Elimination of Voltage Sag/Swell using Dynamic Voltage Restorer R.Kalaivani 1 K.Arunvishnu 2 M.G.Jakir Hussain 3 R.Lokeshwaran 4 M.

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1 International Journal for Research in Technological Studies Vol. 3, Issue 4, March 206 ISSN (online): Elimination of Voltage Sag/Swell using Dynamic Voltage Restorer R.Kalaiani K.runishnu 2 M.G.Jakir Hussain 3 R.Lokeshwaran 4 M.Rajkumaran 5 ssociate Professor 2,3,4,5 UG Student,2,3,4,5 Department of Electrical & Electronics Engineering,2,3,4,5 Info Institute of Engineering, Koilpalayam, Coimbatore6407, Tamilnadu, India bstract Voltage sag disturbances are the most frequently occurring Power Quality problems in the distribution system. This paper explains modelling and simulation of a dynamic oltage restorer as a oltage sag and swell mitigation deice in electrical power distribution networks. Dynamic Voltage Restorer (DVR) is proposed to handle deep oltage sags, swells and outages on a low oltage single phase residential distribution system. The dynamic oltage restorer with its excellent dynamic capabilities, when installed between the supply and a critical load feeder, can compensate for oltage sags/swells, restoring line oltage to its nominal alue within a few milliseconds and hence aoiding any power disruption to the sensitie load. Otherwise, it will operate as an Uninterruptable Power Supply across the sensitie load when disturbance occurs on the supply oltage. It is also designed to reduce the usage of utility power. series injection transformer is connected in series with the sensitie loads which restoring oltage sag and swell to a nominal oltage by protecting the sensitie load from damage. In this paper the technical aspect feasibility related to the use of dynamic oltage restorer (DVR) with series injection transformer are ealuated. The modelling of dynamic oltage restorer is carried out component wise and their performances are analysed using MTL software. The simulation result shows that the control technique is ery effectie and yields excellent compensation for oltage sag/swell Mitigation. The proposed system is alidated with the MTL simulation for experimental setup for Voltage sag /swell occurrence is connected to the load. nd simulation results are erified with the same output for experimental setup. Keywords Dynamic Voltage Restorer (DVR), Magnitude traction, Power Quality, Series injection transformer, Voltage compensation I. INTRODUCTION In the early days of power transmission oltage deiation occurs during load changes, power transfer limitation was obsered due to reactie power unbalances. Modern power systems are complex networks, where hundreds of generating stations and thousands of load centres are interconnected through long power transmission and distribution networks. The main concern of customer is the quality and reliability of power supply at arious load centres. Een though power generation in most welldeeloped countries is fairly reliable, the quality of supply is not. there are two major challenges that the modern power grid must deal with oltage fluctuations and short circuit faults. With wide use of nonlinear loads, the grid suffers from oltage fluctuation, oltage unbalance, and other power quality problems Power distribution system should ideally proide their customers an uninterrupted flow of energy with smooth sinusoidal oltage at the contracted magnitude and frequency. Howeer, in practice power system especially the distribution system, hae numerous nonlinear loads, which are significantly affect the quality of power supply. s a result, the purity of waeform of supply lost. This ends up producing many power quality problems such as oltage sag, oltage swell.. Voltage sag is a sudden reduction of utility supply oltage from90% to 0% of its nominal alue. On the other hand, oltage swell is a sudden rise of supply oltage from 0% to 80% of its nominal alue. typical duration of oltage sag and swell is 0 ms to minute. The oltage sags and swells often caused by starting of large induction motors, energizing a large capacitor bank and faults such as single line to ground fault, three phase to ground fault, double line to ground fault on the power distribution system t the same time, many power loads become more sensitie to these disturbances. To improe power quality, custom power deices are used. Dynamic Voltage Restoration (DVR) is a method and apparatus used to sustain, or restore, an operational electric load during sags, or spikes, in oltage supply. DVRs are a class of custom power deices for proiding reliable distribution power quality. They employ a series of oltage boost technology using solid state switches for compensating sags/swells. II. OJECTIVE Fast mitigation of power quality problems Power quality improement Voltage compensation against oltage disturbances such as oltage sag oltage swell Short Circuit Protection III. LOCK DIGRM OF PROPOSED METHOD Fig. : lock diagram Copyright IJRTS 37

