CN102682358B - A kind of assessment wind-electricity integration scale and Net Frame of Electric Network adaptive planning simulation method - Google Patents

Abstract

The invention provides a kind of assessment wind-electricity integration scale and Net Frame of Electric Network adaptive planning simulation method, comprise the steps: (1). programme is carried out steady-state analysis, according to steady-state analysis result, described power network planning scheme is adjusted；(2). programme is dynamically analyzed, according to dynamic analysis result, described power network planning scheme is adjusted；(3). wind-powered electricity generation scale and grid-connected near region rack are carried out cross-impact analysis, according to cross-impact analysis result, described power network planning scheme is adjusted；(4). described power network planning scheme is modified verification, draws the programme of revised wind-powered electricity generation power supply and electric network coordination.The assessment wind-electricity integration scale that the present invention provides and Net Frame of Electric Network adaptive planning simulation method; can count and after scale wind-electricity integration due to its multi fan type and response characteristic diversity and the impact on power system dynamic step response of the wind-resources characteristic comprehensively, may advantageously facilitate the coordinated development of grid connected wind power and Electric Power Network Planning.

Description

Planning simulation method for evaluating adaptability of wind power grid-connected scale and power grid network frame

Technical Field

The invention belongs to the field of renewable energy power generation grid-connected planning, and particularly relates to a planning simulation method for evaluating wind power grid-connected scale and power grid network frame adaptability.

Background

After the intermittent wind power renewable energy source is connected to the grid on a large scale, the operation mode of a power system can be greatly changed due to randomness and fluctuation of the intermittent wind power renewable energy source. Such as rotational reserve rate, system peak shaving, fm service scheduling, etc. On the other hand, due to the self power production characteristics of renewable energy sources, the system characteristics are also affected after large-scale access. Therefore, it is necessary to deeply analyze changes of dynamic characteristics such as active, reactive, frequency, voltage and the like of the system after the renewable energy is accessed in a large scale.

In the wind power industry of countries in the world, the wind power development of the broad countries in which the uniform is in force presents the following characteristics: the development speed is fast, the wind power plant scale is large, the transmission distance is long, and the voltage level is high. The above characteristics of wind power development and the problems of frequent wind change, uncontrollable wind power, non-uniform wind energy resource distribution and other wind characteristics bring important challenges to wind power grid-connected planning.

(1) In terms of wind resource characteristics, wind power has the characteristics of randomness and intermittency, so that the wind power is difficult to preset and implement an accurate power generation plan like a conventional power supply. (2) In terms of fan characteristics, the influence of the wind turbine generator on the safety and stability of a power grid is different from that of a conventional synchronous generator set, the wind turbine generator adopting an asynchronous machine generates active power and absorbs idle power, and the voltage control is difficult. (3) In countries where the serviceman is in a large area, the geographic position of a wind power plant is generally far away, the grid structure at a grid-connected point is generally not strong enough, the power structure is single, the system is relatively weak, and the large-scale wind power access has great influence on the planning of the original grid in the areas.

With the enlargement of the scale of the wind power plant, the proportion of the wind power installation in the power grid is higher and higher, the access voltage level is improved, and the influence range of the wind power installation on the power grid is gradually enlarged from part. Through the wind power development planning in China, the large-scale wind power generation is intensively connected into the power grid, new challenges are provided for the planning, development and stable operation of the power grid, no ready experience can be used for reference in the world, and corresponding research needs to be carried out on the coordination problem of the wind turbine generator and the power grid under the large-scale wind power connection.

Due to the fact that the renewable energy sources are long in development and utilization time and are mostly connected to the power grid in a dispersed mode, research is mainly focused on the influence on the power distribution network, and the reference significance is small for the large-scale centralized connection condition. With the rapid development of renewable energy power generation, students are more and more concerned about the influence of large-scale access on a power grid, and the content relates to multiple levels of a power supply, a main network, a distribution network and the like and multiple angles of planning, designing, operating and the like. However, a more complete and clear idea, strategy and framework has not been formed.

Disclosure of Invention

In order to overcome the defects, the invention provides a planning simulation method for evaluating the adaptability of the wind power grid-connected scale and the grid structure of the power grid, which can comprehensively take account of the influence of the multi-fan type, the response characteristic difference and the wind resource characteristic on the dynamic characteristic of the power system after large-scale wind power grid connection, accurately evaluate the impact and the safety bottleneck of the wind power grid connection on the power grid connection, and is favorable for promoting the coordinated development of the grid-connected wind power and power grid planning.

In order to achieve the aim, the invention provides a planning simulation method for evaluating the adaptability of a wind power grid-connected scale and a power grid network frame, which adjusts a planning scheme for coordinating a wind power supply and a power grid, and is improved in that the method comprises the following steps:

(1) carrying out steady state analysis on the planning scheme, and adjusting the power grid planning scheme according to a steady state analysis result;

(2) dynamically analyzing the planning scheme, and adjusting the power grid planning scheme according to the dynamic analysis result;

(3) analyzing the mutual influence between the wind power scale and the grid-connected near-zone grid structure, and adjusting the power grid planning scheme according to the mutual influence analysis result;

(4) and correcting and checking the power grid planning scheme to obtain a corrected wind power supply and power grid coordination planning scheme.

In the preferred technical scheme provided by the invention, the steady state analysis, the dynamic analysis and the mutual influence analysis of the wind power scale and the grid-connected near-zone grid structure respectively call a wind power supply simulation method suitable for grid source coordination planning analysis.

