ee5970 ems-scada model presentation

An optimal load shedding strategy for Islanded Distribution networkNameRoll Number

ObjectivesUnder-frequency Load Shedding SchemeBlock DiagramFormulationLoad Shedding ManagerAlgorithmLoad PriorityCase StudySensitivity AnalysisConclusionsReferences

Saptarshi Prakash (EE09B076)*CONTENTSRoll No Name EE5970: EMS-SCADA

Roll No Name EE5970: EMS-SCADA

Islanding - isolation from the rest of the power system network.

Main challenge load - generation balance

If the islanded system is under generated (over load), it leads to frequency drop.

Frequency decay is more severe in case of distribution system.

If no control action is taken, it leads to system collapse

To prevent this condition, load shedding is used

*1.IntroductionRoll No Name EE5970: EMS-SCADA


Smart grids are modernized electrical grids .Smart Grid =Electrical Grids +Digital layer

Smart grid are being developed with the objectives of Improving efficiency reliability and sustainability of production and distribution of Electrical energy.1. Introduction*Roll No Name EE5970: EMS-SCADA


2. Objectives

To implement a simple and efficient load shedding scheme for an islanded distribution network which can1.shed an optimal number of loads2.maintains the system stability by keeping the frequency within acceptable limits.*Roll No Name EE5970: EMS-SCADA


3.Scope of workStudy of different existing load shedding schemes

Implement an UFLS algorithm for optimal load shedding.

Verify effectiveness of the scheme through Matlab / Simulink software.

*Roll No Name EE5970: EMS-SCADA


*4. Literature Review1. Conventional UFLS Scheme

i. Shed loads if frequency goes below threshold value.

ii. fixed amount of load is shed at fixed intervals.

iii. Slow response

iV. Unnecessary load shed

Roll No Name EE5970: EMS-SCADACont


*4. Literature Review3. RoCoF based load shedding phenomenon

f and ROCOF (df/dt) as input signals

More frequency drop leads to more loads shed.

Fixed load is shed in each stage

Roll No Name EE5970: EMS-SCADACont


*4. Literature Review3. Adaptive Load Shedding Scheme

online measurement of system parameters

Actual magnitude of power loss is known.

Redundant communication links



5. Need for studyLoad shedding action must be initiated quickly to curtail the excess load during islanding condition

Minimum amount of load to be shed and also keeping the system stability.

Most of the existing adaptive Load shedding schemes requires various communication devices and links

Hence the optimal Load shedding scheme should consider both technical and economical factors



*Saptarshi Prakash (EE09B076)5. Block DiagramRoll No Name EE5970: EMS-SCADA


5. Project Process Flow Diagram*Roll No Name EE5970: EMS-SCADA


6. Implementation of UFLS algorithm*ContRoll No Name EE5970: EMS-SCADA


start

No

ROCOF < ROCOFl

Nl < = N

f < fl

df/dt < = 0 for T times

No

Measure frequency at every 10 ms

Calculate number of loads (N) to be shed from load priority table

Shed the load ranked Nl

stop

N = N+1

N = 0

Yes

Yes

Yes

Delay time (CB+ Relay pick up)

No

Yes

Yes

No

No

Fault Simulated cleared within t=0.1s 6. Test System Under Consideration / Study*Roll No Name EE5970: EMS-SCADA


*Saptarshi Prakash (EE09B076)6. Schematic Representation of Case StudyRoll No Name EE5970: EMS-SCADA


7. Test Distribution system[6] Pukar Mahat, Zhe Chen and Birgitte Bak-Jensen, Under-Frequency Load Shedding for an Islanded Distribution System with Distributed Generators, IEEE Transaction on Power Delivery, Volume 25, Issue 2, Pages 911 -918, April 2010*Roll No Name EE5970: EMS-SCADA

SL.NoDescriptionTotal (No.s)1Buses142 Generators 63Loads11


8. Test data Considered 1. LOAD AND GENERATION DATA [7] 2. GENERATOR DATA [7] Pukar Mahat, Zhe Chen and Birgitte Bak-Jensen, A Hybrid Islanding Detection Technique Using Average Rate of Voltage Change and Real Power Shift, IEEE Transaction on Power Delivery, Volume 24, Issue 2, Pages 764 771, April 2009Cont

