Voltage control method and device for island conversion of direct-current power transmission system

Abstract

The invention provides a voltage control method and device for island conversion of a direct-current power transmission system, the voltage control method is applied to a power system stabilizer of the direct-current power transmission system, and the method comprises the following steps: if the frequency input to a power system controller is greater than a preset threshold value, judging a direct-current island conversion mode; if the DC island conversion is the active island conversion, closing a frequency signal branch of the power system controller, keeping a power signal branch of the power system controller effective, and restoring the frequency signal branch of the power system controller to be effective after the DC power transmission system enters the DC island state; and if the DC island conversion is passive conversion and the island signal is judged to be true at the output end of the power system controller, reducing the amplitude of the output end of the power system controller according to a preset proportion, and recovering the amplitude of the output end of the power system controller after the DC power transmission system enters the DC island state.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of direct current transmission, in particular to a voltage control method and device for island conversion of a direct current transmission system. BACKGROUND

[0002] Direct current transmission is a power transmission mode in which alternating current is converted into direct current by a converter station for transmission. Due to the characteristics of economic efficiency, large capacity and long distance transmission, direct current transmission has been widely applied. The core equipment of direct current transmission includes a converter station, a direct current line and a power filter, etc., and has the advantages of low line cost and long transmission distance. This technology is mainly applied to high-power transmission and non-synchronous alternating current system networking, and the transmission voltage can reach ±1100 kV.

[0003] The existing operation modes of the direct current transmission system include a networking operation mode and an island operation mode. The networking operation mode refers to an operation mode in which the converter stations on both sides are in networking operation with the main grid, and the power exchange is realized through the connection with the external grid to improve the reliability of power supply. The island operation mode refers to an operation mode in which the converter station and the nearby power station and line form an independent small system, and the alternating current connection with the main grid is disconnected.

[0004] With the construction of a new batch of giant energy bases, higher voltage level and larger capacity ultra-high voltage direct current transmission systems are built in a larger range. The above-mentioned energy bases are generally located in remote areas, and a number of sending end power stations are connected to the ultra-high voltage direct current converter station through the supporting alternating current transmission system to form a direct current sending end network, which often forms a weak connection with the main grid. Based on the above characteristics, in the engineering planning, the ultra-high voltage direct current sending end generally adopts the sending mode of the island operation mode. At the same time, in the power grid operation, there are N-1 / N-2 fault conditions of the alternating current interconnection line of the direct current sending end system and the main grid, and the direct current sending end network is forced to lose connection with the main grid to form an island operation mode.

[0005] The direct current island system has poor voltage stability due to the weak sending end network. In the case of low voltage, the trigger delay angle of the rectifier side is automatically reduced, and the minimum is as low as 5°. The reduction of the trigger delay angle reduces the reactive power consumption of the converter station, which is beneficial to voltage stability. However, the reactive power control and converter variable position control mode of the direct current transmission system may affect the voltage stability of the island system. For example, when the reactive power control mode is adopted, the lower limit of the converter bus voltage amplitude is actually increased, and at the same power transmission level, more reactive power groups are put into the system, the system steady-state voltage level is higher, but the voltage stability is poor, and the voltage instability boundary is closer.

[0006] ​The rotating inertia of the island system is small, and the frequency or voltage fluctuation distance is far, so that the output fluctuation or the composite mutation easily causes the instability of the DC bus voltage. The DC bus voltage is the barometer of the system power balance, and the instability of the DC bus voltage will trigger a chain reaction, for example, the overvoltage triggers the arrester or the blocking converter, causing the power supply interruption. When the voltage fluctuation of the DC island system containing new energy exceeds the tolerance range of the inverter, the wind power / photovoltaic unit automatically disconnects from the grid. The negative damping characteristic may excite shaft torsional vibration, threatening the safety of the generator.

