Network construction type converter control method and system considering primary frequency modulation dead zone

Abstract

The invention discloses a network construction type converter control method and system considering a primary frequency modulation dead zone. The method comprises the following steps: determining a relationship between actual output power of a network construction type inverter without the primary frequency modulation dead zone and reference power; according to the inertia demand in the primary frequency modulation dead zone, selecting the mode of the primary frequency modulation dead zone of the network-building inverter; setting a frequency dead zone range, and sampling the frequency of the power grid system; according to the obtained frequency dead zone range and the frequency of the power grid system, whether the frequency of the current power grid system is located in a set frequency dead zone is determined, and signal selection is obtained; according to the selection of a primary frequency modulation dead zone mode of a network-forming inverter, when a primary frequency modulation inertia demand is small, a primary frequency modulation dead zone is realized by adopting an inverter output port voltage frequency measurement method; when the inertia demand of the selected primary frequency modulation is large, a direct current / alternating current side power instruction modification method is adopted to realize a primary frequency modulation dead zone, and the setting of the primary frequency modulation dead zone of the network-forming inverter is realized; and the service life of the energy storage system is effectively prolonged.

Description

Background Art

[0002] With the rapid development and application of renewable energy power generation, the trend of weak grid is obvious. Weak grids show characteristics such as weak synchronous support and poor frequency anti-disturbance ability, and the stability risk increases. The grid-forming converter that simulates synchronous generator control can actively support the voltage and frequency of the grid, and can provide strong guarantee for the safe and stable operation of weak grids with a high proportion of renewable energy access, making the research on active support provided by grid-forming converters in the grid widely concerned.

[0003] At present, the control of grid-type inverters has not considered the dead zone setting of primary frequency modulation. When the frequency disturbance is small, primary frequency modulation is still performed. However, when the wind and solar inverters participate in primary frequency modulation, they need to be reserved, which reduces the energy utilization rate; when the energy storage inverter participates in primary frequency modulation in the dead zone, the energy storage inverter will be frequently charged and discharged, increasing the number of cycles and reducing its service life. If the dead zone setting of the grid-type inverter is realized through control, the utilization rate of new energy and the service life of the energy storage system can be improved. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a grid-type converter control method and system taking into account the primary frequency modulation dead zone in view of the deficiencies in the above-mentioned prior art, so as to solve the technical problem that the primary frequency modulation dead zone of the grid-type converter cannot be directly achieved by modifying the current reference instruction.

[0005] The present invention adopts the following technical solutions: A control method for a grid-connected converter taking into account a primary frequency modulation dead zone comprises the following steps: S1. Determine the relationship between the actual output power and the reference power of the grid-connected inverter without a primary frequency modulation dead zone; S2. According to the inertia requirement within the inertia primary frequency regulation dead zone, select the primary frequency regulation dead zone method of the grid-type inverter; S3, set frequency dead zone range f db Size, frequency of sampling grid system f g ; S4: Frequency dead zone range obtained according to step S3 f db Size and frequency of the power grid system f g Size, determine whether the frequency of the current power grid system is within the set frequency dead zone, when | f g - f n |Less than f db / 2, the signal selection is obtained; S5. According to the selection of the primary frequency modulation dead zone mode of the grid-forming inverter in step S2, when the primary frequency modulation inertia demand is small, the primary frequency modulation dead zone is realized by the inverter output port voltage frequency measurement method; when the primary frequency modulation inertia demand is large, the DC / AC side power instruction modification method is used to realize the primary frequency modulation dead zone, thereby realizing the primary frequency modulation dead zone setting of the grid-forming inverter.

[0006] Preferably, in step S1, the relationship between the actual output power of the grid-connected inverter without a primary frequency modulation dead zone and the reference power is as follows:

[0007] in, p INV is the actual output power instruction of the inverter, P INV_ref is the power reference command of the inverter, k D_INV is the slope of the inverter droop curve, ω o is the actual angular frequency of the inverter output port, ω ref is the reference angular frequency of the inverter.

[0008] Preferably, in step S2, when the inertia requirement is small, the inverter output port voltage frequency measurement method is selected, and when the inertia requirement is large, the DC / AC side power instruction modification method is selected.

[0009] Preferably, in step S4, the signal selection for:

[0010] in, f n is the rated frequency of the power grid system, f g is the frequency of the power grid system, f db is the frequency dead zone range.

[0011] Preferably, in step S5, when the primary frequency modulation inertia requirement is small, the primary frequency modulation dead zone is realized by using the inverter output port voltage frequency measurement method, and the relationship between the actual power output of the grid-type inverter and the reference power is constructed. as follows:

[0012] in, is the measured angular frequency of the inverter output port, It is a judgment signal for whether the frequency of the power grid system is in the dead zone.

