Reactive power control and SVG coordinated control method and system for DC power transmission system

Abstract

The present invention relates to a reactive power control and SVG coordinated control method and system for a DC power transmission system, the method comprising: calculating the reactive power △Q exchanged between the converter station and the AC system; setting the dead zone range of △Q and limiting the output of △Q; setting the limiting conditions of the SVG's adjustment capability to determine whether the reactive power emitted by the SVG is limited; based on whether the reactive power emitted by the SVG is limited and the reactive power limitation result exchanged between the converter station and the AC system, calculating the input of the PI controller in the QPC module to complete the reactive power control and SVG coordinated control process. When the control method of the present invention is adopted, the operation time of the converter greater than the rated angle is significantly reduced, the converter loss is effectively reduced, the power rise and fall process of the DC system is stable, and the voltage fluctuation of the AC system caused by the switching of the passive filter is greatly reduced.

Description

Technical Field

[0001] The invention relates to a coordinated control method and system of reactive power control and SVG (Static Var Generator) of a direct current power transmission system, and relates to the field of direct current power transmission of electric power systems. Background Art

[0002] The DC transmission system can realize long-distance and large-capacity power transmission, can be used for asynchronous networking of power systems, and plays a positive role in improving the safety and stability of the system. The operation of the converter, the core component responsible for AC-DC conversion, consumes a large amount of reactive power, so reactive power compensation control is an extremely critical link in the control strategy of the DC transmission system. First, reasonable reactive power compensation control can ensure the continuous and stable operation of the DC system. Secondly, by utilizing the fast and flexible regulation characteristics of the DC transmission system, reactive power control can be used as a means of regulating the voltage of the AC power grid to provide a stable AC voltage for the stable operation of the DC system.

[0003] The DC transmission system is usually equipped with the following reactive power control functions: Over voltage control—AC overvoltage control function, which removes the filter group according to the overvoltage of the AC filter bus. ABS Min Filter—Absolute minimum filter function, which is the filter group required to prevent the filter equipment from overloading. Umax / Umin—AC bus maximum / minimum voltage limit, which is used to monitor and limit the steady-state AC bus voltage of the converter station. Q_Maximum—Maximum reactive power limit function, which limits the number of filter groups put into operation. Min Filter—Minimum filter function, which is the minimum filter group required to be put into operation to meet the requirements of filtering harmonics. Q control / U control—Reactive power exchange control / voltage control, which controls the reactive power exchange amount between the converter station and the AC system to the set reference value / controls the AC bus voltage of the converter station to the set reference value. QPC—Converter reactive power control, which increases the reactive power consumption of the converter station by increasing the ignition angle / shutdown angle. The reactive power consumption of the converter under DC steady-state conditions can be expressed by the following formula:

[0004]

[0005] In the formula, Q conv is the reactive power consumed by the converter, I d is the DC current, U di0 is the ideal no-load DC voltage of each 6-pulsation valve group, u is the commutation angle, and α is the trigger angle.

[0006] When the DC transmission system is running at low power, it must be put into use with a certain number of AC filters due to the harmonic restrictions at the access point of the converter station and the performance restrictions of the AC filter equipment. In this low-power operation, the reactive power consumed by the converter is less than the reactive power provided by the AC filter, which causes the DC converter station to inject a large amount of residual reactive power into the AC system, which is easy to cause problems such as overvoltage in the AC system. For this reason, the QPC function is used in the reactive power control strategy as a control strategy to optimize the reactive power exchange between the converter station and the system during low-load operation and power reduction. When the DC transmission power is constant, the inverter side increases the reactive power consumption of the converter by increasing the shutdown angle; the rectifier side increases the reactive power consumption of the converter by adjusting the converter transformer tap changer gear to increase the trigger angle. The converter station is equipped with SVG to smooth the voltage fluctuation of the passive filter switching and to provide voltage support during AC system fault crossing. However, if the SVG control and QPC control do not match, the converter will cause the converter to operate at a greater angle than the rated angle for a long time, resulting in increased losses of the converter, and the switching of the passive filter during the DC power increase and decrease process will also cause fluctuations in the DC power and AC system voltage. Summary of the invention

