POWER QUALITY IMPROVEMENT BY SRF BASED CONTROL USING DYNAMIC VOLTAGE RESTORER (DVR)

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1 Interntionl Journl of Electricl Engineering & Technology (IJEET) Volume 9, Issue 1, Jn-Fe 2018, pp , rticle ID: IJEET_09_01_005 ville online t ISSN Print: nd ISSN Online: Journl Impct Fctor (2016): (lculted y GISI) IEME Puliction POWER QULITY IMPROVEMENT Y SRF SED ONTROL USING DYNMI VOLTGE RESTORER (DVR).V.V. Pvni Lecturer, Deprtment of Electricl nd omputer Engineering, Dill University, Ethiopi P. Sreelth ssistnt Professor, Deprtment of Electricl & Electronics Engineering, Sridevi Women s engineering ollege, Hyderd, Telngn, Indi STRT Power Qulity prolems encompss wide rnge of disturnces such s voltge sgs/swells, flicker, hrmonics distortion, impulse trnsient, nd interruptions This pper descries the prolem of voltge sgs, swells, hrmonics nd its severe impct on non-liner lods or sensitive lods. The dynmic voltge restorer (DVR) hs ecome populr s cost effective solution for the protection of sensitive lods from voltge sgs nd swells. The control of the compenstion voltges in DVR cn e performed with Synchronous reference frme theory (SRF). In this pper, it first nlyzes the power circuit of DVR system in order to come up with pproprite control limittions nd control trgets for the control strtegy. Simultion results re crried out y Mtl/Simulink verify the performnce of the proposed method. Key words: Power Qulity, DVR, SRF, ompenstion. ite this rticle:.v.v. Pvni nd P. Sreelth, Power Qulity Improvement y SRF sed ontrol Using Dynmic Voltge Restorer (DVR). Interntionl Journl of Electricl Engineering & Technology, 9(1), 2018, pp INTRODUTION Power Qulity prolems encompss wide rnge of disturnces such s voltge sgs/swells, flicker, hrmonics distortion, impulse trnsient, nd interruptions. Voltge sgs cn occur t ny instnt of time, with mplitudes rnging from 10 90% nd durtion lsting for hlf cycle to one minute. In other word it is defined s sudden reduction of supply voltge down 90% to10% of nominl nd followed y recovery fter short period of time. It is considered s the most serious prolem of power qulity. It is cused y fult in power system or y strting of lrge induction motor. It cn interrupts or 51 editor@ieme.com

2 Power Qulity Improvement y SRF sed ontrol Using Dynmic Voltge Restorer (DVR) mlfunction ny electronic or electricl equipment which is sensitive to lod. Therefore huge losses result, due to voltge sg prolem t customer lod end. Voltge swell, on the other hnd, is defined s swell is defined s n increse in rms voltge or current t the power frequency for durtions from 0.5 cycles to 1 min. typicl mgnitudes re etween 1.1 nd 1.8 up. Swell mgnitude is lso is lso descried y its remining voltge, in this cse, lwys greter thn 1.0. Hrmonics re non-fundmentl frequency components of distorted frequency wveform. They hve frequencies tht re integer multiples of the fundmentl frequency. The ojective of the electric utility is to deliver sinusoidl voltge t firly constnt mgnitude throughout their system. This ojective is complicted y the fct tht there re lods on the system tht produce hrmonic currents. These currents result in distorted voltges nd currents tht cn dversely impct the system performnce in different wys. There re two importnt concepts to er in mind with regrd to power system hrmonics. The first is the nture of hrmonic current-producing lods (non-liner lods) nd the second is the wy in which hrmonic currents flow nd how the resulting hrmonic voltges develop. There re mny different methods to mitigte voltge sgs, swells nd hrmonics, ut the use of custom Power device is considered to e the most efficient method. Like Flexile Trnsmission Systems (FTS) for trnsmission systems, the term custom power pertins to the use of power electronics controllers in distriution system, especilly, to del with vrious power qulity prolems. Just s FTS improves the power trnsfer cpilities nd stility mrgins, custom power mkes sure customers get pre specified qulity nd reliility of supply. This pre specified qulity my contin comintion of specifictions of the following: low phse unlnce, no power interruptions, low flicker t the lod voltge, low hrmonic distortion in lod voltge, mgnitude nd durtion of over voltges nd under voltges within specified limits, cceptnce of fluctutions, nd poor fctor lods without significnt effect on the terminl voltge. Ech of ustom Power devices hs its own enefits nd limittions. Dynmic Voltge Restorer (DVR) is one of the most effective type of these devices. The Schemtic structure of DVR is shown in Fig 1.1 Figure 1.1 Schemtic structure of DVR 52 editor@ieme.com

