CN102097806A - Low frequency deloading method for stabilizing frequency of interconnected power grids - Google Patents

Abstract

The invention relates to a low frequency deloading method for stabilizing the frequency of interconnected power grids. The low frequency deloading method is characterized by comprising the following steps of: inputting parameters of an interconnected power grid system; partitioning the interconnected power grid system; performing homology equivalence on homologous units in the partitions; setting low frequency deloading of the partitions; performing dynamic frequency characteristic analysis on the interconnected power grid system; determining a deloading position and a deloading amount; and setting a low frequency deloading scheme of the interconnected power grid system. By the scheme provided by the invention, the interconnected power grids are simplified rationally, the deloading process is layered rationally, and quick and effective deloading can be realized under the condition of faults.

Description

A kind of low frequency deloading method that is used for the interconnected network frequency stabilization

Technical field

The present invention relates to the power system frequency antihunt means, specifically relate to a kind of low frequency deloading method that is used for the interconnected network frequency stabilization.

Background technology

The big regional interconnected network direction of electric power system forward develops.Along with scale of power and unit capacity constantly enlarge, part throttle characteristics becomes increasingly complex, electric network composition constantly changes.The regional frequency characteristic otherness of interconnected network and the influence that brings thereof are remarkable day by day.Frequency-response analysis and UFLS setting method based on the same frequency hypothesis of the whole network are challenged.Be difficult to satisfy the requirement of safety analysis of interconnected network frequency and control.And before each large regional grid and the new province's mesh that adds networking still according to the UFLS scheme operation during isolated network operation the networking, and each electrical network UFLS scheme has difference.In large-scale interconnected systems, after had by the frequency change in disturbance area and non-disturbance area to have earlier, be subjected to the decrease speed of disturbance area frequency very fast, but not the variation of the regional frequency of disturbance lag behind.Therefore be difficult to guarantee that the burst island network that may form after whole networked system or the accident is taking place under the high-capacity power vacancy situation, can be rationally load shedding equably, stop frequency to descend big trend fluctuation do not take place, prevent the frequency collapse accident.

It is not independent of each other that dynamic change of large-scale power system medium frequency and frequency stabilization, angle stability, voltage are stablized, but brings out mutually, and the not ipsilateral of the unified physical phenomenon that is mutually related is subjected to the influence of network configuration and operation conditions.The electromotive force of generator is relevant with generator speed, and when the General System frequency reduced, the voltage of system also decreased.When generator voltage reduces along with the frequency reduction, make the idle minimizing of exerting oneself, then make system's reactive power vacancy bigger.Transient state studies show that, is accompanied by electric power system superpower vacancy accident, and often concurrent reactive power is lost in a large number, and the active power of system and the reactive power equilibrium of supply and demand are subjected to very big disturbance.Be subjected to the disturbance area the serious decline of voltage will occur.In order to keep the constant of frequency, should determine the quantity and the position of load shedding by the variation of voltage.

Generating board number too much can increase amount of calculation in the complication system.In order to simplify calculating, in dynamic process, relative angle changes not too largely between them for those, and their the similar generator of absolute angle Changing Pattern is called a people having the same aspiration and interest group of planes in other words, they can be merged into an equivalent unit and participate in calculating.The multimachine system that satisfies the equivalent condition of the people having the same aspiration and interest is being carried out people having the same aspiration and interest polymerization front and back, and the mechanical output that generating set is total and total electromagnetic power are constant.In large-scale interconnected systems, system to mutual contact carries out people having the same aspiration and interest subregion, is divided into different zonules, on the one hand the frequency change after the simulated failure comparatively accurately, can accelerate computational speed on the other hand, realize controlling in real time comparatively accurately the UFLS measure.

Summary of the invention

The objective of the invention is difference at the dynamic frequency characteristic of subregion electrical network and interconnected network, system is rationally simplified to interconnected network, the off-load process is carried out reasonable layering, be implemented under the failure condition off-load fast and effectively, the invention provides a kind of low frequency deloading method that is used for the interconnected network frequency stabilization.

For realizing purpose of the present invention, the present invention adopts following proposal to be achieved:

A kind of low frequency deloading method that is used for the interconnected network frequency stabilization, its improvements are that described low frequency deloading method may further comprise the steps:

A, input interconnected network system parameters;

B, described interconnected network system is carried out subregion;

C, the people having the same aspiration and interest unit in the described subregion is carried out people having the same aspiration and interest equivalence;

D, the UFLS of subregion is adjusted;

E, described interconnected network system is carried out the dynamic frequency characteristic analysis;

F, determine load shedding position and load shedding quantity;

G, the interconnected network system of adjusting UFLS scheme.

