FUTO Journl Series (FUTOJNLS), 2015, VOL. 1, Issue 1 50 MODELING ND SIMULTION OF DYNMI VOLTGE RESTORER FOR POWER QULITY IMPROVEMENT bstrct Uzoechi LO nd Obikor M Deprtment of Electricl/Electronic Engineering, Federl University of Technology, Owerri, Nigeri * lzrus.uzoechi@futo.edu.ng In this pper, the power qulity ws improved by modeling nd simultion of Dynmic Voltge Restorer (DVR). DVR is power electronic device tht cn protect sensitive lods from vrious disturbnces in the power supply. This pper modeled nd simulted the Dynmic Voltge Restorer to mitigte three mjor power qulity problems nmely; voltge sg, voltge swell nd hrmonic distortion for power qulity improvement. To solve these problems, ustom Power Devices re used nd one of these devices is DVR which is the most effective nd efficient custom power devices used in distribution network for power qulity improvement. DVR is series compensting device tht injects voltge of desired mgnitude nd frequency in series nd in synchronism with the distribution supply voltge to restore the lod voltge to desired voltge level. This is implemented using MTL/Simulink/SimPowerSystem. The DVR improved the voltge to bout 95-98%. Keywords Dynmic Voltge Restorer (DVR), Voltge sg, Voltge swell, Hrmonics, Power qulity, ustom Power Device. 1. INTRODUTION The qulity of power output delivered from the utility to the consumers hs become mjor concern in the restructured power system. Therefore, power qulity (PQ) is mjor constrint nd vitl mesure of n electricl power system. The importnce of improved power qulity hs risen very considerbly over the lst two decdes due to remrkble increse in the number of modern industril equipment which re mostly bsed on electronic devices. They include progrmmble logic controllers nd other electronic components tht re very sensitive to power disturbnce or problems which, if not controlled nd corrected, cn cuse very big hrm to them (Llith nd Vindhy, 2013). Idelly, the power generted t the power sttion is purely sinusoidl in nture nd of high power qulity where the purely sinusoidl current wveform is in phse with the purely sinusoidl voltge wveform nd t mgnitude nd frequency given by the ntionl stndrds or system specifiction (Kvith et l, 2013) nd (Roncero-Snchez et l, 2009). ut due to the presence of connected non-liner lods, unblnced lods, power system fults nd power electronic converters in the power system, the power wveform is distorted nd becomes nonsinusoidl thereby leding to poor power qulity problems such s voltge sg, voltge swell, surge, hrmonic distortion, overvoltge, undervoltge, flickers nd blckout (Reddy nd nyneyulu, 2001) nd (fonson et l, 2010). onsequently, these power qulity problems cn led to increse in power losses, power system collpse, mlfunction, dt loss nd dmge of equipment. There is need to protect our electricl nd electronic equipment from mlfunctioning or dmge s result of presence of power qulity problems in our power supply system. This cn be chieved by improving the qulity of power supply being delivered to the consumers which cn be implemented by using Power Improvement devices. One of them is the Dynmic Voltge Restorer (DVR) nd by virtue of its fst, dynmic response, is the most effective nd efficient (Mllel et l, 2005). The DVR is series connected device which by voltge injection cn control the lod voltge (Nielsen, 2002). The three mjor opertions of
FUTO Journl Series (FUTOJNLS), 2015, VOL. 1, Issue 1 51 DVR re the compenstion for voltge sg, voltge swell, nd hrmonic distortion. Erlier, power qulity improvement strted on the genertion nd trnsmission system where Flexible Trnsmission System (FTS) devices were used which include STTOM Sttic Synchronous ompenstor, SSS Sttic Synchronous Series ompenstor, IPF Interline Power Flow ontroller, UPF Unified Power Flow ontroller (Pndey, 2013). ut these FTS devices were for trnsmission system only. However, in the distribution system tody, it is mjor focus for power qulity improvement, nd lso due to the disdvntges ttched to FTS devices such s fixed compenstion, bulkiness, nd electromgnetic interference. These urged the power system nd power electronic engineers to think of developing n djustble nd dynmic solution nd led to the modifiction of the FTS devices