CN113725908A - Grid-connected static stability evaluation method based on converter limit transmission power - Google Patents

Grid-connected static stability evaluation method based on converter limit transmission power Download PDF

Info

Publication number
CN113725908A
CN113725908A CN202111021287.2A CN202111021287A CN113725908A CN 113725908 A CN113725908 A CN 113725908A CN 202111021287 A CN202111021287 A CN 202111021287A CN 113725908 A CN113725908 A CN 113725908A
Authority
CN
China
Prior art keywords
grid
converter
power
transmission power
static stability
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
CN202111021287.2A
Other languages
Chinese (zh)
Other versions
CN113725908B (en
Inventor
刘江东
朱健
孔伯骏
王升波
王建华
陈思宇
陈艳
詹昕
尹俊杰
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Yangzhou Power Supply Branch Of State Grid Jiangsu Electric Power Co ltd
Southeast University
State Grid Jiangsu Electric Power Co Ltd
Original Assignee
Yangzhou Power Supply Branch Of State Grid Jiangsu Electric Power Co ltd
Southeast University
State Grid Jiangsu Electric Power Co Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Yangzhou Power Supply Branch Of State Grid Jiangsu Electric Power Co ltd, Southeast University, State Grid Jiangsu Electric Power Co Ltd filed Critical Yangzhou Power Supply Branch Of State Grid Jiangsu Electric Power Co ltd
Priority to CN202111021287.2A priority Critical patent/CN113725908B/en
Publication of CN113725908A publication Critical patent/CN113725908A/en
Application granted granted Critical
Publication of CN113725908B publication Critical patent/CN113725908B/en
Active legal-status Critical Current
Anticipated expiration legal-status Critical

Links

Images

Classifications

    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06Q—INFORMATION AND COMMUNICATION TECHNOLOGY [ICT] SPECIALLY ADAPTED FOR ADMINISTRATIVE, COMMERCIAL, FINANCIAL, MANAGERIAL OR SUPERVISORY PURPOSES; SYSTEMS OR METHODS SPECIALLY ADAPTED FOR ADMINISTRATIVE, COMMERCIAL, FINANCIAL, MANAGERIAL OR SUPERVISORY PURPOSES, NOT OTHERWISE PROVIDED FOR
    • G06Q10/00—Administration; Management
    • G06Q10/06—Resources, workflows, human or project management; Enterprise or organisation planning; Enterprise or organisation modelling
    • G06Q10/063—Operations research, analysis or management
    • G06Q10/0639—Performance analysis of employees; Performance analysis of enterprise or organisation operations
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06Q—INFORMATION AND COMMUNICATION TECHNOLOGY [ICT] SPECIALLY ADAPTED FOR ADMINISTRATIVE, COMMERCIAL, FINANCIAL, MANAGERIAL OR SUPERVISORY PURPOSES; SYSTEMS OR METHODS SPECIALLY ADAPTED FOR ADMINISTRATIVE, COMMERCIAL, FINANCIAL, MANAGERIAL OR SUPERVISORY PURPOSES, NOT OTHERWISE PROVIDED FOR
    • G06Q50/00—Information and communication technology [ICT] specially adapted for implementation of business processes of specific business sectors, e.g. utilities or tourism
    • G06Q50/06—Energy or water supply
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J1/00—Circuit arrangements for dc mains or dc distribution networks
    • H02J1/10—Parallel operation of dc sources
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J1/00—Circuit arrangements for dc mains or dc distribution networks
    • H02J1/10—Parallel operation of dc sources
    • H02J1/102—Parallel operation of dc sources being switching converters
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J2203/00—Indexing scheme relating to details of circuit arrangements for AC mains or AC distribution networks
    • H02J2203/10—Power transmission or distribution systems management focussing at grid-level, e.g. load flow analysis, node profile computation, meshed network optimisation, active network management or spinning reserve management
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J2203/00—Indexing scheme relating to details of circuit arrangements for AC mains or AC distribution networks
    • H02J2203/20—Simulating, e g planning, reliability check, modelling or computer assisted design [CAD]

