CN115586717A - Method and device for constructing modular multilevel converter - Google Patents
Method and device for constructing modular multilevel converter Download PDFInfo
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Abstract
The invention provides a method and a device for constructing a modular multilevel converter, wherein the method comprises the following steps: constructing a flexible direct current transmission/distribution system equivalent circuit based on the converter; establishing a structure diagram of a P-U-I controller transfer function of the converter according to the equivalent circuit and the feedback logic of the P-U-I controller; the transfer function and the control parameter of each link of the P-U-I controller in the structure diagram are determined to configure the P-U-I controller.
Description
Technical Field
The invention relates to the technical field of flexible direct current transmission/distribution systems, in particular to a method and a device for constructing a modular multilevel converter.
Background
In recent years, the flexible direct current power transmission and distribution technology has strong technical advantages in the aspects of improving the stability of a power system, improving the transmission power and efficiency of a line, increasing the dynamic reactive power reserve of the system, increasing the power supply capacity and radius of the system, improving the quality of electric energy, reducing electromagnetic radiation, interconnecting asynchronous power grids, supplying power to isolated island passive loads, increasing new energy consumption and the like.
The core of the flexible direct current transmission technology lies in the control of an MMC (Modular Multilevel Converter), the control mode of the flexible direct current transmission/distribution system based on the MMC at present mainly comprises master-slave control, voltage margin and droop control, and a controller adopted by the MMC mainly comprises a constant voltage controller, a constant power controller, a droop controller, a margin controller and a P-U-I controller (an inner and outer double-ring voltage power controller). The availability of the controller is verified in a simulation system, but the method for modeling the transfer function of the controller and the parameter selection are not well solved, the selection of the controller parameter is usually obtained by repeatedly testing and modifying in the simulation system, a large amount of debugging time is needed, and a theoretical basis is lacked.
Disclosure of Invention
The invention aims to provide a construction method of a modular multilevel converter, which can quickly and accurately determine the transfer function and the control parameters of a P-U-I controller of the converter so as to improve the construction efficiency of the converter. Another object of the present invention is to provide a modular multilevel converter constructing apparatus. It is a further object of this invention to provide such a computer apparatus. It is a further object of this invention to provide such a readable medium.
In order to achieve the above object, in one aspect, the present invention discloses a method for constructing a modular multilevel converter, including:
constructing a flexible direct current transmission/distribution system equivalent circuit based on the converter;
establishing a structure diagram of a P-U-I controller transfer function of the current converter according to the equivalent circuit and the feedback logic of the P-U-I controller;
and determining transfer functions and control parameters of each link of the P-U-I controller in the structure diagram so as to configure the P-U-I controller.
Preferably, the constructing of the converter-based flexible dc power transmission/distribution system equivalent circuit specifically includes:
and simplifying the flexible direct current transmission/distribution system into a circuit topology in which the MMC converter station is respectively connected with the direct current side virtual equivalent resistor, the rest converter stations on the direct current circuit and the equivalent direct current capacitor of the interface converter to obtain the equivalent circuit.
Preferably, the establishing a structure diagram of a transfer function of the P-U-I controller of the inverter according to the equivalent circuit and the feedback logic of the P-U-I controller specifically includes:
respectively constructing an active branch adopting a P-U-I controller, a reactive branch adopting the P-U-I controller and a coupling relation between the active branch and the reactive branch according to the equivalent circuit;
and establishing a structure diagram of the transfer function of the P-U-I controller of the converter according to the feedback logic of the power, voltage and current loops of the P-U-I controller.
Preferably, the determining the transfer function and the control parameter of each link of the P-U-I controller in the structure diagram specifically includes:
determining a transfer function of each link of the P-U-I controller;
determining transfer function parameters of each link of the P-U-I controller;
and obtaining control parameters of each link of the P-U-I controller according to the primary electrical parameters and the control parameters of the flexible direct current transmission/distribution system.
Preferably, the determining a transfer function of each link of the P-U-I controller specifically includes:
determining a transfer function structure diagram of the MMC current converter;
determining a voltage loop feedback link transfer function;
and determining a transfer function of a power loop feedback link.
