CN117791718A - Synchronous stability evaluation method and system for power system of multiple virtual synchronous generators - Google Patents
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Abstract
The invention discloses a synchronous stability evaluation method and a synchronous stability evaluation system for a power system of multiple virtual synchronous generators, which are used for establishing a dynamic model of an embedded system of the multiple virtual synchronous generators with controller amplitude limiting; constructing a system transient energy function based on the dynamic model; comprehensively considering the influence of frequency amplitude limiting and current saturation to obtain a transient energy boundary of the system; acquiring a synchronous stability evaluation criterion of a plurality of virtual synchronous generator embedded power systems based on the obtained system transient energy boundary; based on the synchronous stability evaluation criterion, the synchronous stability evaluation result of the system is rapidly given. According to the invention, the synchronous stability of the system is evaluated through the synchronous stability criterion, electromagnetic transient simulation is not needed, the calculation time consumption is short, the dynamic synchronous stability evaluation of the novel power system is facilitated, and the safe and stable operation capability of the system can be effectively improved.
Description
Technical Field
The invention belongs to the technical field of power, and particularly relates to a synchronization stability evaluation method and system of a multi-virtual synchronous generator power system.
Background
Starting from the next half of 2003, several large-scale power failure accidents continuously occur worldwide, and a great deal of attention is paid to the analysis of the stability of the power system. To realize the detailed and deep formation of the blackout accident, firstly, various statistical characteristics of the power network need to be inspected, and further dynamics analysis is carried out on the blackout accident on the basis. Current research on the problem of grid phase synchronization stability is mainly divided into two categories: the method is characterized in that the method is used for examining the local construction of the power grid and the phase synchronization stability problem of the local power grid, and the method is used for carrying out phase synchronization stability analysis on the integral expression characteristics of the whole power grid in a statistical sense. It can be said that the current main stream of research on grid phase synchronization stabilization is reductive rather than systematic. Modern power systems are evolving towards high voltage, large units, large grid interconnections, operational marketization, etc., and offer challenges to online real-time and even super real-time numerical simulation analysis. The rapid development of micro-processing technology and computer networks has enabled the economical application of high-performance computing in the field of numerical simulation of electrical power systems. In a new calculation mode, how to fully develop the calculation capability of various existing software and hardware calculation resources on the network to perform grid phase synchronization parallelization evaluation is a challenging application research subject.
In recent years, with the mass access of new energy, the duty ratio of the power electronic converter type power supply is continuously improved, and the problem of synchronous stability is also increasingly outstanding. Grid-type converters are becoming more popular than grid-type converters because they can spontaneously provide inertial or frequency support when required by the power system. But a grid-type converter may lose synchronization with the power system when it encounters a serious ac fault.
However, current research focuses on synchronous stability and control of a single inverter with an infinite system, lacking a synchronous stability assessment method for multiple inverter embedded systems with controller clipping.
Therefore, how to quickly evaluate the synchronization stability of a power system accessed by a large amount of new energy is still a critical problem to be solved.
Disclosure of Invention
The technical problem to be solved by the invention is to provide a synchronous stability evaluation method and a synchronous stability evaluation system for a multi-virtual synchronous generator power system aiming at the defects in the prior art, which are used for solving the technical problem that the synchronous stability of a power system accessed by a large amount of new energy cannot be evaluated rapidly at present.
The invention adopts the following technical scheme:
the method for evaluating the synchronous stability of the power system of the multiple virtual synchronous generators comprises the following steps:
S1, establishing a dynamic model of a plurality of virtual synchronous generator embedded systems with controller amplitude limiting;
s2, establishing transient energy functions of the multiple virtual synchronous generator embedded systems according to the dynamic models of the multiple virtual synchronous generator embedded systems obtained in the step S1;
s3, constructing a synchronous stability evaluation criterion of a plurality of virtual synchronous generator embedded systems under the condition of considering frequency limit and current saturation according to the transient energy function obtained in the step S2;
s4, determining a synchronous stability evaluation result of the system according to the synchronous stability evaluation criterion obtained in the step S3;
s5, determining a frequency limit setting scheme of each converter according to the synchronous stability evaluation criterion obtained in the step S3.
Preferably, in step S1, the dynamic model of the multiple virtual synchronous generator embedded system with controller clipping is as follows:
ω i ＝ω ci -ω s
(ω imin ＜ω i ＜ω imax )
ω i ＝ω imax ,(ω i ＞ω imax ,/>)
ω i ＝ω imin ,(ω i ＜ω imin ,/>)
wherein θ i 、ω ci The angle and angular velocity, ω, respectively provided for the ith VSG s Referencing an angular velocity to the system; omega i Is the difference between the angular velocity of the ith converter and the system reference angular velocity, T Ji And D i Inertia and damping of the ith converter, P i 0 And P i Respectively the power reference value and the actual power output omega of the ith converter imax And omega imin The upper limit and the lower limit of the angular velocity of the i-th converter are respectively indicated, and the subscript i indicates the i-th converter.
