Low-voltage ride-through and recovery method and related device for network-forming type current converter

Abstract

The invention discloses a low-voltage ride-through and recovery method and a related device for a grid-forming converter, and relates to the technical field of power electronics, and the method comprises the following steps: sampling the actual current of a power grid, and obtaining a virtual impedance value through combining a reactive current injection reference value and an active current injection reference value, determining a voltage drop value correspondingly generated by the virtual impedance value and then obtaining a voltage amplitude compensation amount; correcting the voltage amplitude instruction after primary correction according to the voltage amplitude compensation amount to obtain a voltage amplitude instruction after secondary correction; and controlling the low-voltage ride-through of the network-building type converter through the corrected angular frequency instruction and the secondarily corrected voltage amplitude instruction, and after a fault recovery instruction is detected, smoothly correcting the virtual impedance value and the power ring reference value, and controlling the network-building type converter to smoothly exit the fault ride-through state. According to the method, the problem of how to avoid current impact of the network-forming type converter in the power grid voltage drop fault and fault recovery process can be solved.

Description

Technical Field

[0001] The present invention relates to the technical field of power electronics, and in particular to a low voltage ride-through and recovery method of a grid-type converter and a related device. Background Art

[0002] At present, the low-carbon transformation of energy has been significantly accelerated. The energy transformation mainly relies on expanding the proportion of clean energy, low-carbon energy, and zero-carbon energy, and promoting the realization of energy production and consumption centered on electricity. It is an inevitable trend for new energy to replace traditional energy. As the main body, new energy power generation should have the corresponding characteristics of synchronous machines and assume the support and support role of the power grid. The rapid development of new energy construction forces the power grid to achieve efficient energy interaction with it. In the power system with high penetration rate of new energy, as the proportion of power electronic converters in the power system continues to increase, the traditional power grid dominated by synchronous generators is changing. The corresponding increase in the proportion of converters in the power system makes the current new power system (i.e., microgrid system) present the "double high" characteristics of high proportion of renewable energy and high proportion of power electronic equipment, the system inertia is greatly reduced, the system frequency index is deteriorated, and the power grid lacks inertial support, which makes the voltage and frequency stability of the new power system face challenges. The grid-type control technology does not rely on the phase-locked loop to synchronize with the power grid, and can provide voltage support for the large power grid throughout the process, solve the stability problems of voltage and frequency of the new power system, and realize active perception, active response and active support of the power grid.

[0003] like Figure 2 As shown in the figure, since the grid-connected inverter has the inherent characteristics of a voltage source, its output voltage is not affected by grid faults. Therefore, after a grid fault occurs, the output current of the grid-connected inverter will increase rapidly, thereby triggering overcurrent protection and causing the new energy generator set to be disconnected from the grid. In severe cases, the entire system will collapse, endangering the stable operation of the system. In order to improve the stability of the new power system with new energy as the main body, when a short-term fault occurs in the grid, the new energy generator set must remain connected to the grid. Therefore, when a grid fault occurs, the fault current of the grid-connected inverter must be limited to ensure that the new energy unit does not run off the grid. In addition, the grid-connected inverter should have low voltage ride-through capability, that is, the grid-connected inverter needs to inject a certain amount of reactive current into the grid within 30ms after the grid voltage drops suddenly to help the grid recover. However, due to the narrow bandwidth and slow response speed of the power outer loop of the grid-connected inverter, the reactive current regulation speed of the grid-connected inverter is slow, which may lead to low voltage ride-through failure. Therefore, the grid-connected inverter's ability to limit fault current and quickly inject reactive current during grid faults has become the key to the reliable operation of new power systems based on new energy.

[0004] The grid-type inverter in the microgrid can build voltage and frequency autonomously. When the grid voltage drops, the grid-type inverter will automatically inject a large current when it is connected to the grid, causing the power quality to deteriorate, damaging fragile equipment, and even causing it to go offline. At the same time, when the grid drops, the grid-type inverter needs to inject reactive current into the grid according to the degree of grid drop to help the grid recover. Therefore, how to avoid the current shock and rapid reactive injection of the grid-type inverter under the grid voltage drop fault needs to be solved urgently. Summary of the invention

