CN103337855A - Electrical network operation risk assessment method of wind electricity large-scale tripping - Google Patents

Abstract

The invention provides an electrical network operation risk assessment method of a wind electricity large-scale tripping. The method comprises the following steps of: simulation of a wind electricity large-scale tripping accident caused by a fault, a risk assessment of electrical network transient stability after disturbance, the risk assessment of system frequency stability after the disturbance, and the risk assessment of voltage stability after the disturbance. The method of the invention quantizes the risk of the wind electricity large-scale tripping from each aspect of the electrical network operation, so that the effects of preventing the wind electricity tripping and improving the electrical network safety are achieved.

Description

A kind of operation of power networks methods of risk assessment of wind-powered electricity generation scale off-grid

Technical field

The invention belongs to field of power, be specifically related to a kind of operation of power networks methods of risk assessment of wind-powered electricity generation scale off-grid.

Background technology

In order to realize the grand energy strategy of low-carbon (LC), environmental protection, green and sustainable development, China greatly developed regenerative resource in recent years, put into effect a series of standard and policy at regenerative resource, given strong support in national aspect, regenerative resource has obtained tremendous development.Especially wind-powered electricity generation, China has built in a plurality of million kilowatt wind-powered electricity generation base and has finished and inserted operation of power networks, construction is also just progressively carried out in eight ten million multikilowatt wind-powered electricity generation bases of planning, the development mode of China's wind-powered electricity generation is different from abroad, be " carry at a distance, dissolve on a large scale based on extensive access, the high pressure concentrated ", " inserting on-site elimination with extensive dispersion " is the pattern of assisting.

In recent years, the newly-increased scale of wind-powered electricity generation and speed are in first place, the world, the wind-powered electricity generation fast development has brought enormous benefits to society, but this wherein also exists risk: the one, and the wind-electricity integration standard is progressively implemented from national aspect, the wind-powered electricity generation that is not incorporated into the power networks according to standard is is also rectified and improved, but on the whole, wind-powered electricity generation unit regulation and control level is very different, as the low-voltage relatively be concerned about, high voltage ride-through capability etc., this just causes the phenomenon of grid disturbance wind-powered electricity generation off-grid to occur; The 2nd, the core technology of wind-powered electricity generation, as current transformer and relevant with current transformer etc. meritorious, idle control technology etc. not on top of, introduction of foreign technology has increased wind-powered electricity generation unit manufacturing cost, in order to save cost, when putting into operation, meritorious, the idle control of wind-powered electricity generation unit and lowly wear, height is worn etc., and function is often had a greatly reduced quality, simultaneously, with technical specification such as the supporting dynamic reactive compensation device of wind energy turbine set and realize that also there is certain gap etc. in function etc. with expection, to sum up, be difficult to behind the wind-electricity integration provide support for the dynamic security of electrical network preferably; The 3rd, because the wind-powered electricity generation development speed is too fast, exist electric field construction quality and an interior electric component configuration, design to have hidden danger such as unreasonable unavoidably, as the construction quality of main element cable in the wind field, protection for feed line and blower fan protection adjust and cooperate inharmonious etc., these are cause or the inducement of wind-powered electricity generation scale off-grid often; The 4th, the exploitation of China wind-powered electricity generation be based on extensive concentrate be incorporated into the power networks, high pressure is remote carries; be different from external development mode; scale field group's effect and all have particularity with the coupling of big electrical network; easily cause the chain off-grid of scale; all do not have experience can supply to use for reference from planning aspect, operation aspect, the wind-powered electricity generation off-grid strengthens the impact risk of electricity net safety stable.

Because the comprehensive function of the above-mentioned multiple hidden danger that the wind-powered electricity generation fast development brings, cause the risk that the extensive off-grid of blower fan takes place in the wind-powered electricity generation base to increase, and wind-powered electricity generation scale, centrality is more outstanding, the probability that chain off-grid takes place is also just more big, simultaneously with the grid reciprocation, the impact that brings to power network safety operation, influence is just more big, as 2.24 of wind-powered electricity generation base, Jiuquan generation in 2011,4.3,4.17,4.25 etc. serial large-scale wind power off-grid accident, accident causes 598 respectively, 400,677,1278 typhoon machine off-grids, off-grid wind-powered electricity generation capacity is respectively 840MW, 568MW, 975MW and 1535MW; Wind-powered electricity generation unit scale off-grid also takes place in wind-powered electricity generation base, Zhangbei County on April 17 in 2011, and off-grid platform number is that 644, capacity are 854MW, and the extensive off-grid accident of the wind-powered electricity generation of above-mentioned generation has all been brought greater impact to electrical network, has had influence on power network safety operation.The safe and stable operation of electrical network for prevention and control wind-powered electricity generation off-grid better and after guaranteeing off-grid; be necessary to propose a kind of operation of power networks methods of risk assessment for wind-powered electricity generation scale off-grid; the impact and the influence that come the quantitative evaluation off-grid to bring to electrical network from a plurality of sides of power network safety operation, and then prevention and control in addition targetedly.

Because China's wind-powered electricity generation development speed is too fast, and wind-powered electricity generation planning construction and Electric Power Network Planning, blower fan manufacturing, the standard that is incorporated into the power networks, construction quality etc. is inharmonious, concentrate the access high pressure to send outside at a distance under the scene of dissolving at large-scale wind power, very easily take place because the extensive off-grid of wind-powered electricity generation unit that disturbance causes, and then impact big power grid security.

Summary of the invention

In order to overcome above-mentioned the deficiencies in the prior art; the invention provides a kind of operation of power networks methods of risk assessment of wind-powered electricity generation scale off-grid; quantize the risk that the extensive off-grid of wind-powered electricity generation brings from each side of operation of power networks, and then play the effect of prevention and control wind-powered electricity generation off-grid, lifting power grid security.

In order to realize the foregoing invention purpose, the present invention takes following technical scheme:

A kind of operation of power networks methods of risk assessment of wind-powered electricity generation scale off-grid is provided, said method comprising the steps of:

Step 1: simulated failure causes the accident scene of wind-powered electricity generation scale off-grid;

Step 2: carry out the risk assessment of electrical network transient stability after the disturbance;

Step 3: carry out the risk assessment of system frequency stability after the disturbance;

Step 4: carry out the risk assessment of voltage stability after the disturbance.