In a second preferred technical solution provided by the present invention, the wind power supply simulation method adapted to grid-source coordination planning analysis includes: reasonable equivalence processing of static characteristics of the wind power supply, accurate simulation of dynamic characteristics of the wind power supply and difference processing of actual characteristics of the wind power supply.

In the third preferred technical scheme provided by the invention, the reasonable equivalence processing of the static characteristics of the wind power supply comprises the following steps: in a wind power plant, a wind turbine generator adopts unit wiring of 1 machine and 1 transformer, and the models of the transformers are the same; collecting a plurality of wind turbine generators on the high-voltage side of a transformer, and connecting the wind turbine generators to the low-voltage side of a main transformer station of a wind power plant through 1 collecting line; the active loss and the reactive loss of the current on the transformer are respectively as follows:

${\mathrm{\ΔP}}_i=\frac{P_i^2+Q_i^2}{U_{\mathrm{it}}^2}{R}_i,$ ${\mathrm{\ΔQ}}_i=\frac{P_i^2+Q_i^2}{U_{\mathrm{it}}^2}{X}_i$

wherein, P_i、Q_iInjecting active power and reactive power into a transformer connected with the ith wind turbine generator set; u shape_it、R_i、X_iThe voltage, the equivalent resistance and the equivalent reactance of the transformer are respectively; delta P_i、ΔQ_iThe active loss and the reactive loss of the current on the transformer are respectively; therefore, the power injected into the current collecting circuit by the ith wind turbine generator set is as follows:

$P_i^{\′}+{\mathrm{jQ}}_i^{\′}=(P_i-{\mathrm{\ΔP}}_i)+j(Q_i-{\mathrm{\ΔQ}}_i)$

wherein,respectively injecting active power and reactive power of a current collection circuit into the ith wind turbine generator set;

meanwhile, according to the voltage drop phasor diagram, the following can be obtained:wherein,are respectively asAnd U_itAndandthe included angle between the phasors; AB represents the length of the AB section line; from this formula can obtain the active power of every wind turbine generator system transformer high pressure side exitReactive powerAnd power factor

When a plurality of wind turbine generators are connected in parallel to the same current collecting line, the power factors are respectively set as The total power output at the high-voltage side outlet of the transformer of the wind turbine generator is as follows:

wherein P is_i、Q_iThe total active power and the total reactive power output from the high-voltage side outlet of the transformer of the wind turbine generator set,the active power of the nth wind turbine generator set and the included angle of the voltage and current phasor of the nth wind turbine generator set are respectively included, in the wind power plant, each wind turbine generator set can be equivalent to 1 wind turbine generator set by the above formula, and the capacity of the equivalent wind turbine generator set is equal to the sum of the capacities of each wind turbine generator; for the whole wind power plant, the wind power plant can be equivalent to 1 or more wind power plants according to factors such as parameters of the wind power plants and transformer of the wind power plants, and each equivalent wind power plant is taken as a PQ node during load flow calculation, so that the capacity S of the equivalent wind power plant is as follows:

$S_{\mathrm{\Σ\Σ}}=\underset{i=1}{\overset{n}{\mathrm{\Σ}}}\underset{j=1}{\overset{m}{\mathrm{\Σ}}}{S}_{i,j}=\underset{i=1}{\overset{n}{\mathrm{\Σ}}}\underset{j=1}{\overset{m}{\mathrm{\Σ}}}{P}_{i,j}^{\′}+\underset{i=1}{\overset{n}{\mathrm{\Σ}}}\underset{j=1}{\overset{m}{\mathrm{\Σ}}}{Q}_{i,j}^{\′}$

in the formula, i and j represent the positions of the wind turbines in the wind power plant, and n and m respectively represent the number of fans on each current collecting line in the wind power plant and the number of the current collecting lines in the wind power plant;

during load flow calculation, current collecting lines inside a wind power plant are equivalent to 1 equivalent impedance according to the arrangement of wind turbine generators, wherein the current collecting lines inside the wind power plant are divided into two types, namely direct-buried cables and overhead lines; due to the fact that parameter difference between a cable line and an overhead line is large, equivalent values of the current collecting lines in the wind power plant are required to be carried out according to the types of the current collecting lines.

In a fourth preferred technical solution provided by the present invention, the accurate simulation of the dynamic characteristics of the wind power supply includes: the wind generating set mostly adopts an asynchronous generator, and physical quantities needing equivalence are researched through a wind generator single machine mathematical model when equivalence of a wind power plant cluster is researched; equivalent key parameters of the wind power plant can be obtained by an asynchronous generator set mathematical model and a generator rotor motion model as follows:

T_Jequivalent inertia time constant:

similar to an asynchronous motor, the inertia time constant equivalence method of the rotor of the asynchronous generator weights according to the capacity to obtain: $T_J=\frac{1}{S_M}\underset{j=1}{\overset{n}{\mathrm{\Σ}}}{T}_j{S}_j;$

wherein S is_jAnd T_jRespectively refer to the capacity and inertia time of the jth asynchronous motorNumber, S_MIs the sum of the capacities of the asynchronous motors, T_JThe inertia time constant of the equivalent asynchronous machine is obtained, and n is the total number of the asynchronous machines;

s equivalent initial slip:

firstly, connecting the equivalent circuits of the asynchronous machines in parallel, and obtaining the equivalent resistance R of the two machines by using a Thevenin equivalent method_MThe slip s of the equivalent generator in the initial state can be obtained_M；

$s_M=\frac{R_M{(\frac{R_1}{s_1}+\frac{R_2}{s_2})}^2+R_M{(X_{l1}+X_{l2})}^2}{\left(\frac{R_1}{s_1}\right)[X_{l2}^2+{\left(\frac{R_2}{s_2}\right)}^2]+\left(\frac{R_2}{s_2}\right)[X_{l1}^2+{\left(\frac{R_1}{s_1}\right)}^2]}$