[0005] The object of the present invention is to provide a low voltage ride through and recovery method and related device for a grid-type converter, so as to solve the problem of how to avoid current shock in the grid-type converter during a grid voltage drop fault and fault recovery process.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions: In a first aspect, a low voltage ride-through and recovery method for a grid-type converter comprises the following steps: Obtaining a reactive current injection reference value and an active current injection reference value of a grid-type converter, and calculating a power loop reference value of a droop control power loop low voltage ride-through based on the reactive current injection reference value and calculating a corrected angular frequency command and a corrected voltage amplitude command based on the power loop reference value; and correcting an angular frequency command and a corrected voltage amplitude command of the grid-type converter according to the power loop reference value. Sampling the actual current of the power grid, and obtaining a virtual impedance value by combining the reactive current injection reference value and the active current injection reference value, and obtaining a voltage amplitude compensation amount after determining a voltage drop value corresponding to the virtual impedance value; Correcting the primary corrected voltage amplitude instruction according to the voltage amplitude compensation amount to obtain a secondary corrected voltage amplitude instruction; Controlling the low voltage ride-through of the grid-type converter by means of the corrected angular frequency command and the second corrected voltage amplitude command; After the fault recovery instruction is detected, the virtual impedance value and the power loop reference value are smoothly corrected to control the grid-type converter to smoothly exit the fault ride-through state.

[0007] In some implementations, the power loop reference value includes: a reactive power reference value and an active power reference value, and the virtual impedance value includes: a virtual resistance given value and a virtual inductance given value.

[0008] In some implementations, the step of obtaining a reactive current injection reference value and an active current injection reference value of the grid-type converter specifically includes: Obtain the grid voltage and perform coordinate transformation to obtain the direct-axis voltage and quadrature-axis voltage; Comparing the nominal voltage of the power grid with the direct-axis voltage to obtain a power grid voltage drop level; According to the grid voltage drop level and the quadrature-axis current corresponding to the quadrature-axis voltage, reactive compensation calculation is performed to obtain a reactive current injection reference value of the grid-type converter; The remaining capacity of the power grid is obtained, and a difference theoretical calculation is performed on the remaining capacity and a reactive current injection reference value to obtain an active current injection reference value.

[0009] In some implementations, the step of calculating the power loop reference value during the droop control power loop low voltage ride-through period specifically includes: According to the reactive current injection reference value and the active current injection reference value, and in combination with the direct-axis voltage and the quadrature-axis voltage, instantaneous power calculation is performed to obtain the reactive power reference value and the active power reference value of the low voltage ride-through of the droop control power loop.

[0010] In some embodiments, the step of sampling the actual current of the power grid, obtaining a virtual impedance value by combining the reactive current injection reference value and the active current injection reference value, and obtaining a voltage amplitude compensation amount after determining a voltage drop value corresponding to the virtual impedance value specifically includes: Sampling the actual current of the power grid to obtain a current sampling value, and performing coordinate transformation on the current sampling value to obtain a direct-axis sampling current and a quadrature-axis sampling current; After making a difference comparison between the active current injection reference value and the direct axis sampling current, proportional integral adjustment is performed to obtain a virtual resistance given value; After making a difference comparison between the reactive current injection reference value and the quadrature axis sampling current, a proportional integral adjustment is performed to obtain a virtual inductance given value; According to the virtual resistance given value and the direct-axis sampling current, a direct-axis voltage compensation amount is obtained, and according to the virtual inductance given value and the quadrature-axis sampling current, a quadrature-axis voltage compensation amount is obtained. The direct-axis voltage compensation amount and the quadrature-axis voltage compensation amount constitute the voltage amplitude compensation amount.

[0011] In some implementations, after the fault recovery instruction is detected, the step of smoothly correcting the virtual impedance value and the power loop reference value to control the grid-type converter to smoothly exit the fault ride-through state specifically includes: Performing exponential decay calculation on the virtual impedance value to obtain a real-time exit value of the virtual impedance; The active power output value at the time of detecting the fault recovery instruction is sampled and maintained, and the active power reference value under the normal bypass operation state is used as the calculation end point, and a smoothing exponential increase calculation is performed to obtain a real-time exit value of the active power reference value; The reactive power output value at the time of detecting the fault recovery instruction is sampled and maintained, and the reactive power reference value under the normal bypass operation state is used as the calculation end point, and a smooth exponential decay calculation is performed to obtain a real-time exit value of the reactive power reference value; According to the real-time exit value of the virtual impedance, the real-time exit value of the active power reference value and the real-time exit value of the reactive power reference value, the grid-type converter is controlled to smoothly exit the fault ride-through state.

