CN103956747B - Based on the self adaptation low frequency deloading method of local response message - Google Patents

Abstract

Based on the self adaptation low frequency deloading method of local response message, comprise the steps: 1, establish total N number of load bus in region, install a UFLS relay at each load bus, installation place load bus frequency f measured by i-th relay _ito gain merit P with installation place load _i, relay controling parameters first of adjusting, comprises cutting load operating frequency threshold value f first _set, cutting load threshold value operate time T first _set, cutting load ratio Pshed first, 1; 2, f is monitored _ichange, if f _icontinue lower than f _settime is more than T _set, go to step 3, not so go to step 2; 3, excise Pshed, the load of 1%, goes to step 4; 4, the moment that completes of note step 3 is T _shed, determine moment t1 and t2; 5, UFLS relay second round cut load proportion Pi is calculated, shed, 2; 6, i-th relay excision Pi, shed, the load of 2%; Use the UFLS relay of the inventive method independently to measure, discrete motions, control effects energy self adaptation total system is gained merit, and vacancy changes, inertia changes and part throttle characteristics change.

Description

Based on the self adaptation low frequency deloading method of local response message

Technical field

The invention belongs to power system security protection system technical field, be specifically related to a kind of self adaptation low frequency deloading method based on local response message.

Background technology

Frequency is the important parameter of electric power system, is also one of leading indicator weighing the quality of power supply.Frequency stability is as one of large stability of electric power system three, and its essence is the active balance problem of electric power system.When electric power system is due to off-the-line, when the reasons such as heavy-duty generator group comes off suffer large meritorious disturbance, active balance state between generator and load will be broken, only rely on system own frequency regulating power that frequency retrieval sometimes cannot be made to tolerance interval, at this moment the intervention of frequency urgent control device is needed, wherein UFLS is as the important component part of electric power system three lines of defence, is the essential measure preventing frequency collapse of power system.

Although the application of UFLS is comparatively extensive, still there is some problems in it.The maximum traditional low frequency deloading method of on-the-spot application is a kind of structure by round off-load, the Volume control of its pre-set value, fixing action ensure that the dependable with function that device performs, but due to its validity only off-line verify through limited fault collection, and potential fault scenes cannot be exhaustive, frequency unstability risk still can not be got rid of to not verifying fault set.In addition along with the access of domestic new forms of energy and small power station, after the electric network fault of some areas, the probability of isolated power grid increases, the frequency characteristic of lonely net and the whole network interconnected time will have larger difference, the possibly frequency stabilization that cannot ensure all regions of low frequency load shedding equipment that existing the whole network is under unified central planning.

Existing self adaptation low frequency deloading method, needs to obtain system equivalent inertia size.And when system splitting, heavy-duty generator come off and occur, marked change will occur system equivalent inertia, and the concrete numerical value of change cannot be obtained by load-shedding equipment in time in time, controlled quentity controlled variable will be caused to calculate larger error.If adopt and have control centre's scheme, reliable bidirectional communication network at a high speed must be set up between control centre and each device, and control centre must obtain current system network topology change information in time, decision systems border changes, realize these and require that not only cost is very high, and the technological means of present stage is difficult to the reliability of guarantee system, make the practical distance field reality of control centre's scheme far away; And existing distributing self adaptation low frequency deloading method can not be adaptive to the system inertia change that disturbance causes.

Summary of the invention

In order to solve above-mentioned prior art Problems existing, the object of the present invention is to provide a kind of self adaptation low frequency deloading method based on local response message, the UFLS relay of this method is used only to need to measure local node frequency, frequency change rate and load are gained merit, without the need to communication network, information interaction between control centre and each relay, although use the UFLS relay dispersion of this method to install, self contained function, the vacancy change but each UFLS Control effect summation energy self adaptation total system is gained merit, inertia change and part throttle characteristics change, solving self adaptation UFLS relay that at present dispersion installs cannot the problem of adaptive system inertia change, solve the difficult problem that centralized self adaptation low frequency deloading method needs to build communication network and control centre, solve tradition by round low frequency deloading method and semi adaptive low frequency deloading method off-line setting calculation, solidification action brings the problem controlling flexibility deficiency.

In order to realize foregoing invention object, the technical scheme that the present invention takes is:

Based on the self adaptation low frequency deloading method of local response message, comprise the steps:

Step 1: establish total N number of load bus in region, install a UFLS relay at each load bus, installation place load bus frequency f measured by i-th UFLS relay _ito gain merit P with installation place load _i; To adjust UFLS relay controling parameters first, comprise cutting load operating frequency threshold value f first _set, cutting load threshold value operate time T first _set, cutting load ratio P first _shed, 1;

Step 2: monitoring load bus frequency f _ichange, if load bus frequency f _icontinue the f lower than cutting load operating frequency threshold value first _settime exceedes cutting load threshold value operate time T first _set, go to step 3, not so go to step 2;

Step 3: i-th UFLS relay excision P _{shed, 1}the load of %, goes to step 4;

Step 4: the moment that completes of note step 3 is T _shed, determine moment t1 and t2 according to formula (a) and (b):

t1＝T _shed-Δt ₁(a)

t2＝T _shed+Δt ₂(b)

Δ t ₁t1 moment advanced T _shedduration, Δ t ₂t2 moment delayed T _shedduration, Δ t ₁with Δ t ₂value is generally tens ms;

Step 5: calculate i-th UFLS relay second round cut load proportion P according to formula (c) _{i, shed, 2}, t=0ms is initial time before system disturbance, is also initial time after disturbance:

$P_{i,\mathrm{shed},2}=100\·\{\frac{\frac{{\mathrm{df}}_i}{{\mathrm{dt}}_{t=t1}}}{\frac{{\mathrm{df}}_i}{{\mathrm{dt}}_{t=t1}}-\frac{{\mathrm{df}}_i}{{\mathrm{dt}}_{t=t2}}}\left(\frac{P_{i,t=t1}-P_{i,t=t2}}{P_{i,t=0\mathrm{ms}}}\right)+1-\frac{P_{i,t=t1}}{P_{i,t=0\mathrm{ms}}}\}-P_{\mathrm{shed},1}---\left(c\right)$

p _{i, t=t1}that this nodal frequency rate of change measured by t1 moment i-th UFLS relay and load are gained merit; p _{i, t=t2}that this nodal frequency rate of change of t2 moment i-th measured by low frequency load shedding equipment and load are gained merit; P _{i, t=0ms}that before the system disturbance of recording of i-th relay, initial time load bus absorbs meritorious;

Step 6: i-th UFLS relay excision P _{i, shed, 2}the load of %.