More preferably, the output power P of the ith converter in the constant voltage control mode i The following are provided:
wherein U is i 、U j Voltage at the point of common coupling of the ith and j-th converters; b (B) ij To simplify susceptance of the line ij in the network;
output current of the ith converter in current limiting control modeThe following are provided:
wherein,is a vector expression of the current and the voltage of the ith converter in the current limiting control mode, I max And delta i For the preset amplitude and saturation current angle of the saturation current, Y ij K is an index set of the converter in a current limiting mode;
voltage U of each converter in current limiting control mode k The following are provided:
wherein U is k(k×1) Is the voltage vector of the converter, Y k An admittance matrix of a simplified network for converters in current limited mode,is the current vector of the inverter, ">For a current vector flowing from a current-limited mode converter to an non-current-limited mode converter, k is the number of converters in current-limited mode, and subscript (kxk) indicates that the corresponding vector has k rows and k columns;
is at a limit ofActive power P output by ith converter in current mode i The expression is as follows:
wherein,is the voltage vector expression of the ith converter in the current limiting control mode.
Preferably, in step S2, the transient energy functions of the plurality of virtual synchronous generator embedded systems are as follows:
wherein θ si I epsilon n is the steady-state balance point of the ith converter, T Ji For the inertia of the i-th inverter,for the angular velocity of the ith converter, P i 0 Is the active power reference value theta of the ith converter i Angle of the ith converter, theta si Is the stable balance point of the ith converter, U i For the voltage of the ith converter, U j For the voltage of the jth converter, B ij To simplify susceptance of line ij in network, θ j Is the angle of the j-th converter.
Preferably, in step S3, whenWhen meeting, the synchronous stability of the system is ensured, V s For switching system energy at the stationary point; />Maximum potential energy V of system as transient energy boundary of system cr By using the closest approachStabilization of the equilibrium point method>Maximum potential energy V for ensuring system not to enter CLC mode during fault clearing cs Is determined by the minimum value of (a).
More preferably, the system energy V at the stationary point is switched s The following relationship is satisfied:
wherein V is cr Stabilizing energy boundaries for synchronization of the system under study; v (V) cs To ensure maximum potential energy for the system not to enter CLC mode when the fault clears.
Preferably, the synchronous-stationary energy boundary V of the system under investigation cr The method comprises the following steps:
V cs (x)＝minf(θ 1 ,...,θ i ,...θ n )
wherein V is cs (x) To ensure maximum potential energy of the system not entering CLC mode when fault clearing, f (θ 1 ,...,θ i ,...θ n ) To optimize the objective function of the problem, i ci Current of converter in current limiting mode, I max For the current limit value, i ck Is the current of the converter in constant voltage mode, Y kj To simplify admittances of kth and jth nodes of the network, U j For the voltage of the jth converter, theta j Is the angle of the j-th converter.
Preferably, in step S4, the system energy after the failure satisfiesWhen the system is in synchronous stability, V s Transient energy of the system after fault clearing.
Preferably, in step S5, the frequency upper limit setting of each converter adopts a setting rule that:
wherein omega imax For the set frequency limit, V cr For synchronizing and stabilizing energy boundaries of the system under investigation, T Ji The inertia of the ith converter is given, and n is the number of converters of the system under study.
In a second aspect, an embodiment of the present invention provides a synchronization stability evaluation system of a multi-virtual synchronous generator power system, including:
the construction module is used for establishing a dynamic model of the embedded system of the plurality of virtual synchronous generators with controller amplitude limiting;
The function module is used for establishing transient energy functions of the plurality of virtual synchronous generator embedded systems according to the dynamic models of the plurality of virtual synchronous generator embedded systems obtained by the construction module;
the criterion module is used for constructing a synchronous stability evaluation criterion of the multiple virtual synchronous generator embedded systems under the condition of considering frequency limit and current saturation according to the transient energy function obtained by the function module;
the evaluation module is used for determining a synchronous stability evaluation result of the system according to the synchronous stability evaluation criterion obtained by the criterion module;
and the scheme module is used for determining the frequency limit setting scheme of each converter according to the synchronous stability evaluation criterion obtained by the criterion module.
In a third aspect, a chip includes a memory, a processor, and a computer program stored in the memory and executable on the processor, where the processor implements the steps of the method for evaluating synchronous stability of a multi-virtual synchronous generator power system described above when the computer program is executed.
In a fourth aspect, an embodiment of the present invention provides an electronic device, including a computer program, where the computer program when executed by the electronic device implements the steps of the method for evaluating synchronization stability of a multi-virtual synchronous generator power system described above.
Compared with the prior art, the invention has at least the following beneficial effects:
the method for evaluating the synchronous stability of the power system of the multiple virtual synchronous generators comprises the steps of firstly modeling a plurality of converter embedded systems considering the amplitude limitation of a controller, further constructing a transient energy function of the system, deducing by combining the amplitude limitation characteristic of the controller, revealing that the system leaves the amplitude limitation boundary of the controller at a plurality of fixed switching points, further discovering two special switching points which have the minimum transient energy and are irrelevant to time and switching times, and defining the special switching points as switching fixed points. And a synchronous stability criterion is provided, namely, when the energy of the two switching fixed points is smaller than the critical energy of the system, the global stability of the system can be ensured. According to the method, the synchronous stability of the system is evaluated through the synchronous stability criterion, electromagnetic transient simulation is not needed, the calculation time consumption is short, and the dynamic synchronous stability evaluation of the novel power system is facilitated.
