Transient voltage support method, apparatus, storage medium, and direct current power transmission system

Abstract

The application provides a transient voltage support method, device, storage medium and direct current power transmission system. The method comprises the following steps: calculating an effective value of an alternating current bus voltage to obtain an alternating current voltage effective value calculation value; obtaining a difference value between the alternating current voltage effective value calculation value and an alternating current voltage effective value reference value to obtain an alternating current voltage difference value; determining an alternating current q-axis component reference value of an alternating current in a synchronous rotating coordinate system based on the alternating current voltage difference value; obtaining an alternating current q-axis component calculation value, an alternating current d-axis component reference value and an alternating current d-axis component calculation value, and determining a trigger signal of a support valve according to the alternating current q-axis component reference value, the alternating current q-axis component calculation value, the alternating current d-axis component reference value and the alternating current d-axis component calculation value, and triggering and controlling the support valve by using the trigger signal. The support valve is controlled by using the control based on the alternating current bus voltage, and the stability margin of the alternating current bus voltage is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of high-voltage direct current transmission, in particular to a transient voltage support method and device, a storage medium and a direct current transmission system. BACKGROUND

[0002] At present, the ultra-high voltage direct current transmission technology has become a key bridge connecting long-distance energy bases and load centers. As a core component of the direct current transmission system, the performance of the ultra-high voltage direct current converter directly affects the efficiency and reliability of power transmission. However, with the increasing proportion of new energy in the power grid, the phenomenon of "hollowing" of the power grid gradually appears, resulting in a decrease in the dynamic reactive power regulation capability of the power grid and an increase in the risk of commutation failure of the conventional direct current converter under small disturbances, which seriously threatens the stable operation of the power grid.

[0003] The fully-controlled composite converter connects the three-phase multi-bridge arm structure IGCT straight string valve (i.e. the main valve) and the three-phase full-bridge module (i.e. the support valve) in parallel at the AC side, forming a composite converter with voltage source and current source characteristics. The main valve composed of high-voltage and high-power IGCT devices realizes large-capacity active power transmission, and the voltage source support valve with flexible and controllable output voltage realizes the reactive power support capability of the converter to the power grid.

[0004] At present, the transient voltage support of the support valve of the fully-controlled composite converter usually adopts a reactive power control strategy, and the power grid support capability of the reactive power control strategy is insufficient, with the risk of voltage collapse. SUMMARY

[0005] The main purpose of the present application is to provide a transient voltage support method, device, storage medium and direct current transmission system to solve the problem of insufficient power grid support capability of the reactive power control strategy in the prior art and the risk of voltage collapse.

[0006] In order to achieve the above object, according to a first aspect of the present application, a transient voltage support method is provided, the full-control composite converter comprises a main valve and a support valve, the main valve is an IGCT straight string valve, the support valve comprises a full-bridge module, the transient voltage support method comprises: calculating an effective value of an AC bus voltage to obtain an AC voltage effective value calculation value; obtaining a difference value between the AC voltage effective value calculation value and an AC voltage effective value reference value to obtain an AC voltage difference value; determining an AC current q-axis component reference value of an AC current in a synchronous rotating coordinate system based on the AC voltage difference value; obtaining an AC current q-axis component calculation value, an AC current d-axis component reference value and an AC current d-axis component calculation value of the AC current in the synchronous rotating coordinate system, and determining a trigger signal of the support valve according to the AC current q-axis component reference value, the AC current q-axis component calculation value, the AC current d-axis component reference value and the AC current d-axis component calculation value, and triggering and controlling the support valve by using the trigger signal.

[0007] Optionally, obtaining the AC current d-axis component reference value of the AC current in the synchronous rotating coordinate system comprises: obtaining three-phase bridge arm voltage measurement values of the support valve to obtain a first bridge arm voltage measurement value, a second bridge arm voltage measurement value and a third bridge arm voltage measurement value; calculating an average value of the first bridge arm voltage measurement value, the second bridge arm voltage measurement value and the third bridge arm voltage measurement value to obtain a bridge arm voltage average measurement value; obtaining a bridge arm voltage average reference value, and determining the AC current d-axis component reference value according to the bridge arm voltage average measurement value and the bridge arm voltage average reference value.

[0008] Optionally, obtaining the bridge arm voltage average reference value comprises: obtaining a number of sub-modules of a single-phase bridge arm of the support valve and a use voltage of each sub-module; and determining a product of the use voltage of each sub-module and the number of sub-modules as the bridge arm voltage average reference value.

[0009] Optionally, obtaining the AC current q-axis component calculation value and the AC current d-axis component calculation value of the AC current in the synchronous rotating coordinate system comprises: obtaining a phase-locked phase of the AC bus voltage after phase-locked loop processing; obtaining three-phase currents output by the support valve, the three-phase currents output by the support valve are obtained after being synchronized by the phase-locked phase and subjected to coordinate transformation processing, and the AC current q-axis component calculation value and the AC current d-axis component calculation value in two-phase rotating coordinates are obtained.

[0010] Optionally, the trigger signal of the support valve is determined based on the AC current q-axis component reference value, the AC current q-axis component calculation value, the AC current d-axis component reference value and the AC current d-axis component calculation value, including: performing closed-loop decoupling control on the AC current q-axis component reference value, the AC current q-axis component calculation value, the AC current d-axis component reference value and the AC current d-axis component calculation value to obtain a q-axis component and a d-axis component of an output voltage of the support valve; performing phase synchronization on the q-axis component and the d-axis component of the output voltage by using a phase-locked phase, and generating a voltage modulation wave in a three-phase static coordinate through coordinate transformation; performing nearest level approximation modulation processing on the voltage modulation wave in the three-phase static coordinate to obtain the trigger signal of the support valve.

[0011] Optionally, the effective value of the AC bus voltage is calculated to obtain an AC voltage effective value calculation value, including: performing coordinate transformation on the AC bus voltage to obtain a q-axis component and a d-axis component of the AC bus voltage; obtaining a square value of the q-axis component of the AC bus voltage to obtain a first square value; obtaining a square value of the d-axis component of the AC bus voltage to obtain a second square value; integrating the first square value and the second square value in a time domain to obtain an integral value, and calculating a ratio of the integral value and integral time to obtain an average value of voltage square; performing square root processing on the average value of voltage square to obtain the AC voltage effective value calculation value.

[0012] Optionally, the AC current q-axis component reference value in the synchronous rotating coordinate system is determined based on the AC voltage difference value, including: obtaining a PI control model, parameters in the PI control model including a proportional coefficient, an integral coefficient and a time parameter; and applying the PI control model to process the AC voltage difference value to obtain the AC current q-axis component reference value.