The following describes each UFLS relay and be approximately equal to system initially meritorious vacancy according to the actuating quantity sum that (c) formula performs.

According to the total cutting load amount of each relay of (c) formula be

$P_{i,\mathrm{shed}}=\frac{\frac{{\mathrm{df}}_i}{{\mathrm{dt}}_{t=t1}}}{\frac{{\mathrm{df}}_i}{{\mathrm{dt}}_{t=t1}}-\frac{{\mathrm{df}}_i}{{\mathrm{dt}}_{t=t2}}}\left(P_{\mathrm{i\; t},=t}\stackrel{\‾}{1}{P}_{\mathrm{i\; t}=t,}\right){+}_2(P_{\mathrm{i\; t}=\mathrm{ms},}-P_{0\mathrm{it}=t})---\left(d\right)$

By all N number of relay cutting load amount superpositions, obtain the cutting load amount P that each UFLS relay is total _{shed, total}

$P_{\mathrm{shed},\mathrm{total}}=\underset{i=1}{\overset{N}{\mathrm{\Σ}}}{P}_{i,\mathrm{shed}}=\underset{i=1}{\overset{N}{\mathrm{\Σ}}}\{\frac{\frac{{\mathrm{df}}_i}{{\mathrm{dt}}_{t=t1}}}{\frac{{\mathrm{df}}_i}{{\mathrm{dt}}_{t=t1}}-\frac{{\mathrm{df}}_i}{{\mathrm{dt}}_{t=t2}}}(P_{i,t=t1}-P_{i,t=t2})+\left(P_{i,t=\mathrm{tm}0-P_{i,t=t1}}\right)\}---\left(e\right)$

Consider that frequency is an overall situation amount, with system inertia centre frequency f _coireplace the local frequency f of each node _i, have

$\begin{array}{c}\underset{i=1}{\overset{N}{\mathrm{\Σ}}}\{\frac{\frac{{\mathrm{df}}_i}{{\mathrm{dt}}_{t=t1}}}{\frac{{\mathrm{df}}_i}{{\mathrm{dt}}_{t=t1}}-\frac{{\mathrm{df}}_i}{{\mathrm{dt}}_{t=t2}}}(P_{i,t=t1}-P_{i,t=t2})+(P_{i,t=0\mathrm{ms}}-P_{i,t=t1})\}\≈\\ \underset{i=1}{\overset{N}{\mathrm{\Σ}}}\{\frac{\frac{{\mathrm{df}}_{\mathrm{coi}}}{{\mathrm{dt}}_{t=t1}}}{\frac{{\mathrm{df}}_{\mathrm{coi}}}{{\mathrm{dt}}_{t=t1}}-\frac{{\mathrm{df}}_{\mathrm{coi}}}{{\mathrm{dt}}_{t=t2}}}(P_{i,t}-P_{i,t}-t2)+(P_{i,t=0\mathrm{ms}}-P_{i,t=t1})\}\end{array}---\left(f\right)$

Wherein system inertia centre frequency total M platform generator in supposing the system, f _g,j, M _jfrequency and the moment of inertia of jth platform generator in system.

Consider $\underset{i=1}{\overset{N}{\mathrm{\Σ}}}{P}_{i,t=t1}=P_{L,t=t1},\underset{i=1}{\overset{N}{\mathrm{\Σ}}}{P}_{i,t=t2}=P_{L,t=t2},\underset{i=1}{\overset{N}{\mathrm{\Σ}}}{P}_{i,t=0\mathrm{ms}}=P_{L,t=0\mathrm{ms}}---\left(g\right)$

P in formula _{l, t=t1}, P _{l, t=t2,}p _{l, t=0ms}be respectively system in the t1 moment, before t2 moment and disturbance, initial time load is always gained merit.(g) is substituted into (f) have

$\begin{array}{c}\underset{i=1}{\overset{N}{\mathrm{\Σ}}}\{\frac{\frac{{\mathrm{df}}_{\mathrm{coi}}}{{\mathrm{dt}}_{t=t1}}}{\frac{{\mathrm{df}}_{\mathrm{coi}}}{{\mathrm{dt}}_{t=t1}}-\frac{{\mathrm{df}}_{\mathrm{coi}}}{{\mathrm{dt}}_{t=t2}}}(P_{i,t=t1}-P_{i,t=t2})+(P_{i,t=0\mathrm{ms}}-P_{i,t=t1})\}\\ =\frac{\frac{{\mathrm{df}}_{\mathrm{coi}}}{{\mathrm{df}}_{t=t1}}}{\frac{{\mathrm{df}}_{\mathrm{coi}}}{{\mathrm{dt}}_{t=t1}}-\frac{{\mathrm{df}}_{\mathrm{coi}}}{{\mathrm{dt}}_{t=t2}}}\left(P_{L,t=t1}\right)+(P_{L,t=0\mathrm{ms}}-P_{L,t=t1})\\ =\frac{\frac{{\mathrm{df}}_{\mathrm{coi}}}{{\mathrm{dt}}_{t=t2}}\·P_{L,t=t1}-\frac{{\mathrm{df}}_{\mathrm{coi}}}{{\mathrm{dt}}_{t=t1}}\·P_{L,t=0\mathrm{ms}}}{\frac{{\mathrm{df}}_{\mathrm{coi}}}{{\mathrm{dt}}_{t=t1}}-\frac{{\mathrm{df}}_{\mathrm{coi}}}{{\mathrm{dt}}_{t=t2}}}\\ =\frac{M_{\mathrm{eq}}\frac{{\mathrm{df}}_{\mathrm{coi}}}{{\mathrm{dt}}_{t=t2}}\·P_{L,t=t1}-M_{\mathrm{eq}}\frac{{\mathrm{df}}_{\mathrm{coi}}}{{\mathrm{dt}}_{t=t1}}\·P_{L,t=0\mathrm{ms}}}{M_{\mathrm{eq}}\frac{{\mathrm{df}}_{\mathrm{coi}}}{{\mathrm{dt}}_{t=t1}}-M_{\mathrm{eq}}\frac{{\mathrm{df}}_{\mathrm{coi}}}{{\mathrm{df}}_{t=t2}}}+P_{L,t=0\mathrm{ms}}\end{array}---\left(h\right)$

Wherein $M_{\mathrm{eq}}=\underset{j=1}{\overset{M}{\mathrm{\Σ}}}{M}_j$

Theoretical according to the frequency response of the total system center of inertia, have

$M_{\mathrm{eq}}\frac{{\mathrm{df}}_{\mathrm{coi}}}{\mathrm{dt}}\mathrm{\ΔP}---\left(i\right)$

In formula: M _eq, Δ P, f _coi, t is system equivalent inertia respectively, and system is meritorious vacancy in real time, system inertia centre frequency and time.