[0007] In view of the above problems, the purpose of the present invention is to provide a method and system for reactive power control and SVG coordinated control of a DC power transmission system that can utilize the fast adjustment speed of SVG, give priority to using SVG to adjust the converter station to exchange reactive power with the system, minimize the operating time of the converter greater than the rated angle, thereby reducing converter losses, and at the same time avoid passive filter switching to cause DC power and AC system voltage fluctuations.

[0008] To achieve the above object, the present invention adopts the following technical solutions:

[0009] In a first aspect, the present invention provides a method for coordinated control of reactive power and SVG in a DC power transmission system, comprising:

[0010] Based on the capacitive reactive power Q provided by the passive filter invested in this station acf , the capacitive reactive power consumed by the converter valve of this station Q con And the reactive power Q emitted by SVG at this station svg , calculate the reactive power △Q exchanged between this converter station and the AC system;

[0011] Set the dead zone range of △Q and limit the output of △Q;

[0012] Set the limiting conditions of the SVG's regulation capability and determine whether the reactive power generated by the SVG is limited;

[0013] Based on whether the reactive power generated by SVG is limited and the reactive power limitation results exchanged between the converter station and the AC system, the reactive power control and SVG coordinated control process is completed.

[0014] Furthermore, a reactive power compensation device SVG is pre-configured in the converter station, and a QPC module is pre-configured in the DC control system of the converter station.

[0015] Furthermore, the method further includes the step of determining whether to put reactive power control and coordinated control of SVG into operation according to set conditions in advance, including:

[0016] When the local converter is in the unlocked state Deblock=1, the local reactive control is in the Q control mode, and Enable=1, the coordinated control of reactive control and SVG is put into operation; otherwise, the coordinated control of reactive control and SVG is exited, and the PI integrator in the QPC module is cleared.

[0017] Furthermore, the converter station exchanges reactive power △Q with the AC system:

[0018] △Q=Q acf -(Q con +Q svg ).

[0019] Furthermore, the dead zone range of △Q is set, and △Q is output limited, including:

[0020] When the reactive power △Q exchanged between the converter station and the system is within the dead zone, the QPC module does not start, and the γ angle maintains the value of the previous moment, then the △Q output after limitation is 0;

[0021] If △Q exceeds the control dead zone limit range of QPC, the QPC module starts to control △Q within the dead zone. When the γ angle reaches its range limit, the QPC module loses its control ability and the output △Q value after limitation remains unchanged.

[0022] Furthermore, setting the restriction condition of the regulation capability of SVG to determine whether the reactive power generated by SVG is limited includes:

[0023] Q svg Greater than or equal to SVG's Q svgref Control dead zone means that the reactive power emitted by SVG is limited;

[0024] Q svg Smaller than SVG's Q svgref Control dead zone means that the reactive power output of SVG is unlimited, where Q svgref It is the reactive power target value emitted by SVG.

[0025] Furthermore, based on whether the reactive power generated by the SVG is limited and the reactive power limitation results exchanged between the converter station and the AC system, the reactive power control and SVG coordinated control process is completed, including:

[0026] If the SVG output is limited, the input of the PI controller of the QPC module is the output of △Q after limitation, that is, the SVG has lost its reactive power regulation capability. At this time, the QPC module starts to control the converter station to exchange reactive power with the system within the dead zone, sets the limit of the QPC output extinction angle increment, and calculates the output value △γ of the QPC module;

[0027] If the SVG output is not limited, the input of the PI controller is a fixed negative value -Qset, that is, the SVG has the ability to adjust reactive power. The SVG is used to control the converter station to exchange reactive power with the system, and the arc extinction angle is reduced to the rated operating angle. At the same time, the output of QPC is minimized as much as possible to reduce the operating time of the converter greater than the rated angle.

