Application of Synchronous Static Series Compensator (SSSC) on Enhancement of Voltage Stability and Power Oscillation Damping

Application of Synchronous Static Series Compensator (SSSC) on Enhancement of Voltage Stability and Power Oscillation Damping

ABSTRACT:

This paper investigates the problem of controlling and modulating power flow in a transmission line using a Synchronous Static Series Compensator (SSSC). The studies, which include detailed techniques of twelve pulse and PWM controlled SSSC, are conducted and the control circuits are presented. The developed control strategies for both twelve-pulse and PWM-controlled SSSC use direct manipulations of control variables instead of typical d-q transformations. The complete digital simulation of the SSSC within the power system is performed in the MATLAB/ Simulink environment using the Power System Block set (PSB). Simulation results validate that Voltage and Power Oscillation can be damped properly using of Synchronous Static Series Compensator (SSSC).

KEYWORDS:

1. SSSC

2. Reactive compensation

3. Control strategy

4. FACTS

5. PWM control
6. Voltage stabilization.

SOFTWARE: MATLAB/SIMULINK

FUNCTIONAL BLOCK DIAGRAM:

Fig 1. Functional model of SSSC

                                       

CIRCUIT DIAGRAM:

Fig 2. Static Synchronous Series Compensator (SSSC) used for power oscillation damping

EXPECTED SIMULATION RESULTS:

                                            Fig 3. A. SSSC Dynamic Response for Reactive Power     

                              

                                                                              Fig 3 .B. SSSC Dynamic Response for Voltage

                                            Fig 4. A. System without SSSC under a three-phase fault   for Reactive Power

                                                          Fig 4. B. System without SSSC under a three phase fault  for Voltage

     

                                                  Fig 5. A. System with SSSC under a three-phase fault for  Reactive Power  

                                                         Fig 5. B. System with SSSC under a three-phase fault for Voltage

CONCLUSION:

This paper analyzed the problem of controlling and modulating power flow in a transmission line using a Synchronous Static Series Compensator (SSSC). The studies, which include detailed techniques of twelve pulse and PWM controlled SSSC, are conducted and the control circuits are presented. The SSSC operating conditions and constraints are compared to the operating conditions of other FACTS devices, showing that the SSSC offers several advantages over others. However, at the present time the total cost of a SSSC installation is higher than the cost of other FACTS devices. Comparisons of two implemented control strategies clearly show that the PWM based and phase controller have both disadvantages and advantages, which makes the design process somewhat complicated. The dc voltage pre-set value in PWM-based controllers has to be carefully selected. As the modulation ratio lies between zero and one, the dc voltage should not be lower than the maximum of the requested SSSC output phase voltage in order to obtain proper control. On the other hand, if the dc side voltage is too high, the rating of both the GTO valves and dc capacitor has to be increased, which means higher installation costs. Not only that, a higher dc side voltage means a lower amplitude modulation ratio, and the lower modulation ratio results in higher harmonic distortion. Phase control allows the dc voltage to change according to the power system conditions, which is clearly advantageous, but it requires a more complicated controller and special and costly series transformers. Also, Simulation results validate that Voltage and Power Oscillation can be damped properly using of Synchronous Static Series Compensator (SSSC).

REFERENCES:

 [1] “Static Synchronous Compensator,” CIGRE, Working group 14.19, 1998.

[2] N. G. Hingorani and L. Gyugyi, Understanding FACTS, Concepts and Technology of Flexible AC Transmission Systems. Piscataway, NJ: IEEE Press, 2000.

[3] R. Mohan and R. K. Varma, Thyristor-Based FACTS Controllers for Electrical Transmission Systems. Piscataway, NJ: IEEE Press, 2002.

[4] L. Gyugyi, N. G. Hingorani, P. R. Nannery, and N. Tai “Advanced StaticVar Compensator Using Gate Turn- Off Thyristors for Utility Applications”, CIGRE, 23– .203, August 26 September 1, 1990, France

[5] J. Arrillaga, B. Barrett, N. A. Vovos “Thyristor Controlled Regulating Transformer for Variable Voltage Boosting”, IEE Proceedings, No. 10, October 1976.