2 2 c Elimination of Voltage Sag/Swell using Dynamic Voltage Restorer Figure illustrates the block diagram of proposed method. It consists of an c supply from distribution lines, step down transformer, Microcontroller, single phase inerter, series injection transformer and sensitie load. Supply oltage from distribution transformer i.e. 230 is stepped down to desire oltage with the help of tap changing transformer is fed into rectifier and then conerted into DC. The obtained DC oltage is maintained constant with the help of the oltage regulator applied to the microcontroller where the reference oltage and magnitude traction is programed, where the input oltage magnitude is compared with this reference oltage magnitude, when equal supply is directly connected to the load. In case oltage magnitude less than required oltage it will boost the required amount of oltage injected by means of phase to neutral injection in series injection transformer then it is connected to the sensitie load. If oltage magnitude is greater than required oltage, it reduces to the desired oltage and fed to the sensitie load with the help of neutral to phase current injection in series injection transformer. IV. SYSTEM CONFIGURTION The basic idea of a DVR is to inject the missing oltage cycles into the system through series injection transformer wheneer oltage sags are present in the system supply oltage. s a consequence, sag is unseen by the loads. During normal operation, the capacitor receies energy from the main supply source. When oltage dip or sags are detected, the capacitor deliers dc supply to the inerter. The inerter ensures that only the missing oltage is injected to the transformer. relatiely small capacitor is present on dc side of the PWM solid state inerter, and the oltage oer this capacitor is kept constant by exchanging energy with the energy storage reseroir. The required output oltage is obtained by using pulsewidth modulation switching pattern. C DC V S 2 g Goto Pulses Signal(s) Lf PWM Generator V. SIMULTION Cf REF ND Logical Operator reaker SOURCE VOLTGE CONTROL LOOP HEVY LOD Goto3 Discrete, Ts = 2e006 s. powergui Fig. 2: Simulation for DVR SOURCE/SG VOLTGE C LOD VOLTGE INJECTED VOLTGE 2 i LOD C Goto2 Fig. 3: Simulation output for oltage sag recoery by using DVR In aboe diagram Fig 2,3 are the circuit diagram, simulation output of a DVR respectiely The simulation is simulated by using MTL whole simulation will be kept under a discrete mode because to occur an instant output in a discrete manner. n input oltage of 230 rms is fed to the sensitie load when there is no interruption and sag occurs at 0.3ms to 0.45ms where the peak oltage is reduced till Vp = 200V. this is eliminated by generating waeform using pulse width modulation(pwm) generator and adding it with sag waeform with the help of Series injection Transformer so that it will compensates the losses occurs during oltage sag through which sensitie equipment are saed Vp= PeakPeak Voltage V pinj =Injected oltage V L =Load Voltage V L =Vp Vpinj () While sag occurs at t=0.30 ms to t=0.45ms Vp=400 V (2) V pinj= 400V (3) Substitute (2), (3) in () V L = =800V (4) SIMULTION PRMETERS Input oltage 230*.44V DC Source 2 V Load resistance 0 ohm Frequency 50Hz Isolation transfer : (250 Watt) Series injection transformer : (250 Watt) Inductie filter 38mH Capacitie filter 20uF Table : Parameters for DVR Copyright IJRTS 38

3 VI. SUSYSTEMCONTROL LOOP K SOURCE VOLTGE Gain Freq Vsmax Vd Vq hypot V(pu) wt Math sin_cos sinwt Function Sin_Cos Subsystem Discrete phase PLL REF Fig. 4: Circuit diagram for controller loop wt Constant sin Trigonometric Function fc/2 PI Discrete PI Controller del only when the difference in nominal waeform occurs which is injected to the source oltage with the help of series injection transformer to obtain constant load oltage to the sensitie load For Magnitude traction V source * Sin wt = V real (5) V source *cos wt = V img (6) V d =V real *sinwtv img *cos wt (7) V q =V real *coswtv img *sin wt (8) VII. HRDWRE IMPLEMENTTION Fig 6, a singlephase DVR is proposed to compensate oltage sag/swell and harmonics and limit downstream fault currents with a simple topology. lthough, the proposed topology is single phase, it can be extended to any nphase (such as threephase) system. The use of Custom Power Deice (CPD) is one of the most efficient methods to mitigate oltage sag or swell. Custom power deice is powerful tool based on semiconductor switches concept to protect sensitie load if there is a disturbance from power line. mong the seeral noel CPD, Dynamic Voltage Restorer (DVR) are now being established in industrial areas to mitigate oltage disturbances on sensitie loads. In our DVR concept propose the new technique to compensate oltage by using Magnitude traction or Magnitude estimation method. c supply is gien to the step down tap changing transformer. The output oltage from the step down tap changing transformer is compared with the reference oltage which is programed in the PIC. To correct the error between a measured process ariable and a desired set point, the PIC controller is used and controller is also used for magnitude traction of supply oltage. To decrease the error signal, it is compared with a reference signal to produce sine PWM pulses. This sine PWM pulse is generated only when the difference in oltage waeform occurs. The drier circuit consists of opto coupler, transistor and drier IC act as a drier for MOSFET to proide required pulses from the Microcontroller. Solidstate semiconductor deices with turn off capability are used in inerter circuits. VSI is energized by a stiff DC oltage supply of low impedance at the input. The output oltage is independent of load current. Fig. 5: Simulation output for controller unit From fig 4,5 shows the simulation output of control unit,control unit control the load oltage by magnitude traction or magnitude extraction method, where the real oltage is obtained from multiplication of source oltage and sinusoidal angle similarly imaginary oltage is obtained from multiplication of inersed source oltage and cosine angle from which Vd and Vq are calculated which fed to hypot where the oltage is compared with reference oltage and produce a nominal waeform in case sag occurs it will show the difference as shown in figure 5. Pulse Width Modulation (PWM) generator will generate sinusoidal pulse Fig. 6: Hardware implementation Copyright IJRTS 39