A kind of optimized technical scheme provided by the invention is: in the described steps A, described interconnection network system parameter comprises electric network composition, load level, installed capacity, spinning reserve capacity, electric generator structure and generator parameter, load configuration and generator parameter, utilizing the trend computational tool to carry out trend calculates, the trend that obtains base regime is separated assumed load growing direction t=0.

Second kind of optimized technical scheme provided by the invention is: among the described step B, according to described interconnected network system parameters described interconnected network system is carried out subregion.

The third optimized technical scheme provided by the invention is: among the described step C, described people having the same aspiration and interest equivalence is that an equivalent unit participates in calculating, and the frequency characteristic of described equivalent unit is

The 4th kind of optimized technical scheme provided by the invention is: among the described step D, the UFLS of described subregion is realized with loadshedding equipment; Described loadshedding equipment adopts the UFLS pattern of " basic wheel+reserve wheel+urgent wheel ".

The 5th kind of optimized technical scheme provided by the invention is: in the described step e, the dynamic frequency characteristic of described interconnected network system is analyzed dynamic frequency characteristic Δ W (s)=S (MS of described interconnected network system on the basis that subregion is simplified ²+ DS+ ω ₀J) ^-1(Δ P _m(s)+L Δ P _L(s)).

The 6th kind of optimized technical scheme provided by the invention is: in the described step F, determine described load shedding position and load shedding quantity by the variation of voltage.

The 7th kind of optimized technical scheme provided by the invention is: among the described step G, determine load shedding position and the quantity interconnected network system UFLS scheme of adjusting according to the dynamic frequency characteristic of described interconnected network system and described change in voltage.

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

A kind of low frequency deloading method that is used for the interconnected network frequency stabilization provided by the invention carries out people having the same aspiration and interest equivalence at the complexity of interconnected network UFLS to the subregion electrical network, analyzes the frequency characteristic of interconnected network on the basis of equivalence; At the difference of the dynamic frequency characteristic of subregion electrical network and interconnected network, adopt the method for layering off-load, the layering off-load is at first preferentially cutting corresponding load at the interconnected network subregion that is subjected to big disturbance; Secondly differentiate interconnected network load shedding amount and load shedding position automatically by the interconnected network system; And determine off-load quantity and off-load position according to the variation of voltage; Interconnected network is rationally simplified, the off-load process is carried out reasonable layering, realized under failure condition off-load fast and effectively.

Description of drawings

Fig. 1 is the flow chart that is used for the low frequency deloading method of interconnected network frequency stabilization of the present invention.

Embodiment

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

Fig. 1 is the flow chart that is used for the low frequency deloading method of interconnected network frequency stabilization of the present invention, and this low frequency deloading method may further comprise the steps:

A, input interconnected network system parameters;

B, the interconnected network system is carried out subregion;

C, the people having the same aspiration and interest unit in the subregion is carried out people having the same aspiration and interest equivalence;

D, the UFLS of subregion is adjusted;

E, the interconnected network system is carried out the dynamic frequency characteristic analysis;

F, determine load shedding position and load shedding quantity;

G, the interconnected network system of adjusting UFLS scheme.

Being implemented as follows of each step:

Because the factor differences such as electric network composition, load level, installed capacity, spinning reserve capacity, electric generator structure and parameter thereof, load configuration and parameter thereof between the electrical network of each department, thereby cause frequency characteristic difference.At first import the interconnected network system parameters, interconnected network is carried out subregion; The foundation of subregion is to utilize similar the classification and abbreviation of people having the same aspiration and interest group of planes frequency dynamic characteristic.These othernesses according to electrical network are divided into different subregions with electrical network, and in each subregion dynamic process, relative angle changes not too large generator between them, is called a people having the same aspiration and interest group of planes, they are merged into an equivalent unit participate in calculating.The instrument that subregion of the present invention adopts is that BPA power system analysis program means PSD-BPA carries out trend calculating, obtains the combination of a people having the same aspiration and interest group of planes.The equation of rotor motion of supposing j platform unit in the subregion is (1) formula:

${\left(J{\mathrm{\Ω}}_N^2\right)}_j\frac{d(\mathrm{\ω}/{\mathrm{\ω}}_N)}{\mathrm{dt}}=T_{\mathrm{mj}}-T_{\mathrm{ej}}=\frac{1}{\mathrm{\ω}/{\mathrm{\ω}}_N}(P_{\mathrm{mj}}-P_{\mathrm{Lj}})---\left(1\right)$

The total h platform unit of the unification of setting up departments obtains (2) formula with all generator amature equation of motion additions that move units:

$[{\left(J{\mathrm{\Ω}}_N^2\right)}_1+{\left(J{\mathrm{\Ω}}_N^2\right)}_2+...+{\left(J{\mathrm{\Ω}}_N^2\right)}_h]\frac{d(\mathrm{\ω}/{\mathrm{\ω}}_N)}{\mathrm{dt}}=\frac{1}{\mathrm{\ω}/{\mathrm{\ω}}_N}(\underset{j=1}{\overset{h}{\mathrm{\Σ}}}{P}_{\mathrm{mj}}-\underset{j=1}{\overset{h}{\mathrm{\Σ}}}{P}_{\mathrm{Lj}})---\left(2\right)$

Because $\frac{{\left(J{\mathrm{\Ω}}_N^2\right)}_j}{S_s}=\frac{{\left(J{\mathrm{\Ω}}_N^2\right)}_j}{S_j}\·\frac{S_j}{S_s}=M_j\frac{S_j}{S_s}$

Wherein M _jInertia constant for unit j.

The inertia time constant that obtains equivalent generator is the inertia time constant sum of each generator reduction to reference power, that is:

$M_s={\mathrm{\Σ}}_j^h\frac{M_j{S}_j}{S_s}---\left(3\right)$

S in the formula _jSpecified generated output for unit j; S _sSummation for the rated output power of all units of moving in the system.

So the equation of rotor motion of equivalent generator can be expressed as:

$M_s\frac{d\left(\frac{\mathrm{\ω}}{{\mathrm{\ω}}_N}\right)}{\mathrm{dt}}=\frac{P_{{\mathrm{ms}}^{*}}-P_{{\mathrm{Ls}}^{*}}}{\frac{\mathrm{\ω}}{{\mathrm{\ω}}_N}}---\left(4\right)$

Be the active power perunit value of the power supply of remaining system, Active power perunit value for the remaining system load.

Because

$\frac{d{\mathrm{\ω}}^{*}}{\mathrm{dt}}=\frac{\mathrm{d\Δ}{\mathrm{\ω}}^{*}}{\mathrm{dt}}=\frac{\mathrm{d\Δ}{f}^{*}}{\mathrm{dt}}---\left(5\right)$

So formula can be written as

$M_s\frac{\mathrm{d\Δ}{f}^{*}}{\mathrm{dt}}=\frac{P_{{\mathrm{ms}}^{*}}-P_{{\mathrm{Ls}}^{*}}}{f^{*}}---\left(6\right)$

The frequency dynamic characteristic of interconnected network subregion electrical network can be obtained by (6) formula.The derivation of the frequency dynamic characteristic of whole interconnected network is as follows.The dynamic frequency characteristic of the interconnected network that different subregions are formed is drawn by following derivation.Derivation is based on following hypothesis:

(1) linearized system model;

(2) the meritorious trend of system is mainly determined by the phase angle of voltage in the network, and is little with its magnitude relation;

(3) classical generator model is not considered the effect of pressure regulation.

Obtaining the generator amature equation of motion is:

$\frac{\mathrm{d\Δ}{\mathrm{\δ}}_t}{\mathrm{dt}}={\mathrm{\ω}}_0\mathrm{\Δ}{\mathrm{\ω}}_i---\left(7\right)$

$M\frac{\mathrm{d\Δ\δ}{\mathrm{\ω}}_i}{\mathrm{dt}}=\mathrm{\Δ\ω}{P}_{\mathrm{mi}}-\mathrm{\Δ}{P}_{\mathrm{Gi}}-D_i\mathrm{\Δ}{\mathrm{\ω}}_i---\left(8\right)$

Network equation is:

$\left[\begin{array}{c}\mathrm{\Δ}{P}_G\\ \mathrm{\Δ}{P}_L\end{array}\right]=\left[\begin{array}{cc}{H}_{\mathrm{GG}}& H_{\mathrm{GL}}\\ H_{\mathrm{LG}}& H_{\mathrm{LL}}\end{array}\right]\left[\begin{array}{c}\mathrm{\Δ\δ}\\ \mathrm{\Δ\θ}\end{array}\right]---\left(9\right)$

In the formula: Δ P _G, Δ δ is the N dimensional vector;

Δ P _L, Δ θ is the K dimensional vector.

