Smooth Shunt Control of a Fuzzy based Distributed Power Flow Controller to Improve Power Quality

ABSTRACT

Presently, the quality of power supplied is essential to many customers. Power quality (PQ) is a valued utility service where many customers are prepared to pay and get it. In the future, distribution system operators ought to decide, to provide their customers with distinct PQ ranges at different prices. Here, in this paper, a new control action to improve and maintain and enhance the power quality of an electrical power system is proposed in this paper. Fuzzy based distributed power flow controller (DPFC) is designed and put into action to compensate the voltage imbalances arising in a power system. This customized DPFC is an advanced FACTS device, which has its structure analogous to unified power flow controller (UPFC). DPFC comprises of both series and shunt converters, in which its three phase series converter is distributed over the transmission line as several single phase static converters ensuring high controllability and reliability at a low cost compared to an UPFC. A central controlling circuit is designed to supply reference signals to each of the individual controlling circuits of both series and shunt converters. This customized device is applied to a single machine infinite bus power system having nonlinear loads connected to it and is simulated in MATLAB/Simulink environment by using OPAL-RT 5600 Real-time digital Simulator. The results demonstrate the validation of proposed technique to enhance the power quality.

KEYWORDS:

1.      Power quality

2.      Voltage fluctuations

3.      Harmonic analysis

4.      Power harmonic filters

5.      Voltage control

6.      Load flow Voltage Sag and Swell

7.      Fuzzy Logic.

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Fig. 1. Basic configuration of DPFC

EXPECTED SIMULATION RESULTS:

Fig. 2. Voltage waveform during fault condition

Fig. 3. Current waveform during fault condition

Fig. 4. Simulated results for Voltage by employing DPFC controller

Fig. 5. Simulated results for Current by employing DPFC controller

Fig. 6. THD of load voltage without Controller

Fig. 7. FFT Analysis for PI Controller

Fig. 8. FFT Analysis for Fuzzy Controller

CONCLUSION

The work is presented to provide a solution for maintaining Power Quality at the distribution end, compensation of harmonics in grid voltage and in load currents. In order to consummate specified intentions in this paper a new concept for controlling power quality problems was proposed and implemented. By putting the customized device into action, results were analyzed for voltage dips and their mitigations for a three phase source with non-linear loads. The DPFC is modeled by positioning three control circuits designed independently. In this paper we also proposed and implemented the concept of fuzzy logic controller for having better controlling action, which will help in minimization/elimination of harmonics in the system. As compared to all other facts devices the Fuzzy based DPFC converter effectively controls all power quality problems and with this technique we can put THD to 3.04% proving the effectiveness of the proposed controller.

REFERENCES

[1]   D. Divan and H. Johal, “Distributed facts-A new concept for realizing grid power flow control,” in IEEE 36th Power Electron. Spec. Conf. (PESC), 2005, pp. 8–14.

[2]   K K. Sen, “Sssc-static synchronous series compensator: Theory, modeling, and application”,IEEE Trans. Power Del., vol. 13, no. 1, pp. 241–246, Jan. 1998.

[3]   L.Gyugyi, C.D. Schauder, S. L.Williams, T. R. Rietman, D. R. Torgerson, and A. Edris, “The unified power flow controller: A new approach to power transmission control”, IEEE Trans. Power Del., vol. 10, no. 2, pp. 1085– 1097, Apr. 1995.

[4]   M. D. Deepak, E. B. William, S. S. Robert, K. Bill, W. G. Randal, T. B. Dale, R. I. Michael, and S. G. Ian, “A distributed static series compensator system for realizing active power flow control on existing power lines”, IEEE Trans. Power Del., vol. 22, no. 1, pp. 642–649, Jan.2007

[5]    M. Mohaddes, A. M. Gole, and S. Elez, “Steady state frequency response of statcom”, IEEE Trans. Power Del., vol. 16, no. 1, pp. 18–23, Jan. 2001.