for use in the distribution system so tht power qulity cn be further improved. These modified devices re clled ustom Power Devices which include Distributed Sttic ompenstors (DSTTOM), Dynmic Voltge Restorer (DVR), Uninterruptble Power Supply (UPS), Sttic Vr ompenstor (SV). mong these devices, DVR is the most effective nd efficient custom power device becuse of its low cost, smller size, fst response towrds the disturbnce, nd most importntly its dynmism mkes it possible to inject only the quntity or mount of voltge required t prticulr time (Nielsen, 2002). The DVR is still modern device which insertion nd use in the grid system is still rre (El-Gmm et l, 2011). DVR ws treted in (Nguyen nd Sh, 2004) nd (Jen et l, 2012) where the nlysis ws bsed on voltge sg mitigtion only. They did not provide solution for protection ginst other power qulity problems like voltge swell, hrmonic distortion. lso, the work in (Tumy et l, 2011) delt with DVR for rectifying the problem of voltge sg only s they considered voltge sg to be the most severe since sensitive lods re very susceptible to temporry chnges in voltge. In the pper (enchib nd Ferdi, 2008), DVR ws designed for hhrmonics distortion compenstion, nd in this work, voltge sg nd swell were not treted or considered. lso, in the work in (Llith nd Vindhy, 2013), controller bsed on repetitive control for DVR to compenste voltge sg, hrmonic voltge nd voltge imblnce ws discussed. The reserch in (Vivek nd Srividhy, 2013) ws imed t getting good qulity of power nd minimizing the power triff chieved by implementing hybrid power genertion system but focused on the vrious methods of power qulity improvement techniques in hybrid power system However, observtion showed tht most of these forementioned works provided limited informtion bout the comprehensive opertion nd detiled description of the modelling, design, control nd simultion spects. This pper nlyses power qulity nd its ssocited problems, nd subsequently presents concise, comprehensive informtion on the descriptive modeling, simultion, nd opertion of DVR for the mitigtion of voltge sg, voltge swell nd hrmonic distortion in the distribution power system. 1.1 POWER QULITY ND ITS PROLEMS Power Qulity problems involve vrition in voltge mgnitude, vrition in frequency, nd vrition in wveform shpe (hrmonics). The problems of Power Qulity cn be ctegorized s: ii. Short-durtion power qulity disturbnces which include voltge sg, voltge swell, nd voltge trnsient (impulse/surge). iii. Long-durtion power qulity disturbnces which include overvoltge nd undervoltge. iv. ontinuous nd stedy-stte power qulity disturbnce which include hrmonic, flickers, nd voltge imblnce (enchib nd Fredi, 2008b).
FUTO Journl Series (FUTOJNLS), 2015, VOL. 1, Issue 1 52 1.1.1 Voltge Sg ccording to IEEE defined stndrd (IEEE Std. 1159-1995) (IEEE Stndrd ord, 1995), Voltge Sg is defined s decrese in rms voltge from 0.9 to 0.1 per unit (pu) for durtion of 0.5 cycle of power frequency to 1 minute. lso, Voltge sg cn be defined s short reduction in rms voltge mgnitude from 90% to 10% of nominl voltge for time greter thn 0.5cycle of power frequency but less thn or equl to 1minutes (Pnte nd Kristin, 2008). The chrcteriztion of voltge sg is relted with the mgnitude of remining voltge during sg nd the durtion of sg s shown in Fig.1.1. Fig.1.1 Voltge wveform during voltge sg (enchib nd Ferdi, 2008b) Voltge Sg cn be clssified bsed on the sg mgnitude nd durtion. ccording to IEEE std. 1159-1995 (IEEE Stndrd ord, 1995, they re clssified s shown in the Tble 1.1. Tble 1.1: Voltge sg durtion nd Type of Sg Durtion Mgnitude Instntneous 0.5 30 cycles 0.1 0.90 pu Momentry 30 cycles 3s 0.1 0.90 pu up of hevy induction motor of lrge current rting, long distnce trnsmission nd distribution, nd unblnce lod on three phse system (Llith nd Vindhy, 2013) nd (IEEE Stndrd ord, 1995. lso, the effects of voltge sg cn be observed in the mlfunction or dmge of sensitive equipment, reduction in energy trnsfer of electric motors, industril processes being brought to stndstill, power system filure or collpse, overheting of electricl equipment, nd decrese in economy (Llith nd Vindhy, 2013) nd (Pndey, 2013). Temporry 3s 1 min 0.1 0.90 pu Voltge sg my be cused by short-circuit fult nd erth fult in the power network, strting 1.1.2 Voltge Swell ccording to IEEE defined stndrd (IEEE Std. 1159-1995) (IEEE Stndrd ord, 1995, Voltge Swell is defined s increse in r.m.s. voltge from 1.1 to 1.9 per unit (pu) for durtion