Preferably, the determining the transfer function parameters of each link of the P-U-I controller specifically includes:
determining a transfer function of a PI controller of each link of the P-U-I controller;
determining an open-loop transfer function and a closed-loop transfer function of a power loop in the flexible direct current transmission/distribution system;
and obtaining parameters of the P-U-I controller according to preset power loop parameters and the open-loop transfer function and the closed-loop transfer function of the power loop to obtain transfer function parameters.
Preferably, the determining the open-loop transfer function and the closed-loop transfer function of the power loop in the flexible dc transmission/distribution system specifically includes:
determining an open-loop transfer function and a closed-loop transfer function of a current loop in the flexible direct current transmission/distribution system, and further obtaining the open-loop transfer function and the closed-loop transfer function of the voltage loop;
and obtaining an open-loop transfer function and a closed-loop transfer function of the power ring according to the parameter setting value of the PI controller of the voltage ring and the open-loop transfer function and the closed-loop transfer function of the voltage ring.
The invention also discloses a modular multilevel converter construction device, which comprises the following components:
the equivalent circuit building module is used for building an equivalent circuit of the flexible direct current transmission/distribution system based on the converter;
the controller structure chart building module is used for building a structure chart of a P-U-I controller transfer function of the converter according to the equivalent circuit and the feedback logic of the P-U-I controller;
and the parameter solving module is used for determining a transfer function and a control parameter of each link of the P-U-I controller in the structure diagram so as to configure the P-U-I controller.
The invention also discloses a computer device comprising a memory, a processor and a computer program stored on the memory and executable on the processor,
the processor, when executing the program, implements the method as described above.
The invention also discloses a computer-readable medium, having stored thereon a computer program,
which program, when executed by a processor, carries out the method as described above.
The construction method of the modular multilevel converter constructs a flexible direct current transmission/distribution system equivalent circuit based on the converter; establishing a structure diagram of a P-U-I controller transfer function of the current converter according to the equivalent circuit and the feedback logic of the P-U-I controller; and determining the transfer function and the control parameter of each link of the P-U-I controller in the structure chart. Therefore, the invention provides a transfer function modeling and control parameter selection method for a modular multilevel converter adopting a P-U-I controller, which can accurately establish the transfer function of the P-U-I controller, quickly determine the control parameters of the controller and ensure the stability of the controller.
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In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
Fig. 1 shows a flow chart of a specific embodiment of a method for constructing a modular multilevel converter according to the present invention;
fig. 2 is a schematic diagram of an equivalent circuit of a specific embodiment of the method for constructing the modular multilevel converter;
fig. 3 shows a flow chart of a specific embodiment S200 of the method for constructing a modular multilevel converter according to the present invention;
fig. 4 is a schematic diagram of a P-U-I controller according to a specific embodiment of the method for constructing a modular multilevel converter of the present invention;
fig. 5 is a schematic diagram showing a P-U-I controller transfer function according to a specific embodiment of the method for constructing a modular multilevel converter of the present invention;
fig. 6 shows a flow chart of a specific embodiment S300 of the method for constructing a modular multilevel converter according to the present invention;
fig. 7 shows a flowchart of a method for constructing a modular multilevel converter according to an embodiment S310 of the present invention;
FIG. 8 is a schematic diagram showing transfer functions of links of a P-U-I controller according to a specific embodiment of the method for constructing a modular multilevel converter of the present invention;
fig. 9 shows a flowchart of a specific embodiment S320 of the method for constructing a modular multilevel converter according to the present invention;
fig. 10 is a block diagram of an embodiment of a modular multilevel converter building arrangement according to the invention;
FIG. 11 illustrates a schematic block diagram of a computer device suitable for use in implementing embodiments of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
According to one aspect of the invention, the embodiment discloses a modular multilevel converter construction method. As shown in fig. 1, in this embodiment, the method includes:
s100: and constructing a flexible direct current transmission/distribution system equivalent circuit based on the converter.
S200: and establishing a structure diagram of the P-U-I controller transfer function of the converter according to the equivalent circuit and the feedback logic of the P-U-I controller.
S300: and determining transfer functions and control parameters of links of the P-U-I controller in the structural diagram so as to configure the P-U-I controller.