[0013] According to a second aspect of the present application, a transient voltage support device is provided, which is suitable for a full-controlled composite converter, the full-controlled composite converter comprising a main valve and a support valve, the main valve being an IGCT straight string valve, and the support valve comprising full-bridge modules, the transient voltage support device comprising: a calculation unit configured to calculate an effective value of an AC bus voltage to obtain an AC voltage effective value calculation value; an obtaining unit configured to obtain a difference between the AC voltage effective value calculation value and an AC voltage effective value reference value to obtain an AC voltage difference value; a determination unit configured to determine an AC current q-axis component reference value of an AC current in a synchronous rotating coordinate system based on the AC voltage difference value; and an obtaining and determining unit configured to obtain an AC current q-axis component calculation value and an AC current d-axis component calculation value of the AC current in the synchronous rotating coordinate system, and to determine a trigger signal of the support valve according to the AC current q-axis component reference value, the AC current q-axis component calculation value, the AC current d-axis component reference value and the AC current d-axis component calculation value, and to trigger control the support valve by using the trigger signal.

[0014] According to a third aspect of the present application, a computer readable storage medium is provided, which comprises a stored program, wherein the computer readable storage medium controls a device where the computer readable storage medium is located to execute any one of the transient voltage support methods when the program is running.

[0015] According to a fourth aspect of the present application, a DC power transmission system is provided, which comprises: a sending end and a receiving end, the sending end comprising a main valve and a support valve, the receiving end comprising a main valve and a support valve, and a controller connected with the sending end and the receiving end, and configured to execute any one of the transient voltage support methods to support the support valve of the sending end or the support valve of the receiving end in transient voltage.

[0016] The technical advantages of this application include: dynamically adjusting the reference value of the AC current q-axis component based on real-time AC voltage difference; and then determining the trigger signal of the support valve based on the AC current q-axis component reference value, the calculated AC current q-axis component value, the AC current d-axis component reference value, and the calculated AC current d-axis component value, thereby achieving reactive power control of the support valve. This ensures that the reactive power output of the converter can accurately match the actual needs of the power grid, enhancing the support capability for transient voltage. Especially in weak power grids or fault scenarios, this precise control greatly enhances the stability of the power grid voltage and reduces the risk of voltage collapse. By using reactive power control based on AC bus voltage to control the support valve, compared to the solution using a reactive power controller, the stability margin of the AC bus voltage can be improved, reducing the impact of faults on power transmission. This is because the reactive power controller solution requires determining the power based on the AC bus voltage and AC bus current before subsequent reactive power control, rather than the direct control based on the AC bus voltage in this solution. This solves the technical problem of insufficient power grid support capability and the risk of voltage collapse in existing reactive power control strategies. Attached Figure Description

[0017] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings:

[0018] Figure 1 A schematic flowchart of a transient voltage support method according to an embodiment of this application is shown;

[0019] Figure 2 A schematic diagram of the transient voltage support method according to an embodiment of this application is shown, which is applicable to the transient voltage support strategy at the receiving end.

[0020] Figure 3 A schematic diagram of the transient voltage support method according to an embodiment of this application is shown, which is applicable to the transient voltage support strategy at the sending end.

[0021] Figure 4 A schematic diagram showing the connection relationship between a specific main valve and a support valve according to an embodiment of this application is shown;

[0022] Figure 5 A comparison diagram of transient characteristics of the F3C converter under different control strategies according to embodiments of this application is shown;

[0023] Figure 6 A schematic diagram of a transient voltage support device according to an embodiment of this application is shown. Detailed Implementation

[0024] It should be noted that the following detailed description is intended to provide further description of the present application. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

[0025] It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments in accordance with the present application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and / or "comprising," when used in this specification, specify the presence of stated features, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, steps, operations, elements, components, and / or groups thereof.

[0026] It will be understood that when an element such as a layer, film, region, or substrate is referred to as being "on" another element, it can be directly on the other element or intervening elements can also be present. In addition, it will be understood that when an element is referred to as being "connected" to another element, it can be directly connected to the other element, or electrically connected to the other element via a third element.

[0027] In the description of the embodiments of the present application, the technical terms "first", "second", and the like are used only to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the technical features indicated. It can be understood that "at least one" means one or more, and "multiple" means two or more. "At least part of the element" means part or all of the element.

[0028] It can be understood that "connection" in the following embodiments means that the circuits, modules, units, etc. connected to each other have the transmission of electrical signals or data, and should be understood as "electrical connection", "communication connection", etc.

[0029] In the description of the embodiments of the present application, the term "and / or" is only used to describe the association relationship of the associated objects, which means that there can be three relationships, for example, A and / or B, which means that there are three cases of A, A and B, and B. In addition, the character " / " in this paper generally represents that the front and rear associated objects are a "or" relationship.

[0030] The terms used in the description of various embodiments herein are only used to describe specific embodiments, and are not intended to be limiting. As used in the description of various embodiments and the appended claims, "part" is also intended to include the plural form, unless the context clearly indicates otherwise.

[0031] The embodiments of the present application will be described in detail below with reference to the drawings. However, those skilled in the art can understand that, in the embodiments of the present application, many technical details are presented in order to enable the reader to better understand the present application. However, the technical solutions claimed by the present application can be implemented even without these technical details and various changes and modifications based on the following embodiments.

[0032] As introduced in the background, the transient voltage support of the support valve of the full-control composite converter is currently often controlled by reactive power control strategy. The grid support capability of the reactive power control strategy is insufficient, and there is a risk of voltage collapse. In order to solve the problem of insufficient grid support capability of the reactive power control strategy and the risk of voltage collapse, the present application proposes a transient voltage support method, device, storage medium and DC power transmission system.

[0033] In the present embodiment, a transient voltage support method 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 the logical order is shown in the flowchart, in some cases, the steps shown or described can be executed in an order different from that shown here.

[0034] Figure 1 is a flowchart of the transient voltage support method according to the embodiments of the present application. The method is suitable for a full-control composite converter, which includes a main valve and a support valve. The main valve is an IGCT straight string valve, and the support valve includes a full-bridge module. The transient voltage support method in the present solution is suitable for both the sending end and the receiving end of a DC power transmission system.

[0035] The transient voltage support method includes:

[0036] In step S101, the effective value of the AC bus voltage is calculated to obtain an AC voltage effective value calculation value;

[0037] Referring to Figure 2 , the AC bus voltage u g_abc is input to an AC voltage effective value calculation unit to obtain an AC voltage effective value calculation value U acrms ;

[0038] When the transient voltage support method is applied to the sending end of a DC power transmission system, the AC bus voltage is the AC bus voltage of the sending end. When the transient voltage support method is applied to the receiving end of a DC power transmission system, the AC bus voltage is the AC bus voltage of the receiving end.

[0039] Specifically, the AC bus voltage can be directly measured by a voltage transformer or a voltage sensor installed on the AC bus. Of course, other ways of obtaining the AC bus voltage can also be chosen.

[0040] Specifically, the AC voltage effective value calculation value can be obtained after processing the obtained AC bus voltage.

[0041] Step S102, obtaining the difference between the AC voltage effective value calculation value and the AC voltage effective value reference value to obtain the AC voltage difference value;

[0042] Referring to Figure 2 , the difference between the AC voltage effective value calculation value U acrms and the AC voltage effective value reference value U acrms is obtained to obtain the AC voltage difference value.