[0007] The current conventional hydropower station adopts PSS power system stabilizer 2B type power system stabilizer. The PSS 2B type power system stabilizer adopts double input mode, and the double signal inputs of speed deviation and electromagnetic power deviation are input to avoid the "reverse adjustment phenomenon" caused by single signal. In fact, the PSS 2B adjusts the internal potential of the excitation system, thereby adjusting the active power output of the generator, to enhance the damping ratio of the system and suppress low-frequency oscillation. The core lies in that the small change of the generator speed or power is used to generate a control signal, and then the excitation current is affected. However, the PSS power system stabilizer with reasonable parameter setting can adapt to most system operation conditions, but in the DC sending end island system, if the tie-line power is sent out, that is, the power is sent out from the island system to the near-zone AC network, in the networking island conversion process, the DC loop bus voltage and the power station bus voltage all appear voltage distortion, and in the serious case, the transient voltage exceeds the normal operation range. SUMMARY

[0008] Based on this, the application provides a voltage control method and device for DC power transmission system island conversion, which effectively solves the problem of abnormal rise of generator terminal voltage caused by excessive reverse adjustment of frequency signal, which endangers the safety of power station near-zone equipment, by processing method for eliminating voltage high caused by frequency signal branch in the networking island conversion process.

[0009] In the first aspect, the application provides a voltage control method for DC power transmission system island conversion, which is applied to a power system stabilizer of a DC power transmission system, and includes:

[0010] If the frequency input to the power system controller is greater than a preset threshold, the mode of DC island conversion is judged;

[0011] If the DC island conversion is active island conversion, the frequency signal branch of the power system controller is closed, the power signal branch of the power system controller is kept effective, and after the DC power transmission system enters the DC island state, the frequency signal branch of the power system controller is restored to be effective;

[0012] If the direct current island conversion is passive conversion and the island signal at the output end of the power system controller is true, the output end amplitude of the power system controller is reduced by a preset proportion, and the output end amplitude of the power system controller is restored after the direct current power transmission system enters the direct current island state.

[0013] Further, the frequency signal branch of the power system controller is closed, specifically:

[0014] The first time constant and the second time constant of the reset filter in the frequency signal branch of the power system controller are adjusted to 0;

[0015] The frequency signal branch of the power system controller is restored, specifically:

[0016] The first time constant and the second time constant of the reset filter in the frequency signal branch of the power system controller are adjusted to the original first time constant and the original second time constant before the direct current power transmission system island conversion.

[0017] Further, the output end amplitude of the power system controller is reduced by a preset proportion, specifically:

[0018] The upper limit of the output end amplitude of the power system controller is reduced to an adjusted upper limit by a preset proportion, and the lower limit of the output end amplitude of the power system controller is increased to an adjusted lower limit by a preset proportion;

[0019] The output end amplitude of the power system controller is restored, specifically:

[0020] The upper limit of the output end amplitude of the power system controller is increased from the adjusted upper limit to the original upper limit, and the lower limit of the output end amplitude of the power system controller is increased from the adjusted lower limit to the original lower limit.

[0021] Further, the preset proportion is 5%, 3% or 2%.

[0022] In a second aspect, the application also provides a voltage control device for direct current power transmission system island conversion, which is applied to a power system stabilizer of a direct current power transmission system, and comprises:

[0023] A frequency over-reverse adjustment module is configured to determine the mode of direct current island conversion if the frequency input to the power system controller is greater than a preset threshold value.

[0024] A first voltage control module is configured to close the frequency signal branch of the power system controller if the direct current island conversion is active island conversion, while keeping the power signal branch of the power system controller effective, and to restore the frequency signal branch of the power system controller effective after the direct current power transmission system enters the direct current island state.

[0025] a second voltage control module, configured to reduce the output amplitude of the power system controller by a preset ratio if the DC island is converted into passive conversion and the island signal at the output of the power system controller is true, and restore the output amplitude of the power system controller after the DC power transmission system enters the DC island state.

[0026] Further, the frequency signal branch of the power system controller is closed, specifically:

[0027] the first time constant and the second time constant of the reset filter in the frequency signal branch of the power system controller are adjusted to 0;

[0028] the frequency signal branch of the power system controller is restored, specifically:

[0029] the first time constant and the second time constant of the reset filter in the frequency signal branch of the power system controller are adjusted to the original first time constant and the original second time constant before the DC power transmission system island conversion.