The construction method of the modular multilevel converter constructs a flexible direct current transmission/distribution system equivalent circuit based on the converter; establishing a structure diagram of a P-U-I controller transfer function of the converter according to the equivalent circuit and the feedback logic of the P-U-I controller; and determining the transfer function and the control parameter of each link of the P-U-I controller in the structure chart. Therefore, the invention provides a method for modeling the transfer function and selecting the control parameters of the modular multilevel converter adopting the P-U-I controller, which can accurately establish the transfer function of the P-U-I controller of the MMC, quickly determine the control parameters of the controller and ensure the stability of the controller.
In a preferred embodiment, the S100 constructing the converter-based flexible dc power transmission/distribution system equivalent circuit specifically includes:
s110: and simplifying the flexible direct current transmission/distribution system into a circuit topology in which the MMC converter station is respectively connected with the direct current side virtual equivalent resistor, the rest converter stations on the direct current circuit and the equivalent direct current capacitor of the interface converter to obtain the equivalent circuit.
It can be understood that the flexible direct current transmission/distribution system mostly adopts direct current overhead lines and direct current cable lines, and the line impedance is small. Therefore, the line impedance can be ignored, and the flexible direct current transmission/distribution system can be approximately simplified into a circuit topology in which the MMC converter station is connected with the direct current side virtual equivalent resistor Req, the rest converter stations on the direct current line, and the equivalent direct current capacitor Ceq of the interface converter, so as to obtain the equivalent circuit, as shown in fig. 2.
In a specific example, in the equivalent circuit of the flexible direct current transmission/distribution system, according to the law of conservation of energyThe sum of the capacitance energy of all sub-modules of the MMC bridge arm and an equivalent direct current capacitor C equivalent to the direct current side of the MMC bridge arm MMC Is the same, thus obtaining C MMC Comprises the following steps:
the virtual equivalent resistance on the direct current side is as follows:
the virtual equivalent capacitance C on the direct current side is as follows:
C＝C eq +C MMC (3)
wherein N is the number of MMC single bridge arm sub-modules, C 0 For MMC individual sub-module capacitors, U c For MMC single sub-module capacitive voltage, U dcN Rated DC voltage for MMC, P N Rated active power for MMC.
In a preferred embodiment, as shown in fig. 3, the step S200 of establishing a structure diagram of a P-U-I controller transfer function of the inverter according to the equivalent circuit and a feedback logic of the P-U-I controller specifically includes:
s210: and respectively constructing an active branch adopting a P-U-I controller, a reactive branch adopting the P-U-I controller and a coupling relation between the active branch and the reactive branch according to the equivalent circuit.
S220: and establishing a structure diagram of the transfer function of the P-U-I controller of the converter according to the feedback logic of the power, voltage and current loops of the P-U-I controller.
It can be understood that the flexible dc power transmission/distribution system generally includes two branches, one branch is an active branch and uses a P-U-I controller, the other branch is a reactive branch and uses a reactive controller, and the two branches have a coupling relation in the inner loop current portion, and fig. 4 shows a structural diagram of the two branches of the P-U-I controller in a specific example. In FIG. 4, P ref 、Q ref 、U dcref 、I ref 、U dcrefmax 、U dcrefmin 、P、Q、U dc 、i d 、i q 、U d 、U q 、V d 、V q Respectively represents an active power reference value, a reactive power reference value, a direct current voltage reference value, a current reference value, a direct current upper limit value, a direct current lower limit value, actual active power, actual reactive power, actual direct current voltage, an alternating current active component, an alternating current reactive component, an alternating current voltage d-axis component, an alternating current voltage q-axis component, an active regulation instruction and a reactive regulation instruction.
And the PI controllers respectively represent an active power loop, a direct current voltage loop, an active current loop, a reactive power loop and a reactive current loop.
Further, a block diagram of the transfer function of the P-U-I controller may be built based on the feedback logic and position of the power, voltage and current loops of the P-U-I controller, as shown in FIG. 5.
In a preferred embodiment, as shown in fig. 6, the step S300 of determining the transfer function and the control parameter of each link of the P-U-I controller in the structural diagram specifically includes:
s310: and determining the transfer function of each link of the P-U-I controller.
S320: and determining the transfer function parameters of each link of the P-U-I controller.
S330: and obtaining control parameters of each link of the P-U-I controller according to the primary electrical parameters and the control parameters of the flexible direct current transmission/distribution system.