[0012] In a second aspect, a low voltage ride through and recovery system of a grid-type converter includes: A droop control power loop correction module is used to obtain a reactive current injection reference value and an active current injection reference value of a grid-type converter, and calculate a power loop reference value of a low voltage ride-through of a droop control power loop based on the obtained value, and correct an angular frequency command and a voltage amplitude command of the grid-type converter according to the power loop reference value to obtain a corrected angular frequency command and a corrected voltage amplitude command; A compensation amount determination module is used to sample the actual current of the power grid, and obtain a virtual impedance value by combining the reactive current injection reference value and the active current injection reference value, and obtain a voltage amplitude compensation amount after determining the voltage drop value corresponding to the virtual impedance value; A secondary correction module, used for correcting the voltage amplitude instruction after the primary correction according to the voltage amplitude compensation amount to obtain a voltage amplitude instruction after the secondary correction; A ride-through control module, used to control the low voltage ride-through of the grid-type converter through the corrected angular frequency instruction and the second corrected voltage amplitude instruction; The fault recovery module is used to smoothly correct the virtual impedance value and the power loop reference value after detecting the fault recovery instruction, and control the grid-type converter to smoothly exit the fault ride-through state.

[0013] In a third aspect, a computer device comprises a memory, a processor, and a computer program stored in the memory and executable in the processor, wherein the processor implements the steps of a low voltage ride-through and recovery method of a grid-type converter when executing the computer program.

[0014] In a fourth aspect, a computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the steps of the low voltage ride-through and recovery method of the grid-type converter are implemented.

[0015] In a fifth aspect, a computer program product is provided, the computer product comprising a computer program, and the computer program, when executed by a processor, implements the steps of the low voltage ride-through and recovery method of the grid-type converter.

[0016] Compared with the prior art, the present invention has the following beneficial effects: The low voltage ride-through and recovery method of the grid-type converter provided by the present invention controls the low voltage ride-through of the grid-type converter through the corrected angular frequency instruction and the secondary corrected voltage amplitude instruction, and after detecting the fault recovery instruction, smoothly corrects the virtual impedance value and the power loop reference value to control the grid-type converter to smoothly exit the fault ride-through state, which can avoid the impact current caused by the grid-type converter in the case of grid voltage drop and fault recovery, and solve the problem of reactive power support demand.

[0017] Furthermore, in the present invention, when the grid-type converter enters the droop control state and starts low voltage riding, it is assumed that there is a virtual impedance between the low voltage control point where the grid-type converter is located and the AC bus, and the reactive current injection reference value and the active current injection reference value of the grid-type converter are determined according to the grid voltage drop level and the remaining capacity; a virtual impedance value is obtained according to the reactive current injection reference value and the active current injection reference value to obtain a voltage amplitude compensation amount to correct the voltage amplitude instruction, and the grid-type converter is controlled to ride through the low voltage in conjunction with the angular frequency instruction; after detecting the fault recovery instruction, the power reference value, the active power reference value and the virtual impedance value are smoothly corrected to control the grid-type converter to smoothly exit the fault riding state, so that the grid-type converter can provide reactive support to the grid during the low voltage process while ensuring a certain degree of active output, thereby avoiding the technical problems of impact current and reactive support requirements caused by the grid-type converter under the condition of grid voltage drop and fault recovery, and improving the reliability of the low voltage riding of the grid-type converter.

[0018] Furthermore, the present invention samples the grid current in real time, combines the reactive current injection reference value and the active current injection reference value, and dynamically adjusts the virtual impedance value, thereby realizing accurate compensation of the voltage amplitude. This helps the converter maintain a stable output during a grid fault and avoids equipment damage caused by current surge or rapid reactive injection. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 A schematic flow chart of a low voltage ride-through and recovery method for a grid-type converter provided in an embodiment of the present invention; Figure 2 A partial circuit schematic diagram of a microgrid system according to an embodiment of the present invention; Figure 3 A main circuit topology diagram of a low voltage ride-through and fault recovery control strategy provided by an embodiment of the present invention; Figure 4 An equivalent circuit diagram of introducing virtual impedance provided by an embodiment of the present invention; Figure 5A block diagram of voltage and current dual closed-loop control with virtual impedance provided by an embodiment of the present invention; Figure 6 A structural diagram of a low voltage ride-through and recovery system for a grid-type converter provided in an embodiment of the present invention; Figure 7 It is a schematic diagram of the structure of computer equipment involved in the low voltage ride-through and recovery method of the grid-type converter in the embodiment of the present invention. DETAILED DESCRIPTION