The H battle array satisfies following:

$\left\{\begin{array}{c}{H}_{\mathrm{GG}}{I}_N+H_{\mathrm{GL}}{I}_K=0\\ H_{\mathrm{LG}}{I}_N+H_{\mathrm{LL}}{I}_K=0\end{array}\right.---\left(10\right)$

Get from formula (9) cancellation Δ θ according to formula (10):

ΔP _G＝JΔ5+LΔP _L (11)

In the formula:

Each row element sum of J battle array is zero

$L=H_{\mathrm{GL}}{H}_{\mathrm{LL}}^{-1}\∈R^{N\×N}---\left(12\right)$

Comprehensively (8), (9), (10) and (11) get:

$\stackrel{\·}{X}=\mathrm{AX}+\mathrm{BU}---\left(13\right)$

In the formula:

$X=\left[\begin{array}{c}\mathrm{\Δ\δ}\\ \mathrm{\Δ\ω}\end{array}\right]---\left(14\right)$

$U=\left[\begin{array}{c}\mathrm{\Δ}{P}_m\\ \mathrm{\Δ}{P}_L\end{array}\right]---\left(15\right)$

$A=\left[\begin{array}{cc}0& 0\\ -M^{-1}J& -M^{-1}D\end{array}\right]---\left(17\right)$

$B=\left[\begin{array}{cc}0& 0\\ M^{-1}& M^{-1}L\end{array}\right]---\left(18\right)$

M＝diag[M ₁…M _N] (19)

D＝diag[D ₁…D _K] (20)

Set up departments and original machine power disturbance Δ P takes place in the system _mWith load disturbance Δ P _L, carry out Laplace transformation and cancellation Δ δ gets:

ΔW(s)＝S(MS ²+DS+ω ₀J) ^-1(ΔP _m(s)+LΔP _L(s)) (21)

Formula (21) is the Mathematical Modeling that adopts when the UFLS scheme is closed in complicated interconnected systems frequency dynamic process and school.

Above-mentioned is the derivation of complicated interconnected systems frequency dynamic, determines to determine in the frequency change process position and the quantity of UFLS below.The method that the present invention adopts is to determine the quantity and the position of load according to the variation of voltage.The electromotive force of generator is relevant with generator speed, and when system frequency reduced, the voltage of system also decreased; When generator voltage reduces along with the frequency reduction, make the idle minimizing of exerting oneself, then make system's reactive power vacancy bigger.Be subjected to the disturbance area the serious decline of voltage will occur,, determine the quantity and the position of load shedding by the variation of voltage in order to keep the constant of frequency.

Trend accounting equation commonly used is:

P _i＝V _i∑ _j∈iV _j(G _ijcosθ _ij+B _ijsinθ _ij)(i＝1，2，…n) (22)

Q ₁＝V _i∑ _j∈iV _j(G _ijsinθ _ij-B _ijcosθ _ij)(i＝1，2，…n) (23)

In the formula: G _IjAnd B _IjFor the electricity of circuit is led and susceptance.

V _iAnd θ _iVoltage magnitude and phase angle for node i.

J ∈ i represents the node j that all are directly related with node i, comprises the situation of j=i.

$\left[\begin{array}{c}\mathrm{\ΔP}\\ \mathrm{\ΔQ}\end{array}\right]=\left[\begin{array}{cc}H& N\\ G& L\end{array}\right]\left[\begin{array}{c}\mathrm{\Δ\θ}\\ \mathrm{\ΔV}/V\end{array}\right]---\left(24\right)$

In the formula:

$H_{\mathrm{ij}}=\frac{\∂\mathrm{\Δ}{P}_i}{\∂{\mathrm{\θ}}_j}---\left(25\right)$

$N_{\mathrm{ij}}=\frac{\∂\mathrm{\Δ}{P}_i}{\∂{\mathrm{\θ}}_j}{V}_j---\left(26\right)$

$J_{\mathrm{ij}}=\frac{\∂\mathrm{\Δ}{Q}_i}{\∂{\mathrm{\θ}}_j}---\left(27\right)$

$L_{\mathrm{ij}}=\frac{\∂\mathrm{\Δ}{Q}_i}{\∂V_j}{V}_j---\left(28\right)$

Node power deviation equation was identical during node power increment equation and trend were calculated, but Δ P and Δ Q formula power deviation amount in node power deviation equation, the sign that they go to zero and finish as iteration in the Practical Calculation Chinese style, Δ P in the node power increment equation and Δ Q formula system power increment, the existence of this increment directly influences the variation of system frequency and voltage.