Design and Specifications of SVPWM Controlled Three Phase Three Wire Shunt Active Power Filter for Harmonic Mitigation

Abstract

The most important part of the shunt active power filters is generating of gate signal for Voltage Source Inverters (VSI). In this paper the proposed Space Vector Pulse Width Modulation (SVPWM) is implemented in a closed loop control system for a shunt active power filter. The reference harmonic components are extracted from the sensed nonlinear load currents by applying the Synchronous Reference Frame (SRF) theory, where a three-phase thyristor bridge rectifier with R-L load is taken as the nonlinear load. The switching control algorithms of the proposed SVPWM would be generating appropriate switching gates to the voltage source inverter. The shunt active power filter generates the actual compensating harmonic current based on the switching gates provided by the controller. For showing the performance of proposed method a typical system has been simulated by MATLAB/SIMULINK. The proposed active power filter is able to improve about 30.18% of the total harmonic distortion (THD) for the distorted line current caused by an uncontrolled rectifier as the nonlinear load and to meet IEEE 519 standard recommendations on harmonics level.

Keywords

1.                  Power Quality

2.                  Shunt Active Power Filter

3.                  Synchronous Reference Frame Theory

4.                  Space Vector Pulse Width Modulation (SVPWM).

Software: Matlab/Simulink

Block Diagram                     Fig 1. Block diagram of proposed Shunt active power filter for a 3phase 3 wire system

Simulation Results:

Fig 2. Three phase voltage and load currents for before Compensation-simulation results:(a) a-phase voltage, volts, (b) a-phase load current, Amps 

Fig 3. %THD source current before compensation 

 Fig 4. Reference compensation-(a) a-phase compensation currents, Amps (b) b-phase compensation currents, Amps (c) c-phase compensation current, Amps.

 Fig 5. %THD source current after compensation

Fig 6. Source Voltages and Currents in three phases after compensation-(a)a-phase source voltage, (b)a-phase source current

Conclusion

In this paper, a novel simplified control method, which is suitable for digital control realization, for the active power filter using SVPWM is proposed. The objectives of this project have been achieved by reducing the harmonic components that exist in a power system with a chosen nonlinear load. This most recent aimed on the one hand to prove the effectiveness of the SVPWM in the contribution in the switching power losses reduction in shunt active filter. The proposed closed loop filtering control system mainly consists of the harmonics isolator, the hysteresis tolerance comparators conjunction with the space vector pulse width modulation controller and the active power filter. The combination of these components enables the closed loop control system to be implemented. The proposed system is able to compensate the harmonics caused by a three phase uncontrolled diode rectifier and it provides positive results by reducing the percentage of THD of the line current. The shunt active filter is found effective to meet IEEE 519 standard recommendations on harmonics level.      

References

[1] Singh.B, A1-Haddad.K, Chandra.A, “Review of active filters for power quality improvement”, IEEE Trans. Ind. Electron.,(46), 5, Oct, 1999, pp. 960-971

[2] E1-Habrouk. M, Darwish. M. K, Mehta. P, “Active power filters-A review,” Proc. IEE-Elect. Power Applicat., vol. 147, no. 5, Sept. 2000, pp. 403-413.

[3] Akagi, H., “New trends in active filters for power conditioning,” IEEE Trans. On Industry Applications, (32), 6, Nov-Dec, 1996, pp. 1312-1322

[4] Peng Fangzheng, “Application issues of active power filters,” IEEE Industry Applications Magazine, v 4, n 5, Sep-Oct, 1998, pp. 21-30

[5] Akagi.H, Kanazawa.Y, and Nabae.A, “Instantaneous reactive power compensators comprising switching device without energy storage components,” IEEE Trans. on Industry Applications, (20), 3, 1984, pp. 625-630.

Control Scheme to Improve DPFC Performance during Series Converter Failures

ABSTRACT

The Distributed Power Flow Controller (DPFC) is a new device within the FACTS family. It is emerged from the UPFC and has relatively low cost and a high reliability. The DPFC consists of two types of converters that are in shunt and series connected to grids. The common dc link between the shunt and the series converters is eliminated. The active power exchange between the shunt and series converters that is through the common dc link in the UPFC, is now though the transmission line at the 3rd harmonic frequency. The redundancy of the series converters provides the high reliability of the system. In this paper, the DPFC behavior during the failure of a single series converter unit is considered. A control scheme to improve the DPFC performance during the failure is proposed. The principle of the control is based on the facts that, the failure of single series converter will lead to unsymmetrical current at the fundamental frequency. By controlling the negative and zero sequence current to zero, the failure of the series converter is compensated. In this paper, the principle of the DPFC are firstly introduced, and followed by the behavior of the DPFC during the failure of a single series converter. The design of the control scheme and corresponding simulation are presented.