Landscapes

  • Business, Economics & Management (AREA)
  • Engineering & Computer Science (AREA)
  • Human Resources & Organizations (AREA)
  • Economics (AREA)
  • Power Engineering (AREA)
  • Strategic Management (AREA)
  • Health & Medical Sciences (AREA)
  • General Physics & Mathematics (AREA)
  • Development Economics (AREA)
  • Educational Administration (AREA)
  • Marketing (AREA)
  • Entrepreneurship & Innovation (AREA)
  • Theoretical Computer Science (AREA)
  • Tourism & Hospitality (AREA)
  • Physics & Mathematics (AREA)
  • General Business, Economics & Management (AREA)
  • Operations Research (AREA)
  • Quality & Reliability (AREA)
  • Game Theory and Decision Science (AREA)
  • Public Health (AREA)
  • Water Supply & Treatment (AREA)
  • General Health & Medical Sciences (AREA)
  • Primary Health Care (AREA)
  • Supply And Distribution Of Alternating Current (AREA)

Abstract

A grid-connected static stability evaluation method based on converter limit transmission power comprises the following steps: the short-circuit capacity ratio SCR is used for representing the grid-connected power grid strength of the virtual synchronous converter system; establishing an equivalent circuit of converter power transmission, determining a converter power transmission vector relation, and calculating transmitted active power P; deriving a point P of maximum transmission power by differentiating the transmitted active power Pmax(ii) a Calculating to obtain SCRminAnd determining the required conditions of grid-connected static stability. Under the background of high power electronic penetration, the invention develops research aiming at the grid-connected stability mechanism of the power electronic converter under the condition of a weak power grid and is based on current transformation under the condition of the weak power gridAnd theoretical support is provided for grid-connected static stability evaluation of the limit transmission power of the device. The method can be widely applied to the field of static stability evaluation of the power grid.