(24) formula is simplified: the reactance of each element is supposed i node active power amount of unbalance Δ P much larger than resistance in the electric power networks _iVariation only cause each node voltage phase angle θ _i, θ _jVariation, do not cause V _i, V _jVariation; The uneven Δ Q of reactive power _iVariation only cause each node V _i, V _jVariation, do not cause its phase angle θ _i, θ _jVariation, the N in the formula (24), J submatrix are omitted and it are reduced to:

$\left[\begin{array}{c}\mathrm{\ΔP}\\ \mathrm{\ΔQ}\end{array}\right]=\left[\begin{array}{cc}H& 0\\ 0& L\end{array}\right]\left[\begin{array}{c}\mathrm{\Δ\θ}\\ \mathrm{\ΔV}/V\end{array}\right]---\left(25\right)$

Can get by (25) formula:

[ΔQ]＝[0?L][ΔV/V] (26)

By formula (26) as can be known, the variation of node voltage will provide Useful Information, in order to determine to be subjected to the disturbance area, be necessary the decline in short-term of measuring voltage.

Will Substitution formula (26):

Here only consider the variation of voltage in very short time at initial stage that disturbance takes place, because computing time is short, approximately think that reactive power flow does not also shift, the reactive power vacancy of i node only influences the voltage of this node.

$\mathrm{\ΔQ}={\mathrm{\Σ}}_{i=1}^N\mathrm{\Δ}{Q}_i={\mathrm{\Σ}}_{i=1}^N\left[\mathrm{\Δ}{V}_i\frac{\∂\mathrm{\Δ}{Q}_i}{\∂V_i}\right]---\left(29\right)$

$\frac{\mathrm{\Δ}{Q}_i}{\mathrm{\ΔQ}}=\frac{\mathrm{\ΔV}\∂\mathrm{\Δ}{Q}_i/\∂V_i}{\underset{i=1}{\overset{N}{\mathrm{\Σ}}}\mathrm{\Δ}{V}_i\∂\mathrm{\Δ}{Q}_i/\∂V_i}---\left(30\right)$

The idle disturbance of node and the relation between the meritorious disturbance:

ΔP _i＝K _iΔQ _i (31)

In the time of normal operation, each node power factor of system is generally 0.8～0.9, does not have unsteadyly too greatly, thinks K so can be similar to ₁=K ₂=... K _N, can get by top hypothesis:

$\frac{\mathrm{\Δ}{P}_i}{\mathrm{\ΔP}}=\frac{\mathrm{\Δ}{V}_i\∂\mathrm{\Δ}{Q}_i/\∂V_i}{\underset{i=1}{\overset{N}{\mathrm{\Σ}}}\mathrm{\Δ}{V}_i\∂\mathrm{\Δ}{Q}_i/\∂V_i}---\left(32\right)$

$L_{\mathrm{ii}}=\frac{\∂\mathrm{\Δ}{Q}_i}{\∂V_i}{V}_i={V_i}^2{B}_{\mathrm{ii}}-Q_i---\left(33\right)$

$\frac{\∂Q_i}{\∂V_i}={V_i}^2{B}_{\mathrm{ii}}-Q_i/V_i---\left(34\right)$

ΔP＝∑P _LS (35)

$\mathrm{\Δ}{P}_i=\frac{\mathrm{\Δ}{V}_i({V_i}^2{B}_{\mathrm{ii}}-Q_i/V_i)}{\underset{i=1}{\overset{N}{\mathrm{\Σ}}}\mathrm{\Δ}{V}_i({V_i}^2{B}_{\mathrm{ii}}-Q_i/V_i)}\mathrm{\Σ}{P}_{\mathrm{LS}}---\left(36\right)$

In the formula: Δ V _iVoltage decline minimum for node i;

N is all nodes that big change in voltage is arranged;

∑ P _LSBe the total load shedding power of system.