Power Quality Improvement in Transmission Systems Using DPFCPower Quality Improvement in Transmission Systems Using DPFC

ABSTRACT

The flexible ac-transmission system (FACTS) family called distributed power flow controller (DPFC). The DPFC is derived from the unified power flow controller (UPFC) with eliminated common dc link. The active power exchange between the shunt and series converters, which is through the common dc link in the UPFC, is now through the transmission lines at the third harmonic frequency. The DPFC is to use multiple small size single phase converters instead of large size three phase series converter in the UPFC. The large number of series converters provides redundancy, thereby increasing the system reliability. As the D-FACTS converters are single phase and floating with respect to the ground, there is no high voltage isolation required between the phases. The cost of the DPFC system is lower than the UPFC. The DPFC has the same control capability as the UPFC, which comprises the adjustment of the line impedance, the transmission angle, and the bus voltage. Due to the high control capability DPFC can also be used to improve the power quality and system stability, such as low frequency power oscillation damping, voltage sag restoration or balancing asymmetry.

KEYWORDS:

1.      AC–DC power conversion

2.      Load flow control

3.      Power electronics

4.      Power semiconductor devices

5.      Power system control

6.      Power-transmission control

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Figure 1.DPFC configuration

EXPECTED SIMULATION RESULTS:

Figure 2.Supply voltage during sag condition

Figure 3. Injected voltage during sag condition

Figure 4. Elimination of sag voltage

Figure 5. Supply voltage during swell

Figure 6. Injected voltage for swell

Figure 7. Elimination of swell voltage

CONCLUSION

The series converter of the DPFC employs the DFACTS concept, which uses multiple small single-phase converters instead of one large-size converter. It is proved that the shunt and series converters in the DPFC can exchange active power at the third-harmonic frequency, and the series converters are able to inject controllable active and reactive power at the fundamental frequency. The DPFC is also used to improving power quality problems such as sag and swell. The reliability of the DPFC is greatly increased because of the redundancy of the series converters. The total cost of the DPFC is also much lower than the UPFC, because no high-voltage isolation is required at the series converter part and the rating of the components of is low.

REFERENCES

[1]   D. Divan and H. Johal, “Distributed facts-A new concept for realizing grid power flow control,” in IEEE 36th Power Electron. Spec. Conf. (PESC), 2005, pp. 8–14.

[2]    K K. Sen, “Sssc-static synchronous series compensator: Theory, modeling, and application”,IEEE Trans. Power Del., vol. 13, no. 1, pp. 241–246, Jan. 1998.

[3]    L.Gyugyi, C.D. Schauder, S. L.Williams, T. R. Rietman, D. R. Torgerson, and A. Edris, “The unified power flow controller: A new approach to power transmission control”, IEEE Trans. Power Del., vol. 10, no. 2, pp. 1085– 1097, Apr. 1995.

[4]    M. D. Deepak, E. B. William, S. S. Robert, K. Bill, W. G. Randal, T. B. Dale, R. I. Michael, and S. G. Ian, “A distributed static series compensator system for realizing active power flow control on existing power lines”, IEEE Trans. Power Del., vol. 22, no. 1, pp. 642–649, Jan.2007.

[5]   M. Mohaddes, A. M. Gole, and S. Elez, “Steady state frequency response of statcom”, IEEE Trans. Power Del., vol. 16, no. 1, pp. 18–23, Jan. 2001.

Performance of Distributed Power Flow Controller on System Behavior under Unbalance Fault Condition

ABSTRACT

Recently, within the family of FACTS, the distributed power flow controller is an additional device. This paper highlights on voltage sag mitigation which is one of the burgeoning power quality issues. It deals with the working concept of distributed power flow controller for compensating unbalanced three phase line currents in the transmission system. The single phase series converters of DPFC are able to compensate active as well as reactive, negative and zero sequence unbalanced currents. In this paper the performance of the DPFC has been studied by considering line to ground fault near the load end. The MATLAB/SIMULINK results obtained shows an improved performance in voltage sag mitigation, unbalance compensation, remarkable reduction in load voltage harmonics and also enhanced power flow control.

KEYWORDS:

1.      DPFC

2.      Power flow control

3.      Reduction of load voltage harmonics

4.      Reliability improvement

5.      Voltage sag mitigation

6.      Unbalance fault condition.

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Fig. 1. Basic DPFC structure.

EXPECTED SIMULATION RESULTS:

Fig. 2. Load voltage sag waveform during unbalance fault.