FUTO Journl Series (FUTOJNLS), 2015, VOL. 1, Issue 1 53 of 0.5 cycle of power frequency to 1 minute. lso, Voltge sg cn be defined s short increment in r.m.s. voltge mgnitude from 110% to 190% of nominl voltge for time greter thn 0.5cycle of power frequency but less thn or equl to 1 minutes (Pnte nd Kristin, 2008). Voltge swell is s shown in Fig.1.2. Fig.1.3 Digrmmticl representtions of hrmonic distortion (fonson et l, 2010) Fig. 1.2 Voltge wveform during voltge swell (enchib nd Fredi, 2008b). 1.1.3 Hrmonic Distortion This is power qulity problem cused by nonliner equipment s result of their distortion of the power wveform (Llith nd Vindhy, 2013). The current of these non-liner lods s shown in Fig. 1.3 contins hrmonics which produces non-liner voltge drop in the line impednce which distorts the lod voltge (fonson et l, 2010). The presence of hrmonics in power lines cuses greter power losses in the distribution system, interference problem in the communiction system, overheting nd pulsing torque in rotting mchinery, nd opertion filure of electronic equipment (fonson et l, 2010). 2. DYNMI VOLTGE RESTORER DVR is power electronic device tht cn protect sensitive lods from vrious disturbnces in the power supply. It is series compensting interfced equipment between the utility nd customer connected in series between supply nd lod to mitigte three (3) mjor power qulity problems which re voltge sg, voltge swell nd hrmonic distortion (Mllel et l, 2005). There re numerous resons why DVR is preferred over other devices (Hque, 2011). lthough, SV predomintes the DVR but the ltter is still preferred becuse the SV hs no bility to control ctive power flow. DVR is smller in size, power efficient nd less expensive too. n dvnced DVR cn be chieved by integrting present DVR with ctive Power Filter(PF) in other to dditionlly include filtering of hrmonics s result of non-liner lods in system. Fig. 2.1 shows the plcement of DVR in the distribution system.
FUTO Journl Series (FUTOJNLS), 2015, VOL. 1, Issue 1 54 Fig.2.1 Typicl DVR in Distribution System with sensitive Lod (Kvith et l, 2013) 2.1 sic omponent nd onfigurtion Of DVR The generl configurtion of DVR consists of the energy storge unit, inverter unit, control unit, filter unit, series injection trnsformer unit, D chrging unit, nd protection unit s shown in Fig.2.2. Fig. 2.2 Different modules tht mke up typicl DVR (Tumy et l, 2011) The min function of these energy storge units is to provide the desired rel power during voltge sg. Vrious devices such s Led cid btteries, Superconducting Mgnetic Energy storge (SMES) nd Super-pcitors cn be used s energy storge devices. The mount of ctive power generted by the energy storge device is key fctor, s it decides the compenstion bility of DVR (Li et l, 2001). The voltge source inverter (VSI) converts this D voltge into n voltge. In order to boost the mgnitude of voltge during sg in DVR power circuit, step up voltge injection trnsformer is used. Thus VSI with low voltge rting is sufficient (Li et l, 2001). Generlly, Pulse-Width Modulted Voltge Source Inverter (PWMVSI) is used. To convert the inverted PWM pulse wveform into sinusoidl wveform, low pss pssive filters re used. In order to chieve this, it is necessry to eliminte the higher order hrmonic
FUTO Journl Series (FUTOJNLS), 2015, VOL. 1, Issue 1 55 components during D to conversion in VSI which will lso distort the compensted output voltge. We cn void higher order hrmonics from pssing through the voltge trnsformer by plcing the filters in the inverter side. Thus it lso reduces the stress on the injection trnsformer (Li et l, 2001). If there is fult current due to fult in the downstrem, it will flow through the inverter. In order to protect the inverter, y-pss switch is used (Li et l, 2001). The three phse injection trnsformer is used to inject the missing voltge to the system. lso, the trnsformer serves the purpose of isolting the DVR from the power system. The chrging circuit hs two min tsks. They re to chrge the energy