Furthermore, a dynamic model of the embedded system of the multiple virtual synchronous generators with controller amplitude limiting is established, and the method is favorable for the follow-up synchronization stability evaluation criterion and the proposal of a frequency setting scheme.
Further, a transient energy function is constructed for a plurality of virtual synchronous generator embedded systems, and the system stability condition is determined through direct judgment of the system energy.
Further, comprehensively considering the influences of frequency limiting and current saturation, a synchronous stability criterion is provided, namely global stability of the system can be ensured when the energy of two switching fixed points is smaller than the critical energy of the system.
Furthermore, according to the proposed synchronization stability criterion, a frequency limit setting scheme is obtained to realize system power angle stability.
Further, a system synchronization stability criterion is obtained, namely, the system energy after the fault meets the following conditionAt the time of tyingThe system synchronization stability is ensured.
Furthermore, the frequency limit setting scheme of each converter can be determined according to the synchronous stability evaluation criterion, and the limit of the same controller limit is not required to be possessed by all converters, so that the global stability of the system can be ensured as long as the stability condition of the synchronous stability criterion is met.
It will be appreciated that the advantages of the second aspect may be found in the relevant description of the first aspect, and will not be described in detail herein.
In conclusion, the method does not need electromagnetic transient simulation, is short in calculation time consumption, is favorable for dynamic synchronous stability assessment of the novel power system, and can effectively improve the safe and stable operation capability of the system.
The technical scheme of the invention is further described in detail through the drawings and the embodiments.
Drawings
FIG. 1 is a flow chart of the present invention;
FIG. 2 is a schematic topology of a test system;
FIG. 3 is a graph of the dynamic response of the inverter under critical energy constraints for the test system;
FIG. 4 is a graph of dynamic response of the test system with different frequency limits set for each VSG;
FIG. 5 is a schematic diagram of a computer device according to an embodiment of the present invention;
fig. 6 is a block diagram of a chip according to an embodiment of the present invention.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and fully with reference to the accompanying drawings, in which it is evident that the embodiments described are some, but not all embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
In the description of the present invention, it will be understood that the terms "comprises" and "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.
It is also to be understood that the terminology used in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used in this specification and the appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.
It should be further understood that the term "and/or" as used in the present specification and the appended claims refers to any and all possible combinations of one or more of the associated listed items, and includes such combinations, e.g., a and/or B, may represent: a exists alone, A and B exist together, and B exists alone. In the present invention, the character "/" generally indicates that the front and rear related objects are an or relationship.
It should be understood that although the terms first, second, third, etc. may be used to describe the 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 one preset range from another. For example, a first preset range may also be referred to as a second preset range, and similarly, a second preset range may also be referred to as a first preset range without departing from the scope of embodiments of the present invention.
Depending on the context, the word "if" as used herein may be interpreted as "at … …" or "at … …" or "in response to a determination" or "in response to detection". Similarly, the phrase "if determined" or "if detected (stated condition or event)" may be interpreted as "when determined" or "in response to determination" or "when detected (stated condition or event)" or "in response to detection (stated condition or event), depending on the context.
Various structural schematic diagrams according to the disclosed embodiments of the present invention are shown in the accompanying drawings. The figures are not drawn to scale, wherein certain details are exaggerated for clarity of presentation and may have been omitted. The shapes of the various regions, layers and their relative sizes, positional relationships shown in the drawings are merely exemplary, may in practice deviate due to manufacturing tolerances or technical limitations, and one skilled in the art may additionally design regions/layers having different shapes, sizes, relative positions as actually required.
The invention provides a synchronous stability evaluation method of a multi-virtual synchronous generator power system, which is characterized in that an energy boundary of an autonomous system without controller limitation is determined by a nearest unstable balance point method, the maximum potential energy which enables the system not to enter a constant voltage control mode is obtained, further, a synchronous stability evaluation criterion under the condition of considering frequency limit and current saturation is provided, and a synchronous stability evaluation result of the system is rapidly given according to the synchronous stability evaluation criterion.
Referring to fig. 1, the method for evaluating the synchronization stability of a power system with multiple virtual synchronous generators according to the present invention includes the following steps:
s1, a dynamic model of an embedded system of a plurality of virtual synchronous generators with controller amplitude limiting;
for an electric power system consisting of n virtual synchronous machines (virtual synchronous generator, VSG), the kinetic equation of the ith inverter can be described by the following equation, taking into account the effects of controller clipping:
wherein θ i 、ω ci The angle and angular velocity provided for the i-th VSG, respectively; omega s Referencing an angular velocity to the system; omega i Is the difference between the angular velocity of the ith converter and the system reference angular velocity; t (T) Ji And D i Inertia and damping of the ith converter respectively; p (P) i 0 And P i Respectively the power reference value and the actual power output of the ith converter; omega imax And omega imin The upper limit and the lower limit of the angular velocity of the i-th converter are respectively indicated, and the subscript i indicates the i-th converter.