Description

Grid-connected static stability evaluation method based on converter limit transmission power
Technical Field
The invention relates to the field of converter grid-connected static stability evaluation, in particular to a grid-connected static stability evaluation method based on converter limit transmission power.
Background
Under the drive of a double-carbon target, the source-load-storage direct-current characteristic is more obvious, and the traditional power distribution network is gradually developing to the advanced forms of high permeability, high access rate of renewable energy sources and alternating-current and direct-current hybrid connection of power electronic equipment. By adopting a networking mode mainly comprising a power electronic converter, the converter and the converter, and the converter and a power grid interact with each other, so that the internal mechanism of the stability of the power distribution network is changed, and a more complex oscillation phenomenon in a broadband range guided by the converter is presented.
In view of the fact that the internal mechanism of the stability of the alternating current-direct current hybrid power distribution network is changed under high power electronic penetration, the existing power frequency phasor method cannot meet the system analysis requirements, the stability problem of the alternating current-direct current hybrid power distribution network mainly based on a converter networking needs to be researched, the stability analysis is carried out on power electronic key networking equipment, a corresponding stability criterion is provided, and a theoretical basis is provided for the analysis, management and construction application of a future power electronic alternating current-direct current power distribution system.
According to the inherent consistency of a traditional synchronous motor and a power electronic converter on a synchronous mechanism, the stability problem of the power electronic converter can be divided into three categories of static stability, small disturbance stability and transient stability by utilizing the power angle stability theory of a traditional power system. Wherein, the static stability can be judged according to whether a stable static working point exists or not; the small disturbance stability refers to the problem that whether a system generates small signal instability near a static working point, and a relatively mature small signal analysis method based on a linearization theory is formed at present; the transient instability problem of the system presents more complex nonlinear dynamic characteristics, and the stability analysis of the system is beyond the research scope of the linear analysis theory.
Whether the converter system has a stable static operating point is a necessary condition for the static stability of the system, and is also a basis for analyzing the small-disturbance stability of the system. Generally speaking, under the condition of strong power grid, the static stability condition can be met as long as the control design and various parameters of the converter system are set reasonably.
However, under the condition of weak power grid, the impedance of the grid-side line is increased, the transmission power of the converter system is limited, the stable working area is greatly reduced, and the problem of static instability is easily caused. The problem of static instability of the system caused by the change of the impedance characteristic of the line is that non-periodic oscillation different from small disturbance instability appears on the characteristic outside the output of the system. Therefore, before studying the stability of the system in small disturbances, it is necessary to analyze the statically stable operating region of the system under weak grid conditions.
The reduction of the installed capacity of the traditional generator set and the access of a large number of power electronic devices influence the large power grid strength change of an alternating current and direct current power distribution system, and although the power electronic devices can provide certain inertia and damping support for a power grid through a virtual synchronous control technology, the trend that the power distribution network becomes weak is not enough changed. Under the background of high power electronic penetration, a converter system interacts with a power grid, and the problems of oscillation such as subsynchronous/supersynchronous, medium-frequency and high-frequency oscillation are easily caused. Under the condition of weak power grid, because the line impedance is not negligible, the interaction between the generator and the power grid is stronger, the instability problem is more obvious, the generated energy and the stable operation thereof are influenced, and the service life of the generator set is reduced to a certain extent.
Meanwhile, the generation mechanism of the stability problems is different from that of the traditional power system, and the stability problems cannot be explained by using a traditional power system stability analysis method; if the traditional method is used for analysis, the accuracy is not enough.
Therefore, research needs to be carried out on the grid-connected stability mechanism of the power electronic converter under the weak grid condition.
Disclosure of Invention
Aiming at the problems, the invention provides a grid-connected static stability evaluation method based on converter limit transmission power, which improves the accuracy of analyzing a steady-state working area along with the change of line impedance characteristics under a weak power grid.
In order to achieve the purpose, the technical scheme of the invention is as follows: the method comprises the following steps:
s1, representing grid-connected power grid strength of the virtual synchronous converter system by using the short-circuit capacity ratio SCR;
s2, establishing an equivalent circuit of converter power transmission, and then determining a converter power transmission vector relation; secondly, calculating the transmitted active power P;
s3, deriving the maximum transmission power point P by differentiating the transmitted active power Pmax；
S4, calculating the minimum SCR of the short-circuit capacity ratio SCRminAnd determining the required conditions of grid-connected static stability.
In step S1, the grid strength of the virtual synchronous converter system grid connection is represented by a short-circuit capacity ratio:
Figure BDA0003241494840000021