[0020] In order to enable those skilled in the art to better understand the solution of the present invention, the technical solution of the present invention will be further described in detail below in conjunction with the accompanying drawings, and the described content is intended to explain the present invention rather than to limit it.

[0021] It should be noted that the terms "including" and "having" and any variations thereof in the specification and claims of the present invention are intended to cover non-exclusive inclusions. For example, a process, method, system, product or apparatus comprising a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units that are not explicitly listed or are inherent to these processes, methods, systems, products or apparatus.

[0022] like Figure 1 As shown, this embodiment provides a low voltage ride-through and recovery method for a grid-type converter, comprising the following steps: S100, when the grid-type converter in the microgrid system enters a droop control state, a reactive current injection reference value is calculated according to a real-time monitored grid voltage drop level; When the grid voltage drops, Figure 3 As shown, the grid-connected point voltage corresponding to the grid-connected converter is u pcc With nominal bus voltage u gN There will be a voltage difference between the two. If the grid voltage drop level is defined k , then the grid voltage drop level k The calculation process is as follows formula (1): (1) In order to provide reactive support to the grid, the grid-connected converter needs to inject reactive current into the grid. The reactive current injection reference value calculation process of low voltage ride-through is as follows: (2) in, Reactive current injection reference value for low voltage ride through, It is the nominal current of normal operation.

[0023] S200, calculating the active current injection reference value according to the remaining capacity and the reactive current injection reference value, specifically by the following formula (3): (3) in, Active current injection reference value for low voltage ride through, .

[0024] S300, according to the reactive current injection reference value and the active current injection reference value, calculate the reactive power reference value and the active power reference value of the droop control power loop during low voltage ride-through, and calculate by the following formula (4).

[0025] (4) in, is the grid connection point voltage.

[0026] S400, by using the reactive power reference value and the active power reference value, the angular frequency command and the voltage amplitude command of the grid-type converter during low voltage ride-through are corrected to obtain a corrected angular frequency command and a corrected voltage amplitude command, which are calculated by the following formula (5): (5) in, is the corrected angular frequency instruction, is the voltage amplitude instruction after correction, is the rated angular frequency of the grid-type converter, is the rated voltage amplitude of the grid-type converter, is the active power droop coefficient, P is the actual active power output by the grid-type converter, is the active power reference value of low voltage ride through of grid-type converter, is the reactive power droop coefficient, Q is the actual reactive power output by the grid-type converter, It is the reactive power reference value of low voltage ride through of grid-type converter.

[0027] S500, sampling the actual current of the power grid to obtain a current sampling value, and combining the reactive current injection reference value and the active current injection reference value to obtain a virtual resistance given value and a virtual inductance given value, and obtain a voltage amplitude compensation amount; Specifically, step S500 includes: S510, sampling the actual current of the power grid to obtain a current sampling value, and performing coordinate transformation on the current sampling value to obtain a direct-axis sampling current and a quadrature-axis sampling current; It should be noted that in S510, the coordinate transformation may include Parker transformation, and the direct-axis current and the quadrature-axis current are obtained after the coordinate transformation. Specifically, the angular frequency compensation amount can be determined according to the direct-axis current, and the voltage amplitude compensation amount can be determined according to the quadrature-axis current.

[0028] S520, after making a difference comparison between the active current injection reference value and the direct axis sampling current, proportional integral adjustment is performed to obtain a virtual resistance given value, which is calculated by the following formula (6): (6) After comparing the reactive current injection reference value with the quadrature axis sampling current, proportional integral regulation is performed to obtain a virtual inductance given value, which is calculated by the following formula (7): (7) In the above formulas (6) and (7), is the given value of virtual resistance, is the given value of virtual inductance, is the integration coefficient, is the integration coefficient, is the direct axis sampling current, is the quadrature axis sampling current.