Described step 1 may further comprise the steps:

Step 1-1: set up the static trend computation model of big electrical network and big electrical network transient stability computation model based on big electrical network PSD-BPA emulation platform;

Step 1-2: the simulation electric network fault causes the disturbance of wind-powered electricity generation scale off-grid.

Among the described step 1-1, the static trend computation model of big electrical network comprises generator model, load model, transformer model and circuit model; Big electrical network transient stability computation model comprises the generator transient Model based on the generator dynamic element, and described generator transient Model comprises twin shaft model, excitation model, power system stabilizer, PSS model, speed regulator model and prime mover model.

Described step 1-2 may further comprise the steps:

1) the electric component place of simulation wind energy turbine set, big electrical network causes the fault of wind-powered electricity generation off-grid, comprises symmetrical short-circuit fault, unsymmetrical short-circuit fault and disconnection fault;

2) relaying protection regular event in back takes place in simulated failure, excision fault element, the scene of generation wind-powered electricity generation off-grid after postponing blink;

3) simulate the scene that the wind-powered electricity generation unit is counted the scale off-grid according to designated capabilities, appointment platform.

In the described step 2, the electrical network transient stability under the dual impact of the off-grid of wind-powered electricity generation scale subsequently takes place to reach in assessment electrical network main road fault, and its instability forms comprises merit angle step-out aperiodic and vibration step-out.

System's equivalence is one machine infinity bus system, if establish original machine power P _m, generator internal e.m.f. E and Infinite bus system voltage U ' be constant, ignore line resistance and distributed capacitance, total apparent reactance of system is X _Σ

Stand little interference and near the linearisation working point then has the increment equation for Infinite bus system:

$\left\{\begin{array}{c}M\frac{\mathrm{d\Δ\ω}}{\mathrm{dt}}=\mathrm{\Δ}{P}_m-\mathrm{\Δ}{P}_e\\ \frac{\mathrm{d\Δ\δ}}{\mathrm{dt}}=\mathrm{\Δ\ω}\\ P_e=\frac{E{U}^{\′}}{X_{\mathrm{\Σ}}}\cos {\mathrm{\δ}}_0=\mathrm{K\Δ\δ}\end{array}---\left(1\right)\right.$

Wherein, δ is the generator amature angle; δ ₀Generator amature angle for steady operation point place; P _mBe original machine power; P _eBe generator machine end electromagnetic power; M is inertia time constant; ω is generator speed; K is the synchronising torque coefficient, and

Can get the system features equation by formula (1) is

Mp ²+K=0 （2）

Have for equation (2):

1) if K〉0, then characteristic root is

ω _nThe natural frequency of oscillation of the relative Infinite bus system of generator amature during for system's undamped, when taking into account mechanical damping, system stability;

2) as if K＜0, then

Characteristic root has a positive real root, and system's instability, its instability forms are the aperiodicity step-out;

3) if K=0 then is zero repeated root, system is positioned at critical condition, and real system does not allow to move in critical condition;

In the described step 3, behind the wind-powered electricity generation unit scale off-grid, system power generation vacancy, vacancy power is redistributed at each generator according to rigidity factor coefficient and the moment of inertia of each generator, generator electromagnetic power changes, because inertia time constant is bigger, the mechanical output of unit prime mover remains unchanged in this time yardstick, the imbalance of generator electromagnetic power and mechanical output makes generator speed change, when generator speed changes and enters into the mean speed of system, the generator governing system begins to respond rotation speed change, and further change exerting oneself of unit by its characteristic, take into account the merit of load simultaneously and regulate effect frequently, last comprehensive power frequency characteristic decision systems frequency by system;

Power shortage behind the wind-powered electricity generation scale off-grid causes system frequency to descend, by the stability of following two index evaluation system frequencies:

1) low-limit frequency is fallen amplitude greater than 49Hz in the dynamic transition process, to avoid electrical network low frequency load shedding equipment action loss load;

2) steady frequency after the dynamic transition is greater than 49.5Hz and less than 50.5Hz.

In the described step 4, the voltage of establishing power supply point is U ₁0 ° of ∠ is through impedance Z _lThe circuit of ∠ θ is the load power supply of P+jQ to power, and at this moment the voltage of load side is U ₂∠ δ ₂The output power equation is expressed as:

$\left\{\begin{array}{c}P=\frac{U_1{U}_2}{Z_l}\cos ({\mathrm{\&delta;}}_2+\mathrm{\&theta;})-\frac{{\mathrm{<figure-callout\; id="2"\; label="U"\; filenames="HDA00003168281800041.png"\; state="\{\{state\}\}">U</figure-callout>}}_2^2}{Z_l}\cos \mathrm{\&theta;}\\ Q=\frac{U_1{U}_2}{Z_l}\sin ({\mathrm{\&delta;}}_2+\mathrm{\&theta;})-\frac{{\mathrm{<figure-callout\; id="2"\; label="U"\; filenames="HDA00003168281800041.png"\; state="\{\{state\}\}">U</figure-callout>}}_2^2}{Z_l}\sin \mathrm{\&theta;}\end{array}\right.---\left(3\right)$

Cancellation δ ₂, can get:

${\mathrm{<figure-callout\; id="2"\; label="U"\; filenames="HDA00003168281800041.png"\; state="\{\{state\}\}">U</figure-callout>}}_2^4+{\mathrm{<figure-callout\; id="2"\; label="U"\; filenames="HDA00003168281800041.png"\; state="\{\{state\}\}">U</figure-callout>}}_2^2(2{\mathrm{PZ}}_l\cos \mathrm{\&theta;}+2{\mathrm{QZ}}_l\sin \mathrm{\&theta;}-{\mathrm{<figure-callout\; id="1"\; label="U"\; filenames="HDA00003168281800022.png,HDA00003168281800051.png"\; state="\{\{state\}\}">U</figure-callout>}}_1^2)+({\mathrm{<figure-callout\; id="2"\; label="P"\; filenames="HDA00003168281800041.png"\; state="\{\{state\}\}">P</figure-callout>}}^2+Q^2){\mathrm{<figure-callout\; id="2"\; label="Z\; l"\; filenames="HDA00003168281800041.png"\; state="\{\{state\}\}">Z</figure-callout>}}_l^{}=0---\left(4\right)$