[0030] Further, the output amplitude of the power system controller is reduced by a preset ratio, specifically:

[0031] the upper limit of the output amplitude of the power system controller is reduced to an adjusted upper limit by a preset ratio, and the lower limit of the output amplitude of the power system controller is increased to an adjusted lower limit by a preset ratio;

[0032] the output amplitude of the power system controller is restored, specifically:

[0033] the upper limit of the output amplitude of the power system controller is increased from the adjusted upper limit to the original upper limit, and the lower limit of the output amplitude of the power system controller is increased from the adjusted lower limit to the original lower limit.

[0034] Further, the preset ratio is 5%, 3% or 2%.

[0035] In a third aspect, the present application further provides a computer readable storage medium, which stores a computer program, and the computer program is executed by a processor to implement the steps of the voltage control method for DC power transmission system island conversion according to any one of the first aspect.

[0036] In a fourth aspect, the present application further provides a computer device, which comprises a memory and a processor, and the memory stores a computer program, and the processor executes the computer program to execute the voltage control method for DC power transmission system island conversion according to any one of the first aspect.

[0037] The beneficial effects of the above technical solution are as follows: the embodiment divides island conversion in the DC power transmission system into active island conversion and passive island conversion, adjusts the reset filter of the power system stabilizer or the limited amplitude of the output end through specific island conversion scenarios, so that the voltage distortion caused by the frequency signal over-reverse adjustment does not exceed the voltage range of the normal operation of the system, and the high voltage in the island networking conversion process of the system is avoided, and the safety of the equipment is not endangered. BRIEF DESCRIPTION OF DRAWINGS

[0038] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced as follows.

[0039] Figure 1 A voltage control method for island conversion of a DC power transmission system in an embodiment of the present application;

[0040] Figure 2a A networking mode of a DC power transmission system in an embodiment of the present application;

[0041] Figure 2b A island mode of a DC power transmission system in an embodiment of the present application;

[0042] Figure 3 A island mode of a DC power transmission system containing an internal isolated power grid and an external large power grid in an embodiment of the present application;

[0043] Figure 4 A logic framework of a power system controller in an embodiment of the present application. DETAILED DESCRIPTION

[0044] The technical solutions in the embodiments of the present application will be described clearly and completely in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the protection scope of the present application. In order to more specifically describe the present application, the voltage control method and device for island conversion of a DC power transmission system provided by the present application will be described in detail in combination with the drawings.

[0045] Unless otherwise defined, technical terms or scientific terms used in the present disclosure shall have the same meaning as those commonly understood by one of ordinary skill in the art to which the present disclosure belongs. The terms "first", "second", and similar terms are used herein to distinguish one element from another, and are not necessarily used in a sequence or to denote importance. Similarly, the terms "a", "an", or "the" are not limited, whether or not preceded by the term "one", to mean only one. The terms "comprises", "comprising", "includes", "including" and the like can mean the presence of one or more elements or components, but do not preclude the presence of other elements or components. The terms "connected", "coupled", or the like, unless otherwise defined, are to be construed as including a physical or mechanical coupling of one component to another component or associating the one component with another component, whether directly or indirectly. The terms "upper", "lower", "left", "right", and the like are used for description only and are not to be construed as limiting the position of the described objects.

[0046] The application scenario of the voltage control method for DC power transmission system island conversion is provided, and the application scenario includes a terminal device provided by the embodiments. The terminal device includes, but is not limited to, a smart phone and a computer device. The computer device can be at least one of a desktop computer, a portable computer, a laptop computer, a mainframe computer, a tablet computer, and the like. The frequency input to the power system controller is detected to determine whether the frequency is greater than a set threshold value, the mode of DC island conversion is determined, and the specific parameters of the power system controller are adjusted to control the output voltage. The voltage control method for DC power transmission system island conversion is shown in the accompanying drawings, and the specific process is described in the embodiments of the voltage control method for DC power transmission system island conversion. Figure 1 The voltage control method for DC power transmission system island conversion is shown in the accompanying drawings, and the specific process is described in the embodiments of the voltage control method for DC power transmission system island conversion.