[0028] In a second aspect, the reactive power control and SVG coordinated control system of a DC power transmission system provided by the present invention is characterized in that the system comprises:

[0029] The reactive power calculation unit is configured to provide capacitive reactive power Q based on the passive filter input at the station. acf , the capacitive reactive power consumed by the converter valve of this station Q con And the reactive power Q emitted by SVG at this station svg , calculate the reactive power △Q exchanged between this converter station and the AC system;

[0030] The dead zone setting unit is configured to set the dead zone range of △Q and limit the output of △Q;

[0031] The SVG setting unit is configured to set a restriction condition of the SVG's regulation capability and determine whether the reactive power generated by the SVG is limited;

[0032] The coordination control unit is configured to complete the reactive power control and SVG coordination control process based on whether the reactive power emitted by the SVG is limited and the reactive power limitation result exchanged between the converter station and the AC system.

[0033] In a third aspect, the present invention further provides an electronic device, comprising computer program instructions, wherein the program instructions, when executed by a processor, are used to implement the reactive power control and SVG coordinated control method of the DC power transmission system.

[0034] In a fourth aspect, the present invention further provides a computer-readable storage medium, characterized in that computer program instructions are stored on the computer-readable storage medium, wherein the program instructions are used to implement the reactive power control and SVG coordinated control method of the DC transmission system when executed by a processor.

[0035] The present invention adopts the above technical solution, and has the following characteristics:

[0036] 1. The present invention determines whether the SVG has the regulating capability and adjusts the reactive power control strategy of the DC system. When the SVG has the regulating capability, the SVG is preferentially used to control the converter station to exchange reactive power △Q with the system, and at the same time, the QPC is allowed to reduce the output until the output is 0, and the arc extinction angle is reduced to the rated angle at the lowest, thereby reducing the operating time of the converter greater than the rated angle and reducing the converter loss. When the SVG loses the control capability, the QPC increases the output and increases the arc extinction angle to control △Q within the dead zone, thereby avoiding unnecessary fluctuations in the DC power and the AC system voltage caused by the switching of the passive filter.

[0037] 2. When the control method of the present invention is adopted, the operating time of the converter greater than the rated angle is significantly reduced, the converter loss is effectively reduced, the power rise and fall process of the DC system is smooth, and the voltage fluctuation of the AC system caused by the switching of the passive filter is greatly reduced.

[0038] In summary, the present invention can be widely applied to direct current transmission systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the detailed description of the preferred embodiments below. The accompanying drawings are only for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the present invention. Throughout the accompanying drawings, the same reference numerals are used to represent the same components. In the accompanying drawings:

[0040] Figure 1 It is a schematic diagram of the coordinated control method of QPC and SVG according to an embodiment of the present invention.

[0041] Figure 2 The figure is a schematic diagram of simulation results of power increase of a DC system when the control method proposed in an embodiment of the present invention is adopted.

[0042] Figure 3 It is a schematic diagram of simulation results of power reduction of a DC system when the control method proposed in an embodiment of the present invention is adopted.

[0043] Figure 4 FIG. 4 is a structural diagram of an electronic device according to an embodiment of the present invention. DETAILED DESCRIPTION

[0044] It should be understood that the terms used herein are only for the purpose of describing specific example embodiments and are not intended to be limiting. Unless the context clearly indicates otherwise, the singular forms "one", "an" and "said" as used herein may also be meant to include plural forms. The terms "include", "comprise", "contain", and "have" are inclusive, and therefore specify the existence of stated features, steps, operations, elements and / or parts, but do not exclude the existence or addition of one or more other features, steps, operations, elements, parts, and / or combinations thereof. The method steps, processes, and operations described herein are not interpreted as necessarily requiring them to be performed in the specific order described or illustrated, unless the execution order is clearly indicated. It should also be understood that additional or alternative steps may be used.