wherein SCR is short-circuit capacity ratio, PscFor short-circuit capacity of AC mains, Psc＝3Ug 2/ZgWherein U isgAs effective value of the grid voltage, ZgIs the line impedance modulus;
Pconverterfor rated transmission power, P, of the convertersetThe rated transmission power of the virtual synchronous converter is obtained.
In step S2, the equivalent circuit includes a grid side and a converter side, the converter side includes a converter equivalent voltage source, and the grid side includes a line impedance.
According to the equivalent circuit, the vector relation of each variable in the converter power transmission equivalent circuit is established as follows:
Figure BDA0003241494840000022
in the formula of UcIs an equivalent voltage source of a converter, UgIs the effective value of the voltage of the power grid, I is the current, XgIs reactance, RgIs a resistance.
Calculating the transmitted active power P as:
Figure BDA0003241494840000031
in step S3, the reactance X in the active power P transmitted in step S2 is first determinedgResistance RgBy means of the line impedance modulus ZgAnd impedance angle
Figure BDA0003241494840000032
Is represented as follows:
Figure BDA0003241494840000033
then, the differentiation is performed to obtain:
Figure BDA0003241494840000034
the maximum transmission power point PmaxAt the point of maximum extreme value of current Ipole_maxAnd (4) solving the value as:
Figure BDA0003241494840000035
in step S4, under the condition that the virtual synchronous converter system is statically stable, the maximum transmission power point should satisfy the following inequality:
Figure BDA0003241494840000036
SCRmincalculated by the following formula:
Figure BDA0003241494840000037
meanwhile, the grid connection needs to meet the following conditions:
Figure BDA0003241494840000038
according to the method, based on the line impedance characteristics, the static stable working condition of the virtual synchronous converter system under the weak grid condition is calculated by deducing the maximum transmission power point and the minimum grid short-circuit capacity ratio of the converter, so that the analysis accuracy is improved, and the stable operation of the grid is ensured.
Meanwhile, the method provides theoretical support for grid-connected static stability evaluation based on the converter limit transmission power under the condition of weak power grid, lays a foundation for the follow-up small signal stability and transient stability research, and has certain significance.
Drawings
FIG. 1 is a flow chart of a converter grid-connected static stability evaluation method provided by the invention;
FIG. 2 is an equivalent circuit diagram of the power transmission of the converter provided by the present invention;
FIG. 3 is a power transmission vector diagram of a converter provided by the present invention;
FIG. 4 is a P-I curve for different line impedance characteristics provided by the present invention;
FIG. 5 is P provided by the present inventionmaxAnd Zg、
Figure BDA0003241494840000041
A graph of (a);
FIG. 6 is a schematic representation of the present invention
Figure BDA0003241494840000042
A curve;
FIG. 7 is a waveform diagram of the variation of transmission power provided by the present invention;
fig. 8 is a graph of (a) an output current waveform and (b) an output voltage waveform at a transmission power of 10kW provided by the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the drawings of the embodiments of the present invention. It is to be understood that the embodiments described are only a few embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the described embodiments of the invention, are within the scope of the invention.
Therefore, the invention provides a grid-connected static stability evaluation method based on converter limit transmission power. According to the invention, expressions of the maximum transmission power of the converter grid connection and the minimum power grid short-circuit capacity ratio are deduced according to the virtual synchronous converter system equivalent power transmission model, and researches are performed based on the change of line impedance characteristics under weak power grids and mainly aiming at the change conditions of the system static stability working area under different power grid strengths. Finally, the effectiveness of theoretical analysis is verified by simulation.
The present invention, as shown in fig. 1-8, comprises the following steps:
s1, representing grid-connected power grid strength of the virtual synchronous converter system by using the short-circuit capacity ratio SCR;
s2, establishing an equivalent circuit of converter power transmission, determining a converter power transmission vector relation, calculating the transmitted active power P and analyzing P-I curves under different impedance characteristics;
s3, deriving the maximum transmission power point P by differentiating the transmitted active power Pmax(maximum extreme point I)pole_max)；
S4, analyzing the influence of the power grid intensity change on the steady-state working area of the system, and calculating to obtain the SCRminAnd determining the required conditions of grid-connected static stability.
The method comprises the steps of firstly establishing the power grid strength through the step S1, then calculating the transmission power of the converter according to a specific network topology structure through the step S2, deriving the maximum transmission power point in the step S3 based on the result, and finally giving a grid-connected static stability condition through the step S4.
Through the derivation of the steps, the static stability criterion can be rapidly and conveniently derived according to the specific converter grid-connected topological structure, and the quantitative analysis and stabilization mechanism is realized.
In step S1, according to the definition related to the evaluation of the grid strength in the power system, the grid strength of the virtual synchronous converter system grid connection is represented by the short-circuit capacity ratio:
Figure BDA0003241494840000051
in the formula, SCR is a short-circuit capacity ratio, and the larger the value, the higher the grid-connection strength, and PscFor short-circuit capacity of AC mains, Psc＝3Ug 2/ZgWherein U isgAs effective value of the grid voltage, ZgIs the line impedance modulus, PconverterThe rated transmission power of the converter is P corresponding to the rated transmission power in the virtual synchronous converterset。