Further, the output power P of the ith converter in constant voltage control mode i The expression is as follows:
wherein U is i 、U j Voltage at a point of common coupling (the point of common coupling, PCC) of the i, j-th inverter; b (B) ij To simplify susceptance of the line ij in the network.
The output current expression of the i-th inverter in the current limiting control mode is as follows:
wherein,is a vector expression of the current and the voltage of the ith converter in the current limiting control mode; i max And delta i The amplitude and the saturation current angle of the saturation current are preset; y is Y ij ＝jB ij Representing the admittance of the reduced network, K is the index set of the converter in current limiting mode.
Voltage U of each converter in current limiting control mode based on (6) k The expression of (2) can be expressed as follows:
wherein,is the voltage vector of the converter; y is Y k An admittance matrix of a simplified network for converters in current limited mode; />Is the current vector of the converter; />A current vector flowing from the current-limited mode converter to the non-current-limited mode converter; k is the number of converters in the current limit mode, and the subscript (kxk) indicates that the corresponding vector has k rows and k columns.
Active power P output by ith converter in current limiting mode i The expression is as follows:
s2, establishing transient energy functions of a plurality of virtual synchronous generator embedded systems;
the construction system energy function is as follows:
wherein θ si ，i∈n is the steady state balance point of the ith inverter.
Deriving the time of equation (10) to obtain the constructed transient energy function semi-negative determination, and the system track x (t) is bounded:
In order to obtain the system stability criterion, the theory of the latest unstable equilibrium point (unstable equilibrium point, UEP) is adopted in the later analysis, namely, the energy corresponding to the UEP point with the smallest transient energy is searched as the transient energy stability boundary.
S3, analyzing the dynamic characteristics of the multi-converter system considering frequency limiting and current limiting according to the energy function constructed in the step S2, and constructing a synchronous stability evaluation criterion of the multiple virtual synchronous generator embedded systems under the condition of considering frequency limit and current saturation;
the VSG, which considers frequency clipping, has two switching inactivity points independent of the failure duration. When the frequency limit of each converter is specified, the root of the following function is the point where the trajectory leaves the boundary, called the switch-stationary point of the dynamic system under study.
Wherein,the angle of the switching fixed point of the nth converter at the position away from the upper limit of the frequency limiting; />The angle of the switching fixed point of the nth converter at the position away from the lower limit of the frequency limiting; omega imax For the ith converterAn upper frequency limit; omega imin Is the lower frequency limit of the ith converter; definitions->ω max ＝[ω 1max ,ω 2max ,...,ω nmax ] T And omega min ＝[ω 1min ,ω 2min ,...,ω nmin ] T The method comprises the steps of carrying out a first treatment on the surface of the At this time, the switching immobility point of the system under investigation can be noted as (θ u ,ω max ) Sum (theta) l ,ω min )。
It is demonstrated that the system transient energy is minimal when the angle of the switching stationary point is set at the respective stable equilibrium point (stable equilibrium point, SEP):
Wherein θ s Column vectors are formed for stable balance points of all converters of the system.
Thus, will (θ s ,ω max ) As an initial point (starting point) of the disturbed system trajectory, the system has the remarkable characteristic of minimum transient energy, thereby greatly improving the stability of the system.
Further, when the system track touches the frequency limit, the transient energy function is monotonically decreased, and the kth converter track is set to be inTouching frequency boundaries at the moment, at +.>The time-of-day departure from the frequency boundary, the derivative of the system transient energy with respect to time can be expressed as follows:
wherein θ k Is the angle of the kth converter; omega k Is the angular velocity of the kth inverter.
Equation (15) is divided into two parts, and the following inequality is assumed to hold:
so when the system trajectory touches the frequency limit, the transient energy function monotonically decreases.
Therefore, if the current saturation influence of each converter is not considered, the system synchronization stability is ensured when the following inequality is satisfied:
wherein V is s For switching system energy at the stationary point;is the transient energy boundary of the system and is determined by the method of the latest unstable equilibrium point.
At the same time, in order to prevent the system from entering the current limiting (current limiting control, CLC) mode after severe ac faults, the maximum potential of the system under investigation (denoted as V cr ) Determined by the minimum of the two values. One is obtained by the method closest to the unstable equilibrium pointThe other is the maximum potential energy (denoted as V) that ensures that the system does not enter CLC mode when the fault clears cs ). Expressed in the following form:
wherein V is cr Stabilizing energy boundaries for synchronization of the system under study; v (V) cs To ensure maximum potential energy for the system not to enter CLC mode when the fault clears.
V cr The method is obtained by solving the following optimization problems:
wherein,
the physical meaning of the optimization problem described above is to obtain the maximum system potential energy (synchronization stability margin) to ensure that any VSG in the system does not enter CLC state, the optimization problem of equation (20) consists of n sub-problems, which can be written as:
s4, according to the synchronous stability evaluation criterion in the step S3, a synchronous stability evaluation result of the system is rapidly given;
specifically, when the system energy after the fault satisfies the following relation, the system synchronization stability is ensured:
wherein V is s Transient energy of the system after fault clearing.
