Damping Power System Oscillations Using a Hybrid Series Capacitive Compensation Scheme

Damping Power System Oscillations Using a Hybrid Series Capacitive Compensation Scheme

ABSTRACT:

The recently proposed phase imbalanced series capacitive compensation concept has been shown to be effective in enhancing power system dynamics as it has the potential of damping power swing as well as sub synchronous resonance oscillations. In this paper, the effectiveness of a “hybrid” series capacitive compensation scheme in damping power system oscillations is evaluated. A hybrid scheme is a series capacitive compensation scheme, where two phases are compensated by fixed series capacitor (C) and the third phase is compensated by a TCSC in series with a fixed capacitor (Cc). The effectiveness of the scheme in damping power system oscillations for various network conditions, namely different system faults and tie-line power flows is evaluated using the EMTP-RV time simulation program.

KEYWORDS

1.      FACTS Controllers

2.       phase imbalance

3.       series compensation

4.       thyristor controlled series capacitor

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Fig. 1. A schematic diagram of the hybrid series compensation scheme.

                                     

Fig. 2. Test benchmark.

EXPECTED SIMULATION RESULTS:

                   

Fig. 3. Generator load angles, measured with respect to generator 1 load angle, during and after clearing a three-phase fault at bus 4 (Load Profile A).

Fig. 4. Generator load angles, measured with respect to generator 1 load angle, during and after clearing a three-phase fault at bus 4 (Load Profile B).

             

Fig. 5. Structure of a dual-channel power oscillations damping controller.

Fig. 6. Generator load angles, measured with respect to generator 1 load angle, during and after clearing a three-phase fault at bus 4 (Load Profile B, dual-channel controller).

Fig. 7. Phase voltages, VX-Y across the hybrid single-phase-TCSC scheme on L1 during and after clearing a three-phase fault at bus 4 (Load Profile B, dual channel supplemental controllers, Pair 2).

CONCLUSION:

The paper presents the application of a new hybrid series capacitive compensation scheme in damping power system oscillations. The effectiveness of the presented scheme in damping these oscillations is demonstrated through several digital computer simulations of case studies on a test

benchmark. The presented hybrid series capacitive compensation scheme is feasible, technically sound, and has an industrial application potential.

REFERENCES:

[1] Narain G. Hingorani and Laszlo Gyugyi, “Understanding FACTS, Concepts and Technology of Flexible AC Transmission Systems,” IEEE Press, 2000.

[2] M. Klein, G.J. Rogers and P. Kundur, “A Fundamental Study of Inter- Area Oscillations in Power Systems,” IEEE Transactions on Power Systems, Vol. 6, No. 3, 1991, pp. 914-921. Fig. 9. Phase voltages, VX-Y across the hybrid single-phase-TCSC scheme on L1 during and after clearing a three-phase fault at bus 4 (Load Profile B, dual channel supplemental controllers, Pair 2).

[3] E.V. Larsen, J.J. Sanchez-Gasca and J.H. Chow, “Concepts for Design of FACTS Controllers to Damp Power Swings,” IEEE Transactions on Power Systems, Vol. 10, No. 2, May 1995, pp. 948-956.

[4] B. Chaudhuri, B. Pal, A. C. Zolotas, I. M. Jaimoukha, and T. C. Green, “Mixed-sensitivity Approach to H Control of Power System Oscillations Employing Multiple FACTS Devices,” IEEE Transactions on Power System, Vol. 18, No. 3, August 2003, pp. 1149–1156.

[5] B. Chaudhuri and B. Pal, “Robust Damping of Multiple Swing Modes Employing Global Stabilizing Signals with a TCSC,” IEEE Transactions on Power System, Vol. 19, No. 1, February 2004, pp. 499–506.

Analysis and Simulation of a D-STATCOM for Voltage Quality Improvement

Analysis and Simulation of a D-STATCOM for Voltage Quality Improvement

ABSTRACT:

Voltage flicker is a major power quality concern for both power companies and customers. This paper discusses the dynamic performance of a (D-STATCOM) with ESS for mitigation of voltage flicker. The (D-STATCOM) is intended to replace the widely used static var compensator (SVC). A Distribution Static Synchronous Compensator (D-STATCOM) is used to regulate voltage on a 25-kV distribution network. The (D-STATCOM) protects the utility transmission or distribution system from voltage sag and /or flicker caused by rapidly varying reactive current demand. The (D-STATCOM) regulates bus voltage by absorbing or generating reactive power. This voltage is provided by a voltage sourced PWM inverter. The simulation is carried out using MATLAB/SIMULINK and the simulation results illustrate the performance of (D-STATCOM) in mitigation of voltage flicker.

