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What is Distributed Generation


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What is Distributed Generation

  2. 2. REFRENCE IEEE TRANSACTIONS ON POWER DELIVERY, VOL. 28, NO. 1 Voltage Stability Based DG Placement in Distribution Networks BY H. Ghasemi , S. Vaez Zadeh (senior member ,IEEE) 2
  3. 3. content 1. What is DG? 2. Why DG? 3. Earlier used techniques 4. Techniques used in this paper 5. Case study 6. Application 7. Conclusion 1
  4. 4. WhatisDistributedGeneration?  The small energy-generation units which are connected to distribution system are referred to as "Distributed Generation”.  The best definition for DG is, "the source of electrical energy is connected to distribution networks or directly to the consumer side". 2
  6. 6. DistributedGenerationDiagram 4
  8. 8. WHYDG?  System Security  Reliability  Efficiency  Quality  Active Management of distribution network 6
  9. 9. earlierusetechnique’s,How tooselectbestlocationfordg  voltage stability index – most sensitive bus too voltage collapse in radial distribution system Problem – an equivalent two bus system is used for the analysis of voltage stability  bus indices – for considering the effect of aggregated dg in voltage security of transmission grid are developed 7
  10. 10. Newtechniquesfordgplacement  Voltage stability technique – • Modal analysis • Continuous power flow  Ranking method – priority list for dg location for compensating reactive power 8
  11. 11. ModalAnalysisforVoltageStabilityEvaluation  A system is voltage unstable if for at least one bus in the system bus voltage magnitude decreases as the reactive power injection at the same bus is increased.  other words, a system is voltage stable if V-Q sensitivity is positive or every bus and unstable if V-Q sensitivity is negative for at least one bus. 9
  12. 12. ReducedJacobianMatrix  The linearized steady state system power voltage equations are given by- ∆P = incremental change in bus real power. ∆Q=incremental change in bus reactive power injection. ∆θ = incremental change in bus voltage angle. ∆V= incremental change in bus voltage magnitude. 10
  13. 13. at each operating point we keep P constant and evaluate voltage stability by considering the incremental relationship between Q and V. To reduce the above equations we assume ∆P= ∆P=0.  JR is called the reduced Jacobian matrix of the system. JR is the matrix which directly relates the bus voltage magnitude and bus reactive power injection. 11
  14. 14. The ith mode of the Q-V response is defined by the ith eigenvalue , and the corresponding right and left eigenvectors. Since Using this in ∆V, we get By defining v=η∆V vector of modal voltage variation q= η∆Q vector of modal reactive power variation We can write uncoupled first order equation as- 12
  15. 15. Thus for ith mode voltage variation is - Vi=1/ λi * qi  If λi >0 , the ith modal voltage and the ith modal reactive power variations move in the same direction, indicating voltage stability of the system.  whereas λi <0 refers to instability of the system. 13
  16. 16. The relative contribution of the power at bus k in mode i is given by the bus participation factor Pki= ℰ ki* η ki Participation factors determine the most critical areas which  lead the system to instability.  Higher the magnitude bus participation factor better be the remedial action taken too stabilize the mode. 13
  17. 17. Continuouspowerflowmethodology  Determination of max loading is one of the most important problem in voltage stability analysis that can’t be calculated by model analysis. This uses successive solution, to compute the voltage profile up too the collapse point  there jacobian become singular to determine voltage security margin 14
  18. 18. DgplacementALGORITHM DG Placement Process The DG placement problem is solved here by using modal analysis and the CPF method by an objective of voltage security margin enhancement and loss reduction. 14
  19. 19. 15
  20. 20. Dgplacementevaluationindices  ALR – active loss reduction  RLR – reactive loss reduction higher values indicate better performance VI index – lower value better the performance of dg units 16
  22. 22. CASE STUDY Application of DG placement Algorithm Application of the placement method and the corresponding indices are examined on the well-known 33-bus radial distribution network. The system total apparent load is 4.3694 MVA and DG penetration in all cases is considered to be 40% (i.e., 1.7477 MVA). 18
  23. 23. MODIFIEDEQUIVALENTREACTIVEPOWERCOMPENSATION METHOD(MERC)  Uses (QLI) – to determine priority list of dg to compensate reactive power shortages It will not seek VSM 19
  25. 25. System active and reactive losses for different placement scenarios when DGs active power is limited to 0.4 total load and no voltage regulation is performed by DGs. 21
  27. 27. The proposed placement algorithm is implementable in different DG penetration scenarios 23
  28. 28. Due to the radial nature of distribution networks, the buses of each network branch, from the tail to the main feeder, usually have participation factors in a descending order for a specific mode. the 33-bus radial networks participation factors for mode 1 in descending order when DG at bus 18 24
  29. 29. APPLICATIONOFRANKINGMETHOD . Application of the ranking method is examined on all candidate buses obtained from the placement algorithm, bus 28 is the best site for reactive power compensation in the case of shortage. 25
  30. 30. The places are ranked using an MERC method, which determines a priority list of DG locations for reactive power compensation during occasions of reactive power shortage.  The placement algorithm is executed and remedial effect of DGs, both in loss reduction and voltage profile improvement in normal operation, and enhancement of the loading parameter in the case of voltage instability The ranking method is executed over the obtained candidates to provide a priority list from the view point of reactive power compensation in the case of shortage. 26
  31. 31. CONCLUSION DG placement is different from the best location for reactive power compensation and VSM in the presence of a voltage- stability problem. Long-term DG placement problem can be solved by CPF and modal analysis while the short-term reactive power issues can be addressed by the ranking method 27
  32. 32. REFRENCES R. Cossent, T. Gomez, and P. Fras, “Towards a future with large penetration of distributed generation: Is the current regulation of electricity distribution ready? Regulatory recommendations under a European perspective,” Int. J. Energy Policy, vol. 37, pp. 1145–1155, 2009. . Chakravorty and D. Das, “Voltage stability analysis of radial distribution networks, M. E. Baran and F. F. Wu, “Network recon figuration in distribution systems for loss reduction and load balancing,” IEEE Trans. Power H. A. Gil, M. E. Chehaly, G. Joos, and C. A. Caizares, “Bus-based indices for assessing the contribution of DG to the voltage security margin of the transmission grid,” presented at the IEEE Power Energy 28
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