Bus-no PG (MW)QG(MVAr)PL(MW)QL(MW)590006007.64171.16077000.45230.20038000.71240.31159000.11310.050110000.11310.050111000.11310.0501120.63000130.63000140.63000

Sl.NoParameterGas Turbine GeneratorWind Turbine Generator1Rated power3 MW630 KW2Rated Voltage6.3kV0.4 kV3Inertia Constant0.54 0.38

1.Calculating df/dt corresponding to a load with deficiency equal to its peak value (November month)

2. Given system has deficiency of 3.31 MW (peak load) in month of December.

3.Rate of change of frequency (df/dt) for 3.31 MW deficiency is -46 Hz/s

9. Results*Roll No Name EE5970: EMS-SCADA

Sl.NoLoad PL(MW)df/dt (Hz/s)1Load-11.888-48.362Load-20.89-30.663Load-32.521-69.864Load-41.158-36.345Load-51.699-53.336Load-61.901-52.917Load-70.4995-22.828Load-80.7868-28.539Load-90.1249-15.6610Load-100.1249-15.6611Load-110.1249-15.66


Here load with highest peak demand value is shed firstThe Load priority table is 3. In this case, load -3 will shed at 0.09 s 4. Load-7 and load-9 also need be shed to maintain system stability.5. Total load shed amount is 3.3 MW*Roll No Name EE5970: EMS-SCADA 0.9699. CASE STUDY : Highest Peak Demand

Rank (NL)Load P(MW)RoCoFLi RoCoFLi1Load-32.521-69.86-69.862Load-70.4995-22.82-92.683Load-90.1249-15.66-108.344Load-100.1249-15.66-1245Load-41.158-36.24-160.246Load-11.888-48.36-208.67Load-110.1249-15.66-224.268Load-20.89-30.63-254.899Load-61.901-52.91-307.810Load-80.7868-28.53-336.3311Load-51.699-53.23-389.56


10. Conclusions

Less amount of load is shed in case -3 compare to case -1 and case-2.Frequency drop is also less in case-3.

2. The methodology is simple and it can be easily implemented in load shedding relays



11. Important References[1] K. Raiamani, U.K. Hambarde, Islanding and load shedding schemes for captive power plants, IEEE Transactions on Power Delivery, vol. 14, no. 3, July 1999 [2] C. Concordia, L. H. Fink, G. Poullikkas, Load shedding on an isolated system, IEEE Transactions on Power Systems, vol. 13, no. 3, 1995, pp. 1467 1472[3] X. Ding and A. A. Girgis, Optimal load shedding strategy in power systems with distributed generation, Winter Meeting in Power Engineering society, 2001.IEEE, pp. 788 793, Vol.2. [4] V. Tarija, Adaptive under frequency load shedding based on the magnitude of the disturbance , IEEE Transactions on Power Systems, vol. 21, no. 3,2006, pp. 12601266[5] M.S. Pasand, H .Seyedi, New centralized adaptive under frequency load shedding algorithms, in proc. of Power Engineering conference on Large Engineering Systems, Montreal, 2007[6] Pukar Mahat, Zhe Chen and Birgitte Bak-Jensen, Under-Frequency Load Shedding for an Islanded Distribution System with Distributed Generators, IEEE Transaction on Power Delivery, Volume 25, Issue 2, Pages 911 -918, April 2010[7] Pukar Mahat, Zhe Chen and Birgitte Bak-Jensen, A Hybrid Islanding Detection Technique Using Average Rate of Voltage Change and Real Power Shift, IEEE Transaction on Power Delivery, Volume 24, Issue 2, Pages 764 771, April 2009[8] ] U. Rudez, R. Mihalic, Analysis of under frequency load shedding using a frequency gradient, IEEE Transactions on Power Systems, vol. 26, no. 2, April. 2011 [9] Y. Xu, Y. Dai, Z. Y. Dong, Y. Xue, K. P. Wong, Load shedding and its strategies against frequency Instability in power systems, in IEEE proc. of Power and Engineering Society general meeting, San Diego, CA, 2012*Roll No Name EE5970: EMS-SCADA


The EndRoll No Name EE5970: EMS-SCADA*


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ee5970 ems-scada model presentation

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