[0047] The DC power transmission system operating mode includes two modes, namely, a networking operating mode and an island operating mode. The networking operating mode is shown in the accompanying drawings, and the specific process is described in the embodiments of the voltage control method for DC power transmission system island conversion. Figure 2a The networking operating mode is an operating mode in which the two converter stations are in networking operation with the main grid. The island operating mode is shown in the accompanying drawings, and the specific process is described in the embodiments of the voltage control method for DC power transmission system island conversion. Figure 2b The island operating mode is an operating mode in which the converter station forms an independent small system with the nearby station and line, and is disconnected from the main grid AC connection. The disconnection mode of the tie line is shown in the accompanying drawings, and the specific process is described in the embodiments of the voltage control method for DC power transmission system island conversion.

[0048] Island operation mode is a relatively independent island system formed by the sending end of the DC system and several power plants, that is, the DC transmission system is not connected to the main grid AC system, and the power is directly sent to the receiving end through the DC system. The island operation mode can effectively reduce the impact of DC system failure on the main grid and improve the safety and stability of the grid. Since the DC island system refers to an independent power supply system that is not electrically connected to the main AC grid and is interconnected with the external grid only through the DC line, such as offshore wind power platforms, remote islands or energy bases; its voltage stability is the core of safe operation of the system, and power balance and voltage constancy need to be achieved through coordinated control. The common situation of the DC transmission system changing from the interconnected operation mode to the island operation mode is that the tie line between the DC and the main grid is disconnected, and the DC enters the island operation mode.

[0049] The rotational inertia of the island system is small, and the frequency or voltage fluctuation distance under disturbance, so the output fluctuation or composite mutation is easy to cause the DC bus voltage instability. The DC bus voltage is a barometer of system power balance, and DC bus voltage instability will trigger a chain reaction, such as overvoltage triggering arrester or blocking converter, leading to power interruption. When the voltage fluctuation of the DC island system containing new energy exceeds the tolerance range of the inverter, the wind power / photovoltaic unit automatically disconnects from the grid. The negative damping characteristic may excite shaft torsional vibration, threatening the safety of the generator.

[0050] The current conventional hydropower station adopts PSS power system stabilizer type 2B. The 2B type power system stabilizer adopts double input mode, through the double signal input of speed deviation and electromagnetic power deviation, to avoid the "anti-adjustment phenomenon" caused by single signal. In fact, PSS2B adjusts the internal potential of the excitation system, thereby adjusting the active power output of the generator, to enhance the damping ratio of the system and suppress low-frequency oscillation. The core is to use the small change of generator speed or power to generate a control signal, and then affect the excitation current. The existing PSS2B type power system stabilizer shows good low-frequency oscillation suppression ability in island system water and fire power unit, especially in the medium and low frequency band. After reasonable parameter setting, the PSS power system stabilizer can adapt to most system operation conditions, but in the DC sending end island system, if the tie line power is sent out, that is, the power is sent out from the island system to the near area AC network, in the process of interconnected island conversion, the DC loop bus voltage and the power station bus voltage all appear voltage distortion, and in serious cases, the transient voltage exceeds the normal operation range.

[0051] It should be noted that the 2B-type power system stabilizer involved in this application, also known as an accelerated power type power system stabilizer, is a widely used dual-input power system stabilizer. Its core principle is to modulate the generator's excitation voltage by introducing an additional signal related to the generator's active power and speed / frequency, thereby providing positive damping torque when low-frequency oscillations occur in the power system, suppressing oscillations, and enhancing system stability. The control objective of the 2B-type power system stabilizer is to suppress low-frequency oscillations in the power system (typically between 0.1Hz and 2.0Hz). The principle is that when the system oscillates, the generator speed and active power deviate from their steady-state values ​​and exhibit oscillating characteristics. The 2B-type power system stabilizer detects these oscillation signals, processes them, and generates an additional control signal, which is superimposed on the reference voltage of the generator's automatic voltage regulator. This additional signal generates an additional electromagnetic torque that is in phase with the oscillating speed deviation. This in-phase additional torque acts as a damper, consuming oscillation energy and causing the oscillation to subside quickly.