[0013] Preferably, when the primary frequency modulation dead zone is realized ω ref The expression is: .

[0015] Preferably, in step S5, when the primary frequency modulation inertia demand is large, the primary frequency modulation dead zone is realized by modifying the DC side power command in a DC voltage synchronous control manner, and the DC side power command is equal to the actual power output by the grid-forming inverter.

[0016] Preferably, the flow-side power instruction is equal to the actual power output by the grid-connected inverter as follows:

[0017] in, is the power reference command on the DC side of the two-stage inverter, is the equivalent droop coefficient of DC voltage control.

[0018] Preferably, a virtual synchronous machine control method is adopted to realize the primary frequency modulation dead zone through the AC side power instruction modification method, and the relationship between the actual power output of the grid-forming inverter and the reference power is expressed as: .

[0020] In a second aspect, an embodiment of the present invention provides a grid-connected converter control system taking into account a primary frequency modulation dead zone, comprising: A relationship module, determining the relationship between the actual output power and the reference power of the grid-forming inverter without a primary frequency regulation dead zone; Select the module and select the primary frequency regulation dead zone mode of the grid-type inverter according to the inertia requirement within the primary frequency regulation dead zone; Set the module to set the frequency dead zone range f db Size, frequency of sampling grid system f g ; The judgment module obtains the frequency dead zone range f db Size and frequency of the power grid system f g Size, determine whether the frequency of the current power grid system is within the set frequency dead zone, when | f g - f n |Less than f db / 2, the signal selection is obtained; The control module selects the primary frequency modulation dead zone mode of the grid-forming inverter. When the primary frequency modulation inertia demand is small, the primary frequency modulation dead zone is realized by the inverter output port voltage frequency measurement method; when the primary frequency modulation inertia demand is large, the DC / AC side power instruction modification method is adopted to realize the primary frequency modulation dead zone, thereby realizing the primary frequency modulation dead zone setting of the grid-forming inverter.

[0021] In a third aspect, a computer device comprises a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the steps of the above-mentioned method for controlling a grid-connected converter taking into account a primary frequency modulation dead zone when executing the computer program.

[0022] In a fourth aspect, an embodiment of the present invention provides a computer-readable storage medium, including a computer program, which, when executed by a processor, implements the steps of the above-mentioned grid-connected converter control method taking into account the primary frequency modulation dead zone.

[0023] In a fifth aspect, a chip comprises a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the computer program, the steps of the above-mentioned method for controlling a grid-connected converter taking into account a primary frequency modulation dead zone are implemented.

[0024] In a sixth aspect, an embodiment of the present invention provides an electronic device, including a computer program, which, when executed by the electronic device, implements the steps of the above-mentioned grid-connected converter control method taking into account the primary frequency modulation dead zone.

[0025] Compared with the prior art, the present invention has at least the following beneficial effects: A control method for a grid-type converter taking into account the primary frequency regulation dead zone, realizes the primary frequency regulation dead zone of the grid-type converter by measuring the output port voltage frequency, modifying the power reference instruction on the DC side during DC voltage synchronous control, or modifying the power reference instruction on the AC side during virtual synchronous machine control; if it is applied to a wind-solar grid-type inverter, it can solve the problem of abandoned light and abandoned phoenix caused by leaving upper reserve for primary frequency regulation; if it is applied to an energy storage grid-type inverter, the energy storage system will exchange power outside the set primary frequency regulation dead zone; it can reduce the frequent charging and discharging of the energy storage system, reduce its cycle times, thereby effectively improving the service life of the energy storage system, and has high practical value and economic benefits.

[0026] Furthermore, the relationship between the actual output power and the reference power of the grid-connected inverter without the primary frequency modulation dead zone provides a basis for power control outside the dead zone.

[0027] Furthermore, the inverter output port voltage frequency measurement method does not directly provide inertia, and the inertia response part of the DC / AC side power command modification method is retained. Therefore, the inverter output port voltage frequency measurement method is selected when the inertia demand is small, and the DC / AC side power command modification method is selected when the inertia demand is large. The purpose or benefit of setting is given, and the principle analysis is explained.

[0028] Furthermore, when the primary frequency modulation inertia demand is small, the inverter output port voltage frequency measurement method is used to realize the primary frequency modulation dead zone. The frequency of the inverter output port voltage is used as the reference frequency in the dead zone so that it does not participate in the primary frequency modulation in the dead zone and the inertia response is small.

[0029] Furthermore, the selection principle of reference frequency is given.

