Analysis and Simulation of DG Set Placing and Sizing in Grid Network

INTRODUCTION

Micro grid contains some natural energy sources.They may have solar cells, wind turbines, micro turbines, fuel cells and storage battery systems like fly-wheel, battery back-up. The definition of micro grid can be defined according to Department of Energy at U.S.A.: ―A group of interconnected loads and distributed energy resources (DER) with clearly defined electrical boundaries that acts as a single controllable entity with respect to the grid connect and disconnect from the grid to enable it to operate in both grid connected or island mode.‖ Here are reasons that why micro grids are so useful. Because they have some provision of alternative, and mostly renewable sources give more efficiency and less environmental problems than those conventional power generations. Further, they can reduce losses of transmitting power which makes micro grids more efficient than our standard power plants. It is possible to form a micro grid to match the necessities of the area it will be examining. Thus it can provide electricity for lighting as needed by some isolated areas. Then again, it can provide high quality; continue electricity needed by industries which use highly sensitive equipment and also for hospitals purpose. Various technologies are used for generation of power and storage units within or outside of a Micro grid, which are listed as below:-

Here micro grid contains loads, storage device, PV system, micro turbine, fuel cells. Micro grid is connected to utility grid via circuit breaker .Here micro grid supports the main grid when load demand is greater. Hence more load demand can be full filled byvarious sources within micro grid. And on other hand when climate changes, energystorage devices supply the power to maintain continuity. world for providing quality in ourlives and other elements for society‘s requirements. Conventional electrical energy sources are degradable and hence renewable energy sources are taking place by considering economic and environmental factors nowadays. It is to be said that the consumption of electrical power should be in limit, but the truth is there is always collective demand for this energy. Hence, the demand is to be fulfilled, by growing electricity generation capacity. Almost all the power generation takes place which uses coal, oil, natural gas, water or nuclear material as the main source of fuel. The problems facing by the further development of generation methods are based on any of this fuel. Water power generation is restricted sometimes due to areas, and funds of coal. The possible hazards of nuclear power have been involving military usage of nuclear waste things. Also, in order to maintain electrical power supply in many neighborhoods fusion reactors will be tolerated. To achieve the above mentioned goal, it is advisable to enhance in our management system that includes present fossil fuel resources, and use those with non-conventional resources like solar photovoltaic cells, wind energy systems etc. Because of good availability and efficiency that better than these sources, natural sources are also good substitutes for their working. Besides, they are lesser in costs. These sources also give power supply solutions for remote areas, which is outskirts of grid power supply. Hybrid models are so effective options for production of power in whole world. Many studies have been done on it and permanent houses more facilities in the systems. This thesis refers the possible concert valuation in the wind energy, solar photovoltaic panel, fuel cell stack and other hybrid energy system. Also in this solar, wind, Fc systems backup storage battery are designed, integrated and elevated to foresee the behaviour of the generation system.

Photovoltaic plants directly convert the instantaneous solar energy to electrical energy without using any fuel. The PV system generates electrical energy when exposed to sunlight by electromotive force which is generated by the absorption of ionizing radiation defined as photovoltaic effect.Such many advantages support solar photovoltaic plant as a future source of energy. But the only disadvantage is high initial cost for the development of such plants. Moreover, the solar energy source is also variable in nature and availability is at daytime only. However, the yearly electrical power output of Photovoltaic plant depends on different factors such as: • Availability of solar irradiation at the installed plant site. • Environmental condition surrounding the solar plant for e.g. presence of shading due to clouds. • Technical performance of plant components. A photovoltaic plant consists of PV panels, supporting structure to mount the panels on ground or building, power conditioning unit, possible storage system and other electrical switchboards and switch gears assembly with protection equipment and connection cables.

The Solar Plants are largely installed in two different ways (1) Standalone plants (2) Grid connected plants

Solar plants which are not connected to the grid and consist of storage system which allows the plant to supply power even when the sunlight is not available in proper amount or in dark. In such a plant the generated power is directly stored in batteries as DC supply and if AC supply is required then an inverter is needed. Such type installation is more beneficial where the grid network is not available as it can easily replace the generator for generation.