Specifically, the expression of the transfer function of each link of the P-U-I controller can be obtained based on the constructed structure diagram of the transfer function of the P-U-I controller, the parameters in the transfer function of each link of the P-U-I controller can be further determined according to the operation principle of the system, preset system parameters and other information, the transfer function parameters of each link of the P-U-I controller can be further obtained, and then the control parameters of each link of the P-U-I controller can be obtained by inputting the primary electrical parameters and the control parameters of the system into the transfer function parameters.
In a preferred embodiment, as shown in fig. 7, the determining, by S310, the transfer function of each link of the P-U-I controller specifically includes:
s311: and determining a transfer function structure diagram of the MMC converter.
S312: and determining a voltage loop feedback link transfer function.
S313: and determining a transfer function of a power loop feedback link.
Specifically, as shown in fig. 8, determining the transfer function of each link of the P-U-I controller in the structure diagram may include the following steps:
(1) The transfer function of the MMC converter is determined.
Because MMC transverter adopts the decoupling control system structure of electric current inner loop, consider the delay effect of PWM control, introduce an inertia link as approximate equivalence to MMC transverter's transfer function can be expressed as after the current decoupling:
in the formula, T PWM Is the average delay time of the PWM switching, where its statistical average is taken: t is PWM ＝T s /2，T s And in the PWM switching period, R is MMC equivalent resistance, L is MMC equivalent inductance, and s is a differential operator.
(2) Determining voltage loop feedback link transfer function G 4 (s)。
According to Kirchhoff's Current Law (KCL) and system power balance, we can obtain:
U s i d ＝U dc i dc ≈U dcN i dc (6)
wherein Us is MMC AC side voltage, U dc Is the system DC side voltage i dc Is MMC direct-current side bus outlet current.
When formula (5) is substituted for formula (6), it is possible to obtain:
(3) Determining a power loop feedback link transfer function G 5 (s)。
In dq rotation coordinate system, selecting d axis coincident with A, when i is d Is a component of AC power i q Is an alternating current reactive component, so that:
where P(s) is the expression of the power function P (t) in the complex frequency domain, i d (s) is the AC active component i d (t) the representation of the function in the complex frequency domain.
In a preferred embodiment, as shown in fig. 9, the determining, in S320, transfer function parameters of each link of the P-U-I controller specifically includes:
s321: and determining the transfer function of the PI controller of each link of the P-U-I controller.
S322: an open loop transfer function and a closed loop transfer function of a power loop in a flexible direct current transmission/distribution system are determined.
S323: and obtaining parameters of the P-U-I controller according to preset power loop parameters and the open-loop transfer function and the closed-loop transfer function of the power loop to obtain transfer function parameters.
Preferably, the determining of the open-loop transfer function and the closed-loop transfer function of the power loop in the flexible dc power transmission/distribution system in S322 may specifically include: determining an open-loop transfer function and a closed-loop transfer function of a current loop in the flexible direct current transmission/distribution system, and further obtaining the open-loop transfer function and the closed-loop transfer function of the voltage loop; and obtaining an open-loop transfer function and a closed-loop transfer function of the power ring according to the parameter setting value of the PI controller of the voltage ring and the open-loop transfer function and the closed-loop transfer function of the voltage ring.
Specifically, the transfer function of the PI controller in each link of the P-U-I controller can be expressed as:
wherein, the first and the second end of the pipe are connected with each other,
and
PI controllers respectively representing active power loop, DC voltage loop and active current loop, K 1 、K 2 And K 3 Are respectively the proportionality coefficient, tau 1 、τ 2 And τ 3 Is a time coefficient.
