International Journal of Engineering Research And Management (IJERM) ISSN : 2349- 2058, Volume-1, Issue-1, April 2014
Simultaneous Voltage Sag, Swell, Reactive Power Compensation and Voltage Regulation in Distribution System With Series And Shunt Inverters Control Of UPQC Ch.Shravani Abstract—Voltage Sag/Swell on the distribution system is the one of the phenomena that leads to major Power Quality problem. The extensive use of non-linear loads in distribution system is also a contribution to increase the voltage harmonics and power quality issues. The compensation of Reactive Power is one of the common, but very important issues of Power System at the level of distribution. The voltage drop/swelling can be effectively compensated with a dynamic voltage restorer, series active filter, UPQC. In this paper, a new control controlled concept is proposed for compensation of voltage Sag/Swell and load Reactive power simultaneously by using Unified Power Quality Conditioner. Series and Shunt inverters of UPQC are controlled for obtaining the above mentioned characteristics. Series inverter of UPQC can be controlled in two aspects. For voltage sag and swell can de controlled with active power control and reactive power can be controlled with Power angle control concept. PAC concept can be useful for compensation of voltage sag and swell, load reactive power sharing between series and shunt inverters at a time. With this the ratings of shunt inverter can de reduced. Detailed mathematical analysis for the proposed concept that is for series injected voltage and shunt injected current and regulation of voltage with controller is presented in this paper. To support the propos MATLAB/ Simulink based simulation results are developed.
INTRODUCTION Quality of Power (PQ) has been identified as an important concern to improve the efficiency of the system, the reduction of several losses and to guarantee the production quality. The quality of the energy can be classified as a measure of electrical energy is available to the customers. The drop in voltage/swell on the system and one of the most important power quality problems. The drop in voltage/bulge can be effectively compensated with a dynamic voltage restorer, series active filter, UPQC etc. Between the power quality enhancement devices, the UPQC has better sag/swell compensation capacity. Basic block diagram of UPQC based system is shown in fig (1). Some papers are there on the control concept of UPQC. Basic Overview UPQC is shown in Figure.1, where, how the whole control circuit is in the Figure.2. The voltage at the PCC is or are not distorted depending on the other non-linear loads connected to PCC be disabled. Here the adoption of the voltage at the PCC is distorted. Two voltage inverters are connected, a common DC link. There are different control approaches are there which are given under: Control the active power approach in which a phase voltage and is injected through the inverter series [ 16] - [ 22 ], popularly known as UPQC-P, reactive power control approach in that the voltage and quadrature injected [ 23], [ 24], known as UPQC-Q, and A minimum approach VA load in the current series that is injected into a certain angle, [ 25] - [ 28], in this book called as UPQC-VAmin
Index Terms— Voltage Sag, Swell, Reactive Power Compensation, Voltage Regulation, UPQC Fig(1) UPQC configuration
Manuscript received April 19, 2014
Ch.Shravani, Department of Electrical and Electronics Engineering TKR Engineering college, Hyderabad , INDIA.
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International Journal of Engineering Research And Management (IJERM) ISSN : 2349- 2058, Volume-1, Issue-1, April 2014 In this paper, the concept of PAC UPQC extends to tension and swell. This modified approach is used to compensate for voltage case/clan to share the load between two reactive power investors. As an investor UPQC series in this case provides both active and reactive power, has been given the name UPQCS (S of complex power). The most important contribution of this paper can be summarized as follows. 1. The series inverter the UPQC-S for at the same time voltage price/expansion compensation and load response power compensation in the coordination and triage inverter. 2. In UPQC-S, available loading to use its maximum capacity of all the conditions of work against UPQCVAmin primary focuses on reducing where VA UPQC loading the voltage decline. 3. The concept, UPQC covered as well as voltage drops of expansion. 4.Voltage Regulation
MATHEMATICAL COMPUTATIONS OF SERIES AND SHUNT INVERTER PARAMETERS UNDER VOLTAGE SAG CONDITION In order to implement the power angle control approach in practice, it is necessary to estimate the power angle between source and load voltages of, based on the load of reactive power demand, but in an instantaneous way. This paper proposes a instantaneous angle determination based on instantaneous load and -reactive power extraction. In a first moment, it was considered that the PAC offers a power angle difference. Fig(3) shows the detailed analysis for series inject voltage under voltage sag condition. Where Vsr1 and Vsr2 are the series injected voltages for the compensation of load reactive power and voltage sag respectively. Total injected voltage through series inverter be the vector sum of above two voltages.