[0030] Furthermore, when the primary frequency modulation inertia requirement is large, if the inverter is a two-stage topology, the DC voltage synchronous control method can be used to directly control the DC side power command to achieve the primary frequency modulation dead zone.

[0031] It can be understood that the beneficial effects of the second to sixth aspects mentioned above can be found in the relevant description of the first aspect mentioned above, and will not be repeated here.

[0032] In summary, the present invention provides a method for realizing the primary frequency modulation dead zone of grid-connected inverters with different topologies, different control modes, and different inertia requirements, which can effectively improve the service life of the energy storage system.

[0033] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments of the present application. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0035] Figure 1 This is a single-stage DC / AC topology diagram; Figure 2 It is a two-stage DC / AC topology diagram; Figure 3 It is a droop curve diagram containing primary frequency modulation dead zone; Figure 4 A flow chart of the method for realizing the primary frequency modulation dead zone of the grid-type inverter of the present invention; Figure 5 It is the block diagram of DC voltage synchronous control; Figure 6It is the control block diagram of virtual synchronous machine; Figure 7 Select the block diagram for the signal; Figure 8 It is the inverter output voltage frequency measurement module; Fig. 9 This is a test bench for verifying the primary frequency modulation dead zone of a grid-type energy storage inverter, where (a) is the overall schematic diagram and (b) is the detailed diagram; Fig.10 The experimental results under different control schemes are shown in Figure 1, where (a) is the inverter output power and (b) is the system frequency; Fig.11 A schematic diagram of a computer device provided by an embodiment of the present invention; Fig.12 The present invention is a block diagram of an electronic device provided according to an embodiment. DETAILED DESCRIPTION

[0036] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0037] In the description of the present invention, it should be understood that the terms “include” and “comprises” indicate the presence of described features, wholes, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, wholes, steps, operations, elements, components and / or collections thereof.

[0038] It should also be understood that the terms used in the present specification are only for the purpose of describing specific embodiments and are not intended to limit the present invention. As used in the present specification and the appended claims, unless the context clearly indicates otherwise, the singular forms "a", "an" and "the" are intended to include plural forms.

[0039] It should be further understood that the term "and / or" used in the present specification and the appended claims refers to any combination of one or more of the associated listed items and all possible combinations, and includes these combinations. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in the present invention generally indicates that the associated objects are in an "or" relationship.

[0040] It should be understood that, although the terms first, second, third, etc. may be used to describe preset ranges, etc. in the embodiments of the present invention, these preset ranges should not be limited to these terms. These terms are only used to distinguish preset ranges from each other. For example, without departing from the scope of the embodiments of the present invention, the first preset range may also be referred to as the second preset range, and similarly, the second preset range may also be referred to as the first preset range.

[0041] The word "if" as used herein may be interpreted as "at the time of" or "when" or "in response to determining" or "in response to detecting", depending on the context. Similarly, the phrases "if it is determined" or "if (stated condition or event) is detected" may be interpreted as "when it is determined" or "in response to determining" or "when detecting (stated condition or event)" or "in response to detecting (stated condition or event)", depending on the context.

[0042] Various structural schematic diagrams of the embodiments disclosed in the present invention are shown in the accompanying drawings. These figures are not drawn to scale, and some details are magnified and some details may be omitted for the purpose of clear expression. The shapes of various regions and layers shown in the figures and the relative sizes and positional relationships therebetween are only exemplary, and may deviate in practice due to manufacturing tolerances or technical limitations, and those skilled in the art may additionally design regions / layers with different shapes, sizes, and relative positions according to actual needs.

[0043] The present invention provides a control method for a grid-type converter taking into account a primary frequency modulation dead zone. According to the size of the inertia demand in the primary frequency modulation dead zone, the voltage frequency of the output port of the grid-type converter can be measured, and the DC side power reference value of a two-stage grid-type converter adopting a DC voltage synchronous control method can be modified, or the AC side power reference value of a grid-type converter adopting a virtual synchronous machine control method can be modified, thereby realizing the primary frequency modulation dead zone of the grid-type converter.

[0044] See also Figure 1 and Figure 2 , the grid-type inverter can be divided into two-stage and single-stage. The connection structure of the two-stage grid-type inverter is: DC input side, DC / DC converter, DC bus side, DC / AC inverter, filter circuit. The connection structure of the single-stage grid-type inverter is: DC bus side, DC / AC inverter, filter circuit.