KEYWORDS

1.      Power Flow Control

2.      Flexible AC Transmission System

3.      Current Control

4.      symmetrical component

5.      Voltage Source Converter

6.      Transmission

7.      Distributed Power Flow Controller

8.      Unified Power Flow Controller.

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM

 SIMULATION RESULTS

CONCLUSION

This paper analyzed the DPFC performance during a failure of a single series converter unit. Series converters are protected by crowbar diodes to prevent over-voltage at the secondary side of the single-turn transformer. Therefore the failed series converter unit appears short-circuit to the transmission line and the voltage injection is unbalanced between phases. Because of this unbalance, the power network becomes asymmetric thereby resulting unsymmetrical current at the fundamental frequency. Also, the 3rd harmonic current that used to be zero sequence contains positive and negative components thereby leaking to rest of networks. A supplementary control scheme is proposed to add at the DPFC central control to improve the DPFC performance during series converter failure. Its principle is to monitor the zero and negative sequence components of the line current and control them to be zero. The control scheme has been simulated in Matlab, and it proved that the asymmetric caused by the failure can be totally compensated.

REFERENCES

[1] Z. Yuan, S. W. H. de Haan, and B. Ferreira, “A new facts component: Distributed power flow controller (dpfc),” in Power Electronics and Applications, 2007 European Conference on, 2007, pp. 1–4.

[2] L. Gyugyi, “Unified power-flow control concept for flexible ac transmission systems,” Generation, Transmission and Distribution [see also IEE Proceedings-Generation, Transmission and Distribution], IEE Proceedings C, vol. 139, no. 4, pp. 323–331, 1992.

[3] D. Divan and H. Johal, “Distributed facts - a new concept for realizing grid power flow control,” in Power Electronics Specialists Conference, 2005. PESC ’05. IEEE 36th, 2005, pp.8 14.

[4] M. Milosevic, G. Andersson, and S. Grabic, “Decoupling current control and maximum power point control in small power network with photovoltaic source,” in Power Systems Conference and Exposition, 2006. PSCE ’06. 2006 IEEE PES, 2006, pp. 1005–1011.

[5] J. Salaet, S. Alepuz, A. Gilabert, and J. Bordonau, “Comparison between two methods of dq transformation for single phase converters control. application to a 3-level boost rectifier,” in Power Electronics Specialists Conference, 2004. PESC 04. 2004 IEEE 35th Annual, vol. 1, 2004, pp. 214–220 Vol.1.

Simulation of MRAS-based Speed Sensorless Estimation of Induction Motor Drives using MATLAB/SIMULINK

ABSTRACT

Model Reference Adaptive System (MRAS) based techniques are one of the best methods to estimate the rotor speed due to its performance and straightforward stability approach. These techniques use two different models (the reference model and the adjustable model) which have made the speed estimation a reliable scheme especially when the motor parameters are poorly known or having large variations. The scheme uses the error vector from the comparison of both models as the feedback for speed estimation. Depending on the type of tuning signal driving the adaptation mechanism, there could be a number of schemes available such as rotor flux based MRAS, back e.m.f based MRAS, reactive power based MRAS and artificial neural network based MRAS. All these schemes have their own trends and tradeoffs. In this paper, the performance of the rotor flux based MRAS (RF-MRAS) and back e.m.f based MRAS (BEMF-MRAS) for estimating the rotor speed was studied. Both schemes use the stator equation and rotor equation as the reference model and the adjustable model respectively. The output error from both models is tuned using a PI controller yielding the estimated rotor speed. The dynamic response of the RF-MRAS and BEMF-MRAS sensorless speed estimation is examined in order to evaluate the performance of each scheme.

KEYWORDS

         1.      BEMF-MRAS

         2.      MRAS

         3.      Parameter Variations

         4.      RFMRAS

         5.      Sensorless Speed

         6.      Tracking Capability.

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM

Fig. 1. Basic configuration of MRAS-based speed sensorless estimation

scheme.

Fig. 2. Block diagram of RF-MRAS scheme

Fig. 3. Block diagram of BEMF-MRAS scheme.

   SIMULATION RESULTS

Fig. 4. RF-MRAS estimator's tracking performance at reference speed (a) 100rad/s, (b) 70rad/s and (c) 50rad/s (d) 30rad/s.