In step S2, an equivalent circuit of the converter power transmission is established, and a vector relationship diagram of each variable in the equivalent circuit of the converter power transmission is established according to the circuit theorem and in combination with the relationship of each variable in the equivalent circuit diagram, so that the vector relationship of each variable can be obtained:
Figure BDA0003241494840000052
in the formula of UcIs an equivalent voltage source of a converter, UgIs the effective value of the voltage of the power grid, I is the current, XgIs reactance, RgIs a resistance.
Calculating the transmitted active power P as:
Figure BDA0003241494840000053
analyzing the P-I curve under different impedance characteristics to determine whether the transmitted active power P is influenced by the impedance characteristics of the line, including the module value Z of the line impedancegAnd angle of impedance
Figure BDA0003241494840000054
Through the correlation analysis of the static stability, the maximum transmission power point is known to be the key influencing the static stability.
In step S3, the following arrangement is firstly made for the active power P formula transmitted in step S2:
Figure BDA0003241494840000055
i.e. reactance XgResistance RgBy means of the line impedance modulus ZgAnd impedance angle
Figure BDA0003241494840000056
Represents;
then, the differentiation is performed to obtain:
Figure BDA0003241494840000061
maximum transmission power point PmaxThe pole of the p (i) function can be obtained by setting dP/dI to 0. Maximum transmission power point PmaxShould be obtained at the point where the current I assumes the maximum extreme value, and therefore assumes the maximum extreme value Ipole_maxAt the time corresponding to the maximum transmission power point PmaxThe value can be solved as:
Figure BDA0003241494840000062
the above formula shows that the line impedance modulus value ZgAnd angle of impedance
Figure BDA0003241494840000063
The change of the voltage can directly influence the maximum transmission power point of the virtual synchronous converter system, and can be realized by establishing PmaxAnd ZgAnd
Figure BDA0003241494840000064
the graphs of (a) were further observed and analyzed.
In step S4, the analysis shows that as the grid strength decreases, the line impedance module value ZgThe maximum transmission power point P of the virtual synchronous converter system is increased continuouslymaxAnd rapidly decreases. Under the condition of ensuring the static stability of the virtual synchronous converter system, the maximum transmission power point should satisfy the following inequality:
Figure BDA0003241494840000065
SCRmincalculated by the following formula
Figure BDA0003241494840000066
Further, according to the analysis of the above formula, in order to ensure the static stability of the virtual synchronous converter, the grid connection needs to satisfy the following conditions:
Figure BDA0003241494840000067
in the above step S2, an equivalent circuit of the converter power transmission is established as shown in fig. 2. In the figure, UcAnd UgSetting the power grid side as a reference phase for the effective values of the equivalent voltage source and the power grid voltage of the converter, wherein the phase at the converter side is the output power angle theta of the active loop of the converter, and the line impedance
Figure BDA0003241494840000068
Where j is an imaginary unit. For simplifying analysis, the default system power factor is 1, and at this time, the corresponding converter output current and voltage are in phase and can be represented by I & lttheta & gt.
In application, the corresponding equivalent circuit is properly adjusted according to a specific network topology structure.
Specifically, in the present embodiment, according to the circuit theorem, a vector relationship diagram of each variable in the converter power transmission equivalent circuit is established in combination with the relationship of each variable in fig. 2, as shown in fig. 3. From this a specific expression of the transmitted active power P is derived. The active power P and the current I are subjected to per unit processing, and a P-I curve under different line impedance characteristics can be established according to a P formula, as shown in fig. 4, it can be seen that the total of the active power P with the increase of the current I shows a trend of increasing first and then decreasing, and a maximum value P existsmax. Angle of impedance
Figure BDA0003241494840000071
Increase of (i.e. R)g/XgThe value becomes smaller, the maximum value P thereofmaxWill also decrease. In other words, the maximum transmission power of the system will increase as the resistive component of the line impedance increases, all other things being equal.
According to the correlation analysis of the static stability of the system, in the virtual synchronous converter system, because the quasi-power control mode is adopted, the condition for ensuring the static stability of the system can be considered as that the reference value of the active power output by the system cannot be larger than the maximum valueTransmission power value, i.e. Pmax≥Pset. From the image point of view, when P in FIG. 4setWhen the curve and the P-I curve do not have an intersection point, the virtual synchronous converter system does not have a steady-state working point, and the system is statically unstable at the moment.
In step S3, the pole of the p (i) function is determined by setting dP/dI to 0. As can be seen from the observation of the dP/dI formula, the number of poles of the function is 4, and two poles of the function are positive roots and negative roots. The negative root can be directly cut off according to the function independent variable constraint condition, and meanwhile, the maximum transmission power point P can be known by combining the curve of the figure 4maxShould be obtained at the point where the current I assumes the maximum extreme value, and therefore assumes the maximum extreme value Ipole_maxAt the time corresponding to the maximum transmission power point Pmax. From PmaxAccording to the formula, the line impedance module value ZgAnd angle of impedance
Figure BDA0003241494840000072
The variation of the voltage can directly influence the maximum transmission power of the virtual synchronous converter system. PmaxAnd Zg、
Figure BDA0003241494840000073
As shown in fig. 5.
