Power distribution droop control method and system for multiple parallel static var generators

Abstract

The invention discloses a power distribution droop control method and a power distribution droop control system for multiple parallel static var generators, which are characterized in that under the control method of an original active power filter, each harmonic component of power grid voltage is added into an instruction value of a current control inner loop of the active power filter through a band-pass filter, so that the phenomenon of harmonic compensation resonance is inhibited. And aiming at a nonlinear load, the harmonic compensation effect can be better realized, and the overall stability of the system is improved. Meanwhile, a simulation model of the active power filter applied to compensation of nonlinear load harmonic waves is established, simulation verification is performed on the proposed control method and related algorithms, and correctness, practicability and reliability of the method are proved. The system is good in stability, low in implementation cost, simple and efficient in implementation structure, wide in applicability, capable of adapting to various complex power grid environments and relatively practical in engineering application value.

Description

Background Art

[0002] Voltage is an important indicator for measuring power quality. Ensuring that the user's voltage is close to the rated value is one of the basic tasks of power system operation adjustment. The operating voltage level of the power system depends on the reactive power balance of the power system. Sufficient reactive power is a necessary condition to ensure that the power system has a good operating voltage level. Static VAR compensator (SVG) is a new type of reactive power fast adjustment device developed in recent years. It can provide continuously changing inductive or capacitive reactive power, thereby achieving stable voltage control within a given range.

[0003] With the development of renewable energy generation, a single static VAR compensator (SVG) can hardly meet the requirements of reactive power compensation in high-power applications. Therefore, SVG often uses multiple machines in parallel to increase the reactive power compensation capacity, and uses a central controller or communication lines to distribute the compensation capacity. However, due to factors such as communication delay, the mutual communication between multiple parallel SVGs not only reduces the reliability of the system, but also deteriorates the dynamic response of the system, causing harm to the stable operation of the system. In addition, the implementation of the above control method also requires hardware modifications to the original single SVG, which greatly increases the cost and complexity of the system. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a power distribution droop control method and system for multiple parallel static VAR generators in view of the deficiencies in the above-mentioned prior art, which is used to solve the technical problem that the compensation power of each SVG cannot be flexibly distributed proportionally in the application scenario of multiple SVG parallel reactive compensation.

[0005] The present invention adopts the following technical solutions: A power distribution droop control method for multiple parallel static VAR generators comprises the following steps: The components of the grid voltage in the two-phase stationary coordinate system are , Calculate the grid angular frequency as the input of the phase-locked loop and Phase ; Use the grid angular frequency obtained and Phase And direct axis current reference value and quadrature axis current reference value , to conduct counter Transformation to obtain the current reference value in the two-phase stationary coordinate system and And input current inner loop; The power distribution droop coefficient of each static VAR generator is obtained by calculating the power distribution ratio ; Obtain the real-time machine-side current value of each static VAR generator in a two-phase static coordinate system , , obtain the real-time grid-connected current in the two-phase stationary coordinate system ; The power distribution droop coefficient Substitute it into the current loop controller deviation, and use the calculated result as the input of the current loop PR controller of each static VAR generator to control the output current of the equipment and realize the power distribution of parallel static VAR generators.

[0006] Preferably, the components of the grid voltage in the two-phase stationary coordinate system are , Specifically: Sampling the three-phase line voltage of the power grid and conduct Transformation, the components of the grid voltage in the two-phase stationary coordinate system are obtained , .

[0007] Preferably, The components of the grid voltage in the two-phase stationary coordinate system are obtained by transformation , as follows:

[0008] in, , , is the phase voltage at the grid connection point.

[0009] Preferably, the direct-axis current reference value and quadrature axis current reference value Specifically: Sample the DC side voltage and calculate the DC axis current reference value , set the quadrature axis current reference value .

[0010] Preferably, the power allocation coefficient of each static VAR generator is The calculation is as follows: Identify the SVG with the smallest rated current among multiple parallel SVGs; Determine the upper limit of the steady-state error of multiple parallel active filters; The upper limit of the steady-state error is set to the droop factor of the APF with the minimum rated current; Calculate the droop factor of each SVG in the multi-parallel system based on its rated current .