source fter sg compenstion event nd to mintin D link voltge t the nominl dc link voltge 2.2 Opertion Mode Of Dynmic Voltge Restorer Generlly, the DVR is ctegorized into threeopertion modes which re: injection mode, stndby mode nd protection mode (Nguyen nd Sh, 2004). The DVR goes into injection mode s soon s power qulity problem is detected. In this mode, the three single phse c voltges re injected with compensting voltges in series with required mgnitude, phse nd wveform for proper compenstion. In stndby mode (norml stedy stte condition), the DVR my either go into short circuit opertion or inject smll voltge to compenste the voltge drop on trnsformer rectnce or losses. If over current on the lod side exceeds permissible limit due to short circuit on the lod or lrge in-rush current, the DVR will switch to protection mode by being isolted from the system using the by-pss switch which removes the DVR from the system by supplying nother pth of current 2.3 DVR Topology Different topologies of DVR re discussed below. 1. Energy System Topology During voltge sg, the DVR injects voltges nd thereby restores the supply voltges. In this phse, the DVR exchnges ctive nd rective power with the surrounding system. If ctive power is supplied to the lod by the DVR, it needs source for the energy. Two concepts re here considered, one concept uses stored energy nd the other concept uses no significnt energy storge. 2. ompenstion Techniques There re three compenstion strtegies tht re normlly used for sg compenstion (hoi et l, 2005) nd (Wng nd hoi, 2008). They re the pre-sg compenstion, in-phse compenstion, nd the minimum energy injection compenstion technique. In pre-sg compenstion, the DVR compenstes for both the mgnitude nd ngle while for in-phse compenstion, compenstion for voltge mgnitude only is required nd no phse compenstion is required. The minimum energy injection compenstion depends on mximizing the ctive power supplied by the network or keeping the pprent power constnt while decresing the network rective power. : 3. Sg Detection Techniques voltge sg detection technique detects the occurrence of the sg, the strt point, the end point, sg depth (mgnitude to be restored) nd phse shift. ommon voltge sg detection techniques re the pek vlue method, root men squre (r.m.s.) method, Fourier Trnsform (FT) method, nd the spce vector method (Fitzer et l, 2004) nd (e et l, 2010). i. Pek Vlue Method The simplest method of monitoring the supply is to monitor the pek, or mplitude, of the supply voltge, then compring it with reference. controller could be set to recognize if there is difference greter thn specified vlue (10%) nd switch in the inverter. ii. Root Men Squre (rms) Method The strt time of the sg cn be defined s the first point of Vrms when drops below 0.9 pu. To find the end time of the sg, serch for n intervl where Vrms drops below 0.9 pu for t lest hlf cycle. The recovery time is then chosen s the first point in this intervl. iii. Fourier Trnsform (FT) The FT is chieved through orthogonl decomposition of power system signl. Generlly, trigonometriclly orthogonl function set or exponentil orthogonl function set is utilized. y pplying FT to ech supply phse, it is possible to obtin the mgnitude nd phse of ech of the
FUTO Journl Series (FUTOJNLS), 2015, VOL. 1, Issue 1 56 frequency components of the supply wveform. For prcticl digitl implementtion, Windowed Fst Fourier Trnsform (WFFT) is used, which cn esily be implemented in rel time control system. iv. Spce Vector Method The three phse voltges V bc re trnsformed into two dimension voltge V dq, which in turn cn be trnsferred into mgnitude nd ngle. ny devition in ny quntity revels the occurrence of n event. ompring these quntities with reference ones will quntify the disturbnce in the dq-frme, which hd to be trnsformed bck to the bc frme. This method hs no time dely, yet requires complex controller. 