CN101895130A - Solution method of local boundary of injection space voltage stability region having wind power station - Google Patents

Abstract

The invention belongs to the technical field of electric systems, providing a solution method of a local boundary of an injection space voltage stability region (IVSR) having a wind power station for analysis and on-line safe monitoring of power grid voltage stability under the condition that a wind speed is difficult to be correctly forecasted. The method comprises the following steps: firstly, using a trend track and double-layer scheduling model to obtain a modulation unit tightly linked with the wind power station for balancing the fluctuation of the wind power station output power caused by the variation of the wind speed; then, obtaining key nodes of a generator for effectively reducing dimension of the IVSR by using model analysis; and at last, segmenting the regions of possible wind speed and the wind power station output power and calculating, and acquiring the local boundary of the IVSR at the corresponding wind speed through directed perturbation. The invention can rapidly obtain the local boundary of the IVSRat different wind speeds, be used for the on-line voltage stable monitoring of the power system having the wind power station, and has good engineering application prospect.

Description

The solution method of local boundary of injection space voltage stability region that contains wind energy turbine set

Technical field

Belong to technical field of power systems, relate to a kind of static voltage stability territory, injection space (IVSR) solution method of local boundary that contains wind energy turbine set.

Background technology

Wind-powered electricity generation is the most important renewable energy power generation form in the world today, obtains fast development in recent years, and wind-powered electricity generation installed capacity proportion in electrical network is increasing year by year.But output of wind electric field has tangible intermittence and randomness, in the electrical network active power of output, also often from the electrical network absorbing reactive power, therefore can bring to the voltage stability of electrical network to have a strong impact on ^[1]

Existing certain methods research wind-powered electricity generation is introduced the influence to line voltage stability: based on the analytical method of conventional P V curve, can only provide specify operating point down or under the special parameter change direction voltage of system stablize information, the integral body that is difficult to provide system voltage stability is estimated ^[2-4], consider that simultaneously the short-term wind speed is difficult to accurately predicting, cause output of wind electric field to be difficult to accurate grasp, make many of the analytical methods of PV curve be used for the research of programme; Probability analysis method ^[5,6], the computational process complexity can't realize in-service monitoring, and probabilistic method is based on Principle of Statistics simultaneously, and its conclusion often is difficult to instruct the safety on line monitoring.

Carry out on-line monitoring, the operations staff needs that more the global stability of electric power system is had a full appreciation.When we only consider the static voltage stability constraint, whole stable operating points of electric power system will constitute injection static voltage stability territory, space (IVSR) in the injecting power space ^[7,8], then constitute cut set power space voltage stability domain (CVSR) in the cut set power space ^[9,10], they all can be for the monitor staff provides the overall situation indication of system voltage stability and is used to instruct the safety on line monitoring, and therefore, the research of voltage stability domain receives increasing concern.But existing voltage stability domain computational methods still can't be considered the influence that output of wind electric field changes, therefore, and the voltage stability domain computational methods of the wind energy turbine set the considered influence that research is practical are great for electric power system safety on line meaning of monitoring.

When the conventional electric power system exceeded the power delivery limit of electric power networks at workload demand, often the heavy load point by receiving-end system began to take place voltage unstability or collapse.But insert electrical network (as receiving-end system) when the large-scale wind electricity field, may change the original trend transmission mode of system; In addition, consider wind energy turbine set, often will absorb idle in a large number from system when system sends active power.There is a strong correlation and voltage stability and system are idle, makes the access of large-scale wind electricity field in various degree influence be arranged line voltage stability.

Voltage stability domain provides a kind of instrument with application prospect for the monitoring of electric power system on-Line Voltage stability ^[7-10]The static voltage stability territory of containing wind energy turbine set is the set that is made of the stable operating point of all voltages, for ease of describing, uses S _GL=S _GYS _LExpression injecting power vector, wherein, S _G=(P _GcYQ _Gc) Y (P _GwYQ _Gw) represent the injecting power vector of conventional electric generators and wind energy turbine set correspondence, S respectively _L=P _LYQ _LExpression load injecting power vector.Work as S _GLAfter given, can be by the running status x of the unique definite system of following equation:

f(x，S _GL)＝0 (1)

g(x，S _GL)≤0

Wherein: f () is the system load flow equation, and g () is system's operation constraint equation.When x also satisfied formula (2) simultaneously, the title system was that voltage is stable; If x is when also satisfying formula (3) simultaneously, then the title system is in voltage and stablizes critical condition.

det(f _x)≠0 (2)

det(f _x)＝0 (3)

In the formula: f _xJacobian matrix for power flow equation.

Further, use X ^sThe set of whole steady operational status of formula (1) and formula (2) is satisfied in expression simultaneously, uses X ^cWhole set of stablizing critical condition of formula (1) and formula (3) are satisfied in expression simultaneously.Then the voltage stability domain (IVSR) and the boundary definition thereof in power injection space are:

Ω _IVSR＝{S _GL|x∈X ^s，f(x，S _GL)＝0，g(x，S _GL)≤0} (4)

$\∂{\mathrm{\Ω}}_{\mathrm{IVSR}}=\left\{S_{\mathrm{GL}}\right|x\∈X^c,f(x,S_{\mathrm{GL}})=0,g(x,S_{\mathrm{GL}})\≤0\}---\left(5\right)$

If the meritorious injection space of wind energy turbine set is as follows:

P _Gw＝[P _Gw，1，P _Gw，2，...P _Gw，s] (6)

Wherein, s is the wind-powered electricity generation number of fields in the system.After wind farm grid-connected, the random fluctuation meeting of wind speed causes P _GwVariation, and then can be to stable region Ω _IVSRAnd border

Exert an influence.Existing research has shown that the IVSR border is a high dimensional nonlinear curved surface, and existing IVSR method for solving ^[7-11], all need know the injecting power of each node in advance.But the wind speed of considering wind energy turbine set still is difficult to realize the short-term accurately predicting ^[12], cause the short term power output of wind energy turbine set definitely to predict, make and utilize conventional method to find the solution to contain the IVSR of wind energy turbine set to face the difficulty that is difficult to overcome, therefore must be improved.