[0011] Preferably, the number n of parallel static VAR generators and the power distribution ratio are determined, and the output power of the kth static VAR generator is , the power distribution ratio is .

[0012] Preferably, the upper limit of the steady-state error of the multi-parallel active filter is less than 0.05.

[0013] Preferably, the droop coefficient The calculation is as follows:

[0014] in, is the minimum rated current in multiple parallel SVGs, is the upper limit of the steady-state error of the multi-parallel active filter, is the rated current of each SVG.

[0015] Preferably, the current loop controller deviation The calculation is as follows:

[0016] in, is the current reference value, is the actual current value, is the power allocation droop coefficient, Output current for each SVG port.

[0017] In a second aspect, an embodiment of the present invention provides a power distribution droop control system for multiple parallel static VAR generators, comprising: The calculation module converts the components of the grid voltage in the two-phase stationary coordinate system , Calculate the grid angular frequency as the input of the phase-locked loop and Phase ; The conversion module uses the grid angular frequency obtained and Phase And direct axis current reference value and quadrature axis current reference value , to conduct counter Transformation to obtain the current reference value in the two-phase stationary coordinate system and And input current inner loop; The coefficient module uses the power distribution ratio to calculate the power distribution droop coefficient of each static VAR generator. ; The distribution module obtains the real-time machine-side current value of each static VAR generator in the two-phase static coordinate system. , , obtain the real-time grid-connected current in the two-phase stationary coordinate system ; The power distribution droop coefficient Substitute it into the current loop controller deviation, and use the calculated result as the input of the current loop PR controller of each static VAR generator to control the output current of the equipment and realize the power distribution of parallel static VAR generators.

[0018] 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 power distribution droop of multiple parallel static VAR generators when executing the computer program.

[0019] In a fourth aspect, an embodiment of the present invention provides a computer-readable storage medium, comprising a computer program, which, when executed by a processor, implements the steps of the above-mentioned method for controlling power distribution droop of multiple parallel static VAR generators.

[0020] 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 the processor implements the steps of the above-mentioned method for controlling power distribution droop of multiple parallel static VAR generators when executing the computer program.

[0021] 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 method for controlling power distribution droop of multiple parallel static VAR generators.

[0022] Compared with the prior art, the present invention has at least the following beneficial effects: A power distribution droop control method for multiple parallel static VAR generators is provided. For a complex source-load interaction system including grid impedance, nonlinear load and static VAR generator, small signal dynamic characteristic models of key components are established respectively. And based on the established small signal dynamic models of each key component and the mutual coupling relationship, a parasitic feedback model of the whole system is established. Therefore, a detailed theoretical study and analysis of the reactive power compensation effect and stability of the whole system are carried out; by sampling the machine-side current, the machine-side current feedback is added to the current command of the traditional current inner loop control with a certain droop coefficient. So that the machine-side current response link is introduced into each single machine current inner loop control link. At the same time, for the proposed power distribution droop control method, compared with other current sharing methods, the parallel flexible current sharing effect of the static VAR generator is targetedly improved and the stability of the system is maintained; the existing implementation steps do not need to add new hardware equipment such as sensors on the basis of the original static VAR generator equipment. At the same time, the implementation steps are clear and concise, the implementation method is concise and efficient, and the increased calculation cost is small. Therefore, the present invention has good applicability and portability, and has high practical value in engineering practice. In addition, a corresponding system simulation model was built, and simulation experiments were carried out on the corresponding multi-parallel SVG reactive compensation scenario and the current sharing method effect of the method proposed in the present invention, verifying the effectiveness and reliability of the method proposed in the present invention.

[0023] Furthermore, as a typical grid-following converter, SVG needs to use a phase-locked loop and other synchronization links to achieve synchronization with the grid fundamental voltage; The components of the grid voltage in the two-phase stationary coordinate system are obtained by transformation , , which can be used as the input of the phase-locked loop to obtain the grid voltage angular frequency and phase, thereby maintaining the DC side voltage stability and achieving reactive power compensation.