[0043] The AC voltage effective value calculation value is calculated by step S101;

[0044] The AC voltage effective value reference value is usually set according to the overall design requirements of the power system, such as the rated voltage of the power grid. If the rated voltage of the system is 400kV, the AC voltage effective value reference value may be set as the effective value form of 400kV. That is, the AC voltage effective value reference value is 1p.u.

[0045] In actual operation, the AC voltage effective value reference value may also be fine-tuned according to specific operating parameters, such as the load condition of the power grid, weather conditions or other external factors. Such setting is usually based on the purpose of maintaining grid stability and optimizing system performance.

[0046] To ensure that the system can still operate stably under abnormal conditions, in some cases, the AC voltage effective value reference value may be set at a value slightly higher than the rated voltage of the power grid to provide additional safety margin. For example, even if the rated voltage of the system is 400kV, the AC voltage effective value reference value may be set to 410kV so that the system can still remain stable when the voltage fluctuates slightly.

[0047] Step S103, determining the AC current q-axis component reference value of the AC current in the synchronous rotating coordinate system based on the AC voltage difference value;

[0048] Referring to Figure 2 , the AC current q-axis component reference value is represented as i cq .

[0049] In the synchronous rotating coordinate system, the alternating current can be decomposed into d-axis component and q-axis component. The d-axis is consistent with the direction of the positive sequence voltage of the power grid, and the q-axis is perpendicular to the d-axis. In this coordinate system, the q-axis current component is directly related to the reactive power provided by the converter to the power grid. Therefore, by adjusting the q-axis current component reference value, the reactive power output of the converter can be finely controlled. That is, through the control based on the alternating voltage difference value, the converter can quickly adjust its reactive power output, reduce the voltage deviation, and thus maintain the stability of the alternating bus voltage during power grid failure or voltage fluctuation. Accurate control of the q-axis current component in the synchronous rotating coordinate system can achieve fine management of reactive power and improve the operation efficiency and reliability of the power system.

[0050] Specifically, PI control is performed on the alternating voltage difference value to determine the q-axis current component reference value.

[0051] In the embodiments of the present application, to determine the q-axis current component reference value, a fuzzy control strategy can be introduced to construct a fuzzy control relationship between the alternating voltage difference value and the q-axis current component reference value, and to provide more flexible and intelligent determination of the q-axis current component reference value. The parameters in the fuzzy control strategy are set based on the system structure of the DC power transmission system, and in the present scheme, they are set according to the specific structure of the fully controlled composite converter. The parameters in the fuzzy control strategy include membership function parameters, rule base parameters, and defuzzification and scaling factor parameters.

[0052] In addition, PI control and fuzzy control strategy can be combined to determine the q-axis current component reference value. Specifically, the two accurate quantities, the alternating voltage difference value and its rate of change, are first fuzzified, the fuzzy subsets such as "large", "medium" and "small" are divided, and the triangular or trapezoidal membership degree functions are defined. Then, a fuzzy rule base is constructed according to the operation experience of the power system (e.g., when the voltage difference value is large, the q-axis current needs to be quickly adjusted to stabilize the voltage), the fuzzy adjustment amount of the PI controller proportional coefficient (Kp) and integral coefficient (Ki) is generated through the Mamdani or Sugeno reasoning method, and finally the precise parameters are converted through the defuzzification method such as the gravity method to realize the real-time dynamic optimization of the PI parameters. The optimized PI controller calculates and outputs the q-axis current component reference value according to the voltage difference value and the optimized parameters, which not only retains the advantages of PI control such as no static error and high steady-state accuracy, but also improves the dynamic response speed of the system to disturbances with the help of fuzzy control.

[0053] Step S104, obtaining the alternating current q-axis component calculation value of the alternating current in the synchronous rotating coordinate system, the alternating current d-axis component reference value and the alternating current d-axis component calculation value, and determining the trigger signal of the support valve according to the alternating current q-axis component reference value, the alternating current q-axis component calculation value, the alternating current d-axis component reference value and the alternating current d-axis component calculation value, and triggering the support valve using the trigger signal.

[0054] Referring to Figure 2 , the trigger signal S of the support valve is determined according to the alternating current q-axis component reference value i cq *,the alternating current q-axis component calculation value i cq ,the alternating current d-axis component reference value i cd * and the alternating current d-axis component calculation value i cd . a1-n b1-n c1-n .

[0055] In the synchronous rotating coordinate system, the q-axis and d-axis current components represent the independent control freedom degrees of reactive and active power respectively. By independently controlling these two components, the decoupling of active and reactive power is realized, thereby improving the response speed and accuracy of the control system to dynamic changes in the power grid.

[0056] By dynamically adjusting the q-axis current component reference value in real time, the reactive power output by the converter can be accurately matched to the actual demand of the power grid, especially in weak grid or fault scenarios. This precise control greatly enhances the stability of the grid voltage and reduces the risk of voltage collapse.

[0057] By considering both the reference value and the calculation value of the d-axis component, the transmission of active power can also be optimized, ensuring that the active power transmission of the converter is not significantly disturbed while providing reactive power support, maintaining the efficiency and economy of system operation.

[0058] During transient faults (such as bus voltage drop), this control strategy increases the system's response speed to faults by quickly adjusting the q-axis current component reference value, reducing the impact of faults on the normal operation of the converter and enhancing the fault resistance of the converter in weak grid conditions.

[0059] This control strategy realizes self-regulation of active and reactive power within the F3C converter, reducing dependence on external control equipment (such as synchronous compensator SVG and capacitor bank), simplifying the complexity of power system control, and reducing the overall cost and maintenance difficulty of the control system.

[0060] In combination with the analysis in the foregoing, the transient voltage support method including the steps S101, S102, S103 and S104 in the present application, by means of the real-time AC voltage difference, dynamically adjusts the AC current q-axis current component reference value, and then determines the trigger signal of the support valve according to the AC current q-axis component reference value, the AC current q-axis component calculation value, the AC current d-axis component reference value and the AC current d-axis component calculation value, to realize the control of the support valve to achieve reactive power control, ensuring that the reactive power output by the converter can accurately match the actual demand of the power grid, and enhancing the support capability of the transient voltage. Especially in the weak grid or fault scenario, such accurate control greatly enhances the stability of the grid voltage, reducing the risk of voltage collapse. By using the control based on the AC bus voltage to control the support valve reactive power control, compared with the scheme using the reactive power controller, the stability margin of the AC bus voltage can be improved, and the impact of the fault on power transmission can be reduced. The reason is that the scheme using the reactive power controller needs to determine the power according to the AC bus voltage and the AC bus current first, and then perform subsequent reactive control, instead of the direct control based on the AC bus voltage in the present scheme. The technical problem of insufficient power grid support capability of the existing reactive power control strategy and the risk of voltage collapse is solved.