3 .V.V. Pvni nd P. Sreelth 2. ONTROL TEHNIQUE FOR DVR 2.1. Synchronous reference frme theory (SRF): Figure 2.1 Internl View of Synchronous reference frme theory (SRF) ontrol strtegy Fig 2.1 shows The internl view of Synchronous Reference Frme Theory (SRF) control strtegy for DVR. In this control strtegy the SRF-sed DVR control technique is used to generte gte pulses for controlling of DVR. Here from the control strtegy is designed with c frme to d-q frme conversion lock, PLL lock, HPF, PI controller, DQ to conversion lock nd hysteresis controller. The c frme to d-q frme conversion lock converts 3Փ lod current prmeters (Ic) to dq0 prmeters frme y using prks trnsformtion. The phse locked loop genertes Sin ωt nd cos ωt signls for trnsformtion lock. Initilly, the current components from lock in α-β co-ordintes re generted. Ic phses cn then e trnsformed into α-β coordintes. HPF is high pss filter is used to lock low frequency components coming from conversion lock. The V d reference nd ctul vlue is compred then given to pi controller is gin compred with I d loss vlue then given to inverse trnsformtion lock nd then the output of inverse trnsformtion lock is DVR reference current is compred with ctul DVR current then given to Hysteresis controller which will generte gte pulses for switches. ll this process is given in figure 2.2 Figure 2.2 lock Digrm of SRF theory 53 editor@ieme.com

4 Power Qulity Improvement y SRF sed ontrol Using Dynmic Voltge Restorer (DVR) 2.2. Synchronous Reference Theory (SRF) In the SRF [6], the lod current signls re trnsformed into the conventionl rotting frme d-q. If thet is the trnsformtion ngle, the trnsformtion is defined y: Fig.2.3 shows the sic configurtion of synchronous reference frme. In the SRF is time vrying ngle tht represents the ngulr position of the reference frme which is rotting t constnt speed in synchronism with the three phse c voltges. In the SRF θ is time vrying ngle tht represents the ngulr position of the reference frme which is rotting t constnt speed in synchronism with the three phse c voltges. Figure 2.3 sic configurtion of SRF 3. SIMULTION OF DVR Figure 3.1 shows the configurtion of the proposed DVR design using MTL/SIMULINK, where the outputs of three-phse hlf-ridge inverter re connected to the utility supply vi wye-open connected series trnsformer. Once voltge disturnce occurs, with the id of dq0 trnsformtion sed control scheme, the inverter output cn e steered in phse with the incoming c source while the lod is mintined constnt. s for the filtering scheme of the proposed method, output of inverter is instlled with cpcitors nd inductors. Performnce of DVR in mitigting voltge sgs/swells is demonstrted with the help of MTL. forced commutted voltge sources converter is considered in the DVR long with energy storge to mintin the cpcitor voltge editor@ieme.com

5 V.V. Pvni nd P. Sreelth ontinuous Trnsport Dely N Uref Pulses Discrete PWM Genertor N Progrmmle Voltge Source1 Progrmmle Voltge Source2 Universl ridge g + - node 10 D Voltge Source node 10 Vc c V-I Mesurement3 Series RL rnch Series RL rnch1 Ic c Trnsformer V-I Mesurement4 12 Terminls1 node 10 Vc c c Series RL rnch2 Trnsformer V-I Mesurement1 (Two Windings) c dq0 sin_cos Susystem Freq Vc(pu) wt Sin_os Discrete 3-phse PLL Vc Ic V-I Mesurement2 c c dq0 sin_cos Susystem1 Sg inj lod Susystem2 dq0 c sin_cos Series RL Lod Series RL Lod1 Series RL Lod2 dq0_to_c Trnsformtion 1 onstnt Scope Divide Figure 3.1 omplete Simulink model of DVR with SRF ontrol strtegy The sic simultion model consists of source, lod, DVR nd control lock. The liner lod connected is comintion of resistnce nd inductnce in series for ech phse nd the nonliner lod is diode ridge rectifier. This DVR is simulted with the ove descried Synchronous Reference Frme theory nd nd new ck propgtion control lgorithm. Figure 3.2 Output Wveforms of Voltge Sg pplictions: ) Supply Voltge ) Injected Voltge c) Lod Voltge Figure 3.3 Output Wveforms of Voltge Swell pplictions: ) Supply Voltge ) Injected Voltge c) Lod Voltge 55 editor@ieme.com