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Summary of the invention

The objective of the invention is to overcome the above-mentioned deficiency of prior art, characteristics according to wind energy turbine set, propose a kind of IVSR local boundary that comprises wind energy turbine set and find the solution new method, be used for power system voltage stabilization analysis and the safety on line monitoring under can't the accurately predicting situation of wind speed and output of wind electric field.

For this reason, the present invention adopts following technical scheme:

A kind of solution method of local boundary of injection space voltage stability region that contains wind energy turbine set comprises following step:

The first step: determine that wind energy turbine set distributes, and the power variation compensation scheme of definite wind energy turbine set

(1) be defined as follows set:

System's wind energy turbine set set omega _WS={ G _{W, 1}, G _{W, 2}... G _{W, s}}

The direct tight association load aggregation of wind energy turbine set Ω _WL={ L _{W, 1}, L _{W, 2}... L _{W, t}}

With Ω _WLTight association power supply set omega _CS={ G _{C, 1}, G _{C, 2}... G _{C, u}}

The tight load aggregation Ω of the non-direct correlation of wind energy turbine set _OL={ L _{O, 1}, L _{O, 2}..., L _{O, v}}

The non-direct tight association power supply set omega of wind energy turbine set _OS={ G _{O, 1}, G _{O, 2}... G _{O, z},

The power output P if generator i gains merit _{G, i}The factor of sending with charge free to load k of sending with charge free is: k _Gi-Lk=P _Gi-Lk/ P _{G, i}, load k active power P _{L, k}The factor of drawing of drawing power from generator i is: k _Lk-Gi=P _Gi-Lk/ P _{L, k}, wherein: P _Gi-LkThe summation of the active power of transmitting between the k for generator i and load;

(2) determine that wind speed changes the compensation scheme that causes the adjustment of exerting oneself:

Determine by wind energy turbine set Ω earlier _WSExert oneself and adjust the Ω that causes _CSAnd Ω _OSThe variable quantity of power output: suppose load Ω _WL, Ω _OLRemain unchanged over a period to come, and Ω _WSIn w seat wind energy turbine set influenced by wind speed, it is exerted oneself and is changed to Δ P _Gw, Ω then _CSIn i platform generator be sent to Ω _WLThe power output adjustment amount of load is:

I ∈ Ω _CS, establish Ω _CSIn i platform generator supply with Ω _WLLoad proportion is γ _i, then supply with Ω _OLThe proportion of middle load is 1-γ _i, Ω for this reason _CSIn i platform generator for remedying Ω _WSIn wind energy turbine set power fluctuation and the power output adjustment amount made is: Δ P _Gi=Δ P ' _Gi/ γ _i, i ∈ Ω _CS, wherein, γ _iTry to achieve by following relation:

Obtain again because Ω _CSMiddle generator output adjustment causes Ω _OLIn k load power supply uneven and need Ω _OSIn j platform output of a generator adjustment amount be:

(3) determine output of wind electric field minor fluctuations compensation scheme at random

Set a fixed threshold, at Ω _CSThe middle γ that selects _iFollow the tracks of wind energy turbine set power fluctuation at random greater than the unit of this fixed threshold, be called automatic generation control AGC unit set omega _CSA, Ω then _CSAThe power adjustment of middle unit i is:

Ω _OLIn imbalance power will be by Ω _OSIn balancing machine compensate;

Second step: utilize modal analysis method to select the border of injecting static voltage stability territory, space IVSR is had the crucial generator node of decisive role, the meritorious injection vector of establishing crucial generator is: P _k=[P _{K, 1}, P _{K, 2}..., P _{K, m}];

The 3rd step: determine the wind speed of each wind energy turbine set, and then determine exerting oneself of each wind energy turbine set, the formation wind energy turbine set is transported to the active power P in the electrical network _GwAnd reactive power Q _GwVector;

The 4th step: to active power P _GwAnd reactive power Q _GwVector P _GwCarry out two-way perturbation

When perturbation quantity is Δ P, as follows to P _{Gw, i}(1≤i≤s) enforcement perturbation:

In the formula: subscript+and-represent forward perturbation and negative sense perturbation respectively, the micropower amount of unbalance that perturbation produced passes through Ω _CSAIn the output of wind electric field determined according to the first step of unit at random the minor fluctuations compensation scheme carry out balance, Q _GwDisturbance quantity by Q _GwAnd P _GwAnd the decision of the mapping relations between the wind speed, will be to P _GwAnd Q _GwThe operating point of system is designated as after the enforcement perturbation

With it is initial point, determines that system is at P _kInject the voltage in space and stablize critical point, count

In a manner described to P _GwAnd Q _GwIn all wind energy turbine set implement the forward perturbation successively, can get the critical point set of forward perturbation correspondence:

Equally, to P _GwAnd Q _GwAll wind energy turbine set are implemented the negative sense perturbation successively, can get the critical point set of negative sense perturbation correspondence:

The 5th step: the territory of finding the solution of bounding hyperplane is revised;

(1) utilizes

Obtain the approximate hyperplane on IVSR border by finding the solution m linear equation:

(2) utilize

Can get corresponding bounding hyperplane:

(3) adopt following formula to be revised:

In the formula: α _iRepresent the hyperplane coefficient, subscript "+" the expression utilization

Obtain the border coefficient of the approximate hyperplane on IVSR border by finding the solution m system of linear equations, subscript "-" expression utilizes

Can get the coefficient of corresponding bounding hyperplane,

The expression initial point Corresponding critical point, and obtain revised bounding hyperplane H _PFor:

The 6th step: judge whether to run into end condition, if then stop calculating, otherwise continue, end condition is that end condition is calculated in the artificial monitoring of setting of supervisory control system dispatcher, perhaps the end condition after all stable region local boundaries calculating are finished;

The 7th step: when wind farm wind velocity changed, at first the wind speed of determining according to the first step changed and causes that the compensation scheme of adjusting of exerting oneself compensates, and changes for the 3rd step then, continues.