Fig. 5. Effect of incorrect setting of RS values to the RF-MRAS estimator's speed response. (a) Rs (b) Rsnew = 1.1 Rs (C) Rsnew = 1.5 Rs (d) Rsnew = 2 RS.

Fig. 6. BEMF-MRAS estimator's tracking performance at reference speed (a) 100rad/s, (b) 70rad/s and (c) 50rad/s (d) 30rad/s.

Fig. 7. Effect of incorrect setting of Rs values to the BEMF-MRAS estimator's speed response. (a) Rs (b) Rs,ew = 1.1 Rs (c) Rs,ew = 1.5 Rs (d) Rs,ew = 2 Rs.

CONCLUSION

Performance of RF-MRAS and BEMF-MRAS estimators based on the tracking capability and parameter sensitivity was presented. The result shows that the BEMFMRAS estimator is more superior to the RF-MRAS estimator at that particular defined range of reference speeds. This is prior to the elimination of pure integrators used in the RF-MRAS scheme. However, the BEMF-MRAS estimator is more difficult to design due to the non-linear effect of the adaptation gain constants. Therefore, as a whole, considering all the key criteria of comparison, it can be concluded that the BEMF-MRAS scheme embrace the requirement as a versatile estimator. It demonstrate good tracking capability and superb in insensitivity to parameter variations.

REFERENCES

[1] M. Ta-Cao, Y. Hori and T. Uchida, "MRAS-based speed sensorless control for induction motor drives using instantaneous reactive power", IEEE-IES Conference Record, pp. 1717-1422. 2001.

[2] S. Tamai, H. Sugimoto, M. Yano, "Speed-sensorless vector control of induction motor with model reference adaptive system", Conf. Record of the 1985 IEEE-IAS Annual Meeting, pp. 613-620, 1985.

[3] C. Shauder, "Adaptive speed identification for vector control of induction motor without rotational transducers", IEEE Trans. Ind. Application, Vol. 28, No. 5, pp. 1054-1061, Sept./Oct. 1992.

[4] Y.P. Landau, "Adaptive Control: The model reference approach", Marcel Dekker, New York, 1979.

[5] M.N. Marwali, A. Kehyani, "A comparative study of rotor flux based MRAS and back e.m.f based MRAS speed estimators for speed sensorless vector control of induction machine", IEEE-IAS Annual Meeting, New Orleans, Louisiana, pp. 160- 166, 1997.

Harmonic Mitigation using Fuzzy Logic Controller based Shunt Active Power Filter

ABSTRACT

Power quality problem is t he most sensitive problem in the power system. The objective of the project is to reduce one of the power quality issue called “harmonics” using compensation technique. Shunt Active Power Filter (SAPF) is used to eliminate harmonic current and also it compensates reactive power. In this project, both PI controller and Fuzzy Logic Controller based three-phase shunt active filter is employed for a three-phase four wire systems. The advantage of fuzzy control is that it provides linguistic values such as low, medium, high that are useful in case where the probability of the event to occur is needed. It does not require an accurate mathematical model of the system. A MATLAB/SIMULINK has been used to perform the simulation. Simulink model is developed for three phase four wire system under balanced source condition and three phase four wire system for unbalanced source condition. The performance of both balanced source and unbalanced source is done using Fuzzy Logic Controller and PI controller and their Simulink results is compared. Simulation results obtained shows that the performance of fuzzy controller is found to be better than PI controller.

KEYWORDS

       1.      Logic Control

       2.      Instantaneous p-q theory

       3.      Shunt Active Power Filter.

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM

 Fig 1: Block diagram of proposed system

 Fig 2: Structure of three phase four wire APF

SIMULATION RESULTS

 Fig 3: Simulation Waveform using pq with PI                 

 Fig 4: Simulation Waveform using pq with FLC          

 

 Fig 5: Harmonic Spectrum of Is using PI for balanced source

 Fig 6: Harmonic Spectrum of Is using FLC for balanced source

 Fig 7: Harmonic Spectrum of Is using PI for unbalanced source     

                 

                                                 Fig. 8 Harmonic Spectrum of Is using FLC for unbalanced source                                                                

CONCLUSION

The comparative analysis of a three phase four wire system using SAPF for reducingTHD of source current is done.The analysis uses the control of compensating current using PI controller and FLC is done for both balanced and unbalanced source condition. The harmonic spectrum shows the THD of both balanced and unbalanced source condition using PI and FLC. It is found that the harmonic reduction using FLC is found to produce better result than PI controller.