The open loop transfer function of the current loop can be expressed as:
the zero point of the correction device is led to be cancelled with the great inertia pole in the original system, and the current inner loop system is a typical I-type system. According to the optimal setting method of a typical I-type system, the parameter setting value of the PI controller of the obtained current inner ring is as follows:
under PWM control, since
The higher order terms can be ignored.After the above parameters are set, the closed loop transfer function of the current loop can be expressed as:
according to equation (7), the open-loop transfer function of the voltage loop can be obtained as:
by eliminating the optimal tuning method of a typical type I system by zero pole pairs, the closed loop transfer function of the voltage ring can be expressed as:
the parameter setting value of the PI controller of the voltage loop is as follows:
thus, the open-loop transfer function and the closed-loop transfer function of the power loop can be expressed as:
wherein, K 1 Comprises the following steps:
in this particular example, the integration time of the power loop is often used to suppress harmonic effects caused by PWM controlNumeric retrieval of tau 1 ＝10T PWM At the same time, the amplitude-frequency characteristic of the power loop closed loop transfer function should cross the 0dB line at a slope of-20 dB/sec. The two handover frequencies of the system are ω from equation (19) 1 ＝1/τ 1 And omega 2 ＝1/4R eq T PWM . Thus, the crossover frequency may be taken to be ω c ＝1/8R eq T PWM And obtaining the parameters of the transfer function. Furthermore, the primary electrical parameters and the control parameters of the actual flexible direct current transmission/distribution system are substituted into each formula in the process of solving the parameters of the transfer function, and the control parameters of each link of the P-U-I controller can be quickly calculated.
The invention provides a scheme for modeling transfer functions and selecting control parameters of a modular multilevel converter adopting a P-U-I controller aiming at the defect that the P-U-I controller of the traditional MMC lacks a transfer function modeling method and a parameter selecting method, is suitable for parameter design of the MMC adopting the P-U-I controller in various voltage levels, has the characteristics of rapidness and reliability, and can guide parameter setting and optimization of the actual P-U-I controller; the stability and the control effect of the P-U-I controller can be further analyzed through the transfer function.
Based on the same principle, the embodiment also discloses a modular multilevel converter construction device. In this embodiment, as shown in fig. 10, the apparatus includes an equivalent circuit building module 11, a controller structure diagram building module 12, and a parameter solving module 13.
The equivalent circuit building module 11 is configured to build an equivalent circuit of the converter-based flexible dc power transmission/distribution system.
And the controller structure diagram building module 12 is used for building a structure diagram of a P-U-I controller transfer function of the converter according to the equivalent circuit and the feedback logic of the P-U-I controller.
The parameter solving module 13 is configured to determine a transfer function and a control parameter of each link of the P-U-I controller in the structure diagram, so as to configure the P-U-I controller.
In a preferred embodiment, the equivalent circuit constructing module 11 is specifically configured to simplify the flexible dc power transmission/distribution system into a circuit topology in which the MMC converter station is respectively connected to the dc-side virtual equivalent resistor, the equivalent dc capacitors of the remaining converter stations on the dc line, and the interface converter, so as to obtain the equivalent circuit.
In a preferred embodiment, the controller structure diagram constructing module 12 is specifically configured to respectively construct an active branch and a reactive branch of a P-U-I controller, and a coupling relationship between the active branch and the reactive branch according to the equivalent circuit; and establishing a structure diagram of the transfer function of the P-U-I controller of the converter according to the feedback logic of the power, voltage and current loops of the P-U-I controller.
In a preferred embodiment, the parameter solving module 13 is specifically configured to determine a transfer function of each link of the P-U-I controller; determining transfer function parameters of each link of the P-U-I controller; and obtaining control parameters of each link of the P-U-I controller according to the primary electrical parameters and the control parameters of the flexible direct current transmission/distribution system.
In a preferred embodiment, the parameter solving module 13 is specifically configured to determine a structure diagram of a transfer function of the MMC converter; determining a voltage loop feedback link transfer function; and determining a transfer function of a power loop feedback link.
In a preferred embodiment, the parameter solving module 13 is specifically configured to determine a transfer function of a PI controller of each link of the P-U-I controller; determining an open-loop transfer function and a closed-loop transfer function of a power loop in the flexible direct current transmission/distribution system; and obtaining parameters of the P-U-I controller according to the preset power loop parameters and the open-loop transfer function and the closed-loop transfer function of the power loop to obtain transfer function parameters.
In a preferred embodiment, the parameter solving module 13 is specifically configured to determine an open-loop transfer function and a closed-loop transfer function of a current loop in the flexible direct current transmission/distribution system, so as to obtain an open-loop transfer function and a closed-loop transfer function of a voltage loop; and obtaining an open-loop transfer function and a closed-loop transfer function of the power ring according to the parameter setting value of the PI controller of the voltage ring and the open-loop transfer function and the closed-loop transfer function of the voltage ring.
Since the principle of solving the problem of the device is similar to the method, the implementation of the device can refer to the implementation of the method, and details are not described herein.