[0045] See also Figure 3 and Figure 4The present invention provides a control method for a grid-type converter taking into account the primary frequency modulation dead zone. Aiming at the problem that when the grid-type inverter is connected to the power grid, it is not possible to directly achieve non-response in the primary frequency modulation dead zone by modifying the current reference instruction, a control technology for a grid-type converter in the primary frequency modulation dead zone is proposed. This control technology realizes the primary frequency modulation dead zone of the grid-type converter by measuring the output port voltage frequency, modifying the power reference instruction on the DC side during DC voltage synchronous control, or modifying the power reference instruction on the AC side during virtual synchronous machine control according to the requirement for the inertia size in the primary frequency modulation dead zone. The specific steps are as follows: S1. Determine the relationship between the actual output power and the reference power of the grid-connected inverter without a primary frequency modulation dead zone; The relationship between the actual output power and the reference power of a grid-connected inverter without a primary frequency modulation dead zone is as follows:

[0046] Among them, the frequency of the power grid system is denoted as f g ; The rated frequency of the power grid system is recorded as f n ; The rated angular frequency of the power grid system is denoted as ω n ; The reference angular frequency of the inverter is denoted as ω ref ; The actual angular frequency of the inverter output port is denoted as ω o ; The measured angular frequency of the inverter output port is denoted as ω ME ; Frequency dead zone range, denoted as f db ; The upper and lower limits of the frequency corresponding to the dead zone are recorded as f b_max and f b_min ; The slope of the inverter droop curve is denoted by k D_INV ; Inverter inertia, denoted as J INV ; The actual output power command of the inverter is recorded as p INV ; The power reference command of the inverter is denoted as P INV_ref ; The power reference command on the DC side of the two-stage inverter is denoted as p dc_ref ; The actual value of the DC capacitor voltage of the two-stage inverter is recorded as u dc ; The rated voltage of the DC capacitor of the two-stage inverter is expressed as U dc; The DC capacitor voltage reference value of the two-stage inverter is denoted as u dc_ref ; Two-stage inverter DC capacitor value, denoted as C dc ; The equivalent droop coefficient of DC voltage control is expressed as G u ( G u =- C dc U dc k D_INV / J INV ω n ); whether the frequency of the power grid system is in the dead zone, denoted as Signal .

[0047] S2. According to the inertia requirement within the inertia primary frequency regulation dead zone, select the appropriate grid-type inverter primary frequency regulation dead zone method; When inertia response is not required, select the inverter output port voltage frequency measurement method. When inertia response is required, select the DC / AC side power command modification method.

[0048] S3, set frequency dead zone range f db Size, frequency of sampling grid system f g ; S4: Frequency dead zone range obtained according to step S3 f db Size and frequency of the power grid system f g Size, determine whether the frequency of the current power grid system is within the set frequency dead zone, that is, judge | f g - f n Is it less than f db / 2, get its signal selection; Signal selection for:

[0049] in, f n is the rated frequency of the power grid system, f g is the frequency of the power grid system, f db is the frequency dead zone range.

[0050] S5. According to the selection in step S2, when the primary frequency modulation inertia requirement is small, the primary frequency modulation dead zone is realized by using the inverter output port voltage frequency measurement method; When achieving a frequency modulation dead zone ω ref The expression is:

[0051] Relationship between actual power output and reference power of grid-connected inverter when using inverter output port voltage frequency measurement method to realize primary frequency modulation dead zone as follows:

[0052] in, for, for, is the actual angular frequency of the inverter output port, is the measured angular frequency of the inverter output port, It is a judgment signal for whether the frequency of the power grid system is in the dead zone.

[0053] S6. According to the selection in step S2, when the primary frequency modulation inertia demand is large, the DC / AC side power instruction modification method is used to realize the primary frequency modulation dead zone, and the primary frequency modulation dead zone setting of the grid-type inverter is realized according to the existing DC voltage synchronous control and virtual synchronous machine control method.

[0054] See also Figure 5 , the DC voltage synchronous control method is adopted to realize the primary frequency modulation dead zone through the DC side power instruction modification method. The DC side power instruction is equal to the actual power output by the grid-forming inverter, as follows:

[0055] in, is the power reference command on the DC side of the two-stage inverter, is the actual output power command of the inverter, is the actual angular frequency of the inverter output port, is the measured angular frequency of the inverter output port, is the power reference command of the inverter, is the equivalent droop coefficient of DC voltage control.

[0056] See also Figure 6 , Figure 7 and Figure 8 , the virtual synchronous machine control method is adopted to realize the primary frequency modulation dead zone through the AC side power instruction modification method. The relationship between the actual power output of the grid-type inverter and the reference power is expressed as:

[0057] in, is the power reference command of the inverter, Signal It is a signal to judge whether the frequency of the power grid system is in the dead zone. is the slope of the inverter droop curve, is the actual angular frequency of the inverter output port, is the measured angular frequency of the inverter output port.