I () is all applicable to frequency dynamic overall process, for t1 and the t2 moment, have

$M_{\mathrm{eq}}=\frac{{\mathrm{df}}_{\mathrm{coi}}}{{\mathrm{dt}}_{t=t1}}={\mathrm{\ΔP}}_{t=t1}\left(j\right),M_{\mathrm{eq}}\frac{{\mathrm{df}}_{\mathrm{coi}}}{{\mathrm{dt}}_{t=t2}}={\mathrm{\ΔP}}_{t=t2}\left(k\right)$

Wherein Δ P _t=t1=P _{m, t=t1}-P _{l, t=t1}-Δ P _{loss, t=t1}, Δ P _t=t2=P _{m, t=t2}-P _{l, t=t2}-Δ P _{loss, t=t2}

Δ P _t=t1, P _{m, t=t1}, Δ P _{loss, t=t1}when being t1 respectively, etching system is gained merit amount of unbalance, the total meritorious and circuit active loss of machinery; Δ P _t=t1, P _{m, t=t1}, Δ P _{loss, t=t1}when being t2 respectively, etching system is gained merit amount of unbalance, the total meritorious and circuit active loss of machinery.

Consider equation P _{m, t=0ms}=P _{l, t=0ms}-Δ P _t=0ms+ Δ P _{loss, t=0ms}(l)

P in formula _{m, t=0ms}, P _{l, t=0ms}, Δ P _{loss, t=0ms}, Δ P _t=0mscircuit active loss and system initially meritorious vacancy before always meritorious, the disturbance of initial time load before total meritorious, the disturbance of initial time machinery after system disturbance respectively.

By (j), (k) substitutes into (h), has

$\begin{array}{c}\frac{M_{\mathrm{eq}}\frac{{\mathrm{df}}_{\mathrm{coi}}}{{\mathrm{dt}}_{t=t2}}\·P_{L,t=t1}-M_{\mathrm{eq}}\frac{{\mathrm{df}}_{\mathrm{coi}}}{{\mathrm{dt}}_{t=t1}}\·P_{L,t=t2}}{M_{\mathrm{eq}}\frac{{\mathrm{df}}_{\mathrm{coi}}}{{\mathrm{dt}}_{t=t1}}-M_{\mathrm{eq}}\frac{{\mathrm{df}}_{\mathrm{coi}}}{{\mathrm{dt}}_{t=t2}}}+P_{L,t=0\mathrm{ms}}\\ =\frac{P_{L,t=t1}(P_{m,t=t2}-{\mathrm{\ΔP}}_{\mathrm{Loss},t=t2})-P_{L,t=t2}(P_{m,t=t1}-{\mathrm{\ΔP}}_{\mathrm{Loss},t=t1})}{(P_{m,t=t1}-P_{m,t=t2})-(P_{L,t=t1}-P_{L,t=t2})-({\mathrm{\ΔP}}_{\mathrm{Loss},t=t1}-{\mathrm{\ΔP}}_{\mathrm{Loss},t=t2})}+P_{L,t=0\mathrm{ms}}\\ =\frac{(P_{m,t=0\mathrm{ms}}-{\mathrm{\ΔP}}_{\mathrm{Loss},t=0\mathrm{ms}})-(P_{L,t=t1}-P_{L,t=t2})+{\mathrm{\Δ}}_1}{-(P_{L,t=t1}-P_{L,t=t2})+{\mathrm{\Δ}}_2}\end{array}---\left(m\right)$

In formula (m) $\begin{array}{c}{\mathrm{\Δ}}_1=P_{L,t=t1}\{(P_{m,t=t2}-P_{m,t=0\mathrm{ms}})-({\mathrm{\ΔP}}_{\mathrm{Loss},t=t2}-{\mathrm{\ΔP}}_{\mathrm{Loss},t=0\mathrm{ms}})\}\\ -P_{L,t=t2}\{(P_{m,t=t1}-P_{m,t=0\mathrm{ms}})-({\mathrm{\ΔP}}_{\mathrm{Loss},t=t1}-{\mathrm{\ΔP}}_{\mathrm{Loss},t=0\mathrm{ms}})\}\end{array}$

Δ ₂＝(P _m,t＝t1-P _m, _t＝t2)-(ΔP _Loss,t＝t1-ΔP _Loss,t＝t2)

Consider that [t1, the t2] time period is shorter, system mechanics always meritorious variable quantity, circuit active loss variable quantity all to be gained merit Sudden Changing Rate much smaller than load, has

|Δ ₁|＜＜|-(P _L,t＝t1-P _L,t＝t2)|(n)

Consider owing to considering that the machinery that Genset governor determines always is gained merit initial time after system disturbance, t=t1, t=t2 moment numerical value is close to (t1, t2 moment system frequency is near 49Hz, and after system disturbance, initial time system frequency is at 50Hz), circuit active loss absolute figure is very little, it is initial time after system disturbance, t=t1, t=t2 tri-not in the same time between difference less, therefore have

|Δ ₁|＜＜|(P _m,t＝0ms-ΔP _Loss,t＝0ms)(P _L,t＝t1-P _L,t＝t2)|(o)

Δ is ignored in (m) ₁, Δ ₂two, consider (e), (h), (l), (m), (n), (o) has

P _shed,total≈ΔP _t＝0ms(p)

P () formula illustrates that the total cutting load amount of each UFLS relay is approximately equal to system initially meritorious vacancy.

Self adaptation low frequency deloading method based on local response message utilizes the cutting load first of fixing setting value to cause system loading to be gained merit and undergos mutation, and then cause the local frequency change rate experienced of UFLS relay that disperses to install to be undergone mutation before and after cutting load first, each UFLS relay only needs to measure local frequency, frequency change rate and load are gained merit and can be realized the calculating of self adaptation Load Shedding According To Frequency value, without the need to the information interaction between relay, control and communication center without the need to building for adaptive control, the method that the present invention proposes has good practical application prospect.Although each UFLS relay discrete motions of application the inventive method, but theoretical and emulation all demonstrates the relay load shedding amount sum of each discrete motions close to total system initially meritorious vacancy, and the inventive method controls effective Adaptable System inertia, meritorious vacancy, part throttle characteristics variable effect.The present invention provides solution for electric power system distributing frequency urgent control.