[0024] Furthermore, it is necessary to control the SVG output current to maintain the DC voltage stability and realize the reactive power compensation function of the equipment by controlling the quadrature axis current to 0. The DC voltage outer loop is used to calculate the direct axis current reference value. and quadrature axis current reference value As the reference value of the current inner loop, it realizes reactive power compensation at the device access point while maintaining the DC side voltage stability.

[0025] Furthermore, the proposed droop coefficient power allocation method uses the sampled single-machine output current , by designing the droop coefficient , introduces a steady-state error to the system output current. A fundamental wave proportional resonant controller is adopted, whose gain at the grid frequency is infinite, so that the output fundamental wave current in the two-phase stationary coordinate system can be tracked without static error, and the power flexible distribution among multiple parallel static VAR generators can be realized and the harmonic compensation effect can be guaranteed.

[0026] Furthermore, in order to reduce the steady-state error of the output current and maintain the port characteristics and reactive power compensation effect of the device, the upper limit of the steady-state error of the multi-parallel active filter should be set to be less than 0.05.

[0027] Furthermore, sampling the machine-side current does not increase the number of sensors in the system. In the traditional static VAR compensation device, sampling the machine-side current is also required to control the output current of the device, while the traditional multi-parallel SVG control method. Therefore, the present invention uses the existing detection value of the system to adjust the overall characteristics of the system. This makes the present invention easy to implement without changing the hardware structure of the original system.

[0028] 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.

[0029] In summary, the method of the present invention has good stability, low implementation cost, simple and efficient implementation structure, wide applicability, can adapt to various complex power grid environments, and has relatively practical engineering application value.

[0030] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] 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.

[0032] Figure 1 It is a working schematic diagram of a multi-parallel static VAR generator system of the present invention; Figure 2 is a control block diagram of a specific implementation scheme of the present invention, wherein (a) is a detailed control block diagram, and (b) is a simplified control block diagram; FIG3 is a waveform diagram showing the effect of the current sharing control achieved by the proposed method in the dual SVG parallel reactive compensation working condition; wherein (a) is the droop coefficient The waveform of the SVG output current in the two-phase rotating coordinate system, (b) is the droop coefficient The waveform of the SVG output current in the two-phase rotating coordinate system, where the red waveform is the direct-axis current and the green waveform is the quadrature-axis current; Figure 4 A schematic diagram of a computer device provided by an embodiment of the present invention; Figure 5 The present invention is a block diagram of an electronic device provided according to an embodiment.

[0033] Among them: 60. Computer device; 61. Processor; 62. Memory; 63. Computer program; 600. Electronic device; 610. Processing unit; 620. Storage unit; 6201. Random access storage unit; 6202. Cache storage unit; 6203. Read-only storage unit; 6204. Program / utility; 6205. Program module; 630. Bus; 640. Display unit; 650. Input / output interface; 660. Network adapter; 700. External device. DETAILED DESCRIPTION

[0034] 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.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] 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.

[0039] 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.

[0040] 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.

[0041] The present invention provides a power distribution droop control method for multiple parallel static VAR generators, which enables SVG to automatically distribute compensation power when the grid current and the output current of each unit are detected; compared with previous studies, on the basis of improving the SVG capacity at the compensation point, the flexibility and distribution effect of the power distribution of each unit are significantly enhanced, while maintaining good dynamic response. The proposed scheme is suitable for N multiple parallel SVGs, with lower steady-state error and better reliability.