If the voltage of given power supply point and the voltage of load side, then formula (4) be illustrated on the P-Q coordinate system with

Be the center of circle, with Circle for radius; Wherein P represents vertical axis, and Q represents trunnion axis, with the power of load absorption be on the occasion of;

If the voltage of load side is parameter, then by formula (4) bunch circle, each circle is illustrated in the relation of P and Q under the condition of voltage of given load side; The common tangent line representative of bunch circle allows the limit border of the operational mode that exists, is the operational mode that impossible exist at the upside of this tangent line, and the downside of tangent line is the zone that can move;

The active power that causes the near region ultra-high-tension power transmission line to be sent when the quick off-grid of wind-powered electricity generation unit sharply reduces, therefore reduced fast by the meritorious circuit reactive loss that brings of transmission, and it is idle approximate constant to charge, then the idle of near region ultra-high-tension power transmission line injected system will increase behind the off-grid, and wind-powered electricity generation unit off-grid capacity is more big, the amplitude of the idle increase of injected system is also more big, near region, wind-powered electricity generation base substation bus bar voltage magnitude is soaring fast, the maximum that easily surpasses apparatus insulated requirement, the risk of generation insulation breakdown.

Compared with prior art, beneficial effect of the present invention is:

1. practical, prevention and control wind-powered electricity generation off-grid, lifting power grid security are played better effect;

2. the scene of simulated failure after wind TV university scale off-grid preferably, simultaneously, outstanding more disturbance is to the influence of big power network safety operation;

Therefore 3. because the present invention is based on the relevant simulation that big electrical network PSD-BPA emulation platform carries out, it is comparatively accurate to the influence of electrical network to simulate behind the wind-powered electricity generation off-grid;

4. from the risk of the extensive off-grid of each operation side assessment wind-powered electricity generation such as electrical network merit angle, frequency and voltage, assessment is comparatively comprehensive, quantification.

Description of drawings

Fig. 1 is the operation of power networks methods of risk assessment flow chart of wind-powered electricity generation scale off-grid;

Fig. 2 is one machine infinity bus system figure in the embodiment of the invention;

Fig. 3 is the infinitely great generator's power and angle characteristic of unit schematic diagram in the embodiment of the invention;

Fig. 4 is electric power system schematic diagram in the embodiment of the invention;

Fig. 5 is circuit element power and voltage relationship schematic diagram in the embodiment of the invention;

Fig. 6 is that in the embodiment of the invention be incorporated into the power networks and send schematic diagram in wind-powered electricity generation base in Jiuquan;

Fig. 7 be in the embodiment of the invention under the target mode year big load method Jiuquan wind-powered electricity generation insert northwest net main cross sections Power Exchange schematic diagram;

Fig. 8 is Jiuquan～merit angle, circuit N-1 fault power plant, west of a river schematic diagram under the target year big load method in the embodiment of the invention;

Hami～Dunhuang line power schematic diagram when Fig. 9 is Jiuquan under the target year big load method in the embodiment of the invention～west of a river circuit N-1 fault;

Figure 10 is wind-powered electricity generation off-grid 3300MW system frequency change curve under the target year big load method in the embodiment of the invention;

Figure 11 is in the embodiment of the invention under the target year big load method, blower fan off-grid 530MW, each 750kV substation bus bar change in voltage curve synoptic diagram of west of a river passage;

Figure 12 is in the embodiment of the invention under the target year big load method, blower fan off-grid 956MW, passage 750kV Dunhuang, west of a river power station busbar voltage dynamic change schematic diagram.

Embodiment

Below in conjunction with accompanying drawing the present invention is described in further detail.

Because China's wind-powered electricity generation development speed is too fast, and wind-powered electricity generation planning construction and Electric Power Network Planning, blower fan manufacturing, the standard that is incorporated into the power networks, construction quality etc. is inharmonious, concentrate the access high pressure to send outside at a distance under the scene of dissolving at large-scale wind power, very easily take place because the extensive off-grid of wind-powered electricity generation unit that disturbance causes, and then impact big power grid security.The present invention is directed to this problem, propose a kind of operation of power networks methods of risk assessment for wind-powered electricity generation scale off-grid, quantize the risk that the extensive off-grid of wind-powered electricity generation brings from each side of operation of power networks, and then play prevention and control wind-powered electricity generation off-grid, promote the effect of power grid security.Before proposing the present invention, in conjunction with the evolutionary process of the actual extensive off-grid accident of wind-powered electricity generation that takes place and the demand of security and stability analysis of large power grid, 3 reasonably hypothesis preconditions are proposed:

1) because evolutionary process such as the cause of the extensive off-grid of wind-powered electricity generation, development and wind-powered electricity generation unit initial condition, wind-powered electricity generation unit dynamic characteristic etc. are closely related, it is different that each typhoon group of motors of wind energy turbine set is subjected to wind speed etc. to influence initial condition; And wind-powered electricity generation unit dynamic characteristic one is relevant with initial condition, and initial condition is indefinite, and dynamically performance also respectively has difference; The 2nd, relevant with the machine unit characteristic of wind-powered electricity generation unit producer, physical model etc., the wind field blower fan is generally by a plurality of manufacturer production, and the characteristic of each producer's unit differs, and therefore, it is very difficult reappearing this process;

2) since the present invention stress be wind-powered electricity generation scale off-grid to the final influence of big electricity net safety stable, therefore more concerned big electricity net safety stable problem, the detailed simulation of the chain off-grid sequential of blower fan is not as emphasis;

3) because the importance of big electricity net safety stable; so in big electrical network actual operating arrangement and control strategy formulation, all take relatively conservative thinking; namely leave certain margin of safety; therefore; the present invention simulates wind-powered electricity generation scale off-grid scene and takes serious partially mode: in general; be after electric network fault takes place through of short duration time delay, the quick off-grid of wind-powered electricity generation unit is to specifying platform number and designated capabilities, the big power grid security of assessment under this scene.Be assumed to be the operation of power networks methods of risk assessment that precondition proposes wind-powered electricity generation scale off-grid provided by the invention with this, as Fig. 1, this method may further comprise the steps:

Step 1: simulated failure causes the accident scene of wind-powered electricity generation scale off-grid;

Step 2: carry out the risk assessment of electrical network transient stability after the disturbance;

Step 3: carry out the risk assessment of system frequency stability after the disturbance;

Step 4: carry out the risk assessment of voltage stability after the disturbance.