POWER ANGLE CONTROL APPROACH This paper is an attempt to make the use of the existing series inverter to compensate for load of reactive power through the introduction of an angle difference between source and load voltage, keeping both of the voltage magnitude of same. Eventually, will result in better utilization of investor series. The voltage sag of the distribution network can be effectively compensated by reactive [ 8], as well as the active power. Fig 2. Angle of control (PAC) concept: vector representation, UPQC through approaches. With the control of the reactive power approach the burden of reactive power can be compensated by a certain percentage along with the voltage sag compensation. Whereas the voltage at source as reference pharos, during normal working conditions the input voltage and the load voltage will be with the same amplitude and phase, the line impedance is neglected since the UPQC is assumed to be installed in the vicinity, close to loads, and for the sake of simplicity assume lanced, harmonious without source voltages without yielding nd/or swelling, represented by Vs and V respectively. In this AC concept a voltage of Vsr with the magnitude VSr and phase ϕSr s injected through series inverter for an angular displacement of δ between source and load voltages
Fig (3). Under voltage sag condition, vector representation for proposed concept
a) Series Inverter Parameters Estimation In this section, the parameters required for the series inverters for simultaneous load reactive power and the voltage sag compensation calculated. Below fig 4 shows the pharos diagram. Detailed figure found the amplitude and the phase of the series injection voltage.
Fig. (4) Phsor diagram for estimation of para meters of ser ies inverter for voltage Sag condition
Consider,
From the Fig, Where w=z
Fig(2). Basic PAC concept for UPQC
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International Journal of Engineering Research And Management (IJERM) ISSN : 2349- 2058, Volume-1, Issue-1, April 2014 Series injected voltage is from the
b) Shunt Inverter Parameters Estimation
……… (2) By considering the Voltage fluctuation factor kf . this is defriended as the ratio of difference between source voltage and rated load voltage to the rated load voltage. Which is given by the below equation
In this section, the parameters required for the shunt inverters for simultaneous load reactive power and the voltage sag compensation calculated. Below fig 5 shows the phasor diagram. Detailed figure found the amplitude and the phase of the shunt injection current.
……………. (3)
Consider
………....... (4) Fig (5). Phasor diagram for the estimation of shunt inverter parameters, in terms of current phasors
…………….. (5) From computation of series injected voltage magnitude,
Let us consider for the given load condition the input power can be taken as,
………………. (6) For calculation of Phase of Series injected voltage .where
Let
……………. (7)
So,
……………….. (9)
………………. (10)
……………… (11)
So, Form the fig(5)
…………… (8) The equations (6) and (7),(8) gives the information for the magnitude and phase of the series injected voltage for UPQC which should be injected for the compensation of Voltage Sag along with the Reactive for power angle control approach Power
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……………… (12)
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International Journal of Engineering Research And Management (IJERM) ISSN : 2349- 2058, Volume-1, Issue-1, April 2014
Fig(8) Generation of reference signals for series inverter for PAC concept
b) Shunt injected current generation
…………………. (13) The equations (12) and (13) gives the information for the magnitude and phase of the shunt injected current for UPQC which should be injected for the compensation of Voltage Sag along with the Reactive for power angle control approach Power through the shunt inverter For voltage swell also we will get the same equations DESIGN OF CONTROLLERS FOR PROPOSED SYSTEM This section deals with the generation of injected signals for series and shunt inverters of UPQC. a) Generation of load angle Load on the system may not to be constant at all time. So, with the change in load, load reactive power can varies. Load angle for the proposed power angle control concept is generated from real and reactive powers as mentioned below.
Fig (9) Genera tion of reference signals for shu nt inverter for P AC concept
Fig(9) shows the shunt injected current generation for shunt inverter with the use of load angle and constant Ko. With the help of mathematical computations values for the injected current and its phase are calculated with the use of equations 12 and 13 SIMULATION RESULTS Proposed system for simultaneous voltage sag/swell and reactive power compensation along with the voltage regulation is evaluated with simulation. A three-phase voltage of 600V, 60Hz is used as source voltage. Sh i m power sys t em block of MATLAB/SIMULINK is used as simulation tool.
Fig(7) Load angle determination
a) Series injected voltage generation Below fig(8) shows the series injected voltage generation for series inverter with the use of load angle and constant Ko. With the help of mathematical computations values for the injected voltage and its phase are calculated with the use of equations 6,7 and 8.