S5, according to the synchronous stability evaluation criterion in the step S3, giving out a frequency limit setting scheme of each converter;
in particular, the synchronization stability assessment criteria of step S3 provides a useful guide for setting frequency limits to ensure global stability of the system. The upper frequency limit setting for each converter may employ a simple setting rule that may be derived based on (19) as:
Wherein omega imax For the set frequency limit.
It is noted that the proposed synchronization stability criterion does not require that all converters have the same limit of controller clipping, in fact, the global stability of the system can be guaranteed as long as the stability condition of equation (19) is met.
In still another embodiment of the present invention, a synchronization stability evaluation system of a multi-virtual synchronous generator power system is provided, where the system can be used to implement the synchronization stability evaluation method of the multi-virtual synchronous generator power system, and specifically, the synchronization stability evaluation system of the multi-virtual synchronous generator power system includes a construction module, a function module, a criterion module, an evaluation module, and a scheme module.
The system comprises a construction module, a control module and a control module, wherein the construction module is used for establishing a dynamic model of a plurality of virtual synchronous generator embedded systems with controller amplitude limiting;
the function module is used for establishing transient energy functions of the plurality of virtual synchronous generator embedded systems according to the dynamic models of the plurality of virtual synchronous generator embedded systems obtained by the construction module;
the criterion module is used for constructing a synchronous stability evaluation criterion of the multiple virtual synchronous generator embedded systems under the condition of considering frequency limit and current saturation according to the transient energy function obtained by the function module;
The evaluation module is used for determining a synchronous stability evaluation result of the system according to the synchronous stability evaluation criterion obtained by the criterion module;
and the scheme module is used for determining the frequency limit setting scheme of each converter according to the synchronous stability evaluation criterion obtained by the criterion module.
In yet another embodiment of the present invention, a terminal device is provided, the terminal device including a processor and a memory, the memory for storing a computer program, the computer program including program instructions, the processor for executing the program instructions stored by the computer storage medium. The processor may be a central processing unit (Central Processing Unit, CPU), but may also be other general purpose processor, digital signal processor (Digital Signal Processor, DSP), application specific integrated circuit (Application Specific Integrated Circuit, ASIC), off-the-shelf programmable gate array (Field-Programmable Gate Array, FPGA) or other programmable logic device, discrete gate or transistor logic device, discrete hardware components, etc., which are the computational core and control core of the terminal adapted to implement one or more instructions, in particular to load and execute one or more instructions to implement the corresponding method flow or corresponding functions; the processor of the embodiment of the invention can be used for the operation of a synchronous stability evaluation method of a multi-virtual synchronous generator power system, and comprises the following steps:
Establishing a dynamic model of a plurality of virtual synchronous generator embedded systems with controller amplitude limiting; establishing transient energy functions of the multiple virtual synchronous generator embedded systems according to the obtained dynamic models of the multiple virtual synchronous generator embedded systems; constructing a synchronous stability evaluation criterion of a plurality of virtual synchronous generator embedded systems under the condition of considering frequency limit and current saturation according to the obtained transient energy function; determining a synchronous stability evaluation result of the system according to the obtained synchronous stability evaluation criterion; and determining a frequency limit setting scheme of each converter according to the obtained synchronous stability evaluation criterion.
Referring to fig. 5, 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, the computer program 63 when executed by the processor 61 implements the reservoir inversion wellbore fluid composition calculation method of the embodiment, and is not described in detail herein to avoid repetition. Alternatively, the computer program 63, when executed by the processor 61, implements the functions of each model/unit in the synchronous stability evaluation system of the multi-virtual synchronous generator power system of the embodiment, and is not described herein in detail for avoiding repetition.
The computer device 60 may be a desktop computer, a notebook computer, a palm top computer, a cloud server, or the like. Computer device 60 may include, but is not limited to, a processor 61, a memory 62. It will be appreciated by those skilled in the art that fig. 5 is merely an example of a computer device 60 and is not intended to limit the computer device 60, and may include more or fewer components than shown, or may combine certain components, or different components, e.g., a computer device may also include an input-output device, a network access device, a bus, etc.
The processor 61 may be a central processing unit (Central Processing Unit, CPU), but may also be other general purpose processors, digital signal processors (Digital Signal Processor, DSP), application specific integrated circuits (Application Specific Integrated Circuit, ASIC), field programmable gate arrays (Field-Programmable Gate Array, FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, or the like. A general purpose processor may be a microprocessor or the processor may be any conventional processor or the like.
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 provided on the computer device 60, a Smart Media Card (SMC), a Secure Digital (SD) Card, a Flash memory Card (Flash Card), or the like.
Further, the memory 62 may also include both internal storage units and external storage devices of the computer device 60. 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.
Referring to fig. 6, the terminal device is a chip, and the chip 600 of this embodiment includes a processor 622, which may be one or more in number, and a memory 632 for storing a computer program executable by the processor 622. The computer program stored in memory 632 may include one or more modules each corresponding to a set of instructions. Further, the processor 622 may be configured to execute the computer program to perform the synchronization stability assessment method of the multi-virtual synchronous generator power system described above.
In addition, chip 600 may further include a power supply component 626 and a communication component 650, where power supply component 626 may be configured to perform power management of chip 600, and communication component 650 may be configured to enable communication of chip 600, e.g., wired or wireless communication. In addition, the chip 600 may also include an input/output interface 658. Chip 600 may operate based on an operating system stored in memory 632.