4 The nonlinear characteristics of semiconductor deices cause distorted waeforms associated with harmonics at the inerter output. To oercome this problem and proide high quality energy supply, filter unit is used. The output oltage from filter is gien to the series injection transformer. The series injection transformer is used to inject missing oltage to the load. If the input C oltage is need not to step down means we can directly use rectifier and it conerts C to DC. The DC supply is gien as input to inerter and the remaining processes are same. VIII. RESULTS Fig. 9: Normal Voltage When the input oltage mathe the required desired oltage. PIC sends signal to the drier and series injection transformer to connect the load without any changes Fig. 7: Voltage sag occurs Where green is the input oltage with sag, from our proposed method load oltage is matched with the help of series injection transformer and obtain the constant load oltage as in the aboe fig Fig. 0: Filter Output Fig 0, filter output which will injects the required amount of oltage to the series injection transformer to meet the load oltage when sag occurs it will induce the required oltage with the supply oltage, when swell occurs it will reduce the oltage to the desired leel Fig. 8: Voltage swell occurs When swell occurs our propoed method will reduce the input oltage to the required amount of load oltage and protecting the load from damage IX. CONCLUSION design and deelopment of Dynamic Voltage Restorer (DVR) for oltage Sag and Swell compensation for improing power quality is stimulated by using MTL. when compared with the existing method Where Fast Mitigation of oltage sag is achieed by mathematical modeling simulation done in MTL as mentioned in the graphs and the proposed method is capable to compensate the power quality problems like oltage sag and oltage swell within a milliseconds. This proposed method can be used in the distribution sides to protect the sensitie loads getting damage and increase its life time. Copyright IJRTS 40

5 REFERENCES [] Sandy K, Jaya Laxmi, Soni MP. Design of PI and fuzzy controller for dynamic oltage restorer (DVR). SRI Procedia 2 202;2: [2] oonchiam P, Mithulananthan N. Understanding of dynamic oltage restorers through MTL simulation. Thammasat Int J Sic Tech 2006;(3): 6. [3] ElTayyan. PV system behaior based on datasheet. J Electron De 20;9: [4] Elgendy M, Zahawi, tkinson DJ. ssessment of perturb and obsere MPPT algorithm implementation techniques for PV pumping applications. IEEE Trans Sustain Energy 202;3():2 33. [5] Hsieh YP, Chen JF, Liang TJ, Yang LS. Noel high setup DC DC conerter for distributed generation system. IEEE Trans Ind Electron 20;99.. [6] Nielsen JG, Newman M, Nielsan H, laabjerg F. Control and testing of a dynamic oltage restorer (DVR) at medium oltage leel. IEEE Trans Power Electron 2004;9(3): [7] R. Muralekrishnen ; P. Siakumar Improing the power quality performance for distributed power generation 222 March 202 [8] mit Meena, Shirazul Islam, Sandeep nand Department of Electrical Engineering,Indian Institute of Technology Kanpur Design and Control of Single Phase Dynamic July. 203 [9] Taighi Dept. of Electr. & Comput. Eng., Uni. of ritish Columbia, Vancouer,C, Canada H. bdollahzadeh ; J. Marti Fast response DVR control strategy design to compensate unbalanced oltage sags and swells in distribution systems 225 July 203 [0] Mahmoud Zadehbagheri¹, Rahim Ildarabadi*² and Majid aghaei nejad³ Faculty of Electrical, Department of Electrical Engineering, Hakim Sabzeari Uniersity, Modeling and Simulation of Dynamic Voltage Restorer for Voltage Sag/Swell Compensation in Power Distribution Networks Jul. 06, 205 Copyright IJRTS 4