Described step 1 may further comprise the steps:

Step 1-1: set up the static trend computation model of big electrical network and big electrical network transient stability computation model based on big electrical network PSD-BPA emulation platform;

Step 1-2: the simulation electric network fault causes the disturbance of wind-powered electricity generation scale off-grid.

Among the described step 1-1, the static trend computation model of big electrical network comprises generator model, load model, transformer model and circuit model; Big electrical network transient stability computation model comprises the generator transient Model based on the generator dynamic element, described generator transient Model comprise twin shaft (d, q) model, excitation model, power system stabilizer, PSS model (power system stabilizer, PSS), speed regulator model and prime mover model.

Described step 1-2 may further comprise the steps:

1) the electric component place of simulation wind energy turbine set, big electrical network causes the fault of wind-powered electricity generation off-grid, comprises symmetrical short-circuit fault, unsymmetrical short-circuit fault and disconnection fault;

2) relaying protection regular event in back takes place in simulated failure, excision fault element, the scene of generation wind-powered electricity generation off-grid after postponing blink;

3) simulate the scene that the wind-powered electricity generation unit is counted the scale off-grid according to designated capabilities, appointment platform.

In the described step 2; owing to concentrate the large-scale wind power base of inserting mostly away from load center; wind-powered electricity generation is sent outside at a distance by ultra-high-tension power transmission line; near region, wind-powered electricity generation base capacity of short circuit is less relatively, a little less than the grid structure relative thin; anti-transient state disturbance ability a little less than; need the electrical network transient stability under the main road fault generation of emphasis assessment electrical network and the dual impact of the off-grid of wind-powered electricity generation scale subsequently, its instability forms comprises merit angle step-out aperiodic and vibration step-out.

As Fig. 2 and Fig. 3, system's equivalence is one machine infinity bus system, if establish original machine power P _m, generator internal e.m.f. E and Infinite bus system voltage U ' be constant, ignore line resistance and distributed capacitance, total apparent reactance of system is X _Σ

Stand little interference and near the linearisation working point then has the increment equation for Infinite bus system:

$\left\{\begin{array}{c}M\frac{\mathrm{d\&Delta;\&omega;}}{\mathrm{dt}}=\mathrm{\&Delta;}{P}_m-\mathrm{\&Delta;}{P}_e\\ \frac{\mathrm{d\&Delta;\&delta;}}{\mathrm{dt}}=\mathrm{\&Delta;\&omega;}\\ P_e=\frac{\mathrm{EU}\&prime;}{X_{\mathrm{\&Sigma;}}}\cos {\mathrm{\&delta;}}_0=\mathrm{K\&Delta;\&delta;}\end{array}\right.---\left(1\right)$

Wherein, δ is the generator amature angle; δ ₀Generator amature angle for steady operation point place; P _mBe original machine power; P _eBe generator machine end electromagnetic power; M is inertia time constant; ω is generator speed; K is the synchronising torque coefficient, and

Can get the system features equation by formula (1) is

Mp ²+K=0 （2）

Have for equation (2):

1) if K〉0, then characteristic root is

ω _nThe natural frequency of oscillation of the relative Infinite bus system of generator amature during for system's undamped, when taking into account mechanical damping, system stability;

2) as if K＜0, then

Characteristic root has a positive real root, and system's instability, its instability forms are the aperiodicity step-out;

3) if K=0 then is zero repeated root, system is positioned at critical condition, and real system does not allow to move in critical condition;

Can release as followsly to this according to load angle characteristic as physical solution, if systematic steady state operates in the A point, have at that point: P _m=P _e, A point generator amature angle δ _A＜90 °, and have

Then make rotor angle that fractional increments Δ δ as can be known be arranged when there is small sample perturbations in system〉0 the time, by

Generator machine end electromagnetic power P as can be known _eFractional increments Δ P will be arranged _e0, and P _m=0, thus there is equation of rotor motion as can be known, this Δ P _eTo cause that rotor slows down, thereby Δ δ is reduced, and be tending towards returning former operating condition, so after the disturbance disappearance, δ through a transient process, will get back in system under damping action _AOperation; So system is statically stable in the operation of A point.

But if system's initial launch is at B point, P at that point _m=P _e, B point generator amature angle δ _B＜90 °, and have

Then working as system has small sample perturbations, when making rotor angle that fractional increments be arranged, by

As can be known, generator machine end electromagnetic power P _eFractional increments Δ P will be arranged _e＜0, and P _m=0, thus there is equation of rotor motion as can be known, this Δ P _eTo cause that rotor accelerates, thereby Δ δ is further increased, generator is tending towards step-out, is unsettled so system operates in the B point.

When system operates in the C point, this moment C point generator amature angle δ _C90 °,

System is in critical condition.This moment generator machine end electromagnetic power P _eReach maximum, if increase mechanical output again, then because Generator amature angle δ will speed up and is tending towards infinitely great, system's step-out.

To electric power system microvariations stability analysis, the system when supposing normal the operation is at t=t ₀Constantly be interfered, the running status of system is transferred to Δ x (t in this moment by 0 ₀).This value is disturbs the free-moving initial condition of back system that disappears.Because interference is enough little, Δ x (t ₀) be in the enough little neighborhood of Δ x=0.Therefore can study the small interference stability problem of non-linear electric power system according to the Liapunov linearized theory.The Liapunov linearization technique is relevant with the local stability of non linear system, says intuitively, should have similar characteristic to its linearisation when non linear system is moved among a small circle.