Accompanying drawing explanation

Fig. 1 is the self adaptation low frequency deloading method implementation schematic diagram based on local information response.

Fig. 2 is example system for use in carrying primary connection schematic diagram.

Fig. 3 is each off-load scheme works contrast one after excision 1, No. 11 machines.

Fig. 4 is each off-load scheme works contrast two after excision 1, No. 11 machines.

Fig. 5 be after excision No. 1 machine each off-load scheme works to one.

Fig. 6 is each off-load scheme works contrast two after excision No. 1 machine.

Fig. 7 is each off-load scheme works contrast one after excision 1,11, No. 13 machines.

Fig. 8 is each off-load scheme works contrast two after excision 1,11, No. 13 machines.

Each off-load scheme works contrast one when Fig. 9 is excision 1, No. 11 machine induction machine accountings 60%.

Each off-load scheme works contrast two when Figure 10 is excision 1, No. 11 machine induction machine accountings 60%.

Each off-load scheme works contrast one when Figure 11 is excision 1, No. 11 machine induction machine accountings 70%.

Each off-load scheme works contrast two when Figure 12 is excision 1, No. 11 machine induction machine accountings 70%.

Embodiment

Below in conjunction with drawings and the specific embodiments, the present invention is described in further detail.

IEEE39 system wiring figure as shown in Figure 2,

Investigate meritorious vacancy, when system inertia change, part throttle characteristics change, superiority of the present invention and validity, specifically arranged as table 1.

Table 1 disturbance scene setting

As shown in Figure 1, this example implements the self adaptation low frequency deloading method based on local response message, specific as follows: when disturbance scene is 0.2s, etching system the 1st, No. 11 generators come off, and causes the initial meritorious vacancy of system 39.93%.

Step 1: have 21 load buses in institute Region Of Interest, installs a UFLS relay at each load bus, and installation place load bus frequency f measured by UFLS relay _i(i=1,2 ... 21, correspond respectively to 2,3,4,5,7,8,10,12,14,15,16,17,18,19,20,21,23,24,26,29, No. 30 nodes) and installation place load to gain merit P _i(i=1,2 ... 21), before register system disturbance, initial time load bus absorbs meritorious [P _{1, t=0s}, P _{2, t=0s}, P _{3, t=0s}, P _{4, t=0s}, P _{5, t=0s}, P _{6, t=0s}, P _{7, t=0s}, P _{8, t=0s}, P _{9, t=0s}, P _{10, t=0s}, P _{11, t=0s}, P _{12, t=0s}, P _{13, t=0s}, P _{14, t=0s}, P _{15, t=0s}, P _{16, t=0s}, P _{17, t=0s}, P _{18, t=0s}, P _{19, t=0s}, P _{20, t=0s}, P _{21, t=0s}]=[0.21700.02040.07600.94200.22800.30000.05800.11200.06200. 08200.03500.09000.03200.09500.02200.17500.03200.08700.03 500.02400.1060] (p.u).To adjust UFLS relay controling parameters first, comprise cutting load frequency threshold value f first _set=49Hz, first cutting load time gate threshold value T _set=0.15s, first cutting load ratio P _shed, 1=7.

Step 2: monitoring f _i(i=1,2 ... 21) change, load bus 2,3,4,5,7,8,10,12,14,15,16,17,18,19,20,21,23,24,26,29,30 respectively at 0.88s, 0.88s, 0.88s, 0.87s, 0.88s, 0.88s, 0.88s, 0.88s, 0.88s, 0.88s, 0.88s, 0.88s, 0.88s, 0.88s, 0.88s, 0.88s, 0.88s, 0.88s, 0.88s, 0.88s, the 0.88s moment meets relay and measures installation place load bus frequency keeps lower than 49Hz more than 0.15s.

Step 3: load bus 2,3,4,5,7,8,10,12,14,15,16,17,18,19,20,21,23,24,26,29,30 respectively excise 7% load.

Step 4: the moment that completes of note step 3 is T _shed=[0.88s, 0.88s, 0.88s, 0.87s, 0.88s, 0.88s, 0.88s, 0.88s, 0.88s, 0.88s, 0.88s, 0.88s, 0.88s, 0.88s, 0.88s, 0.88s, 0.88s, 0.88s, 0.88s, 0.88s, 0.88s], determine 21(original text according to formula (a) and (b): moment t1 and t2 6) corresponding to individual relay, get and Δ t is set ₁=30ms, Δ t ₁=70ms, has

T1＝T _shed,1-Δt ₁＝[0.85s,0.85s,0.85s,0.84s,0.85s,0.85s，0.85s,0.85s,0.85s,0.85s,0.85s,0.85s，0.85s,0.85s,0.85s,0.85s,0.85s,0.85s,0.85s,0.85s，0.85s]

T2＝T _shed,1+Δt ₂＝[0.95s,0.95s,0.95s,0.94s,0.95s,0.95s，0.95s,0.95s,0.95s,0.95s,0.95s,0.95s，0.95s,0.95s,0.95s,0.95s,0.95s,0.95s,0.95s,0.95s，0.95s]

Here T1 and T2 is 20 one dimension row vectors, and in T1, each element is corresponding in turn to load bus 2,3,4,5,7,8,10,12,14,15,16,17,18,19, the t1 moment numerical value of 20,21,23,24,26,29,30, in T2, each element is corresponding in turn to load bus 2, and 3,4,5,7,8,10,12,14,15,16,17,18,19, the t2 moment numerical value of 20,21,23,24,26,29,30.

Step 5: calculate UFLS relay second round cut load proportion P according to formula (c) _{i, shed, 2}, t=0ms is initial time before system disturbance (being also initial time after disturbance).