[0029] S530, obtaining a direct-axis voltage compensation amount according to the virtual resistance given value and the direct-axis sampling current, and obtaining a quadrature-axis voltage compensation amount according to the virtual inductance given value and the quadrature-axis sampling current, wherein the direct-axis voltage compensation amount and the quadrature-axis voltage compensation amount constitute the voltage amplitude compensation amount, which is specifically implemented by the following formula: (8) in, is the direct axis voltage compensation, is the quadrature axis voltage compensation; like Figure 4 As shown, after the virtual impedance is introduced, the voltage drop generated on the virtual impedance can be obtained by calculating Kirchhoff's law in a two-phase rotating coordinate system, thereby obtaining the voltage amplitude compensation amount of the low voltage ride-through.

[0030] S600, according to the voltage amplitude compensation amount under low voltage ride-through, the voltage amplitude instruction after the primary correction is corrected to obtain the voltage amplitude instruction after the secondary correction, which is calculated by the following formula (9): (9) in, is the voltage loop direct axis reference voltage, is the voltage loop quadrature axis reference voltage, It is the reference value instruction of the output voltage amplitude of the reactive droop power loop.

[0031] S700, controlling the low voltage ride-through of the grid-type converter by using the corrected angular frequency instruction and the second corrected voltage amplitude instruction, such as Figure 5 As shown, in the droop control state, the output voltage and frequency of the grid-type converter in the droop control curve are set to the voltage amplitude instruction after secondary correction and the corrected angular frequency instruction, respectively, and the droop control curve is adjusted to control the grid-type converter to control the low voltage ride-through of the grid-type converter.

[0032] S800, after detecting the fault recovery instruction, the virtual impedance value and the power loop reference value are smoothly corrected to control the grid-type converter to smoothly exit the fault ride-through state; S800 includes: S810, performing exponential decay calculation on the virtual impedance value according to the following formula (10) to obtain a real-time exit value of the virtual impedance; (10) In formula (9) Real-time exit value of virtual resistance for fault recovery process, Real-time exit value of virtual inductance for fault recovery process, is the attenuation coefficient.

[0033] S820, according to the following formula (11), sample and hold the active power output value at the time when the fault recovery instruction is detected, and use the active power reference value in the normal bypass operation state as the calculation end point, perform a smoothing exponential increase calculation, and obtain a real-time exit value of the active power reference value; (11) in, It is the real-time exit value of the active power reference value during the fault recovery process. The sampled active power output value at the time when the fault recovery instruction is detected, It is the active power reference value under normal bypass operation. is the attenuation coefficient.

[0034] S830, according to the following formula (12), sample and hold the reactive power output value at the time when the fault recovery instruction is detected, and use the reactive power reference value in the normal bypass operation state as the calculation end point, perform smooth exponential decay calculation, and obtain a real-time exit value of the reactive power reference value; (12) in, is the real-time exit value of the reactive power reference value during fault recovery. The sampled active power output value at the time when the fault recovery instruction is detected, It is the active power reference value under normal bypass operation. is the attenuation coefficient.

[0035] The above-mentioned embodiment provides a low voltage ride-through and recovery method for a grid-type converter. When the grid-type converter enters a droop control state and starts low voltage ride-through, it is assumed that there is a virtual impedance between the low voltage control point where the grid-type converter is located and the AC bus, and according to the grid voltage drop level, the reactive current injection reference value and the active current injection reference value of the low voltage ride-through are determined to obtain the reactive power reference value and the active power reference value of the low voltage ride-through. The angular frequency command and the voltage amplitude command of the grid-type converter under the low voltage ride-through are corrected by the power loop reference value of the low voltage ride-through of the droop control power loop, and the virtual current reference value and the active current reference value of the low voltage ride-through are obtained. The virtual impedance value is used to obtain the voltage amplitude compensation amount, and the low voltage ride-through voltage amplitude instruction is corrected again to control the low voltage ride-through of the grid-type converter. After the fault recovery instruction is detected, the virtual impedance value and the power ring reference value are smoothly corrected to control the grid-type converter to smoothly exit the fault ride-through state, so as to achieve the control instruction of the grid-type converter to be corrected when the grid voltage drops, so that the grid-type converter can provide reactive support to the grid during the low voltage process while ensuring a certain degree of active output, avoiding the technical problems of impact current and reactive support requirements caused by the grid-type converter in the case of grid voltage drop and fault recovery, and improving the reliability of low voltage ride-through of the grid-type converter. This method can be applied to smooth low voltage ride-through and recovery under symmetrical grid faults.