[0061] In a specific implementation, the AC current d-axis component reference value of the AC current in the synchronous rotating coordinate system is obtained, including:

[0062] The three-phase bridge arm voltage measurement values of the support valve are obtained, to obtain a first bridge arm voltage measurement value, a second bridge arm voltage measurement value and a third bridge arm voltage measurement value;

[0063] Specifically, referring to Figure 2 , the first bridge arm voltage measurement value u dca , the second bridge arm voltage measurement value u dcb and the third bridge arm voltage measurement value u dcc refer to the sum of the voltages of all sub-modules corresponding to the phase, each phase is formed by cascading a plurality of sub-modules SM, the sub-module is a full-bridge structure, each bridge arm includes parallel IGBT and diode, and further includes a capacitor connected in parallel across the full-bridge structure.

[0064] The average value of the first bridge arm voltage measurement value, the second bridge arm voltage measurement value and the third bridge arm voltage measurement value is calculated to obtain a bridge arm voltage average measurement value;

[0065] The bridge arm voltage average reference value is obtained, and the AC current d-axis component reference value is determined according to the bridge arm voltage average measurement value and the bridge arm voltage average reference value.

[0066] Referring to Figure 2 , the AC current d-axis component reference value is determined according to the bridge arm voltage average measurement value U d_ave and the bridge arm voltage average reference value U d_ave* determine the alternating current d-axis component reference value i cd Specifically, the difference between the bridge arm voltage average measurement value and the bridge arm voltage average reference value is subjected to PI operation to obtain the alternating current d-axis component reference value. Specifically,

[0067] ;

[0068] is a proportional coefficient, is an integral coefficient, is an integral time.

[0069] Referring to Figure 2 The sub-module capacitor voltage balancing control is the key to ensure the output characteristics of the support valve. Only accurate control of the voltage of each sub-module can ensure that the stepped voltage waveform of the output has good harmonic characteristics and presents better alternating sinusoidal characteristics. In addition, from the perspective of service life, the more accurate the sub-module capacitor voltage control, the less likely the capacitor voltage will exceed the limit due to overcharging of the sub-module, that is, it is beneficial to prolong the service life of the equipment.

[0070] By calculating the bridge arm voltage average and comparing it with the reference value, the bridge arm voltage can be accurately controlled to ensure stable operation of the converter under various operating conditions, especially in the case of power grid failure or rapid load change. Compared with controlling each sub-module separately, the bridge arm voltage average control greatly simplifies the complexity of the control system and reduces the control cost. Accurate control of the bridge arm voltage average is beneficial to improve the performance indicators of the entire converter system, such as power factor, harmonic content, and energy conversion efficiency.

[0071] The d-axis component controls the transmission of active power. By comparing the bridge arm voltage average with the reference value and timely adjusting the alternating current d-axis component reference value, stable and efficient transmission of active power can be ensured. Specifically, the alternating current d-axis component controls the active power of the support valve, which is essentially the constant voltage of the sub-module SM. Since an increase in active power will directly cause the capacitor voltage of the sub-module SM to rise, and vice versa, when the capacitor voltage of the sub-module SM is controlled to be stable, the support valve will not participate in active power regulation.

[0072] Specifically, the active and reactive power coordination between the converter and the power grid is achieved by relying on the trigger angle control of the main valve and the q-axis component control of the support valve. By adjusting the trigger angle, the active power control of the converter is achieved, and by adjusting the q-axis component, the reactive power control of the converter is achieved. The d-axis component control of the sub-module SM constant voltage is the basis for achieving the active and reactive power coordination control of the fully controlled composite converter. In addition, since the fully controlled composite converter can directly participate in the regulation of the alternating current bus voltage under the control of the alternating current bus voltage, the operating efficiency and stability of the power system are improved.

[0073] Therefore, the above technical solution can significantly improve the stability and fault recovery capability of the power system under weak grid conditions, and ensure the continuity of power transmission and the adaptability of the system to grid changes.

[0074] In addition, referring to Figure 2 The reason why the sub-module capacitor voltage balancing control does not need to control each sub-module SM separately is that the nearest level approximation modulation strategy is adopted, which has the function of capacitor voltage sorting and can discharge the capacitor with high voltage first, so that the bridge arm voltage balancing can directly meet the voltage balancing of the sub-module.

[0075] Specifically, the bridge arm voltage average reference value is obtained, including: obtaining the number of sub-modules of a single-phase bridge arm of a support valve and the use voltage of each sub-module; and determining the product of the use voltage of each sub-module and the number of sub-modules as the bridge arm voltage average reference value.

[0076] For example, for a 4.5kV IGBT, considering the use voltage after redundancy is 2.4kV, the number of sub-modules of each phase bridge arm is 65, and the use voltage is 2.4kV, then the bridge arm voltage average reference value is 65*2.4kV=156kV.

[0077] The determination of the bridge arm voltage average reference value by calculating the product of the number of sub-modules in the single-phase bridge arm of the support valve and the use voltage of the sub-module has the following technical advantages:

[0078] Multiplying the use voltage of the sub-module by the number of sub-modules ensures that the bridge arm voltage average reference value is accurately matched with the voltage level designed by the system, avoiding energy waste and device damage risk caused by voltage mismatch.

[0079] The reference value obtained by this calculation guides the control system, which can realize the balancing control of the capacitor voltage of the sub-module, prevent excessive stress on the sub-module caused by voltage deviation, and prolong the service life of the device.

[0080] This method directly calculates based on the basic parameters of the sub-module, avoids complex model prediction or real-time detection algorithm, simplifies the control logic, and reduces the calculation burden and device cost.

[0081] Combined with the adjustment of the AC current q-axis component reference value in step S103, the method can support the dynamic adjustment capability of the system, adjust the bridge arm voltage average reference value according to the real-time state and demand of the grid, and optimize power transmission.

[0082] In the embodiment of the application, the AC current q-axis component calculation value and the AC current d-axis component calculation value of the AC current in the synchronous rotating coordinate system are obtained, including:

[0083] The AC bus voltage is processed by a phase-locked loop to obtain a phase-locked phase;

[0084] The three-phase current output by the support valve is obtained, and after being synchronized by a phase-locked phase and processed by a coordinate transformation, the AC current q-axis component calculation value and the AC current d-axis component calculation value in the two-phase rotating coordinate system are obtained.

[0085] Referring to Figure 2 , the AC bus voltage u g_abc is processed by a phase-locked loop PLL to obtain a phase-locked phase , the three-phase current i c_abc output by the support valve is processed by a phase-locked phase synchronization and coordinate transformation to obtain the AC current q-axis component calculation value i cq and the AC current d-axis component calculation value i cd .

[0086] The use of a phase-locked loop (PLL) provides an accurate synchronization phase, enabling the converter to operate in synchronization with the power grid, which is crucial for power conversion and control, especially in complex and rapidly changing grid environments.

[0087] Synchronization of the synchronization phase and the fast coordinate transformation process ensures the quick response of the control system to grid changes, which is a key performance indicator for power electronic devices under dynamic grid conditions.