$P_{i,\mathrm{shed},2}=100\·\{\frac{\frac{{\mathrm{df}}_i}{{\mathrm{dt}}_{t=t1}}}{\frac{{\mathrm{df}}_i}{{\mathrm{dt}}_{t=t1}}-\frac{{\mathrm{df}}_i}{{\mathrm{dt}}_{t=t2}}}\left(\frac{P_{i,t=t1}-P_{i,t=t2}}{P_{i,t=0\mathrm{ms}}}\right)+1-\frac{P_{i,t=t1}}{P_{i,t=0\mathrm{ms}}}\}-P_{\mathrm{shed},1}---\left(c\right)$

C the calculating of () formula needs to obtain numerical value, in order to avoid single-point is sampled the error brought, can adopt suitable filtering algorithm during Practical Calculation, this example is in calculating numerical value time adopt following average algorithm:

$\stackrel{\‾}{{\frac{\mathrm{df}}{\mathrm{dt}}}_{t=t1}}=\frac{\frac{\mathrm{df}}{{\mathrm{dt}}_{t=t1-10\mathrm{ms}}}+\frac{\mathrm{df}}{{\mathrm{dt}}_{t=t1}}+\frac{\mathrm{df}}{{\mathrm{dt}}_{t=t1+10\mathrm{ms}}}}{3},\stackrel{\‾}{{\frac{\mathrm{df}}{\mathrm{dt}}}_{t=t2}}=\frac{\frac{\mathrm{df}}{{\mathrm{dt}}_{t=t2-10\mathrm{ms}}}+\frac{\mathrm{df}}{{\mathrm{dt}}_{t=t2}}+\frac{\mathrm{df}}{{\mathrm{dt}}_{t=t2+10\mathrm{ms}}}}{3}$

$\stackrel{\‾}{{\frac{P_{i,t=t1}}{P}}_{i,t=0s}}=\frac{\frac{P_{i,t=t1-10\mathrm{ms}}}{P_{i,t=0s}}+\frac{P_{i,t=t1}}{P_{i,t=t0s}}+\frac{P_{i,t=t1+10\mathrm{ms}}}{P_{i,t=0s}}}{3},\stackrel{\‾}{{\frac{P_{i,t=t2}}{P}}_{i,t=0s}}=\frac{\frac{P_{i,t=t2-10\mathrm{ms}}}{P_{i,t=0s}}+\frac{P_{i,t=t2}}{P_{i,t=t0s}}+\frac{P_{i,t=t2+10\mathrm{ms}}}{P_{i,t=0s}}}{3}$

With $\stackrel{\‾}{{\frac{\mathrm{df}}{\mathrm{dt}}}_{t=t1}},\stackrel{\‾}{{\frac{\mathrm{df}}{\mathrm{dt}}}_{t=t2}},\stackrel{\‾}{{\frac{P_{i,t=t1}}{P}}_{i,t=0\mathrm{ms}}},\stackrel{\‾}{{\frac{P_{i,t=t2}}{P}}_{i,t=0\mathrm{ms}}}$ Replace $\frac{{\mathrm{df}}_i}{{\mathrm{dt}}_{t=t1}},\frac{{\mathrm{df}}_i}{{\mathrm{dt}}_{t=t2}},\frac{P_{i,t=t1}}{P_{i,t=0\mathrm{ms}}},\frac{P_{i,t=t2}}{P_{i,t=0\mathrm{ms}}},$ Have

$\begin{array}{ccccccccccc}[\stackrel{\‾}{{\frac{{\mathrm{df}}_1}{\mathrm{dt}}}_{t=t2}},& \stackrel{\‾}{{\frac{{\mathrm{df}}_2}{\mathrm{dt}}}_{t=t2}},& \stackrel{\‾}{{\frac{{\mathrm{df}}_3}{\mathrm{dt}}}_{t=t2}},& \stackrel{\‾}{{\frac{{\mathrm{df}}_4}{\mathrm{dt}}}_{t=t2}},& \stackrel{\‾}{{\frac{{\mathrm{df}}_5}{\mathrm{dt}}}_{t=t2}},& \stackrel{\‾}{{\frac{{\mathrm{df}}_6}{\mathrm{dt}}}_{t=t2}},& \stackrel{\‾}{{\frac{{\mathrm{df}}_7}{\mathrm{dt}}}_{t=t2}},& \stackrel{\‾}{{\frac{{\mathrm{df}}_8}{\mathrm{dt}}}_{t=t2}},& \stackrel{\‾}{{\frac{{\mathrm{df}}_9}{\mathrm{dt}}}_{t=t2}},& \stackrel{\‾}{{\frac{{\mathrm{df}}_{10}}{\mathrm{dt}}}_{t=t2}},& \stackrel{\‾}{{\frac{{\mathrm{df}}_{11}}{\mathrm{dt}}}_{t=t2}},\\ \stackrel{\‾}{{\frac{{\mathrm{df}}_{12}}{\mathrm{dt}}}_{t=t2}},& \stackrel{\‾}{{\frac{{\mathrm{df}}_{13}}{\mathrm{dt}}}_{t=t2}},& \stackrel{\‾}{{\frac{{\mathrm{df}}_{14}}{\mathrm{dt}}}_{t=t2}},& \stackrel{\‾}{{\frac{{\mathrm{df}}_{15}}{\mathrm{dt}}}_{t=t2}},& \stackrel{\‾}{{\frac{{\mathrm{df}}_{16}}{\mathrm{dt}}}_{t=t2}},& \stackrel{\‾}{{\frac{{\mathrm{df}}_{17}}{\mathrm{dt}}}_{t=t2}},& \stackrel{\‾}{{\frac{{\mathrm{df}}_{18}}{\mathrm{dt}}}_{t=t2}},& \stackrel{\‾}{{\frac{{\mathrm{df}}_{19}}{\mathrm{dt}}}_{t=t2}},& \stackrel{\‾}{{\frac{{\mathrm{df}}_{20}}{\mathrm{dt}}}_{t=t2}},& \stackrel{\‾}{{\frac{{\mathrm{df}}_{21}}{\mathrm{dt}}}_{t=t2}}]& \\ =[-17833.& -1.7833& -1.7833& -1.7833& -1.7833& -1.7667& -1.7667& & & & \\ -1.7668& -1.7667& -1.7667& -1.7667& -1.7667& -1.7667& -1.7667& & & & \\ -1.7667& -1.7667& -1.7667& -1.7667& -1.7667& -1.7667,& -1.7833\left]\right(\mathrm{Hz}/s);& & & & \end{array}$