[0058] It will be appreciated by those skilled in the art that various aspects of the present invention may be implemented as systems, methods or program products. Therefore, various aspects of the present invention may be specifically implemented in the following forms, namely: complete hardware implementation, complete software implementation (including firmware, microcode, etc.), or a combination of hardware and software implementations, which may be collectively referred to herein as "circuits", "modules" or "platforms".

[0059] In another embodiment of the present invention, a grid-type converter control system taking into account the primary frequency modulation dead zone is provided. The system can be used to implement the above-mentioned grid-type converter control method taking into account the primary frequency modulation dead zone. Specifically, the grid-type converter control system taking into account the primary frequency modulation dead zone includes a relationship module, a selection module, a setting module, a judgment module and a control module.

[0060] Among them, the relationship module determines the relationship between the actual output power and the reference power of the grid-forming inverter without a primary frequency regulation dead zone; Select the module and select the primary frequency regulation dead zone mode of the grid-type inverter according to the inertia requirement within the primary frequency regulation dead zone; Set the module to set the frequency dead zone range f db Size, frequency of sampling grid system f g ; The judgment module obtains the frequency dead zone range f db Size and frequency of the power grid system f g Size, determine whether the frequency of the current power grid system is within the set frequency dead zone, when | f g - f n |Less than f db / 2, the signal selection is obtained; The control module selects the primary frequency modulation dead zone mode of the grid-forming inverter. When the primary frequency modulation inertia demand is small, the primary frequency modulation dead zone is realized by the inverter output port voltage frequency measurement method; when the primary frequency modulation inertia demand is large, the DC / AC side power instruction modification method is adopted to realize the primary frequency modulation dead zone, thereby realizing the primary frequency modulation dead zone setting of the grid-forming inverter.

[0061] In another embodiment of the present invention, a terminal device is provided, which includes a processor and a memory, wherein the memory is used to store a computer program, 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, graphics processing units (GPU), tensor processing units (TPU), 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 to implement the corresponding method flow or corresponding function; the processor described in the embodiment of the present invention can be used for the operation of the control method of the grid-type converter taking into account the primary frequency modulation dead zone, including: Determine the relationship between the actual output power and the reference power of the grid-forming inverter without the primary frequency modulation dead zone; select the primary frequency modulation dead zone mode of the grid-forming inverter according to the size of the inertia requirement within the inertia primary frequency modulation dead zone; set the frequency dead zone range f db Size, frequency of sampling grid system f g ;According to the obtained frequency dead zone range f db Size and frequency of the power grid system f g Size, determine whether the frequency of the current power grid system is within the set frequency dead zone, when | f g - f n |Less than f db / 2, its signal selection is obtained; according to the selection of the primary frequency modulation dead zone mode of the grid-forming inverter, when the primary frequency modulation inertia demand is small, the primary frequency modulation dead zone is realized by the inverter output port voltage frequency measurement method; when the primary frequency modulation inertia demand is large, the DC / AC side power instruction modification method is used to realize the primary frequency modulation dead zone, thereby realizing the primary frequency modulation dead zone setting of the grid-forming inverter.

[0062] See also Fig.11 , the terminal device is a computer device, and the computer device 60 of this embodiment includes: a processor 61, a memory 62, and a computer program 63 stored in the memory 62 and executable on the processor 61. When the computer program 63 is executed by the processor 61, the control method of the grid-type converter taking into account the primary frequency modulation dead zone in the embodiment is implemented. To avoid repetition, it is not described one by one here. Alternatively, when the computer program 63 is executed by the processor 61, the functions of each model / unit in the grid-type converter control system taking into account the primary frequency modulation dead zone in the embodiment are implemented. To avoid repetition, it is not described one by one here.

[0063] The computer device 60 may be a computing device such as a desktop computer, a notebook, a PDA, or a cloud server. The computer device 60 may include, but is not limited to, a processor 61 and a memory 62. Those skilled in the art will appreciate that Fig.11 This is only an example of the computer device 60 and does not constitute a limitation of the computer device 60. It may include more or fewer components than shown in the figure, or a combination of certain components, or different components. For example, the computer device may also include input and output devices, network access devices, buses, etc.

[0064] The processor 61 may be a central processing unit (CPU), or other general-purpose processors, graphics processing units (GPU), tensor processing units (TPU), digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor may be a microprocessor or any conventional processor, etc.

[0065] The memory 62 may be an internal storage unit of the computer device 60, such as a hard disk or memory of the computer device 60. The memory 62 may also be an external storage device of the computer device 60, such as a plug-in hard disk, a smart memory card (SmartMediaCard, SMC), a secure digital (SecureDigital, SD) card, a flash card (FlashCard), etc. equipped on the computer device 60.