State equation and the power flow equation of each dynamic element of electric power system are expressed as respectively:

$\left\{\begin{array}{c}{x}_i=f_d(x_i,U)\\ i_i=g_d(x_i,U)\end{array}\right.$

Wherein, x _iBe the state variable of dynamic element, U is the terminal voltage of dynamic element, i _iFor injecting the electric current of network, f _d(x _i, U) be the function of state of dynamic element; g _d(x _i, U) be the trend function of dynamic element;

The linearisation state equation of each dynamic element can be expressed as:

$\left\{\begin{array}{c}\mathrm{\&Delta;}{x}_i=A_i\mathrm{\&Delta;}{x}_i+B_i\mathrm{\&Delta;U}\\ \mathrm{\&Delta;}{i}_i=C_i\mathrm{\&Delta;}{x}_i+Y_i\mathrm{\&Delta;U}\end{array}\right.$

Wherein, A _i, B _i, C _iAnd Y _iBe respectively equation coefficient; B _iAnd Y _iIn the value, except corresponding to the dynamic element terminal voltage or be used for controlling the element non-zero of far-end voltage, other all are zero.Network is to represent with the admittance battle array, Δ i=Y _NΔ U, Δ i be dynamic element to the injection current vector of network, except to being connected to the bus of dynamic element, other all are zero, Y _NBe node admittance matrix;

Can be got by following formula: Δ x _i=(A _i+ B _i(Y _N+ Y _i) ^-1C _i) Δ x=A Δ x.

Order | λ I-A|=0, this formula is called the characteristic equation of matrix A, and wherein I is unit matrix.Satisfying | the value of the λ of λ I-A|=0 is called the characteristic value of A matrix, stablizes first theorem according to Liapunov, and the stable among a small circle of linear system is that root by the linearisation characteristic equation determines, is specially:

L) if the system after the linearisation is progressive stable, namely be negative when the real part of all characteristic values of matrix A, so Shi Ji non linear system is stablized in that balance point is progressive;

2) if the system's instability after the linearisation namely has a real part at least for just when all characteristic values of matrix A, so Shi Ji non linear system is unsettled at balance point;

3) if the system's neutrality after the linearisation, namely no real part is positive in all characteristic values of matrix A, is zero characteristic value but have a real part at least, to the non linear system of reality in the balance point neutrality.For electric power system, this situation also is classified as system's instability.

As through assessment, system keeps transient stability after the disturbance, and then the interior electrical network of Zhi Hou a period of time yardstick experiences the dynamic transition of another kind of form, at this moment more concerned wind-powered electricity generation unit off-grid to the influence of system response and busbar voltage characteristic.

In the described step 3, behind the wind-powered electricity generation unit scale off-grid, system power generation vacancy, vacancy power is redistributed at each generator according to rigidity factor coefficient and the moment of inertia of each generator, generator electromagnetic power changes, because inertia time constant is bigger, the mechanical output of unit prime mover remains unchanged in this time yardstick, the imbalance of generator electromagnetic power and mechanical output makes generator speed change, when generator speed changes and enters into the mean speed of system, the generator governing system begins to respond rotation speed change, and further change exerting oneself of unit by its characteristic, take into account the merit of load simultaneously and regulate effect frequently, last comprehensive power frequency characteristic decision systems frequency by system;

Under the electric power system normal operation, in case load disturbance occurs, suppose that the idle component of load disturbance amount is very little, the node voltage amplitude can be used as invariable.The real component of load disturbance amount will make the voltage phase angle of disturbance point change, and by the change of this phase angle the load disturbance amount will be delivered to all generating sets in the system.

The system of setting up departments has m platform generator, and load disturbance amount Δ P has taken place at node k place _l, under action of small disturbance, the electromagnetic power linearisation to the output of i platform generator has

$\mathrm{\&Delta;}{P}_{\mathrm{ei}}\underset{j\&NotEqual;i,k}{\overset{m}{\underset{j=1}{\mathrm{\&Sigma;}}}}\left(E_i^{\&prime;}{E}_j^{\&prime;}{B}_{\mathrm{ij}}\cos {\mathrm{\&delta;}}_{\mathrm{ij}0}\right)\mathrm{\&Delta;}{\mathrm{\&delta;}}_{\mathrm{ij}}+\left(E_i^{\&prime;}{V}_k{B}_{\mathrm{ik}}\cos {\mathrm{\&delta;}}_{\mathrm{ik}0}\right)\mathrm{\&Delta;}{\mathrm{\&delta;}}_{\mathrm{ik}}=\underset{j\&NotEqual;i,k}{\overset{m}{\underset{j=1}{\mathrm{\&Sigma;}}}}{P}_{\mathrm{sij}}\mathrm{\&Delta;}{\mathrm{\&delta;}}_{\mathrm{ij}}+P_{\mathrm{sik}}\mathrm{\&Delta;}{\mathrm{\&delta;}}_{\mathrm{ik}}$

Wherein: P _EiIt is the electromagnetic power of i platform generator output; δ _Ij0Phase difference for i, j two node voltages before the disturbance; δ _Ik0Phase difference for i, k two node voltages before the disturbance;

With Be respectively the constant potential after i, the reactance of j platform generator transient state; V _kVoltage for disturbance point; B _IjBe i, k two internodal transfer susceptance; B _IkBe i, k two internodal transfer susceptance; P _SijAnd P _SikBe the rigidity factor coefficient.

In disturbance take place moment, the disturbance quantity of load is distributed between generating set by the rigidity factor coefficient of each generating set, and this process is finished rapidly.Finishing of this process is not subjected to any restriction of pool simultaneously, i.e. the transfer of load disturbance amount is not only carried out between generator in the one's respective area of disturbance, also passes through interconnection simultaneously and shifts to adjacent domain.Because this moment, any Region control mode also had little time to play a role, the load disturbance that takes place in a certain district system is inevitable to reflect at interconnection.