$\begin{array}{ccccccccccc}[\stackrel{\‾}{{\frac{{\mathrm{df}}_1}{\mathrm{dt}}}_{t=t2}},& \stackrel{\‾}{{\frac{{\mathrm{df}}_2}{\mathrm{dt}}}_{t=t2}},& \stackrel{\‾}{{\frac{{\mathrm{df}}_3}{\mathrm{dt}}}_{t=t2}},& \stackrel{\‾}{{\frac{{\mathrm{df}}_4}{\mathrm{dt}}}_{t=t2}},& \stackrel{\‾}{{\frac{{\mathrm{df}}_5}{\mathrm{dt}}}_{t=t2}},& \stackrel{\‾}{{\frac{{\mathrm{df}}_6}{\mathrm{dt}}}_{t=t2}},& \stackrel{\‾}{{\frac{{\mathrm{df}}_7}{\mathrm{dt}}}_{t=t2}},& \stackrel{\‾}{{\frac{{\mathrm{df}}_8}{\mathrm{dt}}}_{t=t2}},& \stackrel{\‾}{{\frac{{\mathrm{df}}_9}{\mathrm{dt}}}_{t=t2}},& \stackrel{\‾}{{\frac{{\mathrm{df}}_{10}}{\mathrm{dt}}}_{t=t2}},& \stackrel{\‾}{{\frac{{\mathrm{df}}_{11}}{\mathrm{dt}}}_{t=t2}},\\ \stackrel{\‾}{{\frac{{\mathrm{df}}_{12}}{\mathrm{dt}}}_{t=t2}},& \stackrel{\‾}{{\frac{{\mathrm{df}}_{13}}{\mathrm{dt}}}_{t=t2}},& \stackrel{\‾}{{\frac{{\mathrm{df}}_{14}}{\mathrm{dt}}}_{t=t2}},& \stackrel{\‾}{{\frac{{\mathrm{df}}_{15}}{\mathrm{dt}}}_{t=t2}},& \stackrel{\‾}{{\frac{{\mathrm{df}}_{16}}{\mathrm{dt}}}_{t=t2}},& \stackrel{\‾}{{\frac{{\mathrm{df}}_{17}}{\mathrm{dt}}}_{t=t2}},& \stackrel{\‾}{{\frac{{\mathrm{df}}_{18}}{\mathrm{dt}}}_{t=t2}},& \stackrel{\‾}{{\frac{{\mathrm{df}}_{19}}{\mathrm{dt}}}_{t=t2}},& \stackrel{\‾}{{\frac{{\mathrm{df}}_{20}}{\mathrm{dt}}}_{t=t2}},& \stackrel{\‾}{{\frac{{\mathrm{df}}_{21}}{\mathrm{dt}}}_{t=t2}}]& \\ =[-1.4333& -1.4500& -1.4500& -1.4500& -1.4500& -1.4500& -1.4667& & & & \\ -1.4667& -1.4667& -1.4667& -1.4667& -1.4883& -1.4667& -1.4667& & & & \\ -1.4833& -1.4667& -1.4667& -1.4667& -1.4833& -1.4833& -1.500\left]\right(\mathrm{Hz}/s);& & & & \end{array}$

$\begin{array}{ccccccccccc}[\stackrel{\‾}{{\frac{P_{1,t=t1}}{P}}_{1,t=0\mathrm{ms}}}& \stackrel{\‾}{{\frac{P_{2,t=t1}}{P}}_{2,t=0\mathrm{ms}}}& \stackrel{\‾}{{\frac{P_{3,t=t1}}{P}}_{3,t=0\mathrm{ms}}}& \stackrel{\‾}{{\frac{P_{4,t=t1}}{P}}_{4,t=0\mathrm{ms}}}& \stackrel{\‾}{{\frac{P_{5,t=t1}}{P}}_{5,t=0\mathrm{ms}}}& \stackrel{\‾}{{\frac{P_{6,t=t1}}{P}}_{6,t=0\mathrm{ms}}}& \stackrel{\‾}{{\frac{P_{7,t=t1}}{P}}_{7,t=0\mathrm{ms}}}& \stackrel{\‾}{{\frac{P_{8,t=t1}}{P}}_{8,t=0\mathrm{ms}}}& \stackrel{\‾}{{\frac{P_{9,t=t1}}{P}}_{9,t=0\mathrm{ms}}}& \stackrel{\‾}{{\frac{P_{10,t=t1}}{P}}_{10,t=0\mathrm{ms}}}& \stackrel{\‾}{{\frac{P_{11,t=t1}}{P}}_{11,t=0\mathrm{ms}}}\\ \stackrel{\‾}{{\frac{P_{12,t=t1}}{P}}_{12,t=0\mathrm{ms}}}& \stackrel{\‾}{{\frac{P_{13,t=t1}}{P}}_{13,t=0\mathrm{ms}}}& \stackrel{\‾}{{\frac{P_{14,t=t1}}{P}}_{14,t=0\mathrm{ms}}}& \stackrel{\‾}{{\frac{P_{15,t=t1}}{P}}_{15,t=0\mathrm{ms}}}& \stackrel{\‾}{{\frac{P_{16,t=t1}}{P}}_{16,t=0\mathrm{ms}}}& \stackrel{\‾}{{\frac{P_{17,t=t1}}{P}}_{17,t=0\mathrm{ms}}}& \stackrel{\‾}{{\frac{P_{18,t=t1}}{P}}_{18,t=0\mathrm{ms}}}& \stackrel{\‾}{{\frac{P_{19,t=t1}}{P}}_{19,t=0\mathrm{ms}}}& \stackrel{\‾}{{\frac{P_{20,t=t1}}{P}}_{20,t=0\mathrm{ms}}}& \stackrel{\‾}{{\frac{P_{21}}{P}}_{21,t=0\mathrm{ms}}}]& \\ =[0.9108& 0.9077& 0.9086& 0.9172& 0.9101& 0.9083& 0.8814& & & & q\\ 0.9032& 0.9006& 0.8972& 0.8931& 0.8843& 0.8909& 0.8873& & & & q\\ 0.8856& 0.8815& 0.8925& 0.8870& 0.8906& 0.8954& 0.8953];& & & & q\end{array}$