The present invention has following technique effect: because wind energy turbine set short-term wind speed and exert oneself and be difficult to accurate prediction, the electric power system that causes containing wind energy turbine set is difficult to obtain safety on line necessary for monitoring monolithic stability and estimates.The local approximate boundaries acquisition methods of the IVSR based on perturbation that the present invention proposes can make full use of parallel computing, the IVSR border of the system that obtains quickly and accurately under various wind conditions, thus a kind of analysis tool of practicality is provided for on-line monitoring.

Description of drawings

Fig. 1 wind energy turbine set power back-off schematic diagram;

Fig. 2 wind energy turbine set energy conversion principle figure;

Fig. 3 Power Output for Wind Power Field and wind speed relation curve;

Fig. 4 New England 39 node systems and wind energy turbine set;

Fig. 5 local I VSR border result: what figure (a) expression parallel computer PCI finished is 100MW when wind energy turbine set G30 exerts oneself, the G34 75MW that exerts oneself, and wind energy turbine set G36 exerts oneself and fluctuates between the 100MW at 0MW, IVSR local boundary situation when step-length is 25MW, what figure (b) expression parallel computer PC2 finished is 100MW when wind energy turbine set G30 exerts oneself, the G34 50MW that exerts oneself, and wind energy turbine set G36 exerts oneself and fluctuates between the 100MW at 0MW, IVSR local boundary situation when step-length is 25MW, what figure (c) expression parallel computer PC3 finished is 100MW when wind energy turbine set G30 exerts oneself, the G34 25MW that exerts oneself, and wind energy turbine set G36 exerts oneself and fluctuates between the 100MW at 0MW, IVSR local boundary situation when step-length is 25MW, what figure (d) expression parallel computer PC4 finished is 100MW when wind energy turbine set G30 exerts oneself, the G34 0MW that exerts oneself, and wind energy turbine set G36 exerts oneself and fluctuates the IVSR local boundary situation when step-length is 25MW at 0MW between the 100MW.

The IVSR local boundary of Fig. 6 double-fed wind power generator correspondence;

The IVSR local boundary of Fig. 7 asynchronous wind driven generator correspondence;

Two kinds of wind field IVSR border result contrasts of Fig. 8.

Embodiment

Below to elaborating.

The first step: determine that wind energy turbine set distributes, and the power variation compensation scheme of definite wind energy turbine set

When grid was inserted in the large-scale wind power field, to the load power supply, the fluctuation of its power output then can be had a negative impact to the even running of system if do not compensate wind energy turbine set as main power supply.At double-deck scheduling scheme ^[13]On the basis, by the power flow tracing process ^[14]Obtain the unit that is closely related with wind energy turbine set, change the fluctuation of the wind-powered electricity generation power output that causes in order to the compensation wind speed.Principle is as shown in Figure 1:

Be defined as follows set for this reason:

Ω _WS＝{G _w，1，G _w，2，...G _w，s} (7)

Ω _WL＝{L _w，1，L _w，2，...L _w，t} (8)

Ω _CS＝{G _c，1，G _c，2，...G _c，u} (9)

Ω _OL＝{L _o，1，L _o，2，...，L _o，v} (10)

Ω _OS＝{G _o，1，G _o，2，...G _o，z} (11)

Parameter declaration:

Ω _WS: system's wind energy turbine set set;

Ω _WL: the direct tight association load aggregation of wind energy turbine set;

Ω _CS: with Ω _WLThe set of tight association power supply;

Ω _OL: the tight load aggregation of the non-direct correlation of wind energy turbine set;

Ω _OS: the non-direct tight association power supply set of wind energy turbine set

Respective nodes set in the corresponding diagram 1 respectively.As wind energy turbine set Ω _WSBecause causing, fluctuations in wind speed exerts oneself when changing, will inevitably be to Ω _WLLoad supply exert an influence, need to adjust and Ω this moment _WLClosely-related generator Ω _CSExert oneself balance in addition; And Ω _CSThe adjustment of exerting oneself also can have influence on Ω simultaneously _OLIn load supply, this part influence then needs by Ω _OSCompensated.Concrete scheme is as follows:

The power output P if generator i gains merit _{G, i}The factor of sending with charge free to load k of sending with charge free is:

k _Gi-Lk＝P _Gi-Lk/P _G，i (12)

Load k active power P _{L, k}The factor of drawing of drawing power from generator i is:

k _Lk-Gi＝P _Gi-Lk/P _L，k (13)

Wherein: P _Gi-LkThe summation of the active power of transmitting between the k for generator i and load can be passed through the power flow tracing algorithm ^[14]Obtain.

