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Improvement of Power Quality of a Grid Connected Distributed System Using DSTATCOM 1. SHIVARAJ S, 2.RAKESH J, 3 PRAVEENA ANAJI 1. - U G Students, 2,3. - Assistant Professor Department of Electrical &Electronics, Jain Institute of Technology Davanagere-03 Abstract: Power quality is one of the major issues in the modern electrical power system the variation in the magnitude of voltage causes serious problem in the connected system. In order to solve this problem the modern way of mitigation is the use of static synchronous compensator (STATCOM). It is very difficult to incorporate the filter at the consumer premises as well as at the generator and transmission levels as the equipment gets seriously affected. Hence the best place of incorporative static synchronous compensator is at distribution grid. In this paper the distribution STATCOM is explained with its operation, modeling and a case study which is executed using MATLAB Simulink software and the results and analyzed using theoretical calculation and finally the STATCOM operation is verified. [1] INTRODUCTION: As the electrical system is continuously upgrading with the time there exist new problem with synchronization, transmission distribution etc., in order to meet the load demand we are inter connecting the tie-lines so that the power form different generating sources can be utilized. Hence when this type of synchronization is done there is a creation of problems of harmonics, voltage sag, voltage swell etc., Voltage sag and voltage swell are the two major problems which has got very dynamic effect on the power system if voltage supplied to the equipment is less than the rated it will not work or either it will work at very low efficiency and if the voltage supplied is above the rated windings get damaged. Hence in order to provide reliable uniform, power modern method of mitigation is use of STATCOM. A battery energy system is used to supply the reactive power which is connected shunt with capacitor bank. The STATCOMs are voltage source converter and this is powered by the battery bank. The entire system is connected shunt in distribution network so that whenever the voltage of the line crosses the set value the STATCOM circuit absorbs the active power and whenever the voltage of the line falls then the set value the STATCOM supplies the reactive power. [2] BLOCK DSTATCOM: DIAGRAM OF Figure shows the typical block diagram of STATCOM connected to distribution line. It mainly consists of the voltage source converter. That is , pulse width modulation circuit and capacitor bank, controller circuit as well as the distribution line. The block diagram shown below has three units with consisting resource unit, module unit and a control unit. shunt manner so that required power ratings can be obtained. [6] MODELING OF STATCOM: The theoretical computation of STATCOM is done based on the current ratings needed i.e. injection and absorption currents. As the electrical system mainly consists of inductive equipment the current lags the voltage and is shown in figure below, Figure: Block diagram of connected to distribution line. [3] VOLTAGE CONVERTER: STATCOM SOURCE Voltage source converters are the devices which modifies the voltage waveform i.e. these are power electronic device which are used to convert DC power to alternating power using pulse width modulation technique. IGBT/GTO are mainly used for this operation as IGBTs have fast response time it is mainly preferred. Fig: Phasor diagram Hence the output current can be given as, [4] CONTROLLER CIRCUIT: PI controller is used in the STATCOM circuit which produces an error signal on comparing with set values, 3 phase values are set i.e. Vdc for DC bus Vta, Vtb, Vtc for lines i.e. AC bus. The PI controllers are calibrated with suitable proportion and integral value so that accuracy in error calculation is made. [5] BESS SYSTEM: A capacitor bank with BESS (Battery Energy Storage System) is used which consists of array of batteries connected in series and Figure: Single line diagram of DGgrid interfaced system extra voltage needs to be removed from the system health point of view. Hence the DSTATCOM acts as an additional load so that the battery is charged. And in case of the less voltage then the limit the battery supplies the DC power which is inverted by VSC’s by pulse width modulation technique and hence reactive power is supplied into the grid. Figure: Schematic representation of DSTATCOM Figure: MATLAB model of DSTATCOM. [7] OPERATION DSTATCOM: OF DSTATCOM is basically shunt operated device which mainly operates in two modes one is injective mode and other is absorption mode. In the injective mode the reactive power is supplied into the grid and in absorption mode the active power is taken from the system i.e. if the magnitude of voltage crosses the limit there exists the condition of voltage swell. Under this condition the [8] SIMULATION OF DSTATCOM & ANALYSIS: The analysis of STATCOM is done by implementing a case study in MAT Lab Simulink model. Figure shows the simulated circuit in MAT Lab software and the outputs at different conditions. Transient response of DSTATCOM when connected to a weak supply system and transient responses of distribution system with DSTATCOM without battery for supply, these are the two cases which we consider while studying simulation results and the obtained waves are represented below, [10] REFERENCES: 1. Yash Pal, A. Swarup, and Bhim Singh, “A Review of Compensating Type Custom Power Devices for Power Quality Improvement” 2008 Joint International Conference on Power System Technology (POWERCON) and IEEE Power India Conference New Delhi, India. 2. Mahesh Singh and VaibhavTiwari, Figure (a) “Modeling analysis and solution of Power Quality Problems”,http://eeeic.org/proc/papers/50. pdf. 3. J. Barros, M. de Apraiz, and R. I. Diego, “Measurement of Subharmonics In Power Voltages”, Power Tech, IEEE Lausanne, Page(s): 1736 – 1740, 2007. 4. Sannino. A “Global power systems for sustainable development,” in IEEE General Meeting, Denver, CO, Jun.2004 Figure (b) [9] CONCLUSION: From this modeling and analysis we can conclude that the DSTATCOM is the best method of providing reliable constant power so that power quality problems are mitigated.