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By considering the sag and swell on the system results are obtained. At the instant of t1 sag is their on the system and at the instant of t2 swell is considered. Form the Fig 10(a) and (b), independent to sag and swell on the system load voltage is maintained at desired value. And from fig10 (f) the current is increased under sag and decreased under swell for balancing the power. With the use of PI controller for UPQC, the response of the system is increased and the system attains its steady state value with shorter interval of time. Under sag condition reactive power supplied by series inverter increases with increase in current at the same time to meet the desired reactive power, shunt inverter supplies less reactive power. www.ijerm.com
F
International Journal of Engineering Research And Management (IJERM) ISSN : 2349- 2058, Volume-1, Issue-1, April 2014 With this sharing of reactive power between shunt and series inverters the rating of shunt inverter reduces
.
Fig(10) Simulation results for the proposed PAC control concept along with controller
CONCLUSION In this paper proposed concept useful for both active and reactive power control and sag and swell on the system are compensated. With the use of controller at the dc link the response of the system is increased. With this the stability of the system is also i nc r e a s e s . Simultaneously sag/swell and reactive power can be compensated with the proposed concept and the voltage is also regulated at the dc link. And the rating of the shunt inverter will be reduced. Simulation results shows the efficiency of the system and stability REFERENCES [1] R. C . Dugan, M. F. Mc Granaghan, and H. W. Beaty, Electrical Power Systems Quality.. New York: McGraw-Hill, 1996, p. 265.
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[2] C. Sankaran, Power Quality. Boca Raton, FL: CRC Press, 2002, p. 202. [3] V. Khadkikar and A. Chandra, ―A new control philosophy for a unified power quality conditioner (UPQC) to coordinate load-reactive power demand between shunt and series inverters,ǁ IEEE Trans. Power Del., vol. 23, no. 4, pp. 2522–2534, Oct. 2008. [4] V. Khadkikar, A. Chandra, A. O . Barry, and T. D. Nguyen, ―Analysis of power flow in UPQC during voltage sag and swell conditions for selection of device ratings,ǁ in Proc. IEEE Electr. Computer Eng. (CCECE), May 2006, pp. 867–872. [5] G. S. Kumar, P. H. Vardhana, B. K. Kumar, and M. K. Mishra, ―Minimization of VA loading of unified power quality conditioner (UPQC),ǁ in Proc. IEEE Powereng, Mar. 18–20, 2009, pp. 5 5 2–557. V. Khadkikar and A. Chandra, ― [6] A. Ghosh and G. Ledwich, Po wer Quality Enhancement Using Custom Power Devices. Boston, MA: Kluwer, 2002, p. 460.
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International Journal of Engineering Research And Management (IJERM) ISSN : 2349- 2058, Volume-1, Issue-1, April 2014 [7] B. Singh, K. Al-Haddad, and A. Chandra, ―A review of active e power filters for power quality improvement,ǁ IEEE Trans. Ind. Electron., vol. 45, no. 5, pp. 960–971, Oct. 1999. [8] M. El-Habrouk, M. K. Darwish, and P. Mehta, ―Active power filters: A review,ǁ IEE Electr. Power Appl., vol. 147, no. 5, pp. 403–413, Sep. 2000. [9] Doncker, C. Meyer, R. W. De, W. L. Yun, and F. Blaabjerg, ―Optimized control strategy for a medium-voltage DVR—Theoretical investigations and experimental r esults,ǁ IEEE Trans. Power Electron., vol. 23, no. 6, pp. 2 7 4 6–2754, Nov. 2008. [10] C. N. Ho and H. S. Chung, ―Implementation and performance evaluation of a fast dynamic control scheme for capacitor-supported interline DVR,ǁ IEEE Trans. Power Electron., vol. 25, no. 8, pp. 1 9 7 5–1988, Aug. 2010. [11] Y. Chen, C. Lin, J. Chen, and P. Cheng, ― An inru sh mitigation technique of load transformers for the series voltage sag compensator,ǁ IEEE Trans. Power Electron., vol. 25, no. 8, pp. 2211–2221, Aug. 2010. [12] UPQC-S: A Novel Concept of Simultaneous Voltage Sag/Swell and Load Reactive Power Compensations Utilizing Series Inverter of UPQC by Vinod Khadkikar, Member, IEEE , and Ambrish Chandra, Senior Member, IEEE
Ch.Shravani is B.Tech Graduate in Electrical and Electronics Engineering 2008, JNTU-Hyd. INDIA and she is Pursuing M.Tech – Power Electronics from JNTU-H, Hyd. INDIA. She has 4 years of experience in various Engineering colleges. At Present she is working as Assistant Professor in TKREC, Hyderabad, INDIA.
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