[0045] The reactive power control and SVG coordinated control method of the DC transmission system proposed by the present invention configures a reactive power compensation device SVG in the converter station, configures a QPC module in the DC control system of the converter station, and sets a startup dead zone of the QPC function; when the converter station exchanges reactive power △Q with the system within the dead zone, the QPC module does not start, and the γ angle maintains the value of the previous moment; when △Q is about to exceed the dead zone, the QPC module starts to control △Q within the dead zone, and when the γ angle reaches its range limit, the QPC module loses control ability, and the control target of SVG is △Q is 0. When SVG reaches the limit, the value of the previous moment is maintained. When SVG has the adjustment ability, △Q is controlled by SVG first, and at the same time, the QPC module is allowed to reduce the output until the output is 0, and the arc extinction angle is reduced to the rated angle at the lowest, thereby reducing the operating time of the converter greater than the rated angle and reducing the converter loss; when SVG loses the control ability, the QPC module increases the output, increases the arc extinction angle, and controls △Q within the dead zone, thereby avoiding unnecessary fluctuations in DC power and AC system voltage caused by passive filter switching.

[0046] The exemplary embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments described herein. On the contrary, these embodiments are provided in order to enable a more thorough understanding of the present invention and to fully convey the scope of the present invention to those skilled in the art.

[0047] Embodiment 1: Figure 1 As shown, the reactive power control and SVG coordinated control method of the DC power transmission system provided in this embodiment includes the following steps:

[0048] Step S1: configure a reactive power compensation device SVG in the converter station, configure a QPC module in the DC control system of the converter station, and determine whether to activate reactive power control and coordinated control of SVG according to set conditions.

[0049] Specifically, when the converter of this station is in the unlocked state Deblock=1, the reactive control of this station is in the Q control mode, and Enable=1 (manually start the coordinated control of reactive control and SVG), the coordinated control of reactive control and SVG is started; otherwise, the coordinated control of reactive control and SVG is exited, and the PI integrator of QPC is cleared to avoid the calculation result of this time affecting the calculation of the next start of this control function.

[0050] Step S2: Calculate the capacitive reactive power Q provided by the passive filter used in this station acf , which can be determined based on the number and capacity of ACF groups invested.

[0051] Specifically, the capacitive reactive power Q of this embodiment is acf The calculation formula is shown below, taking this as an example, but not limited to this:

[0052] Q acf =Q acf1 +Q acf2 +......+Q acfn

[0053] In the formula, Q acfn is the reactive capacity of the small group passive filter ACF, and n is the number of small group passive filters ACF put into use.

[0054] Step S3: Calculate the capacitive reactive power Q consumed by the converter valve of this station con .

[0055] Specifically, the capacitive reactive power Q of this embodiment is conf The calculation formula is shown below, which is taken as an example and is not limited to this.

[0056]

[0057] In the formula, I d is the DC current, U di0 is the ideal no-load DC voltage of each 6-pulsation valve group, u is the commutation angle, α is the trigger angle. When calculating the reactive power consumption of the inverter station, replace α with γ. This function can be used in both the rectifier station and the inverter station. If it is in the rectifier station, use α to calculate Q con If it is at the inverter station, use γ to calculate Q con .

[0058] Step S4: Calculate the reactive power Qsvg generated by the local SVG, which can be calculated based on the AC voltage and AC current of the SVG access point.

[0059] Step S5: Calculate the reactive power exchanged between the converter station and the AC system:

[0060] △Q=Q acf-(-(Q con +Q svg );

[0061] Step S6: Set the dead zone range of △Q and limit the output of △Q.

[0062] Specifically, when the reactive power △Q exchanged between the converter station and the system is within the dead zone, the QPC module will not start, and the γ angle will maintain the value of the previous moment, then the output of △Q after limitation is 0; if △Q exceeds the control dead zone limit range of QPC, the QPC module will start and control △Q within the dead zone. When the γ angle reaches its range limit, the QPC module loses control capability and the value of the output △Q after limitation remains unchanged. The control dead zone of QPC is determined according to system requirements.