Fig. 3. Mitigation of load voltage sag wave form during unbalance fault with DPFC.

Fig. 4. Load voltage. (a) Signal selected for calculating THD without DPFC. (b) THD without DPFC.

(b)

Fig. 5. Load voltage. (a) Signal selected for calculating THD with DPFC. (b) THD with DPFC.

.

Fig. 6. Capacitor dc voltage in dc side of shunt converter within DPFC.

CONCLUSION

This paper introduces the unbalance compensation and the voltage sag mitigation during unbalance fault condition by utilizing a recent additional FACTS device which is distributed power flow controller (DPFC) adopting sequence analysis technique. The DPFC is designed by employing three control loops. The simulated system has two machine systems, in presence and absence of the DPFC in the system. To examine the capability of the DPFC, an unsymmetrical L-G fault is taken into account near the load end side. In this paper simulation done verifies that the adopted control is able to give unbalance compensation and mitigation of voltage sag.

REFERENCES

[1]   N. G. Hingorani and L. Gyugyi, Understanding FACTS : Concepts And Technology of Flexible AC Transmission Systems. New York: IEEE Press, 2000.

[2]   L. Gyugyi, C. D. Schauder, S. L. Williams, T. R. Rietman, D. R. Torgerson, and A. Edris, “The Unified Power Flow Controller: A New Approach to Power Transmission Control,” IEEE Trans. Power Del., vol. 10, no. 2, pp. 1085–1097, April 1995.

[3]    Y. H. Song, and A. Johns, “Flexible AC Transmission Systems (FACTS),” Institution of Electrical Engineers (IEE Power and Energy Series), London, U.K:, vol. 30, 1999.

[4]    K. Ramya and C. Christober Asir Rajan, “Analysis And Regulation of System Parameters Using DPFC,” IEEE International Conference on Advances in Engineering, Science And Management (ICAESM), March 2012, pp. 505-509.

[5]   M. D. Deepak, E. B. William, S. S. Robert, K. Bill, W. G. Randal, T. B. Dale, R. I. Michael, and S. G. Ian, “A Distributed Static Series Compensator System For Realizing Active Power Flow Control on Existing Power Lines,” IEEE Trans. Power Del., vol. 22, pp. 642-649, Jan. 2007.

MITIGATION OF VOLTAGE SAG FOR POWER QUALITY IMPROVEMENT USING DPFC SYSTEM

ABSTRACT

A new control scheme to improve and maintain the power quality of an electrical power system by design of distributed power flow controller. Generally, In case of modern power utilities have problems like challenges in growth of electricity in case of non-linear loads in grid connected systems. In this paper, we introduced a new FACTS method i.e. distributed power flow controller which is similar to other series-shunt controller types. This DPFC method is also used like UPFC to mitigate voltage sag and swell as a power quality issue. In DPFC, we eliminate the common dc link capacitor and instead of single three phase series converter it has three individual single phase converters. In this paper the control circuit is designed by using series referral voltages, branch currents. The evaluated values are obtained by using MATLAB/SIMULINK.

KEYWORDS:

1.      DPFC

2.      Voltage Sag and Swell

3.      Power Quality

SOFTWARE: MATLAB/SIMULINK

 BLOCK DIAGRAM:

Fig 1: Basic Configuration of DPFC

EXPECTED SIMULATION RESULTS:

Fig 2: Simulation results for voltage sag condition

Fig 3: Simulation results for mitigation of Voltage sag with DPFC system

Fig 4: Simulation results for current swell condition

                                                                                          

Fig 5: Simulation results for mitigation of current swell with DPFC system

Fig 6: simulation results for active and reactive powers

CONCLUSION

In this paper we implemented a new concept for controlling power quality problems by Distributed Power Flow Controller device. The proposed concept of the DPFC approach is mathematically formulated and analyzed for voltage dips and their mitigations for a three phase source with linear load. The experimental results of DPFC shows the effectiveness of DPFC in power quality enhancement as compared to all other FACTS devices.

REFERENCES

[1]   J. Faiz, G. H. Shahgholian, and M. Torabian, “Design and simulation of UPFC for enhancement of power quality in transmission lines,” IEEE International Conference on Power System Technology, vol. 24, no. 4, 2010.