Grid connected Plants are permanently connected to grid and takes power during insufficient solar power generation to satisfy the requirement of consumer. And at the time of low consumer load the excess of power generated by the solar power plant is given to the grid. The energy generated near the load have higher value the conventional power from grid which is transmitted from longer distance. Also, the power generated during peak hours by the solar plant reduce the need of grid

The PV array is build-up of solar cell as shown in Fig.3.3. The characteristic of a solar array is given by following equation. The main equation of output module. Where, V = voltage across solar panel terminal. I = current across solar panel terminal. k = the Boltzmann constant. a = ideality factor T = cell working temperature ki = shore circuit current temperature coefficient

In order find the optimum location for placing DG units a number of methods aredeveloped. In this thesis, a technique based voltage stability index (VSI) has been developed for optimal placing of DG units. A node with minimum value of VSI is considered as the optimum location for placement of DG. In order to obtain optimal DG size, below steps should be followed: 1) A node with minimum VSI should be found first and then he DG is placed at that node. 2) Assuming Distributed generation power factor as constant, size should be varied in constant steps from a minimum value to a maximum value (feeder loading capacity) till minimum losses are obtained 3) The size of DG which produces minimum loss is considered as optimal size. The system considered here is an IEEE-33 bus system. It has an voltage of 12.66 kV and total real power demand of 3.715 MW and reactive power demand 2.3 MVAr. In the first case load flow without DG is analysed and bus voltages magnitudes and total power loss of the network in RDS are computed. VSI at various buses is also calculated. From the analysis, we found that the bus 18 is having lowest VSI value of 0.66721. Hence, bus 18 is optimal location for placing DG. For analysis, the following two cases are considered: Case 1: DG operating at 0.9 power factor lagging Case 2: DG operating at unity power factor that power losses are non-linearly varying with capacity of generator. First the power losses are decreased up to some minimum values and then start increasing with DG capacity increment. Hence from the test results, it is observed that in the base case without DG, total respective real and reactive power losses are 210.99 kW and 143.03 kVAr. Whereas the losses after placing a DG with 1 MVA at a lagging power factor of 0.9 produces more loss reduction when compared with the DG size of 0.85 MVA at unity power factor. Hence, optimal placing and sizing of DG reflects the power loss reduction in radial distribution system. We can also note that substation capacity release is more for case 1 compared to case 2. As DG injects real and reactive power to the load centers locally, it helps in improving the bus voltages and also reduce the losses at the load side. Comparison of the voltage variation for different cases viz. base case (without DG), Case 1 and Case 2 proves that improvement in voltage for case 1 is more compared to case 2. Similarly analysis is done for IEEE-69 bus network. It has a voltage of 12.66 kV and total real power demand of 3.802 MW and reactive power demand 2.694 MVAr. From the analysis, we found that the bus 65 is having lowest VSI value of 0.68345. Hence, bus 65 is the optimal location for placing DG.

Optimization technique is used to find the best solution for any givencircumstances. For example, in a company if it is required to improve its rating, technological and managerial plans have to be taken many times. Here, the goal of the plans is to either maximize the profits or to minimize the spending effort. Optimization is referred as both minimizing and maximizing the tasks. Since the minimization of any function is same as maximizing its additive inverse, the terminology minimization and optimization can be used interchangeably. Because of this reason, optimization became very important in many fields. Basically, in order to solve the optimization problems, PSO algorithm is inspired by the animal‘s activity. In PSO, swarm means population; particle represents each member of the population. Each particle searches through the entire space by randomly moving in different directions and remembers the previous best solutions of that particle and also positions of its neighbor particles. Particles of a swarm adjust their position and velocity dynamically by communicating best positions of all the particles with each other. In this way, finally all particles in the swarm try to move towards better positions until the swarm reaches an optimal solution Thus, due to its easy implementation and its ability to obtain fast convergence, PSO technique is becoming very popular. Moreover PSO uses only basic mathematics and it does not involve any derivative or gradient information.

Total Real Power Loading: 3715 kW Total Reactive Power Loading: 2300 kVAr

Total Real Power Loss: 210.99 kW Corresponding Bus No. : 18 Table 6.2: IEEE 33 Bus Voltage Stability Index without DG CASE-1: Here DG will inject only real power

Total Real Power Loss: 145.89 kW Total Reactive Power Loss: 100.31kVAr Total Loss after DG placement: 246.20 kVA Size of DG is: 0.8061 MVA

Total Real Power Loss: 123.72 kW Total Reactive Power Loss: 87.027kVAr Total kVA Loss after DG placement: 210.99 kVA Size of DG is: 0.8489+j0.4914 MVA

evaluate the performance of IGSA, GSA and PSO in determining the optimal placement and sizing of PVDG in a distribution system. IGSA is an improved heuristic optimization technique that has several advantages such as adaptive learning rate, better execution and fast convergence in finding the optimal solution. The objective function of the optimization considers total real power loss, average voltage deviation, average. All of the cases plotted the improvement values of the fitness function as the number of iteration increases. This paper also shows that it is better to search for an optimum locations and sizes of PVDG in the system, instead of fixing the locations based on a certain issue such as the voltage collapse point of view.

REFERENCES

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Department of Mechanical Engineering, SS College of Engineering, Rajasthan Technical University, Kota, India