1) wind speed changes and causes the compensation scheme of exerting oneself and adjusting

At first determine by wind energy turbine set Ω _WSExert oneself and adjust the Ω that causes _CSAnd Ω _OSThe variable quantity of power output: suppose load Ω _WL, Ω _OLRemain unchanged over a period to come, and Ω _WSIn w seat wind energy turbine set influenced by wind speed, it is exerted oneself and is changed to Δ P _Gw(for just, being negative when reducing during increase), then Ω _CSIn i platform generator be sent to Ω _WLThe power output adjustment amount of load is:

$\mathrm{\Δ}{P}_{\mathrm{Gi}}^{\′}=\underset{k\∈{\mathrm{\Ω}}_{\mathrm{WL}}}{\mathrm{\Σ}}[(-\underset{w\∈{\mathrm{\Ω}}_{\mathrm{WS}}}{\mathrm{\Σ}}{k}_{\mathrm{Gw}-\mathrm{Lk}}\mathrm{\Δ}{P}_{\mathrm{Gw}})\×k_{\mathrm{Lk}-\mathrm{Gi}}],i\∈{\mathrm{\Ω}}_{\mathrm{CS}}---\left(14\right)$

Consider Ω _CSPower remove to supply with Ω _WLAlso to supply with Ω outward _OL, establish Ω _CSIn i platform generator supply with Ω _WLLoad proportion is γ _i, then supply with Ω _OLThe proportion of middle load is 1-γ _i, Ω for this reason _CSIn i platform generator for remedying Ω _WSIn wind energy turbine set power fluctuation and the power output adjustment amount made is:

ΔP _Gi＝ΔP′ _Gi/γ _i，i∈Ω _CS (15)

Wherein, γ _iTry to achieve by following relation:

${\mathrm{\γ}}_i=\underset{k\∈{\mathrm{\Ω}}_{\mathrm{WL}}}{\mathrm{\Σ}}{k}_{\mathrm{Gi}-\mathrm{Lk}},i\∈{\mathrm{\Ω}}_{\mathrm{CS}}---\left(16\right)$

In like manner can obtain because Ω _CSMiddle generator output adjustment causes Ω _OLIn k load power supply uneven and need Ω _OSIn j platform output of a generator adjustment amount be:

$\mathrm{\Δ}{P}_{\mathrm{Gj}}=\frac{\underset{k\∈{\mathrm{\Ω}}_{\mathrm{OL}}}{\mathrm{\Σ}}[(-\underset{i\∈{\mathrm{\Ω}}_{\mathrm{CS}}}{\mathrm{\Σ}}{k}_{\mathrm{Gi}-\mathrm{Lk}}\mathrm{\Δ}{P}_{\mathrm{Gi}})\×k_{\mathrm{Lk}-\mathrm{Gj}}]}{\underset{k\∈{\mathrm{\Ω}}_{\mathrm{OL}}}{\mathrm{\Σ}}{k}_{\mathrm{Gj}-\mathrm{Lk}}},j\∈{\mathrm{\Ω}}_{\mathrm{OS}}---\left(17\right)$

2) output of wind electric field minor fluctuations compensation scheme at random

For adapting to the minor fluctuations at random of wind energy turbine set, set a fixed threshold, at Ω _CSThe middle γ that selects _iFollow the tracks of wind energy turbine set power fluctuation at random greater than the unit of this fixed threshold, be called automatic generation control (AGC) unit set omega _CSA, Ω then _CSAThe power adjustment of middle unit i is:

$\mathrm{\Δ}{P}_{\mathrm{Gi}}=\underset{k\∈{\mathrm{\Ω}}_{\mathrm{WL}}}{\mathrm{\Σ}}[(-\underset{w\∈{\mathrm{\Ω}}_{\mathrm{WS}}}{\mathrm{\Σ}}{k}_{\mathrm{Gw}-\mathrm{Lk}}\mathrm{\Δ}{P}_{\mathrm{Gw}})\×\frac{k_{\mathrm{Lk}-\mathrm{Gi}}}{\underset{j\∈{\mathrm{\Ω}}_{\mathrm{CSA}}}{\mathrm{\Σ}}{k}_{\mathrm{Lk}-\mathrm{Gj}}}]---\left(18\right)$

Because when carrying out Perturbation Calculation, power fluctuation is not very big, so Ω _OLIn imbalance power will be by Ω _OSIn balancing machine compensate.

The windfarm system energy conversion principle as shown in Figure 2, wind energy turbine set is transported to the power P in the electrical network _Gw, Q _Gw(, being absorbed as negative from system) and axial fan hub wind speed v to send to just _WindBetween have following mapping relations:

P _Gw＝f _p(v _wind) (19a)

Q _Gw＝f _q(v _wind) (19b)

f _pAnd f _qRelevant with wind electric field blower type and control mode, Fig. 3 has provided meritorious power output of a kind of typical wind energy turbine set and wind speed relation curve ^[15], idle and wind speed relation are referring to document [15].Wherein, v _In, v _OutBe respectively the incision wind speed, the excision wind speed; v _rBe rated wind speed; P _rBe rated output power.When wind speed at [v _In, v _Out] between when changing, the meritorious output of wind energy turbine set will [0, P _r] between change, idlely will be determined by formula (19b).With wind speed interval [v _In, v _Out] being divided into the n section, every section siding-to-siding block length is d:

d＝(v _out-v _in)/n (20)

For current wind speed v _i(v _In＜v _i＜v _Out):

v _i＝v _in+d*i，0≤i≤n (21)

Wherein, v ₀=v _In, v _n=v _OutMeritorious and the idle P that exerts oneself of wind energy turbine set _Gw, Q _Gw(wherein, 0≤P _Gw≤ P _r) can determine by formula (19), and then can determine each wind energy turbine set injecting power vector P _GwAnd Q _Gw

The main influence of considering the wind energy turbine set of following two kinds of wind-powered electricity generation units formation to IVSR, adopt different trend computation models for this reason:

Asynchronous wind driven generator trend computation model

A kind of improved PQ model method that proposes according to document [16] is derived the relational expression of reactive power and active power, set end voltage by the simplification equivalent circuit of asynchronous wind driven generator.In each trend, to bring in constant renewal in reactive power value, and revise part Jacobian matrix element, this method amount of calculation is little, and computational speed is fast, and has higher accuracy.Because the machine end of asynchronous wind driven generator all is equiped with reactive power compensator, therefore, this paper further considers the machine end reactive power compensation amount Q of asynchronous blower fan _{Gw, comp}, this paper provides it as calculating initial condition, by the Q-V characteristic equation of asynchronous wind driven generator:

$Q_{\mathrm{Gw}}^{\&prime;}=f\left(V\right)=-{\mathrm{<figure-callout\; id="2"\; label="V"\; filenames="HDA0000024218440000031.png"\; state="\{\{state\}\}">V</figure-callout>}}^2/x_m+(-{\mathrm{<figure-callout\; id="2"\; label="V"\; filenames="HDA0000024218440000031.png"\; state="\{\{state\}\}">V</figure-callout>}}^2+\sqrt{V^4-4P_{\mathrm{Gw}}^2{x}^2})/2x---\left(22\right)$

Wherein: x _mBe excitation reactance, x is a stator and rotor leakage reactance sum, obtains asynchronous wind driven generator need be from the reactive power of system's absorption:

Q _Gw＝-Q′ _Gw+Q _Gw，comp (23)

Given wind speed and node voltage value are determined the active power P of wind-powered electricity generation machine by the wind speed power curve _Gw, according to following formula (22), (23) calculate Q _Gw, bring trend into as the PQ node and calculate, revise the reactive power that should recomputate generator behind the voltage at every turn.

Double-fed wind power generator trend computation model

Double fed asynchronous machine adopts frequency converter to regulate frequency, amplitude, phase place and the phase sequence of rotor winding exciting current, can carry out fine control to power output, can adopt the P-Q simplified model ^[17]Simulate its operation characteristic, promptly under the prerequisite of known active power, calculate the reactive power of this unit by the setting power factor.

Above-mentioned wind-powered electricity generation unit trend computation model has been arranged, for the wind energy turbine set that contains N typhoon power generator, ignoring its internal wiring loss and transformer loss, and suppose when all unit set end voltages all equal to wait to ask wind energy turbine set busbar voltage V that then meritorious the and reactive power of whole wind electric field can be calculated by following formula:

$P_{\mathrm{Gw}}=\underset{i=1}{\overset{N}{\mathrm{\&Sigma;}}}{P}_{\mathrm{Gw},i}---\left(24\right)$

$Q_{\mathrm{Gw}}=\underset{i=1}{\overset{N}{\mathrm{\&Sigma;}}}{Q}_{\mathrm{Gw},i}---\left(25\right)$

Because on the IVSR bounding theory is the Nonlinear Curved of a higher-dimension, it is very big directly to find the solution difficulty.And the perturbation solving method ^[11], can effectively address the above problem, provide the local boundary of the IVSR that is concerned about fast.To on [11] method basis, carry out finding the solution of IVSR border in conjunction with the characteristics that contain the wind energy turbine set electric power system.At first obtain the crucial generator set of system by model analysis for this reason ^[7], being used to carry out the visual dimensionality reduction displaying of IVSR, the meritorious injection vector of establishing crucial generator can be expressed as:

P _k＝[P _k，1，P _k，2，...，P _k，m] (26)

2) utilize modal analysis method to select the border of IVSR is had the crucial generator node of decisive role ^[7], to reach the purpose of visual dimensionality reduction.

In practical power systems, injecting power changes by different directions, and system will reach different critical operation points; In different critical points place, the crucial generator node of system may be different, when carrying out the safety on line monitoring, the load increasing mode is obtained by the short-term load forecasting result, the generator growth pattern is then determined by predefined operation plan, for the sake of simplicity, both all increase by the equal proportion mode in.

Crucial generator node:

Visual for the voltage stability domain local boundary because method for visualizing can only be expressed 3-D graphic information at most, for realizing the visual of territory, must be injected the space to the higher-dimension generator and carry out dimensionality reduction.Because the voltage unstability at first occurs in local weakness zone, involve the whole network then and cause system's large-area power-cuts, find that in conjunction with calculating each generator node is different to the influence of system voltage stability in the system simultaneously.Have some responsive generator nodes in system, the variation of its meritorious scheduling ratio is very big for the shape influence on stable region border, and these generators are referred to as: crucial generator node; Also have some non-sensitive generator nodes simultaneously, they are relatively very little to the edge effect in territory, even can ignore, and therefore can select the crucial generator node of system, just can reach the purpose of dimensionality reduction in the visualization process in territory.

Model analysis:

Model analysis provides rational foundation for the selection of crucial generator node, and the generator participation factors is the efficiency index of reflection generator node to system voltage stabilizing influence power.Generator k to the participation factors of mode i is:

P _FGki＝ΔQ _gki/ΔQ _g?maxi

Wherein: Δ Q _GkiThe idle variation of exerting oneself of the generator k that causes for the idle variation under the mode i; Constitute crucial generator node and be chosen in the generator that has big generator participation factors under the mode i corresponding under the minimal eigenvalue.

3) after the wind speed of each wind energy turbine set is all determined, utilize formula (19) to determine exerting oneself of each wind energy turbine set, form P _Gw, Q _GwVector;

4) to P _GwCarry out two-way perturbation, idle Q _GwDisturbance quantity determine by formula (19b).When perturbation quantity is Δ P, as follows to P _{Gw, i}(1≤i≤s) enforcement perturbation:

$P_{\mathrm{Gw},i}^{+}=P_{\mathrm{Gw},i}+\mathrm{\&Delta;P}---\left(27\right)$

$P_{\mathrm{Gw},i}^{-}=P_{\mathrm{Gw},i}-\mathrm{\&Delta;P}---\left(28\right)$

In the formula: subscript+and-represent forward perturbation and negative sense perturbation respectively.The micropower amount of unbalance that formula (27), (28) produce passes through Ω _CSAIn unit carry out balance, determine by formula (18); Ω _OLIn imbalance power by Ω _OSIn balancing machine compensate.Press (27) to P _GwAnd Q _GwThe operating point of system is designated as after the enforcement perturbation

