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OPTIMAL ARRANGEMENT OF DIFFERENT TYPES OF DG SOURCES IN DISTRIBUTION NETWORKS

Guided byPresented byMs.S.Thangalakshmi,Aran Glenn.JAssociate Professor,Reg No: 410812411002Dept. of Electrical and Electronics Engineering, G.K.M College of Engineering and Technology,Chennai.

Abstract In the present work the optimal placement of different types of DGs has been proposed. The optimal locations and size of the DGs have been determined by minimizing the power distribution loss. The optimal power factor for DG supplying, both real and reactive power, has been obtained in this work. Different types of DGs supplying real and reactive power at different buses have also been considered in the proposed approach. The particle swarm optimization (PSO) technique has been used to solve the optimal placement of DGs. The results obtained from the PSO technique have also been compared with the analytical approach results. The proposed technique is tested on 33-bus test system. Also total power loss can be found out by using differential evolution.

IntroductionObjectiveTraditional electric power generation

Operation of traditional generation systems

Justification

Distributed GenerationDGs are also referred to as Embedded Generations or Disperse Generations. There is no consensus definition for DG, as it depends upon many technologies and many applications in different environments.

International Energy Agency (IEA) :

Define distributed generation as generating plant serving a customer on-site or providing support to a distribution network, connected to the grid at distribution level voltages.

Distributed GenerationFuture Scope :The share of distributed generators (DGs) in power systems has been slowly increasing in the last few years and there is no sign that it would decrease in near future. Moreover, the policy initiatives to promote DG throughout the world also indicate that the number will grow rapidly.

ACTIVE AND REACTIVE POWER COMPENSATION

Optimal placement of DG only producing real power.

Optimal placement of DG and Capacitor being integrated.

Inappropriate allocation of the DG unit may adverse the system performance.

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Location And Sizing Issues

Bus no.%DG Size Loss (MW)Optimal Sizing of DG and Capacitor

The real power loss formula is represented by:

For minimum losses, the rate of change of losses with respect to injected power becomes zero.

Optimal Sizing of DG and Capacitor

Optimal Sizing of DG and CapacitorThe above equations gives the size of DG and Capacitor for each bus i, for the loss to be minimum.

Optimal size of DG and Capacitor1. Any size of DG and Capacitor other than PDGi and QDGi placed at bus i, will lead to higher loss. 2. can be determined by satisfying the system constraints.

10Optimal Power Factor When the optimum values of DG and Capacitor are obtained as above.

The power factor of the DG may be considered as optimal and represented as

Optimal Location The optimal location can be find for the placement of optimal sizes of DG and Capacitor as obtained, which will give the lowest possible total loss due to placement of DG and Capacitor at the respective bus, say bus i and j.

ith bus is the optimal location to place the DG.

jth bus is the optimal location to place the Capacitor.

If the optimal location for DG and Capacitor placement is same, say bus i. Then power factor of DG can be determined at bus i. Objective FunctionThe objective is to compensate the active power and reactive power while meeting the following constraints by PSO approach.

Constraints:System power flow equations must be satisfied.Voltage constraint at each bus (5% ) must be satisfied.

Line current constraint must be satisfied.

Particle Swarm OptimizationParticle swarm optimization (PSO) is a population-based optimization technique which provides a population-based search procedure in which individuals called particles change their position (state) with time.

Particles : These are the entities which move around in a multidimensional search space.Velocity : Every particle moves in the search space with a velocity associated with it.Personal Best : During flight, each particle has its own personal best experience (This value is called Pbest).

Particle Swarm OptimizationGlobal Best : It is the best position encountered by itself and its neighbors (This value is called Gbest).This modification can be represented by the concept of velocity

The current position can be modified by the following equation

Particle Swarm OptimizationThe following weight function is used:

Appropriate value ranges for C1 and C2 are 1 to 2.

Appropriate values for min and max are 0.4 and 0.9 respectively.

This method is applied by considering bus number and sizes of DG and Capacitor as variables.

Test System33-bus distribution system, contains 33 buses and 32 branches as shown in Figure. It is a radial system with a total load of 3.72 MW and 2.3 MVAr.

Results and DiscussionsTable I shows the total active power losses are 211 kW for 33-bus test distribution system for base case i.e without DG. TABLE ITest systemOptimum locationOptimum DG size (MW)Optimum Capacitor size (MVAr)Active Power loss (KW)Reactive Power loss (KVAr)% Reduction in lossWithout DG & Cap.With DG & Cap.Without DG & Cap.With DG & Cap.ActiveReactive33 busBus 62.49-------211111.17143.0381.6647.31%42.91%2.491.7221167.95143.0354.7967.79%61.69%Results and DiscussionsWhen optimum size of DG is placed at optimal location, then the power losses are reduced significantly.

But it violates the voltage limits.

Voltage profile of the system is improved by placing both DG and Capacitor.

Reduction in active power loss with DG is 47.31%.

Both DG and Capacitor are 67.79% for test system.Results and Discussions

The voltage profile of the test system is improved by placing both DG and Capacitor at optimal locations.Results and DiscussionsDG and Capacitor at different Locations:

SystemPSO Technique33 Bus SystemCasesBus No.CapacityLoss in (kW)DG (MW)Capacitor (MVAr)Same location62.49081.721367.95Different location62.482958.45301.2558When DG and capacitor are placed at the same location then the reduction in losses is 67.95 kW.

when both DG and capacitor are placed at different optimal locations then the reduction in losses are 58.45 kWOptimal Power FactorWhen DG and capacitor are placed at bus no.6, the reduction in losses is 67.95 kW, and at optimal power factor of 0.82 leading.

Power factor of the DG must be opposite to the power factor of bus load.

33-bus system has a lagging power factor load.

power factor of DG must be leading. Optimal Power FactorThe results obtained for the optimal placement of DG and Capacitor with optimal power factor has been compared with the results of fast analytical approach results [13].

SystemCOMPARISON OF OPTIMAL DG PLACEMENT RESULTS33 Bus SystemCasesBase Case Loss (kW)Bus No.DG CapacityOptimal p.f.Loss in (kW)DG (MW)Capacitor (MVAr)Proposed PSO21162.49081.72130.8267.95Fast Analytical [13]21163.0247 (MVA)0.8568.28Optimal Power FactorFigure shows the variation of power factor when DG and Capacitor are placed at bus no.6

Observed that total power losses are minimum when power factor of the system is 0.82 leading. Total power loss using differential evolutionNumber of population members NP = 40; Maximum number of iterations (generations) =200 ;

vv=voltage; Tloss=PL;F=(err+PL)

Tloss = 86.870565658454666 ConclusionOptimal placement of only DG can not reduces the losses too much.

Reactive power source is also required to reduce the losses significantly.

Reactive power source is also required to improve the voltage profile.

Optimal power factor of the combination also effect the reduction of line losses.

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