3. METHODOLOGY 3.1 Modeling In order to understnd nd nlyze the ctul behviour nd opertion of Dynmic Voltge Restorer, prototype of this DVR needs to be modeled nd simulted. Therefore, this section hs to do with the modeling nd simultion of this DVR in MTL/Simulink/SimPowerSystem environment. The block digrm which shows the systemic opertion of DVR is shown in Fig. 3.1. Spce Vector Fig. 3.1 lock digrm of component units of DVR 3.2 sic Principle of Opertion of DVR The DVR is connected in series between the supply system nd the lod. nd this DVR is minly mde up of seven bsic units which re: Energy Storge Unit, Inverter Unit, ontrol system Unit, Filter Unit, Series Injection Trnsformer Unit, Protection Unit nd the D hrging Unit. The control system unit which hs controller, monitors nd mesures the mgnitude of the supply voltge nd compres it with reference voltge which will subsequently control nd determine the rnge of opertion of the DVR. So, when there is voltge drop, or voltge rise (s result of voltge sg or voltge swell respectively) in the supply system, the controller mesures the voltge nd compres it with reference voltge nd consequently genertes n error signl (voltge difference) which will then be used s modulting signl to modulte the crrier wve of the inverter using Pulse Width Modultion (PWM) scheme. This modultion of the crrier wve signl of the inverter will then determine the mount nd kind (whether positive or negtive voltge for voltge sg or voltge swell respectively) of voltge the inverter will generte from the energy storge unit. The inverter ctully genertes the rective power needed by itself while it genertes the ctive power by D- energy conversion from the energy storge system. Then, the voltge is pssed
FUTO Journl Series (FUTOJNLS), 2015, VOL. 1, Issue 1 57 through the shunt filter to eliminte the hrmonic generted by the inverter. The filtered voltge is injected in series nd synchronism to the supply system by the injection trnsformer. The series injected voltge will now be dded to the supply voltge to restore the proper or desired mgnitude of the lod voltge. lcultion For DVR Voltge Vlue Z S V supply ZDVR VDVR Fig. 3.2 Equivlent circuit digrm of DVR The system impednce Z S s shown in Fig.3.2 depends on the fult level of the lod bus. When the system voltge (V Supply ) drops, the DVR injects series voltge V DVR through the injection trnsformer so tht the desired lod voltge mgnitude V L cn be mintined. The series injected voltge of the DVR cn be written s: V L Lod (3.1) The lod current I L is given by, where P L = Lod rel power Q L = Lod rective power (3.3) 3.3 Modeling of ontrol System Unit control system is implemented in softwre for control nd protection of the DVR s shown in Fig.11. To detect voltge sg, the voltge is continuously mesured nd Phse Locked Loop (PLL) is implemented to detect the phse nd ngulr position of the three-phsed supply voltge. V R + - V IN PI ONTRO- LLER Output of PI ONTRO- LLER Fig.3.3 Schemtic of typicl PI controller fter mesuring the supply voltge nd subsequent implementtion of phse locked loop, spce vector control will be pplied to the DVR, hence the voltges will be trnsformed in to spce vector representtion: V reference = Desired supply voltge Desired Supply Voltge = Desired lod voltge + line drop where V sg = voltge sg V L = Lod voltge Z S = System impednce I L = Lod current V supply = Supply voltge (3.2) (3.4) The spce vectors re trnsformed in to rotting d-q reference frme ccording to eqution below. (3.5) voltge sg is detected by mesuring the error between the dq-voltge of the supply nd the reference vlues: ( ) (3.6)
+ - g FUTO Journl Series (FUTOJNLS), 2015, VOL. 1, Issue 1 58 The d-reference component is set to rted voltge nd the q-reference component is set to zero. ut Voltges cn be trnsformed directly to d-q rotting reference frme s shown below. (3.8) lso, n d-q voltges cn be converted to positive sequence, V 1, negtive sequence,v 2, nd zero sequence voltges s shown below. (3.7) lso, d-q rotting reference frme cn be trnsformed to s follows: where phse ngle =. (3.9), complex, lso The hrdwre model of control system is shown in Fig.3.4. Vbc_pu3 Mg Phse bc Vbc b c V-I Mesurement1 Discrete 3-phse Sequence nlyzer (Fundmentl)3 Scope3 Scope Freq Sin_os wt Discrete Virtul PLL bc sin_cos dq0 bc_to_dq0 Trnsformtion 415 Reference Voltge PID(s) PID ontroller dq0 sin_cos bc dq0_to_bc Trnsformtion Signl(s) Pulses PWM Genertor Universl ridge Inverter Fig. 3.4 Typicl model of the control system unit Models of other units tht mke up the DVR. The model of the inverter unit is s shown in Fig. 3.5.