Wherein R is₁And R₂Respectively representing the sum of the resistances of the stator and the rotor of two motors, X_l1And X_l2Respectively representing the sum of leakage reactance of stator and rotor of motor, s₁、s₂Respectively representing the initial running slip of the two motors, wherein each physical quantity unit is a per unit value;

x is equivalent synchronous reactance, X' is equivalent transient reactance sumIs the equivalent rotor winding time constant;

the three parameters can be calculated according to the following formula:

$\left\{\begin{array}{c}X=X_s+X_m\\ X^{\′}=X_s+X_r{X}_m/(X_r+X_m)\\ T_0^{\′}=(X_r+X_m)/\left(2\mathrm{\π}{R}_r\right)\end{array}\right.$

in the formula, R_sIs a stator resistor; r_rIs the rotor resistance; x_sIs a stator reactance; x_rIs the rotor reactance; x_mIs an excitation reactance.

In a fifth preferred technical scheme provided by the present invention, the processing of the difference of the actual characteristics of the wind power supply comprises: the temporal and spatial differences are treated separately.

In a sixth preferred technical solution provided by the present invention, the time difference processing includes: determining an accumulative effect reduction function P of wind power plant wind resource characteristic correlation based on meteorological data w of the wind power plant according to the randomness of the output of the wind power plant, the dispersity of the distribution of the wind power plant and wind generating sets_WFPower output characteristic of f (w), where PWF represents the output power of the wind farm.

In a seventh preferred technical solution provided by the present invention, the spatial difference processing includes: an equivalent model is used in static and dynamic simulation, fans in a wind power plant are equivalent to a single equivalent unit, and a detailed wind power plant model is established; in the modeling process of the wind power plant detailed model, all parameters are used to obtain actual parameters of various devices of the wind power plant; if the situation that part of actual parameters are unknown exists, the most conservative situation in a reasonable range is considered;

the modeling of the wind power plant detailed model comprises the following steps: the wind power generation set comprises a wind power generation set, a box type transformer, a current collection circuit, a boosting transformer and an access system circuit.

In the eighth preferred technical scheme provided by the invention, in the step 1, the steady-state analysis calls the reasonable equivalence processing of the static characteristics of the wind power supply, and the influence of wind power on the power flow and the static safety of the power grid and the influence of wind power grid connection on the reactive voltage characteristics of the power grid are respectively analyzed.

In the ninth preferred technical scheme provided by the invention, in the step 2, the dynamic analysis calls the accurate simulation of the dynamic characteristics of the wind power supply, and the transient stability of the system after the wind power is accessed, the voltage stability of the system after the wind power is accessed, the frequency stability of the system after the wind power is accessed and the small interference stability of the system after the wind power is accessed are respectively analyzed.

In the tenth preferred technical solution provided by the present invention, in the step 3, the mutual influence analysis calls accurate simulation of the dynamic characteristics of the wind power supply, and analyzes the wind power sending capacity, the isolated network operation capacity, and the mutual influence of the wind power supply and the near-region conventional power supply, respectively.

In the preferred technical scheme provided by the invention, in the step 4, the difference processing of the actual characteristics of the wind power supply is called, and the power grid planning scheme is corrected and verified.

In a second preferred technical solution provided by the present invention, the influence of the wind power on the power flow of the power grid and the static safety analysis include: the influence of wind power integration on the planning power flow of a power grid and the load rate of power transmission and transformation equipment is analyzed, and whether the thermal stability limit constraint of the power transmission and transformation equipment is met under the condition of no fault disconnection is analyzed.

In a third preferred technical solution provided by the present invention, the analyzing of the influence of the wind power integration on the reactive voltage characteristics of the power grid includes: under the condition that a reactive power compensation device is not configured in the wind power plant, reactive power compensation scheme suggestions including inductive compensation under light load flow and capacitive compensation under heavy load flow are provided for voltage fluctuation of the access point and each substation in the nearby area caused by active power output change through calculation.

In a fourth preferred technical solution provided by the present invention, the analyzing the transient stability of the system after the wind farm is connected includes: after the wind power plant is accessed, N-1 fault checking and serious fault checking are carried out on the access system near area, and a constant power factor operation mode, a constant voltage operation mode and the condition of the existence of low voltage ride through capability of a fan are respectively researched.

In the fifth preferred technical scheme provided by the invention, the analysis of the system voltage stability after the wind power plant is accessed comprises calculating the dropping and recovery conditions of the bus voltage of each transformer substation after the wind power plant is accessed and the short circuit fault occurs in the near area of the access system; voltage stability of the system in case of severe failure; analyzing the influence of wind power plant access on the medium-term and long-term voltage stability of the system, and calculating the change condition of reactive power reserve of the system before and after the wind power plant access.

In a sixth preferred technical solution provided by the present invention, the analyzing of the frequency stability of the system after the wind farm is accessed includes: and calculating the frequency change condition of the isolated network system under the condition that the wind power plant access system is in isolated network operation in the near region and certain power is unbalanced, and frequency stabilizing measures.

In a seventh preferred technical solution provided by the present invention, the analyzing of the small interference stability of the system after the wind farm is accessed includes: and calculating the main low-frequency oscillation mode of the system, and comparing the damping ratio change conditions of the main oscillation modes before and after the wind power plant is accessed.