[0063] Step S7: setting the restriction condition of the regulation capability of SVG, and judging whether the reactive power generated by SVG is limited.

[0064] Specifically, determine whether the SVG output is limited: Q svg Q greater than or equal to the SVG control dead zone svgref value, the reactive power emitted by SVG is limited; Q svg Q less than SVG control dead zone svgref value, the reactive power generated by SVG is not limited. svgref is the reactive power target value emitted by SVG, Q svg It is the reactive power actually generated by SVG. The control dead zone of SVG is determined according to the control accuracy of SVG and system requirements.

[0065] Step S8: Based on whether the reactive power generated by the SVG is limited and the reactive power limitation results exchanged between the converter station and the AC system, the input of the PI controller is calculated to achieve reactive power control and coordinated control of the SVG.

[0066] Specifically, the input quantity of the PI controller is calculated, including:

[0067] If the SVG output is limited, the input of the PI controller is the output of △Q after limitation, that is, the SVG has lost its reactive power regulation capability. At this time, the QPC module starts to control the converter station to exchange reactive power with the system within the dead zone, and sets the limit of the QPC output extinction angle increment. Further, the QPC output value △γ is calculated. △γ is the output of the PI controller, and its upper limit is determined by the active power of the DC system. The specific value is determined by the DC system design, and its lower limit is 0.

[0068] If the SVG output is not limited, the input of the PI controller is a fixed negative value -Qset, that is, the SVG has the ability to adjust reactive power. The SVG is used to control the converter station to exchange reactive power with the system, and the arc extinction angle is reduced to the rated operating angle. At the same time, the output of QPC is minimized as much as possible to reduce the operating time of the converter greater than the rated angle.

[0069] This embodiment takes the Fujian-Guangdong back-to-back DC project as an example, and uses the RTDS simulation test platform of this project to carry out a closed-loop simulation joint adjustment test of the DC control and protection equipment. The DC control and protection system with the same equipment model as the Fujian-Guangdong DC project, the same program core functions, and redundant configuration is used for RTDS simulation testing to verify the test effect of this function.

[0070] The test conditions are dual-unit operation, SVG is configured on the inverter side, and the DC control system is configured with QPC function. Figure 2 The process of increasing the DC power of a single unit from 0 to 1000MW. Figure 3 It is the process of reducing the DC power of a single unit from 1000MW to 0.

[0071] The test results show that if Figure 2 and Figure 3 As shown in the figure, when SVG has the regulation capability, the reactive power exchanged between the converter station and the system is regulated by SVG, and the arc extinction angle is reduced to the rated operating angle; when SVG loses the control capability and the DC system has excess reactive power, the arc extinction angle increases, and the AC system voltage and DC system power rise and fall smoothly.

[0072] Embodiment 2: Embodiment 1 above provides a reactive power control and SVG coordinated control method for a DC power transmission system. Correspondingly, this embodiment provides a reactive power control and SVG coordinated control system for a DC power transmission system. The system provided in this embodiment can implement the reactive power control and SVG coordinated control method for a DC power transmission system of Embodiment 1, and the system can be implemented by software, hardware, or a combination of software and hardware. For the convenience of description, this embodiment is described in various units according to their functions. Of course, the functions of each unit can be implemented in the same or multiple software and / or hardware during implementation. For example, the system may include integrated or separate functional modules or functional units to perform the corresponding steps in each method of Embodiment 1. Since the system of this embodiment is basically similar to the method embodiment, the description process of this embodiment is relatively simple, and the relevant parts can refer to the partial description of Embodiment 1. The embodiment of the reactive power control and SVG coordinated control system for a DC power transmission system provided by the present invention is only schematic.