After generating set has born disturbance component, flip-flop the output of original electromagnetic power, and in this moment, because the relation of machinery inertial, the impossible flip-flop of mechanical output still is original numerical value, at this moment causes the imbalance of power, must cause the change of generating set rotating speed, and following relation is arranged:

$\frac{J_i}{{\mathrm{\&omega;}}_0}\frac{\mathrm{d\&Delta;}{\mathrm{\&omega;}}_i}{\mathrm{dt}}=-\mathrm{\&Delta;}{P}_{\mathrm{ei}}\left(t\right)$

Wherein, J _iIt is the moment of inertia of i platform generator; ω _iIt is the rotating speed of i platform generator; ω ₀Be reference rotation speed; P _Ei(t) be the electromagnetic power that i platform generator t exports constantly.

During this period, each generating set will be played a leading role by moment of inertia, begin to change rotating speed.Because the difference of difference, each generating set rigidity factor coefficient and the moment of inertia of load disturbance point, each generating set will be by the related parameter that has separately, and is accompanied by effect each other, changes the distribution with system load flow of exerting oneself of unit.Because the effect of the rigidity factor coefficient of generating set makes all generating sets progress into the mean speed of system in change.When generating set entered mean speed, the variation of generating set electromagnetic power was decided by its coefficient of rotary inertia.The load disturbance amount is at first distributed between unit by generating set rigidity factor coefficient, then transfers to by the turbine generator inertia coefficient and distributing.In this course, along with the generating set change in rotational speed, governing system is experienced signal, and further changes exerting oneself of unit by its characteristic, at last according to the frequency of comprehensive governor control characteristics decision systems and the exerting oneself of each generating set of system.

Power shortage behind the wind-powered electricity generation scale off-grid causes system frequency to descend, by the stability of following two index evaluation system frequencies:

1) low-limit frequency is fallen amplitude greater than 49Hz in the dynamic transition process, to avoid electrical network low frequency load shedding equipment action loss load;

2) steady frequency after the dynamic transition is greater than 49.5Hz and less than 50.5Hz.

In the described step 4, near region, wind-powered electricity generation base substation bus bar voltage and the idle distribution of near region electric network element are closely related, wherein, the idle of circuit element injected system is the idle algebraical sum of circuit reactive loss and line mutual-ground capacitor charging, mostly large-scale wind electricity base electric power all be by supertension line in addition more the circuit of voltage levels send outside at a distance, because the line voltage distribution grade is higher, circuit is longer, and it is all bigger that the charging of direct-to-ground capacitance is idle.

Fig. 4 is the simple power system schematic diagram, and the voltage of establishing power supply point is U ₁0 ° of ∠ is through impedance Z _lThe circuit of ∠ θ is the load power supply of P+jQ to power, and at this moment the voltage of load side is U ₂∠ δ ₂The output power equation is expressed as:

$\left\{\begin{array}{c}P=\frac{U_1{U}_2}{Z_l}\cos ({\mathrm{\&delta;}}_2+\mathrm{\&theta;})-\frac{{\mathrm{<figure-callout\; id="2"\; label="U"\; filenames="HDA00003168281800041.png"\; state="\{\{state\}\}">U</figure-callout>}}_2^2}{Z_l}\cos \mathrm{\&theta;}\\ Q=\frac{U_1{U}_2}{Z_l}\sin ({\mathrm{\&delta;}}_2+\mathrm{\&theta;})-\frac{{\mathrm{<figure-callout\; id="2"\; label="U"\; filenames="HDA00003168281800041.png"\; state="\{\{state\}\}">U</figure-callout>}}_2^2}{Z_l}\sin \mathrm{\&theta;}\end{array}\right.---\left(3\right)$

Cancellation δ ₂, can get:

${\mathrm{<figure-callout\; id="2"\; label="U"\; filenames="HDA00003168281800041.png"\; state="\{\{state\}\}">U</figure-callout>}}_2^4+{\mathrm{<figure-callout\; id="2"\; label="U"\; filenames="HDA00003168281800041.png"\; state="\{\{state\}\}">U</figure-callout>}}_2^2(2{\mathrm{PZ}}_l\cos \mathrm{\&theta;}+2{\mathrm{QZ}}_l\sin \mathrm{\&theta;}-{\mathrm{<figure-callout\; id="1"\; label="U"\; filenames="HDA00003168281800022.png,HDA00003168281800051.png"\; state="\{\{state\}\}">U</figure-callout>}}_1^2)+({\mathrm{<figure-callout\; id="2"\; label="P"\; filenames="HDA00003168281800041.png"\; state="\{\{state\}\}">P</figure-callout>}}^2+Q^2){\mathrm{<figure-callout\; id="2"\; label="Z\; l"\; filenames="HDA00003168281800041.png"\; state="\{\{state\}\}">Z</figure-callout>}}_l^{}=0---\left(4\right)$

If the voltage of given power supply point and the voltage of load side, then formula (4) be illustrated on the P-Q coordinate system with

Be the center of circle, with

Circle for radius; Wherein P represents vertical axis, and Q represents trunnion axis, with the power of load absorption be on the occasion of;

If the voltage of load side is parameter, then by formula (4) bunch circle, as Fig. 5, each circle is illustrated in the relation of P and Q under the condition of voltage of given load side; The common tangent line representative of bunch circle allows the limit border of the operational mode that exists, is the operational mode that impossible exist at the upside of this tangent line, and the downside of tangent line is the zone that can move;

The active power that causes the near region ultra-high-tension power transmission line to be sent when the quick off-grid of wind-powered electricity generation unit sharply reduces, therefore reduced fast by the meritorious circuit reactive loss that brings of transmission, and it is idle approximate constant to charge, then the idle of near region ultra-high-tension power transmission line injected system will increase behind the off-grid, and wind-powered electricity generation unit off-grid capacity is more big, the amplitude of the idle increase of injected system is also more big, near region, wind-powered electricity generation base substation bus bar voltage magnitude is soaring fast, the maximum that easily surpasses apparatus insulated requirement, the risk of generation insulation breakdown.