Obtain the cutting load amount of each comparatively serious node of voltage drop according to following formula, behind the corresponding load of each node excision, finally make system frequency be stabilized in one preferably on the level.

More than subregion frequency characteristic, interconnected systems frequency characteristic have been carried out detailed inference, also load shedding point and load shedding amount have been carried out quantizing to calculate.Next whole interconnected systems low frequency load shedding method is described, the load shedding method adopts layering load shedding method, by point and face, realizes the rapidity and the science of UFLS.

The layering cutting load is divided into the subregion ground floor and the interconnected systems second layer.

At the disturbance initial stage, because generated output withdraws from a large number, frequency sharply descends, and the result of calculation that low-frequency load reduction control system has little time to provide definite is in order to determine the position and the quantity of cutting load.The loadshedding equipment that be distributed in subregion this moment can adopt the UFLS pattern of " basic wheel+reserve wheel+urgent wheel " in time to move, and alleviates frequency and descends.Basic wheel moves and takes turns level, respectively takes turns particularly first run operating frequency of operating frequency, determines by common power shortage mode, promptly takes turns to be defined as according to the df/dt size and quickens the round that cutting load constitutes.When the basic wheel first round starts, quicken to cut basic wheel second and take turns and be defined as the urgent first round, take turns the first round substantially and quicken to cut basic wheel when starting second, third is taken turns and is defined as urgent second and takes turns, and the like.The operating frequency of reserve wheel should be not less than the starting frequency of taking turns the first round substantially, and takes certain time-delay, treats to move when system frequency is more stable, and frequency retrieval is arrived more than the limit value of permission, below is subregion load shedding scheme:

Discriminant when (1) frequency slowly descends is as follows:

F≤f _Qd, t 〉=t _QdLow-frequency start;

F≤f _Dz1, t 〉=t _Dz1Basic wheel first round action;

F≤f _Dz2, t 〉=t _Dz2Basic wheel second is taken turns action;

F≤f _Dz3, t 〉=t _Dz3The action of basic wheel third round;

F≤f _Dz4, t 〉=t _Dz4The action of basic wheel four-wheel.

(2) big, the frequency of the meritorious vacancy discriminant when very fast that descends

F≤f _Qd, t 〉=t _QdLow-frequency start;

f≤f _dz1，t≥t _dz1

Df/dt＜(df/dt) _Dz1Basic wheel first round action;

(df/dt) _Dz1＜df/dt＜(df/dt) _Dz2Urgent first round action (cut substantially and take turns the first round, quicken to cut second simultaneously and take turns);

(df/dt) _Dz2＜df/dt＜(df/dt) _Dz3Urgent second takes turns action (cut substantially and take turns the first round, quicken to cut second and third simultaneously and take turns).

(3) recover underfrequency, the discriminant when frequency is hovered

F≤f _Qd, t 〉=t _QdLow-frequency start;

F≤f _Hb, t 〉=t _HbThe action of back wheel.

(4) prevent to take turns substantially the discriminant that the 3rd class " is crossed and cut "

The open basic wheel outlet in df/dt＜0 (system frequency is in the decline process);

Outlet (system frequency is in uphill process) is taken turns in df/dt＞0 locking substantially.

Wherein, f _Qd, t _QdBe the low-frequency start definite value and the time-delay definite value of this device, f _Dzi, t _DziBe the action definite value and the time-delay definite value of basic wheel i wheel, f _Hb, t _HbBe the operating value and the time-delay definite value of reserve wheel, (df/dt) _Dz1, (df/dt) _Dz2Be the urgent first round and the urgent second action definite value of taking turns, (df/dt) _Dz2Be slippage locking definite value.

In case big disturbance subregion low frequency load shedding equipment action alleviates frequency and descends, position and the quantity of sufficient time by low-frequency load reduction control system calculating load shedding is just arranged, below be total load shedding total amount and load shedding position:

If system has sufficient spinning reserve capacity (SR), the load shedding total amount is:

∑P _LS＝ΔP _G-K _LΔf _ss-SR (37)

If do not have sufficient spinning reserve capacity in the system, the load shedding total amount is:

∑P _LS＝ΔP _G-K _LΔf _ss (38)

∑ P in the formula _LSBe load shedding power; Δ P _GThe generated output that withdraws from for accident; K _LBe the Load Regulation effect coefficient.