[0073] The reactive power control and SVG coordinated control system of the DC power transmission system provided in this embodiment includes:

[0074] The reactive power calculation unit is configured to provide capacitive reactive power Q based on the passive filter input at the station. acf , the capacitive reactive power consumed by the converter valve of this station Q con And the reactive power Q emitted by SVG at this station svg , calculate the reactive power △Q exchanged between this converter station and the AC system;

[0075] The dead zone setting unit is configured to set the dead zone range of △Q and limit the output of △Q;

[0076] The SVG setting unit is configured to set a restriction condition of the SVG's regulation capability and determine whether the reactive power generated by the SVG is limited;

[0077] The coordination control unit is configured to complete the reactive power control and SVG coordination control process based on whether the reactive power emitted by the SVG is limited and the reactive power limitation result exchanged between the converter station and the AC system.

[0078] Embodiment 3: This embodiment provides an electronic device corresponding to the reactive power control and SVG coordinated control method of the DC transmission system provided in this embodiment 1. The electronic device may be an electronic device for a client, such as a mobile phone, a laptop computer, a tablet computer, a desktop computer, etc., to execute the method of embodiment 1.

[0079] like Figure 4 As shown, the electronic device includes a processor, a memory, a communication interface and a bus, and the processor, the memory and the communication interface are connected through the bus to complete mutual communication. The bus can be an Industry Standard Architecture (ISA) bus, a Peripheral Component Interconnect (PCI) bus or an Extended Industry Standard Component (EISA) bus, etc. The memory stores a computer program that can be run on the processor, and when the processor runs the computer program, it executes the reactive power control and SVG coordinated control method of the DC power transmission system provided in the first embodiment. Those skilled in the art can understand that Figure 4 The structure shown in the figure is only a block diagram of a part of the structure related to the scheme of the present application, and does not constitute a limitation on the computing device to which the scheme of the present application is applied. The specific computing device may include more or fewer components than shown in the figure, or combine certain components, or have a different arrangement of components.

[0080] In some implementations, the logic instructions in the above-mentioned memory can be implemented in the form of software functional units and can be stored in a computer-readable storage medium when sold or used as an independent product. Based on this understanding, the technical solution of the present application can be essentially or partly embodied in the form of a software product that contributes to the prior art, and the computer software product is stored in a storage medium, including several instructions to enable a computer device (which can be a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the method described in each embodiment of the present application. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), optical disk and other media that can store program codes.

[0081] In some other implementations, the processor may be a central processing unit (CPU), a digital signal processor (DSP), or other general-purpose processors of various types, which are not limited herein.

[0082] Embodiment 4: The reactive power control and SVG coordinated control method of the DC power transmission system of the embodiment 1 may be specifically implemented as a computer program product, which may include a computer-readable storage medium carrying computer-readable program instructions for executing the reactive power control and SVG coordinated control method of the DC power transmission system described in the embodiment 1.

[0083] Computer readable storage media can be tangible devices that hold and store instructions used by instruction execution devices. Computer readable storage media can be, for example, but not limited to, electronic storage devices, magnetic storage devices, optical storage devices, electromagnetic storage devices, semiconductor storage devices, or any combination thereof.

[0084] Each embodiment in this specification is described in a progressive manner, and the same and similar parts between the embodiments can be referred to each other, and each embodiment focuses on the differences from other embodiments. In particular, for the system embodiment, since it is basically similar to the method embodiment, the description is relatively simple, and the relevant parts can be referred to the partial description of the method embodiment. In the description of this specification, the description of the reference terms "one embodiment", "some implementations", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the embodiment of this specification. In this specification, the schematic representation of the above terms does not necessarily target the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples without contradiction.