[0088] The introduction of the two-phase rotating coordinate system realizes decoupled control of the d-axis (active) and q-axis (reactive), enabling the converter to control active power while independently controlling reactive power output, which is important for maintaining grid voltage stability and improving power transmission efficiency.

[0089] The coordinate transformation process converts three-phase current into components in the two-phase rotating coordinate system, simplifying the complexity of the control strategy and making the design and implementation of the control system more efficient and economical.

[0090] Control based on coordinate transformation helps to improve the operating stability of power electronic devices under unstable or fault conditions of the power grid. By accurately controlling the q-axis current component calculation value, voltage fluctuations can be quickly suppressed, reducing the impact of faults on power transmission. The accurate control of the q-axis component is directly related to the voltage support capability, which can optimize the reactive power output of the converter, thereby providing more effective voltage support under weak grid conditions and enhancing the overall stability and reliability of the system.

[0091] In a specific embodiment, the trigger signal of the support valve is determined according to the AC current q-axis component reference value, the AC current q-axis component calculation value, the AC current d-axis component reference value, and the AC current d-axis component calculation value, including:

[0092] The AC current q-axis component reference value, the AC current q-axis component calculated value, the AC current d-axis component reference value, and the AC current d-axis component calculated value are closed-loop decoupling controlled to obtain the q-axis component and the d-axis component of the output voltage of the support valve; see Figure 2 The AC current q-axis component reference value i cq The AC current q-axis component calculated value i cq The AC current d-axis component reference value i cd The AC current d-axis component calculated value i cd The AC current q-axis component reference value i cq The AC current d-axis component reference value i cd .

[0093] The q-axis component and the d-axis component of the output voltage are phase-synchronized using a phase-locked phase, and a coordinate transformation is performed to generate a voltage modulation wave in a three-phase stationary coordinate; see Figure 2 The q-axis component and the d-axis component of the output voltage are phase-synchronized using a phase-locked phase, and a coordinate transformation is performed to generate a voltage modulation wave in a three-phase stationary coordinate; see The q-axis component and the d-axis component of the output voltage are phase-synchronized using a phase-locked phase, and a coordinate transformation is performed to generate a voltage modulation wave in a three-phase stationary coordinate; see ca、 cb、 cc .

[0094] The voltage modulation wave in the three-phase stationary coordinate is subjected to nearest level approximation modulation processing to obtain the trigger signal of the support valve. The nearest level approximation modulation approximates the expected voltage waveform by selecting the nearest level, reduces the switching frequency of the switching device, effectively reduces the switching loss, and improves the efficiency and durability of the power electronic equipment.

[0095] By decomposing the AC current into q-axis and d-axis components, independent closed-loop control is adopted, not only achieving the decoupling of active and reactive currents, but also improving the ability to independently adjust the two, making the response speed faster and the control more accurate.

[0096] Closed-loop decoupling control allows the system to accurately track the q-axis and d-axis current components, maintaining stable output of the current components even in the case of grid condition changes or load fluctuations, improving the efficiency and quality of power transmission.

[0097] Synchronizing the q-axis and d-axis components using a phase-locked phase ensures that the output voltage modulation wave is in phase with the grid voltage, optimizing the power conversion process and reducing energy loss during conversion.

[0098] By coordinate transformation, the q-axis and d-axis components of the output voltage are converted into modulation waves in a three-phase stationary coordinate, enabling the inverter to directly control three-phase AC voltage and improving the flexibility and adaptability of control.​​

[0099] The closed-loop decoupling control ensures the stability and accuracy of the support valve output voltage, which plays an irreplaceable role in maintaining grid voltage stability, especially during fault recovery.

[0100] By precisely controlling the q-axis current component, the system can quickly inject or absorb reactive power when the grid fluctuates, effectively dealing with grid faults and reducing the impact of faults on the power system.

[0101] This part of the technical solution optimizes the power conversion process through closed-loop decoupling control and voltage modulation wave generation, improves the system's ability to respond to grid changes, reduces the complexity of the control system, and enhances the stability and intelligence level of the system.

[0102] In some specific embodiments, the effective value of the alternating current bus voltage is calculated to obtain an alternating current voltage effective value calculation value, including:

[0103] The alternating current bus voltage is subjected to coordinate transformation to obtain the q-axis component and the d-axis component of the alternating current bus voltage; the square value of the q-axis component of the alternating current bus voltage is obtained to obtain a first square value; the square value of the d-axis component of the alternating current bus voltage is obtained to obtain a second square value; the first square value and the second square value are integrated in the time domain to obtain an integral value, and the ratio of the integral value and the integral time is calculated to obtain the average value of the square of the voltage; the average value of the square of the voltage is subjected to square root processing to obtain the alternating current voltage effective value calculation value.

[0104] By converting the alternating current bus voltage to the rotating dq coordinate system, the effective value of the voltage can be more easily calculated. This method directly calculates more accurately because the voltage components in the dq coordinate system can better reflect transient and steady-state voltage information. The time-domain integration method of the square value can eliminate the influence of negative values in the alternating current voltage, ensuring the accuracy of the effective value calculation.

[0105] To determine the reference value of the alternating current q-axis component, the reference value of the alternating current q-axis component in the synchronous rotating coordinate system is determined based on the alternating current voltage difference, including: obtaining a PI control model, the parameters of the PI control model including a proportional coefficient, an integral coefficient and a time parameter; applying the PI control model to process the alternating current voltage difference to obtain the reference value of the alternating current q-axis component. Specifically,

[0106] ;

[0107] The reference value of the alternating current q-axis component is The proportional coefficient is The integral coefficient is The integral time is The alternating current voltage effective value reference value is Uacrms The AC voltage effective value calculation value is calculated.

[0108] PI control combines proportional (P) and integral (I) control effects, which can provide fast response and long-term stable control when the system deviates, ensuring accurate setting of the AC current q-axis component reference value. The integral effect can automatically eliminate steady-state error, and even in the presence of external disturbances or system parameter changes, the control output can be adjusted by integrating the accumulated error to maintain the stability of the AC voltage. PI control can improve the dynamic performance of the system, quickly adjust the q-axis current component by quickly responding to grid voltage changes, to maintain the stable operation of the converter, especially when dealing with grid faults or voltage fluctuations.

[0109] In order to enable those skilled in the art to more clearly understand the technical solutions of the present application, the implementation process of the transient voltage support method of the present application will be described in detail below in conjunction with specific embodiments.