Compared with the prior art, the planning simulation method for evaluating the wind power grid-connected scale and the power grid network frame adaptability fully considers the characteristics of a large-scale wind power base, realizes accurate modeling of a wind turbine generator and reasonable equivalence of a large wind power plant, and is suitable for effective evaluation of differences of engineering application fans; the planning simulation method of the wind power supply, which can comprehensively consider the wind resource characteristics, the static state and the dynamic response characteristics of the fan and the actual characteristic difference of the wind power supply, is firstly and definitely provided, an integral analysis technical framework of the coordination planning of the wind power supply and the power grid under the large-scale wind power access is provided based on the method, and on the basis, a coordination planning analysis algorithm flow of the wind power supply and the power grid is developed, so that a technical means of simulation analysis is provided for promoting the coordination planning of the wind power supply and the power grid; the innovative research results expand the depth and the breadth of the simulation calculation work of the wind power grid-connected planning; moreover, the method can comprehensively and objectively take account of the influence of large-scale wind power base grid connection on a power system planning scheme for the first time, and accurately evaluate the impact of wind power access on a planning grid structure and the safety bottleneck. The method is beneficial to the coordinated planning of the wind power supply and the power grid, and has great significance for guiding the formulation of a reasonable wind power supply and grid planning scheme and ensuring the normal operation of the system after the wind power is connected.

Drawings

FIG. 1 is a schematic diagram of a typical wind farm wiring.

Fig. 2 is a schematic wiring diagram of a single wind turbine.

Fig. 3 is a vector diagram of voltage drop.

FIG. 4 is a detailed wiring diagram of a typical wind farm.

Fig. 5 is an overall analysis technology framework of coordination planning of a wind power supply and a power grid under large-scale wind power access.

Fig. 6 is a flow of a wind power supply and power grid coordination planning analysis algorithm.

Detailed Description

A planning simulation method for evaluating adaptability of a wind power grid-connected scale and a power grid network frame aims to effectively take account of influences of static characteristics and dynamic characteristics of a large-scale wind power base on the power grid network frame during grid connection in developing large-scale wind power grid-connected planning simulation analysis, accurately grasp restriction factors of a target planning network frame on grid-connected wind power, provide a corresponding grid source coordination planning scheme, and reasonably evaluate the correction degree of actual differences of arrangement, wind power types, fan characteristics and the like in a wind power field during wind power grid connection on the planning scheme. To this end, the following problems need to be solved: the method comprises the steps of wind turbine static characteristic simulation and dynamic characteristic simulation in planning simulation analysis, establishment of a perfect network source coordination planning flow scheme, correction analysis of a planning scheme by fan actual characteristic differences and the like. The wind power source simulation analysis principle suitable for network source coordination planning analysis and considering the differences of static characteristics, dynamic characteristics and actual characteristics of a large-scale wind power base is provided for the first time, based on the principle, the whole analysis process and framework of the wind power source and power grid coordination planning are developed, and a complete and clear analysis idea, a technical framework and a technical method are provided for power grid planning under large-scale wind power grid connection.

The technical content of the patent will be specifically described below.

Wind power supply simulation principle suitable for network source coordination planning analysis

Reasonable equivalence of static characteristics of wind power supply

A typical wind power plant is taken as an example to illustrate the reasonable equivalence principle of the static characteristics of the wind power supply.

In the wind farm shown in the attached figure 1, the wind turbine generator adopts 1-machine-1-variable unit wiring, and the types of the transformers are the same. Several wind power generator sets are collected at the high-voltage side of the transformer and are connected to the low-voltage side of the main transformer station of the wind power plant through 1 collecting line. The wiring of a single wind turbine is shown in the attached figure 2. The voltage drop phasor diagram of the ith wind turbine transformer is shown in fig. 3. The active loss and the reactive loss of the current on the transformer are respectively as follows:

${\mathrm{\ΔP}}_i=\frac{P_i^2+Q_i^2}{U_{\mathrm{it}}^2}{R}_i,$ ${\mathrm{\ΔQ}}_i=\frac{P_i^2+Q_i^2}{U_{\mathrm{it}}^2}{X}_i$

wherein, P_i、Q_iInjecting active power and reactive power into a transformer connected with the ith wind turbine generator set; u shape_it、R_i、X_iRespectively the voltage, the equivalent resistance and the equivalent reactance of the transformer. Delta P_i、ΔQ_iThe active loss and the reactive loss of the current on the transformer are respectively. Therefore, the power injected into the current collecting circuit by the ith wind turbine generator set is as follows:

$P_i^{\′}+{\mathrm{jQ}}_i^{\′}=(P_i-{\mathrm{\ΔP}}_i)+j(Q_i-{\mathrm{\ΔQ}}_i)$

wherein,and respectively injecting active power and reactive power of a current collection circuit for the ith wind turbine generator set. Meanwhile, according to the voltage drop phasor diagram, the following can be obtained:wherein,are respectively shown in figure 3And U_itAndandangle between phasors. The AB meaning is shown by the line length of the AB segment in FIG. 3. From this formula can obtain the active power of every wind turbine generator system transformer high pressure side exitReactive powerAnd power factor

When a plurality of wind turbine generators are connected in parallel to the same current collecting line, the power factors are respectively set as The total power output at the high-voltage side outlet of the transformer of the wind turbine generator is as follows:

wherein P is_i、Q_iThe total active power and the total reactive power output from the high-voltage side outlet of the transformer of the wind turbine generator set,the active power of the nth wind turbine generator set and the included angle of the voltage and current phasor of the nth wind turbine generator set are respectively included, in the wind power plant, each wind turbine generator set can be equivalent to 1 wind turbine generator set by the above formula, and the capacity of the equivalent wind turbine generator set is equal to the sum of the capacities of each wind turbine generator. For the whole wind power plant, the wind power plant can be equivalent to 1 or more wind power plants according to factors such as parameters of the wind power plants and transformer of the wind power plants, and each equivalent wind power plant is taken as a PQ node during load flow calculation, so that the capacity of the equivalent wind power plant is as follows:

$S_{\mathrm{\Σ\Σ}}=\underset{i=1}{\overset{n}{\mathrm{\Σ}}}\underset{j=1}{\overset{m}{\mathrm{\Σ}}}{S}_{i,j}=\underset{i=1}{\overset{n}{\mathrm{\Σ}}}\underset{j=1}{\overset{m}{\mathrm{\Σ}}}{P}_{i,j}^{\′}+\underset{i=1}{\overset{n}{\mathrm{\Σ}}}\underset{j=1}{\overset{m}{\mathrm{\Σ}}}{Q}_{i,j}^{\′}$

in the formula, i and j represent the positions of the wind turbines in the wind power plant, and n and m respectively represent the number of fans on each current collecting line in the wind power plant and the number of the current collecting lines in the wind power plant.

During load flow calculation, current collecting lines inside a wind power plant are equivalent to 1 equivalent impedance according to the arrangement of the wind generation sets, wherein the current collecting lines inside the wind power plant are divided into two types, namely direct-buried cables and overhead lines. Due to the fact that parameter difference between a cable line and an overhead line is large, equivalent values of the current collecting lines in the wind power plant are required to be carried out according to the types of the current collecting lines.

(2) Accurate simulation of dynamic characteristics of wind power supply

When a large grid-connected wind power plant model is researched, because the wind power plant is composed of a large number of wind turbines, the mathematical model of the wind power plant is established based on the mathematical model of the wind turbines, but a single-machine model cannot be simply applied, the characteristics of the wind power plant are considered, and wind power plant models with different detailed degrees are equivalent aiming at different research problems.

When the stability problem of a power system containing a wind power plant is researched, although each generator in the wind power plant can be represented by a full-transient model of an asynchronous generator, the number of generators in the wind power plant is large, so that the time of simulation calculation is long when the model is applied, and the traditional full-transient model is not suitable for the simulation calculation of the wind power plant. Therefore, a complete algorithm needs to be designed to make a proper mathematical description on the wind power plant dynamic equivalent link.

The wind generating set mostly adopts an asynchronous generator, and when the equivalence of a wind power plant cluster is researched, the physical quantity needing the equivalence is researched through a single-machine mathematical model of the wind power generator. Equivalent key parameters of the wind power plant can be obtained by an asynchronous generator set mathematical model and a generator rotor motion model as follows:

T_Jequivalent time constant of inertia

Similar to an asynchronous motor, the inertia time constant equivalence method of the rotor of the asynchronous generator weights according to the capacity to obtain: $T_J=\frac{1}{S_M}\underset{j=1}{\overset{n}{\mathrm{\Σ}}}{T}_j{S}_j;$

wherein S is_jAnd T_jRespectively refer to the capacity and inertia time constant, S, of the jth asynchronous motor_MIs the sum of the capacities of the asynchronous motors, T_JAnd n is the total number of the asynchronous motors.

S equivalent initial slip

Firstly, connecting the equivalent circuits of the asynchronous machines in parallel, and obtaining the equivalent resistance RM of the two machines by using a Thevenin equivalent method to obtain the slip sM of the equivalent generator in an initial state.

$s_M=\frac{R_M{(\frac{R_1}{s_1}+\frac{R_2}{s_2})}^2+R_M{(X_{l1}+X_{l2})}^2}{\left(\frac{R_1}{s_1}\right)[X_{l2}^2+{\left(\frac{R_2}{s_2}\right)}^2]+\left(\frac{R_2}{s_2}\right)[X_{l1}^2+{\left(\frac{R_1}{s_1}\right)}^2]}$

Wherein R is₁And R₂Respectively representing the sum of the resistances of the stator and the rotor of two motors, X_l1And X_l2Respectively representing the sum of leakage reactance of stator and rotor of motor, s₁、s₂And respectively representing the initial running slip of the two motors, wherein each physical quantity unit is a per-unit value.

X equivalent synchronous reactance

X' equivalent transient reactance

Equivalent rotor winding time constant

The three parameters can be calculated according to the following formula:

$\left\{\begin{array}{c}X=X_s+X_m\\ X^{\′}=X_s+X_r{X}_m/(X_r+X_m)\\ T_0^{\′}=(X_r+X_m)/\left(2\mathrm{\π}{R}_r\right)\end{array}\right.$

in the formula, R_s-a stator resistance; r_r-a rotor resistance; x_s-a stator reactance; x_r-a rotor reactance; x_m-an excitation reactance.

(3) Wind power supply actual characteristic difference processing in planning scheme correction and verification

When the influence of wind power integration on a power grid is analyzed, static and dynamic equivalent models are adopted in large-scale wind power bases. When the analysis conclusion shows that the planning power grid is not suitable for wind power access and the original power grid planning scheme needs to be corrected, the difference between the equivalent model and the actual situation needs to be considered in the correction verification analysis so as to ensure the correctness of the proposed planning and correction scheme. The processing principle of the difference of the actual characteristics of the wind power supply comprises time difference and space difference. The following detailed analysis

(a) Temporal difference

The wind power plant is greatly different from a conventional power plant, the output of the wind power plant is influenced by the motive power wind of the wind power plant and randomly fluctuates, and the output of the wind power plant is lower than the rated capacity of the wind power plant under most conditions; secondly, one area may have a plurality of wind power plants, that is, the distribution of the wind power plants in one area is scattered; thirdly, a wind farm often consists of tens, hundreds or even hundreds of wind turbines, i.e. the distribution of the wind turbines of the wind farm is decentralized. Due to the randomness of the output of the wind power plant and the dispersion of the wind power plant and the wind generating set, the correlation problem of the wind power plant needs to be researched based on meteorological data w of the wind power plant, the power output characteristic of the cumulative effect reduction function F (w) of the wind resource characteristic correlation of the wind power plant is determined, and a basis is provided for the calculation of a power system.