[0042] The present invention provides a control method for power distribution of multiple parallel static VAR generators based on the traditional control method of static VAR compensator; based on the mathematical relationship including the voltage outer loop of SVG control system, the system grid-connected current and the output current of SVG single machine, a series of theoretical analysis and derivation are carried out to analyze the power distribution problem of multiple parallel SVG system; based on the control theory and dynamic model of existing static VAR generator, the present invention proposes an output power distribution method, and achieves good power distribution effect by adding a machine-side current proportional control item to the traditional current inner loop control method of static VAR generator. Example 1 The present invention provides a power distribution droop control method for multiple parallel static VAR generators, comprising the following steps: S1, sampling grid three-phase line voltage and conduct Transformation, the components of the grid voltage in the two-phase stationary coordinate system are obtained , ; Use it as the phase-locked loop input to calculate the grid angular frequency and Phase ; The transformation is to convert the sampled three-phase voltage signal , and Converted into the components of the two-phase stationary coordinate system , ; Its conversion equation is:

[0043] The synchronous rotating coordinate system phase-locked loop can be used to calculate the grid angular frequency and Phase The phase-locked loop mainly extracts the phase difference between the grid voltage phase and the current phase-locked loop output through Clark transformation, and then realizes the closed-loop control of the phase difference through the PI controller. In this way, when the phase-locked loop control reaches a steady state, the phase difference between the grid voltage phase and the phase-locked loop output phase is closed-loop controlled to 0. This achieves effective tracking of the grid voltage phase.

[0044] S2, sample the DC side voltage, and input the difference between the actual value of the DC side voltage and the reference value into the PI controller to calculate the direct axis current reference value , set the quadrature axis current reference value ; S3, using the result obtained in step S1 , And the result of step S2 and , to conduct counter Transformation to obtain the current reference value in the two-phase stationary coordinate system and ; S4. Determine the number n of parallel static VAR generators and the power distribution ratio. Suppose the output power of the kth static VAR generator is , then the power allocation ratio is , the power distribution coefficient of each static VAR generator is obtained by calculating the power distribution ratio ; Power distribution droop coefficient of each single machine The steps to determine are: S401, identify the smallest rated current among multiple parallel SVGs ( ) S402, determine the upper limit of the steady-state error of the multi-parallel active filter ( ); According to the above analysis, this value is also the steady-state error when the SVG with the minimum rated current is running alone; it is usually set below 0.05; S403, setting the upper limit of the steady-state error to the droop coefficient of the APF with the minimum rated current; S404, according to the rated current of each SVG in the multi-parallel system ( ) to calculate its droop coefficient (δ j ).

[0045] Droop coefficient (δ j ) is calculated as follows:

[0046] S5. Obtain the real-time machine-side current value of each static VAR generator in the two-phase static coordinate system , obtain the real-time grid-connected current in the two-phase stationary coordinate system ; The power allocation droop coefficient determined in step S4 Substitute into the current loop controller deviation solution formula In the step S4, the calculated result is used as the input of the current loop PR controller of each static VAR generator to control the output current of the device, so that the power distribution of the parallel static VAR generators desired in step S4 can be achieved.

[0047] 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".

[0048] Example 2 The present invention provides a power distribution droop control system for multiple parallel static VAR generators, which can be used to implement the above-mentioned power distribution droop control method for multiple parallel static VAR generators. Specifically, the power distribution droop control system for multiple parallel static VAR generators includes a calculation module, a transformation module, a coefficient module and a distribution module.

[0049] Among them, the calculation module converts the components of the grid voltage in the two-phase stationary coordinate system into , Calculate the grid angular frequency as the input of the phase-locked loop and Phase ; The conversion module uses the obtained grid angular frequency and Phase And direct axis current reference value and quadrature axis current reference value , to conduct counter Transformation to obtain the current reference value in the two-phase stationary coordinate system and And input current inner loop; The coefficient module uses the power distribution ratio to calculate the power distribution droop coefficient of each static VAR generator. ; The distribution module obtains the real-time machine-side current value of each static VAR generator in the two-phase static coordinate system. , , obtain the real-time grid-connected current in the two-phase stationary coordinate system ; The power distribution droop coefficient Substitute it into the current loop controller deviation, and use the calculated result as the input of the current loop PR controller of each static VAR generator to control the output current of the equipment and realize the power distribution of parallel static VAR generators.