[0110] The present embodiment relates to a specific transient voltage support method applied to the receiving end, the implementation principle is shown in Figure 2 , which comprises:

[0111] The determination of the AC voltage effective value calculation value U acrms is realized by the AC voltage effective value calculation unit;

[0112] The PI control of the AC voltage effective value calculation value U acrms and the AC voltage effective value reference value U acrms * based on the AC bus voltage control obtains the AC current q-axis component reference value i cq *;

[0113] The phase-locked phase obtained after the AC bus voltage is processed by the phase-locked loop, and the three-phase current output by the support valve is synchronized and processed by the coordinate transformation after the phase-locked phase, and the AC current q-axis component calculation value i cq and the AC current d-axis component calculation value i cd in the two-phase rotating coordinate are obtained;

[0114] The determination of the AC current d-axis component reference value i cd * is realized by the application of the sub-module capacitor voltage equalization control, wherein the input parameters of the module capacitor voltage equalization control are the bridge arm voltage average measurement value U d_ave and the bridge arm voltage average reference value U d_ave *;

[0115] Then, according to the AC current q-axis component reference value i cq *, the AC current q-axis component calculation value i cq , and the AC current d-axis component reference value i cd* and the calculated value of the d-axis component of the alternating current i cd ;

[0116] Determine the q-axis component u of the output voltage of the support valve. cq * and d-axis components u cd *, phase-locked phase The q-axis and d-axis components of the output voltage are synchronized in phase and then transformed to generate a voltage modulation wave u in three-phase stationary coordinates. ca、 u cb、 u cc ;

[0117] Subsequent application of Nearest Level Approximation Modulation (NLM) to u ca、 u cb、 u cc The processing yields the trigger signal S of the support valve. a1-n S b1-n S c1-n .

[0118] See Figure 2 It also includes using the DC voltage control of the main valve to determine the trigger angle of the main valve, specifically by performing PI calculations using the measured DC bus voltage value Udc and the reference DC bus voltage value Udc*. , The phase-locked loop is used to process uc_abc to obtain reuse right Phase synchronization is performed to obtain the main valve trigger angle.

[0119] This embodiment relates to another specific transient voltage support method applied to the sending end; the implementation principle is described in [link to implementation details]. Figure 3 As shown, the implementation principle of the transient voltage support method applied to the sending end is the same as that applied to the sending end, the difference being the location for obtaining the AC bus voltage; that is, the transient voltage support method applied to the sending end also uses AC voltage RMS calculation, submodule capacitor voltage equalization control, AC bus voltage-based control, etc. Figure 3 The diagram only shows a part of the implementation principle;

[0120] Another difference is that the control of the main valve at the feed end is based on DC current control, see [link to relevant documentation]. Figure 3 DC bus current measurement value Idc and DC bus current reference value Idc * Specifically, the DC bus current measurement value U is used. dc and Idc PI calculation is performed on the DC bus current reference value Idc* to obtain , , using the phase-locked loop to process the uc_abc to obtain , and using the phase-locked loop to process the uc_abc to obtain the phase synchronization of to obtain the main valve trigger angle.

[0121] The specific connection relationship of the main valve and the support valve can be referred to Figure 4 ;

[0122] The transient characteristics of the F3C converter under different control strategies are compared in Figure 5 :

[0123] Among them, under the single-phase 0.01H inductance grounding fault condition, based on the AC bus voltage control strategy, the bus voltage drops to 153.6kV, and under the constant reactive power control strategy, the bus voltage drops to 146.5kV.

[0124] Among them, under the three-phase 0.01H inductance grounding fault condition, based on the AC bus voltage control strategy, the bus voltage drops to 109.1kV, and under the constant reactive power control strategy, the bus voltage drops to 100.0kV.

[0125] Among them, under the single-phase 0.01H inductance grounding fault condition, based on the AC bus voltage control strategy, the maximum reactive power demand is about 51.4Mvar, and under the constant reactive power control strategy, the maximum reactive power demand is about 149.8Mvar;

[0126] Among them, under the three-phase 0.01H inductance grounding fault condition, based on the AC bus voltage control strategy, the maximum reactive power demand is about 400.3Mvar, and under the constant reactive power control strategy, the maximum reactive power demand is about 705.1Mvar.

[0127] The embodiment of the application also provides a transient voltage support device. It should be noted that the transient voltage support device of the embodiment of the application can be used to execute the transient voltage support method provided by the embodiment of the application. The device is used to realize the above-mentioned embodiments and preferred embodiments, and the description is not repeated. As used below, the term "module" can be a combination of software and / or hardware that implements a predetermined function. Although the device described in the following embodiments is preferably implemented in software, hardware, or a combination of software and hardware can also be implemented and conceived.

[0128] The transient voltage support device provided by the embodiment of the application is introduced below.

[0129] Figure 6is a schematic diagram of a transient voltage support device according to an embodiment of the present application. The transient voltage support device is suitable for a fully controlled composite converter, which includes a main valve and a support valve, the main valve is an IGCT straight string valve, and the support valve includes full-bridge modules, as shown in Figure 6 The device includes:

[0130] A calculation unit 61 is configured to calculate an effective value of an AC bus voltage to obtain an AC voltage effective value calculation value.

[0131] An acquisition unit 62 is configured to acquire a difference between the AC voltage effective value calculation value and an AC voltage effective value reference value to obtain an AC voltage difference value.

[0132] A determination unit 63 is configured to determine an AC current q-axis component reference value of an AC current in a synchronous rotating coordinate system based on the AC voltage difference value.

[0133] An acquisition and determination unit 64 is configured to acquire an AC current q-axis component calculation value of the AC current in the synchronous rotating coordinate system, an AC current d-axis component reference value, and an AC current d-axis component calculation value, and determine a trigger signal of the support valve according to the AC current q-axis component reference value, the AC current q-axis component calculation value, the AC current d-axis component reference value, and the AC current d-axis component calculation value, and perform trigger control on the support valve by using the trigger signal.

[0134] In the present application, the calculation unit, the acquisition unit, the determination unit, and the acquisition and determination unit are used to dynamically adjust the AC current q-axis current component reference value based on the real-time AC voltage difference value, and then determine the trigger signal of the support valve according to the AC current q-axis component reference value, the AC current q-axis component calculation value, the AC current d-axis component reference value, and the AC current d-axis component calculation value, so as to control the support valve to realize reactive power control, thereby ensuring that the reactive power output by the converter can accurately match the actual demand of the power grid and enhancing the support capability of the transient voltage. Especially in a weak power grid or a fault scenario, such accurate control greatly enhances the stability of the power grid voltage and reduces the risk of voltage collapse. By using the control based on the AC bus voltage to perform reactive power control on the support valve, compared with the scheme using a reactive power controller, the stability margin of the AC bus voltage can be improved and the impact of the fault on power transmission can be reduced. The reason is that the scheme using the reactive power controller needs to determine the power based on the AC bus voltage and the AC bus current first, and then perform subsequent reactive control, instead of the direct control based on the AC bus voltage in the present application. The technical problem of insufficient power grid support capability of the existing reactive power control strategy and the risk of voltage collapse is solved.

[0135] In an optional solution, the acquisition and determination unit comprises a first acquisition module, a calculation module and a determination module. The first acquisition module is configured to acquire the three-phase bridge arm voltage measurement values of the support valve to obtain a first bridge arm voltage measurement value, a second bridge arm voltage measurement value and a third bridge arm voltage measurement value. The calculation module is configured to calculate the average value of the first bridge arm voltage measurement value, the second bridge arm voltage measurement value and the third bridge arm voltage measurement value to obtain a bridge arm voltage average value measurement value. The acquisition and determination module is configured to acquire a bridge arm voltage average reference value, and determine the AC current d-axis component reference value according to the bridge arm voltage average measurement value and the bridge arm voltage average reference value.