[2]   A. E. Emanuel and J. A. McNeill, “Electric power quality,” Annu. Rev. Energy Environ, 1997.

[3]    I. N. R. Patne and K. L. Thakre “Factor affecting characteristics of voltage sag due to fault in the power system,” Serbian Journal of Electrical engineering. vol. 5, no.1, 2008.

[4]   B. Singh, K. Al-Haddad, and A. Chandra, “A review of active filters for power quality improvement,” IEEE Trans. Ind. Electron. vol. 46, no. 5, pp. 960–971, 1999.

[5]    M. A. Hannan and A. Mohamed, member IEEE, “PSCAD/EMTDC simulation of unified series-shunt compensator for power quality improvement,” IEEE Transactions on Power Delivery, vol. 20, no. 2, 2005.

Integrating Flywheel Energy Storage System to Wind Farms-Fed HVDC System via a Solid State Transformer

ABSTRACT

As the power of wind farms (WFs) considerably proliferates in many areas worldwide, energy storage systems will be required to dynamically compensate the wind energy intermittency and increase power system stability. In this paper, a backup power conditioning strategy for wind energy-fed voltage source converter HVDC transmission systems is presented. An induction machine based flywheel energy storage systems (FESS) is integrated to the HVDC system via a solid state transformer (SST). The FESS is connected in parallel with the dc-link of the grid side converter; therefore, the excess wind energy can be stored in the flywheel and then restored during the energy shortage periods. The proposed system aims to compensate the power fluctuations caused by the intermittent nature of wind energy, levels the power-fed to the grid, and improves the quality of delivered power. The proposed system including FESS with an interfacing SST is modeled, simulated, and analyzed in MATLAB/SIMULINK environment. The results verify the effectiveness of the proposed system.

KEYWORDS:

1.       HVDC

2.      Wind generation

3.      Storage system

4.      Smart grid

5.      Flywheel.

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Figure 1. The proposed system

 EXPECTED SIMULATION RESULTS:

Figure 2. Simulation results of power smoothing operation in pu (a) grid power, wind power, and flywheel power, (b) flywheel speed, (c) phase shift between two H-bridges of DAB, (d) HV dc link, (e) LV dc link.

Figure 3. Simulation results of HFT waveforms, in pu, employing soft switching using phase shift technique (a) positive power flow (from H2 to H1), (a)negative power flow (from H1 to H2).

Figure 4. Simulation results of power leveling operation in pu.

CONCLUSION

In this paper, a new strategy of improving the integration of large scale wind farms into HVDC transmission system using SST based FESS has been proposed to compensate for the wind power oscillations and to enhance the power profile at grid side. In the proposed technique a low speed induction machine based flywheel energy storage system is connected in parallel with the DC link of the grid side converter. Therefore, the excess wind power is stored in FESS and restored in case of wind power shortage and/or power demand increase preserving the grid power profile at its required value. The simulation results have demonstrated that the FESS compensates for power fluctuations caused by wind nature during different load conditions and exhibits good system performance with a relatively fast response and high dynamics.

  

REFERENCES

[1]   F. Schettler, and H. Huang, N. Christl, "HVDC transmission systems using voltage sourced converters design and applications," Power Engineering Society Summer Meeting, 2000. IEEE, vol.2, pp.715-720 vol. 2, 2000.

[2]   W. Long and S. Nilsson, "HVDC transmission: yesterday and today," Power and Energy Magazine, IEEE, vol.5, no.2, pp.22-31, March-April 2007.

[3]   M.P. Bahrman and B.K. Johnson, "The ABCs of HVDC transmission technologies," Power and Energy Magazine, IEEE, vol.5, no.2, pp.32- 44, March-April 2007.

[4]   N.M. Kirby, Lie Xu; M. Luckett, and W. Siepmann, "HVDC transmission for large offshore wind farms," Power Engineering Journal, vol.16, no.3, pp.135-141, June 2002.

[5]   Jiancheng Zhang, "Research on Flywheel Energy Storage System Using in Power Network," International Conference on PowerElectronics and Drives Systems, 2005. PEDS 2005, vol.2, no., pp. 1344- 1347, 28-01 Nov.2005.