FUTO Journl Series (FUTOJNLS), 2015, VOL. 1, Issue 1 59 g + - Fig. 3.5 Inverter model Universl ridge Inverter1 Fig. 3.6 The energy source model The model for the injection unit is shown in Fig.3.7. lso, the model for energy source unit is shown in Fig. 3.6, mde up of bttery nd Dlink. Fig. 3.7 Injection trnsformer unit model The model for filter unit is shown in Fig.3.8, mde up of cpcitor nd inductor. 3.4 omplete MTL/SIMULINK Model of DVR The MTL/Simulink models of the different components tht mke up the DVR re ssembled to form the complete set of DVR s shown in Fig. 3.9. Fig.3.8 Filter unit model Hrmonic Filter
FUTO Journl Series (FUTOJNLS), 2015, VOL. 1, Issue 1 60 4. SIMULTION, RESULT ND DISUSSION fter modeling, the simultion ws done using MTL/Simulink/SimPowerSystem crried out on the hrdwre model of the Dynmic Voltge Restorer. Different operting conditions on the respective cses were ssumed s follows: 1) when there is no fulty condition without DVR 2) when there is short-circuit fulty condition without DVR 3) when there is short-circuit fulty condition with DVR. These cse scenrios cpture power qulity issues like voltge sg, voltge swell, nd hrmonic problems. The output of the hrdwre simultions hs to do with the results of the different three phse voltge mgnitude wveforms nd its positive sequence mgnitude, ll in per unit, cross the lod obtined from the simultion of modeled DVR nd its opertions re presented ccording to the vrious cses. SE 1: When there is no fulty condition nd without DVR opertion. Fig.4.1 shows the resulting wveform of supply tht hs no fult nd without DVR opertion. This indicte tht good qulity supply should be purely sinusoidl nd should mintin constnt mgnitude cross the lod s shown. Fig. 4.1 Voltge t lod point without DVR nd fult
+ - g 1+ 1 1+ 1 1+ 1 2+ 2 2+ 2 2+ 2 FUTO Journl Series (FUTOJNLS), 2015, VOL. 1, Issue 1 61 Vbc b N Progrmmble Voltge Source1 Discrete, Ts = 5e-005 s. powergui Source impednce 100 MV short circuit level Fult b b Trnsformer (Two Windings)1 c Trnsformer (Two Windings) c Vbc b c V-I Mesurement4 Series RL Lod bc Mg Phse Discrete 3-phse Sequence nlyzer (Fundmentl)1 reker Vbc_pu1 reker1 V-I Mesurement2 c reker2 Mg bc Phse Discrete 3-phse Sequence nlyzer (Fundmentl) Vbc b V-I Mesurement c Vbc_pu Mg bc Phse Discrete 3-phse Sequence nlyzer (Fundmentl)4 Vbc_pu4 Three- Series RL Vbc_pu3 Mg Vbc b c V-I Mesurement1 Trnsformer Fig.3.9 bc omplete MTL/Simulink/SimPowerSystem Model of DVR. Phse 12 Terminls1 Three-Ph Hrmonic F Discrete 3-phse Sequence nlyzer (Fundmentl)3 Freq Sin_os wt Discrete Virtul PLL bc sin_cos dq0 bc_to_dq0 Trnsformtion Scope3 415 Reference Voltge PID(s) PID ontroller dq0 sin_cos bc dq0_to_bc Trnsformtion Scope Series R rnch1 Signl(s) Pulses PWM Genertor b c reker1 Universl ridge Inverter Hrmonic Filter2 Vbc b c V-I Mesurement5 Mg bc Phse Discrete 3-phse Sequence nlyzer (Fundmentl)2 Vbc_pu2 D Voltge Source D cpcitor link SE 2: When there is fulty condition of voltge sg nd without DVR opertion.
FUTO Journl Series (FUTOJNLS), 2015, VOL. 1, Issue 1 62 Fig.4.2 Voltge t lod point with sg nd without DVR In Fig.4.2, the result of three-phse voltge mgnitude wveform under fulty condition of voltge sg (40% or 0.4 reduction) which cuses voltge drop t the time rnge of 0.2-0.3s is shown. nd since there is bsence of DVR, the voltge drop will not be compensted for. SE 3: When there is fulty condition of voltge sg nd with DVR in opertion Fig. 4.3 Voltge response of the test system with sg nd DVR Fig.4.3 shows the result of three-phse voltge mgnitude wveform under fulty condition of voltge sg (40% or 0.4 reduction) which cuses voltge drop t the time rnge of 0.2-0.3s. However, with the presence of DVR, it will respond immeditely to compenste the voltge drop by injecting positive voltge in series with the line voltge to restore the lod voltge to bout 95-98% of its nominl vlue.