(b) Spatial diversity

In static and dynamic simulation of the wind turbine generator, due to the fact that an equivalent model is used, a plurality of fans are equivalent to form a single equivalent generator, and certain deviation of an analysis result is possibly caused. Therefore, in the verification analysis, a detailed model thereof needs to be considered as needed.

In the detailed modeling process of the wind power plant, all parameters should use actual parameters of various devices of the wind power plant obtained by collecting resources. If some conditions exist in which the actual parameters are unknown, the conditions are considered according to the most conservative conditions in the reasonable range.

The detailed modeling of the wind power plant comprises the following steps: the wind power generation system comprises a wind power generation set (each fan is independently modeled), a box type transformer (cables from the fans to the box type transformer are omitted), a current collection circuit, a step-up transformer and an access system circuit. As shown in particular in figure 4.

Integrated analysis technology framework for coordination planning of wind power supply and power grid under large-scale wind power access

The overall analysis technology framework of the coordinated planning of the wind power supply and the power grid must contain analysis contents of the influence of wind power integration on various aspects of the power grid, the influence of factors such as power grid faults on the wind power supply and the like. The specific analysis technique includes the following parts, which may be appropriately selected in practical applications.

(1) Analysis of influence of wind power integration on planning of steady-state characteristics of power grid

(a) Influence of wind power integration on power flow of power grid and static safety analysis

Analyzing the influence of wind power integration on planning power flow of a power grid and load rate of power transmission and transformation equipment (lines and transformers); and analyzing whether the thermal stability limit constraint of the power transmission and transformation equipment is met under the fault-free on-off condition.

(b) Analysis of influence of wind power integration on reactive voltage characteristics of power grid

The partial analysis mainly shows the problem of fluctuation of bus voltages of the access point and each transformer substation in the nearby area caused by the change of the active output of the wind power plant under the condition that the reactive power compensation device is not configured in the wind power plant through calculation and analysis; and then, proposing reactive compensation proposal under various possible conditions through calculation.

Analysis of influence of wind power integration on dynamic characteristics of planned power grid

(a) System transient stability analysis after wind power plant access

After the wind power plant is accessed, N-1 fault checking and serious fault checking are carried out on the access system near area, and various conditions of various different operation modes, the existence of low voltage ride through capability and the like of a fan are respectively researched.

(b) System voltage stability analysis after wind power plant access

Calculating the dropping and recovery conditions of the bus voltage of each transformer substation after the wind power plant is accessed and the short circuit fault occurs in the near area of the access system; voltage stability of the system in case of severe failure; analyzing the influence of wind power plant access on the medium-term and long-term voltage stability of the system, and calculating the change condition of reactive power reserve of the system before and after the wind power plant access.

(c) System frequency stability analysis after wind power plant access

And calculating the frequency change condition of the isolated network system under the condition that the wind power plant access system is in isolated network operation in the near region and certain power is unbalanced, and frequency stabilizing measures.

(d) Small interference stability analysis of system after wind power plant access

And calculating main low-frequency oscillation modes of the system, and comparing the change conditions of the damping ratio of each main oscillation mode before and after the wind power plant is accessed.

(3) Mutual influence analysis of wind power development scale and grid-connected near-zone grid structure

The part needs to be developed by combining the characteristics of accessing to a near-zone power grid and comprises the following steps: analyzing the wind power output capacity, analyzing the isolated network operation capacity, analyzing the mutual influence between the wind power supply and the near-region conventional power supply and the like.

2. The overall analysis technical framework of the coordination planning of the wind power supply and the power grid under the large-scale wind power access is shown in the attached figure 5.

Wind power supply and power grid coordinated planning analysis algorithm flow

Based on a wind power supply simulation principle with content 1 suitable for network source coordination planning analysis and an overall analysis technology framework of wind power supply and power grid coordination planning with content 2 under large-scale wind power access, an analysis algorithm flow of wind power supply and power grid coordination planning is designed and provided. The details are shown in fig. 6.

It should be noted that the summary and the detailed description of the invention are intended to demonstrate the practical application of the technical solutions provided by the present invention, and should not be construed as limiting the scope of the present invention. Various modifications, equivalent alterations, and improvements will occur to those skilled in the art and are intended to be within the spirit and scope of the invention. Such changes and modifications are intended to be included within the scope of the appended claims.