[0066] Furthermore, the memory 62 may include both an internal storage unit of the computer device 60 and an external storage device. The memory 62 is used to store computer programs and other programs and data required by the computer device. The memory 62 may also be used to temporarily store data that has been output or is to be output.

[0067] See also Fig.12 The terminal device is an electronic device 600, which is in the form of a general-purpose computing device. The components of the electronic device may include, but are not limited to: at least one processing unit 610, at least one storage unit 620, a bus 630 connecting different platform components (including the storage unit 620 and the processing unit 610), a display unit 640, etc.

[0068] The storage unit stores program codes, which can be executed by the processing unit 610, so that the processing unit 610 performs the steps according to various exemplary embodiments of the present invention described in the above method section of this specification. For example, the processing unit 610 can perform the following steps: Figure 4 Follow the steps shown in .

[0069] The storage unit 620 may include a readable medium in the form of a volatile storage unit, such as a random access storage unit (RAM) 6201 and / or a cache storage unit 6202 , and may further include a read-only storage unit (ROM) 6203 .

[0070] The storage unit 620 may also include a program / utility 6204 having a set (at least one) of program modules 6205, such program modules 6205 including but not limited to: an operating system, one or more application programs, other program modules, and program data, each of which or some combination may include an implementation of a network environment.

[0071] Bus 630 may represent one or more of several types of bus structures, including a memory unit bus or memory unit controller, a peripheral bus, an accelerated graphics port, a processing unit, or a local bus using any of a variety of bus architectures.

[0072] The electronic device 600 may also communicate with one or more external devices 700 (e.g., keyboards, pointing devices, Bluetooth devices, etc.), may also communicate with one or more devices that enable a user to interact with the electronic device 600, and / or communicate with any device that enables the electronic device 600 to communicate with one or more other computing devices (e.g., routers, modems, etc.). Such communication may be performed via an input / output (I / O) interface 650. Furthermore, the electronic device 600 may also communicate with one or more networks (e.g., a local area network (LAN), a wide area network (WAN), and / or a public network, such as the Internet) via a network adapter 660. The network adapter 660 may communicate with other modules of the electronic device 600 via a bus 630. It should be understood that, although not shown in the figure, other hardware and / or software modules may be used in conjunction with the electronic device 600, including but not limited to: microcode, device drivers, redundant processing units, external disk drive arrays, RAID systems, tape drives, and data backup storage platforms, etc.

[0073] In another embodiment of the present invention, the present invention also provides a storage medium, specifically a computer-readable storage medium, which is a memory device in a terminal device for storing programs and data. It can be understood that the computer-readable storage medium here can include both the built-in storage medium in the terminal device and the extended storage medium supported by the terminal 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 the processor are also stored in the storage space, and these instructions can be one or more computer programs. It should be noted that the computer-readable storage medium here can be a high-speed RAM memory, or a non-volatile memory (Non-VolatileMemory), such as at least one disk memory.

[0074] One or more instructions stored in a computer-readable storage medium may be loaded and executed by a processor to implement the corresponding steps of the control method of a grid-connected converter taking into account a primary frequency modulation dead zone in the above embodiment; one or more instructions in the computer-readable storage medium are loaded and executed by a processor as follows: Determine the relationship between the actual output power and the reference power of the grid-forming inverter without the primary frequency modulation dead zone; select the primary frequency modulation dead zone mode of the grid-forming inverter according to the size of the inertia requirement within the inertia primary frequency modulation dead zone; set the frequency dead zone range f db Size, frequency of sampling grid system f g ;According to the obtained frequency dead zone range f dbSize and frequency of the power grid system f g Size, determine whether the frequency of the current power grid system is within the set frequency dead zone, when | f g - f n |Less than f db / 2, its signal selection is obtained; according to the selection of the primary frequency modulation dead zone mode of the grid-forming inverter, when the primary frequency modulation inertia demand is small, the primary frequency modulation dead zone is realized by the inverter output port voltage frequency measurement method; when the primary frequency modulation inertia demand is large, the DC / AC side power instruction modification method is used to realize the primary frequency modulation dead zone, thereby realizing the primary frequency modulation dead zone setting of the grid-forming inverter.

[0075] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. The components of the embodiments of the present invention described and shown in the drawings here can usually be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0076] The dead zone implementation method of the primary frequency regulation dead zone of the grid-connected inverter using the above control strategy is applied to the energy storage system controlled by the virtual synchronous machine to realize the primary frequency regulation dead zone of the grid-connected energy storage inverter under different inertia requirements and in different methods.

[0077] See also Fig. 9 In the experimental platform, VSG_1 simulates synchronous machine control to make the system work at the rated frequency point, and VSG_2 is used to verify the dead zone of the grid-type primary frequency regulation.