Embodiment

With Northwest Grid target mode year be example, based on the PSD-BPA emulation platform, the operation risk of wind-powered electricity generation base, analysis and evaluation Jiuquan extensive blower fan off-grid Northwest Grid.

As Fig. 6, wind-powered electricity generation base, Jiuquan comprises main force's wind energy turbine set that Gan Qiaowan, Gan Qiaobei, Gan Qiaodong, Gan Gandong, Gan Ganbei, Gan Ganxi etc. are incorporated into the power networks by the 330kV circuit, goal in research year Jiuquan wind-powered electricity generation base installed capacity among the present invention is about 5,000,000 kilowatts, each wind energy turbine set by the 0.69/35/330kV electric pressure be incorporated into the power networks, on send power and send through Dunhuang-Jiuquan-west of a river-Wusheng 750kV passway for transmitting electricity (west of a river passway for transmitting electricity) of nearly thousand kilometers.

(1) wind-powered electricity generation off-grid transient stability operation risk assessment;

Fig. 7 is wind-powered electricity generation base, target mode year Northwest Grid Jiuquan actual power power, each province, northwest discontinuity surface transmission power situation schematic diagram, and wind-powered electricity generation actual exerting oneself in Jiuquan is about 2900MW, and it is 1000MW that Gansu, northwest section power is sent in Xinjiang.

Jiuquan-permanent N-1 short trouble of west of a river double loop generation three-phase when west of a river passway for transmitting electricity, the wind-powered electricity generation unit is whole off-grids after system breaks down, system's active power vacancy is bigger, system frequency descends, the meritorious raising of exerting oneself of the whole network unit under the speed regulator effect, the Xinjiang electrical network northwestwards electrical power of sending of electrical network increases, and stabilization of power grids level in Xinjiang is descended, and causes major network merit angle, the relative northwest of Xinjiang unit unstability.By emulation as can be known, under this target year big load method, when wind-powered electricity generation base, Jiuquan wind-powered electricity generation off-grid scale reaches about 2900MW, transient state merit angle unstability risk takes place easily.The result of calculation tabulation is as shown in table 1.Simulation result such as Fig. 8 and shown in Figure 9.

Table 1

(2) wind-powered electricity generation off-grid frequency operation risk assessment;

The system response of the spinning reserve capacity of system after to extensive jumping machine has great influence, according to operating standard, should leave the spinning reserve capacity of 2%-5% when electrical network normally moves.The present invention considers relative serious situation, consider that simultaneously northwest-Xinjiang electrical network might separate network operation after fault, then Northwest Grid (not containing Xinjiang) spinning reserve should surpass the maximum unit capacity of separate unit in the net under the big load method of target year, be 1000MW, so in this research mode, Northwest Grid (not containing Xinjiang) leaves spinning reserve 1120MW, is about 2.37% of maximum generation capacity, adds up to spinning reserve to be about 2.36% of networking back, Xinjiang, northwest system;

Wind-powered electricity generation base, Jiuquan actual power that sends of wind-powered electricity generation unit is about 3300MW, the whole instantaneous off-grids of wind-powered electricity generation base, Jiuquan 3300MW online wind-powered electricity generation after the consideration disturbance, and system frequency changes as shown in figure 10.By simulation result as can be known: when wind-powered electricity generation off-grid scale reached 3300MW, system frequency deviation was near 1Hz, and system frequency is near UFLS operating value 49Hz.

Therefore, under target year big load method, when disturbance causes that Jiuquan wind-powered electricity generation off-grid scale surpasses 3300MW, system's easy occurrence frequency unstability risk.

(3) wind-powered electricity generation off-grid voltage operation risk assessment;

Under target year big load method, Jiuquan wind-powered electricity generation 2900MW that exerts oneself, northwest 1000MW is sent in Xinjiang.750kV passage each main substation bus bar voltage levvl in the west of a river is specifically as shown in table 2 under the mode of basis, and unit is kV in the table.From table as can be known, voltage levvl all in the reasonable scope.

Table 2

Hami 750kV	Dunhuang 750/330kV	Jiuquan 750/330kV	West of a river 750/330kV	Wusheng 750/330kV
					774.2	771.2/356.8	766.1/361.2	760.5/350.6	763.5/348.3
Bridge west wind electricity and website	Yumen 330kV	The Jiayu Pass 330kV	Zhangye 330kV	Liangzhou 330kV
					357.1	361.4	360.4	356.2	348.5

Because certain disturbance takes place wind energy turbine set, when causing Jiuquan blower fan (mainly being area, Guazhou County) off-grid 530MW, the dynamic change of the main 750kV substation bus bar of west of a river passway for transmitting electricity voltage as shown in figure 11.

Jiuquan blower fan (mainly being area, Guazhou County) off-grid capacity continues to strengthen, and when the off-grid fan capacity reached 956MW, the 750kV Dunhuang busbar voltage change curve of west of a river passage as shown in figure 12.

The soaring schematic diagram of voltage of 530MW, 956MW behind the comparison blower fan off-grid, can find out the increasing along with wind-powered electricity generation off-grid capacity, the soaring amplitude of voltage strengthens, behind blower fan off-grid capacity 956MW, the Dunhuang busbar voltage has surpassed perunit value 1, and namely the famous value of voltage is greater than safe voltage 800kV.

Therefore, under target year big load method, when disturbance caused that Jiuquan wind-powered electricity generation off-grid scale surpasses 956MW, the soaring risk of voltage easily took place in wind-electricity integration near region busbar voltage, had influence on the insulation safety of grid equipment element.

Should be noted that at last: above embodiment is only in order to illustrate that technical scheme of the present invention is not intended to limit, although with reference to above-described embodiment the present invention is had been described in detail, those of ordinary skill in the field are to be understood that: still can make amendment or be equal to replacement the specific embodiment of the present invention, and do not break away from any modification of spirit and scope of the invention or be equal to replacement, it all should be encompassed in the middle of the claim scope of the present invention.

