signal to adjust active power and reactive power of the main valve, determining an inner loop reactive current reference value according to at least the outer loop voltage reference values, comprising: obtaining the bus alternating current voltage, and calculating a difference between the outer loop voltage reference values of the support valve and the bus alternating current voltage to obtain a third difference value; inputting the third difference value into a proportional-integral controller to obtain the inner loop reactive current reference value.

2. The method of claim 1, wherein, obtaining grid synchronization information, comprising: obtaining a first active power, a first active power reference value and a rated angular frequency of the alternating current power grid, wherein the first active power is an active power of the alternating current power grid, and the first active power reference value is a reference value of the first active power; calculating a difference between the first active power reference value and the first active power to obtain a first difference value; performing low-pass filtering processing on the first difference value to obtain a first filtered value, and calculating a product of the first filtered value and an active branch droop coefficient to obtain a first parameter; calculating a sum of the first parameter and the rated angular frequency to obtain a second parameter; inputting the second parameter into an integrator to obtain the power synchronization phase.

3. The method of claim 1, wherein, obtaining outer loop voltage reference values of the support valve, comprising: obtaining a first reactive power, a first reactive power reference value and a rated voltage amplitude of the alternating current power grid, wherein the first reactive power is a reactive power of the alternating current power grid, and the first reactive power reference value is a reference value of the first reactive power; calculating a difference between the first reactive power reference value and the first reactive power to obtain a second difference value; performing low-pass filtering processing on the second difference value to obtain a second filtered value, and calculating a product of the second filtered value and a reactive branch droop coefficient to obtain a third parameter; Calculate a sum of the third parameter and the rated voltage amplitude to obtain an outer ring voltage reference value of the support valve.

4. The method of claim 1, wherein, Obtain an alternating current dq axis component, including: Obtain a three-phase alternating current of the support valve; Perform coordinate conversion processing on the three-phase alternating current to obtain the alternating current dq axis component, which is a dq axis component of the three-phase alternating current in a two-phase rotating coordinate system.

5. The method of claim 1, wherein, Obtain an inner ring active current reference value of the support valve, including: Obtain a second active power and a second active power reference value, the second active power being an active power of the support valve, and the second active power reference value being a reference value of the second active power; Calculate a difference value between the second active power reference value and the second active power to obtain a fourth difference value; Input the fourth difference value into a proportional-integral controller to obtain the inner ring active current reference value of the support valve.

6. The method of claim 1, wherein, Determine 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 grid synchronization information, including: Calculate a difference value between the inner ring reactive current reference value and a q-axis component of the alternating current in the two-phase rotating coordinate system to obtain a fifth difference value; Input the fifth difference value into a proportional-integral controller to obtain a first voltage modulation signal; Calculate a difference value between the inner ring active current reference value and a d-axis component of the alternating current in the two-phase rotating coordinate system to obtain a sixth difference value; Input the sixth difference value into a proportional-integral controller to obtain a second voltage modulation signal; Perform coordinate inversion processing on the first voltage modulation signal and the second voltage modulation signal to obtain a voltage sinusoidal modulation signal; Perform nearest level approximation modulation processing on the voltage sinusoidal modulation signal to obtain the first control signal.

7. The method of claim 1, wherein, Determine a second control signal according to at least the grid synchronization information, including: Obtain a capacitor voltage of a sub-module of the support valve and a second reactive power, the second reactive power being a reactive power of the support valve; Perform negative feedback adjustment processing on the capacitor voltage of the sub-module of the support valve to obtain a first current modulation signal; Perform negative feedback adjustment processing on the second reactive power to obtain a second current modulation signal; Perform coordinate inversion processing on the first current modulation signal and the second current modulation signal to obtain a current sinusoidal modulation signal; Perform pulse width modulation processing on the current sinusoidal modulation signal to obtain the second control signal.

8. The method of claim 7, wherein, Perform negative feedback adjustment processing on the capacitor voltage to obtain a first current modulation signal, including: Obtain a capacitor voltage reference value of a sub-module of the support valve and calculate a difference value between the capacitor voltage reference value 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 value; Input the seventh difference value into a proportional-integral controller to obtain the first current modulation signal.

9. The method of claim 7, wherein, Perform negative feedback adjustment processing on the second reactive power to obtain a second current modulation signal, including: obtain a second reactive power reference value, the second reactive power reference value being a reference value of the second reactive power, and calculate a difference between the second reactive power reference value and the second reactive power to obtain an eighth difference value; input the eighth difference value into a proportional-integral controller to obtain the second current modulation signal.

10. A network configuration control device of a full-controlled composite converter based on droop control, characterized by, The full-control composite converter includes a port for accessing an alternating current grid, a main valve, and a support valve, and the device includes: an obtaining unit, configured to obtain grid synchronization information, alternating current dq-axis components, an outer-loop voltage reference value of the support valve, and an inner-loop active current reference value of the support valve, wherein the grid synchronization information is a power synchronization phase angle of the alternating current grid, the alternating current dq-axis components include a d-axis component of an alternating current in a two-phase rotating coordinate system and a q-axis component of the alternating current in the two-phase rotating coordinate system, the outer-loop voltage reference value is a reference value of a bus alternating current voltage, and the inner-loop active current reference value is a reference value of the d-axis component of the alternating current in the two-phase rotating coordinate system; a determining unit, configured to determine an inner-loop reactive current reference value according to at least 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 alternating current in the two-phase rotating coordinate system; a first control unit, configured to determine a first control signal according to the inner-loop reactive current reference value, the inner-loop active current reference value, the alternating current dq-axis components, and the grid synchronization information, and control the support valve by using the first control signal to adjust an inner-loop reactive current and an inner-loop active current of the support valve; a second control unit, configured to determine a second control signal according to at least the grid synchronization information, and control the main valve by using the second control signal to adjust an active power of the main valve and a reactive power of the main valve, the determining unit includes a fifth obtaining module and a third input module, wherein the fifth obtaining module is configured to obtain the bus alternating current voltage, and calculate a third difference value by using a difference between the outer-loop voltage reference value of the support valve and the bus alternating current voltage; and the third input module is configured to input the third difference value into a proportional-integral controller to obtain the inner-loop reactive current reference value.

11. A direct current power transmission system, characterized by comprise: a direct current power transmission sending end; a direct current power transmission receiving end, which is electrically connected to the direct current power transmission sending end; a controller, which is in communication connection with the direct current power transmission sending end, wherein the controller is configured to execute the grid construction control method of the full-control composite converter based on droop control according to any one of claims 1 to 9.

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