HARMONIC COMPENSATION ANALYSIS USING UNIFIED SERIES SHUNT COMPENSATOR IN DISTRIBUTION SYSTEM

Transcription

1 HARMONIC COMPENSATION ANAYSIS USING UNIFIED SERIES SHUNT COMPENSATOR IN DISTRIBUTION SYSTEM * Montazeri M. 1, Abai Garavand S. 1 and Azadbakht B. 2 1 Department of Electrical Engineering, College of Engineering, Borujerd Branch, Ilamic Azad Univerity, Borujerd, Iran 2 Department of Medical Radiation Engineering, College of Engineering, Borujerd Branch, Ilamic Azad Univerity, Borujerd, Iran * Author for Correpondence ABSTRACT The huge boom oberved in the ue of electronic device, in the lat decade, ha atonihing increaed the main harmonic content. The conequent undeirable effect are the primary caue of electromagnetic compatibility problem, ine wave ditortion, extra diipative loe, exceive neutral current, even in equilibrated three-phae load. Therefore a great amount of effort ha been made in order to minimize all thoe unwanted and quite expenive effect. Thi paper focued on the harmonic compenation in ditribution ytem. The erie- hunt compenation of harmonic due to nonlinear load uing USSC in thi reearch i analyzed and imulated. INTRODUCTION Mitigation of power ytem harmonic can be categorized a corrective olution and precautionary olution. Corrective (remedial) olution are the technique to overcome the exiting problem. The ue of active and paive filter Reconfiguration of the feeder or reallocation of capacitor bank to overcome the reonance. And precautionary (Preventive) olution aim to avoid harmonic and their conequence. Phae cancellation or harmonic control in power convertor. Developing procedure and method to control, reduce or eliminate harmonic in power ytem equipment; mainly capacitor, tranformer and generator. Paive filter coniting of capacitor, inductor and/or reitor can be claified into tuned filter and high-pa filter. They are connected in parallel with nonlinear load uch a diode/thyritor rectifier, ac electric arc furnace, and o in. Intallation of uch a paive filter in the vicinity of a nonlinear load i to provide low-impedance path for pecific harmonic frequencie, thu reulting in aborbing the dominant harmonic current flowing out of the load. Before intalling a paive filter, engineer hould make elaborate invetigation into the poibility of harmonic reonance and overloading on a cae-by-cae bai. However, thee invetigation may be accompanied by relatively high engineering cot. In addition, the final deign of a paive filter hould allow for component tolerance and variation. For example, initial inductor/capacitor tolerance typically range within 5%, and their variation occur due to temperature and other operating condition (Riva et al., 2003). Pure active filter can be claified into hunt (parallel) active filter and erie active filter from their circuit configuration. At preent, hunt active filter are more preferable than erie active filter in term of form and function, and therefore erie active filter are uitable excluively for harmonic filtering. Two type of hybrid active filter for harmonic-current filtering of nonlinear load were propoed in (Akagi, 1996), repectively. The propoal of the two hybrid filter ha encouraged power electronic reearcher/engineer to do further reearch on variou hybrid active filter, concentrating on their practical ue (i et al., 2005). The Unified Shunt Serie Compenator (USSC) conit of back-to-back connection of two three phae active filter (AF) with a common DC link. One of the AF i connected in parallel with the utility and i called Parallel Active Filter (PAF) (Hideaki and Hirofumi, 1998.). The PAF work a current ource and uually compenate for current quality problem of load and regulating of DC link. On the other hand, the econd AF connected in erie with the utility and act a Serie Active Filter (Bau et al., 2001) to compenate for voltage quality problem of utility. In thi way, operation of USSC iolate the utility Copyright 2014 Centre for Info Bio Technology (CIBTech) 670

2 from current quality problem of load and in the ame time, iolate the load from voltage quality problem of utility (USSC) i being ued now-a-day. USSC Intallation in Ditribution Sytem Before modeling the USSC, all ditribution ytem component, i.e., line and cable, load, tranformer, large motor and generator have to be converted into equivalent reactance () and reitance (R) on common bae. The main ytem component model are ued in the formulation of impedance matrix for voltage ag calculation (Hannan and Mohamed, 2004). In teady tate analyi, erie and hunt inverter of the USSC are preented by two voltage ource and h repectively a hown in Figure 1. Figure 1: Equivalent circuit of USSC c and h repreent the reactance of the tranformer aociated with the erie and hunt voltage ource inverter, repectively. Therefore, voltage equation of erie and hunt inverter can be expreed a follow: I e e e ( j ) e 0 ( j e) h ( h) h 0 h Where I c and I are the erie and hunt inverter current, repectively. The voltage acro the ditribution line reactance, i ( j ) 0. I e e Where, I i ditribution line current. The voltage,, acro the ditribution line can be changed by changing the inerted voltage,, which i in erie with the ditribution line. If we conider =0, the ditribution line ending end voltage, S, lead the load voltage by an angle i.e S. The reulting real and reactive power flow at the load ide are P and Q, which are given a follow: 0. Puc in (5) 0. Q (1 co ) With an injection of, the ditribution line voltage 0 will lead the load voltage, and 0., thu the reulting line current and amount of flow Will be changed. With a larger amount of injection, 0 now lag the load voltage, and 0. Conequently, the line current and power flow will be revered. Copyright 2014 Centre for Info Bio Technology (CIBTech) 671 (1) (2) (3) (4) (6)