With it is initial point, determines that system is at P _kInject the voltage in space and stablize critical point, count

In a manner described to P _GwAnd Q _GwIn all wind energy turbine set implement the forward perturbation successively, can get the critical point set of forward perturbation correspondence:

$X_{P_k}^{+}=\{x_{P_k,1}^{\&prime;+},x_{P_k,2}^{\&prime;+},...,x_{P_k,m}^{\&prime;+}\}---\left(29\right)$

Equally, press formula (28) to P _GwAnd Q _GwAll wind energy turbine set are implemented the negative sense perturbation successively, can get the critical point set of negative sense perturbation correspondence:

$X_{P_k}^{-}=\{x_{P_k,1}^{\&prime;-},x_{P_k,2}^{\&prime;-},...,x_{P_k,m}^{\&prime;-}\}---\left(30\right)$

5) territory of finding the solution of bounding hyperplane is revised;

At first utilize

Obtain the approximate hyperplane on IVSR border by finding the solution m system of linear equations:

$H_P^{+}:\underset{i=1}{\overset{m}{\mathrm{\&Sigma;}}}{\mathrm{\&alpha;}}_i^{+}{P}_{k,i}=1.0---\left(31\right)$

Equally, utilize

Can get corresponding bounding hyperplane:

$H_P^{-}:\underset{i=1}{\overset{m}{\mathrm{\&Sigma;}}}{\mathrm{\&alpha;}}_i^{-}{P}_{k,i}=1.0---\left(32\right)$

Because the existence of disturbance quantity, With

Usually do not comprise initial point Corresponding limit point

Adopt following method to be revised for this reason:

${\mathrm{\&alpha;}}_i=\frac{{\mathrm{\&alpha;}}_i^{\&prime;}}{K}---\left(33\right)$

${\mathrm{\&alpha;}}_i^{\&prime;}=\frac{{\mathrm{\&alpha;}}_i^{-}+{\mathrm{\&alpha;}}_i^{+}}{2}---\left(34\right)$

In the formula:

$K=\underset{i=1}{\overset{m}{\mathrm{\&Sigma;}}}{\mathrm{\&alpha;}}_i^{\&prime;}{P}_{\mathrm{Ck},i}^0---\left(35\right)$

$x_{P_k,i}^{\&prime;}=\{P_{\mathrm{Ck},1}^0,P_{\mathrm{Ck},2}^0,...,P_{\mathrm{Ck},m}^0\}---\left(36\right)$

Can get revised bounding hyperplane HP thus is:

$\underset{i=1}{\overset{m}{\mathrm{\&Sigma;}}}{\mathrm{\&alpha;}}_i{P}_{k,i}=1.0---\left(37\right)$

Above-mentioned correction is actual to be right

With

The coefficient on two planes is weighted on average, and with revised hyperplane H _PCarry out translation, to guarantee its mistake That is:

$\underset{i=1}{\overset{m}{\mathrm{\&Sigma;}}}{\mathrm{\&alpha;}}_i{P}_{\mathrm{Ck},i}^0=1.0---\left(38\right)$

6) judge whether to run into end condition,, otherwise continue if then stop calculating.

End condition is that end condition is calculated in the artificial monitoring of setting of supervisory control system dispatcher, perhaps the end condition after all static voltage stability territory local boundaries calculating are finished.

7) when wind farm wind velocity changes, at first by formula (15), (17) to P _GwVariation compensate, change step 3) then, continue.

Be that right algorithm is described further below:

Exerting oneself of wind energy turbine set has tangible intermittence and randomness, and the accurately predicting of short-term wind speed (the wind energy turbine set short-term is exerted oneself) is still global problem so far ^[12], cause the difficulty that contains the system's safety on line monitoring that inserts wind-powered electricity generation thus.Method provides a kind of feasible solution route for it:

Have s seat wind energy turbine set in the supposing the system, when carrying out the safety on line monitoring, although for arbitrary wind energy turbine set, its next wind speed constantly is difficult to accurately predicting, and the distribution of its wind speed can more accurately be grasped.The n five equilibrium is all carried out in the wind speed interval that each wind energy turbine set is possible, behind the independent assortment, co-exists in (n+1) ^sPossible situation.Make up for any one wind speed:

$v_{\mathrm{Gw}}^r=[v_{\mathrm{Gw},1}^r,v_{\mathrm{Gw},2}^r,...,v_{\mathrm{Gw},s}^r],r=\mathrm{1,2}...,{(n+1)}^s---\left(35\right)$

Can determine corresponding output of wind electric field by formula (19):

$P_{\mathrm{Gw}}^r=[P_{\mathrm{Gw},1}^r,P_{\mathrm{Gw},2}^r,...,P_{\mathrm{Gw},s}^r]---\left(36a\right)$

$Q_{\mathrm{Gw}}^r=[Q_{\mathrm{Gw},1}^r,Q_{\mathrm{Gw},2}^r,...,Q_{\mathrm{Gw},s}^r]---\left(36b\right)$

Further, can utilize the IVSR that calculates system's this moment:

$H_P^r=[{\mathrm{\&alpha;}}_1^r,{\mathrm{\&alpha;}}_2^r,...,{\mathrm{\&alpha;}}_m^r]---\left(37\right)$

After having considered every kind of wind speed combination, just can get next constantly all possible IVSR set:

$H_P=[{\mathrm{<figure-callout\; id="1"\; label="H\; P"\; filenames="HDA0000024218440000031.png"\; state="\{\{state\}\}">H</figure-callout>}}_P^{},{\mathrm{<figure-callout\; id="2"\; label="H\; P"\; filenames="HDA0000024218440000031.png"\; state="\{\{state\}\}">H</figure-callout>}}_P^{},...,H_P^{{(n+1)}^s}]---\left(38\right)$

Because (n+1) ^sKind of wind speed (or exerting oneself) combination is incoherent mutually, when carrying out the finding the solution of IVSR set, can utilize the example concurrent technique ^[18]Improve computational efficiency: with (n+1) ^sPlant mutual incoherent wind speed combination, hand over the parallel computation of M platform computer, obtain all possible IVSR of next moment of system then behind the summarized results.