In order to calculate the load shedding position, at first to determine the load shedding scope.The voltage of this node descends and only continues the very short time, but the voltage minimum point can go on record, and the load shedding power of node i can be expressed as:

$\mathrm{\Δ}{P}_i=\frac{\mathrm{\Δ}{V}_i({V_i}^2{B}_{\mathrm{ii}}-Q_i/V_i)}{\underset{i=1}{\overset{N}{\mathrm{\Σ}}}\mathrm{\Δ}{V}_i({V_i}^2{B}_{\mathrm{ii}}-Q_i/V_i)}\mathrm{\Σ}{P}_{\mathrm{LS}}---\left(39\right)$

EMS in the modern power systems (being called for short EMS) provides the data in formula (37), (38) and (39).

Low-frequency load reduction control system obtains corresponding data as required and calculates from the EMS system server, determine big disturbance area according to result of calculation, and sends the cutting load order to the low frequency load shedding equipment of this area, informs the quantity of cutting load.

Load shedding power also may appear at those and deducted in the subregion load shedding on the node of a large amount of loads this moment, in other words, whole load shedding scheme is applicable to the most serious power shortage and two kinds of situations of provincialism power shortage, finally makes system frequency be stabilized in one preferably on the level.

Should be noted that at last: only illustrate that in conjunction with the foregoing description technical scheme of the present invention is not intended to limit.Those of ordinary skill in the field are to be understood that: those skilled in the art can make amendment or are equal to replacement the specific embodiment of the present invention, but these modifications or change are all among the claim protection range that application is awaited the reply.

Claims (8)

1. a low frequency deloading method that is used for the interconnected network frequency stabilization is characterized in that, described low frequency deloading method may further comprise the steps:

A, input interconnected network system parameters;

B, described interconnected network system is carried out subregion;

C, the people having the same aspiration and interest unit in the described subregion is carried out people having the same aspiration and interest equivalence;

D, the UFLS of subregion is adjusted;

E, described interconnected network system is carried out the dynamic frequency characteristic analysis;

F, determine load shedding position and load shedding quantity;

G, the interconnected network system of adjusting UFLS scheme.

2. a kind of low frequency deloading method that is used for the interconnected network frequency stabilization as claimed in claim 1, it is characterized in that, in the described steps A, described interconnection network system parameter comprises electric network composition, load level, installed capacity, spinning reserve capacity, electric generator structure and generator parameter, load configuration and generator parameter, utilizing the trend computational tool to carry out trend calculates, the trend that obtains base regime is separated assumed load growing direction t=0.

3. a kind of low frequency deloading method that is used for the interconnected network frequency stabilization as claimed in claim 1 is characterized in that, among the described step B, according to described interconnected network system parameters described interconnected network system is carried out subregion.

4. a kind of low frequency deloading method that is used for the interconnected network frequency stabilization as claimed in claim 1 is characterized in that, among the described step C, the described people having the same aspiration and interest is equivalent to be participated in calculating with equivalent unit, and the frequency characteristic of described equivalent unit is

$M_s\frac{\mathrm{d\Δ}{f}^{*}}{\mathrm{dt}}=\frac{P_{{\mathrm{ms}}^{*}}-P_{L{s}^{*}}}{f^{*}}.$

5. a kind of low frequency deloading method that is used for the interconnected network frequency stabilization as claimed in claim 1 is characterized in that among the described step D, the UFLS of described subregion is realized with loadshedding equipment; Described loadshedding equipment adopts the UFLS pattern of " basic wheel+reserve wheel+urgent wheel ".

6. a kind of low frequency deloading method that is used for the interconnected network frequency stabilization as claimed in claim 1, it is characterized in that, in the described step e, on the basis that subregion is simplified, the dynamic frequency characteristic of described interconnected network system is analyzed dynamic frequency characteristic Δ W (s)=S (MS of described interconnected network system ²+ DS+ ω ₀J) ^-1(Δ P _m(s)+L Δ P _L(s)).

7. a kind of low frequency deloading method that is used for the interconnected network frequency stabilization as claimed in claim 1 is characterized in that, in the described step F, determines described load shedding position and load shedding quantity by the variation of voltage.

8. a kind of low frequency deloading method that is used for the interconnected network frequency stabilization as claimed in claim 1, it is characterized in that, among the described step G, determine load shedding position and the quantity interconnected network system UFLS scheme of adjusting according to the dynamic frequency characteristic of described interconnected network system and described change in voltage.

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