3 Harmonic Concept Harmonic have frequencie that are integer multiple of the waveform fundamental frequency. For example, given a 50Hz fundamental waveform, the 2nd, 3rd, 4th and 5thharmonic component will be at 100Hz, 150Hz, 200Hz and 250Hz repectively (Balci and Hocaoglu, 2008). Thu, harmonic ditortion i the degree to which a waveform deviate from it pure inuoidal value a a reult of the ummation of all thee harmonic element. The ideal ine wave ha zero harmonic component. In that cae, there i nothing to ditort thi perfect wave. Power ource act a non-linear load, drawing a ditorted waveform that contain harmonic. In preence of inuoidal ource voltage due to non-linear load the current which drawn via ource i harmonic ditorted. Thee harmonic can caue problem ranging from telephone tranmiion interference to degradation of conductor and inulating material in motor and tranformer. Therefore it i important to gauge the total effect of thee harmonic. Harmonic ditortion can have detrimental effect on electrical equipment. Unwanted ditortion can increae the current in power ytem which reult in higher temperature in neutral conductor and ditribution tranformer. Higher frequency harmonic caue additional core lo in motor which reult in exceive heating of the motor core. Thee higher order harmonic can alo interfere with communication tranmiion line ince they ocillate at the ame frequencie a the tranmit frequency. If left unchecked, increaed temperature and interference can greatly horten the life of electronic equipment and caue damage to power ytem. To evaluate the degree of harmonic ditortion, an index named Total harmonic ditortion, or THD, baed on the IEEE definition, i defined a the ummation of all harmonic component of the voltage or current waveform M compared againt the fundamental component of the voltage or current i M 1 (Afono et al., 2000): 2 M i (7) i2 THD M1 The end reult i a percentage comparing the harmonic component to the fundamental component of a ignal. The higher the percentage, the more ditortion that i preent on the main ignal. RESUTS AND DISCUSSION Simulation and Reult In thi ection to invetigate the effect of USSC on harmonic compenation due to nonlinear load i preented. At firt to model the harmonic a programmable main ac ource which inert harmonic to network i imulated. In Figure 2 the power network with preence of USSC i preented. Figure 2: The USSC in network Copyright 2014 Centre for Info Bio Technology (CIBTech) 672

4 A hown in Figure 3 the three phae voltage load which i ditorted to harmonic i indicated. Figure 3: the three phae harmonic ditorted voltage To better undertand the amount of harmonic value, the THD analyi of voltage wave i performed and the THD of none compenated voltage i hown in Figure 4. Figure 4: THD of load voltage without any compenation To reduce the harmonic the USSC i connected to network. The ac voltage of load with preence of USCC i improved and to verify thi matter the THD analyi i performed again. To how the effect of USSC on harmonic compenation, the THD of load voltage i preented in Figure 5. Copyright 2014 Centre for Info Bio Technology (CIBTech) 673

5 Figure 5: THD of load voltage without any compenation A hown in figure, uing USSC the THD of load i deceaed and thi verifie the effective role of USSC on harmonic mitigation. Concluion Thi paper deal with harmonic compenation uing unified erie hunt compenator. The conventional of harmonic compenation method are utilizing paive filter and active filter. But in thi reearch due to multifunctional in power quality improvement a combination of two active filter i preented. The firt active filter i connected to network a erie connection and econd active filter i connected to network a parallel connection. Thi connection of two active filter i named a unifie erie hunt compenator (USSC). Thi type of compenation can improve a variety of power quality compenation. In other word, uing USSC it i poible to improve variou power quality problem including voltage ag/well, harmonic, unbalanced voltage and flicker. It alo can improve the power factor. Due to multi capability of USSC, thi equipment i employed to improve power quality of network. In thi reearch the focu i on the harmonic compenation and the reult of thi tudy are preented. REFERENCES Afono J, Couto C and Martin JS (2000). Active Filter with Control Baed on the p-q Theor. IEEE Indutrial Electronic Society Newletter 47(3) Akagi H (1996). New Trend in Active Filter for Power Conditioning. IEEE Tranaction on Indutry Application 32(6) Erhan Balci M and Hakan Hocaoglu M (2008). Effect of Source oltage Harmonic on Power Factor Compenation in AC Chopper Circuit. Electrical Power Quality and Utilization Journal 14(1) Hannan MA and Mohamed A (2004). Unified Serie-Shunt Compenator: Modeling and Simulation, Proceeding of National Power & Energy Conference (PECon), KuaIa umpur, Malayia. Hideaki Fujita and Hirofumi Akagi (1998). The Unified Power Quality Conditioner: The Integration of Serie and Shunt Active Filter. IEEE Tranaction on Power Electronic 13(2) i H, Zhuo F, Wang Z, ei W and Wu (2005). A Novel Time-Domain Current-Detection Algorithm for Shunt Active Power Filter. IEEE Tranaction on Power Sytem 20(2) Malabika Bau, Da SP and Gopal Dubey K (2001). Requirement of USSC and It Rating Iue for Non-inear and oltage Senitive oad. International Conference on Power Quality - Aement of Impact, 6-7 November, New Delhi. Riva D, Moran, Dixon JW and Epinoza JR (2003). Improving Paive Filter Compenation Performance with Active Technique. IEEE Tranaction on Indutrial Electronic 50(1) Copyright 2014 Centre for Info Bio Technology (CIBTech) 674