[0050] Example 3 The present invention provides a terminal device, 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 processors (GPU), tensor processors (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 power distribution droop control method of multiple parallel static VAR generators, including: The components of the grid voltage in the two-phase stationary coordinate system are , Calculate the grid angular frequency as the input of the phase-locked loop and Phase ; Use the grid angular frequency obtained and Phase And direct axis current reference value and quadrature axis current reference value , to conduct counter Transformation to obtain the current reference value in the two-phase stationary coordinate system and And input the current inner loop; use the power distribution ratio to calculate the power distribution droop coefficient of each static VAR generator ; Obtain the real-time machine-side current value of each static VAR generator in the two-phase static coordinate system , , obtain the real-time grid-connected current in the two-phase stationary coordinate system ; The power distribution droop coefficient Substitute it into the current loop controller deviation, and use the calculated result as the input of the current loop PR controller of each static VAR generator to control the output current of the equipment and realize the power distribution of parallel static VAR generators.

[0051] See also Figure 4 , 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 power distribution droop control method of multiple parallel static VAR generators 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 power distribution droop control system of multiple parallel static VAR generators in the embodiment are implemented. To avoid repetition, it is not described one by one here.

[0052] 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 Figure 4 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.

[0053] 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 the processor may be any conventional processor, etc.

[0054] 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 media card (SMC), a secure digital (SD) card, a flash card, etc., equipped on the computer device 60.

[0055] 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.

[0056] See also Figure 5 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.

[0057] 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 2 Follow the steps shown in .

[0058] The storage unit 620 may include a readable medium in the form of a volatile storage unit, such as a random access memory unit (RAM) 6201 and / or a cache memory unit 6202 , and may further include a read-only memory unit (ROM) 6203 .

[0059] 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.

[0060] 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.

[0061] 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.

[0062] Example 4 The present invention also provides a storage medium, specifically a computer-readable storage medium (Memory), which is a memory device in a terminal device for storing programs and data. It is understandable that the computer-readable storage medium here can include both built-in storage media in the terminal device and extended storage media supported by the terminal device, and can be any tangible medium containing or storing a program, which can be used by an instruction execution system, device or device or used in combination with it. 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 more specific examples (non-exhaustive list) of the computer-readable storage medium here include: an electrical connection with one or more wires, a portable disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a portable compact disk read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the above.

[0063] Computer readable storage media also include data signals propagated in baseband or as part of a carrier wave, which carry readable program codes. Such propagated data signals can take a variety of forms, including but not limited to electromagnetic signals, optical signals, or any suitable combination of the above. The readable storage medium can also be any readable medium other than a readable storage medium, which can send, propagate, or transmit a program for use by or in conjunction with an instruction execution system, device, or device. The program code contained on the readable storage medium can be transmitted using any appropriate medium, including but not limited to wireless, wired, optical cable, RF, etc., or any suitable combination of the above.

[0064] Program code for performing the operations of the present invention may be written in any combination of one or more programming languages, including object-oriented programming languages ​​such as Java, C++, etc., and conventional procedural programming languages ​​such as "C" or similar programming languages. The program code may be executed entirely on the user computing device, partially on the user device, as a separate software package, partially on the user computing device and partially on a remote computing device, or entirely on a remote computing device or server. In the case of a remote computing device, the remote computing device may be connected to the user computing device through any type of network, including a local area network (LAN) or a wide area network (WAN), or may be connected to an external computing device (e.g., through the Internet using an Internet service provider).

[0065] The processor may load and execute one or more instructions stored in a computer-readable storage medium to implement the corresponding steps of the power distribution droop control method for multiple parallel static VAR generators in the above embodiment; the processor may load and execute the following steps of one or more instructions in the computer-readable storage medium: The components of the grid voltage in the two-phase stationary coordinate system are , Calculate the grid angular frequency as the input of the phase-locked loop and Phase ; Use the grid angular frequency obtained and Phase And direct axis current reference value and quadrature axis current reference value , to conduct counter Transformation to obtain the current reference value in the two-phase stationary coordinate system and And input the current inner loop; use the power distribution ratio to calculate the power distribution droop coefficient of each static VAR generator ; Obtain the real-time machine-side current value of each static VAR generator in the two-phase static coordinate system , , obtain the real-time grid-connected current in the two-phase stationary coordinate system ; The power distribution droop coefficient Substitute it into the current loop controller deviation, and use the calculated result as the input of the current loop PR controller of each static VAR generator to control the output current of the equipment and realize the power distribution of parallel static VAR generators.