Claims (8)

1. the operation of power networks methods of risk assessment of a wind-powered electricity generation scale off-grid is characterized in that: said method comprising the steps of:

Step 1: simulated failure causes the accident scene of wind-powered electricity generation scale off-grid;

Step 2: carry out the risk assessment of electrical network transient stability after the disturbance;

Step 3: carry out the risk assessment of system frequency stability after the disturbance;

Step 4: carry out the risk assessment of voltage stability after the disturbance.

2. the operation of power networks methods of risk assessment of wind-powered electricity generation scale off-grid according to claim 1, it is characterized in that: described step 1 may further comprise the steps:

Step 1-1: set up the static trend computation model of big electrical network and big electrical network transient stability computation model based on big electrical network PSD-BPA emulation platform;

Step 1-2: the simulation electric network fault causes the disturbance of wind-powered electricity generation scale off-grid.

3. the operation of power networks methods of risk assessment of wind-powered electricity generation scale off-grid according to claim 2 is characterized in that: among the described step 1-1, the static trend computation model of big electrical network comprises generator model, load model, transformer model and circuit model; Big electrical network transient stability computation model comprises the generator transient Model based on the generator dynamic element, and described generator transient Model comprises twin shaft model, excitation model, power system stabilizer, PSS model, speed regulator model and prime mover model.

4. the operation of power networks methods of risk assessment of wind-powered electricity generation scale off-grid according to claim 2, it is characterized in that: described step 1-2 may further comprise the steps:

1) the electric component place of simulation wind energy turbine set, big electrical network causes the fault of wind-powered electricity generation off-grid, comprises symmetrical short-circuit fault, unsymmetrical short-circuit fault and disconnection fault;

2) relaying protection regular event in back takes place in simulated failure, excision fault element, the scene of generation wind-powered electricity generation off-grid after postponing blink;

3) simulate the scene that the wind-powered electricity generation unit is counted the scale off-grid according to designated capabilities, appointment platform.

5. the operation of power networks methods of risk assessment of wind-powered electricity generation scale off-grid according to claim 1; it is characterized in that: in the described step 2; electrical network transient stability under the dual impact of the off-grid of wind-powered electricity generation scale subsequently takes place to reach in assessment electrical network main road fault, and its instability forms comprises merit angle step-out aperiodic and vibration step-out.

6. the operation of power networks methods of risk assessment of wind-powered electricity generation scale off-grid according to claim 5 is characterized in that: system's equivalence is one machine infinity bus system, if establish original machine power P _m, generator internal e.m.f. E and Infinite bus system voltage U ' be constant, ignore line resistance and distributed capacitance, total apparent reactance of system is X _Σ

Stand little interference and near the linearisation working point then has the increment equation for Infinite bus system:

Wherein, δ is the generator amature angle; δ ₀Generator amature angle for steady operation point place; P _mBe original machine power; P _eBe generator machine end electromagnetic power; M is inertia time constant; ω is generator speed; K is the synchronising torque coefficient, and

Can get the system features equation by formula (1) is

Mp ²+K=0 （2）

Have for equation (2):

1) if K〉0, then characteristic root is

ω _nThe natural frequency of oscillation of the relative Infinite bus system of generator amature during for system's undamped, when taking into account mechanical damping, system stability;

2) as if K＜0, then

Characteristic root has a positive real root, and system's instability, its instability forms are the aperiodicity step-out;

3) if K=0 then is zero repeated root, system is positioned at critical condition, and real system does not allow to move in critical condition.

7. the operation of power networks methods of risk assessment of wind-powered electricity generation scale off-grid according to claim 1, it is characterized in that: in the described step 3, behind the wind-powered electricity generation unit scale off-grid, system power generation vacancy, vacancy power is redistributed at each generator according to rigidity factor coefficient and the moment of inertia of each generator, generator electromagnetic power changes, because inertia time constant is bigger, the mechanical output of unit prime mover remains unchanged in this time yardstick, the imbalance of generator electromagnetic power and mechanical output makes generator speed change, when generator speed changes and enters into the mean speed of system, the generator governing system begins to respond rotation speed change, and further change exerting oneself of unit by its characteristic, take into account the merit of load simultaneously and regulate effect frequently, last comprehensive power frequency characteristic decision systems frequency by system;

Power shortage behind the wind-powered electricity generation scale off-grid causes system frequency to descend, by the stability of following two index evaluation system frequencies:

1) low-limit frequency is fallen amplitude greater than 49Hz in the dynamic transition process, to avoid electrical network low frequency load shedding equipment action loss load;

2) steady frequency after the dynamic transition is greater than 49.5Hz and less than 50.5Hz.

8. the operation of power networks methods of risk assessment of wind-powered electricity generation scale off-grid according to claim 1, it is characterized in that: in the described step 4, the voltage of establishing power supply point is U ₁0 ° of ∠ is through impedance Z _lThe circuit of ∠ θ is the load power supply of P+jQ to power, and at this moment the voltage of load side is U ₂∠ δ ₂The output power equation is expressed as:

Cancellation δ ₂, can get:

If the voltage of given power supply point and the voltage of load side, then formula (4) be illustrated on the P-Q coordinate system with

Be the center of circle, with

Circle for radius; Wherein P represents vertical axis, and Q represents trunnion axis, with the power of load absorption be on the occasion of;

If the voltage of load side is parameter, then by formula (4) bunch circle, each circle is illustrated in the relation of P and Q under the condition of voltage of given load side; The common tangent line representative of bunch circle allows the limit border of the operational mode that exists, is the operational mode that impossible exist at the upside of this tangent line, and the downside of tangent line is the zone that can move;

The active power that causes the near region ultra-high-tension power transmission line to be sent when the quick off-grid of wind-powered electricity generation unit sharply reduces, therefore reduced fast by the meritorious circuit reactive loss that brings of transmission, and it is idle approximate constant to charge, then the idle of near region ultra-high-tension power transmission line injected system will increase behind the off-grid, and wind-powered electricity generation unit off-grid capacity is more big, the amplitude of the idle increase of injected system is also more big, near region, wind-powered electricity generation base substation bus bar voltage magnitude is soaring fast, the maximum that easily surpasses apparatus insulated requirement, the risk of generation insulation breakdown.

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