[0052] Combined with appendix Figure 4 The diagram shows the transfer function framework of the power system controller. As an additional control within the unit's excitation system, the power system controller suppresses oscillations by assisting the automatic voltage regulator. The 2B-type power system controller in this embodiment sequentially includes a reset filter, a lag filter, a stress tracking filter, and a lead / lag sway compensation section. Among these, the attached... Figure 4 middle , , , This represents the time constant of the reset filter section. , , Indicates the gain coefficient. , , , , , These are the filter parameters. , The phase compensation parameters are for the lead-lag slewing reduction compensation stage. , The time constant of the output filter. The maximum value of the output signal. This is the minimum value of the output signal.

[0053] in, This indicates the frequency input, typically the generator frequency, generator speed deviation, or system frequency deviation. This is the most direct signal reflecting system oscillation. For power input, generally the generator power or generator active power deviation, this signal responds quickly to system power changes. In In the input power system stabilizer, when the system load changes continuously and slowly (non-oscillatory), as the system frequency becomes higher, The signal will become larger, causing the power system stabilizer to output unnecessary signals (which can be referred to as anti-regulation) affecting the generator voltage regulation. The introduction of active power The signal helps to distinguish between oscillations and continuous load changes. The signal responds faster to power disturbances than The combination of the two can provide more accurate and timely damping control signals. The signal provides an absolute reference for oscillation (relative to the rated speed), while The signal provides information directly related to system power flow. The combination of the two (usually some form of difference or weighted sum) can more effectively represent the energy exchange process that causes oscillation.

[0054] Based on this, the voltage control method for DC power transmission system island conversion of the embodiment includes the following specific steps:

[0055] Step S101, if the frequency input to the power system controller is greater than the preset threshold, determine the mode of DC island conversion.

[0056] During the process of DC networking to island, the frequency changes greatly, that is, the frequency input to the power system controller is greater than the preset threshold, The signal input end changes temporarily dominant, causing the power system controller output The power system controller output In serious cases, directly against the output limit of the power system controller, directly Superimposed on the generator terminal voltage Causing the generator terminal voltage to appear anti-regulation type voltage rise, exceeding the normal range of system operation, in severe cases, exceeding the normal operating value of the corresponding voltage level bus voltage, even reaching the voltage value boundary of the safe operation of the microcomputer equipment. The existing power system stabilizer in the running state needs to take necessary measures for optimization to avoid the voltage of the system during the island networking conversion process. Abnormally high, endangering the safety of the equipment.

[0057] Step S102, if the DC island conversion is active island conversion, the frequency signal branch of the power system controller is closed, while the power signal branch of the power system controller is effective, and after the DC power transmission system enters the DC island state, the frequency signal branch of the power system controller is restored. Effective.

[0058] The frequency signal branch of the power system controller is closed, specifically as follows:

[0059] The first time constant and the second time constant of the reset filter in the frequency signal branch of the power system controller are adjusted to 0;

[0060] The frequency signal branch of the power system controller is recovered, specifically as follows:

[0061] The first time constant and the second time constant of the reset filter in the frequency signal branch of the power system controller are adjusted to the original first time constant and the original second time constant before the DC power transmission system island conversion.

[0062] When the conversion mode of the DC island conversion belongs to the active island networking and island mode conversion (i.e., the dispatch department actively arranges the networking island conversion operation, collectively referred to as active island conversion), when the system is about to carry out the networking island conversion, the first time constant or the second time constant of the reset filter part of the signal branch of the operating unit power system controller can be modified to a value close to 0, approximately closing the channel; at the same time the signal input channel is still effective, and after the networking island conversion is completed and the system enters the island state from the networking state, the and can be restored to the original value.

[0063] In step S103, if the DC island conversion is passive conversion and the island signal at the output end of the power system controller is true, the output end amplitude of the power system controller is reduced by a preset proportion, and after the DC power transmission system enters the DC island state, the output end amplitude of the power system controller is restored.