$\begin{array}{ccccccccccc}[\stackrel{\‾}{{\frac{P_{1,t=t2}}{P}}_{1,t=0\mathrm{ms}}},& \stackrel{\‾}{{\frac{P_{2,t=t2}}{P}}_{2,t=0\mathrm{ms}}},& \stackrel{\‾}{{\frac{P_{3,t=t2}}{P}}_{3,t=0\mathrm{ms}}},& \stackrel{\‾}{{\frac{P_{4,t=t2}}{P}}_{4,t=0\mathrm{ms}}},& \stackrel{\‾}{{\frac{P_{5,t=t2}}{P}}_{5,t=0\mathrm{ms}}},& \stackrel{\‾}{{\frac{P_{6,t=t2}}{P}}_{6,t=0\mathrm{ms}}},& \stackrel{\‾}{{\frac{P_{7,t=t2}}{P}}_{7,t=0\mathrm{ms}}},& \stackrel{\‾}{{\frac{P_{8,t=t2}}{P}}_{8,t=0\mathrm{ms}}},& \stackrel{\‾}{{\frac{P_{9,t=t2}}{P}}_{9,t=0\mathrm{ms}}}& \stackrel{\‾}{{\frac{P_{10,t=t2}}{P}}_{10,t=0\mathrm{ms}}}& \stackrel{\‾}{{\frac{P_{11,t=t2}}{P}}_{11,t=0\mathrm{ms}}},\\ \stackrel{\‾}{{\frac{P_{12,t=t2}}{P}}_{12,t=0\mathrm{ms}}}& ,\stackrel{\‾}{{\frac{P_{13,t=t2}}{P}}_{13,t=0\mathrm{ms}}}& ,\stackrel{\‾}{{\frac{P_{14,t=t2}}{P}}_{14,t=0\mathrm{ms}}}& ,\stackrel{\‾}{{\frac{P_{15,t=t2}}{P}}_{15,t=0\mathrm{ms}}}& \stackrel{\‾}{{\frac{P_{16,t=t2}}{P}}_{16,t=0\mathrm{ms}}}& \stackrel{\‾}{{\frac{P_{17,t=t2}}{P}}_{17,t=0\mathrm{ms}}}& \stackrel{\‾}{{\frac{P_{18,t=t2}}{P}}_{18,t=0\mathrm{ms}}}& \stackrel{\‾}{{\frac{P_{19,t=t2}}{P}}_{19,t=0\mathrm{ms}}}& \stackrel{\‾}{{\frac{P_{20,t=t2}}{P}}_{20,t=0\mathrm{ms}}}& \stackrel{\‾}{{\frac{P_{21,t=t2}}{P}}_{21,t=0\mathrm{ms}}]}& \end{array}$

$\begin{array}{ccccccc}=[0.8522& 0.8515& 0.8525& 0.8594& 0.8547& 0.8534& 0.8309\\ 0.8477& 0.8469& 0.8445& 0.8404& 0.8337& 0.8400& 0.8373\\ 0.8356& 0.8321& 0.8419& 0.8380& 0.8427& 0.8465& 0.8475];\end{array}$

And P _{shed, 1}=7, therefore have

[P _1,shed,2,P _2,shed,2,P _3,shed,2,P _4,shed,2,P _5,shed,2,P _6,shed,2,P _7,shed,2,P _8,shed,2,P _9,shed,2,P _10,shed,2,P _11,shed,2,P _12,shed,2,P _13,shed,2,P _14,shed,2,P _15,shed,2,P _16,shed,2,P _17,shed,2,P _18,shed,2,P _19,shed,2,P _20,shed,2,P _21,shed,2]=[31.768432.303932.152032.222731.623032.783834.605435.365434.596234.328834.756636.116333.902835.406435.615933.935033.562533.152833.812933.942033.5734];

Step 6: consider that various time delay adds up to 100ms, load bus 2,3,4,5,7,8,10,12,14,15,16,17,18,19,20,21,23,24,26,29,30 respectively at 1.05s, 1.05s, 1.05s, 1.04s, 1.05s, 1.05s, 1.05s, 1.05s, 1.05s, 1.05s, 1.05s, 1.05s, 1.05s, 1.05s, 1.05s, 1.05s, 1.05s, 1.05s, 1.05s, 1.05s, 1.05s excise the load of 31.8%32.3%32.2%32.2%31.6%32.8%34.6%35.4%34.6%34.3%34.8%3 6.1%33.9%35.4%35.6%33.9%33.6%33.2%33.8%33.9%33.6%.

Consider load bus 2,3,4,5,7,8,10,12,14,15,16,17,18,19,20,21,23,24,26,29,30 before system disturbance initial time load bus absorb meritorious P _{i, t=0ms}sequence [the P of composition _{1, t=0s}, P _{2, t=0s}, P _{3, t=0s}, P _{4, t=0s}, P _{5, t=0s}, P _{6, t=0s}, P _{7, t=0s}, P _{8, t=0s}, P _{9, t=0s}, P _{10, t=0s}, P _{11, t=0s}, P _{12, t=0s}, P _{13, t=0s}, P _{14, t=0s}, P _{15, t=0s}, P _{16, t=0s}, P _{17, t=0s}, P _{18, t=0s}, P _{19, t=0s}, P _{20, t=0s}, P _{21, t=0s}]=[0.21700.02040.07600.94200.22800.30000.05800.11200.06200. 08200.03500.09000.03200.09500.02200.17500.03200.08700.03 500.02400.1060] (p.u), the total cutting load amount ratio completed based on the self adaptation UFLS relay two-wheeled action of local response message is 40.02%, very close to system initially meritorious vacancy 39.93%.

In order to contrast adaptive control effect of the present invention, choose certain general by round a scheme, certain general by round b scheme, certain is general by round c scheme, accelerate front the 2 semi adaptive a schemes of taking turns based on by round a scheme, carries out Contrast on effect based on semi adaptive b scheme five kinds of schemes of taking turns by round a scheme acceleration front 3.Specifically in table 3, table 4 and table 5.

Certain is general in round a scheme for table 3

Certain is general in round b scheme for table 4

Certain is general in round c scheme for table 5

Semi adaptive a scheme is taken turns for accelerating to cut second when cutting the first round by round a scheme simultaneously, and semi adaptive b scheme is taken turns for accelerating to cut second and third when cutting the first round by round a scheme simultaneously.

In order to avoid contrast scheme crosses cutting load, when also add every round cutting load when controlling locking link, namely when system frequency is recovered, cutting load trip(ping) circuit possesses blocking function.