[0066] 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.

[0067] See also Figure 1 The specific application scenarios of the reactive power distribution method for multi-machine parallel static VAR generator are: The grid supplies power to the nonlinear load, the static VAR generator is connected in parallel to the front end of the nonlinear load, and the grid connection point voltage is sampled. , grid current The fundamental current reference value is generated through the DC voltage control loop , and set , and then the current controller generates the output current of each SVG unit , compensation of harmonic current The static VAR generator is input into the grid to compensate for the reactive power generated by the nonlinear load. The proposed droop coefficient power allocation method uses the sampled single machine output current , by designing the droop coefficient , introduces a steady-state error to the system output current. At this time, the output current transfer function of a single machine is:

[0068] in, .

[0069] when The fundamental wave proportional resonant controller is used, and its gain at the grid frequency is infinite, so that the output fundamental wave current in the two-phase stationary coordinate system can be tracked without static error. For two different parallel SVGs, the output current proportional relationship is:

[0070] Flexible power distribution among multiple parallel static VAR generators is achieved and harmonic compensation effect is guaranteed.

[0071] See also Figure 2 , the control block diagram of the static VAR generator using the current sharing method based on the droop coefficient is: Controlled by DC voltage Subtract grid-side current The compensation signal is obtained by multiplying the machine-side current by the droop coefficient and then passing through the current control link. , the output voltage of the active power filter is controlled through PWM modulation. Sampling the actual output current As negative feedback, it is input into the current command. Analyzing this control block diagram, it can be seen that this control method not only realizes the current sharing control of multiple parallel SVGs, but also does not affect the original current loop fundamental wave gain, nor does it add oscillation paths to other subharmonics, thus ensuring the stability of the system.

[0072] Please refer to Figure 3. The simulation model is a parallel compensation condition of two static VAR generators. The nonlinear load in the simulation is a resistive and inductive load. The reactive power distribution droop coefficient is added at 0.5s, where (a) is the droop coefficient. The waveform of the SVG output current in the two-phase rotating coordinate system, (b) is the droop coefficient The waveform of the SVG output current in the two-phase rotating coordinate system, where the red waveform is the direct axis current and the green waveform is the quadrature axis current. From the simulation results Figure 3 (a) and (b), it can be seen that after adding the droop coefficient, the steady-state output power of the two machines meets = , which proves that the method of the present invention can effectively realize the current sharing control of multiple parallel SVGs, and the system can maintain the reactive power compensation effect to meet the requirements.

[0073] In summary, the present invention provides a droop control method and system for power distribution of multiple parallel static VAR generators. Under the control method of the original static VAR generator, a steady-state error disturbance is introduced to the output current of each machine in the parallel SVG system through the droop coefficient, thereby realizing proportional and flexible distribution of the output power. For nonlinear loads, the reactive compensation capacity can be generated under the premise of realizing reactive power compensation at the grid connection point. At the same time, a simulation model of reactive power compensation of multiple parallel static VAR generators is built, and the proposed control method and related algorithms are simulated and verified, which proves the correctness, practicality and reliability of the method. The present invention has good stability, low implementation cost, simple and efficient implementation structure, wide applicability, and can adapt to various complex power grid environments, and has a relatively practical engineering application value.

[0074] 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.

[0075] 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.

[0076] 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.

[0077] 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.

[0078] 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.

[0079] 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.

[0080] 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.

[0081] 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.

[0082] 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.

[0083] 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.