KEYWORDS 

1.      Power Quality

2.       Energy Storage System (ESS)

3.       D-STATCOM

4.       Voltage Flicker

5.      Synchronous Reference Frame (SRF)

 SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Fig. 1: D-STATCOM controller with d-q theory.

Fig. 2: Detailed Versus Average Model of D-STATCOM.

EXPECTED SIMULATION RESULTS:

Fig. 3: Output voltage of D-STATCOM.

Fig. 4: Output voltage of voltage source inverter.

Fig. 5: Output P & Q of D-STATCOM.

Fig. 6: Output current of D-STATCOM.

Fig. 7: I_q and I_qref of D-STATCOM.

Fig. 8: P and Q of terminal B₃.

Fig. 9: Terminal voltages B₁ and B₃.

Fig. 10: Changes of DC voltage.

CONCLUSION:

In this paper, D-STATCOM controller is derived by using synchronous reference theory. The model is simulated in MATLAB/SIMULINK platform and D-STATCOM controller’s performance is evaluated using dq theory for voltage flicker mitigation. The controller is proven to be effective for flicker mitigation with improved dynamic response of the system and compensating reactive currents will help the mitigation of voltage flicker.

REFERENCES:

o   Esfandiari, A. and M. Parniani, 2004. “Electric arc furnace power quality improvement using shunt active filter and series inductor,” IEEE Region10 Conference, 4: 105-108.

o   Hingorani, N.G., 1995. “Introducing custom power,” IEEE Spectrum, 1(6): 41-48.

o   Hingorani, N.G. and L. Gyugyi, 2000. “Understanding FACTS: Concepts and Technology of Flexible AC Transmission Systems,” New York: IEEE Press, 135-143.

o   IEEE PES working group FACTS Applications, 1996. IEEE press, (96).

o   Marshall, M.W., 1997. “Using series capacitors to mitigate voltage flicker problems,” 41st Annual Rural Electric Power Conference, pp: B3-1-5

Direct torque control of squirrel cage induction motor for optimum current ripple using three-level inverter

Direct torque control of squirrel cage induction motor for optimum current ripple using three-level inverter

ABSTRACT:

Three-level neutral point clamped (NPC) inverters have been widely used in medium voltage applications. In this study, direct torque control strategy for sensorless squirrel-cage induction motor (SQIM) using NPC three-level inverter is presented. The proposed control strategy optimises the current ripple in steady state and also gives a high dynamic performance of torque in transient state. The advantage of having low dv/dt for three-level inverter output voltage is retained. The control strategy is verified on a 7.5 hp SQIM drive with three-level insulated-gate bipolar transistor (IGBT) inverter. Experimental results validate the steady state and the dynamic performance of the proposed control strategy.

 SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

 Figure 1: Three-level diode clamped inverter

                                       

Figure 2: Block diagram of the controller

EXPECTED SIMULATION RESULTS:

                   

Figure 3: Trajectory of the stator flux in stationary α –β Plane

                 

Figure 4: Experimentally estimated rotor flux (Ѱ_rsα, Ѱ_rsβ) at a frequency of 5 Hz

                

Figure 5: Three-level motor line voltage

         

 Figure 6: Torque reference and actual torque ripple

            

Figure 7: Steady state speed and line current waveforms (a) Experimental waveform of speed (ω_e) and line current (i_s) at steady state (b) Zoomed waveform of line current showing the ripples

Figure 8: Experimental waveforms of speed (ω_e) and line current (i_s) at steady state at 14 Hz

                 

Figure 9: Torque reference (m^*_d) and actual torque (m_d) during transient

CONCLUSION:

This paper has introduced a direct torque and flux control for SQIM using neutral point clamped three-level inverter. The operation of the drive is divided into two regions – low frequency operation and high-frequency operation. Separate switching strategies are proposed for these two regions of operation. The proposed strategy optimises the switching to have minimum dv/dt in the motor line voltages. It also optimises the current ripple in steady state and gives a fast torque response during transient. There is an effective reduction in the dv/dt applied to the motor terminals. This in turn reduces the bearing current and shaft voltages [14, 15] of the motor thereby increasing the life of the motor. Experimental results using SQIM and three-level inverter validate the proposed strategy.