6 Power Qulity Improvement y SRF sed ontrol Using Dynmic Voltge Restorer (DVR) Fig 3.2 () shows the supply voltge nd the occurrence of voltge sg in the wveform. In () the injected voltge is represented with the help of DVR in oost mode using SRF control. The finl compensted lod voltge is represented in (c). In Fig 3.3 () shows the supply voltge nd the occurrence of voltge swell in the wveform. In () the injected voltge is represented with the help of DVR in stndy mode using SRF control nd ck propgtion lgorithm. The finl compensted lod voltge is represented in wve form(c). Due to the presence ridge rectifier, hrmonics re injected in the system. These hrmonic current is injected y DVR nd hrmonics cn e successfully eliminted. 4. ONLUSIONS The modeling nd simultion of DVR with SRF control strtegy using MTL/SIMULINK hs een presented. control system sed on dq0 technique which is scled error of the etween source side of the DVR nd its reference for sgs/swell correction hs een presented. The simultion shows tht the DVR performnce is stisfctory in mitigting voltge sgs/swells nd hrmonics. From simultion results lso show tht the DVR compenstes the sgs/swells quickly nd provides excellent voltge regultion. The DVR hndles oth lnced nd unlnced situtions without ny difficulties nd injects the pproprite voltge component to correct rpidly ny nomly in the supply voltge to keep the lod voltge lnced nd constnt t the nominl vlue. For nonliner lod cse the effect is compensted y DVR nd power fctor is mintined t unity. The hrmonic content of the current t source side is 1.52% when nonliner lod is connected. 5. FUTURE SOPE REFERENES The power demnd is lwys incresing dy y dy. The power qulity prolems re lso following the sme trend nd incresing dy y dy. So there is need to reduce such power qulity prolems like voltge sg nd swell nd mke the supply system efficient. DVR is one of the promising technologies to enhnce the power qulity of system. The power qulity cn e still improved y using soft computing techniques like Unified power flow controller, D- STTOM etc. FT devices cn e controlled through different control techniques to get etter coordintion etween rel nd rective power. [1].Ghosh nd G. Ledwich, Power Qulity Enhncement using ustom Power Devices, Kluwer cdemic Pulishers, London, [2] H. kgi, Y. Knzw, N. Ne, "Generlized theory of the instntneous rective power in three phse circuit", IPE"83-Interntionl Power Electronics onference, Tokyo, Jpn, pp , 1983 [3] H. kgi, E H Wtne nd M redes, "Instntneous power theory nd pplictions to power conditioning", John Wiley & Sons, New Jersey, US, [4] IEEE Recommended Prctices nd Requirements for Hrmonics ontrol in Electric Power Systems, IEEE Std. 519,1982. [5] Kirn Kumr Pinptruni nd Krishn Mohn L "DQ sed ontrol of STTOM for Power Qulity Improvement" pulished in VSRD-IJEEE, Vol. 2 (5), 2012, editor@ieme.com

7 .V.V. Pvni nd P. Sreelth [6] Kruppnn P nd KmlKnt Mhptr 'PLL with PI, PID nd Fuzzy Logic ontrollers Shunt ctive Power Line onditioners' IEEE PEDES-Interntionl onference on Power Electronics, Drives nd Energy Systems-, t IIT Delhi [7] Rosli Omr, Nsrudin d Rhim nd Mrizn Sulimn, Modelling nd Simultion for Voltge Sgs/ Swells mitigtion using Dynmic Voltge Restorer ( DVR) pulished in JTIT, [8]. enchi nd. Ferdi, Power qulity Improvement Using DVR, pulished in mericn Journl of pplied Sciences6 (3): , [9] Prof. hishek W. nkr nd Prof. Sndesh Shete, Power qulity improvement y SRF sed control using D-Sttcom, pulished in IRJET: Volume: 04 Issue: 06, June [10] S. Leel nd S.S.Dsh, ontrol of Three level Inverter sed Dynmic voltge Restorer, pulished in JTIT, [11] M. Thirupthih, P. Venkt Prsd nd V. Gnesh, nlysis of Vrious ompenstion Devices For Power Qulity Improvement In Wind Energy System. Interntionl Journl of Electricl Engineering & Technology, 7 ( 3 ), 2016, pp [12] M. T. Shh nd P. N. Tekwni, i-directionl Three- Level Front-End onverter For Power Qulity Improvement. Interntionl Journl of dvnced Reserch in Engineering nd Technology, 7(4), 2016, pp editor@ieme.com