In step S4, as the grid strength decreases, the line impedance module value ZgThe maximum transmission power P of the virtual synchronous converter system is increased continuouslymaxAnd rapidly decreases. At PmaxDuring the falling process, the value of the power control signal will continuously approach the power command value PsetUntil P appearsset>PmaxIn order to avoid the system from static instability, the transmission power command value must be reduced, which results in a smaller steady-state operating region of the system. Albeit line impedance angle
Figure BDA0003241494840000075
The increase of (2) can raise the maximum transmission power of the system to a certain extent, but from the graph, the situation with a larger raising degree only occurs
Figure BDA0003241494840000076
I.e. the moment when the line impedance mainly exhibits resistive characteristics, this characteristic is difficult to satisfy in practical situations, while under other resistive or inductive conditions, the line impedance angle has little effect on increasing the maximum transmission power of the system. Therefore, in general, as the strength of the power grid decreases, the steady-state operation area of the virtual synchronous converter system will be continuously reduced. The SCR minimum versus line impedance angle is shown in fig. 6.
Specifically, combining the above analysis, the following can be concluded:
1. the static stability of the virtual synchronous converter system can be controlled by the maximum transmission power PmaxReflection of, PmaxThe magnitude of (A) is related to the impedance characteristic of the line, the line impedance modulus ZgThe larger, PmaxSmaller, impedance angle
Figure BDA0003241494840000074
The larger, PmaxThe smaller;
2. as the grid strength weakens, the line impedance increases, PmaxAnd the system is small in steady-state working area and is easy to cause static instability. The resistive component of the line impedance is beneficial to improving the power transmission capability under the condition of weak power grid and improving the static stability, but the effect is very little in the actual scene;
3. to ensure the static stability of the system, the short-circuit capacity ratio SCR has a minimum value, which is determined by the line impedance angle
Figure BDA0003241494840000081
Determining an impedance angle
Figure BDA0003241494840000082
Smaller, SCRminThe smaller.
With Zg＝10.05、
Figure BDA0003241494840000083
The line impedance parameters of (1) are taken as an example, simulation analysis is carried out, and the other parameters are consistent with the parameters. According to the condition that the grid connection needs to be met, the grid connection is corresponding to the conditionThe system working condition of (1) should satisfy Pset≤Pmax7.2kW, SCR is more than or equal to 1.98.
First, the maximum transmission power point of the system under the weak grid condition is found. Setting the virtual synchronous converter system in the simulation model to be connected to the grid at 1.6s, wherein the initial transmission power is 5kW, and increasing the active power at the speed of 1kW/s at the simulation time of 3.5s, and the corresponding waveform change diagram is shown in FIG. 7. As can be seen, the transmission power peaks at approximately 5.9s at the simulation time and then no longer increases following a given power command value, and it can be seen that the system will enter a destabilizing state when the transmission power exceeds the maximum transmission power. Therefore, the maximum transmission power of the system under the condition of the line parameters is about 7.05 kW. According to PmaxFormula, at this time PmaxThe theoretical value of the model is 7.2kW, and the simulation result is basically consistent.
Meanwhile, the operating condition of the system for transmitting 10kW of active power is observed under the condition of the line impedance parameter, and theoretical analysis shows that the system is in a static instability state at the moment, and the simulation waveforms of the output voltage and the current are shown in FIG. 8. As can be seen from the figure, the output voltage and the current of the system show large-amplitude low-frequency (<1Hz) non-periodic oscillation, the oscillation characteristics are greatly different from small disturbance instability, and the system has the characteristics that the system can not be synchronized with an alternating current power grid all the time after the calculation of a controller, and the system does not have a stable working point.
Due to the adoption of the technical scheme, the invention has the following advantages:
1. on the basis of analyzing the instability type of the power electronic converter, the stability problem of static stability of a virtual synchronous converter system is researched based on an impedance analysis method. Under the power frequency, based on the line impedance characteristic, the static stable working condition of the virtual synchronous converter system under the weak grid condition is calculated by deducing the maximum transmission power point and the minimum grid short-circuit capacity ratio of the converter, and the correctness and the effectiveness of the provided index system are analyzed by an example.
2. The invention overcomes the defects of the prior art, the prior art only carries out power grid strength analysis aiming at the operating conditions that the traditional generating set has larger installed capacity occupation ratio and a small amount of power electronic equipment is accessed, however, under the background of high power electronic penetration, because the line impedance is not negligible, the interaction of the power grid is more intense, and the instability problem is more obvious. Because the generation mechanism of the stability problems is different from that of the traditional power system and cannot be explained by using the traditional power system stability analysis method, research needs to be carried out on the grid-connected stability mechanism of the power electronic converter under the weak grid condition. The method provides theoretical support for grid-connected static stability evaluation based on the converter limit transmission power under the condition of weak power grid, lays a foundation for the follow-up small signal stability and transient stability research, and has certain significance.
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 present application is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the application. It will be understood that each flow and/or block of the flow diagrams and/or block diagrams, and combinations of flows and/or blocks in the flow diagrams 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.