FUTO Journl Series (FUTOJNLS), 2015, VOL. 1, Issue 1 63 SE 4: When there is fulty condition of voltge swell nd without DVR opertion. Fig.4.4 Voltge t lod point with swell nd without DVR The result shown in Fig.4.4 is the three-phse voltge mgnitude wveform under fulty condition of voltge swell (40% or 0.4 increment) which cuses voltge rise t the time rnge of 0.2-0.3s. nd since there is bsence of DVR, the voltge rise will not be compensted for. SE 5: When there is fulty condition of voltge swell nd with DVR in opertion. Fig. 4.5 Voltge response of test system with swell nd DVR Fig.4.5 is the result of three-phse voltge mgnitude wveform under fulty condition of voltge swell (40% or 0.4 increment) which cuses voltge swell t the time rnge of 0.2-0.3s. nd,
FUTO Journl Series (FUTOJNLS), 2015, VOL. 1, Issue 1 64 since there is present of DVR, it will rect immeditely to compenste the voltge swell by injecting negtive voltge in series with the line voltge to restore the lod voltge to bout 95-98% of its nominl vlue. SE 6: Non-liner lod with DVR opertion The effect of filter in response to hrmonic distortion being introduced by non-liner lods is shown in Fig.4.6. Fig. 4.6 Opertion of DVR filter for mitigtion of hrmonic distortion. The first grph (1), shows the distortion effect on supply current by hrmonics being generted by non-liner lod. ut, in the presence of DVR Filter, it will filter out the hrmonics nd restore the supply current bck to its originl sinusoidl wveform s shown in second grph (2). 5. ONLUSION Power Qulity hs been key fctor in the power system trnsmission nd distribution. Power qulity problems such s voltge sg, voltge swell nd hrmonic distortion hve hd dverse effects on industril equipment, power system structures, nd economy t lrge. Therefore, in quest to mitigte these problems, custom power device, Dynmic Voltge Restorer (DVR), hs been proposed for the mitigtion of these power qulity problems Furthermore, from the nlysis of the results obtined from the simultion of the modeled DVR using MTL/Simulink/SimPowerSystem in this pper DVR opertes to restore the desired lod voltge mgnitude to bout 95-98%, therefore, it hs been proven stisfctory tht DVR cn be used to provide cceptble solution to power qulity problems of voltge sg, voltge swell nd hrmonic distortion. lso, becuse of the fst response, smll size, nd dynmism of this device, it is the most efficient nd effective custom power device for power qulity improvement. REFERENES fonson, J., Ribeiro d Silv, H. & Mrthins, J. (2010) ctive Filter for Power Qulity Improvement. IEEE Porto PowerTech [Online], 10(13). 1-8 e,., Jeong, J., Lee, J. nd Hn,. (2010) Novel Sg Detection Method for Line- Interctive Dynmic Voltge Restorer. IEEE Trnsction on Power Delivery. 25(2). 1210-1211. enchib,. & Ferdi,. (2008) Voltge Qulity Improvement Using Dynmic Voltge. Electricl Power Qulity nd Utiliztion Journl, 14(1). 39-46. enchib,., & Ferdi,. (2008b) Modeling nlysis nd Solution of Power Qulity