[0064] The output end amplitude of the power system controller is reduced by a preset proportion, specifically as follows:

[0065] The upper limit of the output end amplitude of the power system controller is reduced to an adjusted upper limit of the amplitude by a preset proportion, and the lower limit of the output end amplitude of the power system controller is increased to an adjusted lower limit of the amplitude by a preset proportion;

[0066] The output end amplitude of the power system controller is recovered, specifically as follows:

[0067] The upper limit of the output end amplitude of the power system controller is increased from the adjusted upper limit of the amplitude to the original upper limit of the amplitude, and the lower limit of the output end amplitude of the power system controller is increased from the adjusted lower limit of the amplitude to the original lower limit of the amplitude.

[0068] The above-mentioned preset proportion is 5%, 3% or 2%.​

[0069] When the conversion mode of the direct current island conversion belongs to the passive island condition processing (i.e. the system is in the passive networking state and is converted into the island state due to a fault), it is necessary to prevent passive jumping into the island under unknown conditions. The method that can be processed is that when the original island signal is true at the output end of the power system controller, the amplitude is limited to 5% of the original value, and the 5% amplitude is adjusted to a smaller 2% or 3%. The specific adjustment size can be obtained by simulation technology to obtain a suitable And The voltage distortion in the networking island conversion process is ensured to be within the normal operating voltage range of the system. After the networking island conversion ends and enters the stable island state, the power system controller output amplitude adjustment is adjusted to 5%. And The networking island conversion process is ensured to be within the normal operating voltage range of the system. After the networking island conversion ends and enters the stable island state, the power system controller output amplitude adjustment is adjusted to 5%.

[0070] The embodiment adopts the original power system controller parameters in the networking and island stable operation processes, but in the networking island conversion process, in order to realize smooth switching of the networking island system, effectively solve the problem of sudden rise of the terminal voltage due to over-reverse adjustment in the networking island conversion process, endangering the safety of equipment, quickly suppress the system voltage fluctuation, and more effectively ensure the stability of the direct current island operation mode.

[0071] It should be understood that, although the steps in the flowchart of the accompanying drawings are shown in sequence according to the arrows, these steps are not necessarily executed in sequence according to the arrows. Unless otherwise specified in this article, the execution of these steps is not strictly limited in sequence, and these steps can be executed in other sequences. Moreover, at least part of the steps in the accompanying drawings Figure 1 may include multiple sub-steps or sub-stages, which are not necessarily executed at the same time, but can be executed at different times, and the execution sequence of these sub-steps or stages is not necessarily sequential, but can be alternately executed with other steps or at least part of the sub-steps or stages of other steps. Figure 1 The voltage control method of the direct current power transmission system island conversion is described in detail in the above embodiments disclosed by the present application. The above method disclosed by the present application can be implemented by various forms of equipment, and therefore the present application also discloses a voltage control device for direct current power transmission system island conversion. The following specific embodiments are given to explain in detail.

[0072] The frequency over-reverse adjustment module is used to determine the mode of the direct current island conversion if the frequency input to the power system controller is greater than a preset threshold value.

[0073]

[0074] ​The first voltage control module is configured to, if the DC island conversion is active island conversion, perform closed processing on a frequency signal branch of the power system controller while keeping a power signal branch of the power system controller effective, and restore the frequency signal branch of the power system controller to be effective after the DC power transmission system enters the DC island state.

[0075] The second voltage control module is configured to, if the DC island conversion is passive conversion and an island signal at an output end of the power system controller is true, reduce an output end amplitude of the power system controller by a preset proportion, and restore the output end amplitude of the power system controller after the DC power transmission system enters the DC island state.

[0076] Further, the closed processing on the frequency signal branch of the power system controller is specifically:

[0077] The first time constant and the second time constant of a reset filter in the frequency signal branch of the power system controller are adjusted to 0.

[0078] The restoring of the frequency signal branch of the power system controller to be effective is specifically:

[0079] The first time constant and the second time constant of the reset filter in the frequency signal branch of the power system controller are adjusted to original first time constant and original second time constant before the DC power transmission system island conversion.