In a further embodiment of the present invention, the present invention further provides a storage medium, in particular, a computer readable storage medium, which is a memory device in the terminal device, for storing programs and data. It will be appreciated that the computer readable storage medium herein may include both a built-in storage medium in the terminal device and an extended storage medium supported by the terminal device. The computer-readable storage medium provides a storage space storing an operating system of the terminal. Also stored in the memory space are one or more instructions, which may be one or more computer programs, adapted to be loaded and executed by the processor. The computer readable storage medium may be a high-speed RAM Memory or a Non-Volatile Memory (Non-Volatile Memory), such as at least one magnetic disk Memory.
One or more instructions stored in a computer-readable storage medium may be loaded and executed by a processor to implement the respective steps of the method for evaluating synchronous stability of a multi-virtual synchronous generator power system of the above embodiments; one or more instructions in a computer-readable storage medium are loaded by a processor and perform the steps of:
Establishing a dynamic model of a plurality of virtual synchronous generator embedded systems with controller amplitude limiting; establishing transient energy functions of the multiple virtual synchronous generator embedded systems according to the obtained dynamic models of the multiple virtual synchronous generator embedded systems; constructing a synchronous stability evaluation criterion of a plurality of virtual synchronous generator embedded systems under the condition of considering frequency limit and current saturation according to the obtained transient energy function; determining a synchronous stability evaluation result of the system according to the obtained synchronous stability evaluation criterion; and determining a frequency limit setting scheme of each converter according to the obtained synchronous stability evaluation criterion.
For the purpose of making the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is apparent that the described embodiments are some embodiments of the present invention, but not all embodiments of the present invention. The components of the embodiments of the present invention generally described and illustrated in the figures herein may be arranged and designed in a wide variety of different configurations. Thus, the following detailed description of the embodiments of the invention, as presented in the figures, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
Referring to fig. 2, fig. 2 is a schematic diagram of a 9-node system under test.
Referring to fig. 3, fig. 3 is a dynamic response of the system after the three-phase ground ac fault occurs on the bus No. 9 of the test system. FIG. 3 (a) is a phase plane diagram of machine number 1 when the frequency limit is set such that the system trajectory does not enter CLC mode; FIG. 3 (b) is a phase diagram of machine number 1 when the frequency limit setting is not taking into account the controller limit; fig. 3 (c) shows transient energy of the system for different fault durations and different control strategies. When the value of the frequency clipping ensures that the system does not enter CLC mode, the system trajectory does not enter CLC mode after leaving the switch dead point, regardless of the duration of the fault, as shown by the black and blue curves. If the system has the capability to enter the CLC mode, the risk of instability is faced during the continuous switching process, as shown in the red curve. This result verifies the effectiveness of the invention.
Referring to table 1, table 1 shows the inverter parameters used.
TABLE 1
To better simulate the integration of renewable energy stations into large power systems through a power transmission network, machine number three is modified to an infinite bus system, the inertia constant is set to a larger number (T J3 =600). The first machine and the second machine represent renewable energy stations connected with the converter. During normal operation, the grid-tied VSG is regulated as a constant voltage source (U i ∠θ i )，θ i Is the lead angle between the d-axis and the x-axis. Inertia constants of two VSGs (T J1 And T J2 ) Set to 6s and 4s, respectively. The small damping of each VSG was set to 1.5p.u. The current saturation of each VSG was set to 1.4p.u. The system rated capacity was 500MW and the capacity of each VSG was 1000MW. Since renewable energy power generation centers have little load, local loads are modified to relatively low levels.
Referring to table 2, table 2 shows the steady state power flow results of the system.
TABLE 2
Referring to table 3, table 3 sets the results for the system energy boundaries and frequency limits without considering the controller limits.
TABLE 3 Table 3
As shown in table 3, the system energy boundaries and frequency limitation ranges are large regardless of the controller limitations. When the frequency limit is reached, the system trajectory is reconstructed to start moving from the special switching stationary point. However, the system is unstable. This may be interpreted as that the placement of such a switch immobilization point, as determined by the energy boundaries of autonomous systems without controller limitations, does not ensure that no mode switch will occur after a large disturbance. Once the mode switch is frequently triggered, system stability cannot be guaranteed.
Referring to table 4, table 4 shows the system energy boundary and frequency limit setting results considering current limit control.
TABLE 4 Table 4
As shown in table 4, the system energy boundary and frequency limit range for the current limit control are considered to be small. At this point, the system trace does not enter CLC mode, regardless of the duration of the fault. The placement of such a switch immobilization point ensures global stability of the system.
Referring to fig. 4, fig. 4 shows the system dynamic response when the frequency limit of each VSG is not uniform. Fig. 4 (a) is a phase diagram of a machine number one, the frequency limit of which is set to 0.01; FIG. 4 (b) is a phase diagram of machine number two with a frequency limit set to 0.015; fig. 4 (c) is the system transient energy of two machines. In fact, as long as the total energy of the switching immobilization point of the design is less than the critical energy, the global stability of the system can be guaranteed. When a fault clears, the system trace moves from the designed switch dead point and this attribute is independent of the length of time the fault cleared. Fig. 4 (c) shows that the stability of the system is guaranteed after a limited number of handovers based on frequency limitation.