FUTO Journl Series (FUTOJNLS), 2015, VOL. 1, Issue 1 65 Problems. Electricl Power qulity nd Utiliztion. 16(1). 15-25. hoi, S., Li, J. nd. Vilthgmuw, M. (2005) Generlized Voltge ompenstion Strtegy for Mitigting the Impcts of Voltge Sgs/Swells. IEEE Trnsction on Power Delivery. 20(3). 2289-2298. El-Gmm, M., bou-ghzl,.y. & El- Shennwy, T.I. (2011) Dynmic Voltge Restorer For Voltge Sg Mitigtion. Interntionl Journl of Electricl Engineering nd Informtics. 3(1). 1-11. Fitzer,., rnes, M. nd Green, P. (2004) Voltge Sg Detection Technique for Dynmic Voltge Restorer. IEEE Trnsction on Industry pplictions. 40(1). 203-212. Gnesh, S., Reddy, K. nd Rm,. (2009) Neuro ontrol Strtegy for scded Multilevel Inverter sed Dynmic Voltge Restorer. Interntionl Journl of Electricl nd Power Engineering. 3(4). 208-214. Hque, M.H. (2011) ompenstion of Distribution System Voltge Sg by DVR nd DSTTOM. Power Tech Proceedings IEEE Porto. 1.10-13. Hque, M. H. (2001) Voltge Sg correction by Dynmic Voltge Restorer with minimum power injection. IEEE Power Engineering Review. 21(5). 56 58. IEEE Stndrd bord. IEEE Std 1159-1995: IEEE Recommended Prctice for Monitoring Electric Power Qulity. The Institute of Electricl nd Electronics Engineers, Inc. 1995, 11-23. Jen,.K., Mohptr,., & Prdlon, K. (2012) Modeling nd Simultion of Dynmic Voltge Restorer. Electricl Power Qulity nd Utiliztion Journl. 3. 12-32. Kvith, M., hndrsekhr, T., & Reddy, D. (2013) Designing of dynmic Voltge Restorer to Improve the Power Qulity for Restructured Power System. mericn Journl of Electricl Power nd Energy System. 2(3), 94-97. 2013 vilble from: http://doi:1011648/j.epes.20130203.15 [ccessed 20th My, 2014]. Llith, V. & Vindhy, K. (2013) Improvement of Power Qulity Using Repetitive ontroller for Dynmic Voltge Restorer. Interntionl Journl of Science nd Reserch. 2(11), 416-420. Li,. H., hoi, S.S., nd Vilthgmuw, D.W. (2001) Design considertions on the line side filter used in the Dynmic Voltge Restorer. IEE Proceedings of Genertion, Trnsmission nd Distribution. 148(1). 1 7. Loh, P., Vilthgmuw, M., Tng,S. & Long, H. (2004) Multilevel Dynmic Voltge Restorer. IEEE Power Electronics Letters. 2(4). 125-130. Mllel, V. S., Solnki, P. S. & hturvedi,. (2005) Role of Dynmic Voltge Restorer in Mitigtion of Power Qulity Problems. Interntionl onference on ommuniction, omputer & Power. 161-166. Nielsen, J. G. (2002) Design nd ontrol of Dynmic Voltge Restorer. Disserttion Submitted in prtil fulfilment of the Requirements of lborg University for the Degree of Doctor of Philosophy. lborg. lborg University, Denmrk. Nguyen, P.T. & Sh, T. K. (2004) Dynmic Voltge Restorer ginst blnced nd unblnced voltge sgs: Modeling nd simultion. IEEE trnsctions on Power Delivery. 4(5). 1-6. Pndey,. (2013) Dynmic Voltge Restorer nd its ppliction t LV nd MV level. Interntionl Journl of Scientific nd Engineering Reserch. 4. 668-671. Pnte, N., nd Kristin L. (2008) Fctor ffecting hrcteristic of Voltge Sg Due to Fult in Power System. Journl of Electricl Engineering. 5 (1). 171-182. Reddy, K. & nyneyulu, K. S. (2001) New Technique for improving The Power Qulity In Power Trnsformer y FPG. Journl of Theoreticl nd pplied Informtion Technology, 169-175. Roncero-Sánchez, P., ch, E., Orteg-lderon Vicente Feliu, J. E. & Grcí-errd,. (2009) verstile control scheme for
FUTO Journl Series (FUTOJNLS), 2015, VOL. 1, Issue 1 66 dynmic voltge restorer for powerqulity improvement. IEEE Trnsctiwon on Power Delivery. 24(1). 277-284. Tumy, M., Teke,., yindir, K. & um, M. (2011) Simultion nd Modeling of Dynmic Voltge Restorer. IEEE Trnsction on Power Delivery, 20(1). 20-25. Vivek, M. nd Srividhy, P. (2013) Power Qulity Improvement Techniques In Hybrid System. Interntionl Journl of Technology nd Engineering Reserch [Online]. 3(5). 56-59. vilble from: http://www.ijter.com. Wng, Q. nd hoi, S. (2008) n Energy-Sving Series ompenstion Strtegy Subject to Injected Voltge nd Input-Power Limits. IEEE Trnsction on Power Delivery. 23(2). 1121-1131.