[0036] like Figure 6 As shown, this embodiment also provides a low voltage ride through and recovery system for a grid-type converter, including: A droop control power loop correction module is used to obtain a reactive current injection reference value and an active current injection reference value of a grid-type converter, and calculate a power loop reference value of a low voltage ride-through of a droop control power loop based on the obtained value, and correct an angular frequency command and a voltage amplitude command of the grid-type converter according to the power loop reference value to obtain a corrected angular frequency command and a corrected voltage amplitude command; A compensation amount determination module is used to sample the actual current of the power grid, and obtain a virtual impedance value by combining the reactive current injection reference value and the active current injection reference value, and obtain a voltage amplitude compensation amount after determining the voltage drop value corresponding to the virtual impedance value; A secondary correction module, used for correcting the voltage amplitude instruction after the primary correction according to the voltage amplitude compensation amount to obtain a voltage amplitude instruction after the secondary correction; A ride-through control module, used to control the low voltage ride-through of the grid-type converter through the corrected angular frequency instruction and the second corrected voltage amplitude instruction; The fault recovery module is used to smoothly correct the virtual impedance value and the power loop reference value after detecting the fault recovery instruction, and control the grid-type converter to smoothly exit the fault ride-through state.

[0037] The division of modules in the embodiments of the present invention is schematic and is only a logical function division. There may be other division methods in actual implementation. In addition, each functional module in each embodiment of the present invention may be integrated into one processor, or may exist physically separately, or two or more modules may be integrated into one module. The above-mentioned integrated modules may be implemented in the form of hardware or in the form of software functional modules.

[0038] In this embodiment, a computer device is also provided, which includes a processor and a memory, wherein the memory is used to store a computer program (in this embodiment, the computer program includes a computing component and an iterative component, and can perform model calculation and model update), the computer program includes program instructions, and the processor is used to execute the program instructions stored in the computer storage medium. The processor may be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA) or other programmable logic devices, discrete gates or transistor logic devices, discrete hardware components, etc. It is the computing core and control core of the terminal, which is suitable for implementing one or more instructions, and is specifically suitable for loading and executing one or more instructions in a computer storage medium to implement a corresponding method flow or a corresponding function; the processor described in the embodiment of the present invention can be used for the operation of a low voltage ride-through and recovery method of a grid-type converter.

[0039] Reference below Figure 7 , which shows a schematic diagram of the structure of a low voltage ride through and fault recovery control device suitable for implementing the embodiment of the present application. The low voltage ride through and fault recovery control device in the embodiment of the present application may include but is not limited to mobile terminals such as laptop computers, PDAs (Personal Digital Assistants), PADs (Portable Application Descriptions: tablet computers), etc., and fixed terminals such as desktop computers, etc. Figure 7The low voltage ride-through and fault recovery control device shown is merely an example and should not bring any limitation to the functions and scope of use of the embodiments of the present application.

[0040] like Figure 7 As shown, the above-mentioned computer device may include a processing device 1001 (such as a central processing unit, a graphics processor, etc.), which can perform various appropriate actions and processes according to a program stored in a read-only memory (ROM: Read Only Memory) 1002 or a program loaded from a storage device 1003 to a random access memory (RAM: Random Access Memory) 1004. In RAM1004, various programs and data required for the operation of the xxx device are also stored. The processing device 1001, ROM1002 and RAM1004 are connected to each other through a bus 1005. An input / output (I / O) interface 1006 is also connected to the bus. Generally, the following systems can be connected to the I / O interface 1006: an input device 1007 including, for example, a touch screen, a touch pad, a keyboard, a mouse, an image sensor, a microphone, etc.; an output device 1008 including, for example, a liquid crystal display (LCD: Liquid Crystal Display), a speaker, etc.; a storage device 1003 including, for example, a magnetic tape, a hard disk, etc.; and a communication device 1009. The communication device 1009 may allow the low voltage ride through and fault recovery control device to communicate with other devices wirelessly or by wire to exchange data. The computer device may be a low voltage ride through and fault recovery control device.