In summary, according to the method and the system for evaluating the synchronous stability of the power system of the multiple virtual synchronous generators, the energy boundary of the autonomous system without the limitation of the controller is determined by the method of the nearest unstable balance point, the maximum potential energy for enabling the system not to enter the constant voltage control mode is obtained, and further the criterion for evaluating the synchronous stability under the condition of considering the frequency limit and the current saturation is provided. And according to the synchronous stability evaluation criterion, a synchronous stability evaluation result and a frequency limit setting scheme of the system are rapidly given.
It will be apparent to those skilled in the art that, for convenience and brevity of description, only the above-described division of the functional units and modules is illustrated, and in practical application, the above-described functional distribution may be performed by different functional units and modules according to needs, i.e. the internal structure of the apparatus is divided into different functional units or modules to perform all or part of the above-described functions. The functional units and modules in the embodiment may be integrated in one processing unit, or each unit may exist alone physically, or two or more units may be integrated in one unit, where the integrated units may be implemented in a form of hardware or a form of a software functional unit. In addition, specific names of the functional units and modules are only for convenience of distinguishing from each other, and are not used for limiting the protection scope of the present application. The specific working process of the units and modules in the above system may refer to the corresponding process in the foregoing method embodiment, which is not described herein again.
In the foregoing embodiments, the descriptions of the embodiments are emphasized, and in part, not described or illustrated in any particular embodiment, reference is made to the related descriptions of other embodiments.
Those of ordinary skill in the art will appreciate that the various illustrative elements and algorithm steps described in connection with the embodiments disclosed herein may be implemented as electronic hardware, or combinations of computer software and electronic hardware. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the solution. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present invention.
In the embodiments provided in the present invention, it should be understood that the disclosed apparatus/terminal and method may be implemented in other manners. For example, the apparatus/terminal embodiments described above are merely illustrative, e.g., the division of the modules or units is merely a logical function division, and there may be additional divisions when actually implemented, e.g., multiple units or components may be combined or integrated into another system, or some features may be omitted or not performed. Alternatively, the coupling or direct coupling or communication connection shown or discussed may be an indirect coupling or communication connection via interfaces, devices or units, which may be in electrical, mechanical or other forms.
The units described as separate units may or may not be physically separate, and units shown as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of 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.
In addition, each functional unit in the embodiments of the present invention may be integrated in one processing unit, or each unit may exist alone physically, or two or more units may be integrated in one unit. The integrated units may be implemented in hardware or in software functional units.
The integrated modules/units, if implemented in the form of software functional units and sold or used as stand-alone products, may be stored in a computer readable storage medium. Based on such understanding, the present invention may implement all or part of the flow of the method of the above embodiment, or may be implemented by a computer program to instruct related hardware, where the computer program may be stored in a computer readable storage medium, and when the computer program is executed by a processor, the computer program may implement the steps of each of the method embodiments described above. Wherein the computer program comprises computer program code which may be in source code form, object code form, executable file or some intermediate form etc. The computer readable medium may include: any entity or device capable of carrying the computer program code, a recording medium, a usb disk, a removable hard disk, a magnetic disk, an optical disk, a computer Memory, a Read-Only Memory (ROM), a Random-Access Memory (RAM), an electrical carrier wave signal, a telecommunications signal, a software distribution medium, etc., it should be noted that the content of the computer readable medium may be appropriately increased or decreased according to the requirements of legislation and patent practice in jurisdictions, such as in some jurisdictions, according to the legislation and patent practice, the computer readable medium does not include electrical carrier wave signals and telecommunications signals.
The present application is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus, and computer program products according to embodiments of the application. 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.
The above is only for illustrating the technical idea of the present invention, and the protection scope of the present invention is not limited by this, and any modification made on the basis of the technical scheme according to the technical idea of the present invention falls within the protection scope of the claims of the present invention.
Claims (10)
1. The method for evaluating the synchronous stability of the power system of the multiple virtual synchronous generators is characterized by comprising the following steps of:
s1, establishing a dynamic model of a plurality of virtual synchronous generator embedded systems with controller amplitude limiting;
s2, establishing transient energy functions of the multiple virtual synchronous generator embedded systems according to the dynamic models of the multiple virtual synchronous generator embedded systems obtained in the step S1;
s3, constructing a synchronous stability evaluation criterion of a plurality of virtual synchronous generator embedded systems under the condition of considering frequency limit and current saturation according to the transient energy function obtained in the step S2;
S4, determining a synchronous stability evaluation result of the system according to the synchronous stability evaluation criterion obtained in the step S3;
s5, determining a frequency limit setting scheme of each converter according to the synchronous stability evaluation criterion obtained in the step S3.