[0080] Further, the reducing of the output end amplitude of the power system controller by the preset proportion is specifically:

[0081] The upper limit of the output end amplitude of the power system controller is reduced to an adjusted upper limit of amplitude by the preset proportion, and the lower limit of the output end amplitude of the power system controller is increased to an adjusted lower limit of amplitude by the preset proportion.

[0082] The restoring of the output end amplitude of the power system controller is specifically:

[0083] The upper limit of the output end amplitude of the power system controller is increased from the adjusted upper limit of amplitude to an original upper limit of amplitude, and the lower limit of the output end amplitude of the power system controller is increased from the adjusted lower limit of amplitude to an original lower limit of amplitude.

[0084] The preset proportion is 5%, 3% or 2%.

[0085] The voltage control device for island conversion of a DC power transmission system can refer to the above description of the method, and will not be repeated here. Each module in the above device can be implemented by software, hardware, or a combination thereof. The above modules can be embedded in or independent of the processor of the terminal device in hardware form, or stored in the memory of the terminal device in software form, so that the processor invokes and executes the operations corresponding to each of the above modules.

[0086] In one embodiment, the present application also provides a computer-readable storage medium having a computer program stored thereon, wherein the computer program is executed by a processor to implement the steps of the above-mentioned voltage control method for island conversion of a DC power transmission system.

[0087] The computer-readable storage medium can be an electronic storage such as a flash memory, an EEPROM (Electrically Erasable Programmable Read-Only Memory), an EPROM (Erasable Programmable Read-Only Memory), a hard disk, or a ROM. Alternatively, the computer-readable storage medium includes a non-transitory computer-readable storage medium. The computer-readable storage medium has a storage space for program codes for executing any of the above-mentioned method steps. These program codes can be read from or written into one or more computer program products, and can be compressed in an appropriate form.

[0088] In one embodiment, the present application provides a computer device comprising a memory and a processor, wherein the memory stores a computer program, and the processor executes the computer program to execute the above-mentioned voltage control method for island conversion of a DC power transmission system.

[0089] The computer device comprises a memory, a processor, and one or more computer programs, wherein the one or more computer programs can be stored in the memory and configured to be executed by the one or more processors, and the one or more application programs are configured to execute the above-mentioned voltage control method for island conversion of a DC power transmission system.

[0090] The processor can include one or more processing cores. The processor connects various parts within the entire computer device by various interfaces and lines, performs various functions of the computer device and processes data by running or executing instructions, programs, code sets or instruction sets stored in the memory, and calling data stored in the memory. Optionally, the processor can be implemented in at least one of a hardware form of digital signal processing (DSP), field-programmable gate array (FPGA), programmable logic array (PLA). The processor can integrate a combination of one or several of central processing unit (CPU), graphics processing unit (GPU) and modem. Among them, the CPU mainly processes operating systems, user interfaces and application programs, etc.; the GPU is responsible for rendering and drawing display content; and the modem is used for processing wireless communication. It can be understood that the above-mentioned modem can also not be integrated into the processor, but be realized by a separate communication chip.

[0091] The memory can include random access memory (RAM) and can also include read-only memory (ROM). The memory can be used to store instructions, programs, codes, code sets or instruction sets. The memory can include a program storage area and a data storage area, wherein the program storage area can store instructions for implementing an operating system, instructions for implementing at least one function (such as a touch function, a sound playing function, an image playing function, etc.), instructions for implementing the above-mentioned various method embodiments, etc. The data storage area can also store data created by the terminal device in use, etc.

[0092] The above embodiments are only used to illustrate the technical solutions of the present application, but not limit it; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for part of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A voltage control method for islanding conversion of a direct current power transmission system, the voltage control method being applied to a power system stabilizer of the direct current power transmission system, characterized by, The method comprises the following steps: If the frequency input to the power system controller is greater than a preset threshold, the mode of DC island conversion is determined; If the DC island conversion is active island conversion, the frequency signal branch of the power system controller is closed, the power signal branch of the power system controller is kept effective, and after the DC power transmission system enters the DC island state, the frequency signal branch of the power system controller is restored to be effective; If the DC island conversion is passive conversion and the island signal at the output end of the power system controller is true, the output end amplitude of the power system controller is reduced by a preset proportion, and after the DC power transmission system enters the DC island state, the output end amplitude of the power system controller is restored.