[0041] In particular, according to the embodiments disclosed in the present application, the process described above with reference to the flowchart can be implemented as a computer software program. The embodiments disclosed in the present application include a computer program product, which includes a computer program carried on a computer-readable medium, and the computer program includes a program code for executing the method shown in the flowchart. In such an embodiment, the computer program can be downloaded and installed from a network through a communication device, or installed from a storage device 1003, or installed from a ROM 1002. When the computer program is executed by the processing device 1001, the above-mentioned functions defined in the method of the embodiment disclosed in the present application are executed.

[0042] The computer equipment provided in the present application adopts the low voltage ride-through and recovery method of the grid-type converter in the above-mentioned embodiment, which can solve the technical problems of impact current and reactive power support requirements caused by grid-type converters when the grid voltage drops and faults are restored.

[0043] This embodiment also provides a storage medium, specifically a computer-readable storage medium (Memory), which is a memory device in a computer device for storing programs and data. It is understandable that the computer-readable storage medium here can include both built-in storage media in a computer device and, of course, extended storage media supported by the computer device. The computer-readable storage medium provides a storage space, which stores the operating system of the terminal. In addition, one or more instructions suitable for being loaded and executed by a processor are also stored in the storage space, and these instructions can be one or more computer programs (including program codes). It should be noted that the computer-readable storage medium here can be a high-speed RAM memory or a non-volatile memory, such as at least one disk memory. The processor can load and execute one or more instructions stored in the computer-readable storage medium to implement the corresponding steps of a low voltage ride-through and recovery method of a grid-type converter in the above embodiment.

[0044] This embodiment also provides a computer program product, which includes a computer program. When the computer program is executed by a processor, the corresponding steps of the low voltage ride-through and recovery method of a grid-type converter in the above embodiment are implemented.

[0045] Those skilled in the art will appreciate that embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present invention may take 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 code.

[0046] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks 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 produce 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.

[0047] 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.

[0048] 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.

[0049] 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 above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A low voltage ride through and recovery method for a grid-type converter, characterized in that: The following steps are involved: Obtaining a reactive current injection reference value and an active current injection reference value of a grid-type converter, and calculating a power loop reference value of a droop control power loop low voltage ride-through based on the reactive current injection reference value and calculating a corrected angular frequency command and a corrected voltage amplitude command based on the power loop reference value; and correcting an angular frequency command and a corrected voltage amplitude command of the grid-type converter according to the power loop reference value. Sampling the actual current of the power grid, and obtaining a virtual impedance value by combining the reactive current injection reference value and the active current injection reference value, and obtaining a voltage amplitude compensation amount after determining a voltage drop value corresponding to the virtual impedance value; Correcting the primary corrected voltage amplitude instruction according to the voltage amplitude compensation amount to obtain a secondary corrected voltage amplitude instruction; Controlling the low voltage ride-through of the grid-type converter by means of the corrected angular frequency command and the second corrected voltage amplitude command; After the fault recovery instruction is detected, the virtual impedance value and the power loop reference value are smoothly corrected to control the grid-type converter to smoothly exit the fault ride-through state.

2. A low voltage ride through and recovery method for a grid-type converter according to claim 1, characterized in that: The power loop reference value includes: a reactive power reference value and an active power reference value, and the virtual impedance value includes: a virtual resistance given value and a virtual inductance given value.

3. A low voltage ride through and recovery method for a grid-type converter according to claim 2, characterized in that: The step of obtaining the reactive current injection reference value and the active current injection reference value of the grid-type converter specifically includes: Obtain the grid voltage and perform coordinate transformation to obtain the direct-axis voltage and quadrature-axis voltage; Comparing the nominal voltage of the power grid with the direct-axis voltage to obtain a power grid voltage drop level; According to the grid voltage drop level and the quadrature-axis current corresponding to the quadrature-axis voltage, reactive compensation calculation is performed to obtain a reactive current injection reference value of the grid-type converter; The remaining capacity of the power grid is obtained, and a difference theoretical calculation is performed on the remaining capacity and a reactive current injection reference value to obtain an active current injection reference value.