REFERENCES:

[1] NABAE A., TAKAHASHI I., AKAGI H.: ‘A new neutral point clamped inverter’, IEEE Trans. Ind. Appl., 1981, IA-17, (5), pp. 518–523

[2] LAI J.-S., PENG F.Z.: ‘Multilevel converters – a new breed of power converters’, IEEE Trans. Ind. Appl., 1996, 32, (3), pp. 509–517

[3] MCGRATH B.P., HOLMES D.G., LIPO T.A.: ‘Optimized space vector switching sequences for multilevel inverters’, IEEE Trans. Power Electron., 2003, 18, (6), pp. 1293–1301

[4] BUJA G.S., KAZMIERKOWSKI M.P.: ‘Direct torque control of PWM inverter-fed AC motors – a survey’, IEEE Trans. Power Electron., 2004, 51, (4), pp. 744–757

[5] CASADEI D., SERRA G., TANI A., ZARRI L.: ‘Assessment of direct torque control for induction motor drives’, Bull. Pol. Acad. Sci., Techn. Sci., 2006, 54, (3), pp. 237–254

Wind driven Induction Generator with Vienna Rectifier and PV for Hybrid Isolated Generations

Wind driven Induction Generator with Vienna Rectifier and PV for Hybrid Isolated Generations

ABSTRACT:

 Hybrid PV-wind generation shows higher availability as compared to PV or wind alone. For rural electrifications, researches are focused on hybrid power system which provides sustainable power. The variable voltage and frequency of the self excited induction generator (SEIG) is rectified through Vienna rectifier (three switches) to the required D.C voltage level and fed to common D.C bus. The variable output voltage of PV module is controlled by DC/DC converter using proposed fuzzy logic controller and fed to common D.C bus. The DC bus collects the total power from the wind and photovoltaic system and used to charge the battery as well as to supply the A.C loads through inverter. A dynamic mathematical model and MATLAB simulations for the entire scheme is presented. Results from the simulations and experimental tests bring out the suitability of the proposed hybrid scheme in remote areas.

KEYWORDS:

1. DC-DC converter

2. Fuzzy logic

3. SEIG

4. PV array

5. Vienna Rectifier

6. Wind energy.

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Figure 1. Schematic diagram of solar-wind hybrid scheme

EXPECTED SIMULATION RESULTS:

Figure 2: Simulated and Experimental waveforms

                                                                       Figure 3(a) Conventional Six Pulse Converter

  Figure 3(b) vienna Rectifier

                            Figure 3(c) per phase input voltage and current waveforms of  vienna Rectifier

             

CONCLUSION:

A hybrid scheme for isolated applications, employing solar and wind driven induction generator with Vienna rectifier, is proposed with fuzzy logic controller, with optimized rule-base. Hence it is very suitable for the rural electrification in remote areas where grid cannot be accessed. The photovoltaic characteristics and capacitance requirements of SEIG are discussed. Using the mathematical model described the dynamic characteristics of the hybrid scheme to maintain almost the desired load voltage is also discussed. The simulated results are focused on both the steady-state and dynamic behavior of the hybrid scheme which demonstrates the validity of the proposed model. The simulation and the experimental result of hybrid scheme shows the operation of the controller for constant load voltage had inherently resulted in balancing of power between the two sources while supplying constant power to the load.

REFERENCES:

[1] Y.Jaganmohan Reddy, Y.V. Pavan kumar, K. padma raju, and Anil kumar ramesh, “ Retrofitted Hybrid Power System Design With Renewable Energy Sources for Buildings”, IEEE Transaction on Smart Grid , Vol.3, no.4, pp. 2174-2186, Dec 2012.

[2] S.Meenakshi, K.Rajambal, C.Chellamuthu, and S.Elangovan, “Intelligent Controller for Stand-Alone Hybrid Generation System”, Power India Conference IEEE, pp 8-15, 2006.

[3] Ashraf A.Ahmed, Li Ran, Jim Bumby, “Simulation and control of a Hybrid PV-Wind System”, Power Electronics Machines & Drives, PEMD 4th IET conference, pp 421-425, 2008.

[4] Meenakshmisundaram Arutchelvi, Samuel Arul Daniel, “Grid Connected Hybrid Dispersed Power Generators Based on PV Array And Wind Driven Induction Generator”, Journal of Electrical Engineering, Vol., 60, pp 313-320, 2009.

[5] Hao Chen, Dionysios C. Aliprantis , “ Analysis of Squirrel-cage Induction Generators with Vienna Rectifier for Wind Energy Conversion System”, IEEE Transactions on Energy Conversion, Vol.26, no.3, 2011.