 REFERENCES

[1] Akagi. H. 2005. Active Harmonic Filters. Proceedings of the IEEE, Vol.93, 2128-2141.

[2] Hirofumi Akagi, Yoshihira Kanazawa and Akira Nabae. (1984), “Instantaneous Reactive Power Compensators Comprising Switching Devices without Energy Storage Components”, IEEE Transactions on Industrial Electronics, Vol. 20, pp-625-630.

[3] Fang Zheng Peng and Akagi.H, (1990), “A New Approach to harmonic Compensation in Power Systems –Acombined System of Shunt Passive and Series Active Filters”, IEEE Transactions on Industrial Applications, Vol. 26, pp-6-11.

[4] Karuppanan P and Kamala kanta Mahapatra (2011), “PI with Fuzzy Logic Controller based Active Power Line Condtioners” Asian Power Electronics, Vol. 5, pp-464-468.

[5] Kirawanich P and O,Connell R.M. (2004), “Fuzzy Logic Control of an Active Power Line Condioner”, (2004), IEEE Transactions on Power Electronics, Vol. 19, pp-1574-1585.

Implementation of Z-Source Based Dynamic Voltage Restorer for the Mitigation of Voltage Sag /Swell

 ABSTRACT

Modern industrial equipments are more sensitive to power quality problems such as voltage sag, voltage swells, interruption, harmonic, flickers and impulse transient. Failures due to such disturbances create high impact on production cost. So nowadays high quality power is became basic needs of highly automated industries This paper deals with modeling and simulation technique of a Dynamic Voltage Restore (DVR).The DVR is a dynamic solution for protection of critical loads from voltage sags/swells. The DVR restores constant load voltage and voltage wave form by injecting an appropriate voltage. Present novel structure improves power quality by compensating voltage sag and voltage swells. This control scheme provides superior performance compared to conventional control methods because it directly measurers the rms voltage at the load point without involving any transformation process. A new topology based on Z-source inverter is presented in order to enhance the voltage restoration property of dynamic voltage restorer. Z-source inverter would ensure a constant DC voltage across the DC-link during the process of voltage compensation. The modeling of Z-source based dynamic voltage restorer is carried out component wise and their performances are analyzed using MATLAB software.

KEYWORDS

      1.      Point Of Common Coupling (PCC)

      2.      Dynamic Voltage Restorer (DVR)

      3.      Active Power Filter (APF)

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM

 Fig.1. Schematic diagram of DVR.

Fig.2. Proposed Z source inverter topology.

SIMULATION RESULTS

 Fig.3. Simulation waveform of DVR based system when sag occurred. 

 Fig.4. Simulation waveform of DVR based system when swell occurred.

 Fig.5. Simulation waveform of DVR based system when sag/swell occurred.

Fig.6. Simulation waveform of DVR based system when connected to Z-source inverter.

CONCLUSION

Simulation of Z-source DVR for Power Quality Improvement is one of the techniques to improve the power quality by using Z-source DVR. This project has presented a discrete PWM control scheme for Dynamic Voltage Restorer to improve the system response and injection capability for the mitigation of voltage sag/swell. As opposed to fundamental frequency switching schemes already available in the MATLAB/SIMULINK, this PWM control scheme requires only rms value of the voltage.

REFERENCES

[1] M.H.J Bollen „Understanding Power Quality Problems : Voltage sag and Interruptions” New York IEEE Press ,1999.

[2] J.C. smith J.Lamoree ,P.Vinett,T.Duffy M.Klein “The impact of voltage sag Industrial plant load” International Conference Power quality end use application and perspective pp171-178.

[3] Akagi H,”New trends in active filters for power conditioning” IEEE Transaction Ind.Application,vol 32 pp 1312-1322 Nov/Dec 1996.

[4] Ghosh A and Ledwich G (2002) “Power quality Enhancement using Custom Power Devices”.Kluwr Academics publishers, United States.

[5] O. Anaya-Lara, E. Acha, “Modeling and Analysis of Custom Power Systems by PSCAD/EMTDC,” IEEE Trans., Power Delivery, PWDR vol-17 (1), pp. 266-272, 2002.