[0084] 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 power distribution droop control method for multiple parallel static VAR generators, characterized in that: The following steps are involved: The components of the grid voltage in the two-phase stationary coordinate system are , Calculate the grid angular frequency as the input of the phase-locked loop and Phase ; Use the grid angular frequency obtained and Phase And direct axis current reference value and quadrature axis current reference value , to conduct counter Transformation to obtain the current reference value in the two-phase stationary coordinate system and And input current inner loop; The power distribution droop coefficient of each static VAR generator is obtained by calculating the power distribution ratio ; Obtain the real-time machine-side current value of each static VAR generator in a two-phase static coordinate system , , obtain the real-time grid-connected current in the two-phase stationary coordinate system ; The power distribution droop coefficient Substitute it into the current loop controller deviation, and use the calculated result as the input of the current loop PR controller of each static VAR generator to control the output current of the equipment and realize the power distribution of parallel static VAR generators.

2. The power distribution droop control method of multiple parallel static VAR generators according to claim 1, characterized in that: Components of the grid voltage in a two-phase stationary coordinate system , Specifically: Sampling the three-phase line voltage of the power grid and conduct Transformation, the components of the grid voltage in the two-phase stationary coordinate system are obtained , .

3. The power distribution droop control method of multiple parallel static VAR generators according to claim 2, characterized in that: The components of the grid voltage in the two-phase stationary coordinate system are obtained by transformation , as follows: in, , , is the phase voltage at the grid connection point.

4. The power distribution droop control method of multiple parallel static VAR generators according to claim 1, characterized in that: Direct axis current reference value and quadrature axis current reference value Specifically: Sample the DC side voltage and calculate the DC axis current reference value , set the quadrature axis current reference value .

5. The power distribution droop control method of multiple parallel static VAR generators according to claim 1, characterized in that: Power distribution coefficient of each static VAR generator The calculation is as follows: Identify the SVG with the smallest rated current among multiple parallel SVGs; Determine the upper limit of the steady-state error of multiple parallel active filters; The upper limit of the steady-state error is set to the droop factor of the APF with the minimum rated current; Calculate the droop factor of each SVG in the multi-parallel system based on its rated current .

6. The power distribution droop control method of multiple parallel static VAR generators according to claim 5, characterized in that: Determine the number of parallel static VAR generators n and the power distribution ratio. Suppose the output power of the kth static VAR generator is , the power distribution ratio is .

7. The power distribution droop control method of multiple parallel static VAR generators according to claim 5, characterized in that: The upper limit of the steady-state error of the multi-parallel active filter is less than 0.

05.

8. The power distribution droop control method of multiple parallel static VAR generators according to claim 5, characterized in that: Droop coefficient The calculation is as follows: in, is the minimum rated current in multiple parallel SVGs, is the upper limit of the steady-state error of the multi-parallel active filter, is the rated current of each SVG.

9. The power distribution droop control method of multiple parallel static VAR generators according to claim 1, characterized in that: Current loop controller deviation The calculation is as follows: in, is the current reference value, is the actual current value, is the power allocation droop coefficient, Output current for each SVG port.

10. A power distribution droop control system for multiple parallel static VAR generators, characterized in that: include: The calculation module converts the components of the grid voltage in the two-phase stationary coordinate system , Calculate the grid angular frequency as the input of the phase-locked loop and Phase ; The conversion module uses the grid angular frequency obtained and Phase And direct axis current reference value and quadrature axis current reference value , to conduct counter Transformation to obtain the current reference value in the two-phase stationary coordinate system and ; The coefficient module uses the power distribution ratio to calculate the power distribution droop coefficient of each static VAR generator. ; The distribution module obtains the real-time machine-side current value of each static VAR generator in the two-phase static coordinate system. , , obtain the real-time grid-connected current in the two-phase stationary coordinate system ; The power distribution droop coefficient Substitute it into the current loop controller deviation, and use the calculated result as the input of the current loop PR controller of each static VAR generator to control the output current of the equipment and realize the power distribution of parallel static VAR generators.

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