Claims (15)

1. A planning simulation method for evaluating the adaptability of a wind power grid-connected scale and a power grid network frame adjusts a planning scheme for coordinating a wind power supply and a power grid, and is characterized by comprising the following steps:

(1) carrying out steady state analysis on the planning scheme, and adjusting the power grid planning scheme according to a steady state analysis result;

(2) dynamically analyzing the planning scheme, and adjusting the power grid planning scheme according to the dynamic analysis result;

(3) analyzing the mutual influence between the wind power scale and the grid-connected near-zone grid structure, and adjusting the power grid planning scheme according to the mutual influence analysis result;

(4) correcting and checking the power grid planning scheme to obtain a corrected wind power supply and power grid coordination planning scheme;

the steady state analysis, the dynamic analysis and the mutual influence analysis of the wind power scale and the grid-connected near-zone grid structure respectively call a wind power supply simulation method suitable for grid source coordination planning analysis;

the wind power supply simulation method suitable for network source coordination planning analysis comprises the following steps: reasonable equivalence processing of static characteristics of the wind power supply, accurate simulation of dynamic characteristics of the wind power supply and difference processing of actual characteristics of the wind power supply;

the accurate simulation of the dynamic characteristics of the wind power supply comprises the following steps: the wind generating set mostly adopts an asynchronous generator, and physical quantities needing equivalence are researched through a wind generator single machine mathematical model when equivalence of a wind power plant cluster is researched; equivalent key parameters of the wind power plant can be obtained by an asynchronous generator set mathematical model and a generator rotor motion model as follows:

T_Jequivalent inertia time constant:

similar to an asynchronous motor, the inertia time constant equivalence method of the rotor of the asynchronous generator weights according to the capacity to obtain:

wherein S is_jAnd T_jRespectively refer to the capacity and inertia time constant, S, of the jth asynchronous motor_MIs the sum of the capacities of the asynchronous motors, T_JThe inertia time constant of the equivalent asynchronous machine is obtained, and n is the total number of the asynchronous machines;

s equivalent initial slip:

firstly, connecting the equivalent circuits of the asynchronous machines in parallel, and obtaining the equivalent resistance R of the two machines by using a Thevenin equivalent method_MThe slip s of the equivalent generator in the initial state can be obtained_M；

$s_M=\frac{R_M{(\frac{R_1}{s_1}+\frac{R_2}{s_2})}^2+R_M{(X_{l1}+X_{l2})}^2}{\left(\frac{R_1}{s_1}\right)\[X_{l2}^2+{\left(\frac{R_2}{s_2}\right)}^2\]+\left(\frac{R_2}{s_2}\right)\[X_{l1}^2+{\left(\frac{R_1}{s_1}\right)}^2\]}$

Wherein R is₁And R₂Respectively representing the sum of the resistances of the stator and the rotor of two motors, X_l1And X_l2Respectively representing the sum of leakage reactance of stator and rotor of motor, s₁、s₂Respectively representing the initial running slip of the two motors, wherein each physical quantity unit is a per unit value;

x is equivalent synchronous reactance, X 'is equivalent transient reactance and T'₀Is the equivalent rotor winding time constant;

the three parameters can be calculated according to the following formula:

$\left\{\begin{array}{c}X=X_s+X_m\\ X^{\′}=X_s+X_r{X}_m/(X_r+X_m)\\ T_0^{\′}=(X_r+X_m)/\left(2{\mathrm{\πR}}_r\right)\end{array}\right.$

in the formula, R_sIs a stator resistor; r_rIs the rotor resistance; x_sIs a stator reactance; x_rIs the rotor reactance; x_mIs an excitation reactance.

2. The planning simulation method of claim 1, wherein the reasonable equivalence processing of the static characteristics of the wind power supply comprises: in a wind power plant, a wind turbine generator adopts unit wiring of 1 machine and 1 transformer, and the models of the transformers are the same; collecting the wind turbine generator connected to 1 collecting line at the high-voltage side of the transformer, and connecting the wind turbine generator to the low-voltage side of a main transformer station of a wind power plant through 1 collecting line; the active loss and the reactive loss of the current on the transformer are respectively as follows:

${\mathrm{\ΔP}}_i=\frac{P_i^2+Q_i^2}{U_{it}^2}{R}_i,{\mathrm{\ΔQ}}_i=\frac{P_i^2+Q_i^2}{U_{it}^2}{X}_i$

wherein, P_i、Q_iInjecting active power and reactive power into a transformer connected with the ith wind turbine generator set; u shape_it、R_i、X_iThe voltage, the equivalent resistance and the equivalent reactance of the transformer are respectively; delta P_i、ΔQ_iThe active loss and the reactive loss of the current on the transformer are respectively; therefore, the power injected into the current collecting circuit by the ith wind turbine generator set is as follows:

P'_i+jQ'_i＝(P_i-ΔP_i)+j(Q_i-ΔQ_i)

wherein, P'_i、Q'_iRespectively injecting active power and reactive power of a current collection circuit into the ith wind turbine generator set;

meanwhile, according to the voltage drop phasor diagram, the following can be obtained:wherein (a),Are respectively asAnd U_itAndandthe included angle between the phasors; AB represents the length of the AB segment; active power P 'at the outlet of the high-voltage side of the transformer of each wind turbine generator can be obtained according to the formula'_iAnd reactive power Q'_iAnd power factor

When a plurality of wind turbine generators are connected in parallel to the same current collecting line, the power factors are respectively set asThe total power output at the high-voltage side outlet of the transformer of the wind turbine generator is as follows:

wherein P is_i、Q_iThe total active power and the total reactive power P output from the high-voltage side outlet of the transformer of the wind turbine generator_n'、The active power of the nth wind turbine generator set and the included angle of the voltage and current phasor of the nth wind turbine generator set are respectively included, in the wind power plant, each wind turbine generator set can be equivalent to 1 wind turbine generator set by the above formula, and the capacity of the equivalent wind turbine generator set is equal to the sum of the capacities of each wind turbine generator; for the whole wind power plant, the wind power plant equivalent can be 1 wind power plant according to factors such as parameters of a wind power plant and a generator transformer, and the equivalent generator is taken as a PQ node during load flow calculation, so that the capacity S of the equivalent wind power plant is as follows:

$S_{\mathrm{\Σ}\mathrm{\Σ}}=\underset{i=1}{\overset{n}{\mathrm{\Σ}}}\underset{j=1}{\overset{m}{\mathrm{\Σ}}}{S}_{i,j}=\underset{i=1}{\overset{n}{\mathrm{\Σ}}}\underset{j=1}{\overset{m}{\mathrm{\Σ}}}{P}_{i,j}^{\′}+\underset{i=1}{\overset{n}{\mathrm{\Σ}}}\underset{j=1}{\overset{m}{\mathrm{\Σ}}}{Q}_{i,j}^{\′}$

in the formula, i and j represent the positions of the wind turbines in the wind power plant, and n and m respectively represent the number of fans on each current collecting line in the wind power plant and the number of the current collecting lines in the wind power plant;

during load flow calculation, current collecting lines inside a wind power plant are equivalent to 1 equivalent impedance according to the arrangement of wind turbine generators, wherein the current collecting lines inside the wind power plant are divided into two types, namely direct-buried cables and overhead lines; due to the fact that parameter difference between a cable line and an overhead line is large, equivalent values of the current collecting lines in the wind power plant are required to be carried out according to the types of the current collecting lines.

3. The planning simulation method according to claim 1, wherein the difference of the actual characteristics of the wind power supply is processed, and the time difference and the space difference are processed respectively.

4. The planning simulation method according to claim 3, wherein the temporal diversity processing comprises: determining an accumulative effect reduction function P of wind power plant wind resource characteristic correlation based on meteorological data w of the wind power plant according to the randomness of the output of the wind power plant, the dispersity of the distribution of the wind power plant and wind generating sets_WFPower output characteristic of f (w), where PWF represents the output power of the wind farm.

5. The planning simulation method according to claim 3, wherein the spatial diversity processing comprises: an equivalent model is used in static and dynamic simulation, all fans in a wind power plant are equivalent to a single equivalent unit, and a detailed model of the wind power plant is established; in the modeling process of the wind power plant detailed model, all parameters use actual parameters of various devices of the wind power plant; if the situation that part of actual parameters are unknown exists, the most conservative situation in a reasonable range is considered;

the modeling of the wind power plant detailed model comprises the following steps: the wind power generation set comprises a wind power generation set, a box type transformer, a current collection circuit, a boosting transformer and an access system circuit.

6. The planning simulation method according to any one of claims 1 to 5, wherein in the step (1), the steady-state analysis invokes a wind power supply static characteristic reasonable equivalence process to analyze the influence of wind power on the power flow of the power grid and the static safety, and the influence of wind power integration on the reactive voltage characteristic of the power grid, respectively.

7. The planning simulation method according to any one of claims 1 to 5, wherein in the step (2), the dynamic analysis calls an accurate simulation of the dynamic characteristics of the wind power supply, and analyzes the transient stability of the system after the wind power access, the voltage stability of the system after the wind power access, the frequency stability of the system after the wind power access, and the small interference stability of the system after the wind power access.

8. The planning simulation method according to any one of claims 1 to 5, wherein in the step (3), the mutual influence analysis calls a wind power supply dynamic characteristic accurate simulation to analyze the wind power sending capacity, the isolated network operation capacity and the mutual influence of the wind power supply and a near-region conventional power supply respectively.

9. The planning simulation method according to any one of claims 1 to 5, wherein in the step (4), the difference processing of the actual characteristics of the wind power supply is invoked to correct and verify the power grid planning scheme.

10. The planning simulation method of claim 6, wherein the influence of the wind power on the grid power flow and the static safety analysis comprise: the influence of wind power integration on the planning power flow of a power grid and the load rate of power transmission and transformation equipment is analyzed, and whether the thermal stability limit constraint of the power transmission and transformation equipment is met under the condition of no fault disconnection is analyzed.

11. The planning simulation method according to claim 6, wherein the analysis of the influence of the wind power integration on the reactive voltage characteristics of the power grid comprises: under the condition that a reactive power compensation device is not configured in the wind power plant, reactive power compensation scheme suggestions including inductive compensation under light load flow and capacitive compensation under heavy load flow are provided for voltage fluctuation of the access point and each substation in the nearby area caused by active power output change through calculation.

12. The planning simulation method of claim 7, wherein the post-wind farm access system transient stability analysis comprises: after the wind power plant is accessed, N-1 fault checking and serious fault checking are carried out on the access system near area, and a constant power factor operation mode, a constant voltage operation mode and the condition of the existence of low voltage ride through capability of a fan are respectively researched.

13. The planning simulation method according to claim 7, wherein the analysis of the system voltage stability after the wind farm is connected comprises calculating the dropping and recovery conditions of the bus voltage of each transformer substation after the wind farm is connected and the short-circuit fault occurs in the near area of the connected system; voltage stability of the system in case of severe failure; analyzing the influence of wind power plant access on the medium-term and long-term voltage stability of the system, and calculating the change condition of reactive power reserve of the system before and after the wind power plant access.

14. The planning simulation method according to claim 7, wherein the analyzing of the frequency stability of the system after the wind farm is accessed comprises: and calculating the frequency change condition of the isolated network system under the condition that the wind power plant access system is in isolated network operation in the near region and certain power is unbalanced, and frequency stabilizing measures.

15. The planning simulation method according to claim 7, wherein the analyzing of the stability of the system small interference after the wind farm is accessed comprises: and calculating the main low-frequency oscillation mode of the system, and comparing the damping ratio change conditions of the main oscillation modes before and after the wind power plant is accessed.