When carrying out online application, when wind energy turbine set really wind cutting speed (or exerting oneself) known after, then can utilize the corresponding IVSR of wind speed (or exerting oneself) combination that closes on to carry out real-time security monitoring, satisfied the demand that voltage is stablized online security monitoring computational speed and precision.Solve output of wind electric field thus and can't determine the difficulty of the safety on line monitoring that forecasting institute causes.

Embodiment

With New England-39 node system is that example is carried out example and checking to institute's extracting method, if generator G39 is a balancing machine, the distribution situation of this system and contained wind energy turbine set is established G30, G34, G36 is the grid connected wind power field as shown in Figure 4, each wind energy turbine set rated output with initially exert oneself as shown in table 1.The wind-driven generator type takes in respectively by double-fed type and two kinds of situations of common asynchronous generator.

Table 1 wind energy turbine set state rated output power with initially exert oneself

Table1?Rated?and?initial?output?power?of?wind?farm

Table 2 wind energy turbine set compensation unit

Table2?The?compensation?generators?of?wind?farms

The tight offset supply of wind energy turbine set

G30 G37

G34 G33

G36 G35

Wind energy turbine set is the situation of double-fed wind power generator

Adopt the P-Q simplified model ^[17]Simulate the operation characteristic of double-fed wind power generator, this example is set double-fed type wind-powered electricity generation unit and electrical network and is asked and do not carry out reactive power exchange, i.e. power factor cos θ=1.0.Convenient for example, we constantly to the five equilibrium in forecasting wind speed interval, change next into to the meritorious forecast interval of exerting oneself of next moment wind energy turbine set five equilibrium in the example.If wind speed changes and causes that the interval step-length of wind energy turbine set power variation is d=25MW, and suppose to be between the possible fluctuation zone of next moment power of each electric field [0, P _{Gw, N}], P _{Gw, N}Specified meritorious exerting oneself for this wind energy turbine set.After then considering three wind energy turbine set, next is the P of this system constantly _GwAnd Q _GwCombining form possible in 100 will be arranged.Choose generator G32, G33, G35 as crucial generator node by model analysis, be used for visual presentation.Discuss for simplifying, only choose Ω for every wind energy turbine set _CSIn power supply that is closely related as the offset supply of corresponding wind energy turbine set, this power supply is obtained by power flow tracing ^[14], bear P _GwAnd Q _GwPower back-off when variation and perturbation, the formation situation of compensation unit is as shown in table 2.

For ease of describing, suppose through prediction, the wind speed of wind energy turbine set G30 remains unchanged constantly at next, be that meritorious the exerting oneself of wind energy turbine set G30 still is 100MW, and G34, the random fluctuation of exerting oneself of G36 wind energy turbine set, utilize joint 2 described methods, (PC1～PC4), bear the calculating of 20 IVSR local boundaries jointly, the result as shown in Figure 5 to adopt 4 parallel computers.Fig. 6 has provided 20 IVSR local boundary iso-surface patch results together.As seen, when wind energy turbine set G30 exert oneself definite, and G34, G36 exerts oneself when all changing by step-length d, the IVSR local boundary is arranged according to certain rules, approximate being on the three-dimension curved surface.When G30 meritorious exert oneself change after, for each possible exerting oneself of G30, all corresponding 20 system local I VSR borders.

Wind energy turbine set is common asynchronous generator

Adopt and improve the P-Q model ^[16]Simulate the operation characteristic of common asynchronous wind driven generator, and determine that with formula (22) (23) the idle of wind energy turbine set correspondence exert oneself.Compare for ease of the resulting IVSR local boundary of wind field that constitutes with the double-fed blower fan, still choose generator G32, G33, G35 is as crucial generator node and adopt identical assumed condition, can get corresponding part IVSR local boundary as shown in Figure 7.

For ease of relatively double-fed wind power generator and asynchronous wind driven generator constitute the influence of wind energy turbine set to the IVSR border, Fig. 6 and Fig. 7 result are plotted in same coordinate, the result is as shown in Figure 8: be not difficult to find out, for research system of institute, when G30, G34, G36 were the wind field that is made of asynchronous wind driven generator, the scope of its voltage stability domain was less than the situation that above-mentioned electric field is the double-fed unit.Hence one can see that, when double-fed wind power generator is incorporated into the power networks, the influence of system voltage stability is better than traditional asynchronous wind-powered electricity generation machine.

Can find following rule by above-mentioned analysis and calculating:

1) no matter for the wind energy turbine set that still constitutes by the double-fed type generator by common asynchronous generator, consider the IVSR border after its all possible wind speed (or exerting oneself) changes, generally can be similar to a high dimensional nonlinear curved surface.If utilize traditional IVSR border preparation method, can only produce a large amount of critical points at random, obtain by the Nonlinear Curved approximating method then, its amount of calculation is very huge, is difficult to use in the safety on line monitoring of instructing electric power system.And the perturbation method of utilizing the present invention to propose, calculate exert oneself IVSR local boundary under the combined situation of various wind-powered electricity generations: on the one hand, estimate its real border fast with part plan a plurality of and that the IVSR border is approximate tangent, under the prerequisite that guarantees computational accuracy, made full use of the wieldy convenience of hyperplane; On the other hand, algorithm has taken into full account the relative independentability that each output of wind electric field changes, and can promote computational efficiency by the example concurrent technique, to realize the safety on line monitoring of electric power system.

2) wind energy turbine set of double-fed wind power generator formation is better than the wind energy turbine set that common asynchronous generator constitutes to the influence of system's static electric voltage stability.