4. A low voltage ride through and recovery method for a grid-type converter according to claim 3, characterized in that: The step of calculating the power loop reference value during the low voltage ride-through of the droop control power loop specifically includes: According to the reactive current injection reference value and the active current injection reference value, and in combination with the direct-axis voltage and the quadrature-axis voltage, instantaneous power calculation is performed to obtain the reactive power reference value and the active power reference value of the low voltage ride-through of the droop control power loop.

5. A low voltage ride through and recovery method for a grid-type converter according to claim 2, characterized in that: The step of sampling the actual current of the power grid, obtaining a virtual impedance value by combining the reactive current injection reference value and the active current injection reference value, and obtaining a voltage amplitude compensation amount after determining a voltage drop value corresponding to the virtual impedance value specifically includes: Sampling the actual current of the power grid to obtain a current sampling value, and performing coordinate transformation on the current sampling value to obtain a direct-axis sampling current and a quadrature-axis sampling current; After making a difference comparison between the active current injection reference value and the direct axis sampling current, proportional integral adjustment is performed to obtain a virtual resistance given value; After making a difference comparison between the reactive current injection reference value and the quadrature axis sampling current, a proportional integral adjustment is performed to obtain a virtual inductance given value; According to the virtual resistance given value and the direct-axis sampling current, a direct-axis voltage compensation amount is obtained, and according to the virtual inductance given value and the quadrature-axis sampling current, a quadrature-axis voltage compensation amount is obtained. The direct-axis voltage compensation amount and the quadrature-axis voltage compensation amount constitute the voltage amplitude compensation amount.

6. A low voltage ride through and recovery method for a grid-type converter according to claim 2, characterized in that: After the fault recovery instruction is detected, the virtual impedance value and the power loop reference value are smoothly corrected to control the grid-type converter to smoothly exit the fault ride-through state, specifically comprising: Performing exponential decay calculation on the virtual impedance value to obtain a real-time exit value of the virtual impedance; The active power output value at the time of detecting the fault recovery instruction is sampled and maintained, and the active power reference value under the normal bypass operation state is used as the calculation end point, and a smoothing exponential increase calculation is performed to obtain a real-time exit value of the active power reference value; The reactive power output value at the time of detecting the fault recovery instruction is sampled and maintained, and the reactive power reference value under the normal bypass operation state is used as the calculation end point, and a smooth exponential decay calculation is performed to obtain a real-time exit value of the reactive power reference value; According to the real-time exit value of the virtual impedance, the real-time exit value of the active power reference value and the real-time exit value of the reactive power reference value, the grid-type converter is controlled to smoothly exit the fault ride-through state.

7. A low voltage ride through and recovery system for a grid-type converter, characterized in that: include: A droop control power loop correction module is used to obtain a reactive current injection reference value and an active current injection reference value of a grid-type converter, and calculate a power loop reference value of a low voltage ride-through of a droop control power loop based on the obtained value, and correct an angular frequency command and a voltage amplitude command of the grid-type converter according to the power loop reference value to obtain a corrected angular frequency command and a corrected voltage amplitude command; A compensation amount determination module is used to sample the actual current of the power grid, and obtain a virtual impedance value by combining the reactive current injection reference value and the active current injection reference value, and obtain a voltage amplitude compensation amount after determining the voltage drop value corresponding to the virtual impedance value; A secondary correction module, used for correcting the voltage amplitude instruction after the primary correction according to the voltage amplitude compensation amount to obtain a voltage amplitude instruction after the secondary correction; A ride-through control module, used to control the low voltage ride-through of the grid-type converter through the corrected angular frequency instruction and the second corrected voltage amplitude instruction; The fault recovery module is used to smoothly correct the virtual impedance value and the power loop reference value after detecting the fault recovery instruction, and control the grid-type converter to smoothly exit the fault ride-through state.

8. A computer device, characterized in that: It comprises a memory, a processor and a computer program stored in the memory and executable in the processor, wherein when the processor executes the computer program, the steps of a low voltage ride-through and recovery method for a grid-type converter as described in any one of claims 1 to 6 are implemented.

9. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the steps of a low voltage ride-through and recovery method for a grid-type converter as described in any one of claims 1 to 6 are implemented.

10. A computer program product, the computer product comprising a computer program, characterized in that: When the computer program is executed by a processor, the steps of a low voltage ride-through and recovery method for a grid-type converter as described in any one of claims 1 to 6 are implemented.

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