[0078] Working condition settings: Rated frequency of power grid f n =50.00Hz; VSG_1 related parameters: Power reference value P INV_ref1 =750W, droop coefficient k D_INV1 =25kW / Hz, inertia J INV1 =1kg·m 2 , dead zonef db1 =0; VSG_2 related parameters: Power reference value P INV_ref2 =0, droop coefficient k D_INV2 =25kW / Hz, inertia J INV2 =2kg·m 2 , dead zone f db2 = f b_max2 – f b_min2 =0.06Hz, the dead zone corresponds to the upper and lower frequencies f b_max2 =50.03Hz, f b_min2 =49.97Hz.

[0079] See also Fig.10 , which is the experimental result diagram of the port voltage measurement method with no primary frequency modulation dead zone, small inertia demand, and power command modification method with large inertia demand under this working condition.

[0080] Under this load disturbance, the grid system frequency is in the dead zone. When the grid-type primary frequency regulation dead zone setting is not adopted, VSG_1 and VSG_2 jointly bear the load disturbance; when the grid-type primary frequency regulation dead zone control is adopted, the load disturbance is completely borne by VSG_1 in steady state, and the inertia response of the port voltage frequency measurement method in the transient process is smaller than the inertia response of the power command modification method.

[0081] The correctness and reliability of the present invention are verified by the above experimental results.

[0082] In summary, the present invention provides a grid-connected converter control method and system taking into account the primary frequency modulation dead zone, by judging the power grid system frequency and the size of the dead zone setting, to obtain the selection signal Signal Then, according to the inertia demand within the primary frequency modulation dead zone, the output port voltage frequency measurement method is selected when the inertia demand is small, and the DC / AC power command modification method is selected when the inertia demand is small, thus realizing the primary frequency modulation dead zone of the grid-type converter. If it is applied to the energy storage grid-type inverter, the energy storage system will exchange power outside the set primary frequency modulation dead zone. It can reduce the frequent charging and discharging of the energy storage system and reduce its cycle times, thereby effectively improving the service life of the energy storage system.

[0083] The technicians in the relevant field can clearly understand that for the convenience and simplicity of description, only the division of the above-mentioned functional units and modules is used as an example for illustration. In practical applications, the above-mentioned function allocation can be completed by different functional units and modules as needed, that is, the internal structure of the device can be divided into different functional units or modules to complete all or part of the functions described above. The functional units and modules in the embodiment can be integrated in a processing unit, or each unit can exist physically separately, or two or more units can be integrated in one unit. The above-mentioned integrated unit can be implemented in the form of hardware or in the form of software functional units. In addition, the specific names of the functional units and modules are only for the convenience of distinguishing each other, and are not used to limit the scope of protection of this application. The specific working process of the units and modules in the above-mentioned system can refer to the corresponding process in the aforementioned method embodiment, which will not be repeated here.

[0084] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described or recorded in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0085] Those skilled in the art will appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed in the present invention can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of the present invention.

[0086] In the embodiments provided by the present invention, it should be understood that the disclosed devices / terminals and methods can be implemented in other ways. For example, the device / terminal embodiments described above are only schematic. For example, the division of the modules or units is only a logical function division. There may be other division methods in actual implementation, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of devices or units, which can be electrical, mechanical or other forms.

[0087] The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0088] In addition, each functional unit in each embodiment of the present invention may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit. The above-mentioned integrated unit may be implemented in the form of hardware or in the form of software functional units.

[0089] If the integrated module / unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the present invention implements all or part of the processes in the above-mentioned embodiment method, and can also be completed by instructing the relevant hardware through a computer program. The computer program can be stored in a computer-readable storage medium, and the computer program can implement the steps of the above-mentioned various method embodiments when executed by the processor. Among them, the computer program includes computer program code, and the computer program code can be in source code form, object code form, executable file or some intermediate form. The computer-readable medium may include: any entity or device capable of carrying the computer program code, recording medium, U disk, mobile hard disk, disk, optical disk, computer memory, read-only memory (ROM), random access memory (RAM), electric carrier signal, telecommunication signal and software distribution medium, etc. It should be noted that the content contained in the computer-readable medium can be appropriately increased or decreased according to the requirements of legislation and patent practice in the jurisdiction. For example, in some jurisdictions, according to legislation and patent practice, computer-readable media do not include electric carrier signals and telecommunication signals.

[0090] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices, and computer program products according to the embodiments of the present application. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of the 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 generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0091] 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 1A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0092] 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.