The systems, apparatuses, modules or units described in the above embodiments may be specifically implemented by a computer chip or an entity, or implemented by a product with certain functions. A typical implementation device is a computer device, which may be, for example, a personal computer, laptop computer, cellular telephone, camera phone, smart phone, personal digital assistant, media player, navigation device, email device, game console, tablet computer, wearable device, or a combination of any of these devices.
In a typical example, the computer device specifically comprises a memory, a processor and a computer program stored on the memory and executable on the processor, the processor implementing the method performed by the client as described above when executing the program, or the processor implementing the method performed by the server as described above when executing the program.
Referring now to FIG. 11, shown is a schematic diagram of a computer device 600 suitable for use in implementing embodiments of the present application.
As shown in fig. 11, the computer apparatus 600 includes a Central Processing Unit (CPU) 601 that can perform various appropriate jobs and processes according to a program stored in a Read Only Memory (ROM) 602 or a program loaded from a storage section 608 into a Random Access Memory (RAM)) 603. In the RAM603, various programs and data necessary for the operation of the system 600 are also stored. The CPU601, ROM602, and RAM603 are connected to each other via a bus 604. An input/output (I/O) interface 605 is also connected to bus 604.
The following components are connected to the I/O interface 605: an input portion 606 including a keyboard, a mouse, and the like; an output portion 607 including a Cathode Ray Tube (CRT), a liquid crystal feedback (LCD), and the like, and a speaker and the like; a storage section 608 including a hard disk and the like; and a communication section 609 including a network interface card such as a LAN card, a modem, or the like. The communication section 609 performs communication processing via a network such as the internet. The driver 610 is also connected to the I/O interface 606 as needed. A removable medium 611 such as a magnetic disk, an optical disk, a magneto-optical disk, a semiconductor memory, or the like is mounted on the drive 610 as necessary, so that a computer program read out therefrom is mounted as necessary on the storage section 608.
In particular, according to an embodiment of the present invention, the processes described above with reference to the flowcharts may be implemented as computer software programs. For example, embodiments of the invention include a computer program product comprising a computer program tangibly embodied on a machine-readable medium, the computer program comprising program code for performing the method illustrated in the flow chart. In such an embodiment, the computer program may be downloaded and installed from a network through the communication section 609, and/or installed from the removable medium 611.
Computer-readable media, including both permanent and non-permanent, removable and non-removable media, may implement the information storage by any method or technology. The information may be computer readable instructions, data structures, modules of a program, or other data. Examples of computer storage media include, but are not limited to, phase change memory (PRAM), static Random Access Memory (SRAM), dynamic Random Access Memory (DRAM), other types of Random Access Memory (RAM), read Only Memory (ROM), electrically Erasable Programmable Read Only Memory (EEPROM), flash memory or other memory technology, compact disc read only memory (CD-ROM), digital Versatile Disks (DVD) or other optical storage, magnetic cassettes, magnetic tape magnetic disk storage or other magnetic storage devices, or any other non-transmission medium, which can be used to store information that can be accessed by a computing device. As defined herein, a computer readable medium does not include a transitory computer readable medium such as a modulated data signal and a carrier wave.
For convenience of description, the above devices are described as being divided into various units by function, respectively. Of course, the functionality of the units may be implemented in one or more software and/or hardware when implementing the present application.
The present invention is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each flow and/or block of the flowchart illustrations and/or block diagrams, and combinations of flows and/or blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
It should also be noted that the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrases "comprising a," "8230," "8230," or "comprising" does not exclude the presence of other like elements in a process, method, article, or apparatus comprising the element.
As will be appreciated by one skilled in the art, embodiments of the present application may be provided as a method, system, or computer program product. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.
The application may be described in the general context of computer-executable instructions, such as program modules, being executed by a computer. Generally, program modules include routines, programs, objects, components, data structures, etc. that perform particular tasks or implement particular abstract data types. The application may also be practiced in distributed computing environments where tasks are performed by remote processing devices that are linked through a communications network. In a distributed computing environment, program modules may be located in both local and remote computer storage media including memory storage devices.
The embodiments in the present specification are described in a progressive manner, and the same and similar parts among the embodiments are referred to each other, and each embodiment focuses on the differences from the other embodiments. In particular, for the system embodiment, since it is substantially similar to the method embodiment, the description is simple, and for the relevant points, reference may be made to the partial description of the method embodiment.