[0136] In an optional solution, the acquisition and determination module is specifically configured to acquire the number of sub-modules of the single-phase bridge arm of the support valve and the use voltages of the sub-modules, and determine the product of the use voltages of the sub-modules and the number of the sub-modules as the bridge arm voltage average reference value.

[0137] In an optional solution, the acquisition and determination unit comprises a first processing module and a second processing module. The first processing module is configured to obtain a phase-locked phase after the AC bus voltage is processed by a phase-locked loop. The second processing module is configured to acquire the three-phase current output by the support valve, and obtain the AC current q-axis component calculation value and the AC current d-axis component calculation value in the two-phase rotating coordinate after the three-phase current output by the support valve is synchronized by the phase-locked phase and processed by coordinate transformation.

[0138] In the embodiment of the application, the acquisition and determination unit comprises a decoupling module, a synchronization module and a modulation module. The decoupling module is configured to perform closed-loop decoupling control on the AC current q-axis component reference value, the AC current q-axis component calculation value, the AC current d-axis component reference value and the AC current d-axis component calculation value to obtain the q-axis component and the d-axis component of the output voltage of the support valve. The synchronization module is configured to perform phase synchronization on the q-axis component and the d-axis component of the output voltage by using the phase-locked phase, and generate a voltage modulation wave in the three-phase stationary coordinate after coordinate transformation. The modulation module is configured to perform nearest level approximation modulation processing on the voltage modulation wave in the three-phase stationary coordinate to obtain the trigger signal of the support valve.

[0139] In the embodiment of the application, the calculation unit comprises a transformation module, a second acquisition module, a third acquisition module, an integration module and a square root module. The transformation module is configured to perform coordinate transformation on the AC bus voltage to obtain the q-axis component and the d-axis component of the AC bus voltage. The second acquisition module is configured to acquire the square value of the q-axis component of the AC bus voltage to obtain a first square value. The third acquisition module is configured to acquire the square value of the d-axis component of the AC bus voltage to obtain a second square value. The integration module is configured to integrate the first square value and the second square value in the time domain to obtain an integration value, and calculate the ratio of the integration value and the integration time to obtain the average value of the voltage square. The square root module is configured to perform square root processing on the average value of the voltage square to obtain the AC voltage effective value calculation value.

[0140] In the embodiment of the present application, the determining unit is specifically configured to obtain a PI control model, parameters in the PI control model including a proportional coefficient, an integral coefficient and a time parameter; and the PI control model is applied to process the AC voltage difference to obtain the AC current q-axis component reference value.

[0141] The technical advantages of the transient voltage support method embodiment in the present application can be migrated to the transient voltage support device embodiment.

[0142] The transient voltage support device includes a processor and a memory, and the above-mentioned computing unit and the like are stored in the memory as program units, and the corresponding functions are realized by the processor executing the above-mentioned program units stored in the memory. The above-mentioned modules are located in the same processor; or the above-mentioned modules are located in different processors in any combination.

[0143] The processor contains a core, and the corresponding program unit is called from the memory by the core. The core can be set to one or more, and the technical problem of insufficient power grid support capability of the reactive power control strategy and the risk of voltage collapse can be solved by adjusting the core parameters.

[0144] The memory can include non-permanent memory in a computer readable medium, random access memory (RAM) and / or non-volatile memory such as read-only memory (ROM) or flash memory (flash RAM), and the memory includes at least one memory chip.

[0145] The embodiment of the present application provides a direct current power transmission system, including a sending end and a receiving end, the sending end includes a sending end converter, the sending end converter includes a main valve and a support valve, the receiving end includes a receiving end converter, the receiving end converter includes a main valve and a support valve, and any one of the transient voltage support methods is applied to the support valve of the sending end for transient voltage support; and / or, any one of the transient voltage support methods is applied to the support valve of the receiving end for transient voltage support.

[0146] The embodiment of the present application provides a computer readable storage medium, the computer readable storage medium includes a stored program, wherein when the program runs, the computer readable storage medium controls the device where the computer readable storage medium is located to execute the transient voltage support method.

[0147] The embodiment of the present application provides a processor, the processor is used for running a program, wherein when the program runs, the processor executes the transient voltage support method.

[0148] The embodiment of the present application provides a device, the device includes a processor, a memory and a program stored on the memory and executable on the processor, and the processor executes the program to realize the steps in the transient voltage support method. The device in the present application can be a server, a PC, a PAD, a mobile phone and the like.

[0149] The application also provides a computer program product adapted to perform the steps of initializing the method of transient voltage support when executed on a data processing device.

[0150] It should be apparent to those skilled in the art that the modules or steps of the application described above can be implemented with general computing devices, which can be centralized on a single computing device or distributed on a network of multiple computing devices, which can be implemented with program codes executable by computing devices, so that they can be stored in storage devices and executed by computing devices, and in some cases, the steps shown or described can be executed in different order than shown, or they can be made into individual integrated circuit modules or a single integrated circuit module. Thus, the application is not limited to any particular combination of hardware and software.

[0151] Those skilled in the art should clearly understand that the embodiments of the application can be provided as a method, a system, or a computer program product. Therefore, the 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 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.

[0152] The application is described with reference to flowcharts and / or block diagrams according to the methods, devices (systems), and computer program products of the embodiments of the application. It should be understood that each flow and / or block in the flowcharts and / or block diagrams, and the combination of flows and / or blocks in the flowcharts and / or block diagrams can be implemented by computer program instructions. These computer program instructions can be provided to a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing devices to produce a machine, so that the instructions executed by the computer or other programmable data processing devices produce a device that implements the functions specified in the flowcharts and / or block diagrams. Figure 1 The functions specified in a flow or multiple flows and / or blocks Figure 1 The functions specified in a flow or multiple flows and / or blocks

[0153] These computer program instructions can also be stored in a computer readable storage medium that can direct the computer or other programmable data processing devices to work in a specific manner, so that the instructions stored in the computer readable storage medium produce a manufactured product including instruction devices that implement the functions specified in the flowcharts and / or block diagrams. Figure 1 The functions specified in a flow or multiple flows and / or blocks Figure 1 The functions specified in a flow or multiple flows and / or blocks

[0154] These computer program instructions can also be loaded into 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 Figure 1

[0155] In one typical configuration, the computing device includes one or more processors (CPUs), input / output interfaces, network interfaces, and memory.

[0156] The memory can include non-persistent memory and / or volatile memory, such as random access memory (RAM) about which the processor can execute instructions. The memory can also include non-volatile memory, such as read only memory (ROM), electrically programmable read only memory (EPROM), electrically erasable programmable read only memory (EEPROM), programmable read only memory (PROM), or flash memory, for example. Memory is an example of computer readable media.