Claims (7)

1. A grid-connected static stability evaluation method based on converter limit transmission power is characterized by comprising the following steps:
s1, representing grid-connected power grid strength of the virtual synchronous converter system by using the short-circuit capacity ratio SCR;
s2, establishing an equivalent circuit of converter power transmission, and then determining a converter power transmission vector relation; secondly, calculating the transmitted active power P;
s3, deriving the maximum transmission power point P by differentiating the transmitted active power Pmax；
S4, calculating the minimum SCR of the short-circuit capacity ratio SCRminAnd determining the required conditions of grid-connected static stability.
2. The grid-connected static stability assessment method based on the converter limit transmission power as claimed in claim 1, wherein in step S1, the grid strength of the virtual synchronous converter system grid-connected is represented by the short-circuit capacity ratio:
Figure FDA0003241494830000011
wherein SCR is short-circuit capacity ratio, PscFor short-circuit capacity of AC network，Psc＝3Ug 2/ZgWherein U isgAs effective value of the grid voltage, ZgIs the line impedance modulus;
Pconverterfor rated transmission power, P, of the convertersetThe rated transmission power of the virtual synchronous converter is obtained.
3. The grid-connected static stability assessment method based on the limit transmission power of the converter according to claim 2, wherein in step S2, the equivalent circuit comprises a grid side and a converter side, the converter side comprises a converter equivalent voltage source, and the grid side comprises a line impedance.
4. The grid-connected static stability assessment method based on the converter limit transmission power as claimed in claim 3, characterized in that, according to the equivalent circuit, the vector relationship of each variable in the converter power transmission equivalent circuit is established as follows:
Figure FDA0003241494830000012
in the formula of UcIs an equivalent voltage source of a converter, UgIs the effective value of the voltage of the power grid, I is the current, XgIs reactance, RgIs a resistance.
5. The grid-connected static stability assessment method based on converter limit transmission power as claimed in claim 4, wherein the active power P of the transmission is calculated as:
Figure FDA0003241494830000013
6. the grid-connected static stability assessment method based on the converter limit transmission power as claimed in claim 5, wherein in step S3, the active power P transmitted in step S2 is first determinedReactance X ofgResistance RgBy means of the line impedance modulus ZgAnd impedance angle
Figure FDA0003241494830000014
Is represented as follows:
Figure FDA0003241494830000021
then, the differentiation is performed to obtain:
Figure FDA0003241494830000022
the maximum transmission power point PmaxAt the point of maximum extreme value of current Ipole_maxAnd (4) solving the value as:
Figure FDA0003241494830000023
7. the grid-connected static stability assessment method based on the converter limit transmission power as claimed in claim 1, wherein in step S4, under the condition of static stability of the virtual synchronous converter system, the maximum transmission power point should satisfy the following inequality:
Figure FDA0003241494830000026
SCRmincalculated by the following formula:
Figure FDA0003241494830000024
meanwhile, the grid connection needs to meet the following conditions:
Figure FDA0003241494830000025
CN202111021287.2A 2021-09-01 2021-09-01 Grid-connected static stability evaluation method based on converter limit transmission power Active CN113725908B (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CN202111021287.2A CN113725908B (en) 2021-09-01 2021-09-01 Grid-connected static stability evaluation method based on converter limit transmission power