[0093] The above contents are only for explaining the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A control method for a grid-connected converter taking into account a primary frequency modulation dead zone, characterized in that: The following steps are involved: S1. Determine the relationship between the actual output power and the reference power of the grid-connected inverter without a primary frequency modulation dead zone; S2. According to the inertia requirement within the inertia primary frequency regulation dead zone, select the primary frequency regulation dead zone method of the grid-type inverter; S3, set frequency dead zone range f db Size, frequency of sampling grid system f g ; S4: Frequency dead zone range obtained according to step S3 f db Size and frequency of the power grid system f g Size, determine whether the frequency of the current power grid system is within the set frequency dead zone, when | f g - f n |Less than f db / 2, the signal selection is obtained; S5. According to the selection of the primary frequency modulation dead zone mode of the grid-forming inverter in step S2, when the primary frequency modulation inertia demand is small, the primary frequency modulation dead zone is realized by the inverter output port voltage frequency measurement method; when the primary frequency modulation inertia demand is large, the DC / AC side power instruction modification method is used to realize the primary frequency modulation dead zone, thereby realizing the primary frequency modulation dead zone setting of the grid-forming inverter.

2. The grid-connected converter control method taking into account the primary frequency modulation dead zone according to claim 1, characterized in that: In step S1, the relationship between the actual output power and the reference power of the grid-connected inverter without a primary frequency modulation dead zone is as follows: in, p INV is the actual output power instruction of the inverter, P INV_ref is the power reference command of the inverter, k D_INV is the slope of the inverter droop curve, ω o is the actual angular frequency of the inverter output port, ω ref is the reference angular frequency of the inverter.

3. The grid-connected converter control method taking into account the primary frequency modulation dead zone according to claim 1, characterized in that: In step S2, when the inertia demand is small, the inverter output port voltage frequency measurement method is selected, and when the inertia demand is large, the DC / AC side power command modification method is selected.

4. The grid-connected converter control method taking into account the primary frequency modulation dead zone according to claim 1, characterized in that: In step S4, the signal selection for: in, f n is the rated frequency of the power grid system, f g is the frequency of the power grid system, f db is the frequency dead zone range.

5. The grid-connected converter control method taking into account the primary frequency modulation dead zone according to claim 1, characterized in that: In step S5, when the primary frequency modulation inertia requirement is small, the primary frequency modulation dead zone is realized by using the inverter output port voltage frequency measurement method, and the relationship between the actual power output of the grid-type inverter and the reference power is constructed. p INV as follows: in, is the measured angular frequency of the inverter output port, It is a judgment signal for whether the frequency of the power grid system is in the dead zone.

6. The grid-connected converter control method taking into account the primary frequency modulation dead zone according to claim 5, characterized in that: When achieving a frequency modulation dead zone ω ref The expression is: 。 7. The grid-connected converter control method taking into account the primary frequency modulation dead zone according to claim 1, characterized in that: In step S5, when the primary frequency modulation inertia demand is large, the primary frequency modulation dead zone is realized by modifying the DC side power command in a DC voltage synchronous control manner, and the DC side power command is equal to the actual power output by the grid-forming inverter.

8. The grid-connected converter control method taking into account the primary frequency modulation dead zone according to claim 7, characterized in that: The power command on the flow side is equal to the actual power output by the grid-connected inverter as follows: in, is the power reference command on the DC side of the two-stage inverter, is the equivalent droop coefficient of DC voltage control.

9. The grid-connected converter control method taking into account the primary frequency modulation dead zone according to claim 7, characterized in that: The virtual synchronous machine control method is used to realize the primary frequency modulation dead zone through the AC side power instruction modification method. The relationship between the actual power output of the grid-type inverter and the reference power is expressed as: 。 10. A grid-connected converter control system taking into account the primary frequency modulation dead zone, characterized in that: include: A relationship module, determining the relationship between the actual output power and the reference power of the grid-forming inverter without a primary frequency regulation dead zone; Select the module and select the primary frequency regulation dead zone mode of the grid-type inverter according to the inertia requirement within the primary frequency regulation dead zone; Set the module to set the frequency dead zone range f db Size, frequency of sampling grid system f g ; The judgment module obtains the frequency dead zone range f db Size and frequency of the power grid system f g Size, determine whether the frequency of the current power grid system is within the set frequency dead zone, when | f g - f n |Less than f db / 2, the signal selection is obtained; The control module selects the primary frequency modulation dead zone mode of the grid-forming inverter. When the primary frequency modulation inertia demand is small, the primary frequency modulation dead zone is realized by the inverter output port voltage frequency measurement method; when the primary frequency modulation inertia demand is large, the DC / AC side power instruction modification method is adopted to realize the primary frequency modulation dead zone, thereby realizing the primary frequency modulation dead zone setting of the grid-forming inverter.

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