[0157] Computer readable media includes permanent and non-permanent, removable and non-removable media implemented in any method or technology for storage of information such as 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 programmable read only memory (EEPROM), flash memory or other memory technology, compact disc read only memory (CD-ROM), digital versatile discs (DVDs) or other optical storage, magnetic cassettes, magnetic tapes, magnetic disk storage or other magnetic storage devices, or any other non-transmission medium that can be used to store information accessible to a computing device. According to the definition herein, computer readable media does not include transitory media, such as modulated data signals and carrier waves.

[0158] It should also be noted that the terms "comprising," "including," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements recited, but can also include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without limitation, an element preceded by "comprises a" does not, without more constraints, foreclose the existence of additional identical elements in the process, method, article, or apparatus that comprises the element.

[0159] ​​Any technical features in the above-described embodiments can be combined in any manner, and for the sake of brevity, not all possible combinations are described, but it is understood that the scope of the present disclosure encompasses all possible combinations.

[0160] The above-described embodiments are merely preferred embodiments of the present application and are not intended to limit the present application. The present application can be variously changed and modified by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the scope of the present application.

Claims

1. A method of transient voltage support, characterized by, The transient voltage support method is suitable for a full-control composite converter, the full-control composite converter comprises a main valve and a support valve, the main valve is an IGCT straight string valve, the support valve comprises a full-bridge module, and the transient voltage support method comprises: An effective value of an AC bus voltage is calculated to obtain an AC voltage effective value calculation value; A difference between the AC voltage effective value calculation value and an AC voltage effective value reference value is obtained to obtain an AC voltage difference value; An AC current q-axis component reference value of an AC current in a synchronous rotating coordinate system is determined based on the AC voltage difference value; An AC current q-axis component calculation value and an AC current d-axis component calculation value of the AC current in the synchronous rotating coordinate system are obtained, an AC current d-axis component reference value is obtained, and a trigger signal of the support valve is determined according to the AC current q-axis component reference value, the AC current q-axis component calculation value, the AC current d-axis component reference value and the AC current d-axis component calculation value, and the support valve is triggered and controlled by using the trigger signal.

2. The method of claim 1, wherein, The AC current d-axis component reference value of the AC current in the synchronous rotating coordinate system is obtained, comprising: Three-phase bridge arm voltage measurement values of the support valve are obtained to obtain a first bridge arm voltage measurement value, a second bridge arm voltage measurement value and a third bridge arm voltage measurement value; An average value of the first bridge arm voltage measurement value, the second bridge arm voltage measurement value and the third bridge arm voltage measurement value is calculated to obtain a bridge arm voltage average value measurement value; A bridge arm voltage average value reference value is obtained, and the AC current d-axis component reference value is determined according to the bridge arm voltage average value measurement value and the bridge arm voltage average value reference value.

3. The method of claim 2, wherein, The bridge arm voltage average value reference value is obtained, comprising: The number of sub-modules of a single-phase bridge arm of the support valve and the use voltages of the sub-modules are obtained; The product of the use voltages of the sub-modules and the number of the sub-modules is determined as the bridge arm voltage average value reference value.

4. The method of claim 1, wherein, The AC current q-axis component calculation value and the AC current d-axis component calculation value of the AC current in the synchronous rotating coordinate system are obtained, comprising: The AC bus voltage is processed by a phase-locked loop to obtain a phase-locked phase; Three-phase currents output by the support valve are obtained, and the AC current q-axis component calculation value and the AC current d-axis component calculation value in a two-phase rotating coordinate are obtained after the three-phase currents output by the support valve are synchronized by the phase-locked phase and processed by coordinate transformation.

5. The method of claim 1, wherein, The trigger signal of the support valve is determined according to the AC current q-axis component reference value, the AC current q-axis component calculation value, the AC current d-axis component reference value and the AC current d-axis component calculation value, comprising: Closed-loop decoupling control is performed on the AC current q-axis component reference value, the AC current q-axis component calculation value, the AC current d-axis component reference value and the AC current d-axis component calculation value to obtain a q-axis component and a d-axis component of an output voltage of the support valve; The q-axis component and the d-axis component of the output voltage are phase-synchronized by using the phase-locked phase, and a voltage modulation wave in a three-phase static coordinate is generated after coordinate transformation. The voltage modulation wave in the three-phase static coordinate is subjected to nearest level approximation modulation processing to obtain a trigger signal of the support valve.

6. The method of claim 1, wherein, An effective value of the AC bus voltage is calculated to obtain an AC voltage effective value calculation value, including: The AC bus voltage is subjected to coordinate transformation to obtain a q-axis component and a d-axis component of the AC bus voltage; A square value of the q-axis component of the AC bus voltage is obtained to obtain a first square value; A square value of the d-axis component of the AC bus voltage is obtained to obtain a second square value; The first square value and the second square value are integrated in a time domain to obtain an integral value, and a ratio of the integral value and integral time is calculated to obtain an average value of voltage square; The average value of voltage square is subjected to square root processing to obtain the AC voltage effective value calculation value.

7. The method of claim 1 to 6, wherein, An AC current q-axis component reference value of the AC current in the synchronous rotating coordinate system is determined based on the AC voltage difference value, including: A PI control model is obtained, and parameters in the PI control model include a proportional coefficient, an integral coefficient and a time parameter; The PI control model is applied to process the AC voltage difference value to obtain the AC current q-axis component reference value.

8. A transient voltage support device, characterized by, The transient voltage support device is applicable to a full-control composite converter, the full-control composite converter includes a main valve and a support valve, the main valve is an IGCT straight string valve, the support valve includes a full-bridge module, and the transient voltage support device includes: A calculation unit calculates an effective value of an AC bus voltage to obtain an AC voltage effective value calculation value; An obtaining unit obtains a difference value between the AC voltage effective value calculation value and an AC voltage effective value reference value to obtain an AC voltage difference value; A determination unit determines an AC current q-axis component reference value of an AC current in a synchronous rotating coordinate system based on the AC voltage difference value; An obtaining determination unit obtains an AC current q-axis component calculation value, an AC current d-axis component reference value and an AC current d-axis component calculation value of the AC current in the synchronous rotating coordinate system, and determines a trigger signal of the support valve according to the AC current q-axis component reference value, the AC current q-axis component calculation value, the AC current d-axis component reference value and the AC current d-axis component calculation value, and triggers and controls the support valve by using the trigger signal.

9. A computer-readable storage medium, characterized in that, The computer readable storage medium includes a stored program, and when the program runs, controls a device where the computer readable storage medium is located to execute the transient voltage support method in any one of claims 1 to 7.

10. A direct current power transmission system, characterized by Including: A sending end and a receiving end, the sending end includes a sending end converter, the sending end converter includes a main valve and a support valve, the receiving end includes a receiving end converter, and the receiving end converter includes a main valve and a support valve; A controller connected with the sending end and the receiving end, used to execute the transient voltage support method in any one of claims 1 to 7 to support the support valve of the sending end in transient voltage, or support the support valve of the receiving end in transient voltage.

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