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CN202111021287.2A CN113725908B (en) 2021-09-01 2021-09-01 Grid-connected static stability evaluation method based on converter limit transmission power

Publications (2)

Publication Number Publication Date
CN113725908A true CN113725908A (en) 2021-11-30
CN113725908B CN113725908B (en) 2022-10-28

Family

ID=78680571

Family Applications (1)

Application Number Title Priority Date Filing Date
CN202111021287.2A Active CN113725908B (en) 2021-09-01 2021-09-01 Grid-connected static stability evaluation method based on converter limit transmission power

Country Status (1)

Country Link
CN (1) CN113725908B (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP4280408A1 (en) * 2022-05-17 2023-11-22 Hitachi Energy Switzerland AG Method and system for evaluating a condition of a power grid

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN107492894A (en) * 2017-09-05 2017-12-19 淮南联合大学 A kind of node voltage static stability appraisal procedure of the power system containing wind power plant
CN113131526A (en) * 2021-04-07 2021-07-16 国家电网有限公司 Static stability control method for wind-fire bundling system with virtual inertia control

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN107492894A (en) * 2017-09-05 2017-12-19 淮南联合大学 A kind of node voltage static stability appraisal procedure of the power system containing wind power plant
CN113131526A (en) * 2021-04-07 2021-07-16 国家电网有限公司 Static stability control method for wind-fire bundling system with virtual inertia control

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP4280408A1 (en) * 2022-05-17 2023-11-22 Hitachi Energy Switzerland AG Method and system for evaluating a condition of a power grid
US12061243B2 (en) 2022-05-17 2024-08-13 Hitachi Energy Ltd Method and system for evaluating a condition of a power grid

Also Published As

Publication number Publication date
CN113725908B (en) 2022-10-28

Similar Documents

Publication Publication Date Title
Hu et al. Impedance-based analysis and stability improvement of DFIG system within PLL bandwidth
CN113346513B (en) Method for identifying forced subsynchronous oscillation of direct-drive fan
CN113725908B (en) Grid-connected static stability evaluation method based on converter limit transmission power
CN111130136A (en) Subsynchronous oscillation suppression method based on additional virtual impedance control
CN115021277A (en) Control method and system for improving damping characteristic of new energy through flexible direct current transmission
CN110336279B (en) Electric power system oscillation self-adaptive suppression method, system and medium based on grid-connected converter
CN102651550A (en) Sub-synchronous oscillation suppression method based on controllable series compensation additional impedance deviation control
Chen et al. Voltage control impact on performance of virtual synchronous generator
CN117375086A (en) Main power source type doubly-fed wind field damping control method based on multi-machine parameter adjustment
CN111769592A (en) Virtual harmonic resistance control method of grid-connected inverter based on parabola method
CN107526923B (en) Method and device for determining line loss rate of half-wavelength power transmission line
CN113794198B (en) Method, device, terminal and storage medium for suppressing broadband oscillation
CN114243762A (en) Analysis and control method for fan grid connection
CN114006387A (en) Adaptive frequency subsynchronous oscillation suppression method and system based on multi-branch impedance
CN114336736A (en) Energy storage inverter grid-connected system stability improvement method based on current mode control
Krishnamoorthy et al. A novel, empirical equation—Based shunt active filter for harmonic elimination and power factor correction, using a modified PSO algorithm
CN111181455A (en) Self-adaptive tracking control method and system for maximum power point of doubly-fed wind generator
CN111416377A (en) Flexible direct current control method and device for improving transient stability of power grid
CN115498654B (en) Virtual inertia control method of permanent magnet synchronous fan based on fuzzy logic control
Ren et al. Impedance shaping of grid-connected converter based on gershgorin disc theorem and return ratio matrix
Huang et al. Research on harmonic impedance characteristics of doubly-fed induction generator
Zhu et al. Analysis of Static Stability of Virtual Synchronous Converter Based on Line Impedance Characteristics
CN116470569B (en) Method and device for determining dynamic impedance interval of full-power wind turbine generator
CN111416343B (en) Method, device and medium for evaluating DC power boost of power system
Li et al. Harmonic resonance modal analysis of Multi-inverter Grid-connected system

Legal Events

Date Code Title Description
PB01 Publication
PB01 Publication
SE01 Entry into force of request for substantive examination
SE01 Entry into force of request for substantive examination
GR01 Patent grant
GR01 Patent grant