2. The method for evaluating the synchronization stability of a multi-virtual synchronous generator power system according to claim 1, wherein in step S1, a dynamic model of the multi-virtual synchronous generator embedded system with controller clipping is as follows:
wherein θ i 、ω ci The angle and angular velocity, ω, respectively provided for the ith VSG s Referencing an angular velocity to the system; omega i Is the difference between the angular velocity of the ith converter and the system reference angular velocity, T Ji And D i The inertia and damping of the ith inverter,and P i Respectively the power reference value and the actual power output omega of the ith converter imax And omega imin The upper limit and the lower limit of the angular velocity of the i-th converter are respectively indicated, and the subscript i indicates the i-th converter.
3. The method for evaluating the synchronous stability of a multi-virtual synchronous generator power system according to claim 2, wherein the output power P of the i-th inverter in the constant voltage control mode i The following are provided:
wherein U is i 、U j Voltage at the point of common coupling of the ith and j-th converters; b (B) ij To simplify susceptance of the line ij in the network;
output current of the ith converter in current limiting control modeThe following are provided:
wherein,is a vector expression of the current and the voltage of the ith converter in the current limiting control mode, I max And delta i For the preset amplitude and saturation current angle of the saturation current, Y ij K is an index set of the converter in a current limiting mode;
voltage U of each converter in current limiting control mode k The following are provided:
wherein U is k(k×1) Is the voltage vector of the converter, Y k An admittance matrix of a simplified network for converters in current limited mode,is the current vector of the inverter, ">For a current vector flowing from a current-limited mode converter to an non-current-limited mode converter, k is the number of converters in current-limited mode, and subscript (kxk) indicates that the corresponding vector has k rows and k columns;
active power P output by ith converter in current limiting mode i The expression is as follows:
wherein,is the voltage vector expression of the ith converter in the current limiting control mode.
4. The method for evaluating the synchronization stability of a multi-virtual synchronous generator power system according to claim 1, wherein in step S2, the transient energy functions of the plurality of virtual synchronous generator embedded systems are as follows:
Wherein θ si I epsilon n is the steady-state balance point of the ith converter, T Ji For the inertia of the i-th inverter,for the angular velocity of the ith converter, +.>Is the active power reference value theta of the ith converter i Angle of the ith converter, theta si Is the stable balance point of the ith converter, U i For the voltage of the ith converter, U j For the voltage of the jth converter, B ij To simplify susceptance of line ij in network, θ j Is the angle of the j-th converter.
5. The method for evaluating the synchronous stability of a multi-virtual synchronous generator power system according to claim 1, wherein in step S3, whenWhen meetingThe synchronous stability of the system is ensured, V s For switching system energy at the stationary point; />Maximum potential energy V of system as transient energy boundary of system cr By using the method closest to the unstable equilibrium point>Maximum potential energy V for ensuring system not to enter CLC mode during fault clearing cs Is determined by the minimum value of (a).
6. The method for evaluating the synchronous stability of a multi-virtual synchronous generator power system according to claim 5, wherein the system energy V at the stationary point is switched s The following relationship is satisfied:
wherein V is cr Stabilizing energy boundaries for synchronization of the system under study; v (V) cs To ensure maximum potential energy for the system not to enter CLC mode when the fault clears.
7. The method for evaluating the synchronous stability of a multi-virtual synchronous generator power system according to claim 1, characterized in that the synchronous stability energy boundary V of the system under investigation cr The method comprises the following steps:
V cs (x)＝minf(θ 1 ,...,θ i ,...θ n )
wherein V is cs (x) To ensure maximum potential energy of the system not entering CLC mode when fault clearing, f (θ 1 ,...,θ i ,...θ n ) To optimize the problemI is the target function of (i) ci Current of converter in current limiting mode, I max For the current limit value, i ck Is the current of the converter in constant voltage mode, Y kj To simplify admittances of kth and jth nodes of the network, U j For the voltage of the jth converter, theta j Is the angle of the j-th converter.
8. The method for evaluating the synchronous stability of a multi-virtual synchronous generator power system according to claim 1, wherein in step S4, the system energy after the failure satisfies the following conditionWhen the system is in synchronous stability, V s Transient energy of the system after fault clearing.
9. The method for evaluating the synchronous stability of a multi-virtual synchronous generator power system according to claim 1, wherein in step S5, the upper frequency limit setting of each inverter adopts a setting rule of:
wherein omega imax For the set frequency limit, V cr For synchronizing and stabilizing energy boundaries of the system under investigation, T Ji The inertia of the ith converter is given, and n is the number of converters of the system under study.
10. A synchronous stability assessment system for a multi-virtual synchronous generator power system, comprising:
the construction module is used for establishing a dynamic model of the embedded system of the plurality of virtual synchronous generators with controller amplitude limiting;
the function module is used for establishing transient energy functions of the plurality of virtual synchronous generator embedded systems according to the dynamic models of the plurality of virtual synchronous generator embedded systems obtained by the construction module;
the criterion module is used for constructing a synchronous stability evaluation criterion of the multiple virtual synchronous generator embedded systems under the condition of considering frequency limit and current saturation according to the transient energy function obtained by the function module;
the evaluation module is used for determining a synchronous stability evaluation result of the system according to the synchronous stability evaluation criterion obtained by the criterion module;
and the scheme module is used for determining the frequency limit setting scheme of each converter according to the synchronous stability evaluation criterion obtained by the criterion module.
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