2. The voltage control method for DC power transmission system island transition according to Claim 1, wherein The closing processing of the frequency signal branch of the power system controller is specifically: The first time constant and the second time constant of the reset filter in the frequency signal branch of the power system controller are adjusted to 0; The restoration of the frequency signal branch of the power system controller is effective, specifically: The first time constant and the second time constant of the reset filter in the frequency signal branch of the power system controller are adjusted to the original first time constant and the original second time constant before the DC power transmission system island conversion.

3. The voltage control method for DC power transmission system island conversion according to Claim 1, wherein The reduction of the output end amplitude of the power system controller by a preset proportion is specifically: The upper limit of the output end amplitude of the power system controller is reduced to an adjusted upper limit by a preset proportion, and the lower limit of the output end amplitude of the power system controller is increased to an adjusted lower limit by a preset proportion; The restoration of the output end amplitude of the power system controller is specifically: The upper limit of the output end amplitude of the power system controller is increased from the adjusted upper limit to the original upper limit, and the lower limit of the output end amplitude of the power system controller is increased from the adjusted lower limit to the original lower limit.

4. The voltage control method for islanding conversion of a DC power transmission system according to claim 3, wherein The preset proportion is 5%, 3% or 2%.

5. A voltage control device for islanding conversion of a direct current power transmission system, the voltage control device being applied to a power system stabilizer of the direct current power transmission system, characterized by, The method comprises the following steps: The frequency over-reverse adjustment module is used to determine the mode of DC island conversion if the frequency input to the power system controller is greater than a preset threshold; The first voltage control module is used to close the frequency signal branch of the power system controller if the DC island conversion is active island conversion, keep the power signal branch of the power system controller effective, and restore the frequency signal branch of the power system controller to be effective after the DC power transmission system enters the DC island state; The second voltage control module is used to reduce the output end amplitude of the power system controller by a preset proportion if the DC island conversion is passive conversion and the island signal at the output end of the power system controller is true, and restore the output end amplitude of the power system controller after the DC power transmission system enters the DC island state.

6. The voltage control apparatus for DC power transmission system island transition according to Claim 5, wherein The closing processing of the frequency signal branch of the power system controller is specifically: The first time constant and the second time constant of the reset filter in the frequency signal branch of the power system controller are adjusted to 0; The restoration of the frequency signal branch of the power system controller is effective, specifically: The first time constant and the second time constant of the reset filter in the frequency signal branch of the power system controller are adjusted to the original first time constant and the original second time constant before the DC power transmission system island conversion. The first time constant and the second time constant of the reset filter in the frequency signal branch of the power system controller are adjusted to original first time constant and original second time constant before island conversion of the HVDC system.

7. The voltage control apparatus for DC power transmission system island conversion according to Claim 5, wherein The output amplitude of the power system controller is reduced by a preset ratio, and the specific method is: The upper limit of the output amplitude of the power system controller is reduced to an adjusted upper limit of the amplitude by a preset ratio, and the lower limit of the output amplitude of the power system controller is increased to an adjusted lower limit of the amplitude by a preset ratio. The output amplitude of the power system controller is recovered, and the specific method is: The upper limit of the output amplitude of the power system controller is increased from the adjusted upper limit of the amplitude to the original upper limit of the amplitude, and the lower limit of the output amplitude of the power system controller is increased from the adjusted lower limit of the amplitude to the original lower limit of the amplitude.

8. The voltage control device for DC power transmission system island transition according to claim 7, wherein The preset ratio is 5%, 3% or 2%.

9. A computer-readable storage medium having stored thereon a computer program, characterized in that, The computer program is executed by the processor to realize the steps of the voltage control method for island conversion of the HVDC system in any one of claims 1-4. 10.A computer device, comprising a memory and a processor, wherein the memory stores a computer program, and the computer device is configured to perform the method according to any one of claims 1-9. The processor executes the computer program to execute the voltage control method for island conversion of the HVDC system in any one of claims 1-4.

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