The above description is only an example of the present application and is not intended to limit the present application. Various modifications and changes may occur to those skilled in the art to which the present application pertains. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the scope of the claims of the present application.
Claims (10)
1. A method for constructing a modular multilevel converter is characterized by comprising the following steps:
constructing a flexible direct current transmission/distribution system equivalent circuit based on the converter;
establishing a structure diagram of a P-U-I controller transfer function of the current converter according to the equivalent circuit and the feedback logic of the P-U-I controller;
and determining transfer functions and control parameters of each link of the P-U-I controller in the structure diagram so as to configure the P-U-I controller.
2. The method according to claim 1, wherein the constructing of the converter-based flexible dc power transmission/distribution system equivalent circuit specifically comprises:
and simplifying the flexible direct current transmission/distribution system into a circuit topology in which the MMC converter station is respectively connected with the direct current side virtual equivalent resistor, the rest converter stations on the direct current circuit and the equivalent direct current capacitor of the interface converter to obtain the equivalent circuit.
3. The method according to claim 1, wherein the step of establishing a block diagram of a P-U-I controller transfer function of the converter according to the equivalent circuit and the feedback logic of the P-U-I controller specifically comprises:
respectively constructing an active branch adopting a P-U-I controller, a reactive branch adopting the P-U-I controller and a coupling relation between the active branch and the reactive branch according to the equivalent circuit;
and establishing a structure diagram of the transfer function of the P-U-I controller of the converter according to the feedback logic of the power, voltage and current loops of the P-U-I controller.
4. The method according to claim 2, wherein the determining the transfer function and the control parameter of each link of the P-U-I controller in the structure diagram specifically comprises:
determining a transfer function of each link of the P-U-I controller;
determining transfer function parameters of each link of the P-U-I controller;
and obtaining control parameters of each link of the P-U-I controller according to the primary electrical parameters and the control parameters of the flexible direct current transmission/distribution system.
5. The method according to claim 4, wherein the determining the transfer function of each link of the P-U-I controller specifically comprises:
determining a transfer function structure diagram of the MMC current converter;
determining a voltage loop feedback link transfer function;
and determining a transfer function of a power loop feedback link.
6. The method according to claim 4, wherein the determining the transfer function parameters of each link of the P-U-I controller specifically comprises:
determining a transfer function of a PI controller of each link of the P-U-I controller;
determining an open-loop transfer function and a closed-loop transfer function of a power loop in the flexible direct current transmission/distribution system;
and obtaining parameters of the P-U-I controller according to the preset power loop parameters and the open-loop transfer function and the closed-loop transfer function of the power loop to obtain transfer function parameters.
7. The method for constructing a modular multilevel converter according to claim 6, wherein the determining the open-loop transfer function and the closed-loop transfer function of the power loop in the flexible DC power transmission/distribution system specifically comprises:
determining an open-loop transfer function and a closed-loop transfer function of a current loop in the flexible direct current transmission/distribution system, and further obtaining the open-loop transfer function and the closed-loop transfer function of the voltage loop;
and obtaining an open-loop transfer function and a closed-loop transfer function of the power ring according to the parameter setting value of the PI controller of the voltage ring and the open-loop transfer function and the closed-loop transfer function of the voltage ring.
8. A modular multilevel converter building apparatus comprising:
the equivalent circuit construction module is used for constructing a flexible direct current transmission/distribution system equivalent circuit based on the converter;
the controller structure chart building module is used for building a structure chart of a P-U-I controller transfer function of the current converter according to the equivalent circuit and the feedback logic of the P-U-I controller;
and the parameter solving module is used for determining a transfer function and a control parameter of each link of the P-U-I controller in the structure diagram so as to configure the P-U-I controller.
9. A computer device comprising a memory, a processor, and a computer program stored on the memory and executable on the processor,
the processor, when executing the program, implements the method of any of claims 1-7.
10. A computer-readable medium, having stored thereon a computer program,
the program when executed by a processor implements the method of any one of claims 1 to 7.
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| CN202211054452.9A CN115586717A (en) | 2022-08-31 | 2022-08-31 | Method and device for constructing modular multilevel converter |
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