Under disturbance scenario A, the contrast effect of each scheme is shown in Fig. 3 and accompanying drawing 4; As can be seen from the figure: adopting the present invention program, to control (duration 40s) system low-limit frequency in rear whole dynamic process the highest in six kinds of control programs, system highest frequency is than by round a scheme, low by round b scheme, semi adaptive a scheme, semi adaptive b scheme.After controlling by round c scheme, system there occurs frequency unstable phenomenon (low-limit frequency is lower than 47.5Hz); By round a scheme, control rear system there occurs frequency over control (highest frequency is higher than 51.5Hz) by round b scheme, semi adaptive a scheme, semi adaptive b scheme; And utilize the present invention program to control rear whole dynamic process medium frequency response curve all to meet the requirements.Comprehensively it seems that the present invention program's control effects is optimum in whole six kinds of control programs.

Under disturbance scenario B, the contrast effect of each scheme is shown in Fig. 5 and Fig. 6, as can be seen from the figure: adopting the present invention program, to control (duration 40s) system low-limit frequency in rear whole dynamic process the highest in six kinds of control programs, system highest frequency is than by round a scheme, low by round c scheme, semi adaptive a scheme, semi adaptive b scheme.After controlling by round a scheme, semi adaptive a scheme, semi adaptive b scheme, system there occurs frequency over control (highest frequency is higher than 51.5Hz); Utilize the present invention program to control rear whole dynamic process medium frequency response curve all to meet the requirements.Comprehensively it seems that the present invention program's control effects is optimum in whole six kinds of control programs.

Under disturbance scene C, the contrast effect of each scheme is shown in Fig. 7 and Fig. 8, as can be seen from the figure: adopting the present invention program, to control (duration 40s) system low-limit frequency in rear whole dynamic process the highest in six kinds of control programs, system highest frequency is than low by round a scheme, semi adaptive a scheme, semi adaptive b scheme.By round b scheme, there occurs frequency unstable phenomenon (low-limit frequency is lower than 47.5Hz) by system after the control of round c scheme; After controlling by round a scheme, semi adaptive a scheme, semi adaptive b scheme, system there occurs frequency over control (highest frequency is higher than 51.5Hz); Utilize the present invention program to control rear whole dynamic process medium frequency response curve all to meet the requirements.Comprehensively it seems that the present invention program's control effects is optimum in whole six kinds of control programs.

Under disturbance scene D, the contrast effect of each scheme is shown in Fig. 9 and Figure 10, as can be seen from the figure: adopting the present invention program, to control (duration 40s) system low-limit frequency in rear whole dynamic process the highest in six kinds of control programs, system highest frequency is than low by round a scheme, semi adaptive a scheme, semi adaptive b scheme.After controlling by round c scheme, system there occurs frequency unstable phenomenon (low-limit frequency is lower than 47.5Hz); After controlling by round a scheme, semi adaptive a scheme, semi adaptive b scheme, system there occurs frequency over control (highest frequency is higher than 51.5Hz); And utilize the present invention program to control rear whole dynamic process medium frequency response curve all to meet the requirements.Comprehensively it seems that the present invention program's control effects is optimum in whole six kinds of control programs.

Under disturbance scene E, the contrast effect of each scheme is shown in Figure 11 and Figure 12, as can be seen from the figure: adopting the present invention program, to control (duration 40s) system low-limit frequency in rear whole dynamic process the highest in six kinds of control programs, system highest frequency is than low by round a scheme, semi adaptive a scheme, semi adaptive b scheme.After controlling by round c scheme, system there occurs frequency unstable phenomenon (low-limit frequency is lower than 47.5Hz); After controlling by round a scheme, system there occurs frequency over control (highest frequency is higher than 51.5Hz); And utilize the present invention program to control rear whole dynamic process medium frequency response curve all to meet the requirements.Comprehensively it seems that the present invention program's control effects is optimum in whole six kinds of control programs.

Disturbance scenario A, B, C have different systems initially meritorious vacancy and system inertia, and the present invention program all has good control effects under three kinds of scenes, illustrate that the present invention program effectively can be adaptive to system and to gain merit the change of vacancy and system inertia.

Disturbance scenario A, D, E have different part throttle characteristics, and the present invention program all has good control effects under three kinds of scenes, illustrate that the present invention program can the change of effective self adaptation part throttle characteristics.

Claims (1)

1., based on the self adaptation low frequency deloading method of local response message, it is characterized in that, comprise the following steps:

Step 1: establish total N number of load bus in region, install a UFLS relay at each load bus, installation place load bus frequency f measured by i-th UFLS relay _ito gain merit P with installation place load _i; To adjust UFLS relay controling parameters first, comprise cutting load operating frequency threshold value f first _set, cutting load threshold value operate time T first _set, cutting load ratio P first _{shed, 1};

Step 2: monitoring load bus frequency f _ichange, if load bus frequency f _icontinue lower than cutting load operating frequency threshold value f first _settime exceed cutting load threshold value operate time T first _set, go to step 3, not so go to step 2;

Step 3: i-th UFLS relay excision P _{shed, 1}the load of %, goes to step 4;

Step 4: the moment that completes of note step 3 is T _shed, determine moment t1 and t2 according to formula (a) and (b):

t1＝T _shed-Dt ₁(a)

t2＝T _shed+Dt ₂(b)

Dt ₁t1 moment advanced T _shedduration, Dt ₂t2 moment delayed T _shedduration, Dt ₁and Dt ₂value is tens ms;

Step 5: calculate UFLS relay second round cut load proportion P according to formula (c) _{i, shed, 2}, t=0ms is initial time before system disturbance, is also initial time after disturbance:

$P_{i,\mathrm{shed},2}=100\·\{\frac{{\frac{{\mathrm{df}}_i}{\mathrm{dt}}}_{t=t1}}{{\frac{{\mathrm{df}}_i}{\mathrm{dt}}}_{t=t1}-{\frac{{\mathrm{df}}_i}{\mathrm{dt}}}_{t=t2}}\left(\frac{P_{i,t=t1}-P_{i,t=t2}}{P_{i,t=0\mathrm{ms}}}\right)+1-\frac{P_{i,t=t1}}{P_{i,t=0\mathrm{ms}}}\}-P_{\mathrm{shed},1}---\left(c\right)$

p _{i, t=t1}that this nodal frequency rate of change measured by t1 moment i-th UFLS relay and load are gained merit; p _{i, t=t2}that this nodal frequency rate of change measured by t2 moment i-th UFLS relay and load are gained merit; P _{i, t=0ms}that before the system disturbance of recording of i-th UFLS relay, initial time load bus absorbs meritorious;

Step 6: i-th UFLS relay excision P _{i, shed, 2}the load of %.