[0085] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0086] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0087] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0088] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for coordinated control of reactive power and SVG in a DC power transmission system, characterized in that include: Pre-configure reactive power compensation device SVG in the converter station and configure QPC module in the DC control system of the converter station; Based on the capacitive reactive power provided by the passive filter invested in this station Q acf , capacitive reactive power consumed by the converter valve of this station Q con And the reactive power emitted by SVG Q svg , calculate the reactive power △Q exchanged between this converter station and the AC system; Set the dead zone range of △Q and limit the output of △Q, including: When the reactive power △Q exchanged between the converter station and the system is within the dead zone, the QPC module does not start, and the γ angle maintains the value of the previous moment, then the △Q output after limitation is 0, where the γ angle is the arc extinction angle; If △Q exceeds the control dead zone limit range of QPC, the QPC module starts to control △Q within the dead zone. When the γ angle reaches its range limit, the QPC module loses its control ability and the output △Q value after limitation remains unchanged. Set the limiting conditions of the SVG's regulation capability and determine whether the reactive power generated by the SVG is limited; Based on whether the reactive power generated by SVG is limited and the reactive power limitation results exchanged between the converter station and the AC system, the reactive power control and SVG coordinated control process is completed, including: If the SVG output is limited, the input of the PI controller of the QPC module is the output of △Q after limitation, that is, the SVG has lost its reactive power regulation capability. At this time, the QPC module starts to control the converter station to exchange reactive power with the system within the dead zone, sets the limit of the QPC output extinction angle increment, and calculates the output value △γ of the QPC module, where △γ is the extinction angle increment; If the SVG output is not limited, the input of the PI controller is a fixed negative value -Qset, that is, the SVG has the ability to adjust reactive power. The SVG is used to control the converter station to exchange reactive power with the system, and the arc extinction angle is reduced to the rated operating angle. At the same time, the output of QPC is minimized as much as possible to reduce the operating time of the converter greater than the rated angle.

2. The method for coordinated control of reactive power and SVG of a DC power transmission system according to claim 1, characterized in that: The step of determining whether to put reactive power control and coordinated control of SVG into operation according to set conditions in advance includes: When the local converter is in the unlocked state Deblock=1, the local reactive control is in the Q control mode, and Enable=1, the coordinated control of reactive control and SVG is put into operation; otherwise, the coordinated control of reactive control and SVG is exited, and the PI integrator in the QPC module is cleared.

3. The method for coordinated control of reactive power and SVG of a DC power transmission system according to claim 1, characterized in that: The converter station exchanges reactive power △Q with the AC system: △Q= Q acf -（ Q con + Q svg ）。 4. The method for coordinated control of reactive power and SVG in a DC power transmission system according to claim 1, characterized in that: Set the restriction conditions of SVG's regulation capability and determine whether the reactive power generated by SVG is limited, including: Q svg Greater than or equal to SVG Q svgref Control dead zone means that the reactive power emitted by SVG is limited; Q svg Smaller than SVG's Q svgref Control dead zone means that the reactive power output of SVG is unlimited, where Q svgref It is the reactive power target value emitted by SVG.

5. A reactive power control and SVG coordinated control system for a DC power transmission system that implements the reactive power control and SVG coordinated control method for a DC power transmission system as claimed in any one of claims 1 to 4, characterized in that: The system includes: The reactive power calculation unit is configured to provide capacitive reactive power based on the passive filter used in the station. Q acf , capacitive reactive power consumed by the converter valve of this station Q con And the reactive power emitted by SVG Q svg , calculate the reactive power △Q exchanged between this converter station and the AC system; The dead zone setting unit is configured to set the dead zone range of △Q and limit the output of △Q; The SVG setting unit is configured to set a restriction condition of the SVG's regulation capability and determine whether the reactive power generated by the SVG is limited; The coordination control unit is configured to complete the reactive power control and SVG coordination control process based on whether the reactive power emitted by the SVG is limited and the reactive power limitation result exchanged between the converter station and the AC system.

6. An electronic device, characterized in that: The method comprises computer program instructions, wherein the program instructions are used to implement the reactive power control and SVG coordinated control method of the direct current transmission system as claimed in any one of claims 1 to 4 when executed by a processor.

7. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores computer program instructions, wherein the program instructions are used to implement the reactive power control and SVG coordinated control method of a direct current transmission system as claimed in any one of claims 1 to 4 when executed by a processor.

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