Claims (1)

1. solution method of local boundary of injection space voltage stability region that contains wind energy turbine set comprises following step:

The first step: determine that wind energy turbine set distributes, and the power variation compensation scheme of definite wind energy turbine set

(1) be defined as follows set:

System's wind energy turbine set set omega _WS={ G _{W, 1}, G _{W, 2}... G _{W, s}}

The direct tight association load aggregation of wind energy turbine set Ω _WL={ L _{W, 1}, L _{W, 2}... L _{W, t}}

With Ω _WLTight association power supply set omega _CS={ G _{C, 1}, G _{C, 2}... G _{C, u}}

The tight load aggregation Ω of the non-direct correlation of wind energy turbine set _OL={ L _{O, 1}, L _{O, 2}..., L _{O, v}}

The non-direct tight association power supply set omega of wind energy turbine set _OS={ G _{O, 1}, G _{O, 2}... G _{O, z},

The power output P if generator i gains merit _{G, i}The factor of sending with charge free to load k of sending with charge free is: k _Gi-Lk=P _Gi-Lk/ P _{G, i}, load k active power P _{L, k}The factor of drawing of drawing power from generator i is: k _Lk-Gi=P _Gi-Lk/ P _{L, k}, wherein: P _Gi-LkThe summation of the active power of transmitting between the k for generator i and load;

(2) determine that wind speed changes the compensation scheme that causes the adjustment of exerting oneself:

Determine by wind energy turbine set Ω earlier _WSExert oneself and adjust the Ω that causes _CSAnd Ω _OSThe variable quantity of power output: suppose load Ω _WL, Ω _OLRemain unchanged over a period to come, and Ω _WSIn w seat wind energy turbine set influenced by wind speed, it is exerted oneself and is changed to Δ P _Gw, Ω then _CSIn i platform generator be sent to Ω _WLThe power output adjustment amount of load is:

I ∈ Ω _CS, establish Ω _CSIn i platform generator supply with Ω _WLLoad proportion is γ _i, then supply with Ω _OLThe proportion of middle load is 1-γ _i, Ω for this reason _CSIn i platform generator for remedying Ω _WSIn wind energy turbine set power fluctuation and the power output adjustment amount made is: Δ P _Gi=Δ P ' _Gi/ γ _i, i ∈ Ω _CS, wherein, γ _iTry to achieve by following relation:

Obtain again because Ω _CSMiddle generator output adjustment causes Ω _OLIn k load power supply uneven and need Ω _OSIn j platform output of a generator adjustment amount be:

(3) determine output of wind electric field minor fluctuations compensation scheme at random

Set a fixed threshold, at Ω _CSThe middle γ that selects _iFollow the tracks of wind energy turbine set power fluctuation at random greater than the unit of this fixed threshold, be called automatic generation control AGC unit set omega _CSA, Ω then _CSAThe power adjustment of middle unit i is: Ω _OLIn imbalance power will be by Ω _OSIn balancing machine compensate;

Second step: utilize modal analysis method to select the border of injecting static voltage stability territory, space IVSR is had the crucial generator node of decisive role, the meritorious injection vector of establishing crucial generator is: P _k=[P _{K, 1}, P _{K, 2}..., P _{K, m}];

The 3rd step: determine the wind speed of each wind energy turbine set, and then determine exerting oneself of each wind energy turbine set, the formation wind energy turbine set is transported to the active power P in the electrical network _GwAnd reactive power Q _GwVector;

The 4th step: to active power P _GwAnd reactive power Q _GwVector P _GwCarry out two-way perturbation

When perturbation quantity is Δ P, as follows to P _{Gw, i}(1≤i≤s) enforcement perturbation:

In the formula: subscript+and-represent forward perturbation and negative sense perturbation respectively, the micropower amount of unbalance that perturbation produced passes through Ω _CSAIn the output of wind electric field determined according to the first step of unit at random the minor fluctuations compensation scheme carry out balance, Q _GwDisturbance quantity by Q _GwAnd P _GwAnd the decision of the mapping relations between the wind speed, will be to P _GwAnd Q _GwThe operating point of system is designated as after the enforcement perturbation With it is initial point, determines that system is at P _kInject the voltage in space and stablize critical point, count

In a manner described to P _GwAnd Q _GwIn all wind energy turbine set implement the forward perturbation successively, can get the critical point set of forward perturbation correspondence:

Equally, to P _GwAnd Q _GwAll wind energy turbine set are implemented the negative sense perturbation successively, can get the critical point set of negative sense perturbation correspondence: $X_{P_k}^{-}=\{x_{P_k,1}^{\&prime;-},x_{P_k,2}^{\&prime;-},...,x_{P_k,m}^{\&prime;-}\};$

The 5th step: the territory of finding the solution of bounding hyperplane is revised;

(1) utilizes Obtain the approximate hyperplane on IVSR border by finding the solution m linear equation:

(2) utilize

Can get corresponding bounding hyperplane:

(3) adopt following formula to be revised:

, in the formula: α _iRepresent the hyperplane coefficient, subscript "+" the expression utilization

Obtain the border coefficient of the approximate hyperplane on IVSR border by finding the solution m system of linear equations, subscript "-" expression utilizes

Can get the coefficient of corresponding bounding hyperplane,

The expression initial point

Corresponding critical point, and obtain revised bounding hyperplane H _PFor:

The 6th step: judge whether to run into end condition, if then stop calculating, otherwise continue, end condition is that end condition is calculated in the artificial monitoring of setting of supervisory control system dispatcher, perhaps the end condition after all stable region local boundaries calculating are finished;

The 7th step: when wind farm wind velocity changed, at first the wind speed of determining according to the first step changed and causes that the compensation scheme of adjusting of exerting oneself compensates, and changes for the 3rd step then, continues.

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